Mechanochemical Synthesis of Carbazole Isomer Phosphors

Abstract The 1H‐benzo[f]indole (Bd[f]), a carbazole (Cz) isomer is first reported as the source of Cz‐based phosphors in 2020. In this work, the novel carbazole isomers, 1H‐benzo[g]indole (Bd[g]) based derivatives, are synthesized by a one‐step solvent‐free mechanical ball milling reaction, establishing a facile, efficient, and environmentally friendly method for the synthesis of new Cz isomer phosphorescent derivatives with high yields compared to previously reported multi‐step solvent‐based thermochemical synthesis routes of Bd[f] derivatives with low yields. Six Bd[g] derivatives with different substituents, namely OCH 3 –Bd, In–Bd, Bn–Bd, F–Bd, Cl–Bd, and Br–Bd, are synthesized, which exhibit distinctly different single‐crystal structures and phosphorescent properties. After irradiation with 365 nm UV light, Bd[g] derivatives‐doped poly (methyl methacrylate) (PMMA) films exhibit photoactivated green room‐temperature phosphorescence with ultra‐long lifetimes up to 1.65 s. Interestingly, the phosphorescence is stable in seawater along with good bactericidal properties, which also provide new candidates for indole‐based marine antifoulants. This study demonstrates that mechanical ball milling is an efficient method for the synthesis of benzoindole heterocycles. Bd[g], as new members of the benzoindole family, are new building units to construct carbazole isomer phosphorescent molecules besides Bd[f].