Tetraphenylethylene Series|New Products|AmBeed

Tetraphenylethylene Series

Aggregation-induced emission (AIE) is a photophysical phenomenon in which luminescent materials exhibit weak emission in solution but strong emission upon aggregation. This phenomenon has garnered significant attention in the field of multifunctional luminescent materials. The primary working mechanism of AIEgens is currently understood to be the restriction of intramolecular motion (RIM), which can be further categorized into the restriction of intramolecular rotation (RIR) and the restriction of intramolecular vibration (RIV). Tetraphenylethylene (TPE) is a prime example of an AIE (Aggregation-Induced Emission) molecule that functions via the RIR (Restricted Intramolecular Rotation) mechanism. In solution, TPE molecules do not luminesce because the energy from the excited state is dissipated due to the rotational motion of its four phenyl ring rotors. Leung et al. hypothesized that if the phenyl rings of TPE molecules were immobilized by chemical bonds[1](Figure a), the luminescence quenching caused by molecular rotation in solution could be prevented. They conducted experiments using saturated and unsaturated alkyl chain segments as anchors perpendicular to the central double bond, synthesizing two derivatives: BDBA and THBDBA(Figure a). Both BDBA and THBDBA demonstrated typical AIE properties. Zheng and colleagues employed a unique method to immobilize the benzene ring rotator, synthesizing cis and gem TPE derivatives[2] (Figure b). In these derivatives, the two adjacent pairs of phenyl rings were restricted from rotation. The bridging moiety, aligned parallel to the central olefin double bond, emitted light in solution, whereas the TPE derivative with the bridging moiety perpendicular to the double bond still demonstrated AIE properties. They posit that this phenomenon results from the disruption of conjugation in the sp² electronic structure of the two carbon atoms forming the central double bond, which leads to the formation of a rotatable single bond in the excited state.

Tetraphenylethylene Series