Tetraphenylethylene-Carborane-Tetraphenylethylene Triad: Influence of Steric Bridge on Aggregation-Induced Emission Properties.

A novel tetraphenylethylene (TPE)-bridge-tetraphenylethylene triad has been synthesized, where the o-carboranyl moiety functions as a central bridge and two TPE units are in the lateral positions. This molecular triad has been characterized by various spectroscopic methods, and its structure has been studied by X-ray crystallography as well as theoretical calculations. The impact of the bridging carboranyl unit on the aggregation-induced emission (AIE) characteristics of the TPE-bridge-TPE triad has been investigated. When the central bridge is changed from one-dimensional (1D) alkynyl to three-dimensional (3D) carboranyl, the absolute luminescent quantum yield of the triad increased from 21.2 % to 54.7 % in the solid state, accompanied by a luminescence color change from blue to yellow (94 nm red-shift).