Am 1 Semiempirical Mo Calculations of Torsional Barriers and Structural Reorganization in Radical Ions of Pbo and Pbzt Model Structures

Abstract

AM 1 semiempirical calculations on model structures of neutral, anionic and cationic poly(p-phenylenebenzobisthiazole), PBZT, offer an explanation why the PBZT anion has been shown to be an electrical conductor while the PBZT cation is not. To wit, the highest occupied molecular orbital (HOMO) in the PBZT model structure is centered primarily on the sulfur atoms, resulting in concentration of the positive charge on the sulfur atom when the cation is formed. The lowest occupied molecular orbital (LUMO) is far more delocalized and consequently anion formation produces a species which has electronic charge delocalized over the entire model structure. Similar calculations on model structures of neutral, anionic and cationic poly(p-phenyienebenzobisoxazole), PBO, indicate that both frontier orbitals, i. e., the HOMO and the LUMO are delocalized.

Crystal Structure and Packing Disorder of Poly(p-phenylenebenzobisoxazole): Structural Analysis by an Organized Combination of X-ray Imaging Plate System and Computer Simulation Technique

“…Their structural model seems essentially correct, but they gave the predicted diffraction pattern only qualitatively and schematically and they did not calculate the structure factors of the possible reflections so as to compare them with the observed data in a quantitative manner. The structural investigations based on the molecular mechanics calculation or the molecular orbital calculation were also reported by several people − in order to find out the energetically stable molecular conformation of PBO chain, but no trial was made to check the reasonableness of their models through the quantitative evaluation of the X-ray diffraction pattern.…”