Conducting Polymers and Electroactive Materials
This program targets new electronic materials, and supramolecular structures constructed from labile C-C bonds. Polymer syntheses involve metal-mediated polymerizations of alkene, alkyne, silane, and/or stannane monomers. An emphasis is placed on development of electron-delocalized polymers, which show promise as advanced materials that function as conductors, semiconductors, photoconductors and light-emitting materials. Metal-catalyzed dehydropolymerizations have been used to obtain the first high molecular weight polystannanes. These low band-gap polymers are semiconducting when doped, and display interesting temperature-dependent optical properties. An approach to new pi-conjugated structures is based on the zirconocene-coupling of diynes to polymers with zirconacyclopentadiene units in the main chain. The metallacyclic monomer units provide versatile chemical pathways for placement of various conjugated groups (dienes, aromatic heterocycles) into a delocalized chain. Related methods are being used to obtain oligomeric and small-molecule organic materials that possess high electron affinities, n-type semiconducting properties, and high electron mobilities. These molecules are being constructed by zirconocene-coupling methods, and by nucleophilic aromatic substitution reactions of fluorinated aromatic systems. A related topic is based on the discovery that zirconocene-coupling methods are useful in high-yield syntheses of macrocycles and cages, from readily available diynes. This method, which relies on the reversibility of C-C bond formation in the couplings, is being used to produce assemblies of controlled size, shape, and functionality. Applications in host-guest chemistry, catalysis, anion binding, and supramolecular chemistry are being developed.