Synthesis of carbon nanohoops containing thermally stable cis azobenzene

Abstract

Cycloparaphenylenes (CPPs) have been praised for their size-tunable HOMO/LUMO gap and associated electronic and optical properties, and have generated significant interest for small-molecule electronics. Another fascinating but less-explored prospect for CPPs involves exploiting their hollow geometry. With a rigid pore of tunable size and high electron density arising from the inward facing π-orbitals, CPPs are ideal for electron-poor guests. [10]CPP in particular has shown very high binding affinity for fullerene C60. The ability to reverse this encapsulation by external stimuli is an important next step. Herein we report the design and synthesis of two CPPs containing thermally stable cis azobenzene moieties in the conjugated framework, their behavior upon irradiation, and computational results evaluating their potential as photoswitchable fullerene hosts.