Effect of bridge unit on photo-properties of tetraphenylethene-benzothiazole hybrid AIEgens with high-contrast mechanofluorochromic behaviour

Abstract

The tetraphenylethene-benzothiazole hybrid AIEgens (TP and TPM) with different bridge units (carbonyl or dicyanoethylene) have been designed and synthesized to systematically investigate the effect of bridge units on their fluorescence properties. These molecules are demonstrated to have non-planar twisted structures and exhibit aggregation-induced emission (AIE) characteristic. Upon grinding, the pristine form of TP and TPM show 24 nm and 74 nm red shift in the fluorescence spectra, respectively, revealing MFC characteristic. PXRD, SEM, crystal structures and DFT calculations studies provided further insight on the MFC behavior. The MFC behavior of TPM exhibits large red shift and obvious color change compared to TP as the bridge unit was changed from carbonyl to dicyanoethylene indicating better ICT and strong π stacking in former. This work implies that the introduction of different bridge units to a specific molecule structures might be useful as a feasible strategies for designing high-contrast MFC-active materials.