Chalcogen-Influenced Benzochalcogenazolo-Based ,-Coordinated Difluoroboron Complexes: From Lasing Dyes to Room-Temperature-Phosphorescence Emitters.

Four ,-coordinated benzochalcogenazolo-based boron difluoride complexes were designed, synthesized, and spectroscopically investigated in solutions, crystalline state, and dye-doped poly(methyl methacrylate) films. The single crystal analysis revealed that oxadiazaborinine dyes adopt planar geometry with multiple intermolecular hydrogen-bonding interactions. The benzoxazole- and benzothiazole-containing dyes exhibit highly intensive photoluminescence in the crystalline state and when dispersed in the inert polymer, accompanied by high-rate constants of radiative deactivation (2.2 × 10 s and 2.7 × 10 s, respectively). This results in their amplified spontaneous emission ability with very low thresholds of 11 and 4.7 μJ/cm, respectively, and very narrow bandwidths with the values of full widths at half maxima of 10 and 6.3 nm. In stark contrast, the benzotellurium-containing analogue shows room temperature phosphorescence with a short phosphorescence lifetime of 9.4 μs, caused by the strong chalcogen heavy-atom effect.