Infrared and ab initio studies of conducting molecules: 2,5-Diamino-3,6-dichloro-1,4-benzoquinone

Abstract

2,5-Diamino-3,6-dichloro-1,4-benzoquinone has been synthesized by modifying the procedure reported in literature. Its IR spectrum has been recorded in the solid phase in the range 4000–400 cm −1. Ab initio calculations have been performed using Gaussian ’03 program to compute optimized geometry, harmonic vibrational frequencies along with intensities in IR and Raman spectra and atomic charges at RHF/6-31+G*, B3LYP/6-31+G* and B3LYP/6-311++G** levels. To make vibrational analysis Gaussian View software was used. The optimized molecular structure is found to possess C 2h point group symmetry. The observed IR frequencies have been assigned to different modes taking C 2h molecular symmetry with the help of pictorial view of normal modes. From the magnitude of the observed frequencies corresponding to the NH 2 stretching motions an indication of H-bonding is noticed. From geometrical parameters of the molecule it appears that two parallel sets of conjugated strands are formed in this molecule providing a route to conduct charges. The N–H bonds facing towards chlorine atoms are found to be shorter than those facing towards oxygen atoms indicating the presence of H-bonding between hydrogen atom of an NH 2 group and carbonyl (quinoid) oxygen atom.