Facile synthesis of azobenzene-embedded conjugated macrocycles for optically switchable single-crystal transistors and tunable supramolecular assemblies

A series of newπ-conjugated macrocycles(AzoM-n-E,n 1–3)incorporating=azobenzene units have been synthesized by a facile strategy in one-pot reaction.The resultant azobenzene-embedded macrocycles feature intrinsic photoresponsive behaviors and intriguing supramolecular assembling properties.The smallest macro-cycle AzoM-1-E with a rigid planar conjugated backbone structure is used to prepare the single crystal transistors,showing reversible optical tunability.The moderate size macrocycle AzoM-2-E assembles into a dimer in the form of interpenetration throughπ-πstacking between azobenzene units.The largest macrocycle AzoM-3-E with enhancedflexibility can adaptively assemble with various types of electron-deficient guests accompanied by distortion of azobenzene.Typically,AzoM-3-E assembles with the planar F4-TCNQ to form a tetragonal geometry by C-F⋅⋅⋅π and π-π interactions,while the assembly with ellipsoidal C70 viaπ-πinteractions induces AzoM-3-E to form a boat-shaped geometry.This work will shed new light on the development of functional conjugated macrocycles in organic electronics.