Compressibility behaviour of some copper(I) perchlorate complexes in binary mixtures of acetonitrile with nitromethane and dimethylsulfoxide at 298.15K

Ultrasonic velocity (u) and density (rho) 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)]CIO4, [Cu(Phen)(2)]CIO4, [Cu(DMPhen)(2)]CIO4 and [Cu((NH2)(2)CS)(4)]CIO4 have been measured over the entire composition range at 298.15K. Using these data, isentropic compressibilities (K-s) and apparent molal isentropic compressibilities (K-s,K-phi) for various salts have been calculated and used for the evaluation of limiting apparent molal isentropic compressibilities (K-s,phi(0)). The K-s,phi(0) values S. S 4 of various salts have been split into the contribution of individual ions The (K-s,phi(0)), values for all copper (1) cations [Cu(CH3CN)(4)](+), [Cu(Phen)(2)](+), [Cu(DmPhen)(2)](+) an [Cu((NH2)(2)CS)(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,phi(0)) values with solvent composition indicates that both DMSO and NM interact with complex copper (1) 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 (1) cations and CIO4- 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.