Synthesis and properties of tetraphenylethene cationic cyclophanes based on o-carborane skeleton

Two o-carborane based tetraphenylethene (TPE) cationic cyclophanes O1·4PF₆ and O2·4PF₆ were synthesized through an S_N2 reaction. Their structures were confirmed both possessing Z-shaped cavities in single crystal analysis. The optical properties of these macrocycles were systematically investigated using UV–vis spectroscopy and fluorescence techniques. It is worth noting that the introduction of a methoxy group to the TPE unit enables the synthesis of a near-infrared-emitting macrocycle O2·4PF₆. The recognition behaviors of these two macrocycles towards nucleotides were investigated using various techniques including fluorescence titration, UV–vis titration, and transmission electron microscopy (TEM). Interestingly, these cyclophanes exhibited aggregation-induced emission (AIE) effects in water or under the induction of nucleotides.