Synthesis of a new naphthol-derivative salen and spectrophotometric study of the thermodynamics and kinetics of its complexation with copper(II) ion in binary dimethylsulfoxide-acetonitrile mixtures

A synthetic procedure has been developed for the preparation of new salen ( 2,2'-[1,2-ethanediyl bis (nitriloethylidyne)] bis (1-naphthalenol)). The th ermodynamics and kinetics of complexation reaction between the new salen an d Cu2+ ion were investigated spectrophotometrically in different dimethyl s ulfoxide-acetonitrile mixtures. Formation constant of the resulting 1:1 com plex was determined from the absorbance-mole ratio data and found to increa se with increasing acetonitrile content of the solvent mixtures. Enthalpy a nd entropy data for complexation were determined from the temperature depen dence of the formation constant. In all solvent mixtures, the sale n-copper complex is entropy stabilized but enthalpy destabilized. Order of reaction , rate constants and activation parameters for the complexation reaction in different solvent mixtures were also investigated. The Arrhenius plots sho wed a distinct isokinetic temperature at about 88 degrees C, at which the r eaction rate is approximately independent of the solvent composition. Activ ation parameters are strongly solvent dependent.