The chemical desymmetrisation of two- and three-dimensional polyphenylenes as a key step to functional nanoparticles

Desymmetrisation of macromolecules is an important process in the preparation of functional nanoparticles for a variety of potential applications. Efficient routes for the directed stepwise synthesis of desymmetrised functional two- and three-dimensional polyphenylenes are here presented. Building blocks substituted with different functional groups have been prepared and combined to make functionalised hexaphenylbenzenes. Cyclodehydrogenation of these gives unique hexa-peri-hexabenzocoronenes with different types of substituents in various substitution patterns. These show remarkable phase-forming properties, which can be controlled through their substitution patterns, making them attractive candidates for use in electronic aplications. Selective silylation of a tetrahedrally symmetric core molecule followed by stepwise addition of substituted dendrons leads to dendrimers selectively functionalised on the periphery by different functional groups in well-defined spatial relationships to each other. By this method dendrimers have been made with two diffferent chromophores permitting study of energy transfer processes, and dendrimers with functional groups permitting their attachment to electrodes or biological systems with posssible applications as biosensors.