Deep-blue emission and thermally activated delayed fluorescence via Dimroth rearrangement of tris(triazolo)triazines

Three luminescent donor-acceptor compounds were prepared based on the Dimroth rearrangement of tris(triazolo)triazines (TTT). In comparison to the non-rearranged TTT isomers, the Dimroth isomer (TTTD) exhibits a substantial blue-shift in emission while maintaining thermally activated deLayed fluorescence (TADF) properties. Out of the series of emitters, TTTD-3HMAT exhibits deepest blue emission with CIE(x, y) < (0.16, 0.03) and unity quantum yield in toluene, a narrower emission band, and highest two-photon cross-section of 1001 GM owing to the nature of the Nanarized HMAT donor. TTTD-3tBu also exhibits unity quantum yield and deep-blue emission with CIE(x, y) < (0.16, 0.05) in toluene. Finally, TTTD-3ACR exhibits TADF with blue-shifted emission and prolonged delayed Lifetime due to the slightly larger Delta E-ST of 0.26 eV in comparison to the non-rearranged isomer. Overall, this work demonstrates a practical strategy to convert TTT-based donor-acceptor materials to their Dimroth isomers, opening the door to deeper blue-emitting TADF materials with TTT-type acceptors.