Indian Journal of Chemistry Vol. 38A, September 1999, pp.913-920

Solvation of copper (I) perchlorate in propionitrile-acetonitrile and 3-hydroxypropionitrile-acetonitrile mixtures studied by viscosity, conductance and

63CU NMR measurements

Dip Singh Gill *', Jasbi r Singh', Rohitash Singh', Tal at Zamir" & Terry I. Quickenden"

'Department o f Chemistry, Panj ab Uni versity, Chandigarh 16001 4, India "Department o f Chemi stry, Balochistan Uni versi ty, Quetta, Paki stan

' De partment of Chemistry, University of Western Australia, Nedl ands, Western Australia-6907 , Australia.

Received 3 1 March 1999; revised 23 June 1999

Vi scosi ties and molar conductances o f Bu4NBPh •. Bu. NCIO. and CuCI04 have been measured in the salt concentrati on range (4 -1100) x 10" mol dm') in prop io nitril e (PN ), 3- hydroxy propi o nitril e (3HPN), pro pi onitrile-acetonitrile (PN-AN) and 3-hydroxypropi onitril e-acetonitrile (3 HPN-AN) mixtures at 298. 15 K. h)CU NMR parameters like chemical shift (8), Iinewidth (~) and relati ve intensity (I) of CuCIO. have also been measured in 3HPN -A N mixtures at several compositions and at different concentrations of CuCI0

4 (between 0.034 to 0.468 M) in 3HPN-AN mi xtu re cont aining 43.66 mol % 3HPN. The viscosity data have been analyzed

by the Jones-Dole equation: TJ / 1'10= I +ACI/2+ BC to eva luate A and B coeffi cients of the electrolytes and the ionic vi scosity B and R coeffi cients have been evalu ated using the method reported by Gill and Sharma.The conductance data have been analyzed· by th~ Shedlovsky equation to eva luate A() and KA values o f the electrolytes and the NMR data to obtain qu adrupolar coupling constants (e2Qq/ h) of the so lvated Cu· ion. The viscosi ty results show that Cu· is better so lvated by AN and ClO. ' by PN and 3HPN in PN-AN and 3HPN-AN mi xtures respectively. The (e2Qq/h) result s in 3HPN-AN mi xtures show that 3HPN slowly replaces the AN molecules from the solvation sphere of C u· as the composition of 3HPN increases in the mixture but no change in the solvation sphere of Cu· occurs at constant composition of 3 HPN with change o f CuCIO. concentratio n.

The solvation be haviour of co pper (I ) perchl o ra te (CuCI0

4) is well investigated in acetonitrile (AN) and

its binary mixtures with some organic solvents '-(, . The solubility of copper (I) perchlorate in most of these sol-vent systems, however, is not sufficient to prepare con-centrated copper (I) solutions. There is thus a great need to look for some other solvent systems better than AN in which copper (I) salt solutions of high concentration can be prepared and stabilised .

3-Hydroxypropionitrile (3HPN ) has both - OH and -C = N groups and dissolves copper (I) salts to a much greater extent than AN. Similarly propionitrile (PN) also dissolves copper (I) salts better than AN. Both of these solvents like AN also stabili se copper (I) salts. There are hardly any studies in the literature where PN, 3HPN and their binary mixtures with AN have been used as sol vent systems for the study of solvation behaviour of copper (I) salts. In the present work, therefore, we have undertaken to measure viscosity and molar conductance

oftetrabutylammonium tetraphenylborate (Bu4NBPh

4),

tetrabutylammonium perchlorate (Bu4NCI0

4) and cop-

per (I) perchlorate (CuCl04

) in PN - AN and 3HPN -AN mixtures and IlJCU NMR of CuCI0

4 in 3HPN-AN

mixtures so that the sol vation behaviour of CuClO can 4

be thoroughly investigated .

Materials and Methods Acetonitrile (Merck, 99.5 %) was purified by the

method reported earlier7.x. PN (99 %, Merck) and 3HPN (99 %, Fluka) were stored over well-dried 4 A. molecu-lar sieves for several days. The solvents were filtered under dry conditions. Bu

4NBPh

4. Bu

4NCI0

4 and CuCl0

4.

4CH]CN were prepared by the methods given earlierY' JO • An Ubbelohde s!lspended bulb viscometer with a fl ow time of 280 s for water at 298. 15 K was used fo r all viscosity measurements. The vi scometer was calibrated by the method already gi ven II. The procedure and other experimental details of the viscosity measurements were

914 INDIAN J CHEM, SEC. A, SEPTEMBER 1999

Table I - Density (p), viscosity (1"\ ) and re lative permittivity (E) of PN-AN and 3HPN-AN mixtures at 298.15 K

PN-AN mixture 3HPN-AN mixture

mol % PN plkg m') 1"\ / 1 o-)N sm2 E mol %3HPN p/kg m" 1"\/lo-)Nsm'z E

0.00 776.62 0.343 36.0 0.00 776.62 0.343 36.0

(776.49)' (0.341 )' (35.94)' 2.60 784.32 0.387 32.8

12.98 776.64 0.350 34.2 13.42 83 1.80 0.466 35.5

27.16 776.67 0.360 33.9 27.93 868.79 0.689 53 .6

42 .7 1 776.70 0.374 32.8 43.66 915.20 0.906 69.3

59.86 776.72 0.384 32.1 60.79 958.53 1.358 74.8

78.85 776.76 0.402 31.2 71.80 985.34 1.772 73 .3

100.0 776.79 0.411 28.6 79.49 997.64 2.144 72.5

(776.82);' (0.41 1 )h (26.1)" 91.56 1018.70 2.958 69.5

100.00 1039.97 3.57 1 68.3

'Ref. [12]; href. [24]; ' this value was only approx imately extrapolated in ref.[24] and was not experi mentall y measured .

the same as described previouslyll . The reproducibility of viscosity measurements was ± 0 .1 %. Densities of the pure solvents, binary mixtures and electrolyte solutions were measured using an Anton Paar digital density meter model 60 and calibrated cell type 602 with a reproducibility of ± 0.002 kg m· 3 . Conductances were measured using a digital conductivity meter at a fre-quency of 1000 Hz. The procedure of conductance mea-surement. has been reported earlier? The reproducibi l-ity of conductance measurements was ± 0.2 %. Relative permitti vi ties were measured with an uncertainty of ± 0.5 % by the method described previousll. All NMR measurements were recorded on a Bruker 500 MHz NMR spectrometer us ing a broadband probe head with 10 mm o.d. sample tubes at a frequency of 132.61 35 MHz using the procedures already given4 '. Chemical shift (0), linewidth (Ll ) and relative line intensity (l) of o3CU NMR signal were recorded at 298. 15 ± 0.1 K rela-tive to 0 .064 M CuCI0

4 solution in pure AN for wh ich 0

was selected as 0 ppm, I was se lected as 1000 and Ll was equa l to 480 Hz. Th is reference solu tion was measured from time to time to ensure consistency of all NMR measurements.

Results and Discussion The experimentall y measured den sit ies (p), vi.~cosi

ties (11), and re lative permitivit ies (E) of PN, 3HPN and P -AN and 3HPN-AN mixtures over the entire com-· position ran ge are reported in Table I. Except for some

values in pure AN and PN, no such data are available in the literature with which a comparison can be made. Measured physical constants for pure AN and pure PN are in good agreement with the previous values l2.

Viscosity measurements Viscosities ofBu

4NBPh4,Bu4NClO 4and CuC104 have

been measured in the concentrat ion range ( 16-1 100) x 10.4 mol dnl" in PN, 3HPN and in PN-AN mixtures con-taining 12.98, 27 .16, 42.7 1, 59.86 and 78.85 mol % PN and in 3HPN-AN mixtures contai ning 13.42, 27.93 , 43 .66, 60.79, 79.49, and 8 1.55 mol % 3HPN at 298.15 K. The viscosity data have been analyzed to evaluate A and B coeffici ents of the electro lytes by usi ng the Jones-Dole equat ion U in the form :

T), =1l/ T) .. =I+AC '''+ BC ... ( 1)

where 11 and 11" are the vi scosit ies of the solution and of the pure so lvent or solvent mixture respective ly, Cis molar concentration and A and B are cons tants and are characteristic of the solvent and the salt. The A param-eter is the measure of ion-ion inreract ion and the B pa-rameter is the measu re of ion-solvent interaction. In all the cases, the plots of \jf =( 11-11

0 ) i11oCil2 versus C

I12

were fOllnd to be linear over the whole concentration range :; Indied. The A and B coeffic ients in each case w re calculated from the intercept and slopes of the plots by the least squares treatment. The A and B coeffic ients thus obtained are recorded in Tables 2 and 3 respecti ve ly.

, mol% PN

0.00

13.42

27.93

43.66

60.79

79.49

8 1.55

100.00

GILL el al.: SOLVATION OF COPPER(I) PERCHLORATE

Table 2 - Viscosity A (dm'll mol·1I2) and B (dmJ mol ·l ) coefticients' of the Jones-Dole equation for some electrolytes in PN-AN mixtures at 298.15 K

Bu.NBPh. Bu.NCIO. CuCIO. mol% PN

Ax 102 B AxlOZ B AxlOZ

0.00 1.84 1.29 0.48 0.80 0.65 (2.42) (IJI)h (1.79) (0.81)< (1.75)

(1.35)~

12.98 1.09 1.32 -0.23 0.91 1.05 (2.46) ( 1.82) (1.79)

27.16 0.33 1.37 0.94 0.94 0.40 (2.47) ( 1.82) t 1.79)

42.71 2.09 1.38 0.38 1.01 0.64 (2.49) ( 1.84) (1.81 )

59.86 1.72 1.56 0.49 1.13 0.57 (2.54) ( 1.86) ( 1.83)

78.85 2.63 1.64 -0.44 1.22 1.06 (2.58) ( 1.89) ( 1.84)

100.00 1.52 1.78 -0. 16 1.28 1.29 (2.76) ( 1.99) ( 1.9 1)

'The max imum uncertaint y in the B values is ± 0.02 dmJ mol·l ; hvalues obtained after adding ionic B. and B coeffi cients from ref. [20] ; eref. [1 8]; ~ re f. [2 1 J

B

0.80 (0.77)<

0.87

0.88

0 .94

0.97

0.98

1.00

Table 3 -Viscosity A (dmVl mol·I12) and B (dm] mol-I ) coeflicients' of the Jones-Dole equation fo r some electrolytes in 3HPN-AN mixtures at 298. 15 K

Bu. NBPh4 Bu4NCIO. CuCIO.

AxlOl B Ax102 B Axl02 B

1. 84 1.29 0.48 0.80 0.65 0.80 (2.42) ( 1.78) ( 1.75) 1. 8 1 1.36 1.46 0.90 1.40 0.74 (2.42) ( 1.79) ( I. 72) 1.44 1.44 0.86 1.00 2.25 0.69 (2.00) ( 1.42) ( 1.35) 1. 83 1.45 1.1 6 1.02 0.34 0.7 1 ( 1.83) ( 1.29) ( 1.20) 1.1 5 1.53 0.61 1.06 1.03 0.67 ( 1.77) ( 1.2 1) ( 1.06)

0.S5 1.5S 0.43 1.1 2 1.27 0.66 ( 1.44 ) (1.1 3) ( 1.06) 1.40 1.6 1 ( 1.44 )

( 1.63)1' 1.22 1.14 0.53 0.65 ( 1.24) ( 1. 14)

'The max imum uncertain ty in the B values is ± 0.02 dmJ mol·l ; hBu.NBPh. is not soluble in 100 % 3HPN, thi s vallie is indirectly obtained by ex trapolati on of the values at various compositions

9 15

916 INDIAN J CHEM, SEC. A, SEPTEMBER 1999

Table 4 - 1\, values of some electrolytes' in PN-AN and 3HPN-AN mixtures at 298. 15 K

A,! S cm2 rnol" PN-AN mixture 3HPN-AN mixture

mol % Bu4NBPh

4 Bu

4NCI04 CuQ04 mol % Bu4NBPh. Bu.NCI04 cuelo.

PN 3HPN 0.00 119.8 165.4 168.4 0.00 119.8 165.4 168.4

(119.65)h ( I 65 .06)h (168.4)" 12.98 118.63 163.83 166. 10 13.42 87.53 122.88 126.80

±O.23 ± 0.34 ±O.30 :1:0. 18 ±0.32 ±O.30

27.16 115.57 160.53 162. 12 27.93 59.33 84.13 88.58 ±O.30 ±O.26 ±O.25 ±O. 16 ±O.23 ±O.27

42.71 112.2 1 154.SI 156.3 1 43.66 43 .39 63.19 67. 18 ±O.26 ±O.30 ±O.31 ±O.19 ±O. 17 ±O. 18

59.86 108.13 150.23 155.04 60.79 28.75 43.60 48.46 ±O.21 ±0.35 ±O.27 ±O.12 ±O.09 ±0.09

78.85 103.14 143.8 1 147.14 79.49 22.79 29.34 31.12 ±0.19 ±0.29 ±O.30 ±0.08 ±O.IO ±0.07

100.00 98.60 139.72 144.23 100.00 ( 12.86)J 16.56 17.87 ±O.20 ±0.30 ±O.24 ±0.04 ±0.03

(98.4)' ( 139.4)'

'A ll these electrolytes have no ion-association in PN-AN and 3HPN-AN mixtures, href. [25); ' ref. [26) ; "extrapolated value; ' ref.[24)

The B coefficients of all the three e lectrolytes reported in Tabl es 2 and 3 are posi tive and large . The same

behav iour is observed for many electrolytes in pure 14. 17

and mixed non-aqueous solventsll . I X , l ~ . Except in pure

AN, B values for these salts are not available in litera-

ture to enab le comparison with the present values . The B coefficients in pure AN , however. are in good agree-ment with the previous values ,x.2o,2 1 (recorded in paren-

theses in Table 2) . Also, the B coeffi c ients except for CuCiO in 3HPN-AN mixtures, increase significantly

4

with the inc rease in PN or 3HPN mo l % in the mixture.

The A coefficient s for all e lectro lytes except for Bu NCIO in some PN-AN mixtures are also positive.

4 .)

T hese va lues are small indicat in g that there is no ion-assoc iation in these electrolytes. A compari son of the

experimental A values has been made with the A'l val -ues calculated theore tical ly using the Falken hagen-

Verno n equati on22 .

... (2)

It has been found that the present experimental A values for a ll these salts in a ll ~olvent systems (Tables 2 and

3) are in good agreement with the A~ values calcul ated using Eq. (2) and are g iven in parentheses in Tables 2

and 3 respective ly.

Conductance measurements For the calculation of A values fro m Falkenhagen-

~

Yernon equation, the limitin g equivalent conductance (/\ ) of the elec tro lytes in that particular solvent and the limiting ion conductances (\0, A20) were required. These values have been calculated from conductance measure-ments. Equivalent conductances (/\) of B u4NBPh 4, Bu

4NClO. and CuCl0

4 in these solvent systems were

measured in the concentration range (4- J SO) x 10'.) mol .:1m'" and the 1\0 va lues of the e lectrolytes were cal-culmed using Shed lo vsky's method. T he A/' and A1

0

value s were computed using Bu.)NBPh4 assumption , based on the equations proposed by G ill and Cheema ' .

T he 1\" values ~btai ned f rom conductance measurements are recordeJ in Table 4. T he analysis of the c mductancs

data by the Shed lovsky equ ati on showed that these elec-tro lytes are not assoc iated in PN-AN and 3BPN-AN

mixtures.

,.

GILL et at.: SOLVATION OF COPPER(I) PERCHLORATE 917

Table 5 - Ionic B + and B. coefficients' of some ions in PN-AN and 3HPN-AN mixtures at 298.15 K

B./dm~mol·'

PN-AN mixture

mol% PN Bu~N+ Cu+ Cl04 ' Ph.B '

0.00 0.58 0.58 0.22

12.98 0.59 0.55 0.32

27.16 0.62 0.56 0.32

42.71 0.62 0.55 0.39

59.86 0.70 0.54 0.43

78.85 0.74 0.50 0.48

100.00 0.80 0.52 0.48

'The maximum uncertainty in the B± values is ± 0.02 dm~ mol"

Ionic B + and B coefficients The B coefficients, like I\, values of electrolytes, are

additive and can be split into ionic contributions . There is no direct method to divide B values of e lectrolytes into B + and B. coefficients and that has been done using indirect method purposed by Gill and Sharma tn non-aqueous mixed solvents II (Eqs 3 and 4).

B Su " N '

8 Ph J B ·

and

=(~) ' 5.35

These va lues are recorded in Table 5.

. . . (3)

. . . (4)

A perusal of the data in Table 5 shows that B + and B. va lues for Bu

4N+ and Ph

4B- increase uniformly over the

whole compos ition range with the increase in PN or 3HPN mol % in the mixtures. Similar behaviour for these two ions was observed in AN-DMF' and AN-MeOH' ~ mixtures where such values increased un iformly with increased DMF or methanol mol %. For Cl0

4- , the B

values also increase with the increa 'e in PN or 3HPN mol % bu t the incr ase is very signifIcant as compared to that for Bu N+ and Ph B ions. Lapre B or B values

-1 4 b +

show better solvation: Therefore, CIO~ - ion shows stron-

0.71

0.73

0.75

0.76

0.86

0.90

0.98

3HPN-AN mixture

mol% 3HPN Bu~N+ Cu' CIO; Ph~B '

0.00 0.58 0.58 0.22 0.71

13.42 0.6 1 0.45 0.29 0.75

27.93 0.65 0.34 0.35 0.79

43.44 0.65 0.34 0.37 0.80

60.79 0.69 0.30 0.37 0.84

79.49 0.71 0.25 0.41 0.87

100.00 0.73 0.24 0.41 0.90

ger solvation by PN and 3HPN in the respecti ve mix-tures as compared to that by AN. For Cu+ on the other hand, the B + value decreases significantly with the in-crease in PN or 3HPN mol %. The decrease in the case of 3HPN is much greater than in the case of PN. The

variation of B + coefficients for Cu· with solvent compo-sition shows much better solvation of Cu+ by AN which decreases in the mixtures by the increase in PN or 3HPN

content. CuCIO~ thus shows heteroselective preferential solvation in PN-AN and 3HPN-AN mixtures .

()!eu NMR measurements In order to obtain some add itional information regard-

ing the nature of CuCI04

and the solvation behaviour of Cu+ ion, (" Cu NMR measu rements of CuClO~ have been made in 3HPN-AN mi xtures at different so lvent compos itions as well as at different CuCI0

4 concentra-

ti ons in 3HPN-AN mixture contain ing 43.66 mol % 3HPN. The measured chemical shift (8), linewidth (t.) ;md relati ve in tensity (I) of the n3Cu NMR signal are re-ported in Tables 6 and 7 respec ti vely. The variation of chemical shi ft (8) , linewidth (t.) and relative in tens ity (n of the copper signal as a function of 3HPN composi-tion is shown in Fig.!. Both chemical shift (8) and linewidth (t.) significantly increase bur the relative in-tensi ty (J) dec reases with the increase in 3HPN compo-si tion in the mixture (Fig.l ). The variation of the above sa id NMR pa rameters as a function of CuCIO concen-. 4

918 INDIAN J CHEM, SEC. A, SEPTEMBER 1999

Table 6 - Chemical shift (0), linewitlth (t.) , relative intensity (I), viscosity (TI), reorientational correlation time ('tR

) and quadrupolar coupling constant (e2Qq/h) for 0.064 M CuCIO. solutions in 3HPN-AN mixtures at different compositions at 298 .15 K

mol% 3HPN O/ppm ~Hz TI/I 0·'Nsm·2 't/IO·lls e2Qq/h/MHz

0.00 0 .0 480 1000 0.372 4.45 2.93

2.60 0.9 610 685 0.402 4.81 3. 18

13.42 3.0 960 502 0.482 5.42 3.75

27.93 6.0 1550 291 0.715 8.05 3.91

43.66 9.3 2560 178 0.943 10.61 4.38

60.79 13.5 4175 83 1.403 . 1.82 4.73

71.80 14.9 5760 66 1.878 19.84 4.81

79.49 17.8 6725 54 2.24 1 23.68 4.85

91.56 21.5 8820 30 2.993 29.65 4.87

100.00 23.4 11850 26 3.620 33.57 5.30

Table 7 -Chemical shift (0), linewidth (~), relative intensity (I), viscosity (TI), reorientat ional correlation time ('tR

) and quadrupolar coupling constant (e1Qq/hl for "'Cu NMR signal at different concentrations of CuCIO. in 3HPN-AN mixture containing 43 .66 mol %

CuCIO. OIppm ~Hz

Concentration Imol dm"

0 .034 9.62 2540 88

0.064 9.60 2580 178

0 .1 32 9.53 2657 342

0.209 9 .50 2850 388

0.357 9.48 2960 678

0.468 9.21 3148 808

tration in 43 .66 mol % 3HPN is shown in Fig. 2. The chemical shift (5) for CuCIO. is quite large in 43 .66 mol % 3HPN mixture and decreases from a value of 9.62 ppm to 9.21 ppm with the change in salt concentra-tion from 0 .034 M to 0.468 M (Fig. 2). The linewidth (~) of the copper s ignal in this mixture is also quite large and increases from 2540 Hz to 3148 Hz with the change in salt concentration. The relati ve line intensity (1), how-

3HPN at 298.15 K

TIl I 0·)Nsm·2 't /lO·II S . R e2Qq/h/MH z

0.927 10.43 4.40

0.943 10.61 4.38

0.988 11.12 4.36

1.035 11.65 4.41

1. 109 12.48 4.35

1.228 13.82 4.26

ever, shows an interesting behaviour. The value increases linearly upto about 0. 15 M CuCI0

4 and then the slope

of the line changes (decreases) at higher concentrations. Such behaviour can arise from ion-association of the salt'. CuCI0

4 thus shows ion-association in 3HPN-AN

mixture containing 43.66 mol % 3HPN beyond 0.15 M concentration. Viscosities (11) of all solutions have also been measured and used to calculate the reorientational

GILL e/ al.: SOLVATION OF COPPER(I) PERCHLORATE 919

2!1

20

E 1& a.. a.. 'iO 10

5

0 0 20 40 60 80 100

mol·/.3HPN

16000

12000

N

i!: 8000 ~

4000

0 0 20 40 60 60 100

mol%3HPN

1200

1000

800 ·

• 600 400

200

0 --0 20 40 60 80 100

mol %3HPN

Fig. I - Variat ion of chemical shift (8), linewidth (6) and relative intensi ty (I) of the copper signal as a function or mol % 3HPN in 3HPN-AN mixtures at 298.15 K.

correlation ti mes (" R) and the quadrupo lar cou pli ng con-stant (e2Qq/h ) of the complexes. The 11 '"R and (c2Qq/h) va lues as a funct ion of 3;-/PN composition in 3HPN-AN mixtures are g iven in Table 6 and the 11. 1R :U1d c2Qql h val ues as a function of CuClO 4 concentrJ ti on in 3HP -AN mixture containi ng 43.66 mol % 3HP are recorded in Table 7.

Eq uations (5-7 ) ha ve been llsed [ 0 cJlculate guadrupolar relax a tion rates (I IT

2)o and hen ce

quadrupolar coupling constan t (e2Qq/h) fo r the copp 'r complexes 21 .

9.7

U

s.U !' 9.4 to 9.3

9.2

9.1 0 0.1 0.2 0.3 0.4 0.8

C I (moles dm.a)

3800

3200

N J: 2800

920 INDIAN J CHEM, SEC. A, SEPTEMBER 1999

3HPN. The result shows that 3HPN plays an important role towards solvation of Cu· in 3HPN-AN mixtures. 3HPN slowly replaces the AN molecules from the sol-vation sphere of Cu+ as the composition of 3HPN in-creases in the mixture. The (e2Qq/h) value at all con-centrations of CuCI0

4 in 43.66 mol % 3HPN (Table 7)

is found to be constant and equal to 4.35 ± 0.10 MHz. This shows that the composition of the solvation sphere of Cu· at constant composition of 3HPN does not change with CuCI0

4 concentration.

Acknowledgement ! DSG thanks the Gledden Trust for the Award of a

Gledden Senior Visiting Fellowship for siX' months (from September 1997 to February 1998) and the CSIR, New Delhi for some research grant under the scheme 1(1412)/ 96 EMR-II. TZ thanks Balochistan University, Pakistan for Academic leave for doing research work in Austra-lia.

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