α-Cyanostilbene: a multifunctional spectral engineering motif

Abstract

Aggregation-induced emission (AIE) is a unique photophysical phenomenon of organic molecules exhibiting significant emission enhancement in the condensed phase (aggregate/solid/film) than in the solution phase. This remarkable feature offers excellent strategies to obtain the molecular materials possessing unique spectral signatures such as high fluorescence intensity, excellent quantum yield, large Stokes shift, and exquisite optoelectronic properties. Unlike a great library of articles with propeller-shaped tetraphenylethene molecular framework, reviews based on the mechanistic understandings of α-cyanostilbenes are relatively few. Considering the lacuna, we highlight the structure-property relationship of the α-cyanostilbene-based AIE frameworks for tuning the aggregation through molecular displacement with reference to the transition dipoles based on the following parameters: i) positional substitution and orientation of the α-cyano unit; 2) π-conjugation length (da or db) and molecular size (DAr) of the peripheral substitutions to the α-cyano unit, and 4) branching effect. In addition, we elaborated on the utility of its unique AIE emission characteristics for various optoelectronic applications, including self-assembled nanostructures, chemical sensing, organogelation, white light emission, molecular switches, multiphoton absorption, liquid crystals, anion receptors, and biological probes. It is anticipated that organic materials with a cyanostilbene framework shall continue to garner attention in the interdisciplinary fields of biology, chemistry, and materials for diverse applications.