Abstract :
Summary form only given. Unique new ladder polymers, made recently by Scherf and Mullen and consisting of condensed succession of six and five membered conjugated carbon rings, open up the opportunity to synthesize polymeric materials with surprising properties. The electronic structures of several isomers have been studied, using geometry optimization, self-consistent field calculations and spin-unrestricted Hartree-Fock calculations. The fundamental parameters of the electronic structure of these non-Kekule polymers is very sensitive to the topology of the isomers. Some are intrinsically small band gap polymers, others have intermediate bandgaps. In some instances the high spin ground state is favored over a Peierls-distorted small bandgap state, or an antiferromagnetically coupled state. Calculated data are compared with experiment, where data are available. These comparisons include planarized poly-phenylenes.
