Theoretical investigation of the effects of solvents and para-substituents

The effects of halogens (F, Br, and Cl) and solvent media (acetone, ethanol, and toluene) on the structural and electronic properties of nitrobenzene compounds were investigated by combination the DFT/B3LYP and MP2 methods with 6-31 + G (d,p) basis set. The results indicate that the bond lengths between carbon-halogen atoms are increased with increased atomic size and decreased electronegativity, whereas some bond angle magnitudes are reduced than those with substitution halogens. Also, various solvent effects of studied compounds were performed with the conductor-like polarizable continuum model (CPCM) method, showing a reduction of the dipole moment by the substitution of a hydrogen atom for a ring with halogen atoms in para-position over the ring. In addition, natural bond orbitals (NBA), chemical reactivity descriptors, and the frontier molecular orbitals (FMOs) of substituted nitrobenzene were calculated. NBO analysis showed the strong interactions within a cyclic system and the fluorine atom in P-FNB is considered the best donor. Moreover, FMO analysis showed that energy band gap is related to the nature of the substituents (halogen atoms) in the para-position of the nitrobenzene compound.