Synthesis and photophysical properties of donor-substituted phenyl-phosphachromones as potential TADF materials

A series of novel arylamine-substituted phenyl-phosphachromones were constructed via post-functionalization. As a new type of D–π–A functional molecule, their photophysical properties can be well tuned by different amino substituents at different positions with variable Stokes shifts (Δλ = 127–299 nm). Moreover, compounds 4a, 4b, 4f, 4m, and 4n exhibit an unusual dual emission with a large wavelength difference. Strong intermolecular interactions were also observed for these compounds, and therein, a sandwich π(donor)–π(donor) stacking interaction was found in the solid-state structure of 4e. Moreover, (TD-)DFT computations were performed to rationalize the observed electronic properties and intramolecular interactions. Finally, the delayed fluorescence of these D–π–A molecules in the film was observed and further confirmed to be a result of thermally activated delayed fluorescence and mixed room-temperature phosphorescence.