Synthesis and Optical Properties of Stable Gallafluorene Derivatives: Investigation of Their Emission via Triplet States

We designed and synthesized air- and moisture-stable gallafluorenes in which two benzene rings were bridged by the four-coordinate gallium atoms. The series of gallafluorenes were prepared by introducing electron-donating and -withdrawing groups through Suzuki–Miyaura coupling reactions. The gallafluorenes showed unique emissions via their triplet states in the presence of B­(C6F5)3. These emissions were obtained via the triplet exciplex of gallafluorene and B­(C6F5)3.