Molecular structure, vibrational spectra, HOMO, LUMO and NMR studies of 1,2-dichloro-4-nitrobenzene and 2,3,5,6-tetrachloro-1-nitrobenzene based on density functional calculations

The vibrational spectra of 1,2-dichloro-4-nitrobenzene (DCNB) and 2,3,5,6-tetrachloro-1-nitrobenzene (TCNB) were computed using B3LYP methodology with 6-31G* basis set. The solid phase FTIR and FT-Raman spectra were recorded in the region 4000–400 cm−1 and 4000–50 cm−1, respectively. A similarity was achieved between the observed and calculated frequencies by refinement of the scale factors. The HOMO and LUMO energies were calculated. 13C and 1H NMR chemical shifts results were also compared with the experimental values.