Conformation-tunable hydrogen-bonded calix[2]aramide macrocycles: bridging aggregation-induced emission and charge-transfer host–guest chemistry

Abstract

Two novel hydrogen-bonded calix[2]aramide (C[2]A) macrocycles were conveniently synthesized by linking crescent aramide trimers via methylene bridges. The macrocycles exhibited aggregation-induced emission and clusterization-triggered emission phenomena and enhanced solid-state luminescence efficiency superior to that of trimers. Notably, variations in skeletal conformations and cavity sizes of the macrocycles led to different host–guest binding behaviors toward the same guest. The complexation between macrocycle C[2]A-2 and the bipyridinium ion induced a bright green emission, attributed to the intermolecular charge transfer. This work expands the scope of the aramide macrocycles and enriches their optical properties.