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Virparia, Arvindkumar M., 2013, " Studies on Metal Chelates of Some Schiff's
Bases ", thesis PhD, Saurashtra University
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STUDIES ON METAL CHELATESOF
SOME SCHIFF’S BASES
A THESIS SUBMITTED TO THE
SAURASHTRA UNIVERSITY FOR THE DEGREE OF
Doctor of Philosophy
IN
THE FACULTY OF SCIENCE (CHEMISTRY)
BY
Mr. ARVINDKUMAR M. VIRPARIA
UNDER THE GUIDANCE
OF
Dr. P. K. Patel
CHEMISTRY DEPARTMENT MAHARAJA SHREE MAHENDRASINHJI SCIENCECOLLEGE,
MORBI- 363 642 GUJARAT (INDIA)
2013
The Sarvodaya Education Society’s
Maharaja Shree Mahendrasinhji Science College Nazar Baugh, Bhadiyad Road, Morbi-363 642.
Dr. P. K. Patel Residence: M.Sc., Ph.D. ‘Aum’ Principal, 4-Avani Park Society, Maharaja Shree Opp. P.G. Clock, Mahendrasinhji Science College, Shanala Road, Morbi - 363 642 Morbi - 363 641 Phone(O): - 02822-240601 Phone(R)02822224755
Statement under O. Ph. D. 7 of Saurashtra University
The work included in the thesis is my own work under the supervision of Dr. P. K. Patel and leads to some contribution in chemistry subsidized by a number of references.
Dt.: - 01 - 2013 (Arvindkumar M. Virparia)
Place: Morbi
This is to certify that the present work submitted for the Ph.D. Degree of Saurashtra University by Arvindkumar M. Virparia is his own work and leads to advancement in the knowledge of chemistry. The thesis has been prepared under my supervision.
Date : - 01 - 2013 Dr. P. K. Patel
Place : Morbi Principal` MaharajaShree
Mahendrasinhji Science College Morbi - 363 642
Dedicated
To my
Beloved family
And
My
“Guruji”
ACKNOWLEDGEMENTS
“Shree Ganeshay Namah”
It is a moment of gratification and pride to look back with a sense of contentment at the long traveled path, to be able to recapture some of the fine moments, to be think of the infinite number of people, some who were with me from the beginning, some who joined me at different stages during this journey, whose kindness, love and blessings has brought me to this day. I wish to thank each of them from the bottom of my heart.
First and foremost, I wish to pay my homage and devote my emotions to “Lord Ganesha”, “The Wonderful Chemist” of this lovely world without whose blessings this task would not have been accomplished. I bow my head in utter humility and complete dedication.
I bow my head with absolute respect and pleasantly convey my heartily thankfulness to my co-traveler and my research guide, most respectable Dr. Praful K. Patel, who continued to support my aspiration with lots of love and encouragement. I consider myself privileged to work under his generous guidance, because I got the newer creative dimensions and positive attitude in my thinking and analyzing capacity, which helped me to make things simple but programmatic. I am always indebted to him. He constantly encouraged me to remain focused on achieving my goals. His observations and comments helped me to establish the overall direction of the research and also move forward expeditiously with investigation in depth.
I would like to extend my deepest sense of indebtness to shri Chhabilbhai Sanghavi, Hon. President, and all members of SES for their support, encouragement and facilities provided by them to use Maharaja Shre Mahendrasinhji Science College Laboratory.
Above all, I bow my head with utter respect to my beloved parents late Vajiben and Mohanbhai for this accomplishment of my life. Also I can never forget my brithers Valjibhai, Govindbhai and Manshukhbhai.
I do not hence any word to express my gratefulness to my wife Gita and children Tanmay and Utsav who stood beside me during my work. Their love and smiling face boosted up me.
I wish to Special thanks to Dr. J. M. Parmar, Dr. D. R. Bhadja, Dr. B. M. Bheshdadia, Dr. M. V. Parsania, and Dr. B. M. Sharma, DR. V.A Modhvadiya, Dr.K.M.Rajkotia Dr. H. C. Mandavia, Mr. H. O. Jethva, Dr. J. G. Raiyani, Mr. N. H. Manani, Dr. R. R. Ranjan, Dr. N. S. Panchal, Mr. S. S. Babariya, Mr. V. M. Katba, Mr. R.D. Kalaria, Mr. D. M. Sanghani, Mr. B. M. Patel, and for them constant guidance and moral support whenever I needed during the course of my research work.
I would like to express my deep sense of gratitude and lots of love towards my dearest friends Dr. A. J. Rojivadiya, Dr. D. O. Odedara, Mr. H.H. Ranavaia, Dr. A. H. Bapodara, Dr. J. J. Upadhya, and Dr. J. J. Modha, Mr. L. M. Vagela, Dr. D. M. Purohit Dr. D. S. Kundariya,
I also like to thanks to Mahendra, Pravin, Haresh, Dilip, Dharmendra,Dilip kalaria, dinesh, Bharat, Rakesh, Govind Dr.kantaria, Prakashbhai, Haresh Charola, Sureshbhai Marvania, I am really very much thankful to God for giving me such nice friends.
I also owe to, Dr. P. H. Parsania, Professor and Head Department of Chemistry, Saurashtra University, Rajkot. DR. D. K. Raval, Dr. N. J. Parmar
I would also like to thank teaching and non-teaching staff members of M. M. Science College, Morbi for their kind help and moral support during course of my research work.
I wish to Special thanks to My Adhytmic Guruji H.H. Shri Shivkrupand Swamiji and Pujya Guruma
I gratefully acknowledge the most willing help and co-operation shown by CDRI Lucknow and SAIF Punjab University, Chandigarh, Chemistry Department Saurashtra University Rajkot for spectral studies and Chemistry Department S. P. University V. V. Nagar for providing Magnetic Analysis. And Sicart, V.V. Nagar for providing thermal analysis
Finally, I express my grateful acknowledgment to Department of Chemistry, M. M. Science College, Morbi, for providing me the excellent laboratory facilities and kind furtherance for accomplishing this work
Mr.Arvindkumar M.Virparia
CONTENTS
Page. No.
SYNOPSIS 1 CHAPTER - 1
Introduction and literature survey on Schiff bases and their
Metal Chelates. 6
Reference 23
CHAPTER - 2
Experimental: Synthesis of Schiff base and their Metal Chelates. 29
Reference 40
CHAPTER - 3
Analytical and spectral study of Schiff base and their Metal Chelates. 41
Reference 94
CHAPTER - 4
Thermal Analysis of Metal Chelates. 95
Reference 107
CHAPTER - 5
Magnetic Measurement. 109
Reference 133
CHAPTER - 6
A comprehensive summary of work 135
Reference 152
Studies on metal chelates……………….. Synopsis
1
STUDIES ON METAL CHELATES OF SOME SCHIFF’S BASES
Hugo Schiff described the condensation between an aldehyde and an
amine leading to a Schiff base in 1864 1. Schiff base ligands are able to
coordinate metals through imine nitrogen and another group, usually linked to
the aldehyde. The coordination chemistry of Schiff bases has attracted the
attention of several investigators 2-5. Nitrogen, oxygen and /or sulphur-
containing ligands and there metal complex have been found to possess
significant biological and pharmacological activities and are used as catalyst,
fungicides, bactericides, tuberculostatic and anticarcinogenic agents 6. Schiff
bases have been used as corrosion inhibitors 7.
The coordination complexes have found extensive application in
various fields of human interest. These including extraction, dyeing, water
softening etc. These metal complexes containing ligands play an important
role as catalyst in many bioinorganic systems. Many chelating ligands find
extensive applications as reagent and masking agents in various titrimetric,
spectrophotometric, chromatographic methods. Thus complexation studies of
Schiff bases are particular attention by coordination chemists.
1. Schiff H. Ann. Suppl. 1864; 3; 343.
2. Patel MN, Patel KM, Patel NH, Patel KN. Synth. React. Inorg.Met.-
Org.Chem.2000;30:1965
3. Cukurovali A, Yilmaz I, Ozmen H, Ahmedzade M. Trans. Met.
Chem.2002; 27: 171
4. Khan MMT, Halligudi SB, Shukla S, Shark J. Jou. Mol. Catal. 1990; 57:
301.
5. Bhattacharya PK. Chem. Sci. 1990; 102: 247.
6. Singh MS, Singh AK, Tawada K. Synth. React. Inorg.Met.-
Org.Chem.2002; 32: 639.
7. Achouri M, Kertit S, Salem M, Essassi EM, and Tellal M; Bull. Of
Electrochem., 1998; 14: 462.
Studies on metal chelates……………….. Synopsis
2
The work presented in the thesis with title "STUDIES ON
METAL CHELATES OF SOME SCHIFF’S BASES” has been
described into six chapters:
CHAPTER- 1 Introduction and literature survey on Schiff bases
and their Metal Chelates.
CHAPTER- 2 Experimental: Synthesis of Schiff base and their
Metal Chelates.
CHAPTER- 3 Analytical and spectral study of Schiff base and
their Metal Chelates.
CHAPTER- 4 Thermal Analysis of Metal Chelates.
CHAPTER- 5 Magnetic Measurements.
CHAPTER- 6 A comprehensive summary of work
CHAPTER- 1 INTRODUCTION
This chapter of the thesis describes the general introduction, Schiff
base, Importance of Schiff bases, uses of coordination compounds, Literature
survey, Present work, and Reference.
CHAPTER- 2 EXPERIMENTAL
2.1 Syntheses of Schiff bases
This section is deal with synthesis of amine and their Schiff bases.
• Synthesis of Amine 1, 1’ bis (4-aminophenyle) cyclohexane [ A ]
Compound [A] was prepared by condensation of cyclohexanone and
excess aniline as follow 8-9. To a solution of cyclohexanone 0.101 mole and
aniline 0.267 mol in 25 ml of 35% HCl at 110ºC for 17-18 h.(yield 51.48 % of
light – yellow crystal M.P.110-112 M.F.C18H22N2, F.W.=266GM)
8. Mi Hie YI, Wenxi Huang, Moon Young Jin, and Kil–Yeong Choi,
Macromolecules,1997, 30 (19),5606-5611.
9. Myska,J. Chem. Abstr.1964,61,14558.
Studies on metal chelates……………….. Synopsis
3
Synthesis of Schiff base:
• 6,6’-(4,4’-(cyclohexane-1,1-diyl) bis(4,1-phenylene)) bis (azan-1-yl-1-
ylidene) bis (methan-1-yl-1-ylidene) bis (2-methoxy phenol) (L1-o-v-A)
and
• 2,2’-(4,4’-(cyclohexane-1,1-diyl)bis(4,1-phenylene))bis(azan-1-yl-1-
ylidene)bis(methan-1-yl-1-ylidene) diphenol (L2- sal-A)
• 1,1’-(4,4’-(cyclohexane-1,1-diyl)bis(4,1-phenylene))bis(azan-1-yl-1-
ylidene)bis(methan-1-yl-1-ylidene)dinaphthalen-2-ol(L3-O-H-Naph.-A)
Synthesis of Schiff base by condensation of 50ml solution of 2-
hydroxyl -3- methoxy benzaldehyde (7.6gm , 50mmol.) in hot ethanol and
50ml solution of 1, 1’ bis ( 4-aminophenyle) cyclohexane (6.65gm,25mmol) in
hot ethanol. using glacial acetic acid as a catalyst and reaction mixture was
reflux on water bath for 4-5 h. a solid mass was separated out on cooling, it
was suction filtered, washed with sodium bisulfite solution, water and finally
with ethanol. Subsequently dried over anhydrous CaCl2 in desiccators. The
Schiff base are recrystallized from chloroform and purity was checked by TLC
in appropriate solvent system at room temperature The Same procedure was
adopted for the other ligands
N N CH
HO
O
HC
OH
O
Studies on metal chelates……………….. Synopsis
4
2.2 Synthesis of Metal Chelates of Schiff base:
The metal chelates of the Schiff base were synthesized by mixing
(1:1mol) a chloroform-ethanolic (1:1, 30ml) of Schiff base, L1-O-V-A or L2-
Sal- A or L3-O-H-Naph.-A with an ethanolic solution (30 ml ) of metal solt or
metal acetate. The resulting mixture was refluxed with stirring on a magnetic
stirrer equipped with heater for 5-6 h. on cooling, the colored chelates
precipitated out, which was filtered by suction, washed several times with
ethanol and finally with ether, and dried over anhydrous CaCl2 .The metal ions
selected were Cu (II), Ni (II), Co (II) & Zn (II) proposed structure of metal
Chelates will be as following
N N CH
O
O
CH3
HC
O
O
CH3
M+2
CHAPTER – 3 Analytical and spectral study of Schiff bases and their
Metal chelates.
This chapter of thesis deals with the Elemental analysis, Conductivity
Measurements, Solubility, spectral characterization of Schiff base and their
metal chelates it gives functional groups ,quantitative structure of the
Compound.
Studies on metal chelates……………….. Synopsis
5
CHAPTER – 4 Thermal Analysis of Metal Chelates:
This Chapter deals with determinations of change in chemical or
physical properties of material as a function of temperature in a controlled
atmosphere. Thermo gravimetric analysis (TGA), measured weight changed
in a material as a function of temperature. The TGA data provide important
experimental evidence in determining the number of water molecules present
in the metal chelates. It is best tool for understanding decomposition
mechanism etc.
CHAPTER – 5 Magnetic Measurements:
This chapter deal with Magnetic susceptibility Measurements on the
vibration sample magnetometer (VSM), model 7304, Lake Shore Cryotronics,
inc., U.S.A., was used to characterize magnetic prosperities of the metal
chelates. The effective Magnetic moment µeff was calculated from the
expression: µeff. = 2.84 (χ m X T) 1/2, where T = absolute temperature (K)
CHAPTER – 6 A comprehensive summary of work
This chapter of the thesis describes a comprehensive summary of the
work incorporated in the thesis.
Studies on metal chelates……………….. Chapter-1
6
General Transition metal chelates
A transition metal chelate is species consisting of a transition metal
coordinated (bonded to) one or more ligands (anionic or neutral non-metal
species) or polydentate ligands.
Ligands
Ligands are species (neutral or anionic) bonded to the metal ion. They
may be attached to the metal through a single atom (monodentate) or bonded
to the metal through two or more atoms (bidentate, tridentate.etc.).
Polydentate are called chelating ligands.
Ligands and oxidation state
Low oxidation state complexes can be stabilized by using ligands such
as cyanide and carbon monoxide (π acceptor ligands). Intermediate oxidation
state complexes often have ligands such as chloride, ammonia or water. High
oxidation state complexes usually have fluoride or oxide as ligands. Transition
metal complexes are important in catalysis, materials synthesis,
photochemistry, and biological systems. Display diverse chemical, optical and
magnetic properties.
Coordination number
Coordination number is the number of donor atoms bonded to the
central metal atom/ ion. Transition metal ions usually form complexes with a
well defined number of ligands. Complexes with coordination numbers four
and six are the most common, although two and five coordination are very
well established.
Studies on metal chelates……………….. Chapter-1
7
Coordination number and geometry are determined by a combination of:
- Metal ion size
- Ligand size - electronic factors (electron configuration, ligand type Linear complexes
Two coordinate linear complexes are almost exclusively found for d10
metal ions such as Ag+, Hg+ etc. These metals can adopt higher coordination
numbers under favorable circumstances. Some linear complexes are shown
in figure – 1.1
Cu (I) x Cu x
X = Cl, Br
Ag (I) H3N Ag NH3 +
Figure 1.1 Linear complexes
Four coordination
Four coordinate chelates typically have a tetrahedral or square planar
geometry. Square planar geometry is only found when there are electronic
reasons for it
Tetrahedral geometry is often found for steric reasons.
- Small metal ion and large ligands.
- Some example of tetrahedral complexes are shown in figure- 1.2
Studies on metal chelates……………….. Chapter-1
8
OV
OO
O
3-
OCr
OO
O
2
OMn
OO
O
Fe
Cl
ClClCl
Co
Cl
ClClCl
2
Figure1.2. Four coordinate complexes
Square planar complexes
Square planar coordination is rarely encountered for metals that do not
have a d8 electron configuration. For 3d metals this d8 configuration has to be
combined with a π accepter ligand, giving a large crystal field splitting, to get
square planar coordination. Some examples of square planar complexes are
shown in figure – 1.3
PdClCl
Cl Cl
2
PtNH3H3N
H3N NH3
2
AuClCl
Cl Cl
Figure 1.3 Square planar complexes
Studies on metal chelates……………….. Chapter-1
9
Five coordinate complexes
There are two common geometries for five coordinate complexes:
Trigonal bipyramidal and square pyramidal.
- TBP is sterically favored over square pyramidal.
- Energetic difference between the two geometries is small.
- Geometry can be dictated by the use of an appropriate ligand or by crystal
packing requirements. Examples of five coordinated complexes are
shown in figure – 1.4
Ni
CN
CN
CN
NC
NC
3
[Ni (CN) 5] 3-square pyramidal conformational
Ni
3
NC
NC
CN
CN
CN
Cu
3
Cl
Cl
Cl
Cl
Cl
[Ni (CN) 5] 3-trigonal bipyramidal conformational & [Cu (Cl) 5] 3-trigonal bipyramidal
conformational
Figure 1.4 Trigonal bipyramidal and square pyramidal complexes
Studies on metal chelates……………….. Chapter-1
10
Six coordinate complexes
By far the most common six coordinate geometry is octahedral, but
various distortions of the octahedral geometry and trigonal prismatic
coordination can be found. Example of six coordinated complexes is shown in
figure – 1.5A &1. 5B.
M
[Co (NH3)6]3+ Regular octahedral
M
Trigonal antiprism
M
Trigonal prismatic
Figure – 1.5 A. Six coordination complexes
Studies on metal chelates……………….. Chapter-1
11
(A) (B)
(C) (D) Figure –1.5B. (A) And (B) tetragonal distortations of a regular octahedral. (C)
Rhombic and (D) trigonal distortations
Trigonal prismatic coordination
Found in sulfide materials such as MoS2 and in complexes where the
ligand is small relative to the metal center (octahedral is sterically favored
over prismatic) or where special ligands are used. Some examples of trigonal
prismatic coordination are shown in figure – 1.6
Studies on metal chelates……………….. Chapter-1
12
Ligand with a small bite angle tends to favor trigonal prismatic
coordination.
ML
L
Bite angle
Bite angle
Zr
CH3H3C
CH3H3C
Zr(IV)
2-CH3
CH3
W
SS
SS
W(VI)
S
S
Figure – 1.6. Trigonal prismatic complexes
Higher coordination numbers
Some of the early transition metals are large enough to accommodate
more than six ligands. Some examples of 7- coordinate complexes are shown
in figure – 1.7 and 8-coordinate complexes are shown in figure -1.8 and 9-
coordinate complex is shown in figure –1. 9
Pentagonal bipyramidal occurs in [V (CN)7] 4- and [ZrF7] 3-
Studies on metal chelates……………….. Chapter-1
13
(a) (b)
(c)
Mo
CNCN
NC NC
NC
NC CN
CN
3-
[Mo (CN) 8]3-
Figure - 1.7 (a) pentagonal bipyramid (b) capped octahedron (c) capped
trigonal prism
[Zr (ox) 4] 4 – square antiprismatic [Mo (CN) 8] 3- Dodecahedral
Figure – 1.8 Eight coordinate complex
[ReH9]2-
Figure – 1.9 Nine coordinate complex
Studies on metal chelates……………….. Chapter-1
14
Schiff bases
Hugo Schiff described the condensation between an aldehyde and an
amine leading to a Schiff base in 1864 1. Schiff base ligands are able to
coordinate metals through imine nitrogen and another group, usually linked to
the aldehyde.
Ar-CHO + Ar’-NH2 → Ar-CH=N-Ar’ + H2O
Schiff base ligands are considered “Privileged ligands” because they
are easily prepared by the condensation between aldehyde and imines. Schiff
base ligands are able to coordinate many different metals and stabilized them
in various oxidation states, enabling the use of Schiff base metal
complexes for a large variety of useful catalytic transformations.
The presence of dehydrating agents normally favors the formation of
Schiff bases. MgSO4 is commonly employed as a dehydrating agent. The
water produced in the reaction can also be removed from the equilibrium
using a dean stark apparatus, when conducting the synthesis in toluene or
benzene. Finally, ethanol at room temperature or in refluxing condition is also
a valuable solvent for the preparation of Schiff bases.
Degradation of the Schiff bases can occur during the purification step.
Chromatography of Schiff bases on silica gel can cause some degree of
decomposition of the Schiff bases, through hydrolysis. It is better to purity the
Schiff base by crystallization.
Schiff bases are stable solids and can be stored without precautions.
Coordination of the metal with bi-or tri- dentate Schiff bases can produce
dimeric, or a saturated metal complex. Particularly with early transition metals,
which have a tendency to coordinate ligands in an octahedral manner, the
Complexation step realized in situ can produce a saturated octahedral
complex.
Studies on metal chelates……………….. Chapter-1
15
Importance of Schiff bases
Schiff bases derived from the Salicylaldehyde are well known
polydentate ligands2. Owing to the biological activity and variable bonding
potentialities in forming complexes with metal ions, the coordination chemistry
of Schiff bases has attracted the attention of several investigators3-9. Schiff
bases containing – RC= N – groups have gained importance because of
physiological and pharmacological activities associated with them.
Nitrogen, oxygen and/or sulphur containing ligands have been found to
possess significant biological and pharmacological activities and are used as
fungicides, tuberculostatic and anti carcinogenic agents10.the coordination
behavior of multidonor Schiff base ligands having sulphur-nitrogen donor sites
has received increasing attention because of their potentially ambidentate
nature and pharmacological importance11.
Some amino acid Schiff base complexes derived from o- hydroxyl
aromatic aldehyde are involved in variety of biological process12,13 e.g. as
catalyst of transamination, recemization and carboxylation reactions. it was
suggested that the active intermediates in transamination reactions were
metal Schiff base complexes. Moreover, they were used as radiotracers in
nuclear medicine and as antibacterial and anticancer reagents. Ternary
complexes containing an amino acid as a second ligand are of significance as
they are regarded as potential models for enzyme metal ion substrate
complexes; they have considerable biological activity.14. Some complex
compounds of gold with cysteine, glycine, histidine and tryptophan possess
selective antibacterial activity and low toxicity 15.
During the past decades 16-19 there has been a great deal of interest in
the synthesis and characterization of transition metal Schiff base chelates
because of their importance as catalysts in many reactions such as
carbonylation, hydroformylation, reduction, oxidation, epoxidation, hydrolysis,
in the chemical and petrochemical industry. The catalytic activity has been
reported to depend upon the structure of the Schiff base ligand.
Studies on metal chelates……………….. Chapter-1
16
Furthermore, binuclear complexes have been found to be better catalysts
than mononuclear complexes20, 21. Mixed-ligand complexes were used as
catalysts22-24.and also as biological models in understanding the structure of
biomolecules and biological processes25. The development of chiral Schiff
base ligands has received considerable attention since Jacobsen and
subsequently, Katsuki reported significant success in the asymmetric
epoxidation of unfunctionlized olefins by chiral Mn (III) Salen Schiff base
catalyst26. The chiral Schiff base complexes of transition metals are very
effective catalysts for asymmetric cyclopropanation and epoxidation of
alkenes; however they have not been developed to a level such that they
have found widespread use in organic synthesis27-30.
Schiff bases assumed new importance because of their antibacterial
and antifungal activities 31. Schiff bases and their metal complexes play a key
role in our understanding of the coordination chemistry of transition metal
ions. They may serve as models for biological important species, and find
applications in biomimetic catalytic reactions 32-33. Schiff bases containing S,
N and O, N donor atoms are important owing to their significant antifungal,
antibacterial and anticancer activity34. Transition metal complexes with
biologically active Schiff base ligands frequently exhibit higher biological
activity and lower toxicity than initial ligands. This makes possible their use in
medicine and biochemistry35. Many organic compounds used in medicine do
not have a purely organic mode of action; some are activated or
biotransformed by metal ions, others have a direct or indirect effect on metal
ion metabolism 36-37.
The Schiff bases derived from Salicylaldehyde and different amines are
considered to be suitable models for B6 vitamins38. Heterocyclic Schiff bases
metal complexes have attracted considerable attention due to their
remarkable antifungal, antibacterial and antitumour activity39-40. Copper di
Schiff bases have anticarcinogenic activity.41, Organo-Cobalt (III) Schiff base
chelates are proposed for combined cancer therapy42. Schiff bases have been
used as corrosion inhibitors43. The Schiff bases being antipyrine derivatives
may passes antibacterial, antiflammatory44, antipyretic and analgesic
activity45. Schiff bases from acylhydrazie and their complexes have strong
Studies on metal chelates……………….. Chapter-1
17
antitumor and antivirus activities46. A many hydrazones and their complexes
with metals have provoked wide interest in their diverse spectrum of biological
and pharmaceutical activities, such as anticancer, antitumor and antioxidative
activities, as well as the inhibition of lipid peroxidation etc47.
Transition metal complexes with Schiff bases derived from
arolhydrazines are known as potent inhibitors of DNA synthesis and cell
growth. Such complexes are also important for their possible pharmacological
applications48. Substituted pyrimidine derivatives and its Schiff bases with
salicylaldehyde have been reported as antitubercular, antipyretics, anticancer,
antihypertensive, cardiotonic, analgesic and anti- inflammatory drugs as well
as herbicides 49.
Bioinorganic chemistry
The understanding of the role of metal ions in biochemical process has
lead to the emergence of new fields of study, called inorganic biochemistry.
There are number of metal ions involved in biological systems and
there are number of potential coordinating biomolecules. Hence, the
biochemical reaction should involve the formation of metal complexes. The
bio- inorganic chemistry is of fundamental importance to the maintenance of
life because all living systems require an adequate supply of more than twenty
elements and of ligands related to these elements. These ingredients are then
composed into essential biochemicals. Metal ions, in limited quantity are
essential for life processes.
Uses of coordination compounds
A chiral Co (salen) has a well established ability to bind oxygen, useful
for the transfer of carbine and for opening epoxides.
Ni (salen) complex can behave as a bifunctional catalyst.
Bis (acetylacetonato) Co (II) and tris (acetylacetonato) Co (II) have
been found to possess fungicidal activity on cotton and linen fabrics50
Studies on metal chelates……………….. Chapter-1
18
K4 [Fe(CN)6 ] has been used as corrosion inhibitor for metal surface51
Manganese complexes of 2 [ (1-hydroxy -2- naphthallenyl) carbonyl]
benzoic acid are reported to be effective photo stabilizers for
polymers52
Complexes of thiosemicarbazones have been investigated as
medicinal since Domagk et.al.53 Discovered antitubercular activity in
this class of chemicals and have also been studied for antifungal and
antiviral properties.
Sorenson54 has observed that copper complexes of anti-inflammatory
compounds possess greater activity that the ligand themselves.
In petroleum industries transition metal complexes are used as
catalyst.
Ecofriendly dyes are Metal complex of dyes.
Metal complexes of Rh, Ni, Co, Ti, are used as catalyst for
hydrogenation, homogeneous, hydroformylation reaction, asymmetric
epoxidation of allylic alcohols.
Lead poisoning and copper poisoning are treated by injecting EDTA,
so that metal –EDTA complex is extracted in the urine.
Literature survey
Mi Hie Yi et.al 55-56 has been reported the synthesis of series of novel
aromatic diamines containing cyclohexane moieties. They have also
synthesized and characterized soluble polyimides from1, 1 – bis (4-
aminophenyl) cyclohexane derivatives. Jarrahpouret A. A. et.al57 Synthesized
novel azo Schiff base and their antibacterial and antifungal activities.
New multidentate Schiff base 1,4-bis (o-salicyldeneaminophenyl)-1,4-
dioxobutane and its Co(II), Ni(II) and Zn(II) complexes have been synthesized
by Yamanouchi et.al. 58, Urbach F. L. et.al 59 reported neutral tatradentate
Schiff base ligands derived from 1, 3-diamines and pyridine-2-
carboxaldehyde. .Some mixed Schiff base complexes of Cu (II) and Ni(II)
have been synthesized and characterized by elemental analysis, TLC
Studies on metal chelates……………….. Chapter-1
19
analysis, conductance , magnetic measurements and spectral analysis by
Bhattacharya P.K. et al.60
Syamal A & Kale K.S. have synthesized Cu (II) complexes with some
tridentate dibasic ONO Donor ligands61. Jani Bakul et.al62 Synthesized new
asymmetric tetradentate Schiff bases Cu(II) complexes and characterized
them by magnetic and spectral and elemental analysis. Ahmed I et.al.
Synthesized Cu (II) and Ni (II) complexes with a tetradentate Schiff base
derived from 2- hydroxyl naphthaldehyde and ethylene diamine and
characterized63. Mary Elizabatihe J et.al.64 synthesized some five co-ordinate
binuclear Schiff base Fe (II) complexes, and carried out Spectral and
magnetic study. Iftikar K. et.al65 - studies on bis (p–dimethyl amino
benzylidene) benzidine complexes of trivalent lanthanides. Marvin Illingworth
et al.66 synthesized eight – coordinate Zr (IV) Schiff base complex as a new
reagent for preparing coordination polymers. Co (II) Schiff base complexes as
oxygen carriers have been synthesized by Dian Chen and coworker67.
Mohmed E. M. Emam et.al.68 synthesized and studied physicochemical
parameters of Cu (II) Ni (II) Co (II) Pd (II) UO2(II) complexes with Schiff base
derived from α-benzylmonoxime. Masakazu Hirotsu et.al69 synthesized Mn
(III) complexes with optical active tetradentate Schiff base Ligands. Noboru
Yoshida et.al70 Synthesized Zn (II) metal complex with some bis – N,N- and
N,O- bidentate Schiff bases and chiral packing modes in solid state.
RamanN.et.al.71 Synthesized and characterized Cu (II), Ni (II), Mn (II), Zn (II)
and VO (II) Schiff base complexes derived from o-phenylendiamine and
acetanilide. Patel M.N. et. al. 72 synthesized coordination chain polymers of
some Mn (II) Cu (II), N i(II), Co (II), Zn (II) and Cd (II) metals with 1-carboxy-
1’-hydroxy-2,2’-(1-isonitriloethylidyne-4-nitrilomethylidenephenyl) diphenyl as
a Schiff base.
Non –symmetrical tetradentate vanadyl Schiff base complexes derived
from 1, 2-phenylene diamine and 1, 3 naphthalene diamine as catalysts for
the oxidation of cyclohexane have been synthesized by Daver M. Boghaei
and Sajjad Mohebi73. Canpla Erdal t et.al74 synthesis of mononuclear chelates
with Co (II), Ni(II), Cu(II), and Zn(II) derived from substituted Schiff base, 5-
Hydroxy salicyliden-p-amino acetophenoneoxime. Salen Schiff base metal
Studies on metal chelates……………….. Chapter-1
20
complexes in catalysis derived by Pier Giorgio cozzi 75.Mono - and Bi -
Nuclear metal complexes of Schiff base hydrazone derived from o-
hydroxylacetophenone and 2-amino–4-hydrazino-6-methylpyrimidine was
synthesized and characterized by Khalil S.M.E. et.al76. Cu (II), Ni (II), Co (II),
Zn (II) and Cd (II) complexes of Schiff base ligands derived from 7-formyl-8-
hydroxyquinoline and diaminonaphthalenes have been synthesized by Ismail
and Tarek77.
Synthesis, characterization and biological activity of Cu(II) complexes
with phenylglyoxal bis(thiosemicarbazones) have been done by Dharmarajan
and Murthy78. Zidan and et.al 79 reported the coordination properties of some
mixed amino acid metal complexes. Sekerci and Temel 80 reported the
synthesis of Mn (II), Co (II), Cu (II) and Zn (II) complexes with Schiff base
derived from condensation of 1, 2-bis (p-aminophenoxyl) ethane with
Salicylaldehyde. Cu (II), Co(II), Ni(II) complexes with Schiff bases derived
from aroylhydrazines have pharmacological applications is reported by Pal S
et.al81.Synthesis and Characterization of Copper (II), Nickel (II) and Cobalt (II)
Chelates with Tridentate Schiff Base Ligands Derived from 4-Amino-5-
hydroxynaphthalene-2,-7-disulfonic Acid was reported by Mehmet Tunel
et.al82. Raman N et.al83 synthesized, microanlytical, molar conductance and
magnetic prosperities and spectral analysis also done of Cu(II), Co(II), Ni(II),
and Zn(II) complexes of Schiff base derived from benzil-2,4-
dinitrophenylhydrazone with aniline.
Synthesis, Characterization and Catalytic Activity of Salen-type Schiff
Base Polychelates have been done by Bansod et.al84. Khan et.al85
synthesized and characterized, unsymmetrical tetradentate Schiff base Mn(II),
Ni(II) and Cu(II) complexes derived from 2,3-diaminophenol and
Salicylaldehyde and 5- bromosalicylaldehyde. Thaker et.al 86Synthesized and
spectroscopic studies of mononuclear mixed ligand Schiff base complexes of
Cu (II). Sen Soma. et.al87 Synthesized and characterized Zn (II), Cd (II),
Co(II), Co(II) and Mn(II) complexes with the Schiff base derived from 2-
dimethylaminoethylamine and o- vanillin. Joseph J. et.al88 synthesized and
characterized and thermal analysis of Mn(II), Co(II), Ni(II), Cu (II), Cd(II) and
Studies on metal chelates……………….. Chapter-1
21
Hg(II) metal complexes with Schiff bases derived from 3-formyl-4-
hydroxycoumarin and semicarbazone.
Natarajan K. et.al89 was prepared hexa- coordinated Ru (II) complexes
by hydrolytic cleavage of Schiff bases. Masakatsu Shibasaki et. Al90 reported
the utility of a hetrobimetalic Cu- Sm- Schiff base complex as a syn- Selective
catalytic asymmetric Nitro – mannich reaction. Ali M. Ali, Ayman H. Ahmed,
et.al91 Synthesized Co (II), Ni(II), Fe(III) And Pd(II) Schiff base metal chelates
and corrosion inhibition of Schiff base derived from o-toludine. Sancak
Kemal et.al92 Synthesized Cu (II), Ni (II) Fe (II) complexes with a new
substituted (1, 2, 4) triazole Schiff base and also characterized. Dehghanpour
Saeed et.al. 93 Synthesized and characterized Co (II), Ni (II), and Zn (II),
complexes with N, N’-bis (2-nitrocinamaldehyde)-1,2-diiminoethen ligand.
Samanta Brajagopal et.al.94 Synthesize, Structural, Characterization and
biochemical activity study of new Cu (II) Complexes with polydentate
chelating Schiff base ligands. Synthesis, Spectral Characterization and DNA
Cleavage study of heterocyclic Schiff base Zn (II), Co (II), Ni (II) metal
complexes by Raman N. et.al95.Catalytic activity of polymer anchored N, N’-
bis (o-hydroxy Acetophenone) ethylene diamine Schiff base complexes of
Fe(III), Cu(II) and Zn(II) ions in oxidation of phenol have been synthesized
and characterized by Gupta K.C. et.al96. Bis(O-vanillin) benzidine (o-v2bzh2)
as a binucleating ligands: synthesis, characterization and 3D molecular
modeling and analysis of some binuclear complexes of o-v2bzh2 with Cu (II),
Ni (II), Co (II), Mn (II), Zn (II), Sm (III) and UO2(VI) have been reported by
Maurya R C et.al 97.Rubavathy Jaya Priya A et.al 98 have been synthesized,
spectral characterized and antimicrobial activity of Cu (II), Ni (II), VO (II) metal
complexes with quadridentate Schiff base.
Synthesis, characterized by elemental analyses, spectral and thermal
(TGA-DTA) methods, magnetic and conductance measurements and
biological activity of Cr(III),Fe(III), and Co(III), complexes of tetradentate
ONNO Schiff base ligands as 1,4-bis[3-(2-hydroxy-1-naphthaldimine) propyl ]
piperazine and 1,8-bis[3-(2-hydroxy-1-naphthaldimine)-p-menthane have
been repotted by Eren et.al99. Modi et.al100 synthesized tetradentate Schiff
base complexes of VO (IV) and Cu (II) and evaluated them by spectral,
Studies on metal chelates……………….. Chapter-1
22
coordination and thermal aspects. Hamadi Temel et.al101 Synthesized and
spectroscopy studies of novel transition metal complexes with Schiff base
synthesized from 1,4-bis-(o-aminophenoxy) butane and Salicyldehyde. Ding
Y. et.al.102Synthesized mono and di Schiff base complexes of Ni (II) and
structurally characterized by singal crystal X-ray diffraction studies. Prasad
Archana et.al. 103 Synthesized, spectral and electrochemical studies of Co (II)
and Zn (II) complexes of novel Schiff base derived from Pyridoxal. Azza A.A.
Abu-Hussen et.al.104 Synthesized new mononuclear transition metal
complexes of macrocyclic Schiff bases derived from 1, 1’-diacetylferrocin and
evaluated them by spectroscopic and biologically. Tanmay Chatopadhyay
et.al105have been synthesized and characterized and studies of
photoluminescence of mono and dinuclear Zn (II) complexes of Schiff base
ligands. Patel R. N. et. Al106. Have been done Spectroscopic, structural and
magnetic studies of nickel (II) complexes with tetra- and pentadentate ligands.
Present Work
The research work described in the thesis is in connection with the
experimental, analytical and spectral, thermal, magnetic studies of some
transition metal chelates of some Schiff’s bases. The results of these
investigations are presented in following chapters.
Chapter – 2 contains the experimental methods used for the Synthesis of the
Schiff’s bases and their metal chelates.
Chapter –3 deals with the description of analytical and spectral study of
Schiff’s bases and their metal chelates.
Chapter –4 described the Themogravimetric analysis of the metal chelates. Chapter –5 contains the description of magnetic measurements of metal
chelates.
Chapter – 6 deals with comprehensive summary of the work.
Studies on metal chelates……………….. Chapter-1
23
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Studies on metal chelates……………… Chapter-2
29
2.1 Synthesis of Schiff bases
Synthesis of Amine: 1, 1’ bis (4- aminophenyl) cyclohexane [A].
Aromatic amine [A] was synthesized by acid catalyzed condensation of
Cyclohexanone and excess aniline 1-3.Thus, 0101(10.55ml) mole
Cyclohexanone and 0.267 (24.5ml) mole aniline in 25 ml of 35% HCl at 110oC
for 17-18 hours. After, the resultant solution of 1, 1’ bis (4-aminophenyl)
cyclohexane hydrochloride was stared with 1 gm activated charcoal and 50ml
boil water than cooled to room temperature. At room temperature resinous
mass is separated it was filtrate off. The clear red solution was made alkaline
with drop wise addition of 5% NaOH solution, A white presipate of amine [A]
was separated and amine [A] was filtrated ,washed well with hot distilled
water and dried in an oven at 50-60oC. Amine [A] was recrystallized from
benzene to gate light yellow crystals. The yield was 51% and M.P.112oC.The
purity of amine [A] was checked by TLC in CHCl3 –n – Hexane (70:30) solvent
system.
REACTION SCHEME
O
+
NH2
[1] 35 % HCl [2] 5 % NaOH
2 NaCl + 2H2O
0.101Mol0.267Mol
H2N NH2
110oC
17-18 h.
Studies on metal chelates……………… Chapter-2
30
Physical constants of amine [A] 1, 1’ bis (4- aminophenyl) cyclohexane
H2N NH2
Table-2.1
Sr.
No.
Molecular
Formula
Molecular
Weight
(gm)
Melting
Point
(o c)
Color
Rf
Value
1 C18H22N2 266 112 Light
yellow 0.59
TLC Solvent system is Ethyl acetate – n-hexane (70:30v/v)
Studies on metal chelates……………… Chapter-2
31
Synthesis of Schiff base: (L1-o-v-AH2) 6,6’-(4,4’-(cyclohexane-1,1-diyl)
bis(4,1-phenylene)) bis (azan-1-yl-1- ylidene) bis (methan-1-yl-1ylidene)
bis (2-methoxy phenol)
Schiff base L1-o-v-AH2 was synthesized by condensation of amine [A]
and substituted aromatic aldehydes 4 in ethanol using glacial acetic acid as a
catalyst at reflux temperature. Thus into a 250ml RBF, 50ml solution of 2-
hydroxy -3- methoxy benzaldehyde (7.6 gm, 50 mmol) in hot ethanol and 50
ml solution of 1,1’ bis(4-aminophenyl)cyclohexene (6.65gm, 25 mmol) in hot
ethanol, using 2 ml glacial acetic acid as a catalyst, and reaction mixture was
reflux on water bath for 4-5 hours. A solid mass was separated out on cooling,
it was suction filtrated, washed with sodium bisulfate to remove unreact
aldehydes, water and finally with ethanol. Subsequently dried over anhydrous
CaCl2 in desiccators. The Schiff base is soluble in common solvent like CHCl3,
benzene, CCl4, DMF. The Schiff base was recrystallized from chloroform and
purity was checked by TLC in appropriate solvent system at room
temperature. The yield was 71%. Analytical details are described in Table 3.1,
in chapter- 3 on page 43.
REACTION SCHEME
+
CHO
0.025 mol 0.05 mol
[1]EtOH[2] Glacial Acetic Acid
[3] Reflux 2 -7 hours
H2N NH2
HO
N NHC
OH HO
CH
OCH3 H3CO
H3CO
Studies on metal chelates……………… Chapter-2
32
Physical constants of Schiff base (L1-o-v-AH2)
NN
HC
OH HO
CH
OCH3 H3CO
Table-2.2
Sr.
No.
Molecular
Formula
Molecular
Weight
(gm)
Melting
Point
(o c)
Color
Rf
Value
1 C34H34N2O4 534.62 196 Orange 0.53
TLC Solvent system is Ethyl acetate- n-hexane (80:20v/v)
Studies on metal chelates……………… Chapter-2
33
Synthesis of Schiff base: (L2 - Sal – AH2)2,2’-(4,4’-(cyclohexane-1,1-
diyl)bis(4,1-phenylene))bis(azan-1-yl-1-ylidene)bis(methan-1-yl-1-ylidene)
diphenol
Schiff base L2-Sal – AH2 was synthesized by condensation of amine [A]
and substituted aromatic aldehydes4 in ethanol using glacial acetic acid as a
catalyst at reflux temperature. Thus into a 250ml RBF, 50ml solution of
Salicylaldehyde (5.25ml, 50 mmol) in hot ethanol and 50 ml solution of 1,1’
bis (4-aminophenyl) cyclohexene (6.65gm, 25 mmol) in hot ethanol, using 2
ml glacial acetic acid as a catalyst, and reaction mixture was reflux on water
bath for 4-5 hours. A solid mass was separated out on cooling, it was suction
filtrated, washed with sodium bisulfate to remove unreact aldehydes, water
and finally with ethanol. Subsequently dried over anhydrous CaCl2 in
desiccators. The Schiff base is soluble in common solvent like CHCl3,
benzene, CCl4, DMF. The Schiff bases were recrystallized from acetone, and
purity was checked by TLC in appropriate solvent system at room
temperature. The yield was 69%. Analytical details are described in Table 3.1
in chapter- 3 on page 43.
REACTION SCHEME
+
CHO
OH
0.025 mol 0.05 mol
[1]EtOH[2] Glacial Acetic Acid
[3] Reflux 2 -7 hours
NN
HC
OHHO
CH
H2N NH2
Studies on metal chelates……………… Chapter-2
34
Physical constants of Schiff base (L2 - Sal – AH2 )
NN
HC
OH HO
CH
Table -2.3
Sr.
No.
Molecular
Formula
Molecular
Weight
(gm)
Melting
Point
(o c)
Color
Rf
Value
1 C32H30N2O2 474.57 154 Light
Yellow 0.62
TLC Solvent system is Ethyl acetate - n-hexane (80:20 v/v)
Studies on metal chelates……………… Chapter-2
35
Synthesis of Schiff base:(L3 -O-H-Naph.-AH2) 1,1’-(4,4’(cyclohexane-1,1-
diyl)bis(4,1-phenylene))bis(azan-1-yl-1-ylidene)bis(methan-1-yl-1-
ylidene)dinaphthalen-2-ol
Schiff base L2-Sal – AH2 was synthesized by condensation of amine [A]
and substituted aromatic aldehydes4 in ethanol using glacial acetic acid as a
catalyst at reflux temperature. Thus into a 250ml RBF, 50ml solution of 2-
hydroxy -1- Naphthaldehyde (8.6 gm, 50 mmol) in hot ethanol and 50 ml
solution of 1,1’ bis (4-aminophenyl) cyclohexene (6.65gm, 25 mmol) in hot
ethanol, using 2 ml glacial acetic acid as a catalyst, and reaction mixture was
reflux on water bath for 5-8 hours. A solid mass was separated out on cooling,
it was suction filtrated, washed with sodium bisulfate to remove unreact
aldehydes, water and finally with ethanol. Subsequently dried over anhydrous
CaCl2 in desiccators. The Schiff base is soluble in common solvent like CHCl3,
benzene, 1, 4-dioxane, DMF. The Schiff bases were recrystallized from
benzene and purity was checked by TLC in appropriate solvent system at
room temperature. The yield was 72%. Analytical details are described in
Table 3.1,in chapter- 3 on page 43.
REACTION SCHEME
+
CHO
0.025 mol 0.05 mol
[1]EtOH[2] Glacial Acetic Acid
[3] Reflux 2 -7 hours
NN
HC
OH HO
CH
H2N NH2
HO
Studies on metal chelates……………… Chapter-2
36
Physical constants of Schiff base: (L3 -O-H-Naph.-AH2)
NN
HC
OH HO
CH
Table - 2.4
Sr.
No.
Molecular
Formula
Molecular
Weight
(gm)
Melting
Point
(o c)
Color
Rf
Value
1 C40H34N2O2 574.68 205 Yellow 0.61
TLC Solvent system is Ethyl acetate - n-hexane (80:20 v/v)
Studies on metal chelates……………… Chapter-2
37
2.2 Synthesis of Metal Chelates of Schiff bases:
Synthesis of Copper chelates:-
The metal chelates of Schiff bases, L1-o-v-AH2 were synthesized according
literature 5-8 by mixing 1:1 chloroform-ethanol solution (30ml) of Schiff base,
L1-o-v-AH2 (2.673gm,5mmol) with an ethenolic solution (30ml) of metal
acetate (5mmol,0.998gm Cu(CH3COO)2·H2O) in 1:1 mole ratio. The resulting
mixture was refluxed with staring on a magnetic stirrer equipped with heater
for 5-7 hours. On cooling, the colored chelates precipitated out, which was
filtered by suction, washed several times with ethanol and finally with ether,
and dried over anhydrousCaCl2. All metal chelates are insoluble in common
organic solvent but is soluble in DMSO and DMF. The general reaction
scheme for synthesis of all metal chelates is as following. The Same
procedure was adopted with the other ligands. The physical and elemental
analysis are given in table 3.11 in chapter 3 on page 61.
Cu (CH3COO)2 ·H2O + L1-o-v-AH2 →
Cu (L1-o-v-A) .H2O + 2 CH3COOH
Synthesis of Nickel chelates:-
The metal chelates of Schiff bases, L1-o-v-AH2were synthesized according
literature5-8 by mixing 1:1 chloroform-ethanol solution (30ml) of Schiff base,
L1-o-v-AH2 (2.673gm,5mmol) with an ethenolic solution (30ml) of metal
acetate (5mmol,1.224gm NI(CH3COO)2· 4H2O) in 1:1 mole ratio. The resulting
mixture was refluxed with staring on a magnetic stirrer equipped with heater
for 5-6 hours. On cooling, the colored chelates precipitated out, which was
filtered by suction, washed several times with ethanol and finally with ether,
and dried over anhydrousCaCl2. All metal chelates are insoluble in common
organic solvent but is soluble in DMSO and DMF.
Studies on metal chelates……………… Chapter-2
38
The general reaction scheme for synthesis of all metal chelates is as
following. The Same procedure was adopted with the other ligands. The
physical and elemental analysis is given in table 3.14 in chapter 3 on page 70.
Ni (CH3COO)2 ·4H2O+ L1-o-v-AH2→
Ni (L1-o-v-A) 2H2O + 2 CH3COOH +2H2O
Synthesis of Cobalt chelates:-
The metal chelates of Schiff bases, L1-o-v-AH2were synthesized according
literature5-8 by mixing 1:1 chloroform-ethanol solution (30ml) of Schiff base,
L1-o-v-AH2 (2.673gm,5mmol) with an ethenolic solution (30ml) of metal
acetate (5mmol,1.245gm Co(CH3COO)2· 4H2O)in 1:1 mole ratio. The resulting
mixture was refluxed with staring on a magnetic stirrer equipped with heater
for 5-6 hours. On cooling, the colored chelates precipitated out, which was
filtered by suction, washed several times with ethanol and finally with ether,
and dried over anhydrousCaCl2. All metal chelates are insoluble in common
organic solvent but is soluble in DMSO and DMF. The general reaction
scheme for synthesis of all metal chelates is as following. The Same
procedure was adopted with the other ligands. The physical and elemental
analysis is given in table 3.17 in chapter 3 on page 79.
Co (CH3COO) 2 ·4H2O + L1-o-v-AH2→
Co (L1-o-v-A) 2H2O + 2 CH3COOH + 2H2O
Studies on metal chelates……………… Chapter-2
39
Synthesis of Zinc chelates:-
The metal chelates of Schiff bases, L1-o-v-AH2 were synthesized according
literature5-8 by mixing 1:1 chloroform-ethanol solution (30ml) of Schiff base,
L1-o-v-AH2 (2.673gm,5mmol) with an ethenolic solution (30ml) of metal
acetate (5mmol,1.1gm Zn(CH3COO)24H2O) in 1:1 mole ratio. The resulting
mixture was refluxed with staring on a magnetic stirrer equipped with heater
for 5-7 hours. On cooling, the colored chelates precipitated out, which was
filtered by suction, washed several times with ethanol and finally with ether,
and dried over anhydrousCaCl2. All metal chelates are insoluble in common
organic solvent but is soluble in DMSO and DMF. The general reaction
scheme for synthesis of all metal chelates is as following. The Same
procedure was adopted with the other ligands. The physical and elemental
analysis is given in table 3.20 in chapter 3 on page 88.
Zn (CH3COO)2 ·4H2O+ L1-o-v-AH2 →
Zn (L1-o-v-A) 2H2O + 2 CH3COOH +2H2O
Studies on metal chelates……………… Chapter-2
40
References:
1. Schiff H. Ann. Suppl.; 3, 343, (1864)
2. Mi Hie YI, Wenxi Huang, Moon Young Jin, and Kil–Yeong Choi,
Macromolecules, 30 (19), 5606-5611(1997).
3. Myska,J. Chem. Abstr., 61,14558 (1964)
4. Vogel A. R. Texbook of Practical Organic Chemistry,4Th ed.;
Longman,inc.;New York, (1981).
5. Bhattacharya P.K., Kohli Rakesh Kumar, Bul. Chem. Soc. Japan,
49,2872-2874 ( 1976)
6. Syamal A., Kale K.S., Ind. J. Chem., 16A, 46-48 (1978)
7. Jani Bakul, Bhattacharya P. K., Ind. J. Chem., 18A, 80 (1979)
8. Ahmed I. , Akhtar F., Ind. J. Chem., 20A, 737 (1981)
Studies on metal chelates……………….. Chapter-3
41
Studies on metal chelates……………….. Chapter-3
42
CHARACTERISATION OF THE SCHIFF BASES 1. ELEMENTAL ANALYSIS:
The microanalysis of Carbon and hydrogen and nitrogen were
performed on a Vario EL-III analyzer. The result of elemental analysis and
general properties like color, empirical formula and formal weight of Schiff
bases are given in table –3.1 on page No. 43
2. ABSORPTION SPECTRA
The absorption spectra of the Schiff bases solution in chloroform was
recorded on a Simadzu 2401 spectrophotometer. The nature of the absorption
curves are shown in fig. 3.1 on page 44.The result are presented in table 3.2
on page no.45
3. IR SPECTRA
The infrared spectra of the amine A and Schiff bases were recorded
using KBr discs on Perkin Elmer spectrophotometer (PerkinElmer RX1)
between 4000-400 cm-1. The IR spectra are represented as in fig. 3.3 to 3.5
on page 47 - 49.The results are presented in table- 3.4 - 3.6
4. NMR SPECTRAL STUDY:
The nuclear magnetic resonance spectrums of the ligands were
recorded in CDCl3 solution on BRUKER DRX-300 Spectrometer [300MHz].
The results obtained are presented in table – 3.7- 3.9 on page no.50-52.
The nature of the NMR spectra shown in fig. 3.6 -3.8 on 50-52
5. MASS SPECTRAL STUDY:-
The mass spectrums of the Schiff bases were on Jeol 102 / Da-600
mass spectrometer at room temperature. Corresponding mass spectra are
shown in fig 3.9 - 3.11 on page 53-55.
Studies on metal chelates……………….. Chapter-3
43
TABLE – 3.1
ELEMENTAL ANALYSIS OF SCHIFF BASES
Sr. No.
Schiff bases
Molecular Formula
Collar formula Weight (gm)
% of Carbon %of Nitrogen %of Hydrogen
found calculate found calculate found calculate
1 L1-o-v-AH2 C34H34N2O4 Orange 534.62 76.31 76.37 5.18 5.23 6.38 6.41
2 L2 - Sal – AH2 C32H30N2O2 Light
Yellow 474.57 80.92 80.98 5.86 5.90 6.32 6.37
3 L3 -O-H-Naph.-AH2 C40H34N2O2 Yellow 574.68 83.52 83.59 4.80 4.87 5.93 5.96
Studies on metal chelates……………….. Chapter-3
44
FIG. 3.1 UV SPECTUM OF SCHIFF BASES
Studies on metal chelates……………….. Chapter-3
45
TABLAE – 3.2
Absorption maximum (λ max.) of the Schiff bases.
Sr. No.
Schiff’s bases λ max[nm]
1 L1-o-v-AH2 326
282
2 L2 - Sal – AH2 346
273
3 L3 -O-H-Naph.-AH2
464.50
444.00
264.00
Studies on metal chelates……………….. Chapter-3
46
FIG. 3.2 IR Spectrum analysis of amine A
TABLE –3.3
Type Vibration mode
Frequency cm-1
Ref.
Observed Reported
Primary amines
-NH2
v(OH) N-H aym. N-H sy. N-H def. C-N str. N-H wag.
3340.5 3211.3
3421.7
1624
1276.8
819.7
3550-3350
3450-3250
1650-1580
1340-1250
850-750
1-3
Alkane -CH2-
C-H str. (asym.) C-H str. (sym.) C-H def.(asym.) C-H def.(sym.)
2929.3 2854.5 1450.4
1276.8
2975-2920 2880-2860 1470-1435 1395-1370
1-3
Aromatic
C-H str. C=C C-H ( i. p. d. ) C-C ( o. o. p. d. )
1512.1 1276.8 1186.1 1014.5 819.7
1579 ± 5
1258 ± 10
1175 ± 5 817 ± 14
1-3
Studies on metal chelates……………….. Chapter-3
47
FIG. 3.3 IR Spectrum analysis of Schiff base L1-o-v-AH2
Instrument: Perkin Elmer FT-IR Spectrophotometer Frequency range: 4000-400cm-1
TABLE – 3.4
Type Vibration mode
Frequency cm-1
Ref.
Observed Reported
Hydroxyl-OH
O-H str.
O-H def.
3450.3
1406.3
3650-2590
1410-1310 1-3
Alkane CH3
C-H str. (asym.) C-H str. (sym.) C-H def.(asym.) C-H def.(sym.)
2936.0 2865.7 1463.8 1365.0
2975-2920 2880-2860 1470-1435 1395-1370
1-3
Aromatic
C-H str. C=C C-H ( i. p. d. ) C-C ( o. o. p. d. )
3068.5 1509.6 1082.5 828.4
3100-3000 1585-1480 1125-1090
860-810
1-3
Schiffs base
N=C str. C-N def.
1615.7 1255.7
1650-1580 1350-1200
1-3
Studies on metal chelates……………….. Chapter-3
48
FIG.3.4 IR Spectrum analysis of Schiff base: L2 - Sal – AH2
Instrument: Perkin Elmer FT-IR Spectrophotometer Frequency range: 4000-400cm-1
TABLE -3.5
Type Vibration mode
Frequency cm-1
Ref.
Observed Reported
Hydroxyl-OH O-H str.
O-H def. 3451
1407.7
3650-2590
1410-1310 1-3
AlkaneCH2
C-H str. (asym.) C-H str. (sym.) C-H def.(asym.) C-H def.(sym.)
2925.9 2869.1 1454.7 1396
2975-2920 2880-2860 1470-1435 1395-1370
1-3
Aromatic
C-H str. C=C C-H ( i. p. d. ) C-C ( o. o. p. d. )
3060 1572.3 1114.5
830
3100-3000 1585-1480 1125-1090
860-810
1-3
Schiffs base
N=C str. C-N def.
1626.7 1277.7
1650-1580 1350-1200
1-3
Studies on metal chelates……………….. Chapter-3
49
FIG.3.5 IR Spectrum analysis of Schiff base: L3 -O-H-Naph.-AH2
Instrument: Perkin Elmer FT-IR Spectrophotometer Frequency range: 4000-400cm-1
TABLE- 3.6
Type Vibration mode
Frequency cm-1
Ref.
Observed Reported
Hydroxyl-OH O-H str.
O-H def. 3426.9 1326.1
3650-2590
1410-1310 1-3
AlkaneCH2
C-H str. (asym.) C-H str. (sym.) C-H def.(asym.) C-H def.(sym.)
2930.7 2864.5 1498.9 1246.2
2975-2920 2880-2860 1470-1435 1395-1370
1-3
Aromatic
C-H str. C=C C-H ( i. p. d. ) C-C ( o. o. p. d. )
3041.0 1571.5 1085.1 822.8
3100-3000 1585-1480 1125-1090
860-810
1-3
Schiffs base
N=C str. C-N def.
1621.0 1173.7
1650-1580 1350-1200
1-3
Studies on metal chelates……………….. Chapter-3
50
FIG.3.6 : 1H NMR SPECTRA OF Schiff base L1-o-v-AH2
TABLE – 3.7
Sample NMR chemical shifts, ppm
L1-o-v-AH2
OCH3HO
d
ef
1.504 , 6H,s β +γ –CH2
2.329-2.511, 4H s α –CH2
3.853 ,6H s –OCH3
6.472-6.493 2H f Ar-Hf
6.881 2H e Ar-He
6.97 2H d Ar Hd
7.109-7.1229 4H d Ar Hb
7.199 -7.246 4H d Ar Ha
8.912 2H s CH=N
13.3175 2H s Ar-OH
Studies on metal chelates……………….. Chapter-3
51
FIG.3.7 : 1H NMR SPECTRA OF Schiff base L2 - Sal – AH2
TABLE 3.8
Sample NMR chemical shifts, ppm
L2-sal-AH2
HOd
e
fg
1.5837 ( 6H, s, β + γ, -CH2),
2.1731 (4H, s, α, - CH2)
6.936 -6.883 (2H, dd , Ar- Hd ,
7.016-6.966 (2H,dd, Ar-Hf ,
7.222-7.187 (4H,d, Ar-Hb,
7.371-7.319 (8H, m, Ar-H (a+e+g),
8.578 (2HC, s, -CH=N-),
13.365 (2H, s, Ar-OH (h))
Studies on metal chelates……………….. Chapter-3
52
FIG. 3.8 1H NMR SPECTRA OF Schiff base L3-O-H-Naph.-AH2
TABLE- 3.9
Sample NMR chemical shifts, ppm
L3-O-H-Naph.-AH2
ΗΟ
d
e
f
gh
i
1.59 ( 6H, s, β + γ, -CH2),
2.301 (4H, s, α, - CH2)
7.16 ( 4H, s Hb Ar-Hb)
7.26 (4H, s Ha Ar-Ha)
7.27 -7.80 (12H ,m d+e+f+g+h+i )
8.38 (2HC, s, -CH=N-),
13.167 (2H, s, Ar-OH
Studies on metal chelates……………….. Chapter-3
53
FIG. 3.9 MASS SPECTRUM OF SCHIFF BASE L1-o-v-AH2
Studies on metal chelates……………….. Chapter-3
54
FIG. 3.10 MASS SPECTRUM OF SCHIFF BASE L2 - Sal – AH2
Studies on metal chelates……………….. Chapter-3
55
FIG. 3.11 MASS SPECTRUM OF SCHIFF BASE L3-O-HNaph.-AH2
Studies on metal chelates……………….. Chapter-3
56
Studies on metal chelates……………….. Chapter-3
57
Characterization of Cu (II) Schiff bases metal chelates 1. Solubility:
All Cu (II) Schiff bases metal chelates are insoluble in water and common
organic solvent like chloroform, benzene, ether, ethanol and other organic
solvents .it is soluble in DMF, DMSO
The chelates do not show clear melting point. It gets char at temperature
above 3100 C
2. Conductivity Measurements:
The conductance data for co-ordination compounds provides unimportance
experimental evidence in determining the nature of co-ordination compounds
(whether ionic or covalent).The conductivity of copper chelates was
determined using systronics conductivity bridge model no.361.since the
solubility of chelates is less in common organic solvents. 0.001M solution in
DMSO was used to measured conductivity. The molar conductivity was
calculated using the formula
Molecular conductivity = 1000 x K
C
Where, K = Conductivity of the solution of the metal chelates in DMSO.
C = Concentration of the chelates.
The result is presented in Table 3.10 on page no. 60 the low
conductivity conforms the copper chelates are non-ionic in nature.
3. Molecular Weight Determination:
Because of the less solubility of the metal chelates under study in common
organic solvent the molecular weight of Cu (II) Schiff bases chelates was
determined by Rest’s Camphore method.
Studies on metal chelates……………….. Chapter-3
58
Rest’s Method:
About 50 mg. of chelates was weighted in a test tube. About 200mg. of
the camphor was added and weighed again. The test – tube was corked
loosely and heated gently on a flame to obtain a clear homogeneous solution.
The tube is shaken and allowed to cool. a small portion of the solidified
mixture is taken, powdered and its melting point determined. The
determination of melting point is repeated to get consistent results. The
melting point of pure camphor is also determined so that the depression in the
melting point can be calculated.
The same experiment is repeated with a known compound, i.e., naphthalene
and the value of k calculated for camphor. The molecular weight was
calculated by using the formula.
M = K x w x 1000
t x W
Where, K = Molecular depression constant
w = weight of complex W = weight of camphor t = Depression of the melting point The result is presented in table -3.10 on pages No.60 4. Elemental Analysis:
This involved the estimation of, copper, Carbon, hydrogen and nitrogen
present in the complex. C, H, and N were performed on a Vario EL-III
analyzer. for copper estimation a known weight of chelates was broken down
in sixty percent A.R. perchloric acid on heating till a clear solution was
obtained, it was transferred to 250 ml. measuring flask and the total volume
was made to 250ml by adding required amount of distilled water. From this
solution copper was estimated complexometrically with EDTA, carbon,
Studies on metal chelates……………….. Chapter-3
59
hydrogen and nitrogen were estimated on Vario EL-III analyzer the result is
given in table 3.10 on page No.60. 4-5
5. Absorption Spectra of Cu (II) Schiff bases chelates:
The compounds containing transition metal exhibit a great range of
colors of varying intensity. Thee colures arise from the characteristic
absorption in the visible part of the electromagnetic spectrum. The
characteristics visible absorption spectra of the complexes as usually arise
due to electronic transition in the d- orbitals of the metal ions and therefore
they are known as d-d spectra. The d- orbitals in oh or d4h symmetry are of
type g and hence these electronic transitions amongst d- orbitals are Laport-
forbidden transitions and hence are of low intensity but they are allowed by
spin selection rule. The organic part of the ligand shows characteristic
absorption maxima in UV region. From spectral properties of the metal
complexes as well as the effect of spectral studies information in collected
regarding the different substitution in the ligand molecule. The copper
complex of known weight dissolved in DMSO and thus known concentration
solution was prepared.
Absorption spectra of copper complex of Schiff’s bases was taken
using Simadzu 2401 spectrophotometer the nature of the absorption curves
are shown in fig. 3.12 on page -61.the results are summarized in Table 3.11
on page no. 62.
6. IR SPECTRA:
The infrared spectra of the Schiff’s bases Cu (II) metal chelates were
recorded using KBr discs on Perkin Elmer spectrophotometer (PerkinElmer
RX1) between 4000-400 cm-1
. The IR spectra are represented as in fig.3.13 –
3.15 on page no.63-65. The results are presented in table-no.3.12 on page
no.66.
Studies on metal chelates……………….. Chapter-3
60
TABLE – 3.10
PHYSICAL AND ELEMENTAL ANALYSIS OF Cu (II) METAL CHELATES
Sr. No.
Metal chelates
Molecular Formula
formula Weight (gm)
Collar
Decomposition temp Co.
Yield Conductivity mohs .cm2.mol-1
% Found(calculated)
C H N Metal %
1 Cu(II)(L1-o-v-A)2H2O
Cu(C34H36N2O6) 632.17 Leaf
green >310 66 12.5
64.51 (64.59)
5.71
(5.73)
4.39
(4.43)
10.01
(10.05)
2 Cu(II)(L2 -Sal –A)2H2O
Cu(C32H32N2O4) 572.12 Light green
>318 62 11.8 67.13
(67.17) 5.60
(5.63) 4.85
(4.89) 11.07
(11.10)
3 Cu(II)(L3 -O-H-Naph.-A) 2H2O
Cu (C40H36N2O4) 672.23 Dark green
>310 65 8.6 71.42
(71.46) 5.35
(5.39) 4.13
(4.16) 9.43
(9.45)
Studies on metal chelates……………….. Chapter-3
61
FIG.3.12 ABSORPTION SPECTRA OF THE Cu (II) METAL CHELATES
Studies on metal chelates……………….. Chapter-3
62
TABLE – 3.11
Absorption Maximum (λ Max) of Cu (II) Schiff bases metal chelates.
Sr.No. Metal chelates λmax.(nm.)
1 Cu(II)( L1-o-v-A)2H2O
597.00
372.00
277.50
257.50
2 Cu(II)( L2 - Sal – A)2H2O
727.00
401.00
306.00
257.50
3 Cu(II)(L3 -O-H-Naph.-A) 2H2O
411.00
304.00
257.00
221.00
Studies on metal chelates……………….. Chapter-3
63
Fig. 3.13 IR SPECRA OF Cu (II) L1-o-v-A .2H2O
Studies on metal chelates……………….. Chapter-3
64
Fig.3.14. IRSPECRAOF Cu (II) L2 - Sal – A 2H2O
Studies on metal chelates……………….. Chapter-3
65
Fig.3.15 IR SPECRA OF Cu (II) L3 -O-H-Naph.-A 2H2O
Studies on metal chelates……………….. Chapter-3
66
TABLE – 3.12
Infrared spectral data of the Cu (II) metal chelates
Compounds ν (C=N)cm-1
ν(C-O) cm-1
ν (M-N)cm-1
Cu(II)(L1-o-v-A) .2H2O 1607.5 1441.7 551.0
Cu(II)(L2 –Sal A)2H2O 1610.5 1444.7 553.0
Cu(II)( L3 -O-H-Naph.-A) 2H2O 1612.0 1321.6 521.5
Studies on metal chelates……………….. Chapter-3
67
Characterization of Ni (II) Schiff bases metal chelates 1. Solubility:
All Ni (II) Schiff bases metal chelates are insoluble in water and
common organic solvent like chloroform, benzene, ether, ethanol and
other organic solvents .it is soluble in DMF, DMSO
The chelates do not show clear melting point. It gets char at
temperature above 3100 C
2. Conductivity Measurements:
The conductance of Ni (II) Schiff bases metal chelates was
determined by the method as described on page 57. The result is
presented in Table -3.13. On page 69. The low conductivity conforms the
Nickel chelates are non-ionic in nature.
3. Molecular Weight Determination:
Because of the less solubility of the metal chelates under study in
common organic solvent the molecular weight of Ni (II) Schiff’s bases
chelates was determined by Rest’s Camphor method. The method as
described on page 57-58. The result is presented in Table -3.13 on page –
69.
4. Elemental Analysis:
This involved the estimation of nickel, Carbon, hydrogen and
nitrogen present in the Schiff base Ni (II) complex, Carbon, hydrogen and
nitrogen present in the complex was performed on a Vario EL-III analyzer.
For nickel estimation using the method as described on page 58.The result
is given in table-3.13. On page No. 69.
Studies on metal chelates……………….. Chapter-3
68
5. Absorption Spectra of Ni (II) Schiff’s base’s chelates:
The absorption Spectra of Ni (II) Schiff bases metal chelates were
taken using Simadzu 2401 spectrophotometer. The nature of the
absorption curves are shown in fig. 3.16 on page no.70. The results are
summarized in Table -3.14.On page 71.
6. IR SPECTRA
The infrared spectra of the Ni (II) Schiff bases metal chelates were
recorded using KBr discs on Perkin Elmer spectrophotometer
(PerkinElmer RX1) between 4000-400 cm-1. The IR spectra are
represented as in fig. 3.17 - 3.19.On page no.72-74. The results are
presented in table- 3.15 on page no.75.
Studies on metal chelates……………….. Chapter-3
69
TABLE – 3.13
PHYSICAL AND ELEMENTAL ANALYSIS OF Ni (II) METAL CHELATES
Sr. No.
Metal chelates
Molecular Formula
Molecular Weight (gm)
Collar Decomposition
temp o C.
Yield Conductivity mohs .cm2.mol-1
% Found(calculated)
% C
H
N
Metal
1 Ni(II)(L1-o-v-A)2H2O Ni(C34H36N2O6) 627.34 Green yellow
>310 63 6.3 65.04
(65.09)
5.74
(5.78)
4.40
(4.46)
9.31
(9.35)
2 Ni(II)(L2 -Sal -A)2H2O
Ni(C32H32N2O4) 567.29 Light green yellow
>325 61 7.6 67.69
(67.74) 5.66
(5.68) 4.90
(4.93) 10.32
(10.34)
3 Ni(II)( L3 -O-H-Naph.-A) 2H2O
Ni (C40H36N2O4)
667.40 Green yellow
>320 65 7.9 71.92
(71.98) 5.40
(5.43) 4.15
(4.19) 8.76
(8.79)
Studies on metal chelates……………….. Chapter-3
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FIG.3.16. ABSORPTION SPECTRA OF THE Ni (II) METAL CHELATES
Studies on metal chelates……………….. Chapter-3
71
TABLE – 3.14
Absorption Maximum (λ Max) of Ni (II) Schiff bases metal chelates.
Sr.No. Metal chelates λmax.(nm.)
1 Ni(II)( L1-o-v-A)2H2O
754.00
404.00
308.00
259.00
2 Ni(II)(L2 -Sal -A)2H2O
349.00
325.00
270.00
3 Ni(II)( L3 -O-H-Naph.-A) 2H2O
326.00
282.00
252.00
Studies on metal chelates……………….. Chapter-3
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Fig.3.17 IR SPECRA OF Ni (II) L1-o-v-A 2H2O
Studies on metal chelates……………….. Chapter-3
73
Fig.3.18 IR SPECRA OF Ni (II) L2 - Sal – A 2H2O
Studies on metal chelates……………….. Chapter-3
74
Fig. 3.19 IR SPECRA OF Ni (II) L3 -O-H-Naph.-A 2H2O
Studies on metal chelates……………….. Chapter-3
75
TABLE – 3.15
Infrared spectral data of the Ni (II) metal chelates
Compounds ν (C=N)cm-1
ν(C-O) cm-1
ν (M-N)cm-1
Ni(II)( L1-o-v-A )2H2O 1608.5 1440.7 543.0
Ni(II)(L2 –Sal A)2H2O 1615.1 1444.5 547.8
Ni(II)( L3 -O-H-Naph.-A ) 2H2O
1611.2 1327.1 519.5
Studies on metal chelates……………….. Chapter-3
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Characterization Of Co (II) Schiff bases metal chelates 1. Solubility:
All Co (II) Schiff bases metal chelates are insoluble in water and
common organic solvent like chloroform, benzene, ether, ethanol and
other organic solvents .it is soluble in DMF, DMSO
The chelates do not show clear melting point. It gets char at
temperature above 3000 C
2. Conductivity Measurements:
The conductance of Co (II) Schiff bases metal chelates was
determined by the method as described on page 57. The result is
presented in Table -3.16.On Page no. 78. The low conductivity conforms
the cobalt (II) chelates are non-ionic in nature.
3. Molecular Weight Determination:
Because of the less solubility of the metal chelates under study in
common organic solvent the molecular weight of Co (II) Schiff bases
chelates was determined by Rest’s Camphor method. The method as
described on page no. 57-58. The result is presented in Table -3.16.on
page no.78.
4. Elemental Analysis:
This involved the estimation of Cobalt, Carbon, nitrogen and
hydrogen present in the Schiff bases Co (II) complexes, Carbon, hydrogen
and nitrogen present in the complex was performed on a Vario EL-III
analyzer. For Cobalt estimation using the method as described on page
on.58.The result is given in Table–3.16. On page No. 78.
Studies on metal chelates……………….. Chapter-3
77
5. Absorption Spectra of Co (II) Schiff bases chelates:
The absorption Spectra of Co (II) Schiff bases metal chelates were
taken using Simadzu 2401 spectrophotometer. The nature of the
absorption curves are shown in fig.3.20 on page no.79.The results are
summarized in Table –3.17. On page 80.
6. IR SPECTRA
The infrared spectra of the Co (II) Schiff bases metal chelates were
recorded using KBr discs on Perkin Elmer spectrophotometer
(PerkinElmer RX1) between 4000-400 cm-1
. The IR spectra are
represented as in fig.3.21 – 3.23 on page no.81 -83. The results are
presented in table-3.18 on page no.84.
Studies on metal chelates……………….. Chapter-3
78
TABLE – 3.16.
PHYSICAL AND ELEMENTAL ANALYSIS OF Co (II) METAL CHELATES
Sr. No.
Metal chelates
Molecular Formula
Molecular Weight (gm)
Collar
Decomposition
temp o C.
Yield Conductivity mohs .cm2.mol-1
% Found(calculated)
% C
H
N
Metal
1 Co(II)( L1-o-v-
A)2H2O Co (C34H36N2O6) 627.56 orange >300 65 8.1
65.00 (65.06)
5.75
(5.78)
4.43
(4.46)
9.32
(9.39)
2 Co(II)(L2 -Sal –
A)2H2O Co (C32H32N2O4) 567.51
Brown orange
>315 62 5.9 67.68
(67.72) 5.63
(5.68) 4.90
(4.93) 10.35
(10.38)
3 Co (II)( L3 -O-H-Naph.-A) 2H2O
Co (C40H36N2O4) 667.62 Dark
orange >320 64 6.6
71.91 (71.95)
5.40 (5.43)
4.15 (4.19)
8.79 (8.82)
Studies on metal chelates……………….. Chapter-3
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FIG 3.20.ABSORPTION SPECTRA OF THE Co (II) METAL CHELATES
Studies on metal chelates……………….. Chapter-3
80
TABLE – 3.17
Absorption Maximum (λ Max) of Co (II) Schiff bases metal chelates.
Sr.No. Metal chelates λmax.(nm.)
1 Co (II)( L1-o-v-A)2H2O
505.00
314.00
255.00
2 Co (II)(L2 -Sal -A)2H2O
561.00
302.50
256.00
3 Co (II)( L3 -O-H-Naph.-A) 2H2O
538.00
303.00
257.00
Studies on metal chelates……………….. Chapter-3
81
Fig.3.21 IR SPECRA OF Co (II) L1-o-v-A 2H2O
Studies on metal chelates……………….. Chapter-3
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Fig.3.22 IR SPECTRA OF Co (II) L2 - Sal – A 2H2O
Studies on metal chelates……………….. Chapter-3
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Fig.3.23 IR SPECRA OF Co (II) L3 -O-H-Naph.-A 2H2O
Studies on metal chelates……………….. Chapter-3
84
TABLE – 3.18
Infrared spectral data of the Co (II) metal chelates
Metal chelates
ν (C=N)cm
-1 ν(C-O) cm
-1 ν (M-N)cm
-1
Co(II)( L1-o-v-A )2H2O 1614.5 1445.4 501.2
Co (II)(L2 –Sal A)2H2O 1608.8 1436.0 500.8
Co(II)(L3 -O-H Naph.-A) 2H2O 1612.2 1329.0 515.2
Studies on metal chelates……………….. Chapter-3
85
Characterization of Zn (II) Schiff bases metal chelates 1. Solubility:
All Zn (II) Schiff bases metal chelates are insoluble in water and common
organic solvent like chloroform, benzene, ether, ethanol and other organic solvents
.it is soluble in DMF, DMSO
The chelates do not show clear melting point. It gets char at temperature
above 3000 C
2. Conductivity Measurements:
The conductance of Zn (II) Schiff bases metal chelates was determined by
the method as described on page no.57.The result is presented in Table -3.19 on
page no.87.The low conductivity conforms the Nickel chelates are non-ionic in
nature.
3. Molecular Weight Determination:
Because of the less solubility of the metal chelates under study in common
organic solvent the molecular weight of Zn (II) Schiff bases chelates was determined
by Rest’s Camphor method. The method as described on page no.57-58.The result
is presented in Table -3.19.On pageno.87.
4. Elemental Analysis:
This involved the estimation of Zinc, Carbon, nitrogen and hydrogen present
in the Schiff base Zn (II) complex. Carbon, hydrogen and nitrogen present in the
complex were performed on a Vario EL-III analyzer. For Zinc estimation using the
method as described on page 58.The result is given in Table –3.19 on pages No.87.
Studies on metal chelates……………….. Chapter-3
86
5. Absorption Spectra of Zn (II) Schiff bases chelates:
The absorption Spectra of Zn (II) Schiff bases metal chelates were taken
using Simadzu 2401 spectrophotometer. The natures of the absorption curves are
shown in fig. 3.24 on page no. 88.The results are summarized in Table –3.20 on
page -89.
6. IR SPECTRA
The infrared spectra of the Zn (II) Schiff bases metal chelates were recorded
using KBr discs on Perkin Elmer spectrophotometer (PerkinElmer RX1) between
4000-400 cm-1
. The IR spectra are represented as in fig. 3.25-3.27 on pages 90 - 92.
The results are presented in Table-3.21 on page no.93.
Studies on metal chelates……………….. Chapter-3
87
TABLE – 3.19
PHYSICAL AND ELEMENTAL ANALYSIS OF Zn (II) METAL CHELATES
sr.
No.
Metal chelates
Molecular Formula
Molecular Weight (gm)
Collar
Decomposition
temp o C.
Yield Conductivity mohs .cm2.mol-1
% Found(calculated)
% C H N Metal
1 Zn(II)( L1-o-v-A)2H2O Zn(C34H36N2O6) 634.00 Yellow >315 62 2.9 64.36
(64.40)
5.69 (5.72)
4.38
(4.41)
10.27
(10.31)
2 Zn (II)(L2-Sal–A)2H2O Zn(C32H32N2O4) 573.95 Light
yellow >310 61 7.1
66.91 (66.96)
5.58 (5.61)
4.83 (4.88)
11.35 (11.38)
3 Zn (II)(L3 -O-H-Naph.-A) 2H2O
Zn(C40H36N2O4) 674.06 Light
yellow >325 60 4.6
71.22 (71.26)
5.35 (5.38)
4.11 (4.15)
9.65 (9.69)
Studies on metal chelates……………….. Chapter-3
88
FIG. 3.24 ABSORPTION SPECTRA OF THE Zn (II) METAL CHELATES
Studies on metal chelates……………….. Chapter-3
89
Table – 3.20
Absorption Maximum (λ Max) of Zn (II) Schiff bases metal chelates.
Sr.No. Metal chelates λmax.(nm.)
1 Zn(II)( L1-o-v-A)2H2O
414.00
325.00
258.00
2 Zn(II)(L2 -Sal A)2H2O
347.00
271.00
3 Zn(II)(L3 -O-H-Naph.-A) 2H2O
325.00
281.50
251.00
Studies on metal chelates……………….. Chapter-3
90
Fig. 3.25 IR SPECRA OF Zn (II) L1-o-v-A. 2H2O
Studies on metal chelates……………….. Chapter-3
91
Fig.3.26 IR SPECRA OF Zn (II) (L2 - Sal – A) 2H2O
Studies on metal chelates……………….. Chapter-3
92
Fig.3.27 IR SPECRA OF Zn (II) (L3 -O-H-Naph.-A) 2H2O
Studies on metal chelates……………….. Chapter-3
93
Table – 3.21
Infrared spectral data of the Zn (II) metal chelates
Compounds ν (C=N)cm-1
ν(C-O) cm-1
ν (M-N)cm-1
Zn(II)( L1-o-v-A )2H2O 1614.3 1459.3 570.3
Zn (II)(L2 –Sal A)2H2O 1610.2 1453.9 576.6
Zn(II)(L3 -O-H Naph.-A) 2H2O
1611.0 1392.1 571.0
Studies on metal chelates……………….. Chapter-3
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References:
1. V.M. Parikh; “absorption spectroscopy of organic Molecule” .Addition-
Wesley Pub. Co. London,243-256(1978)
2. C. N. R. Rao; “chemical application of infrared spectroscopy” Academic
press, New York (1963).
3. Silverstein Bassler and Morrill; spectrometric identification of organic
compounds 5th edn. By john wiely & sons Inc.(1991).
4. Vogel A. I.; “Quantitative Inorganic Analysis”, Longamans Green,
London, (1961).
5. Schwarzenbach G. “complexomeric titration” Intersciences, New York,
76, (1960).
Studies on metal chelates……………….. Chapter-4
95
General
Le Chatelier 1, 2 was the first to use thermal transformation of materials
as an analytical tool. He applied this technique to analyze the clay materials.
A number of investigators have obtained kinetic information from DTA
measurements3, 4. Murray and white 5 reported that the thermal decomposition
of clay followed a first order law. Kissinger 6 studied the variation of peak
temperature with heating rate in DTA. The application of DTA to organic
material offers considerable potential to the study of thermal properties, which
are important from both scientific and practical point of view.
Still 7has classified the thermal method of analysis into different
categories depending on change in weight, in dimension and those involving
evolved volatiles. The techniques based on energy changes are DTA and
DSC. Those depending on weight change are TGA and isobaric and
isothermal weight change. Differential and derivative dilatometry are the
example of techniques base on dimensional changes where as the
techniques depending upon the evolved volatiles are evolved gas detection
(EGD) and evolved gas analysis(EGA).the parameters measured as a
function of temperature in DTA , TGA, DSC. Physical transformation such as
melting, freezing, volatilization, glass transformation, crystallization from
melts, etc., can be studies by DTA and DSC.
Chemical transformation 8can is studies by DTA and TGA. In DTA
technique, difference in temperature between a substance and reference
materials is recorded against either temperature or time as the two specimens
are subjected to identical temperature regimes in an environment heated or
cooled at a controlled heating rate. Any transition, which a sample undergoes,
will result in absorption or liberation of energy by the sample with a
corresponding deviation of its temperature from that of the reference. In DTA,
when at a particular temperature, sample change its physical or chemical
state, the differential signal appears as a peak. The numbers, position, shape
and nature (exothermic or endothermic) of peak gives information about
Studies on metal chelates……………….. Chapter-4
96
melting crystallization, glass transition temperature, crystalline rearrangement,
decomposition of the compound,etc9
Thermal analysis is defined as a group of methods based on the
determination of changes in chemical or physical properties of material as a
function of temperature in a controlled atmosphere. Thermo gravimetric
analysis (TGA), measures weight loss or gain. There are three types of
thermogravimetry: static or isothermal thermogravimetry, Quasistatic
thermogravimetry and dynamic thermogravimetry .generally dynamic
thermogravimetry is used. In this technique, the sample start losing weight at
a very slow rate up to a particular temperature and then the rate of weight loss
become large over a narrow range of temperature. After this temperature, the
loss in weight levels off. TG curves are characteristic for a given compound
because of unique sequence of physicochemical reaction which occurs over
definite temperature range and at rates that are a function of molecular
structure. The changes in weight are due to rupture and /or formation of
various physical and chemical changes which lead to the evolution of volatile
products or the formation of heavier reaction products10
TGA monitors weight change in material as a function of temperature
(or time) under a controlled atmosphere. This allows measurement of the
thermal stability and composition of a material through. Determination of the
reaction temperature involving weight changes. Such reaction includes
dehydration, solvent /volatile removal, oxidation and decomposition. There are
three types of thermogravimetry: static or isothermal thermogravimetry,
quasistatic thermogravimetry and dynamic thermogravimetry. Generally
dynamic thermogravimetry is used. In this
TGA is routinely used in all phases of research, quality control and
production operations. For example of TGA trace of calcium carbonate
(CaCO3) to 1000oC showing a mass loss of 44% around 850oC.This mass
loss may be associated with the removal of CO2 to form CaO.
In thermogravimatric analysis, a small but accurately known sample
mass (typical about 100 milligrams) is heated in a crucible on an analytical
Studies on metal chelates……………….. Chapter-4
97
balance during controlled heating. An inert reference material treated
simultaneously ensures that any drift of the instrument can be corrected for. In
general several gases – atmospheres (e.g. air, N2, CO2) can be chosen. Any
difference of weight of the sample (loss or gain) is recorded verses
temperature during controlled heating. This may be related to reaction(s)
taking place in a sample, (such as oxidation, reduction, dehydration etc.). The
technique is suited for many solid materials, although limitation may arise with
respect to possible reactions with the crucible, or corrosive gases emitted by
the sample.
Thermal analysis is a good analytical tool to measure:-
• Thermal decomposition of solids and liquids
• Solid-solid and solid-gas chemical reactions
• Material specification, purity and identification
• Inorganic solid material absorption
• Phase transitions.
• Elastomers
- Evolution possibilities for the glass transition
- Influence of sample pretreatment on the glass transition
- Expansion coefficient of silicone elastomers
- Comparison of different possibilities for evaluating the glass
transition
- Glass transition of vulcanized and unvulcanized silicone
elastomers
- Analysis of carbon black in SBR elastomers with different
degrees of cross-linking
- Analysis of carbon black in elastomers based on chloroprene
Studies on metal chelates……………….. Chapter-4
98
- TGA of silicone elastomers
- Identification of BR and NBR using a TGA – FTIR combination
- TGA of elastomers containing SBR as one constituent
- Analysis of a CR/ NBR blend by TGA
- Combined TGA and DSC analysis of an EPDM/SBR blend
- Temperature – dependent DMA measurements of an unfilled
SBR/NR elastomer
• Pharmaceutical
The potential applications of thermal analysis in the
pharmaceutical industries are numerous on account of the different
chemical – physical aspects of investigations. Amongst others these
include method development, characterization and specification of
active and inactive ingredients, safety analysis or routing analysis in
quality control and stability studies.
- Melting behavior and decomposition
- DSC fingerprint
- Purity using DSC and HPLC
- Solvent detection by means of TG-MS, Pharmaceutical active
substance
- Quantification
• Thermoplastics
• Food
- TGA of sugar and starch
- DSC of amorphous sugar
Studies on metal chelates……………….. Chapter-4
99
- Influence of pH on bovine Hemoglobin
- DSC of meat
• Evolved gas analysis
- Decomposition of acetylsalicylic acid
- Detection pf residual solvents in a pharmaceutical substance
- Decomposition of copper sulfate pentahydrate
- Detection of methyl salicylate in sample of rubber
Base on this information, one can characterize polymers, organic or
inorganic chemical, metal, semiconductors and other common classes of
materials.
Analysis of water molecules from thermal decomposition:
The Thermogrvimetric analysis data provide important experimental evidence
in determining the number of water molecules present in the Schiff base metal
chelates. Generally, the loss of lattice water will be at a lower temperature
than that of the coordinated water 11.According to Patel et. al12 Coordinated
water molecules were evaluated by considering the residue loss at 150-200oC
and lattice water molecules were evaluated by considering weight loss at 100
– 110oC. Analytical data of the chelates support the formulations proposed
after evaluation of water molecule.
Literature survey
Khare et al 13 have studied thermal decomposition of ammonium
interacted dcolite; which shows a remarkable exchange capacity with NH4+ion
which replaces 80.71% of Na2O. they observed dehydration, deammoniation
and dehydroxylation processes during thermal treatment of this derivative
thermal studies on some chelate polymers were carried out by Aswer et al 14
and depicted that the decomposition temperature of the polychelates
decrease in the order Ni > Mn > Cu > Co > Zn and concluded that the reaction
Studies on metal chelates……………….. Chapter-4
100
of decomposition of poly chelates can be classed as a slow reaction.
Upadhyaya et al 15 studied the thermal decomposition of praseodymium and
neodymium myrisates both as a function of temperature and time. The
thermogrvimetric analysis has show that order of decomposition reaction is
kinetically of zero order and the energy of activation for the decomposition
process lies in the range of 10-15 kcal/ mole. Thermal behavior of some
organotin IV) semicarbazone and thiosemicarbazone complexes were studied
by Nath et al 16 .Patel et al 17 prepared some solid complexes of α –
oximinoacetoacet – O / P chloroanilide – β thiosemicarbazone with metal their
characteristic with thermogrvimetric analysis revels that the rate of reaction for
the metal chelates decomposition is faster then the ligand and the metal
chelates follow a single step decomposition. Fluorenone antthranilic acid
complexes of Mn (II), Co (II), and Ni (II) were synthesized by Thomas et al 18.
Thermal studies of dioxouranium (VI) sulphato complexes of some Schiff base
of 4-aminoantipyrine was studied by Agarwal 19 and reported that the TG
curves of these complexes do not show the presence of water molecule either
n or out of the coordination sphere. The thermal analysis of Fe(II) , Ni (II) and
Cu (II) complexes with 1,3,5 – trimethylhexahydrotrizine and 1,4,7-
triazacyclononane were studied by TG and DTA techniques by Belal 20 and
reported their relative thermal stability. Ali et al 21 studied the thermal behavior
of the adduct of 8- hydroxyquionoline and determined the kinetic parameters
such as order of reaction and activation energy, using TG curves. Thermal
decomposition of palladium complexes with triphenylphosphine were studied
by Baobieri et al 22 where as thermal degradation of palladium – di – thioester
systems up to 10000C and their intermediates were studies by Faraglia et al 23
the kinetic properties and thermal stability of chlorinated complexes of Co(II)
and Ni (II) with 3-hydroxypyridine were studied in a N2 atm. Using TGA, DTG
and DSC methods by Halawani 24. Thermal behavior of some divalent
transition metal complexes of triethanolamine was examined by Icbudak et
al25 and by using the initial decomposition temperature the sequence of
thermal stability was found to be Mn(II)> Fe(II) > Ni (II)>Zn(II)>Cu(II). Kinetic
parameters and the reaction between thermal stability and chemical structure
of the complexes also been discussed. In case of some isodithiobivert
Studies on metal chelates……………….. Chapter-4
101
complexes thermal pattern was used to predict the attachment of metal ion
with sulfur. In this case due to sulfur environment around the metal ion the
formation of metal sulphate or metal were made on the basis of change in
weight of respective residues. Omar, M.; Mohamed, G. et.al.26 examine the
thermal behavior of Transition metal complexes of heterocyclic Schiff base is
studied and the activation thermodynamic parameters are calculated using
Coats-Redfern method. Synthesis, spectral and thermal degradation kinetics
of divalent cadmium complexes studies by Bhojya Naik et.al27.
Discussion
A Representative Thermogram of Cu (II), Co(II), Ni(II) and Zn(II)
chelates is given in fig 4.1 – 4.4, it is found from the TGA that the heating
rates were suitably controlled at 10 o C/min under nitrogen atmosphere and
weight loss was measured from temperature range of 50-800 o C.
Thermogram of metal chelates indicates small weight loss in 60oC to 80oC
which is assigned to loss of lattice water, it has been observed that the Schiff
base metal chelates show a loss in weight corresponding to decomposition of
partial organic ligand with two water molecules is coordinated to the metal ion
in the temperature range 110 oC to 295 oC 28-31. And the gradual weight loss
in the temperature range 295oC - 700oC or 800oC, can be assigned to
complete decomposition of ligand moiety around metal ion. In all cases, the
final products are metal oxides. In all cases, these results are in good
accordance with the proposed Schiff base metal chelates composition. The
Thermal analysis data are collected in table 4.1. On page 102.
Studies on metal chelates……………….. Chapter-4
102
Table -4.1
Thermogravimetric Data
Sr.No. Metal chelates % Loss in weight
Temp. 0C Found (calcd.)
1 Cu(II)( L1-o-v-A)2H2O 5.65(5.69)a 110-290
87.39(87.41)b 290-800
2 Cu(II)( L2 - Sal – A)2H2O 6.27(6.29)a 110-290
86.02(86.09)b 290-700
3 Cu(II)(L3 -O-H-Naph.-A) 2H2O
5.33(5.35)a 110-275
88.11(88.16)b 275-700
4 Ni(II)( L1-o-v-A)2H2O 5.89(5.92)a 115-190
87.66(87.69)b 190-800
5 Ni(II)(L2 -Sal -A)2H2O
6.30(6.34)a 110-190
86.79(86.83)b 190-800
6 Ni(II)( L3 -O-H-Naph.-A) 2H2O
5.35(5.39)a 110-180
88.75(88.80)b 180-800
7 Co(II)(L1-o-v-A)2H2O 5.88(5.92)a 110-275
87.62(87.66)b 275-700
8 Co(II)(L2 -Sal –A)2H2O 6.30(6.34)a 110-285
86.76(86.79)b 285-700
9 Co (II)(L3 -O-H-Naph.-A) 2H2O
5.33(5.39)a 110-290
88.78(88.83)b 290-700
10 Zn(II)(L1-o-v-A)2H2O 5.82(5.86)a 110-295
86.71(86.74)b 295-700
11 Zn (II)(L2 -Sal –A)2H2O 6.22(6.27)a 110-290
85.78(85.82)b 290-700
12 Zn (II)(L3 -O-H-Naph.-A) 2H2O
5.31(5.34)a 110-285
87.90(87.92)b 285-700
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Fig. 4.1 Thermogram of [Cu (II) ( L2 -Sal –A- 2H2O) ]
Studies on metal chelates……………….. Chapter-4
104
Fig. 4.2 Thermogram of [Co (II) (L1-o-v-A - 2H2O) ]
Studies on metal chelates……………….. Chapter-4
105
Fig. 4.3 Thermogram of [Ni (II) (L3–O-Naph.-A- 2H2O) ]
Studies on metal chelates……………….. Chapter-4
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Fig. 4.4 Thermogram of [ Zn(II) ( L2 Sal –A- 2H2O) ]
Studies on metal chelates……………….. Chapter-4
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References:
1. H. Le Chatelier, Bull. Soc. Franc. Mineral, 10, 204 (1887).
2. H. Le Chatelier, Z Physik. Chem.., 1,396 (1987).
3. P.Murray and J. White, Clay Mineral Bull., 2, 255 (1955).
4. P.Baumgartner and P.Duhaut, Bull.Soc.Chem. france, 1187 (1960).
5. P.Murray and J. White, Trans. Brit. Ceram. Soc., 48, 187 (1949).
6. H. E. Kissinger, J.Res. Natl. bur. Std., 57, 217 (1956).
7. R.H. Still, British Polymer, L., 11, 101 (1979).
8. E.Heisenberg, Cllulose Chemie, 12,159 (1931).CA, 25, 59823(1931).
9. G.Chatwal and S. anand “instrumental Methods of Chemical Analysis”
Second Edition (1984).
10. H.H. Willard, L.L. Merritt, Jr, J. A. Dean and F. A. Settle,
Jr.,"Instrumental Methods of Analysis” Sixth Edition (1986).
11. Joshi, R. A.: J. Chem. Soc. 21, 259, (1994).
12. Patel P.S., Patel M. M. J. Ind. Chem. Soc. 72, 149 (1999).
13. Khare A. S. Banerjee S.P. J. Ind. Chem. Soc. 68 353 (1991).
14. Aswer A. S., Munshi K. N.Ind. Chem. Soc. 69,544 (1992).
15. Upadhyaya S.K., Sharma S.P., J. Ind. Chem. Soc. 70, 753 (1993)
16. Nath M., Sharma N., J. Ind. Chem. Soc. 72,115 (1995).
17. Patel P.S., Patel M. M. J. Ind. Chem. Soc. 72, 149 (1995).
18. Thomas J. K., Parameshwaran, G. J. Ind. Chem. Soc. 72,155 (1995).
19. Agarwal R. K. J. Ind. Chem. Soc. 72, 263 (1995).
20. Belal A.A.M. Asian Sci. Tech.Bult. 15,59, (1994).
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21. Ali, S.I., Ansari, A.M.A., Pundhir,N.K.S. Inorg. Bio.-Inorg. Phys.Theor.
Anal. Chem. 34A (6), 423, (1995).
22. Barbieri R.S., Belatto C.R., Massabni A.C. J.Therm.Anal. 44(A), 903
(1995).
23. Farsglia G., Longo D., Cherchi V., Sitran S. Polyhedron 14, 1905
(1995).
24. Halawani K. H. Thermochim Acta 256(2), 359 (1995).
25. Icbudak H., Yilmaz V.T. Oelmez H., J. Therm. Anal. 44(3), 605(1995).
26. Omar M., Mohamed G., Hindy A. J. Of Thermal Anly. And Calorimetry
86(2) ,315-325 (2006).
27. Halehatty S. Bhojya Naik, R. Chetana, D. Revanasiddappa,Turk J.
Chem. 26,565-572(2002)
28. Icbudak H., Yilmaz V.T. Oelmez H., J. Therm. Anal. 53, 843(1998).
29. Issar,Y.M., Abdel Latif S. A., Abu-El-Wafa S. M., Abdel – Salam H.A.
Synth.Reac.Inorg.Met.-Org. Chem.,29(1), 53 (1999).
30. Tumer M. Ko¨ksal H., Sertn S. Synth.Reac.Inorg.Met.-Org. Chem.
27(5), 775 (1997).
31. Nakamoto K. Lattice water and aqua and hydroxo complexes in
infrared and raman spectra of Inorganic and coordination compounds
.4TH Edn.,John wiley and sons, ine., 227.1986.
Studies on metal chelates……………….. Chapter-5
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General
Materials may be classified by their response to externally applied
magnetic fields as diamagnetic, paramagnetic, or ferromagnetic, these
magnetic responses differ greatly in strength. Diamagnetic is a property of all
materials and opposes applied magnetic fields, but is very weak.
Paramagnetism, when present, is stronger than diamagnetism and produces
magnetization in the direction of the applied field, and proportional to the
applied field. Ferromagnetic effects are very large; producing magnetizations
sometimes orders of magnitude greater than the applied field and as such are
much larger than either diamagnetic or paramagnetic effects.
The magnetization of material is expressed in terms of density of net
magnetic dipole moments µ in the material. The magnetization (M) is given by
M = µ total / V
Then the total magnetic field B in the material is given by
B = B0 +µ0M
Where µ0 is the magnetic permeability of space and B0 is the externally
applied magnetic field. When magnetic field inside of materials are calculated
using Ampere’s law or the Biot- Savart law, then the µ0 in those equations is
typically replaced by just µ with the definition
µ = Km µ0
Where Km is called the relative permeability. If material dose not
respond to the external magnetic field by producing any magnetization, then
Km = 1. Another commonly used magnetic quantity is the magnetic
Susceptibility which specifies how much the relative permeability differs from
one. Magnetic susceptibility χ m = Km – 1
For paramagnetic and diamagnetic materials the relative permeability
is very close to 1 and the magnetic susceptibility very close to zero. For
ferromagnetic materials, these quantities may be very large.
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Another way to deal with the magnetic field which arise from
magnetization of materials is to introduce a quantity called magnetic field
strength H. it can be defined by the relationship and has the value of
H = B0 / µ0 = B / µ0 – M
Unambiguously designating the driving magnetic influence from
external currents in a material, independent of the material’s magnetic
response. The relationship for B above can be written in the equivalent from
B = µ0 (H + M)
H and M will have the same units, amperes / meter.
Types of magnetic behavior
(a) Diamagnetism :
Diamagnetism was discovered and named in 1845 by Michael
Faraday.
The orbital motion of electrons creates tiny atomic current loops, which
produce magnetic fields. When an external magnetic field is applied to a
material, these current loops will tend to align in such a way as to oppose the
applied field. This may be viewed as atomic version of Lenz’s law: induced
magnetic field tend to oppose the change which created them. Materials in
which this effect is the only magnetic response are called them. Materials in
which this effect is the only magnetic response are called diamagnetic. All
materials are inherently diamagnetic, but if the atoms have some net
magnetic moment as in paramagnetic materials, or if there is long- range
ordering of atomic magnetic moments as in ferromagnetic materials, these
stronger effects are always dominant.
Diamagnetic is the residual magnetic behavior when materials are
neither paramagnetic nor ferromagnetic.
Diamagnetic is a very weak from of magnetism that is only exhibited in the
presence of an external magnetic field. It is the result of change in the orbital
Studies on metal chelates……………….. Chapter-5
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motion of electrons due to the external magnetic field. The induced magnetic
moment is very small and in a direction opposite to that of the applied field.
When placed between the poles of a strong electromagnet, diamagnetic
materials are attracted towards regions where the magnetic field is weak.
Diamagnetism is found in all materials; however, because it is so weak it can
only be observed in materials that do not exhibit other forms of magnetism.
Also, diamagnetism is found in element with unpaired electrons. Oxygen was
once thought to be diamagnetic, but a new revised molecular orbital (MO)
model confirmed oxygen’s paramagnetic nature.
An exception to the weak nature of diamagnetism occurs with the rather
large number of materials that become superconducting, something that
usually happens at lowered temperature. Superconducting, something that
usually happens at lowered temperatures. Superconductors are perfect
diamagnets and when placed in an external magnetic field expel the field line
from their interiors (depending on field intensity and temperature).
Superconductors also have zero electrical resistance, a consequence of their
diamagnetism. Superconducting structures have been known to tear
themselves apart with astonishing force in their attempt to escape an external
field. Superconducting magnets are the major component of most magnetic
response imaging system, perhaps the only important application of
diamagnetism.
A thin slice of pyrolitic graphite, which is an unusually strongly diamagnetic
material, can be stably floated on a magnetic field, such as that from rare
earth permanent magnets. This can be done with all components at room
temperature, making a visually effective demonstration of diamagnetism.
Diamagnetic materials have a relative magnetic permeability that is less than
1, and a magnetic susceptibility that is less than 0.
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(a) Para magnetism:
Some materials exhibit a magnetization which is proportional to the
applied magnetic field in which the material is placed. These materials are
said to be paramagnetic.
Paramagnetism is the tendency of the atomic magnetic dipoles, due to
quantum – mechanical spin, in a material that is otherwise non – magnetic to
align with an external magnetic field. This alignment of the atomic dipoles with
the magnetic permeability greater than unity (or, equivalently, a small positive
magnetic susceptibility).
In pure Paramagnetism, the field acts on each atomic dipole
independently and there are no interactions between individual atomic
dipoles. Such paramagnetic behavior can also be observed in ferromagnetic
materials that are above their curie temperature.
Paramagnetic materials attract and repel like normal magnets when
subject to a magnetic field. Under relatively low magnetic field saturation
when the majority of the atomic dipoles are not aligned with the field,
paramagnetic materials exhibit magnetization according to curie’s law.
M = C (B / T)
Where , M is the resulting magnetization, B is the magnetic flux density
of the applied field, T is absolute temperature (Kelvin), C is a material specific
curie constant.
This law indicates that paramagnetic materials tend to become
increasingly magnetic as the applied magnetic field is increased, but less
magnetic as temperature is increased. Curie’s law is incomplete because it
fail to predict what will happen when most of the little magnets are aligned
(after everything is aligned, increasing the external field will not increase the
total magnetization) so curie’s constant really should be expressed as function
of how much of the material is already aligned.
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Paramagnetic materials in magnetic fields will act like magnets but
when the field is removed, thermal motion will quickly disrupt the magnetic
alignment. In general paramagnetic effects are small (magnetic susceptibility
of the order of 10-3 to 10-5). Ferromagnetic materials above the Curie
temperature become paramagnetic.
(c) Ferromagnetism:
Ferromagnetism is phenomenon by which a material can exhibit a
spontaneous magnetization, and is one of the strongest forms of magnetism.
It is responsible for most of magnetic behavior encountered in everyday life,
and is the basis for all permanent magnets. These are a number of crystalline
materials hat exhibit ferromagnetism.
One can also make amorphous ferromagnetic metallic alloys by very
rapid quenching of liquid alloy. These have the advantage that their properties
are nearly isotropic. This results in low coercivitty, low hysteresis loss, high
permeability, and high electrical resistivity. A typical such material is a
transition metal – metalloid alloy, made from about 80% transition metal
(usually Fe, Co, or Ni) and a metalloid component ( B, C, SI, P, or Al) that
lowers the melting point.
(d) Antiferromagnetism:
In materials that exhibit Antiferromagnetism, the spins of magnetic
electrons align in a regular pattern with neighbouring spins pointing in
opposite directions. This is the opposite of ferromagnetism. Generally,
antiferromagnetic materials exhibit Antiferromagnetism at a low temperature,
and become disordered above a certain temperature. The transition
temperature is called the Neel temperature. Above the Neel temperature the
material is typically paramagnetic. The magnetic susceptibility of an
antiferromagnetic material will appear to go through a maximum as the
temperature is lowered; in contrast, that of a paramagnet will continually
increase with decreasing temperature. Antiferromagnetic materials have a
negative coupling between adjacent moment and low frustration.
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Antiferromagnetic materials are relatively uncommon. An example is the
heavy – fermion superconductor URu2Si2
Magnetic susceptibility measurements:
The Vibration Sample Magnetometer (VSM), model 7304, Lake shore
Cryotronics, Inc., U.S.A., was used to characterize magnetic properties of the
metal chelates. The Model 7304 is capable of characterizing a verity of
particulate and continuous magnetic media materials including; audio, video
and digital data tapes, flexible media, magneto – optical materials, sputtered
and plated thin film materials including multilayer GMR,CMR, exchange- bias
and spin valve materials. In addition to standard major and minor hysteresis
loop measurements, the lake shore Model 7304 also measure remanence
curves, and facilities investigation of anisotropic materials with a vector option.
Permanent magnet materials including rare – earth magnets (NdFeB, SmCo,
etc), polymer – bonded magnets, electrical steel, iron oxides (ferrites) etc. are
also readily characterized in Model 7304. In addition to all full loop properties,
2nd quadrant characteristics may be measured, energy products determined.
Curie point determinations with an optional furnace are also possible. The
Model 7304 is also ideally suited for basic measurements over a broad range
of magnetic fields and temperatures employing optional cryostats and liquids
are all readily accommodated. Materials that may be characterized include;
multilayer films, high and low temperature superconductors, molecular
magnets, rare –earth and transition metal materials, spinglsses, amorphous
magnets, and more. It measures the magnetic moment of any magnetic
material in any form, from 5 x 10-6 emu to 1 x 103 emu. A description and
theory are as follows:
When a sample material is placed in a uniform magnetic field, a dipole
moment proportional to the product of the sample susceptibility times the
applied field is induced in the sample. A sample undergoing sinusoidal motion
as well induced an electrical signal in suitable located stationary pick up coils.
This signal, which is at the vibration frequency, is proportional to the magnetic
moment, vibration amplitude, and vibration frequency. The material under
Studies on metal chelates……………….. Chapter-5
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study is contained in a sample holder, which is centered in the region between
the pole pieces of magnet. A slender vertical sample rod connects the sample
holder with a transducer assembly located above the magnet, which supports
the transducer assembly with sturdy, adjustable supports rods. The
transducer converts a sinusoidal AC drive signal, provided by a circuit located
in the console, into a sinusoidal vertical of the sample rod and the sample is
thus made to undergo a sinusoidal motion in a uniform magnetic field. Coil
mounted on the pole pieces of the magnet pick up the signal resulting from
the sample motion. This AC signal at the vibration frequency is proportional to
the magnitude of the moment induced in the sample. However, it is also
proportional to the vibration amplitude and frequency. The constancy
maintained in the drive amplitude and frequency is so that the output
accurately tracks the moment level without degradation due to variation in the
amplitude and frequency of vibration.
This technique depends on being able to use a vibrating capacitor
located beneath the transducer to generate an AC control signal that varies
solely with the vibration amplitude and frequency. The signal, which is at the
vibration frequency, is fed back to the oscillator where it functions as the
reference drive signal. The signal from the sample is developed in the pickup
coils, then buffered, amplified, and applied to the demodulator. There it is
synchronously demodulated with respect to the reference signal derived from
the moving capacitor assembly. The resulting DC output is an analog of the
moment magnitude alone, uninfluenced by vibration amplitude change and
frequency drift.
The moment calibration of Vibrating Sample Magnetometer is
traditionally performed with a nickel standard at an applied field above the
saturation field of nickel, normally 5000Oe. Lake shore supplies a nickel
cylinder of 99.99 % purity, an aspect ratio of nearly 1: 1 and a mass of
approximately 0.02 grams. These samples are etched and weighted prior to
measuring their saturation magnetization. The saturation magnetization of the
nickel sample is measured with a VSM calibrated with a NIST (NBS) nickel
Studies on metal chelates……………….. Chapter-5
116
standard. There fore, calibration on a single range ensures the overall
calibration of the electronics.
Lake shore performs moment- offset calibration. Additional moment
offset adjustments should not be required, but lake shore allows for software
offset correction to the moment readings. Lake shore calibrates both the gain
and the offset of the measurement / control loop to specification accuracy
during final assembly and testing.
The VSM report the total magnetic moment, m, of a sample in emu.
However, the end gole of the magnetic measurement is not the moment in
emu, but to get the effective magnetic moment, µ eff. Therefore, the VSM
magnetic moment can be converted to susceptibility of a sample has units of
volume and is defined for paramagnetic materials by the equation:
χ (cm3) = m (emu)/ H (Oersted).
The gram susceptibility, χ g was calculated using the expression:
Gram susceptibility: χ g = χ (cm3)/mass
The gram susceptibility was multiplied by the molecular weight of the
sample to obtain molar susceptibility, χ m. . A correction was applied for the
diamagnetism of the ligands to get the correction molar susceptibility χ m’. The
effective magnetic moment µ eff was calculated from the expression:
µ eff. = 2.84 (χ m’ x T) 1/2
Where T = absolute temperature (K)
Magnetic susceptibility of the copper (II) Schiff base chelates.
The Cu (II) ion has [Ar] 3d9 electronic configuration and its compounds
are expected to have magnetic moment close to be spin – only value
1.73B.M. This ion has one unpaired electron whatever the geometry
octahedral, plane or tetrahedral.
Studies on metal chelates……………….. Chapter-5
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The single-ion magnetic properties of copper (II) are fairly
straightforward. Spin – orbit coupling is large, causing the g values to lie in the
range 2.0 to 2.3, but because copper has an electronic spin of only ½, there is
no zero – field splitting effects. The g values are often slightly anisotropic,
being for example 2.223(║) and 2.051 (┴) in Cu (NH3) SO4 .H2O.The one
problem that dose arise with this ion is that it rarely occupied a site of high
symmetry; in octahedral complexes ,two trans ligands are frequently found
substantially further from the metal than the remaining four. This has led to
many investigation of copper as the Jahn – Teller susceptible ion, per
excellence. Dynamic Jahn - teller effects have also been frequently reported
in EPR investigations of copper compounds at low temperatures. Tetrahedral
copper is also well-known, through it usually quite distorted because of the
Jahn – Teller effect. It is found, for example, in Cs2CuCl4, a system with an
average g-value of 2.20.
The magnetic moment of Cu (II) ion in octahedral or planar
stereochemistry generally lies around 1.98 B.M. at room temperature. In
absence of magnetic exchange between neighbouring copper ions, Curie’s
law is obeyed. For tetragonal coordinated Cu (II) ion with 2T2g ground term, the
anticipated magnetic moment is 2.2B.M. At room temperature, some literature
magnetic moment data of the Cu (II) complexes are summarized as following
table 5.1.
Studies on metal chelates……………….. Chapter-5
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Table – 5.1 Literature magnetic moment data of the Cu (II) complexes
No. Complexes µ eff. (B.M.) Geometry Reference
1 [Cu(L’)(NO3)2] 1.80 Tetrahedral 15
2 [Cu(L’)2] 1.99 Square
planer 16
3 [Cu(Sal)2acphen]H2O 1.71 Octahedral 17
4 [Cu(5-Clsal)((bzal)] 2.18 Tetrahedral 14
5 [CuL2](ClO4)2H2O 1.55 Tetrahedral 8
6 [Cu(SB-Cl)2benen] 1.89 Octahedral 18
Where L’ = 1.1’-diacetyl ferrocene,
L’ = Salicylidene –p- aminoazobenzene,
acphen = bis (acetophenone) ethylenediamine,
5-Clasal = 5 –chlorosalicyldehyde,
bzal = 1 – phenyl- 1, 3 – butanedione,
L2 = 2 – (thiomethyl – 2’ – benzimidazolyl) benzaimidazole,
SB-Cl = chlorosalicylidene – p anisidene,
benen = bis (benzylidene) ethelenediamine,
Studies on metal chelates……………….. Chapter-5
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In presence case the magnetic susceptibility of the Cu (II) chelates are
given in table 5.2, the magnetic moment value of the Cu (II) chelates lies in
between 1.79 – 1.95 B.M. these values are close to the spin allowed values
expected for a S = ½ system (1.73 B.M.) and may be indicative of an
octahedral geometry around the Cu (II) ions 10
The representative plot of field Vs moment of the metal chelate are
given on page no.121.
Table 5.2 Magnetic susceptibility of copper (II) Schiff base chelates
Schiff base Cu(II) chelates µ eff.(B.M.)
Cu(II)( L1-o-v-A)2H2O 1.95
Cu(II)( L2 - Sal – A)2H2O 1.87
Cu(II)(L3 -O-H-Naph.-A) 2H2O 1.79
Where
L1 –o-v-A = 6,6’-(4,4’-(cyclohexane-1,1-diyl) bis(4,1-phenylene)) bis (azan-1-yl-1- ylidene) bis (methan-1-yl-1ylidene) bis (2-methoxy phenol)
L2-sal- A = 2,2’-(4,4’-(cyclohexane-1,1-diyl)bis(4,1-phenylene))bis(azan-1-yl-1-ylidene)bis(methan-1-yl-1-ylidene) diphenol
L3-O-H-Naph.- A =1,1’-(4,4’(cyclohexane-1,1-diyl)bis(4,1-phenylene))bis(azan-1-yl-1-ylidene)bis(methan-1-yl-1-ylidene)dinaphthalen-2-ol
Studies on metal chelates……………….. Chapter-5
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Calculation of the effective magnetic moment value from the graph for
the [Cu(II)( L1-o-v-A)2H2O]
χ m = slop at HC x mol.wt.
Mass
= 1.76 x 10 -7 x 632.17
0.070
= 1.589 x10-3
µ eff. = 2.84 √ χ m x T where T = absolute temperature (298oK)
µ eff. = 2.84 √1.589 x10-3 x 298
µ eff. = 1.95 B.M.
Studies on metal chelates……………….. Chapter-5
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Fig. 5.1 Plot of field Vs moment of the [Cu(II)( L1-o-v-A)2H2O]
Slop at HC 1.76 e-07 amu slop: 0 amu/Oe
Studies on metal chelates……………….. Chapter-5
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Magnetic susceptibility of the cobalt (II) Schiff base chelates.
The Co (II) ion has 3d7 configurations with free ion ground term 4F in
high – spin complexes, and 2G in low – spin complexes. So it has three
unpaired electrons in it sub shell. The observed value of magnetic moment is
higher than calculated on the basis of spin – only formula µ = 4S(S+1). A
value is 3.87 B.M. to expect to be exhibit magnetic moment is equal to spin –
only values.
This suggests that there is also an orbital contribution. To have an
orbital angular moment it must be possible to transform an orbital into an
equivalent orbital by rotation. It is possible to transform the t2g orbitals (dxy, dxz,
and dyz) into each other by rotating 900 . It is not possible to transform the e.g.
orbital’s in this way (e.g. the dx2-y2 into the dz2 ), since they have different
shapes. If the t2g orbital are all singly occupied, then it is not possible to
transform the dxy into dxz or dxz since they already contain an electron with the
same spin. Similarly it is not possible to transform the t2g orbitals if they are all
doubly occupied. Thus configuration with (t2g)3 or (t2g)0 have no orbital
contribution, but the other all have an orbital contribution. Thus in octahedral
complexes the following arrangements have an orbital contribution:
(t2g)1 (eg)0 (t2g)2(eg)0 (t2g)4(eg)2 (t2g)5(eg)2
Co2+ has the (t2g)5 (eg)2 configuration ,hence the high value of µ is due to the
orbital contribution. Some literature magnetic moment data of the Co (II)
complexes are summarized as following table 5.3.
Studies on metal chelates……………….. Chapter-5
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Table - 5.3 Some literature magnetic moment data of the Co (II)
complexes are summarized as follow.
No. complexes
µ eff
(B.M.) Geometry Reference
1 [Co(H2L)(H2O)3] 5.40 Octahedral 4
2 [Co(Py)4(SO3Cl)2] 5.11 Octahedral 2
3 [CoL2Cl2] 5.75 Octahedral 5
4 Co(CNCHMe)4{NH2CSNH2}](ClO4)2 4.92 Octahedral 6
5 [Co(LH2)] 4.62 Octahedral 3
6 [CoL’Cl2] 4.42 Octahedral 7
7 [CoL”Br2] 4.90 Octahedral 8
8 Co2L’2X2 4.40 Tetrahedral 19
9 Co(L3)2 3.85 Tetrahedral 20
Where
H2L = salicylidine – 2 – aminobenzimidazole
Py = pyridine
L = 2- (1-indazolyl)benzothizole
LH = α – bromo acetoacetanilide semicarbazone
L’ = 1,4,8,12- tetraaza – 4 – (1’,1’ – dimethylethyl ) – 2
(1’’,1’’,2’’,2’’,3’’,3’’,3’’-heptafluoropropyl)-9,11-(dimethylcyclotetradeca)-
1,4,8,11-tetraene
L’’ = 2- (thiomethyl-2-benzimidazolyl)benzimidazole)
L’2 =4-[2’-hydroxysalicylidene5’ (2’’thiozlyazo)] chlorobenzene
X2 = Cl
L3 = p- aminoacetophenoneoxime – 5 - hydroxysalicylaldiminato
Studies on metal chelates……………….. Chapter-5
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In present work the magnetic moment values of Co (II) Schiff base
chelates are presented in table 5.4. The magnetic moment values for the Co
(II) chelates have been used as criteria to determine the type of coordination
around the metal ion. Due to the intrinsic orbital angular momentum in the
ground state, there is consistently a considerable orbital contribution and the
effective magnetic moment values of the Co (II) chelates are lies in between
3.90 - 4.10 B.M., which are slightly greater than the spin – only value
(3.87B.M.). This high value of the magnetic moment and the stoichiometries
suggest a coordination number of six for the central Co (II) ion and an
octahedral geometry 11. The representative plot of field Vs moment of the
metal chelate are given on page no.126.
Table - 5.4 Magnetic Susceptibility of the cobalt (II) Schiff base Chelates.
Schiff base metal chelates µeff . (B.M.)
Co(II)( L1-o-v-A)2H2O 3.98
Co(II)(L2 -Sal –A)2H2O 3.90
Co (II)( L3 -O-H-Naph.-A) 2H2O 4.10
Where
L1 –o-v-A = 6,6’-(4,4’-(cyclohexane-1,1-diyl) bis(4,1-phenylene)) bis (azan-1-yl-1-
ylidene) bis (methan-1-yl-1ylidene) bis (2-methoxy phenol)
L2-sal- A = 2,2’-(4,4’-(cyclohexane-1,1-diyl)bis(4,1-phenylene))bis(azan-1-yl-1-ylidene)bis(methan-1-yl-1-ylidene) diphenol
L3-OHNaph.- A =1,1’-(4,4’(cyclohexane-1,1-diyl)bis(4,1-phenylene))bis(azan-1-yl-1-ylidene)bis(methan-1-yl-1-ylidene)dinaphthalen-2-ol
Studies on metal chelates……………….. Chapter-5
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Calculation of the effective magnetic moment value from the graph for
the [CoL1-o-V –A-2H2O]
χ m = slop at HC x mol.wt. Mass
= 4.74 x 10 -7 x 627.56
0.045
= 6.610 x 10 -3
µ eff. = 2.84 √ χ m x T where T = absolute temperature (298oK)
µ eff. = 2.84 √ 6.610X10-3 x 298
µ eff. = 3.98 B.M.
Studies on metal chelates……………….. Chapter-5
126
Fig. 5.2 Plot of field Vs moment of the [CoL1-o-V –A-2H2O]
Studies on metal chelates……………….. Chapter-5
127
Magnetic susceptibility of the Nickel (II) Schiff base chelates.
The electronic configuration of Ni (II) is [Ar]3d8. Ni (II) forms stable chelates with coordination number four and six. Compounds of higher coordination number are rare. The principal geometries of its complexes are octahedral and square – planar. Some trigonal bipyramidal, square pyramidal and tetrahedral complexes are also known.
In tetrahedral ligand field Ni (II) has an orbitally degenerate 3T1g(P) term which will give rise to a relatively large orbital contribution. In regular tetrahedral stereochemistry magnetic moment is observed to be around at 3.5 to 4.0 B.M. The diamagnetic four coordinated complexes are square planar. In octahedral stereochemistry the magnetic moment of the Ni(II) complex is found to have value in between 2.8 to 4.1 B.M., consideration of spin-orbit coupling and contribution from 3A2g and the next higher 3T2g states give a some what higher magnetic moment than spin – only value 2.83 B.M. for the stereochemistry of the Ni(II) complexes, the magnetic data are specially significant. Since the stereochemistry of the attached Schiff base ligand affects the quenching of orbital magnetism, the size of the latter may in suitable cases be used as a guide to stereochemistry.
Table - 5.5 Some literature magnetic moment data of the Ni(II) complexes
are summarized as follow.
No. Complexes µ eff
(B.M.) Geometry References
1 [NiL2Cl2] 2.99 Octahedral 5
2 [NiL]Cl2 3.06 Octahedral 9
3 Ni(HL)2H2O 3.85 Octahedral 4
4 [Ni(L)2] 2.40 Octahedral 12
5 [NiHL(H2O)Cl] 2.87 Octahedral 13
6 Ni(5-ClSal)(acac)(H2O)2 2.73 Octahedral 14
7 Ni(L1)2 2.71 Tetrahedral 19
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128
Where
L = 2(1- indazolyl)benzothizole,
L = 6, 10, 16, 20- tetraketo- 8, 18 – dithia – 1, 5, 11, 15-
tetrazocycloeicosane,
L = salicylidine -2- aminobenzimidazole,
L = 4- (1-phenyl – 1- methylcyclobutane -3-yl)-2-(2-hydroxy-5-
bromo)benzalidene aminothiazide
L= 1,4-di(hydroxybenzylidene)thio – semicarbazide
5-Clsal = 5-chlorosalicylaldehyde
acac = acetylacetone
L = salicylidene -1- amino -5- benzoyl -4- phenyl -1H –pyrimidine-2-
thione
L1= p- aminoacetophenoneoxime – 5 - hydroxysalicylaldiminato
Magnetic susceptibility of the Ni (II) Schiff base metal chelates in the
present work have been measured at room temperature. The values of
magnetic moment are incorporated in Table 5.6. The magnetic moment
values are observed in the range 2.81 to 3.11 B.M., corresponding to 2-
unpaired electron. The magnitude of magnetic moment clearly indicates that
Ni (II) ion has paramagnetic nature in all the Ni (II) Schiff base metal chelates,
with octahedral structure. The slight variation in magnetic moment values for a
high-spin Ni+2 chelates depend on the magnitude of the orbital contributions,
expected for similar hexa – coordinated Ni (II) ions.21 The representative plot
of field Vs moment of the metal chelate are given on page no.131.
Studies on metal chelates……………….. Chapter-5
129
Table - 5.6 Magnetic susceptibility of the Nickel (II) Schiff base chelates.
Schiff base metal chelates µeff . (B.M.)
Ni(L1-o-v- A) (H2O)2 2.94
Ni(L2-sal- A) (H2O)2 2.81
Ni(L3-O-H-Naph.- A) (H2O)2 3.11
Where
L1 –o-v-A = 6,6’-(4,4’-(cyclohexane-1,1-diyl) bis(4,1-phenylene)) bis (azan-1-yl-1- ylidene) bis (methan-1-yl-1ylidene) bis (2-methoxy phenol)
L2-sal- A = 2,2’-(4,4’-(cyclohexane-1,1-diyl)bis(4,1-phenylene))bis(azan-1-yl-1-ylidene)bis(methan-1-yl-1-ylidene) diphenol
L3-O-H-Naph.- A =1,1’-(4,4’(cyclohexane-1,1-diyl)bis(4,1-phenylene))bis(azan-1-yl-1-ylidene)bis(methan-1-yl-1-ylidene)dinaphthalen-2-ol
Studies on metal chelates……………….. Chapter-5
130
Calculation of the effective magnetic moment value from the graph for
the [Ni (L1-o-vA)
χ m = Slope at HC x mol.wt. Mass χ m = 3.16 x 10 -7 x 627.34
0.055
χ m = 3.6033 x 10-3
µ eff. = 2.84 √ χ m x T where T = absolute temperature (298o K)
µ eff. = 2.84 √ 3.6033 x 10-3 x 298
µ eff. = 2.94 B.M.
Studies on metal chelates……………….. Chapter-5
131
Fig. 5.3 Plot of field Vs moment of the [Ni (L1-o-vAH2)
Studies on metal chelates……………….. Chapter-5
132
Magnetic susceptibility of the Zinc (II) Schiff’s bases chelates.
In Zn (II) d sub shell is completely filled there are no unpaired electrons, hence the compounds of Zn (II) metal chelates are expected to be diamagnetic. Most of the Zn (II) metal chelates are expected to tetrahedral. However, octahedral Zn (II) metal complexes are reported.22
In present work, the magnetic moment determination of the Zn (II) metal chelates shows diamagnetic nature. Therefore, they have no unpaired d- electron in Zn (II), hence the chelates must be diamagnetic. The chelates are yellowish colour, which is also indicating the absence of unpaired electrons. The structure may be tetrahedral or octahedral.
Studies on metal chelates……………….. Chapter-5
133
References:
1. Figgish B.N., Introduction to ligand fields. The magnetic properties of complex ions; interscience Publishers. John Wiley and sons: new York, 248, (1967).
2. Siddiqi, Z. A.; Shakir, M.; Aslam, M.; Khan, T.A.; Zaidi, S. A. A. Synth. React. Inorg. Met.-Org. Chem.13 (4), 397, (1983).
3. Deepa K.; Arvindakshan K.K. Synth. React. Inorg. Met.-Org. Chem.31
(3).429, (2004).
4. Mohamed G.G; Abd EL – Wahab,Z.H. Jou. Of Therm. Ana. And Colri.73, 347 (2003).
5. Khan T.A.; Shahjahan, Synth. React. Inorg. Met.-Org. Chem. 31(6), 1023, (2001).
6. Becker C.A.; Odisitse S. Synth. React. Inorg. Met.-Org. Chem.30 (8), 1547, (2000).
7. Shakir M.; Chingsubam P.;Azim Y.;Parveen S.; Synth. React. Inorg. Met.-Org. Chem. 34 (5), 847, (2004).
8. Satyanarayana S.; Synth. React. Inorg. Met.-Org. Chem. 34 (5), 883, (2004).
9. Chandra S.; Gupta N.; Gupta L.K.; Synth. React. Inorg. Met.-Org. Chem. 34(5), 919,(2004).
10. Speca A. N.: Karayannis M.: Pyleuski L.L. J.Inorg.Nucl.Chem. 35, 3113 (1973).
11. Patel M.M.; Malavanan R. J. Macromol. Sci. Chem. 19A ,951 (1983).
12. Yilmaz I.: Cukurovali A.: Ahmedzale M., Synth.React.Inorg.Met.-Org.Chem. 30 (5), 919 (2000).
13. Mashaly M. M.; Abd-EL Wahab Z. A. Synth.React.Inorg.Met.-Org.Chem. 34 (2), 233 (2004).
14. Prasad R.N.; George R. Synth.React.Inorg.Met.-Org.Chem. 34 (5), 943 (2004).
15. Chohan Z. H. Synth.React.Inorg.Met.-Org.Chem. 34 (5), 833 (2004).
Studies on metal chelates……………….. Chapter-5
134
16. Ragiumov A. V. Mamedov B.A. Polymer 60, 1851 (1989).
17. Patel B.K.; Patel M.M. Ind. J. of Chem. 29(1), 90 (1990).
18. Patel M. N.; Patel K. N.; Patel N. H. Synth.React.Inorg.Met.-Org.Chem. 32 (10), 1879 (2002).
19. L.V.Gavali; P.P.Hankarep J. of Physical Science.11, 147, (2007).
20. Erdal Canpolat, Mehmet KAYA; Turk J. Chem. 29, 409, (2005).
21. Issa Y. M.; El- Hawary W. F.; Abdel –Salam H. A. Transition Met. Chem. 20, 423 (1995).
22. Aswar A. S.; Mahale R. G.; Kakede P.R.; Bhadange S. G. J.Ind. Chem. Soc. 75, 395 (1998).
23. J.D.Lee; “Concise inorganic chemistry” 5th edition john Wiley ,2003
Studies on metal chelates……………….. Chapter-6
135
GENERAL DISCUSSION
Schiff base ligands :-
The large number of Schiff bases is forming metal complexes. We have
synthesized three new Schiff bases of 1, 1’ bis (4- aminophenyl) cyclohexene [A]
like
(1). 6, 6’-(4, 4’-(cyclohexane-1, 1-diyl) bis (4, 1-phenylene)) bis (azan-1-yl-1-
ylidene) bis (methan-1-yl-1ylidene) bis (2-methoxy phenol) (L1-o-v-AH2)
(2). 2, 2’-(4, 4’- (cyclohexane-1, 1-diyl) bis (4, 1-phenylene)) bis (azan-1-yl-1-
ylidene) bis (methan-1-yl-1-ylidene) diphenol (L2 - Sal – AH2)
(3) 1,1’-(4,4’(cyclohexane-1,1-diyl)bis(4,1-phenylene))bis(azan-1-yl-1-ylidene)bis
(methan-1-yl-1-ylidene) dinaphthalen-2-ol (L3 -O-H-Naph.-AH2)
They are different in colors; dissolve in almost all organic solvent, like
benzene, CCl4, CHCl3. Their characteristic properties are discussed in chapter-3.
These Schiff base ligands have reactive system containing hydroxyl group (OH)
and azomethine group (C═ N). Thus, they are good chelating agent or ligands.
We have synthesized metal complexes of Cu (II), Ni (II), Co (II) and Zn (II) with
these ligands.
On the basis of synthesis elemental analysis, spectral studies. The
general structure of the ligands proposed to represented as,
NN
HC
OH HO
CH
OCH3 H3CO
L1-o-v-AH2
Studies on metal chelates……………….. Chapter-6
136
N NHC
OH HO
CH
L2 - Sal – AH2
NN
HC
OH HO
CH
L3 -O-H-Naph. – AH2
Studies on metal chelates……………….. Chapter-6
137
The elemental analysis as prescribed in chapter -3 table 3.1 on page.43
agrees with theoretical expected value. Thus supporting the suggested molecular
formula.
Absorption spectral studies of Schiff bases.(UV/VIS.):-
In general as it is known that the absorption of light energy by
organic compounds in visible and ultraviolet region involves transition of
electrons from the ground state to higher states. The electronic transitions that
are involved in the ultraviolet and visible regions are of the following types.
σ→ σ* , n→ σ*, n→π* , π → π*
The absorption spectra of Schiff base ligands in UV& Visible region show
bands at 280-330nm, 270-350nm, and 264 -465nm. These are attributed to π →
π* and n → π* transaction of phenyl ring and azomethine respectively. The slight
shift in the λ max due to change in molecular weight of the ligands
Table- 6.1
Absorption maximum (λ max.) and (log e) of the Schiff’s bases.
Sr. No.
Name of Schiff’s bases λ max[nm]
1 L1 -O-V-AH2 326
282
2 L2 -SAL-AH2 346
273
3 L3 – O-Naph.- AH2
464.50
444.00
264.00
Studies on metal chelates……………….. Chapter-6
138
IR Spectral studies of Schiff base ligands :-
The IR spectra of all the ligands are on page no. 47-49 in chapter -3, are
identical with slight variation in group frequency as shown in table 6.2 on
page139 , which are according to the suggested structure of the all ligands
molecules.
Studies on metal chelates……………….. Chapter-6
139
Table – 6.2
IR Spectral Data of Schiff bases (cm-1)
Schiff bases ligands
Hydroxyl-OH
(H2O)
Alkane -CH2 Aromatic
Schiff’s base
O-H str. O-H def.
C-H str. (asym.)
C-H str. (sym.)
C-H def. (asym.)
C-H def. (sym.)
C-H str.
C=C
C-H ( I.p.d
C-C (o. O .p. d. )
CH=N str.
C-N def.
L1 -O-V-AH2
3451
1407.7
2925.9
2869.1
1454.7
1396
3060
1572.3
1114.5
830
1626.7
1277.7
L2 -SAL-AH2
3450.3
1406.3
2936.0
2865.7
1463.8
1365.0
3068.5
1509.6
1082.5
828.4
1615.7
1255.7
L3–O-Naph.-AH2
3426.9
1326.1
2930.7
2864.5
1498.9
1246.2
3041.0
1571.5
1085.1
822.8
1621.0
1173.7
NMR spectral studies of Schiff base ligands:-
The NMR spectral bands are presented on page 50-52 and their value is
presented in table 3.7- 3.9 in chapter-3 on page 50-52. The structure of the
Schiff base ligands molecule is further supported by the NMR spectral data.
Mass spectral studies of Schiff base ligands:-
For purpose of supporting the proposed structure of the Schiff bases. The
mass spectral analysis was carried out. The mass spectra are presented on page
53-55 in chapter-3. These data are also in good agreement with proposed
structure of Schiff base ligands molecules.
Metal chelates:-
Metal complexes of Cu (II), Ni (II), Co (II), and Zn (II) were synthesized
and the studies of their characteristic, properties are mentioned in chapter - 3.
All the copper (II), nickel (II), cobalt (II), and Zn (II) complexes are
insoluble in water and common organic solvents. It is soluble in DMSO and DMF.
From the elemental analysis it is found that the all complexes are type ML.
The molecular weight determine by Rast’s camphor method although not
very reliable still it is in agreement with the suggested molecular formula of all
complexes.
The conductivity of solution of all complexes in DMF was measured and
low values of conductivity observed suggest that the metal complexes are non –
ionic in nature.
Infrared spectra
Infrared spectroscopy deals with the study of molecular vibrations and
rotations. One of the important applications of vibrational spectra is the
Studies on metal chelates……………….. Chapter-6
141
determination of shape of a molecule. Although the infrared spectrum is
characteristic of the entire molecule, it turns out that certain functional groups
give bands at or near the same frequency regardless of the structure of the rest
of molecule. This fact forms the basis of the use of infrared spectra in qualitative
identification of a substance. The spectra of all metal complexes are given in
chapter -3. Discussion is as following.
The infrared spectra of Cu (II) chelates
The copper (II) complexes exhibit a broad band in the region 3400-3000
cm-1, suggesting the presence of coordinated water molecules1. The weak band
around 850 cm-1 are assigned as υ (OH) stretching rocking and wagging
vibration2. The IR spectra of Schiff bases display a strong absorption bands at
1615.7, 1626.7 and 1621.0 cm-1 for L1-o-v-AH2, L2 - Sal – AH2 and L3 -O-H-
Naph.-AH2 respectively assignable to C= N stretching mode, shift towards lower
frequency region by 1607.5, 1610.5, 1612.0 respectively in the complexes
indicating coordination through the azomethine nitrogen.3,4. The appearance of
sharp bands around 1441.7 cm-1, 1444.7, cm-1 and 1321.6 cm-1. Is attributed to υ
(C-O) band, which indirectly supports bonding of phenolic oxygen to metal ion.
The band observed in the region of 521-551cm-1 is attributed to υ (M-N). The υ
(M-O) band may be observed in the region 475-495 cm-1 5, 6. The IR spectra are
represented as in fig.3.13 – 3.15 on page no.63-65. In chapter-3
The infrared spectra of Ni (II) chelates
The nickel (II) complexes exhibit a broad band in the region 3400-
3425cm-1, suggesting the presence of coordinated water molecules 1. the weak
band around 856 cm-1 are assigned as υ (OH) stretching rocking and wagging
vibration 2 The IR spectra of Schiff bases display a strong absorption bands at
1615.7, 1626.7 and 1621.0 cm-1 for L1-o-v-AH2, L2 - Sal – AH2 and L3 -O-H-
Naph.-AH2 respectively assignable to C= N stretching mode, shift towards lower
Studies on metal chelates……………….. Chapter-6
142
frequency region by 1608.5, 1615.5, 1611.2 respectively in the complexes
indicating coordination through the azomethine nitrogen to the metal.7 The
appearance of sharp bands around 1440.7 cm-1, 1444.5, cm-1 and 1327.1cm-1. Is
attributed to υ (C-O) band, which indirectly supports bonding of phenolic oxygen
to metal ion 8. In the low frequency region, the band observed in the region of
520-547cm-1 is attributed to υ (M-N). In the region of 470-490 cm-1 attributed to
υ (M-O) phenolic band 6. The IR spectra are represented as in fig. 3.17 - 3.19.On
page no.72-74, in chapter - 3
The infrared spectra of Co (II) chelates
The cobalt (II) complexes exhibit a broad band in the region 3400-
3429cm-1, suggesting the presence of coordinated water molecules9. the weak
band around 855 cm-1 are assigned as υ (OH) stretching rocking and wagging
vibration 2 .The IR spectra of Schiff bases display a strong absorption bands at
1615.7, 1626.7 and 1621.0 cm-1 for L1-o-v-AH2, L2 - Sal – AH2 and L3 -O-H-
Naph.-AH2 respectively assignable to C= N stretching mode, shift towards lower
frequency region by 1614.5, 1608.8, 1612.2 respectively in the complexes
indicating coordination through the azomethine nitrogen to the metal.7 The
appearance of sharp bands around 1445.5 cm-1, 1436.0, cm-1 and 1329.0cm-1. Is
attributed to υ (C-O) band, which indirectly supports bonding of phenolic oxygen
to metal ion 8. In the low frequency region, the band observed in the region of
500-515cm-1 is attributed to υ (M-N). In the region of 475-485 cm-1 to υ (M-O)
phenolic band may be observed 6, 7. The sharp band near 725-760cm-1 and
1490-1530cm-1 are due to aromatic υ (C-H) 10. And υ (C=C) 11, respectively. The
IR spectra are represented as in fig.3.21 – 3.23 on pages no.81 -83, in chapter- 3
Studies on metal chelates……………….. Chapter-6
143
The infrared spectra of Zn (II) chelates
The zinc (II) complexes exhibit a broad band in the region 3400- 3410cm-1,
suggesting the presence of coordinated water molecules 8. the weak band
around 847 cm-1 are assigned as υ (OH) stretching rocking and wagging vibration
2 .The IR spectra of Schiff bases display a strong absorption bands at 1615.7,
1626.7 and 1621.0 cm-1 for L1-o-v-AH2, L2 - Sal – AH2 and L3 -O-H-Naph.-AH2
respectively assignable to C= N stretching mode, shift towards lower frequency
region by 1614.3, 1610.2, 1611.0 respectively in the complexes indicating
coordination through the azomethine nitrogen to the metal.7 The appearance of
sharp bands around 1459.3 cm-1, 1453.9, cm-1 and 1392.0cm-1.Is attributed to υ
(C-O) band, which indirectly supports bonding of phenolic oxygen to metal ion8.
In the low frequency region, the band observed in the region of 500-575cm-1 is
attributed to υ (M-N). In the region of 450-470 cm-1 to υ (M-O) phenolic band
may be observed 5, 6 the sharp band near 725-760cm-1 and 1490-1530cm-1 are
due to aromatic υ (C-H) 10. and υ (C=C)11,respectively. The IR spectra are
represented as in fig. 3.25 -3.27 on pages 90 – 92, in chapter - 3
Thermo gravimetric analyses
Thermogravimetric analysis has been obtained by a model PerkinElmer
Pyris1 TGA instrument. The thermal curves were obtained at a heating rate of
100C/ min over the temperature range of 50-8000C. It has been observed that all
the metal chelates clearly show a weight loss corresponding to two water
molecules in range ~110-2950C, indicating that these water molecules are
coordinating to the metal ion. 12-16. The TG curves indicate that in the
temperature range between ~ 295 -700 0C and 8000C the Schiff base molecules
are lost. In all the cases the final products are metal oxides. These results are in
good accordance with the composition of the metal chelates. The result are given
in table 4.1 on page 102 and selected thermogram of metal chelates are given in
fig.4.1 – 4.4 on page 103-106 in chapter -4.
Studies on metal chelates……………….. Chapter-6
144
Magnetic properties and Electronic spectra of Cu(II) chelates
The magnetic moment of Cu (II) ion in octahedral or planar
stereochemistry generally lies around 1.98 B.M. at room temperature. The
magnetic susceptibility of copper (II) complexes is given in table 5.2 in chapter -
5.These magnetic moment values are lies between 1.79 to 1.95 B.M. are very
closed to spin- only value (1.73B.M.). These values consistent with an octahedral
geometry. 17. Most of Cu (II) complexes and compounds have a distorted
octahedral structure and are blue or green. The metal ion has the d9 electronic
configuration gives rise to the 2D free ion term, which is split in a regular
octahedral field into a lower doublet Eg level and an upper triplet T2g level.18,19.
Thus , only one spin allowed d-d transition 2Eg → 2T2g the d9 configuration is
highly Jahn – Teller unstable and the resulting
tetragonal distortion(D4h) leads to the further splitting of Eg and T2g level into B1g
,A1g, and B2g ,Eg. Levels, respectively 20-24
, this splitting of the state increases with
the tetragonal component of the crystal field. As the energy of the 2A1g state
increases, a situation may arise in which this is sufficient close to the 2Eg and
2B2g
The UV/Visible absorption spectra of all the copper (II) chelates are shown
in fig. 3.12 in chapter -3 and spectral data are summarized in table 3.11 in
chapter-3. All the Cu (II) chelates show π→ π*, n→π* and C→T, transition at
220-255, 270-305, and 300-400 respectively and- d → d transition at
597,727,411 nm for all complexes. This assignment is in agreement with the
general observation 25. According absorption spectra and magnetic
susceptibility value, geometry of Cu(II) Schiff base metal complexes are conform
the distorted octahedral
Studies on metal chelates……………….. Chapter-6
145
Magnetic properties and Electronic spectra of Ni (II) chelates
Ni (II) is 3d8 has two unpaired electron on its subshell. Hence, it is
assumed that all compounds containing Ni (II) are expected to exhibit magnetic
moment close to spin- only values for two unpaired electrons (2.83 B.M.).
Deviation from the spin –only value of 2.83 B.M., i.e. the orbital contributions to
the magnetic moment, depends on the stereochemistry of the complex. In some
cases the magnetic moments indicate the exact stereochemistry of the complex.
For example the Ni(II) complexes 26,27 exhibit zero magnetic moment and are
considered to have diamagnetic behavior, while those Ni(II) complexes 28 having
magnetic moments 2.8-3.3 B.M. may exist in octahedral stereochemistry. The
excess values may be due to distorted nature. The room temperature magnetic
moments for tetrahedral Ni (II) complexes 29 usually lie in the range 3.6 -4.1 B.M.
The magnetic moments of the Ni (II) complexes studied in present work
are given in table 5.6 in chapter -5.These magnetic moment of the Ni (II)
complexes were found to be in the range 2.81 to 3.11 B.M. corresponding to two
unpaired electrons. The magnitude of magnetic moment clearly indicates that Ni
(II) ion has paramagnetic nature in all the complexes, with octahedral structures.
The slightly higher magnetic moment in some of the cases may be assigned due
to orbital contribution. The magnetic moment values in present work are within
range expected for similar hexa-coordinated Ni (II) ions, which is also supported
by many similar observation30-31.
The large numbers of sterochemical forms in nickel (II) complexes are
reported. Different types of d-d transition in various sterochemical forms of Ni (II)
are briefly discussed.
The absorption spectra of six-coordinated nickel (II) complexes have been
studied extensively32. It shows simple spectra involving three main bands in the
regions 7,000- 13,000; 14,000-17,000 and 20,000 – 27,000 cm-1. The bands may
be assigned to 3A2g → 3T2g (F), 3A2g →
3T1g (F), 3A2g →
3T1g (P)
respectively33. Sometime, second transition exhibits double peak nature, for
which different explanation are suggested 34, 35.
Studies on metal chelates……………….. Chapter-6
146
The tetrahedral nickel (II) complexes have a multiple band at 15,000 -
18,000cm-1 which is assigned to 3 T1 (F) → 3 T2 (P) (v3) transition. Weak band on
either side are spin- forbidden transitions assigned to components of 1D and 1G
level respectively 36.
The square planar complexes of nickel (II) are usually orange, red, brown,
or yellow but purple and green coloured examples are also known 37-40. The
majority of these complexes exhibit a strong absorption band in the visible region
between 15,000 and 25,000 cm-1 may be assigned to 1A1g → 1A2g transition and
in many cases a second more intense band between 23,000 and 30,000cm-1
assigned to the 1A1g → 1B1g transition 35, 38. Square planar complexes of nickel
(II) can readily be distinguished from octahedral or tetrahedral complexes by
absence of transition below 10,000 cm-1.
The electronic absorption spectra of Ni (II) chelates are shown in fig .3.16
in chapter -3 and spectral data are summarized in table 3.14 in chapter -3. All the
Ni (II) chelates shows π→ π*, n→π* and C→T, transition at 250-260, 270-300,
and 300-325 and d-d transition at 326-405 and at 759. Using energy level
diagram, this three band may be assigned to 3A2g → 3T2g (F), 3A2g →
3T1g
(F), 3A2g → 3T1g (P) respectively, for an octahedral stereo- chemistry 41 .
Magnetic properties and Electronic spectra of Co(II) chelates
The Co (II) ion has 3d7 configurations with free ion ground term 4F in high-
spin complexes, and 2G in low-spin complexes. Octahedral and tetrahedral
stereo chemistries are very common for the Co (II) 42. Square planar 43 and
pentacoordinated 44 complexes of Co (II) are also reported. Tetrahedral
complexes are usually more favourable for Co (II) than any other transition metal
ion because the ligand field stabilization favours the tetrahedral stereochemistry
relative to octahedral one.
The magnetic properties of high-spin octahedral cobalt (II) complexes are
governed by orbital degenerated ground term 4 T1g, this provide the orbital
Studies on metal chelates……………….. Chapter-6
147
contribution to the magnetic moment, so that at room temperature magnetic
moment values are found to lie in the range of 4.30-5.20 B.M. and these values
very appreciably with change in the temperature 45. Low –spin octahedral Co (II)
complexes have 2Eg ground term arising from the t2g6 eg
1 electronic configuration
46. The magnetic moment values of these types of complexes usually lie in the
range 1.70 – 1.85 B.M.
In present work magnetic moment values of all the complexes are
presented in table 5.4 in chapter 5. The magnetic moment of the Co (II)
complexes were found to be in the ranges 3.90 - 4.10 B.M. The magnitude of
magnetic moment clearly indicates that all chelates are paramagnetic in nature,
with octahedral structures. The magnetic moment data are may be slightly lower
than three unpaired electrons which may be due to mixture of spin free
octahedral and tetrahedral geometries as predicted by Aggarwal and others 47, 48.
The low magnetic moments for d7 Co (II) ion may also be due to equilibrium
between low- spin and high- spin octahedral states. The complexes in which
magnetic moments (3.9 -4.88 B.M.) are slightly higher than three unpaired
electrons which may be due to the intrinsic orbital angular momentum in the
ground state, there is consistently a considerable orbital contribution. This
deviation from the spin only value (3.87B.M.) may be ascribed to spin orbital
coupling and suggest 49 an octahedral geometry for the Co (II) complex in the
high – spin state.
The Co (II) ion has the electron configuration d7, and its ground state
configuration in an octahedral ligand field may be either t2g5eg
2 in weak field or
t2g6eg
1 in strong fields. The ground term of Co (II) in octahedral environment is
4T1g or
2Eg depending on whether the complex is high spin or low-spin. The cobalt
(II) chelates shows three bands at 8928, 18518 and 21978 cm-1, which may be
assigned to the 4T1g →
4T2g (F),
4T1g →
4A2g (F) and
4T1g →
4T1g (P) transition
respectively in octahedral symmetry 50.
Studies on metal chelates……………….. Chapter-6
148
The electronic absorption spectra of Co (II) chelates are shown in fig .3.20
in chapter -3 and spectral data are summarized in table 3.17 in chapter -3.In
present work, the Co (II) complexes show three band in the regions 250-260 nm,
300-320nm and 500-561 nm these three band due to π→ π*or n→π* , C→T
or d-d transition for octahedral stereochemistry.
Magnetic properties and Electronic spectra of Zn(II) chelates
In present work, the magnetic moment determination shows that all the
complexes are diamagnetic nature. Therefore, they have no unpaired d-electron
in Zn (II), hence the complexes must be diamagnetic .The experimental data
coincident with theoretical prediction. The complexes are yellowish, which also
indicate the absence of unpaired electron. The structure may be tetrahedral or
octahedral 51-54.
In Zn (II),‘d ’ sub- shell is completely filled. There are no unpaired
electrons, hence, d-d transition are not possible in the complexes of Zn (II).
The electronic spectra of Zn (II) complexes exhibit bands in the range 414-
325 nm; 325-271nm and 251-258 nm which may be due to ligands transitions.
The electronic absorption spectra of Zn (II) chelates are shown in fig .3.24, in
chapter -3. The values are shown in table – 3.20 in chapter-3.They may be a
π→π*, n→π* transition. Most of complexes of Zn (II) are expected to be
tetrahedral. However, octahedral Zn (II) complexes are reported 55, 56.
Studies on metal chelates……………….. Chapter-6
149
Conclusion:-
The important point of the Schiff bases metal chelates are as follow.
1. Insoluble in water, methanol and other common organic solvent.
2. Soluble in polar organic solvent dimethyl sulfoxide, dimethyl formamide.
3. High melting point colored and stable in air.
4. Octahedral geometry.
5. The Co (II), Ni (II) and Cu (II) Schiff bases ligands chelates are
paramagnetic while Zn (II) Schiff bases ligands chelates are diamagnetic.
Based on the analytical, spectroscopy data, magnetic
measurements and thermal studies the following fig.6.1-6.3 tentative
octahedral structures has been proposed for all the Schiff bases ligands
chelates [ M (L1-o-v-A)(2H2O)], [M( L2-sal-A)(2H2O)], [M(L3-O-H-Naph-
A)(2H2O)]
NN
CH CH
O
M
O H2O
H2O
OCH3 H3CO
Fig.6.1
Studies on metal chelates……………….. Chapter-6
150
NN
HC HC
O
M
O H2O
H2O
Fig.6.2
NN
HC CH
O
M
O H2O
H2O
Fig.6.3
Studies on metal chelates……………….. Chapter-6
151
Where
M = Cu (II), Ni (II), Co (II), Zn (II)
(L1-o-v-A) =
6, 6’-(4, 4’-(cyclohexane-1, 1-diyl) bis (4, 1-phenylene)) bis (azan-1-yl-1- ylidene)
bis (methan-1-yl-1ylidene) bis (2methoxy phenol)
(L2 - sal – A) =
2, 2’-(4, 4’- (cyclohexane-1, 1-diyl) bis (4, 1-phenylene)) bis (azan-1-yl-1-ylidene)
bis (methan-1-yl-1-ylidene) diphenol
(L3 -o-H-Naph.-A) =
1,1’-(4,4’(cyclohexane-1,1-diyl)bis(4,1-phenylene))bis(azan-1-yl-1-ylidene)bis
(methan-1-yl-1-ylidene) dinaphthalen-2-ol
Studies on metal chelates……………….. Chapter-6
152
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