Density functional theory study of the free and cobalt-coordinated allopurinol ligand

Abstract

Chemical and physicochemical properties of the purinic structural isomer, allopurinol have been the subject of study from experimental and theoretical points of view. To gain insight in to the understanding of these properties, a density functional theory study of neutral allopurinol in its ketonic N(1)–H/N(5)–H tautomeric form, in free form (in both (a) solid state and (b) gas phase), and (c) as a ligand in a metallic compound in solid state, was carried out. Several electronic properties like Mayer indices, atomic charges, electric dipole moment, total electronic charge density, molecular electrostatic potential, MOs-wave function and IR vibrational modes, have been obtained for the three systems. The study shows that some electronic properties are sensitive to the heterocyclic molecular structural changes, and also to either free or coordinated state. The corresponding properties for the Co compound allow us to explore some aspects of the metal–ligand interactions. A preliminary theoretical assignment of the experimental IR spectra of both free allopurinol and the Co compound in solid phase has also been performed.