CH/π-interaction-driven self-assembly of tetraphenylethylene derivatives into the face to face arrangement

For tetraphenylethene (TPE) derivatives, it is difficult to determine the arrangement of the molecules in the aggregation state because disordered aggregation usually occurs. To solve the problem, we have explored a novel and facile strategy to investigate the aggregation mode of a TPE derivative framework in which the two neighboring ortho carbons of two phenyl moieties at the same ethylene carbon were linked with an alkoxyl chain (C4) (denoted as TPEC4). The XRD measurements on the particles obtained in a DMSO/H₂O mixture (f _w = 60%) showed sharp peaks which is consistent with the simulated XRD patterns on the basis of a single crystal structure of TPEC4, indicating well-ordered molecular packing in the aggregated state. The CH/π-interaction and solvophobicity driven self-assembly behaviour of the compound was observed in the DMSO/H₂O mixture. A face to face molecular packing structure that arises from quadruple intermolecular CH/π-interactions of the tetraphenylethylenes is the key motif for self-assembly in solution. The unique blue-red shifted emission in the DMSO/H₂O mixture associated with aggregated behaviour of the compound was also investigated. This discovery will provide the basis for theoretical research and the rational design of TPE-based luminogens.