Divalency switch from carbenes to germylenes at theoretical levels

Acyclic germylenes with XCCGeX formula, and singlet (Xs) and triplet (Xt) states are generated at ab initio and DFT levels, through free optimization of their corresponding cyclic singlet and triplet carbenes: 2,3-di(X)-2-germacyclopropenylidenes, 1s and 1t, respectively (X = F, Cl, and Br). The calculated frontier molecular orbitals, bond orders, NBO charges, and dipole moments are consistent with the XCCGeX structure. Their relative stabilities and the singlet (s)-triplet (t) energy splitting (ΔEs-t) indicate singlet states (Xs) as the global minima for all the acyclic germylenes scrutinized.