Aggregation-Induced Emission Luminogens Based on Restriction of Intramolecular Vibration.

Over the past two decades, high-performance materials with aggregation-induced emission (AIE) characteristics have emerged as indispensable components in modern functional materials science. Among them, AIEgens based on the restriction of the intramolecular rotation (RIR) mechanism have been thoroughly studied and developed. AIEgens operating via the restriction of the intramolecular vibration (RIV) mechanism have emerged as a promising yet underexplored class; however, they remain constrained by a limited repertoire of molecular scaffolds and poorly defined design principles. This outlook categorizes reported RIV-type AIEgens into four types based on a geometry-oriented classification of molecular deformation modes: structural inversion driven by aromaticity, bending, twisting, and molecular bond vibration. The representative structures and underlying RIV mechanisms are elaborated in detail, aiming to establish a framework for the rational design and functional expansion of next-generation RIV-type AIEgens, with the ultimate goal of broadening their applications in optoelectronics and biomaterials.