Electrochemical behaviour of In(III) with Isoleucine in aqueous and non-aqueous media at Dropping Mercury Electrode

 

Jyoti Singh¹, Sushil Kumar Sharma²

¹Assistant Professor, Department of Chemistry, Uka Tarsadia University, Bardoli, Gujarat, INDIA.

²Assistant Professor, Department of Pure & Applied Chemistry, University of Kota, Kota, Rajasthan, INDIA

*Corresponding Author E-mail: sksharmauok@gmail.com

Studies of In(III) metal with Isoleucine have been carried out by Polarographic method in non-aqueous (20%, 40%, DMSO) medium under varying temperatures at 308K and 318K. Potassium Nitrate was used as a supporting electrolyte. The reduction of In(III) was found to be quasi-reversible in non-aqueous medium. Isoleucine ligand has shown the formation of 1:1, 1:2 and 1:3 complexes. DeFord and Hume method has been applied for the determination of composition and stability constants of the complex species. The changes in thermodynamic parameters ΔH°, ΔG°, ΔS°, accompanying complexation have been evaluated. The mathematical Mihailov's method has also been applied for the comparison of stability constants values.

 

 

 

INTRODUCTION:

Amino acids are the chemical units or "Building Block" of the body that make up proteins, which improve the growth and maintenance of all cells are dependent upon them. Isoleucine stimulates the brain in order to produce mental alertness. Amino acids have wide variety of applications varying from biological, pharmaceutical and other chemical uses and have  been  reported to form complexes with some metals and hence the importance of this class of compounds have been growth number of electrochemical studies on the behaviour of amino acids and their complexes. The coordinated system Cu(II)-neutral L-isoleucine and Cu(II)-L-isoleucinate ion were studied polarographically. in aq. medium m = 1.0M (NaClO₄) and 25 ± 0.1°C and the stability constants of the complexes were determined.¹

 

Interaction between Cd(II) with some L-amino acids such as L-lysine, L-serine and other L-amino acids as a primary ligands and vitamin - PP as a secondary ligand has been studied by DC polarography at pH = 7.3 ± 0.01 in 1.0 M KNO₃ as a supporting electrolyte at 298K. Schaap and and McMaster's method confirmed the formation of 1:1:1, 1:1:2, 1:2:1 complexes with stability constant.²

 

Reduction of Tl(I) L-Threonine complexes in aqueous non-aqueous  media at d.m.e.³    Studies have been done on mixed-ligand complexes of Pb(II) with some amino acids (Isoleucine, valine and other amino acids) at DME by polarography. The stability constants were determined by the method of DeFord and Hume.⁴ and the stability constants of mixed-ligand complexes have been evaluated by the method of Schaap and McMasters.

 

Electrochemical study of complexes Cd(II) with antibiotic drug has been carried out at DME in non-aqueous media⁵. ^. Polarograpic studies of histidine with p-block elements like Ga(III), In(III), Tl(I) have been carried out at constant ionic strength (m=1) by using KCl at 298K and 308k temperatures.^6-9 Polarographic determination of Tl(I) complexes with L-threonine in aqueous and non aqueous media¹⁰was also studies. Electrochemical studies have been carried out of Penicilin Benzyl salt with Pb(II) in nonaqueous media.¹¹ Polarographic study carried out on In(III) complex with 2,2´-oxydiacetic acid in aqueous and aqueous-non aqueous media (methanol, ethanol).^12-18  Comparative polarographic studies of Cu(II) complex of glycine have been carried out in aqueous and aqueous nonaqueous media. Present paper deals with the study of In(III) with isoleucine in non-aqueous media (20% DMSO and 40% DMSO).

 

MATERIAL AND METHODS:

A CL-362 polarographic analyser was used to record polarograms using saturated calomel electrode as the reference electrode and DME as microelectrode. Reagent grade chemicals were used and isoleucine was used as complexing agent. All solutions were prepared in double distilled water. Potassium nitrate was used as a supporting electrolyte to maintain constant ionic strength.

 

Triton X-100 was used to suppress the observed maxima. The DME had the following characteristics, m = 4.62, mg/s, t = 2 sec and height of the mercury column h_eff = 43 cm and purified N₂ was used for deaeration.

 

RESULTS AND DISCUSSION:

The reduction of In(III) in presence of Isoleucine was found quasi-qreversible in non-aqueous (20%, 40%, DMSO) medium, under varying temperatures at 308K and 318K. Direct proportionality of diffusion current to the square root of effective height of mercury column indicates the reduction to be diffusion controlled. The values of half-wave potentials for metal ion and their complexes shifted to more negative values on increasing concentration of ligand. This system has been treated with Gelling's method and E^r_1/2 values were obtained.

 

The complex ion formed is of much larger size as compared to aqua metal ion. Hence the low values of diffusion currents have been found with the increase of ligand concentration.

 

The values of overall formation constants log b_j were calculated by the graphical extrapolation method. The experimentally determined values calculated for In(III)-Isoleucine system in 20% DMSO at 308K and 318K are recorded in Tables 1 and 2, respectively and the overall formation constant were obtained by extrapolation of F_j[(X)] function to the zero concentration. The formation constants of the three complexes are log b₁ = 3.9474, log b₂ = 4.7401, and log b₃ = 7.8560, at 308K and the formation constant values at 318K are log b₁ = 3.079, log b₂ =4.653,and log b₃ = 7.1760.

 

In 40% DMSO Solvent, the overall formation constants for In(III)-Isoleucine system were also calculated and the polarographic parameters are recorded at 308K and 318K in Tables 3 and 4 respectively. The formation constants of three complex species formed are logb₁ = 3.9560, logb₂=4.7633, and logb₃=7.8670. The values of formation constants at 318K are 3.130 ,4.698, and 7.220.

 

 

TABLE-2: Polarographic measurements and F_j[(X)] function values for In(III)-Isoleucine system in 20% DMSO at 308K

[In(III)] = 0.1 mM, Ionic strength (m) = 1.0 (KNO₃) ]

CX (Mole/Litre) Concentration of Isoleucine	id (mA)	Er1/2  (-V vs S.C.E)	F0[(X)]	F1[(X)] x 103	F2[(X)] ×104	F3[(X)] × 107
0.000	6.4	0.55443	-	-	-	-
0.001	6.32	0.5631	2.4763	14.7630	76.3000	-
0.002	6.30	0.5875	4.1613	15.8060	90.3250	17.660
0.003	6.25	0.5895	6.1618	17.2060	106.8660	17.2800
0.004	6.20	0.5968	8.5810	18.9520	123.8120	17.2000
0.005	6.15	0.6047	11.5292	21.0580	141.1680	17.2800
0.006	6.10	0.6111	15.1051	23.5080	158.4750	17.2800
0.007	6.05	0.6166	19.3595	26.2270	174.6830	17.2800

 

TABLE-2: Polarographic measurements and F_j[(X)] function values for In(III)-Isoleucine system in 20% DMSO at 318K  

[In(III)] = 0.1 mM, Ionic strength (m) = 1.0 (KNO₃) ]

CX (Mole/Litre) Concentration of Isoleucine	id (mA)	Er1/2                       (-V vs S.C.E)	F0[(X)]	F1[(X)] x 103	F2[(X)] ×104	F3[(X)] × 107
0.000	6.4	0.5770	-	-	-	-
0.001	6.32	0.5772	2.252	12.2529	52.9000	-
0.002	6.30	0.5773	3.6897	13.448	72.42250	1.3710
0.003	6.25	0.5778	5.3923	14.6418	88.0330	1.4340
0.004	6.20	0.5778	7.4189	16.047	101.1750	1.4300
0.005	6.15	0.5782	9.9880	17.976	119.5200	1.4390
0.006	6.10	0.5785	13.0894	20.179	135.8160	1.5130
0.007	6.05	0.5790	16.8766	22.679	152.5570	1.5300

TABLE-3: Polarographic measurements and F_j[(X)] function values for In(III)-Isoleucine system in40% DMSO at 308K

[In(III)] = 0.1 mM, Ionic strength (m) = 1.0 (KNO₃)]

CX (Mole/Litre) Concentration of Isoleucine	id (mA)	Er1/2                         (-V vs S.C.E)	F0[(X)]	F1[(X)] x 102	F2[(X)] ×103	F3[(X)] × 104
0.000	6.	0.5760	-	-	-	-
0.001	6.5	0.5773	3.58039	15.552	8.6640	6.1361
0.002	6.4	0.5780	6.4054	16.1106	11.8640	6.1631
0.003	6.3	0.5786	9.5662	16.9156	15.0690	6.1740
0.004	6.26	0.5800	13.2247	17.6544	18.2629	6.1755
0.005	6.20	0.5820	17.3836	18.4042	21.4648	6.1784
0.006	6.1	0.5831	22.2853	19.2033	24.6635	6.1793
0.007	6.0	0.5877	28.009	20.007	27.8665	6.1842

 

 

 

 

TABLE-4: Polarographic measurements and F_j[(X)] function values for In(III)-Isoleucine system in40% DMSO at 318K

[In(III)] = 0.1 mM, Ionic strength (m) = 1.0 (KNO₃)]

CX (Mole/Litre) Concentration of Isoleucine	id (mA)	Er1/2  (-V vs S.C.E)	F0[(X)]	F1[(X)] x 103	F2[(X)] ×104	F3[(X)] × 107
0.000	6.53	0.5660	-	-	-	-
0.001	6.46	0.5663	2.4060	14.061	5.9740	5.8841
0.002	6.29	0.5669	4.0584	15.161	8.520	5.8842
0.003	6.28	0.5672	5.9907	16.443	11.8062	5.9034
0.004	6.25	0.5671	8.2818	18.174	14.7406	5.9106
0.005	6.25	0.5797	10.9538	19.907	17.5082	5.9920
0.006	6.24	0.5835	14.5032	22.505	20.489	5.9099
0.007	6.20	0.5856	18.6248	25.178	23.408	5.8890

 

 

 

It is concluded from the above results that for the definite composition of the non-aqueous mixture that as the concentration of solvent increases, stability of complexes increases because complexation increases with increased availability of ligand molecules.

 

The overall change in thermodynamic parameters DH°, DG° and DS° on complex formation of In(III)-isoleucine system in 20% and 40% DMSO solvent mixtures at 308K and 318K are recorded in Tables 5,6.

 

 

Table-5: Stability constants and thermodynamic parameters of In(III)-isoleucine system in aqueous-DMSO (20%) solvent mixtures.

Metal complex species	log bj		DG° (–) (K.cal./mole)	DH° (–) (K.cal./mole)	DS° (–) (K.cal.deg/mol)
	308K	318K
MX1	3.9474	3.079	4.3680	38.793	0.108
MX2	4.7401	4.652	6.5995	37.086	0.0958
MX3	7.8560	7.7760	11.0087	30.785	0.05999

M = In(III), X = Isoleucine

 

 

 

 

Table-6: Stability constants and thermodynamic parameters of In(III)-isoleucine system in aqueous-DMSO (40%) solvent mixtures.

Metal complex species	log bj		DG° (–) (K.cal./mole)	DH° (–) (K.cal./mole)	DS° (–) (K.cal.deg/mol)
	308K	318K
MX1	3.9560	3.130	4.328	42.066	0.126
MX2	4.7633	4.698	6.490	41.823	0.118
MX3	7.8670	7.220	9.950	35.248	0.089

M = In(III), X = Isoleucine

 

The more negative values of DG° for 1:3 complexes show that the driving tendency of the complexation reaction is from left to right and the reaction tends to proceed spontaneously. The negative values of DH° suggest that the formation of these complexes is an exothermic process.

The value of stability constants for In(III)-isoleucine system in 20% DMSO and 40% DMSO solvent mixtures have also been further verified by mathematical method given by Mihailov and data are recorded in Table-7.

 

 

TABLE-7: The value of stability constants for In(III)-isoleucine system in 20% DMSO and 40% DMSO solvent mixtures

Solvent	Temp.	log bj	DeFord and Hume	Mihailov
20% DMSO	308K	log b1	3.9474	3.5498
		log b2	4.740	3.8010
		log b3	7.8560	6.4996
	318K	log b1	3.079	3.679
		log b2	4.653	3.8652
		log b3	7.1760	6.6021
40% DMSO	308K	log b1	3.9560	3.6874
		log b2	4.7633	4.9904
		log b3	7.8670	6.116
	318K	log b1	3.130	3.034
		log b2	4.698	4.662
		log b3	7.220	7.553

 

 

CONCLUSION:

(i) In definite composition of the non-aqueous mixture, the concentration of solvent increases, stability of complexes increases because complexation increases with increased availability of ligand molecules.

(ii)The overall change in thermodynamic parameters DH°, DG° and DS° on complex formation of In(III)-isoleucine system in 20% and 40% DMSO solvent mixtures at 308K and 318K are recorded.

(iii) The negative values of DH° suggest that the formation of these complexes is an exothermic process.

(iv) The negative values of DG° suggest that the formation of these complexes is an spontaneous process.

 

REFERENCES:

1.          Castro-Aleman v.v., Sanz-Alaezos M.T., Rodriguez Placeres J.C., Garcia-Montelongo F. J.Electrochimica.Acta.1990; 35(6): 999-1001.

2.          Khanam A., Khan F., J.Ind.Chem.Soc. 2008;85(1):89-91.

3.          Agrawal S. and Gupta O.D., I.J.C.S, 2012; 10(3):1205-1212.

4.          Mihailov M.H., J.Inorg.Nucl.Chem,1974;73:5321.

5.          Karadia C.  and Gupta O.D., Int.J.Chem.Sci, 2009;7(3):1531-1536.

6.          Fernanedes P.S., J. of. Chem and Environment,2001; 59-64.

7.          Gupta, Saini, Kalawati, Panday R.S., J.Chem.Soc, 2006;83: 495.

8.          Zuman P.  , Elect.An, 2000; 912: 1187-1194.

9.          Karadia C.  and Gupta O.D., Rasayan J. Chem, 2009; 2(1): 18-22.

10.       Agrawal S. and Gupta O.D., Int. J. Chem. Sci, 2014; 209-216.

11.       Meena, Sharma S., and Gupta O.D., Asian .J. of. Chem, 2009; 21: 4346-49

12.       Sharma S., Sharma A., Meena, Ultra.Chem,2008; 4(2):165- 170.

13.       Sharma SK, Chhimpa D, Sharma IK and Verma PS. Electrochemical Reduction of p-Nitro benzoic acid at Glassy Carbon and Stainless Steel (SS-316) Electrode at Different pH.Asian Journal of chemistry.2009;21(5): 3976-3980.

14.       Sharma SK, Jain N, Agarwal H, Sharma IK and Verma PS. Voltammetric behaviour of o-nitro benzoic acid in aqueous-methanol medium.International Journal of  Chemical  Sciences 2009;7(2): 1353-1360.

15.       Sharma SK, Sharma IK and Verma PS. Electrochemical reduction of m-Nitro benzoic acid at various electrode and pH.Research Journal of Pharmaceutical, Biological and Chemical Sciences.2013;4(1): 635-641.

16.       Sharma SK, Sharma IK and Verma PS. Electrochemical Reduction of p-Nitrobenzamide at Stainless (SS-316) Electrode in Basic Media. Research Journal of Chemical Sciences, 2013;3(3): 1-4.

17.       Sharma SK, Wadhvani G, Sharma IK and Verma PS. Synthesis of 3-Hydroxy cyclohexanone by Electrochemical and Microbial techniques. International Journal of Chem Tech Research, 2014; 6(2): 1462-1469.

18.       Sharma SK, Wadhvani G, Sharma IK and Verma PS. Electrochemical Reduction of 2-Methylcyclohexane-1, 3-Dione at Stainless Steel (SS-316) Electrode in Basic Media. Int .J. of Innovative Research in Science, Engg. & Tech.2014; 3(12): 17837-17840.

 

 

 

 

 

 

 

Received on 04.11.2017         Modified on 13.12.2017

Accepted on 06.01.2018         © AJRC All right reserved