transport studies of some 1:1 copper(i) perchlorate complexes in acetonitrile-dimethylsulphoxide...

Z. Phys. Chem. 225 (2011) 69–77 / DOI 10.1524/zpch.2011.5527© by Oldenbourg Wissenschaftsverlag, München

Transport Studies of Some 1 : 1 Copper(I)Perchlorate Complexes inAcetonitrile-Dimethylsulphoxide Mixtures

By Dip Singh Gill∗, Dilbag Singh Rana, and Surinder Pal Jauhar

Department of Chemistry, Panjab University, Chandigarh 160014, India

(Received November 25, 2009; accepted in revised form May 5, 2010)

Transport Studies / Solvation / Acetonitrile / Dimethylsulphoxide

Solvation behaviour of some copper(I) perchlorate complexes has been investigated in binarymixtures of acetonitrile (AN) and dimethylsulphoxide (DMSO) containing 1.0, 0.8, 0.6, 0.4, 0.2and 0 mol fraction of AN at 298 K by molar conductances and viscosity measurements. Theconductance data have been analyzed by using the Shedlovsky method to calculate limiting molarconductance (Λo) and the viscosity data by the Jones–Dole equation to evaluate viscosity B-coefficients of various salts. Limiting ion conductances (λo

i ), solvated radii (ri) and ionic viscosityB± coefficients in all solvent systems have been evaluated using Gill’s modification based onBu4NBPh4 as a reference electrolyte. The studies show that all copper(I) complexes are solvatedand the extent of solvation is stronger in AN and AN rich regions than in DMSO and DMSO richregions. The ClO4

− ion is poorly solvated in AN + DMSO mixtures. The viscosity results are ingood agreement with the results obtained from the conductance studies.

1. IntroductionStudies of the transport properties of electrolytes in different solvent media are ofgreat importance for obtaining information on ion-association and ion-solvation be-haviour of ions in solution. Highly ionic copper(I) complexes like copper(I) per-chlorates tetraacetonitrile [Cu(CH3CN)4]ClO4, copper(I) perchlorates tetrabenzonitrile[Cu(C6H5CN)4]ClO4 are unstable in water and large number of organic solvents andphysicochemical studies of copper(I) salts are limited in mixed solvents. Though someinvestigations [1–5] of the behaviour of these copper complexes in pure acetonitrile andbinary mixtures of acetonitrile with some other solvents using conductance, viscosity,ultrasound velocity, partial molar volume, partial molal adiabatic compressibility and63Cu NMR studies have been carried out, yet such studies are still lacking in the binarymixtures of AN with DMSO. In continuation with our previous studies [6–8], in thispaper we report conductance and viscosity measurements of some copper(I) complexions in AN + DMSO mixtures consisting of significantly different relative permittivity(εDMSO = 46.7 and εAN = 36.0).

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70 D. S. Gill et al.

Table 1. Density (ρo), viscosity (ηo) and relative permittivity (εo) of AN + DMSO mixtures at 298 K.

Mol fraction of AN ρo/g cm−3 ηo/cP εo

1.0 0.77685 0.341 36.00.8 0.85743 0.521 38.30.6 0.92947 0.839 40.50.4 0.99268 1.157 41.50.2 1.04610 1.400 44.00.0 1.09601 1.990 46.7

2. Experimental

AN and DMSO (both 99.5% from E. Merck) were purified as reported [9]. The purifiedsolvents had the densities 0.77685 and 1.096 g cm−3, viscosities 0.341 and 1.990 cP,respectively which agree well with the literature values [9]. Tetraacetonitrile cop-per(I) perchlorate [Cu(CH3CN)4]ClO4 was prepared by the reduction of copper(II)perchlorate hexahydrate by copper metal powder in warm AN, following the methodreported by Hathaway et al. [10] and Gill et al. [11]. Benzonitrile 99% (Lancaster),phenanthroline 99.5% (Löba), dimethylphenanthroline 99% (Löba) and thiourea 99%(New India Chemical Enterprises, Cochin) were used in the present work for thepreparation of copper(I) perchlorate complexes. Tetrabenzonitrile copper(I) perchlo-rate [Cu(C6H5CN)4]ClO4 was prepared by heating [Cu(CH3CN)4]ClO4 with requiredamount of benzonitrile in CH2Cl2, bis(1,10-phenanthroline) copper(I) perchlorate[Cu(Phen)2]ClO4 was prepared by mixing warm solution of 1,10-phenanthroline ligandwith [Cu(CH3CN)4]ClO4 in acetonitrile in required proportion, bis(2,9-dimethyl-1,10-phenanthroline) copper(I) perchlorate [Cu(DMPhen)2]ClO4was prepared by mixingwarm solution of 2,9-dimethyl-1,10-phenanthroline ligand with [Cu(CH3CN)4]ClO4 inacetonitrile in required proportion and precipitated out by adding toluene. Tetrathioureacopper(I) perchlorate [Cu(TU)4]ClO4 and bis(2,2′-bipyridyl) copper(I) perchlorate[Cu(Bipy)2]ClO4was prepared by mixing hot solution of thiourea and 2,2′-bipyridylligand respectively with [Cu(CH3CN)4]ClO4 in acetonitrile in required proportion.Tetrabutylammonium tetraphenylborate and tetrabutylammonium perchlorate were pre-pared and dried by the method already reported [12]. The purity of salts was checked bytheir elemental, chemical and spectroscopic analysis.

Molar conductances of various salts were measured at 1000 Hz frequency at298.15±0.01 K with a digital conductivity meter (Model NDC-732, Naina Electronics,Chandigarh). The details of the experimental procedure of conductance measurementswere same as reported earlier [12,13]. The overall accuracy of the conductance meas-urements was found to be ±0.2%.

Viscosity measurements were made by using Ubbelohde suspended level viscometerwith flow time of 329 s for water at 298 K. The viscometer was calibrated by the methodreported earlier [14]. The details of the experimental procedure of viscosity measure-ments were the same as reported earlier [14]. The reproducibility of the viscosity meas-urements was better than ±0.1%.



Transport Studies of Some 1 : 1 Cu(I) Perchlorate Complexes in AN-DMSO Mixtures 71

Densities of solvent mixtures and solutions were measured using an AntonPaar Digital Density Meter Model-60 and calibrated cell with reproducibility of±0.00001 g cm−3. Relative permittivities were measured at 2 MHz frequency usingRadelkis Hungury OH-301 dielectrometer. The experimentally measured physical pa-rameters of binary mixtures of AN + DMSO used for analysis of data are reported inTable 1.

3. Results and discussion

3.1 Molar conductance measurements

Molar conductances (Λ) of Bu4NBPh4, Bu4NClO4, [Cu(CH3CN)4]ClO4, [Cu(C6H5

CN)4]ClO4, [Cu(Phen)2]ClO4, [Cu(DMPhen)2]ClO4, [Cu(TU)4]ClO4, and [Cu(Bipy)2]ClO4 have been measured in the concentration range (1–125)×10−4 mol dm−3 in ANand DMSO binary mixtures containing 1.0, 0.8, 0.6, 0.4, 0.2 and 0 mol fraction of ANat 298 K. The conductance results have been analyzed by a least square treatment usingPentium IV PC and following the Shedlovsky method [15] to evaluate limiting molarconductances (Λo) of the electrolytes. The Λo values so obtained for different salts arereported in Table 2.

Since, the accuracy of our present conductance measurements is not better than±0.2%, the use of other extended conductance equations which demand accuracy muchbetter ±0.1% was not thought worthwhile to use. It is known in the literature that allconductance equations (extended or semi empirical) after analysis give almost same Λo

values but different KA values for electrolytes. Since the main purpose of the presentstudies was to study the solvation of ions which is completely based on Λo valuesand not on KA values of the electrolytes, therefore, the analysis of the data by theShedlovsky method was of equal precision for calculating limiting ion conductances(λo

i ) and hence solvated radii of ions (r i). The Λo values for some of these salts in AN al-ready available in the literature are reported in parentheses for comparison with presentvalues. A good agreement has been found between the present values and the literaturevalues [16–19].

3.1.1 Limiting ion conductances (λ◦i )

The limiting ionic molar conductances (λo±) have been calculated using Bu4NBPh4 as

reference electrolyte with the help of the following equations

λo(Bu4N+)

λo(Ph4B−)= 5.35− (0.0103ε+ ry)

5.00− (0.0103ε+ ry), (1)

Λo(Bu4NBPh4) = λo(Bu4N+)+λo(Ph4B−) . (2)

The limiting ionic molar conductances for Bu4N+ and Ph4B− ions are obtained fromthe above equations, and these values have been used to calculate limiting ionic mo-lar conductances of all other ions from Λo values on the basis of Kohlrausch’s law ofindependent migration of ions. The λ◦

i values for all ions are recorded in Table 3.




Table 2. Λo values for some salts at different mol fraction of AN in AN + DMSO binary mixtures at298 K.

Salt Λo (S cm2 mol−1)1.0 0.8 0.6 0.4 0.2 0

Bu4NBPh4 119.91 78.57 49.71 36.70 30.94 22.24(119.8)a

Bu4NClO4 165.62 112.75 74.32 57.47 49.17 36.12(164.8)b

[Cu(CH3CN)4]ClO4 168.13 114.28 75.30 58.79 52.64 39.84(168.4)c

[Cu(C6H5CN)4]ClO4 167.80 115.56 76.97 60.15 52.74 39.87[Cu(DMPhen)2]ClO4 152.90 105.21 69.93 54.54 47.33 35.33

(155.6)d

[Cu(Phen)2]ClO4 155.0 106.70 70.93 55.33 48.07 35.93[Cu(TU)4]ClO4 167.70 115.46 76.87 60.05 52.64 39.77[Cu(Bipy)2]ClO4 160.80 110.12 73.23 57.15 49.81 37.37

a Ref. [16]; b Ref. [17]; c Ref. [18]; d Ref. [19].

3.1.2 Actual radii (ri) for ions in solution

To understand the solvation behaviour of different ions, the solvated radii (r i) for vari-ous ions have been calculated using Gill’s modification of Stokes law [20].

r i = |Z| F2

6πηNλoi

+0.0103ε+ ry (3)

where r i is the actual radius of ion in solution, ε is the relative permittivity of themedium, ry is the adjustable parameter and all other symbols have their usual signif-icance. For associated and hydrogen bonded solvents ry has been recommended as0.113 nm and for non-associated or dipolar aprotic solvents as 0.085 nm [20]. Since inthe present work dipolar aprotic solvents and their binary mixtures have been used assolvent systems, therefore ry has been used as 0.085 nm.

Using λ◦i values, the r i values for various ions have been calculated in different sol-

vent systems and are also reported in Table 3. The inspection of Table 3 shows that,tetrabutylammonium and tetraphenylborate ions are not solvated because they have theconstant r i values in all solvent mixtures and these constant values are equal to theircrystallographic radii (rc = 0.50 nm and ra = 0.535 nm respectively). These two ionsare not solvated in many dipolar aprotic solvents [20] due to their large size. The anionsare very less solvated. In the AN rich region, solvated radii for the copper(I) complexions are relatively larger and decease with decrease in AN composition in the mixtureindicating that the AN molecules from the solvation sphere of copper(I) ions are sharplyreplaced by the DMSO molecules as the DMSO composition increases.

3.2 Viscosity measurements

Viscosities of Bu4NBPh4, Bu4NClO4, [Cu(CH3CN)4]ClO4, [Cu(TU)4]ClO4, [Cu(C6H5

CN)4]ClO4, [Cu(Phen)2]ClO4, [Cu(DMPhen)2]ClO4, and [Cu(Bipy)2]ClO4 have been




Tabl

e3.

Lim

iting

ion

cond

ucta

nce

λo i

(Scm

2m

ol−1

)an

dso

lvat

edra

dii

r i(n

m)

valu

esfo

rso

me

ions

atdi

ffer

ent

mol

frac

tion

ofA

Nin

AN

+D

MSO

mix

ture

sat

298

K.

Ion

1.0

0.8

0.6

0.4

0.2

0λ

o ir i

λo i

r iλ

o ir i

λo i

r iλ

o ir i

λo i

r i

Bu 4

N+

62.6

10.

5141

.06

0.51

26.0

00.

5119

.21

0.51

16.2

10.

5111

.67

0.51

[Cu(

CH

3C

N) 4

]+65

.12

0.49

42.5

90.

5026

.98

0.50

20.5

30.

4919

.68

0.45

15.3

90.

43[C

u(Ph

en) 2

]+51

.99

0.58

35.0

10.

5822

.61

0.57

17.0

70.

5615

.11

0.54

11.4

80.

52[C

u(D

MP

hen)

2]+

49.8

90.

6033

.52

0.60

21.6

10.

5916

.28

0.58

14.3

70.

5610

.88

0.54

[Cu(

TU

) 4]+

64.6

90.

4943

.77

0.49

28.5

50.

4821

.79

0.47

19.6

80.

4515

.32

0.43

[Cu(

Bip

y)2]+

57.7

90.

5438

.43

0.54

24.9

10.

5318

.89

0.52

16.8

50.

5012

.92

0.48

[Cu(

C6H

5C

N) 4

]+64

.79

0.49

43.8

70.

4928

.65

0.48

21.8

90.

4719

.78

0.45

15.4

20.

43C

lO4−

103.

010.

3671

.69

0.35

48.3

20.

3438

.26

0.33

32.9

60.

3324

.45

0.33

BPh

4−

57.3

00.

5437

.51

0.55

23.7

10.

5517

.49

0.55

14.7

30.

5510

.57

0.55




measured in the AN + DMSO binary mixtures containing 1.0, 0.8, 0.6, 0.4, 0.2 and0 mol fraction of AN in the concentration range (10–540)×10−4 mol dm−3. The viscos-ity data have been analyzed using the Jones–Dole [21] equation in the form

η

η0

= 1+ AC1/2 + BC (4)

where η0 and η are the viscosities of the solvent and solution, respectively, C is the mo-lar concentration of the electrolyte and, A and B are the constants characteristic of thesolvent and the salt, respectively. The plots of (η−η0)/η0C1/2 = ψ against C1/2 wereconstructed and found to be linear over the whole concentration range studied. TheA and B parameters for the electrolytes were obtained directly from the plots by theleast-squares method and are reported in Tables 4 and 5. The limiting theoretical valuesof Aη were also calculated using the Falkenhagen–Vernon equation [22] (Eq. 5) and arealso reported in Table 4 for comparison.

Aη = 0.2577Λ◦η0 (ε0T )

1/2λ◦

1λ◦2

[1−0.6863

(λ◦

1 −λ◦2

Λ◦

)2]

(5)

where Λo = λo1 +λo

2, λo1 and λo

2 are the limiting ion conductances, ηo and εo are the vis-cosity and relative permittivity of the solvent or solvent mixture, respectively and T isthe absolute temperature. The agreement between A and Aη values in Table 4 is fairlygood for some of the salts. In some cases, however, the experimental A coefficients aretwo to three times larger than the Aη values. Some other workers have also observedthat the experimental A coefficients evaluated from the plots of ψ against C1/2 in nonaqueous solvents were different from the Aη values [23].

Viscosity B-coefficients for all the electrolytes in AN + DMSO mixtures are largeand positive. In dipolar aprotic solvents, the structure breaking contribution is negli-gible with the result that the B-coefficients are positive and large. A comparison ofpresent B-values cannot be made in present solvent system as no such data are alreadyavailable in literature, however our values in pure AN are in good agreement with theliterature values [24–26].

The B-coefficients of the salts are split into the contributions of individual ionsusing Bu4NBPh4 as reference electrolyte on the basis of the following equations

B[Ph4B−]B[Bu4N+] = r3[Ph4B−]

r3[Bu4N+] = (5.35)3

(5.00)3, (6)

B[Bu4N+]+ B[BPh4−] = B[Bu4NBPh4] (7)

where B[Bu4NBPh4] is observed B-coefficient for Bu4NBPh4. Using the Eqs. (5) and(6), the ionic B± coefficients of Bu4N+ and BPh4

− are used to calculate viscosity B-coefficients of all other ions in AN, DMSO and AN + DMSO mixtures and are reportedin Table 6. Inspection of Table 6 shows that B± values for Bu4N+, BPh4

− and ClO4−

in AN, DMSO and AN + DMSO mixtures remain practically constant indicatingno solvation of these ions. The B+coefficients for [Cu(CH3CN)4]+, [Cu(C6H5CN)4]+,[Cu(Phen)2]+, [Cu(Bipy)2]+, [Cu(TU)4]+ and [Cu(DMPhen)2]+ ions decrease as the




Tabl

e4.

A-c

oeffi

cien

tsof

the

Jone

s–D

ole

equa

tion

and

the

corr

espo

ndin

gA

η(d

m3/

2m

ol−1

/2)

valu

esof

the

Falk

enha

gen–

Ver

non

equa

tion

for

som

esa

ltsat

diff

eren

tm

olfr

actio

nof

AN

inA

N+

DM

SOm

ixtu

res

at29

8K

.

Salt

1.0

0.8

0.6

0.4

0.2

010

2A

102A

η10

2A

102A

η10

2A

102A

η10

2A

102A

η10

2A

102A

η10

2A

102A

η

Bu 4

NB

Ph4

1.11

2.43

2.11

2.36

3.11

2.25

4.11

2.18

5.14

2.08

5.85

1.97

Bu 4

NC

lO4

1.03

1.87

2.04

1.77

3.02

1.65

4.02

1.56

5.05

1.47

5.74

1.38

[Cu(

CH

3C

N) 4

]ClO

45.

741.

825.

051.

734.

031.

613.

031.

492.

081.

301.

061.

16[C

u(Ph

en) 2

]ClO

45.

952.

115.

281.

964.

261.

813.

241.

692.

221.

551.

221.

40[C

u(D

MP

hen)

2]C

lO4

5.96

2.17

5.27

2.02

4.28

1.87

3.25

1.75

2.26

1.60

1.23

1.45

[Cu(

TU

) 4]C

lO4

5.87

1.83

5.16

1.70

4.17

1.55

3.16

1.44

2.17

1.30

1.11

1.16

[Cu(

Bip

y)2]C

lO4

5.98

1.97

5.23

1.85

4.29

1.70

3.27

1.58

2.28

1.44

1.28

1.29

[Cu(

C6H

5C

N) 4

]ClO

45.

891.

835.

161.

704.

121.

553.

181.

432.

171.

291.

191.

16




Table 5. Viscosity B-coefficients for some salts at different mol fraction of AN in AN + DMSO mixturesat 298 K.

Salt B/dm3 mol−1

1.0 0.8 0.6 0.4 0.2 0

Bu4NBPh4 1.35 1.36 1.39 1.40 1.41 1.43(1.35)a

Bu4NClO4 0.84 0.85 0.87 0.89 0.90 0.91(0.81)b

[Cu(CH3CN)4]ClO4 0.77 0.78 0.76 0.76 0.73 0.69(0.77)c

[Cu(Phen)2]ClO4 1.43 1.31 1.18 1.06 0.93 0.81[Cu(DMPhen)2]ClO4 1.45 1.32 1.20 1.07 0.95 0.82[Cu(TU)4]ClO4 1.10 1.02 0.95 0.87 0.80 0.72[Cu(Bipy)2]ClO4 1.41 1.29 1.16 1.04 0.91 0.79[Cu(C6H5CN)4]ClO4 1.10 1.02 0.95 0.87 0.80 0.72

a Ref. [24]; b Ref. [25]; c Ref. [26].

Table 6. Ionic viscosity B-coefficients for some ions at different mol fraction of AN in AN + DMSO mix-tures at 298 K.

Ions (B)±/dm3 mol−1

1.0 0.8 0.6 0.4 0.2 0

Bu4N+ 0.61 0.61 0.63 0.63 0.63 0.65[Cu(CH3CN)4]+ 0.54 0.54 0.53 0.50 0.46 0.43[Cu(Phen)2]+ 1.20 1.07 0.94 0.80 0.66 0.55[Cu(DMPhen)2]+ 1.22 1.08 0.96 0.81 0.68 0.56[Cu(TU)4]+ 0.87 0.78 0.71 0.61 0.53 0.46[Cu(Bipy)2]+ 1.18 1.05 0.92 0.78 0.64 0.53[Cu(C6H5CN)4]+ 0.87 0.78 0.71 0.61 0.53 0.46ClO4

− 0.23 0.24 0.24 0.26 0.27 0.26BPh4

− 0.74 0.75 0.76 0.77 0.78 0.78

mol fraction of DMSO increases in the AN + DMSO binary mixture. As previ-ously reported by compressibility studies [27], DMSO interacts strongly with complexcopper(I) cations forming mixed complexes of the type [Cu(CH3CN)4−x(DMSO)x]+

(x = 1–4) and [Cu(CH3CN)2]+(CH3CN)y (DMSO)z in mixed solvents by replacing theAN molecules.

4. Conclusion

The results obtained from viscosity measurements are similar to those obtained fromconductance measurements which indicate that whereas Bu4N+, Ph4B− and ClO4

− arepoorly solvated and the solvation of copper(I) complex ions is relatively stronger in ANand the AN rich region than in DMSO and the DMSO rich region.




Acknowledgement

Dip Singh Gill and Dilbag Singh Rana thanks UGC, for the award of Emeritus Fellow-ship and Senior Research Fellowship respectively.

References

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1729.4. D. S. Gill, L. Rodehueser, and J. J. Delpuech, J. Chem. Soc. Faraday Trans. 86 (1990) 2847.5. J. Singh, T. Kaur, V. Ali, and D. S. Gill, J. Chem. Soc. Faraday Trans. 90 (1994) 579.6. D. S. Gill, D. Rana, A. Kumari, R. Gupta, and S. P. Jauhar, J. Mol. Liq. 133 (2007) 7.7. D. S. Gill, D. Rana, and R. Gupta, Z. Phys. Chem. 222 (2008) 1039.8. D. S. Gill and D. Rana, Z. Naturforsch. 64a (2009) 269.9. J. A. Riddick, W. B. Bugner, and T. K. Sakano, Organic Solvents, Physical Properties and

Methods of Purification, 4th Ed., Wiley Interscience, New York (1986).10. B. J. Hathaway, D. G. Holah, and J. D. Postlewaite, J. Chem. Soc. (1961) 3215.11. D. S. Gill and J. S. Cheema, Electrochim. Acta. 27 (1982) 1267.12. D. S. Gill, A. N. Sharma, and H. Schneider, J. Chem. Soc. Faraday Trans. 78 (1982) 465.13. D. S. Gill and M. B. Sekhri, J. Chem. Soc. Faraday Trans. I 78 (1982) 119.14. D. S. Gill, H. Anand, A. Kumari, and J. K. Puri, Z. Naturforsch. 59a (2004) 615.15. R. M. Fuoss and T. Shedlovsky, J. Am. Chem. Soc. 71 (1949) 1496.16. A. B. Brown and R. M. Fuoss, J. Phys. Chem. 64 (1960) 1341.17. D. S. Gill, N. Kumari, and M. S. Chauhan, J. Chem. Soc. Faraday Trans. I 81 (1985) 687.18. H. L. Yeager and B. Kratochvil, J. Phys. Chem. 73 (1969) 1963.19. D. S. Gill, K. S. Arora, B. Singh, M. S. Bakshi, and M. S. Chauhan, J. Chem. Soc. Faraday

Trans. 87 (1991) 1159.20. D. S. Gill, J. Chem. Soc., Faraday Trans. I 77 (1981) 751.21. G. Jones and M. Dole, J. Am. Chem. Soc. 51 (1929) 2950.22. J. Falkenhagen and E. L. Vernon, Z. Phys. Chem. 33 (1932) 140.23. N. P. Yao and D. N. Bennion, J. Phys. Chem. 75 (1971) 1729.24. D. S. Gill and B. Singh, J. Chem. Soc. Faraday Trans. I 84 (1988) 4417.25. D. S. Gill, M. S. Chauhan, and M. B. Sekhri, J. Chem. Soc. Faraday Trans. I 78 (1982) 3461.26. D. S. Gill and M. S. Bakshi, J. Chem. Soc. Faraday Trans. I 85 (1989) 2297.27. D. S. Gill, V. Pathania, A. Kumari, H. Anand, and S. P. Jauhar, Z. Phys. Chem. 218 (2004)

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transport studies of some 1:1 copper(i) perchlorate complexes in acetonitrile-dimethylsulphoxide...

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