Crystal Structure, Infrared Spectra and Density Functional Theory Study on 2,3-Diketo-benzopiperazine Dimer

2,3-Diketo-benzopiperazine, which exists as dimeric form in its crystal structure has been synthesized. The calculated results on the dimer at B3LYP/6-31G* level show that the average strength of the double hydrogen bonds is of medium-grade. Natural bond orbital analyses have been performed. The predicted harmonic vibration frequencies support the experimental values. The thermodynamic properties of the dimer at different temperatures have been calculated and the change of Gibbs free energy for the aggregation from the monomer to the dimerDelta GT = -30.86 kJ/mol at 298.15 K, which implies the spontaneous process of the dimer formation.