Flexible and Continuous Regulation Promoting Remarkably Emission Enhancement of Planar Triphenylene

The photophysical properties of π-conjugated materials in aggregate states are heavily dependent on molecular arrangements. Accordingly, the regulation of molecular packing is an essential issue for achieving optimized optical properties, especially the related adjustment of π–π interactions. Herein, triphenylene (TPhE) with the planar structure was presented as an ideal model, in which the molecular packing was regulated continuously by the exogenous stimulation, as monitored by the uncommon and conspicuous emission enhancement, which should be attributed to the enhanced excimer yielded by the pressure-induced strengthening π–π interactions. Additionally, the different fluorescence behaviors of cocrystal based on TPhE and tetrafluoroterephthalonitrile (TFTP) under high pressure further illustrated the important role of enhanced excimer formation in fluorescence enhancement. To the best of knowledge, this research is the first example with pressure-induced emission enhancement (PIEE) feature of polycyclic aromatic hydrocarbon (PAH) without heteroatom, which revealed the evolution of an excimer with its intrinsic photophysical properties, and provided deep insights into the packing-property of π-conjugated materials in aggregates.