Revealing the internal heavy chalcogen atom effect on the photophysics of the dibenzo[a,j]phenazine-cored donor–acceptor–donor triad

A new twisted donor–acceptor–donor (D–A–D) multi-photofunctional organic molecule comprising phenoselenazine as the electron donor (Ds) and dibenzo[a,j]phenazine (DBPHZ) as the electron acceptor (A) has been developed. The developed selenium-incorporated D–A–D compound features multi-color polymorphism, distinct mechanochromic luminescence, chemically-stimulated luminochromism, thermally-activated delayed fluorescence, and room-temperature phosphorescence. The internal heavy atom effect on the photophysical properties of the D–A–D system has been investigated through a comparison with the physicochemical properties of a previously developed sulfur analogue and a tellurium analogue.