Spacial structures induced by sterical hindrance of large substituents : a dendritic macromolecular “snowflake” molecule

Abstract

The mulitstage preparation of densly packed thienylene-phenylene dendrimer 15 comprising 42 thiophene and 7 benzene units arranged in a hexagonal “snowflake” fashion is described. The desired three-dimensionality is induced through steric repulsion of the peripheral hexa(thienyl)benzene units. The molecular geometry of individual dendrimers was supported by quantum chemical calculations, whereby atomic force microscopy gave evidence for spontaneous ordering of the molecules on a graphite surface by the formation of stable nanosized edge-on oriented columns.