Density Functional Calculations on a Double Hydrogen Bonded Dimer of (p-Methoxyphenyl)thiosemicarbazide

摘要

Density functional theory (DFT) calculations on a double hydrogen-bonded dimer of (p-methoxyphenyl)thiosemicarbazide were carried out at B3LYP/6-31G* level.The optimized geometry of the dimer closely resembles that in the crystal.The calculated results show that the total energy of the dimer is much lower than the sum of energies of the two monomers,and the average strength of the double hydrogen bond is about 21.92 kJ/mol.In order to probe the origin of the interactions in the dimer,natural bond orbital analyses have been performed.The thermodynamic properties of the title compound at different temperatures have also been calculated on the basis of vibrational analyses and the change of Gibbs free energy for dimerization of the two monomers.DELTA G_T = -18.40 kJ/mol at 298.15 K and 0.1 MPa,which implies the spontaneous process of the dimer formation.The correlation graphs of S_m~0,H_m~0 and temperatures for the dimer are depicted.