Room temperature phosphorescence, thermally activated delayed fluorescence and multicolor mechanochromic luminescence of emitters through molecular interaction and conformational modulations

Two novel heavy atom-free pure organic pyrimidine-based asymmetric donor-acceptor type emitters were designed and synthesized. The twisted D-A conformation was favored to produce small ΔE st and effective ISC. Excitingly, PMBT and CzPMBT showed precious fluorescence-RTP-TADF triple emission. Furthermore, PMBT responded to external stimuli of volatile solvents fumigation and different intensity grinding to generate a multicolor switching system, which included charming white light due to the dual emission of fluorescence and phosphorescence. Crystallographic analysis was conducted to explain the reasons for the differences in photophysical properties produced by the two compounds. This research provides insight into the mechanism of action of RTP, TADF and multicolor MCL through intermolecular interactions and conformational modulation. • Two asymmetric D-A type derivatives based on pyrimidines were synthesized. • Two emitters achieved the fluorescence-RTP-TADF triple emission. • PMBT implemented a multicolor switching system including white light emission.