A photoexcited triplet state germylene with a half-life of hours at room temperature.

Triplet state tetrylenes posess significant potential for transforming chemically inert substrates, but their fleeting nature has limited their detection beyond low-temperature matrix environments, making the study of their physical and chemical properties challenging. This challenge is exacerbated in heavier tetrylenes, such as germylenes, due to their higher singlet-triplet (S1-T1) energy gaps. Here we report the photoinduced generation of a long-lived triplet germylene with a 14-h half-life time at room temperature, achieved through an excited singlet-triplet trap stabilization strategy. The metastable nature of this excited state enabled its spectroscopic investigation and the study of its reactivity. Compared with the ground state, enhanced reactivity is observed, including the cleavage of N=N, C-Br, Si-H and even C-C bonds in a doubly reductive cleavage of benzene.