Pressure-Induced Emission Enhancement and Piezochromism of Triphenylethylene

Pressure-induced emission enhancement (PIEE) is a new phenomenon that has attracted widespread attention in the past few years for improving the solid-state emission efficiency of fluorophores. However, a thorny issue still remains in the study of PIEE. Thus, it is urgent and important to discover and design more PIEE systems for further enhancing the efficiency. In this paper, we found that triphenylethylene (TriPE) showed both conspicuous emission enhancement within the pressure range of 0.0–0.8 GPa and piezochromism behavior upon compression. More interestingly, infrared (IR) analysis indicated that ring-opening reaction of the phenyl ring occurred when pressure was beyond 14.2 GPa. Also, the ring-opening reaction of the phenyl ring led to irreversible optical changes. In situ high-pressure IR spectroscopy and angle-dispersive X-ray diffraction analysis demonstrated that the PIEE of TriPE was attributed to the related C–H···π and C–H···C hydrogen bonds that could inhibit or restrict the movement of aromatic parts remarkably, restraining the energy loss by intramolecular motion. Our study provides insights into the significant effect of intermolecular interactions on fluorescence emission properties.