CASSCF CALCULATIONS FOR NEUTRAL AND ANION-RADICAL STATES OF SEVERAL PI-CONJUGATED BIS-METHYLENE SYSTEMS

The CASSCF calculations were carried out for the neutral and anionic s tates of several model systems including two carbenes linked together through pi-conjugation to investigate variations of the ground spin st ates induced by pi- or sigma-electron doping. The full geometry optimi zations of these anion radical species were performed by the CASSCF en ergy gradient technique. It was found that the optimized geometries fo r the bis-methylene moieties largely depend on the electron configurat ions, particularly the number of sigma-electrons, and the ground spin states for the anion radicals are also sensitive to the symmetry of th e SOMO.