Electronic structure and conformation of aniline and meta-chloroaniline dimers

Poly(aniline) is a subject of considerable scientific and technological int erest. Its homologs such as poly(m-chloroaniline) potentially offer similar physical-chemical properties. In this work we present a comparative theore tical study between aniline and the m-chloroaniline species at several leve ls of theory. To Envisage the possible mechanism of polymerization, we have obtained geometries and electronic structures for the monomers and dimers as well as the corresponding cations and dications. Based on the monomer-op timized geometries, atomic charges, bond orders, and spin densities, a head -to-tail coupling in the electrochemical polymerization is suggested. We ha ve also calculated band gaps and ionization potentials. For the cationic di mers of aniline and m-chloroaniline, the highest occupied molecular orbital -lowest unoccupied molecular orbital (HOMO-LUMO) energy difference has a sm aller value, and oxidation at specific sites may be observed. (C) 2000 John Wiley & Sons, Inc.