This article presents a combined experimental and computational investigation of 3-amino-1-phenyl-2-buten-1-onato, APBO ligand and its copper(II) and nickel(II) complexes. APBO is an unsymmetrical, bidentate and monoanionic ligand with different coordinating atoms (N,O). A comparison among different possible conformers of the ligand has been carried out using density functional theory (DFT) method at the B3LYP/6-31?G(d,p) level. It was demonstrated that two factors control stability of the compounds as hydrogen bonding (conventional and nonconventional) and resonance effect. The effectiveness of each of these parameters on the stability of ligands is discussed. The prepared homoleptic complexes of [Ni(APBO)2] and [Cu(APBO)2] were characterized with IR, NMR, UV–Vis spectroscopic techniques. The X-ray crystallography of [Ni(APBO)2] demonstrated that the bidentate APBO binds to the metal center in trans fashion and the geometry around the nickel atom is square planar. The experimental studies on the complexes were accompanied computationally by the DFT and time-dependent DFT calculations.
