“…Finally, [2,1- b ]-103 with a 4π-3spiro architecture (four π-systems connected thanks to 3 spiro-bridges) was very recently designed and tested in TADF-OLED21–22 also with interesting performances. 218 As expected, the HOMO and HOMO-1 are spread on the two acridine units and the LUMO on the triphenyltriazine substituent. For this emitter Δ E ST is 0.02 eV, the decay profile exhibits two components corresponding to prompt (27 ns) and delayed fluorescence (3.2 μs) and the rate constant of radiative decay and reverse intersystem crossing are similar to those of [2,1- b ]-101-[2,1- b ]-102 (Scheme 25) suggesting efficient device performances.…”