Purely Organic Room-Temperature Phosphorescence Endowing Fast Intersystem Crossing from Through-Space Spin-Orbit Coupling

Purely organic room-temperature phosphorescence endowing very fast intersystem crossing from through-space systems has not been well investigated. Here we report three space-confined bridged phosphors, where phenothiazine is linked with dibenzothiophene, dibenzofuran, and carbazole by a 9,9-dimethylxanthene bridge. Nearly pure phosphorescence is observed in the crystals at room temperature. Interestingly, phosphorescence comes solely from the phenothiazine segment. Experimental results indicate that bridged counterparts of dibenzothiophene, dibenzofuran, and carbazole contribute as close-lying triplet states with locally excited (LE) character. The throughspace spin-orbit coupling principle is proposed in these bridged systems, as their (LE)-L-1 and (LE)-L-3 states have intrinsic spatial overlap, degenerate energy levels, and tilting face-to-face alignment. The resulting effective through-space spin-orbit coupling leads to efficient intersystem crossing a with rate constant as high as 10(9) s(-1) and an overwhelming triplet decay channel of the singlet excited state.

Automated summary

This study reports three space-confined bridged phosphors that exhibit nearly pure phosphorescence at room temperature. Experimental results indicate efficient intersystem crossing in these systems, with the main phosphorescence originating from the phenothiazine segment.