The bis(3-amino-1-phenyl-2-buten-1-onato)copper(II) complex, Cu(APBO)2, has been characterized by ab initio calculations and vibrational spectroscopic techniques. The geometry optimization are performed at the UB3LYP level using 6-311G(d) and 6-311þG(d,p) basis sets. The vibrational frequencies were calculated at the UB3LYP/6-311þG(d,p) level. Furthermore, to include the relativistic effects on the core electrons of Cu atom, the optimization and vibrational frequencies were recalculated at the UB3LYP level with 6-311G(d,p) basis set for all atoms but the Cu atom, whose basis set was LanL2DZ and CEP-31G, with their corresponding pseudopotential. The scaled theoretical frequencies and the structural parameters are in excellent agreement with the experimental data. HOMOeLUMO energies and natural charges over chelated ring atoms of Cu(APBO)2 and Cu(APO)2 are also compared.

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