BINOL-based chiral aggregation-induced emission luminogens and their application in detecting copper(ii) ions in aqueous media

Abstract

Two novel chiral luminogens BINOM-CN and BINOP-CN derived from (R)-1,1′-binaphthol (BINOL) with aggregation-induced emission (AIE) characteristics were designed and synthesized. Dicyanomethylene and the substituent of the hydroxyl group have been found to be the key structural element for this unique AIE effect. Meanwhile, these two chiral AIE luminogens exhibit abnormal aggregation-induced annihilation of the circular dichroism (CD) signal, which is ascribed to the decrease of the dihedral angle between adjacent naphthalene rings in the aggregation state. With the assistance of the pyridine unit, BINOP-CN can serve as an excellent sensor for Cu²⁺. In the presence of Cu²⁺, the fluorescence intensity and CD signals of BINOP-CN both decreased observably due to its ideal coordination with Cu²⁺, which was further confirmed by X-ray crystallography. Moreover, the addition of Cu²⁺ can induce the self-assembly of BINOP-CN.