Study of Kinetics and Mechanism of Ligand Substitution Reaction of Tetraaza Macrocyclic Ligand with Tridentate Schiff Base Dianionic Ligand in Copper(II) Complexes

AbstractThe kinetics of the ligand exchange reaction between the tetraaza macrocycle, N۴۲HClO۴ (where N۴۲HClO۴ is ۵,۷,۷,۱۲,۱۴,۱۴-Hexaniethyl-۱,۴,۸,۱۱-tetraazacyclo tetradeca-۴,۱۱-diene dihydrogen perchlorate) and CuLX complexes, where L is N-(۲-carboxy phenyl)salicyliden imine a tridentate Schiff base dianionic ligand and X is a neutral monodentate ligand have been studied by visible spectrophotometry in dimethylformamide, DMF, solvent at ۲۵ ± ۰.۲°C and an ionic strength of ۰.۱ M NaClO۴. The kinetics of the ligand exchange reaction were studied under pseudo-first-order with [N۴۲HClO۴] >> [CuLX] by measuring the absorbance changes at ۷۰۰ nm, corresponding to the maximum difference in molar absorptivity between reactants and products. Under these conditions, the reaction was found to proceed via a two-step process (biphasic reaction). Therefore, two rate constants kobs(۱) and kobs(۲), were obtained. The first step was rapid and dependent on the macrocycle concentration, [N۴۲HClO۴], whereas the second step was not significantly affected by [N۴۲HClO۴] and is the determining step. A mechanism consistent with these results is proposed.

کلیدواژه ها:

Kinetic ، Macrocyclic ligand ، Cu(II) complexes ، Ligand Substitution ، Schiff base