Rigid Jeffamine-included polyrotaxane as hydrogen-bond template for salicylideneazine with aggregation-enhanced emission

Abstract

Because restricted molecular rotation is the main mechanism responsible for aggregation-induced emission (AIE), a Jeffamine-included polyrotaxane (JCD) was therefore used in this study as a rigid template to impose effective rotational restriction on the AIE-active luminogen of 1,2-bis(2,4-dihydroxybenzylidene)hydrazine (CN₄OH). Besides rigidifying the flexible Jeffamine chain, the β-cyclodextrin (β-CD) rings of JCD also provided hydroxyl (OH) groups to hydrogen bond to the OHs of CN₄OH, furnishing emissive CN₄OH/JCD(x/y) (x/y: molar ratio between CN₄OH and JCD) blends with emission efficiency higher than the pure CN₄OH itself. Dependent on the composition of the blends, CN₄OHs in the blends are arrayed differently to experience varied levels of rotational restriction and thus emit with an intensity correlated with the molecular arrangement of the CN₄OHs in the blends. The relationship between molecular arrangement, restricted molecular rotation and AIE-oriented emission behavior is the focus of this study.