Classic Annulenes, Nonclassical Applications

This Account details the application of [n]annulenes as functional building blocks for electromechanical actuators, double-helical ladder polymers, and protecting groups for supramolecular interactions. Specifically, redox-induced conformational changes occurring in [8]annulenes are utilized as the transducing element in polymeric electromechanical actuators. Conversely, rigid [8]annulenes are utilized as double-helical fragments for the synthesis of double-helical octaaryl macromolecules. Last, Dewar benzenes are prepared from [4 + 2] cycloadditions (where the 4pi component is a [4]annulene). The potential of using Dewar benzenes as protecting groups for [6]annulne-[6]annulene supramolecular interactions is exemplified by demonstration of photolithographic crystallization (amorphous [4]annulene --> crystalline [6]annulene) on a surface, followed by subsequent X-ray analysis of the resulting [6]annulene crystals.