Ab Initio Studies of the Dipole Moments and Polarizabilities of p-nitroaniline and Related Molecules in their Ground and Excited States.

We report Ab Initio energies, dipole moments and mean dipole polarizabilities for the ground and five lowest electronic excited singlet states of nitromethane, methylamine, nitromethylamine, nitrobenzene, aniline and p-nitroaniline, together with ground state data for methane and benzene. Ground state properties were calculated using the HF/6-311++G(2d,1p) model whilst excited states were modelled using CIS and CIS(D). Our ground state results are consistent with available experimental data and other advanced literature calculations. The XCH2Y calculations give group contributions of 13.6 atomic units (au) for NO2 and 7.7 au for NH2. The XC6H4Y 's suggest 14.4 and 10.8 au, but there is no evidence of a contribution from the push-pull mechanism. The excited state dipole moments and 's are consistent with the sparse experimental data, and we predict immensely enhanced values for these properties in many of the excited states.