vanilina_aminoalcooli

8/13/2019 Vanilina_aminoalcooli

1/22

Synthesis, crystal structures and fluorescence studies of three new Zn(II)

complexes with multidentate Schiff base ligands

Yu-Fei Ji, Rui Wang, Shuai Ding, Chun-Fang Du, Zhi-Liang Liu

PII: S1387-7003(11)00574-0

DOI: doi:10.1016/j.inoche.2011.11.027

Reference: INOCHE 4413

To appear in: Inorganic Chemistry Communications

Received date: 26 September 2011

Accepted date: 22 November 2011

Please cite this article as: Yu-Fei Ji, Rui Wang, Shuai Ding, Chun-Fang Du, Zhi-LiangLiu, Synthesis, crystal structures and fluorescence studies of three new Zn(II) complexeswith multidentate Schiff base ligands, Inorganic Chemistry Communications (2011), doi:10.1016/j.inoche.2011.11.027

This is a PDF file of an unedited manuscript that has been accepted for publication.As a service to our customers we are providing this early version of the manuscript.The manuscript will undergo copyediting, typesetting, and review of the resulting proofbefore it is published in its final form. Please note that during the production processerrors may be discovered which could affect the content, and all legal disclaimers thatapply to the journal pertain.
http://dx.doi.org/10.1016/j.inoche.2011.11.027http://dx.doi.org/10.1016/j.inoche.2011.11.027http://dx.doi.org/10.1016/j.inoche.2011.11.027http://dx.doi.org/10.1016/j.inoche.2011.11.027


2/22

ACCEP

TED

MANUSCRIPT

ACCEPTED MANUSCRIPT

Synthesis, crystal structures and fluorescence studies of

three new Zn(II) complexes with multidentate Schiff base

ligands

Yu-Fei Ji, Rui Wang, Shuai Ding, Chun-Fang Du, Zhi-Liang Liu *

College of Chemistry and Chemical Engineering, Inner Mongolia University, 010021, Hohhot, P. R.

China

* Corresponding author. Tel.: +86-471-4995414. E-mail addresses: [email protected] .

Abstract

Three new zinc(II) complexes Zn(L1)2 (1), Zn2L2(OAc)3 (2) and Zn2L

3(OAc)3 (3) have been

synthesized by using Zn(OAc)22H2O and potentially multidentate Schiff base ligands HL1

(2-((1-hydroxybutan-2-ylimino)methyl)-6-methoxyphenol), HL2(2-((1-hydroxy-2-methyl-propan-

2-ylimino)methyl)-6-methoxyphenol) and HL3 (2-((2-hydroxypropylimino)-methyl)-6-

methoxyphenol), respectively. These Schiff base ligands are the condensation product of o-vanillin

and corresponding amino alcohols. All the three complexes 1, 2and 3have been characterized by

elemental analysis, IR, single crystal X-ray diffraction and fluorescence studies. Structural studies

reveal that 1is a mononuclear complex whereas in dinuclear complexes 2and 3the two Zn(II)

centers are held together by deprotonated Schiff base ligands and acetates. All the synthesized

complexes display intraligand (*) fluorescence and can potentially serve as photoactive

materials.

Keywords:

Schiff base ligand

Zinc(II) complex

Crystal structure


3/22

ACCEP

TED

MANUSCRIPT

ACCEPTED MANUSCRIPT

Fluorescence

In the past decades, the rational design and synthesis of zinc coordination compounds with

novel structures have received considerable attention, mostly motivated by their potential

applications in the field of luminescence, nonlinear optics, molecular sensing, and so on [1-5].

Zinc(II) ion has no optical spectroscopic signature due to its closed-shell 3d10configuration, but it

can enhance ligands luminescence upon coordination [6, 7].

Schiff base ligands have been extensively studied in coordination chemistry mainly due to

their facile syntheses, tunable steric and electronic properties. It is well known that ligands

containing N and O atoms can easily coordinate metal ions [8-15]. Therefore, Schiff base ligands

possessing N, O-donor and chromophore groups are of important building blocks to construct

luminescence complexes [16-23].

In this work, we have successfully synthesized three new zinc(II) complexes containing

Schiff base ligands that can afford various coordination modes. Our strategy is the use of

multidentate Schiff base ligands to control the nuclearity. Herein, HL1

(2-((1-hydroxybutan-2-ylimino)methyl)-6-methoxyphenol), HL2 (2-((1-hydroxy-2-methyl-

propan-2-ylimino)methyl)-6-methoxyphenol) and HL3 (2-((2-hydroxypropylimino)methyl)-

6-methoxyphenol) (see Scheme) [24] were used for constructing the zinc(II) complexes. We report

here the synthesis, crystal structures and fluorescence properties of a mononuclear zinc(II)

complex with formula Zn(L1)2 (1) [25] and two dinuclear zinc(II) complexes with formula

Zn2L2(Ac)3 (2) [26] and Zn2L

3(Ac)3 (3) [27].

X-ray crystallographic analysis [28] (Crystal data for the complexes 1, 2and 3are shown in

Table 1) shows that complex 1exhibits a chiral space group; the chirality of complex 1 comes


4/22

ACCEP

TED

MANUSCRIPT

ACCEPTED MANUSCRIPT

from the chiral ligand HL1. Each of the unit cells comprises two mononuclear units. A perspective

view of [Zn(L1)2] is depicted in Fig. 1 and some selected bond lengths and angles are presented in

Table 2. In each asymmetric unit, the Zn(II) ion is coordinated by four N, O-donor atoms: two

nitrogen atoms (N1, N2) from different imino groups of HL1, two oxygen atoms (O5, O2) from

phenoxido groups of HL1, respectively. The coordination environment around the Zn(II) center is

a distorted tetrahedral geometry. All NZn(II) and OZn(II) bond distances are within the normal

range observed in other four-coordinated zinc(II) complexes [29-31]. With strong hydrogen bonds

(H4O5#1 = 1.995, Symmetry Transformation#1: x,y1,z) between the phenolic hydroxyl and

the alcohols hydroxyl of (L1), asymmetric unit were connected into a 1D chain structure (See Fig.

2).

Complex 2 contains (L2)ligand anion instead of (L3)ligand anion. Here we describe the

structure of 2. X-ray crystallographic analysis shows that complex 2exhibits a dinuclear structure,

as shown in Fig. 3. Each of the unit cells comprises four dinuclear units. The asymmetric unit

contains two zinc ions, one (L2)ligand anion, and three acetoxy anions. The Schiff base ligand

displays flexible tetradentate (N1O1O6O7 donor set) coordination mode in the structure. The

coordination geometry of Zn1center with a tetragonal pyramid (ZnNO4) is pentacoordinated by

two oxygen atoms (Zn1-O1 = 2.170, Zn1-O7 = 2.044) from (L2) ligand anion, another two

oxygen atoms (O2, O8) belong to the two distinct acetates (Zn1-O2 = 1.974, Zn1-O8 = 1.965) and

the nitrogen donor atom (Zn1-N = 2.032) belongs to azomethine of (L2). The square base around

Zn1 is formed by phenolato, alcoholic hydroxyl oxygen atoms and azomethine nitrogen atom (O1,

O7 and N1 respectively) from the bridging (L2) and carboxyl oxygen (O2), whereas the axial

sites are occupied by another carboxyl oxygen (O8). The six coordinated Zn2 ions have ZnO6


5/22

ACCEP

TED

MANUSCRIPT

ACCEPTED MANUSCRIPT

distorted octahedron coordination sphere. The six O-donor atoms belong to two bridging carboxyl

groups of acetate (Zn2-O3 = 2.032, Zn2-O9 = 2.027), a chelating carboxyl group of acetate

(Zn2-O4 = 2.029, Zn2-O5 = 2.379), phenolate and methoxy group of (L2)ligand anion (Zn2-O6 =

2.360, Zn2-O7 = 1.996), respectively. The two zinc centers are bridged by phenolic hydroxyl of

the Schiff base ligand and two carboxyl groups of acetate with ZnZn distance of 3.228(8) .

The fluorescence properties [17] of the Schiff base ligands and its Zn(II) complexes (1, 2and

3) were investigated at room temperature (298 K) in methanolwater solutions (see Fig. 4). For

excitation wavelengths between 280 and 440 nm, there is no obvious emission observed for free

ligands. The fluorescence of the ligands are probably quenched by the occurrence of a

photoinduced electron transfer (PET) process due to the presence of a lone pairs of electrons of the

donor atoms in the ligands (N, O-donor) [17, 32]. All the three complexes exhibit strong blue

emission bands in comparison to the corresponding free ligands. For Zn(II) complexes, no

emission originating from metal-centered MLCT/LMCT excited states are expected, since the

Zn(II) ion is difficult to be oxidized or reduced due to its stable d 10 configuration. Thus, the

emission observed in the complexes is tentatively assigned to the * intraligand fluorescence

[33]. Moreover, in Zn(II) complex, the PET process is prevented by the complexation of HL with

metal ions, thus the fluorescence intensity may be greatly enhanced by the coordination of Zn(II).

The chelation of the ligands to Zn(II) increases their rigidity and thus reduces the loss of energy

by thermal vibrational decay [32].

It is worthy of note that the complex 1 shows a higher emission intensity than that of the

complex 2and 3. This is supported from their calculated quantum yield values with reference to

quinine sulfate (See Table 3). This could be accounted for the fact that every Zn(II) ion


6/22

ACCEP

TED

MANUSCRIPT

ACCEPTED MANUSCRIPT

coordinates with two Schiff base ligands in 1and the * intramolecular electron transition is

accordingly much higher. Furthermore, hydrogen bonds and packing in 1 increase the

conformational rigidity of chromophore groups [35, 37]. Thus, the emission intensity observed in

complex 1is much stronger.

In summary, three blue luminescent zinc(II) complexes have been synthesized by using

Zn(OAc)22H2O and potentially multidentate Schiff base ligands. The structures of all the three

complexes 1, 2and 3have been determined by single crystal X-ray diffraction. Structural studies

reveal that 1is a mononuclear complex, whereas in dinuclear complexes 2and 3the two Zn(II)

centers are held together by deprotonated Schiff base ligand and acetates. All the synthesized

complexes display intraligand (*) fluorescence, but complex 1 shows a higher emission

intensity than that of the complex 2and 3.

Supplementary material

Crystallographic data (excluding structure factors) for the structural analysis have been

deposited with the Cambridge Crystallographic Data Centre, CCDC 837486, 837487 and 837488.

Copies of this information may be obtained free of charge from The Director, CCDC, 12 Union

Road, Cambridge, CB2 1EZ, UK or Fax: +44 1223 336033; Email: [email protected] or

http://www.ccdc.cam.ac.uk.

Acknowledgement

Financial support by the NSFC (21061009) and Inner Mongolia Autonomous Region

Foundation for Scientific Research Project (2010MS0201) are kindly acknowledged.

References

[1] D. Feng, S. Liu, W. Zhang, P. Sun, F. Ma, C. Zhang, Blue Fluorescence Emission Property of aMetal-Organic Coordination Polymer with One-Dimensional Channels Z. Anorg. Allg. Chem.,

636 (2010) 1133-1136.[2] R. Ghosh, S.H. Rahaman, C.-N. Lin, T.-H. Lu, B.K. Ghosh, Coordination behaviour of


7/22

ACCEP

TED

MANUSCRIPT

ACCEPTED MANUSCRIPT

symmetrical hexadentate N-donor Schiff bases towards zinc(II)pseudohalides: Syntheses, crystal

structures and luminescence, Polyhedron, 25 (2006) 3104-3112.

[3] K.-Y. Ho, W.-Y. Yu, K.-K. Cheung, C.-M. Che, A blue photoluminescent [Zn(L)(CN)2] (L =

2,2'-dipyridylamine) material with a supramolecular one-dimensional chain structure, Chem.

Commun., (1998) 2101-2102.

[4] K.-Y. Ho, W.-Y. Yu, K.-K. Cheung, C.-M. Che, Blue luminescent zinc(II) complexes with

polypyridylamine ligands: crystal structures and luminescence properties, J. Chem. Soc., Dalton

Trans., (1999) 1581-1586.

[5] R. Pandey, P. Kumar, A.K. Singh, M. Shahid, P.Z. Li, S.K. Singh, Q. Xu, A. Misra, D.S. Pandey,

Fluorescent zinc(II) complex exhibiting "on-off-on" switching toward Cu2+and Ag+ ions, Inorg.

Chem., 50 (2011) 3189-3197.

[6] Y. Xu, J. Meng, L. Meng, Y. Dong, Y. Cheng, C. Zhu, A highly selective fluorescence-based

polymer sensor incorporating an (R,R)-salen moiety for Zn(2+) detection, Chem.--Eur. J., 16

(2010) 12898-12903.

[7] X.-Y. Yu, L. Ye, X. Zhang, X.-B. Cui, J.-P. Zhang, J.-Q. Xu, Q. Hou, T.-G. Wang, Fluorescentmetal-organic polymers of zinc and cadmium from hydrothermal in situ acylation reaction, Dalton

Trans., 39 (2010) 10617-10625.

[8] C. Diaz, P. Mukherjee, M.G.B. Drew, M. Estrader, A. Ghosh, Influence of counter anions on the

structures and magnetic properties of trinuclear Cu(II) complexes containing a mu(3)-OH core and

Schiff base ligands, Inorg. Chim. Acta, 361 (2008) 161-172.

[9] P. Zhao, H. Wang, J. Song, L. Lu, Synthesis, structures, and property studies on Zn(II), Ni(II), and

Cu(II) complexes with a Schiff base ligand containing thiocarbamide group, Struct. Chem., 21

(2010) 977-987.

[10] K. Isele, F. Gigon, A.F. Williams, G. Bernardinelli, P. Franz, S. Decurtins, Synthesis, structure and

properties of {M4O4} cubanes containing nickel(II) and cobalt(II), Dalton Trans., (2007)

332-341.

[11] T.K. Karmakar, S.K. Chandra, J. Ribas, G. Mostafa, T.H. Lu, B.K. Ghosh, Synthesis, structure and

magnetism of a new dicubane-like ferromagnetic tetranuclear nickel cluster containing versatile

azido-only bridges and a bis(bidentate) Schiff base blocker, Chem. Commun., (2002) 2364-2365.

[12] J. Chakraborty, S. Thakurta, G. Pilet, D. Luneau, S. Mitra, A novel tetra(3-phenoxo) bridged

copper(II) Schiff base complex containing a Cu4O4cubane core: Synthesis, structural aspects and

magneto-structural correlations, Polyhedron, 28 (2009) 819-825.

[13] Y. Morishita, T. Kogane, T. Nogami, T. Ishida, Double half-cubane copper(II) complexes available

from copper(II) 1,1,1,5,5,5-hexafluoropentane-2,4-dionate dissolved in formamides, Dalton Trans.,(2006) 4438-4443.

[14] H.-C. Fang, X.-Y. Yi, Z.-G. Gu, G. Zhao, Q.-Y. Wen, J.-Q. Zhu, A.-W. Xu, Y.-P. Cai, Construction

of Low-Dimensional Cadmium Compounds with N2O/N2S Donor Tridentate Schiff Base Ligands,

Cryst. Growth Des., 9 (2009) 3776-3788.

[15] H.-C. Fang, J.-Q. Zhu, L.-J. Zhou, H.-Y. Jia, S.-S. Li, X. Gong, S.-B. Li, Y.-P. Cai, P.K.

Thallapally, J. Liu, G.J. Exarhos, pH-Dependent Assembly and Conversions of Six

Cadmium(II)-Based Coordination Complexes, Cryst. Growth Des., 10 (2010) 3277-3284.

[16] S. Mitra, A. Majumder, G.M. Rosair, A. Mallick, N. Chattopadhyay, Synthesis, structures and

fluorescence of nickel, zinc and cadmium complexes with the N,N,O-tridentate Schiff base

N-2-pyridylmethylidene-2-hydroxy-phenylamine, Polyhedron, 25 (2006) 1753-1762.


8/22

ACCEP

TED

MANUSCRIPT

ACCEPTED MANUSCRIPT

[17] Steady state fluorescence measurements for all the complexes and the Schiff base ligands at room

temperature (298 K) were performed using a Spex fluorolog II spectrofluorimeter. The solutions

(ca. 210-5M) of the ligands and complexes 1, 2and 3were prepared in a 2:1 methanolwater

mixed solvent ratio and the OD for each of the solutions at the wavelength for fluorescence

excitation was recorded. The fluorescence quantum yields of the Schiff base ligands and its zinc(II)

complexes were determined using quinine sulfate as the reference with a known R of 0.7 in

methanol (0.1 M). The complexes, along with ligands and the reference compound, were excited

at 390 nm and the emission spectra were recorded from 400 to 750 nm. The area of the emission

spectrum was integrated using the software available in the instrument and the quantum yield was

calculated according to the following equation:

S/ R= [AS/AR] [(OD)R/ (OD)S] [S2/ R

2]

Here Sand Rare the fluorescence quantum yields of the sample and reference, respectively, A Sand ARare the areas under the fluorescence spectra of the sample and the reference, respectively.

(OD)Sand (OD)Rare the respective optical densities of the sample and the reference solution atthe wavelength of excitation, and Sand Rare the values of refractive index for the respective

solvents used for the sample and reference [37].

[18] C. Basu, S. Chowdhury, R. Banerjee, H. Stoeckli Evans, S. Mukherjee, A novel blue luminescent

high-spin iron(III) complex with interlayer O-H...Cl bridging: Synthesis, structure and

spectroscopic studies, Polyhedron, 26 (2007) 3617-3624.

[19] X.-X. Zhou, H.-C. Fang, Y.-Y. Ge, Z.-Y. Zhou, Z.-G. Gu, X. Gong, G. Zhao, Q.-G. Zhan, R.-H.

Zeng, Y.-P. Cai, Assembly of a Series of Trinuclear Zinc(II) Compounds with N 2O2Donor

Tetradentate Symmetrical Schiff Base Ligand, Cryst. Growth Des., 10 (2010) 4014-4022.

[20] S. Khatua, S.H. Choi, J. Lee, K. Kim, Y. Do, D.G. Churchill, Aqueous fluorometric and

colorimetric sensing of phosphate ions by a fluorescent dinuclear zinc complex, Inorg. Chem., 48

(2009) 2993-2999.

[21] T. Kawamoto, M. Nishiwaki, Y. Tsunekawa, K. Nozaki, T. Konno, Synthesis and Characterization

of Luminescent Zinc(II) and Cadmium(II) Complexes with N,S-Chelating Schiff Base Ligands,

Inorg. Chem., 47 (2008) 3095-3104.

[22] Y.-S. Song, B. Yan, Z.-X. Chen, Synthesis of two luminescent coordination polymers based on

self-assembly of Zn(II) with polycarboxylic acids ligands and heteroaromatic N-donor, Appl.

Organomet. Chem., 20 (2006) 44-50.

[23] S. Naskar, S. Naskar, H.M. Figgie, W.S. Sheldrick, S.K. Chattopadhyay, Synthesis, crystal

structures and spectroscopic properties of two Zn(II) Schiff's base complexes of pyridoxal,Polyhedron, 29 (2010) 493-499.

[24] The Schiff base ligands HL1, HL2and HL3were synthesized by a condensation reaction between

3-methoxysalicylaldehyde and the corresponding amino alcohol (2-Amino-1-butanol,

2-Amino-2-methyl-1-propanol and 1-Amino-2-propanol, respectively) under refluxing in the

methanol solution. The resulting orange yellow solution containing the required product was used

without further purification.

[25] Synthesis of 1: A methanol solution (10 mL) of Schiff base ligand HL1(0.5 mmol 0.112 g) was

added to a methanol solution (5mL) containing NaOH (0.5 mmol 0.02 g), and then

Zn(OAc)22H2O (0.5 mmol 0.11 g) in ethanol (10 mL) was added. The mixture was stirred for 1 hat room temperature. After being filtered, the resulting light yellow solution was standing at


9/22

ACCEP

TED

MANUSCRIPT

ACCEPTED MANUSCRIPT

ambient temperature to allow for solvent evaporation. After 10 days, the well-shaped colorless

crystals of complex 1 were obtained. The crystals were isolated by filtration and air-dried. Yield:

46% (based on zinc acetate dihydrate). Elemental analysis (%), Anal. Calc. for C 24H32N2O6Zn: C,

56.58; H, 6.29; N, 5.50. Found: C, 56.08; H, 6.34; N, 5.15. IR (KBr, cm1): 3445 (s, br), 2960 (m),1621 (s, sh), 1469 (s, sh), 1312 (w), 1242 (s, sh), 1080 (s, sh) (w, weak; m, medium; s, strong; br,

broad; sh, sharp).

[26] Synthesis of 2: A methanol solution (10 mL) of Schiff base ligand HL2(0.5 mmol 0.112 g) was

added to 4,4-bipyridine (0.5 mmol 0.096 g) in ethanol (10 ml), then a mixture of Zn(OAc) 22H2O(0.5 mmol 0.11 g) in methanol (10 mL) was added. The mixture was stirred for 1 h at room

temperature. After being filtered, the resulting light yellow solution was standing at ambient

temperature to allow for solvent evaporation. After 10 days, the colorless crystals of compound 2

were obtained. The crystals were isolated by filtration and air-dried. Yield: 44%. Elemental

analysis (%), Anal. Calc. for C18NO9Zn2: C, 40.83; H, 4.72; N, 2.65. Found: C, 41.12; H, 4.38; N,

2.70. IR (KBr, cm-1): 3126 (s, br), 2979 (m, sh), 1634 (s, sh), 1434 (s, sh), 1300 (m), 1219 (m, sh),

1168 (m), 1044 (w).[27] Synthesis of 3: This compound was prepared using the same procedure as that described above for

the synthesis of complex 2 but using HL3 in place of HL2. Finally, the product as colorless

block-shaped crystals was obtained after 10 days. The crystals were isolated by filtration and

air-dried. Yield: 43%. Elemental analysis (%), Anal. Calc. for C17H22NO9Zn2: C, 39.69; H, 4.28; N,

2.72. Found: C, 40.21; H, 4.36; N, 3.01. IR (KBr, cm-1): 3191 (s, br), 2939 (m, sh), 1622 (s, br),

1401 (s, sh), 1306 (m), 1217 (m), 1036 (w).

[28] Crystallographic data were collected at temperature of 298 K (for 1) and 293 K (for 2and 3) on a

Bruker ApexII CCD diffractometer with graphite-monochromated Mo-K radiation (=0.71073

). Data processing was accomplished with the SAINT processing program [34]. The structure

was solved by direct method and refined on F2by full-matrix least squares using SHELXTL [36].

The locations of metal atoms were easily determined, and the oxygen, nitrogen, and carbon atoms

were subsequently determined from the difference Fourier maps. The non-hydrogen atoms were

refined anisotropically. The hydrogen atoms were introduced in calculated positions and refined

with a fixed geometry with respect to their carrier atoms.

[29] W.B. Lin, O.R. Evans, R.G. Xiong, Z.Y. Wang, G.K. Wong, Crystal engineering of acentric

diamondoid metal-organic coordination networks, Angew. Chem., Int. Ed., 38 (1999) 536-538.

[30] O.R. Evans, W. Lin, Crystal Engineering of Nonlinear Optical Materials Based on Interpenetrated

Diamondoid Coordination Networks, Chem. Mater., 13 (2001) 2705-2712.

[31] W. Lin, L. Ma, O.R. Evans, NLO-active zinc(II) and cadmium(II) coordination networks with8-fold diamondoid structures, Chem. Commun., (2000) 2263-2264.

[32] D. Das, B.G. Chand, K.K. Sarker, J. Dinda, C. Sinha, Zn(II)-azide complexes of diimine and

azoimine functions: Synthesis, spectra and X-ray structures, Polyhedron, 25 (2006) 2333-2340.

[33] G.-X. Liu, Y.-Y. Xu, Y. Wang, S. Nishihara, X.-M. Ren, Three zinc(II) complexes constructed from

aromatic dicarboxylate and 1,4-bis((2-(pyridin-2-yl)-1H-imidazol-1-yl)methyl)benzene: Syntheses,

crystal structures and luminescent properties, Inorg. Chim. Acta, 363 (2010) 3932-3938.

[34] G. Sheldrick, Acta Crystallographica Section A, 64 (2008) 112-122.

[35] Y. Chen, X.-J. Zhao, X. Gan, W.-F. Fu, Zinc(II) complexes with 1,8-naphthyridine-based ligand:

Crystal structures and luminescent properties, Inorg. Chim. Acta, 361 (2008) 2335-2342.

[36] G. Sheldrick, Acta Crystallographica Section A, 64 (2008) 112-122.


10/22

ACCEP

TED

MANUSCRIPT

ACCEPTED MANUSCRIPT

[37] S. Basak, S. Sen, S. Banerjee, S. Mitra, G. Rosair, M.T.G. Rodriguez, Three new pseudohalide

bridged dinuclear Zn(II) Schiff base complexes: Synthesis, crystal structures and fluorescence

studies, Polyhedron, 26 (2007) 5104-5112.


11/22

ACCEP

TED

MANUSCRIPT

ACCEPTED MANUSCRIPT

Scheme: Structure of the ligands L1, L2, and L3.

Fig. 1 Perspective view of structure of [Zn(L1)2] (1). Hydrogen atoms are omitted for clarity.

Fig. 2 Crystal structure of [Zn(L1)2] (1) showing the hydrogen bonding interactions between the

phenolic hydroxyl and the alcohols hydroxyl of (L1).

Fig. 3Perspective view of structure of [Zn2L2(OAc)3](2). Hydrogen atoms are omitted for clarity.

Fig. 4Fluorescence spectra of complexes 1, 2and 3in methanol-water (exc= 390 nm).


12/22

ACCEP

TED

MANUSCRIPT

ACCEPTED MANUSCRIPT

Table 1

Crystal and refinement data of compound 1-3.

Compound 1 2 3

Empirical formula C24H32N2O6Zn C18H25NO9Zn2 C17H22NO9Zn2

Formula weight 509.89 530.13 515.10Crystal syst Monoclinic Monoclinic Monoclinic

Space group P2(1) P2(1)/n P2(1)/c

Unit cell dimensions

a= 8.1967(6)

b= 7.4081(5)

c= 20.2096(14)

= 91.437 (10)

a= 8.8010(18)

b= 25.801(5)

c= 10.009(2)

= 111.29(3)

a= 13.403(3)

b= 8.8910(18)

c= 17.634(4)

= 95.85(3)

V 3 1226.78(15) 2117.8(7) 2090.4(8)

Z 2 4 4

T(K) 298 293 293

, mm-1 1.042 2.315 2.342F(000) 536 1088 1052

Limiting indices

9h9

8k8

15l24

11h11

33k33

13l12

17h17

11k11

23l23

(deg) 2.49-25.01 1.58-27.89 2.32-28.27

GOFon F2 1.049 1.034 1.046

R1, wR2R1= 0.0756

wR2= 0.1599

R1= 0.0296

wR2= 0.0686

R1= 0.0269

wR2= 0.0745


13/22

ACCEP

TED

MANUSCRIPT

ACCEPTED MANUSCRIPT

Table 2

Bond lengths [] and angles [] for compound 1-3.

Complex 1

Zn(1)-O(2) 1.942(6) Zn(1)-N(1) 1.993(8)

Zn(1)-O(5) 1.949(6) Zn(1)-N(2) 2.026(7)O(2)-Zn(1)-O(5) 109.9(3) O(2)-Zn(1)-N(2) 106.7(3)

O(2)-Zn(1)-N(1) 94.1(3) O(5)-Zn(1)-N(2) 95.1(3)

O(5)-Zn(1)-N(1) 111.1(3) N(1)-Zn(1)-N(2) 138.7(3)

Complex 2

Zn(2)-O(3) 2.032(1) Zn(1)-N(1) 2.032(2)

Zn(2)-O(4) 2.029(1) Zn(1)-O(1) 2.170(1)

Zn(2)-O(5) 2.379(2) Zn(1)-O(2) 1.974(1)

Zn(2)-O(6) 2.360(2) Zn(1)-O(7) 2.044(1)

Zn(2)-O(7) 1.996(1) Zn(1)-O(8) 1.965(1)

Zn(2)-O(9) 2.027(1)O(8)-Zn(1)-N(1) 119.73(6) O(9)-Zn(2)-O(3) 101.68(6)

O(2)-Zn(1)-N(1) 126.33(6) O(4)-Zn(2)-O(3) 99.43(6)

O(8)-Zn(1)-O(7) 100.24(6) O(7)-Zn(2)-O(6) 73.37(5)

O(2)-Zn(1)-O(7) 95.67(6) O(4)-Zn(2)-O(6) 87.67(5)

N(1)-Zn(1)-O(7) 88.55(7) O(3)-Zn(2)-O(6) 92.73(6)

O(8)-Zn(1)-O(1) 88.93(6) O(7)-Zn(2)-O(5) 101.96(6)

O(2)-Zn(1)-O(1) 91.77(6) O(9)-Zn(2)-O(5) 91.55(6)

N(1)-Zn(1)-O(1) 76.57(7) O(4)-Zn(2)-O(5) 59.03(5)

O(7)-Zn(2)-O(9) 97.68(6) O(6)-Zn(2)-O(5) 77.58(5)O(9)-Zn(2)-O(4) 97.03(6)

Complex 3

Zn(2)-O(2) 2.016(1) Zn(1)-N(1) 2.032(2)

Zn(2)-O(3) 2.306(1) Zn(1)-O(1) 2.210(2)

Zn(2)-O(4) 2.365(2) Zn(1)-O(2) 2.082(1)

Zn(2)-O(5) 2.049(2) Zn(1)-O(7) 1.954(2)

Zn(2)-O(6) 2.019(2) Zn(1)-O(8) 1.987(1)

Zn(2)-O(9) 2.057(1)

O(7)-Zn(1)-N(1) 130.40(7) O(6)-Zn(2)-O(5) 92.11(6)

O(8)-Zn(1)-N(1) 115.42(7) O(2)-Zn(2)-O(9) 93.55(6)O(7)-Zn(1)-O(2) 101.45(6) O(6)-Zn(2)-O(9) 102.46(6)

O(8)-Zn(1)-O(2) 95.70(5) O(5)-Zn(2)-O(9) 97.61(6)

N(1)-Zn(1)-O(2) 87.93(6) O(2)-Zn(2)-O(3) 74.34(5)

O(7)-Zn(1)-O(1) 85.55(6) O(5)-Zn(2)-O(3) 90.18(6)

O(8)-Zn(1)-O(1) 95.35(6) O(9)-Zn(2)-O(3) 93.66(6)

N(1)-Zn(1)-O(1) 76.38(6) O(2)-Zn(2)-O(6) 99.88(6)


14/22

ACCEP

TED

MANUSCRIPT

ACCEPTED MANUSCRIPT

Table 3

Photophysical parameters of complexes 1, 2and 3in MeOH/H2O (2:1) at 298 K; excitation at 390 nm;

reference compound is quinine sulfate (R= 0.7 in methanol)

Complex Abs.(max), nm

Emission(max), nm

Quantum yield ()

1 397 469 0.15432 398 498 0.0142

3 424 487 0.0097


15/22

ACCEP

TED

MANUSCRIPT

ACCEPTED MANUSCRIPT

Figure 1


16/22

ACCEP

TED

MANUSCRIPT

ACCEPTED MANUSCRIPT

Figure 2


17/22

ACCEP

TED

MANUSCRIPT

ACCEPTED MANUSCRIPT

Figure 3


18/22

ACCEP

TED

MANUSCRIPT

ACCEPTED MANUSCRIPT

Figure 4


19/22

ACCEP

TED

MANUSCRIPT

ACCEPTED MANUSCRIPT

Scheme 1


20/22

ACCEP

TED

MANUSCRIPT

ACCEPTED MANUSCRIPT

Graphical abstract


21/22

ACCEP

TED

MANUSCRIPT

ACCEPTED MANUSCRIPT

Graphical abstract synopsis

Three blue luminescent zinc(II) complexes have been synthesized by using Zn(OAc) 22H2O andpotentially multidentate Schiff base ligands. The structures of all the three complexes 1, 2and 3have been determined by single crystal X-ray diffraction.


22/22

ACCEP

TED

MANUSCRIPT

ACCEPTED MANUSCRIPT

Highlights

Three zinc(II) complexes with blue luminescent which display intraligand (*) fluorescencehas been synthesized. The fluorescence intensity is greatly enhanced by the coordination ofZn(II) with Schiff base ligands. The supramolecular interactions of hydrogen bonds and packing in the complex increase the conformational rigidity of chromophore groups and thus theemission intensity observed in the complexis much stronger.

vanilina_aminoalcooli

Documents