Termodynamics of Ag+ Cation complexation With N,N′-bis (salicylidene)-1,3-propane diamine in Some Binary Mixed Non-aqueous Solvents

The complexation reaction between Ag+ cation and the N,N′-bis (salicylidene)-1,3-propane diamine (SB- SalPr) ligand (Fig. 1) in the binary mixtures: acetonitrile-methanol (AN-MeOH), acetonitrile-ethanol (AN-EtOH), acetonitrile-dimethylsulfoxide (AN-DMSO) and acetonitrile-dimethylformamide (AN-DMF), was investigated using a conductometric method at different temperatures of (288.15, 298.15, 308.15 and 318.15) K. In most of the studied solvent systems, SB- SalPr forms a 1:1 [M: L] complex with the Ag+ cation. But in some cases, 1:2 [M: L2] complexes are formed in solutions. The best estimate of stability constant (log kf=3.74) for the [SB-SalPr. Ag]+ complex, was observed for the AN-MeOH (25:75 mol %) binary mixture at 308.15 K using GENPLOT computer program. The values of the standard thermodynamic parameters (i.e., ΔGc˚, ΔHc˚ and ΔSc˚) for formation of the 1:1 complexes of [SB-SalPr. Ag]+ were obtained from temperature dependence of the stability constants of the complexes using the van, t Hoff plots. The results show that, in most cases, the [SB-SalPr. Ag]+ complexes are enthalpy destabilized but entropy stabilized. The values and signs of the thermodynamic parameters are affected by the nature and composition of the mixed solvents [1, 2].