Push-pull porphyrins as non-linear optical materials: ab initio quantum chemical calculations

We report accurate ab initio quantum chemical calculations of the first static hyperpolarizability (beta) of porphyrin systems containing porphyrin moiety as the electron donor and quinone and pyromellitimide as the electron acceptors separated by a spacer which influence the electronic communication between donor and acceptor. Geometries of all porphyrin molecules were optimised at the Hartree-Fock level with STO-3G minimal basis set and with the 3-21G split valence basis set using GAUSSIAN98W. In addition to non-linear properties, polarizabilities (alpha) of these molecules are also reported. The calculated values of beta were compared with beta of tertraphenyl porphyrin derivatives reported in the literature. We examine the HOMO and LUMO generated via GAUSSIAN98W in order to explain the variation of beta in these highly conjugated molecular systems. The study suggested that these porphyrin molecules in general may have potential applications in the development of non-linear optical materials. (C) 2003 Elsevier B.V. All rights reserved.