Binding of p-aminobenzoate anion to bis(diethylenetriamine)cobalt(III) cation in solution and solid phases: synthesis, characterization, and X-ray structure determination of s-fac-[Co(dien)2]Cl(p-aminobenzoate)2·3H2O

Abstract

The reaction of an isomeric mixture of [Co(dien)2]Cl3 with sodium salt of p-aminobenzoic acid in aqueous medium leads to the formation of dark orange coloured crystals of composition s-fac-[Co(dien)2]Cl(p-aminobenzoate)2·3H2O. The configuration of the cationic isomer was initially determined with the help of spectroscopic data (NMR, UV–Vis, and IR). The binding properties of s-fac-bis(diethylenetriamine)cobalt(III) cation with p-aminobenzoate anion has been determined (in solution phase) with the help of UV–Vis spectroscopic titrations. Single crystal X-ray structure determination of title complex reveals the presence of one cation, three anions (one Cl and two p-aminobenzoates) along with three lattice water molecules. The crystal lattice is stabilized by electrostatic forces of attraction and H-bond interactions (N–H···O, N–H···Cl, O–H···O, and O–H···Cl). The water molecules of crystallization play a major role in stabilizing the complex by forming intermolecular H-bonds with Cl− and O atoms of p-aminobenzoate and water.