Complex from ionic β-cyclodextrin polyrotaxane and sodium tetraphenylthiophenesulfonate: restricted molecular rotation and aggregation-enhanced emission

Abstract

Because restricted intramolecular rotation (RIR) is the main mechanism responsible for the aggregation-induced or -enhanced emission (AIE or AEE), we thus used a rigid polyrotaxane to impose effective RIR for an ionic, water-soluble and AEE-active luminogen of sodium 4,4′,4′′,4′′′-(thiophene-2,3,4,5-tetrayl)tetrabenzenesulfonate (TPS). Jeffamine-included β-cyclodextrin (JA-included β-CD) with cationic ammonium terminals was used as a rigid component to complex with the sulfonate anions of TPS, resulting in an iTP–CD-JA complex, which was used for characterization. Comparison was also made with a complex of iTP–JA prepared from the complexation of TPS with flexible JA chains. Without the incorporation of rigid β-CD rings, the emission efficiency of the iTP–JA complex was inferior to that of the iTP–CD-JA complex. The role of a rigid template in imposing effective RIR on an AEE-active luminogen was thus demonstrated in this study.