Compressibility Behaviour of some Copper (I) Perchlorate Complexes in Binary Mixtures of Acetonitrile with Nitromethane and Dimethylsulfoxide at 298.15 K

Abstract

Abstract Ultrasonic velocity (u) and density (ρ) of the binary mixtures of acetonitrile (AN) with nitromethane (NM) and dimethylsulfoxide (DMSO) as well as of the solutions of Bu4NBPh4, Bu4NClO4, [Cu(CH3CN)4]ClO4, [Cu(Phen)2]ClO4, [Cu(DMPhen)2]ClO4 and [Cu((NH2)2CS)4]ClO4 have been measured over the entire composition range at 298.15 K. Using these data, isentropic compressibilities (K s) and apparent molal isentropic compressibilities (K s, ϕ ) for various salts have been calculated and used for the evaluation of limiting apparent molal isentropic compressibilities (K s, ϕ 0). The K s, ϕ 0 values of various salts have been split into the contribution of individual ions (K s, ϕ 0)±. The (K s, ϕ 0)± values for all copper (I) cations [Cu(CH3CN)4]+, [Cu(Phen)2]+, [Cu(DMPhen)2]+ and [Cu((NH2)2CS)4]+ are negative and large, for Bu4N+ and Ph4B− are positive and large at all compositions in both AN + NM and AN + DMSO mixtures but for ClO4 − are negative in AN + DMSO mixtures and positive in AN + NM mixtures. The variation of (K s, ϕ 0)± values with solvent composition indicates that both DMSO and NM interact with complex copper (I) cations forming complex ions of the type [Cu(CH3CN)4 − x (S) x ]+ (x = 1–4 and S = co-solvent) and [Cu(ligand)2]+(CH3CN) y (S) z in which AN is systematically replaced by the co-solvents. DMSO interacts more strongly with complex copper (I) cations and ClO4 − ion as compared to NM. Bu4N+ and Ph4B− show some special interaction with AN which decreases with the increase of NM or DMSO composition in the mixture.