Experimental and ab initio calculational studies on 2,3-diketo-benzopiperazine

The title compound, 2,3-diketo-benzopiperazine, has been synthesized and characterized by elemental analysis, IR, electronic spectroscopy and single crystal X-ray diffraction. Ab initio calculations of the structure, natural bond orbital, topological analysis and thermodynamic functions of the title compound were performed at HF/6-311G** and B3LYP/6-311G** levels of theory. Vibrational frequencies were also predicted, assigned, compared with the experimental values, and they supported each other. Electronic absorption spectra were calculated by the time-dependent density functional theory, which indicates that the two absorption bands are mainly derived from the contribution of bands p/p*. The calculation of the second order optical non-linearity was carried out, and the molecular hyperpolarisability was 3.282!10K30 esu. q 2004 Elsevier B.V. All rights reserved