Molecular structure, anharmonic vibrational analysis and electronic spectra of o-, m-, p-iodonitrobenzene using DFT calculations

In the present work, molecular geometry and anharmonic vibrational spectra of o-, m-, p-iodonitrobenzene have been studied. The anharmonic frequencies were calculated using second order perturbative (PT2) approach with basis set 3-21G∗ on iodine and 6-311G(d,p) on other atoms at DFT(B3LYP) level of theory and were compared to experimental values. The assignments of vibrational modes of isomeric iodonitrobenzenes were done by using potential energy distribution (PED) and vibrational assignments of benzene, nitrobenzene and iodobenzene. The combination and overtone bands are also assigned. The electronic spectra were recorded as well as simulated using polarizable continuum model (PCM) at TD-B3LYP/6-311G(d,p)/3-21G∗ level of theory. The vibrational and electronic spectra are interpreted. Moreover, atomic charges, MEP mapping, HOMO–LUMO, NBO analysis and various thermodynamics and molecular properties are reported.