Properties of the low-lying electronic states of phenanthrene: Exact PPP results

We report properties of the exact low-lying states of phenanthrene, its anion and dianion within the Pariser-Parr-Pople (ppp) model. The experimentally known singlet states of the neutral molecule are well reproduced by the model. The intensities for one and two photon absorption to various singlet states are also in good agreement with experiment. From the bond orders of these states, we predict the equilibrium geometries. The relaxation energies of these states, computed from charge-charge correlations and bond orders, are presented. We also present results of ring current calculations in the singlet ground state of phenanthrene. We have also reported energies, spin densities, bond orders, and relaxation energies of several triplet states and compared them with experiments as well as with other calculations, where available. The fine structure constants D and E, computed in the Lowest triplet state, compare well with those obtained from experiments. These properties are also presented for the anions and the dianions. The PPP model in these cases predicts a low-energy (< 1 eV) dipole excitation. (C) 1996 John Wiley & Sons, Inc.