Theoretical characterization of phenylene-based oligomers, polymers, and dendrimers

Phenylene-based pi-conjugated materials are of current interest due to their wide range of possible applications, especially in light-emitting diodes, displays, and lasers. In this contribution, we first review the results of recent theoretical calculations on the geometric and electronic properties of phenylene-based chains, paying special attention to the influence of chemical doping on the geometry and optical absorption spectra. We then discuss an approach that allows us to characterize the electronic levels of finite size molecules in momentum space and to describe the chain-size evolution from molecular levels to band states in quasi-infinite one-dimensional chains. Finally, we characterize, at the molecular mechanics and molecular dynamics level, the structural properties of dendrimers synthesized with benzene rings as molecular building blocks; we analyze the shape persistence of dendrimers built on different cores by investigating the time evolution of the structures of their first and second generations. (C) 1999 Elsevier Science S.A. All rights reserved.