Elucidation of distinct fluorescence and room-temperature phosphorescence of organic polymorphs from benzophenone-borate derivatives.

The development of organic room-temperature phosphorescence (RTP) is accompanied by opportunities and challenges. RTP from crystal polymorphism has aroused much attention, due to the significant different photophysical characteristics and intermolecular packings found in the same molecule with different crystal phases. Herein, we report three organic molecules BP-o-BO, BP-m-BO, and BP-p-BO, in which two crystal polymorphisms of BP-p-BO are successfully cultivated with different emission properties. BP-p-BO-A exhibits bright cyan photoluminescence (PL) with a quantum yield of 11.3% and a distinct RTP with a lifetime of 17.1 ms, which is much higher than the deep blue PL of BP-p-BO-B (6.9%) and the corresponding RTP lifetime of 3.3 ms. Crystal structure analyses indicate that the different emission properties can be ascribed to the different intermolecular packing, further demonstrating the essential role of molecular packing in the designing of RTP materials.