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E:\chem-239-d (2)12.pmd

Ultra Chemistry Vol. 8(2), 239-242 (2012).
Influence of ionic strength of medium on the thermodynamic
parameters of substituted heterocyclic drug with
Ce (III), Gd (III) complexes
J.P. NEHETE1, G.P. WAGHULADE3 and A.N. SONAR2 (Acceptance Date 20th July, 2012)
The metal-ligand and proton–ligand stability constant of Ce(III) and Gd(III) with substituted heterocyclic drug (Montelukast) were determined at various ionic strength by pH metric titration. NaClO4 wasused to maintain ionic strength of solution. The results obtained were,extrapolated to the zero ionic strength using an equation with oneindividual parameter. The thermodynamic stability constant of thecomplexes were also calculated.
Key word: Stability constant, ionic strength, substituted Introduction
constant of vanadium with glycene at variousionic strength by potentiometric titration The substituted heterocyclic drug is
technique. Majlesi7 have determined the used for the treatment of asthma. It has seasonal stability constant of Mo (IV) with Iminodiacetic anti- allergies properties.1-2 It forms complex acid at different ionic strength maintain by with Ce(III) and Gd(III). Th. Saroda Devi3
using sodium per chlorate. Sharma8 have have studied the stability constant of Co studied the effect of ionic strength and solvent (III) with 1-Amidino-0-methylurea as primary ligand at different ionic strength. Agrawal4 have also studied the mechanism of protonation have studied the influence of ionic and complex formation of binary complexes strength of medium on complex equilibria.
of La (III), Ce (III), Pr (III) and Nd(III) with Meshram5 have studied the association and dissociation constant of Pr(III) complexes with 3-(2-hydroxy-3-Iodo-5-methyl phenyl)1,5 detail study of complex under identical set of diphenyl pyrazoline at different ionic strength.
experimental condition is still lacking. It was Khorrami6 have studied the stability thought of interest to study the effect of ionic dependence of proton-ligand stability constant complexes of substituted heterocyclic drug and metal-ligand stability constant on ionic with Ce (III) and Gd(III) in 70% ethanol-water strength of medium was examined by taking fix concentration of metal nitrates and ligandsolution during pH metric titration. The system Experimental
has been studied at 0.02, 0.04, 0.06, 0.08, 0.1Mionic strength by varying the concentration of sodium per chlorate. The total ionic strength of medium is calculated by equation.
(accuracy ± 0.01 units) using combine glasselectrode at 208 K. Pure rare earth nitrates µ = ½ C Z 2
(99.9% Pure) were used. All metal nitrates Ci, Zi are the concentration and valency of ith
U.S.A. Metal nitrate was prepared in triplydistill water and concentration was estimated by standard method. The solution of drugs was ligand constant of Ce(III) and Gd(III) complexes prepared in solvent. The pH metric reading in at different ionic strength 0.02,0.04,0.06, 0.08 70% ethanol –water mixture were converted and 0.1M determined. These values determined by using Irving-Rossotties method. From table proposed by Van Uitert Haas. The ethanol was 1, it was seen that the values of proton–ligand purified by the method described by Vogel9.
stability constant (PK) decreases with increasing
The overall ionic strength of solution was ionic strength of medium. The metal-ligand constant maintains by adding NaClO4. All the stability constant (logK) also decrease with
solutions were titrated with standard carbonate increasing ionic strength. For determination of free NaOH (0.2N) solution at different ionic stability constant at zero ionic strength the strength. The titration was carried out at ionic strength by adding NaClO4 (0.02, 0.04, 0.06,0.08, 0.1M).
logK = logK0 + A
pK = pK0 – A
metric titrations of solutions of –1) Free HClO4 (A) Where K0 is the formation constant at zero
ionic strength, pK0 is proton-ligand stability
constant at zero ionic strength, ‘A’ is the Debye- Data obtained from each titration is plotted as 2 is the difference in
pH Vs volume of NaOH added and corresponding square of the changes of product and reactant The pK0 and logK0 values were
Result and Discussion
calculated by plotting the graph of pK, logK , Influence of ionic strength of medium---Ce (III), Gd (III) complexes.
Table 1. Proton–ligand (pK) and metal-ligand stability constant (LogK)
values for Ce (III) and Gd (III) with Montelukast at various ionic strength (µ)  Montelukast Ce(III) 
Montelukast Gd(III) 
Table 2. Thermodynamic stability constant (pK0and Log K0)
values for Ce (III) and Gd (III) with Montelukast.
Montelukast Ce(III) 
 Montelukast Gd(III) 
  pK Vs 
  pK Vs 
pK Vs 
  LogK1 Vs 
  LogK1 Vs 
1 Vs 
  LogK2 Vs 
  LogK2 Vs 
LogK2 Vs 
Table 3. Values of Z2 determined from the plots of PK Vs µ
Z2 Expected
Z2 Observed
HL  H+ + L-
L- + M+3  ML+2
  ML+2 +  L-  ML +1
HL  H+ + L-
L- + M+3  ML+2
  ML+2 +  L-  ML +1
Ultra Chemistry Vol.8(2), (2012).
Dr. R.P. Falak, D.D.N. Bhole College Bhusawal obtained from different plots. The plots pK,
1, logK2 versus
the entire range of ionic strength for both 1. Lipkowitz, Myron A. and Navarra, Tova, systems. It shows that the bronsted relationship The Encyclopedia of Allergies (2nd ed.) is valid for dissociation equilibrium. Fazlur Facts on File, New York, p. 178 (2001).
Rahman10 et. al. have determined similar
results of stability constant of different metal 3. Th. Saroda devi and AK. Manihar Singh, oxime at 0.1,0.05, and 0.01M ionic strength in J. Ind. Coun. Chem, Vol. 24 No. 2, 32-35 4. P.B. Agrawal and M.L. Narwade, Acta The values of Z2 were calculated
Ciencia Indica, XXIXC(2), 141(2003).
from the slope of plots PK Vs
, LogK1 Vs
5. Y.K. Mehram, A.U. Mandakmare and M.L.
Narwade, Orien. J. of Chem., Vol. 16(1), equal to 0.5161.11 The value of Z2 given in
table 3. The observed value of Z2 is different
6. S.A. Khorrami, H. Bayat, S. Sharifi and than the expected value. These values do not give M. Shafai, J. Chem. Eng. data, Vol. 41(6), conclusive evidence regarding the magnitude of the charge of reacting species. This discre- 7. K. Majlesi, F. Gharib and M. Arafati, J. pancy may be due to the limited applicability Inorg. Chem., Vol. 51 No. 2, 1982-1986 of Bronsted equation.Narwade12, Sathe and
meshram4 also recorded same discrepancy.
8. S. Sharma, M. C. Shah, D. Dalwadi, F.
Thakur and J.J. Vora, Research J. of Conclusion
Chem. and Envi., Vol.12(4), 29-34 (2008).
9. G. H. Vogel’s, Jaeffery, S. Bassetl, R. C.
The calculated values of stability constant Denney “Text book of quantetative chemical at various ionic strength are high. From data analysis”. Vth Ed., ELBS Longman, 53
the conclusion is, the complexes of Montelukast with Ce (III) and Gd (III) is quite stable at 10. F. Rahman, S.N. Rastogi and U.K. Jettey, over all range of ionic strength. The values of J. Ind. Chem. Soc., 67, 342 (1990).
11. R.A. Robinson and R.H. Stroke, “Electrolyte from all plots was good agreement of results.
Solutions” IInd Ed. Butterworths, 468(1959).
12. M.L. Narwade, S.W. Sathe, Acta ciencia Indica, VII C (1), 10 (1982).


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