Alkoxy Substitution Controls Columnar Organization in Quinoxaline Cyclotetrabenzoin Macrocycles

Abstract

Shape-persistent quinoxaline macrocycles were synthesized from cyclotetrabenzil through condensations with substituted phenylenediamines. Variation of peripheral alkoxy substituents systematically modulates supramolecular organization in the solid state. Selected tetraalkoxy macrocycles form ordered soft crystal columnar hexagonal phases, whereas octaalkoxy derivatives exhibit more diverse phase behavior. Notably, a branched 3,7-dimethyloctyl derivative displays a columnar oblique liquid-crystalline phase. Single-crystal structures reveal layered packing governed primarily by weak [C–H···O], [C–H···N], and [C–H···π] interactions. These results demonstrate that macrocycle size and side-chain architecture influence columnar packing and phase behavior in quinoxaline macrocycles, with the branched octaalkoxy derivative uniquely exhibiting a liquid-crystalline mesophase.