Polyphenylene Dendrimers: From Three-Dimensional to Two-Dimensional Structures

摘要

By making use of weak intermolecular forces and suitable reaction conditions, chemists have attempted to produce supramolecular structures from molecules of different shapes and sizes. In addition to stiff rodlike and spherical molecules, disk-shapedmolecules have attracted particular attention. This latter group includes polycyclic aromatic hydrocarbons (PAHs), which are characterized by their typical crystal packings and their stacking in discotic mesophases. We have recently developed routes to extended PAHs which enable the systematic alteration of the shape and size of the disks. The key step is the flattening of branched polyphenylene precursors to planar structures by means of cyclodehydrogenation. Here we describe the use of 3,4-bis[4-(triisopropylsilylethynyl)-phenyl]-2,5-diphenylcyclopentadienone (3c in Scheme 1) as a building block that can be used for the rapid construction of complex, highly branched polyphenylene structures and den-drimers by Diels-Alder cyclo-addition.