An Exceedingly Long-Lived Photoexcited Triplet State Germylene with a Half-life of Hours at Room Temperature

Triplet state tetrylenes are highly promising candidates for the transformation of chemically inert substrates, but their fleeting nature has precluded their detection beyond low-temperature matrix environments, thereby hindering the study of their physical and chemical properties. This challenge is exacerbated in heavier tetrylenes (HTs), such as germylenes, due to higher singlet-triplet (S1-T1) energy gaps. Here we report the photoinduced generation of a truly long-lived triplet germylene with a 10-hour half-life time at room temperature, achieved via an excited singlet-triplet trap stabilizing strategy. This metastable excited state facilitated detailed investigations and revealed greatly enhanced reactivity compared to the ground state, including cleavage of C–N, C–Br, Si–H and even C–C bonds in an exotic doubly reductive cleavage of benzene.