A novel triplet germylene F₃C{single bond}over(Ge, ̈){single bond}Ge{triple bond, long}Ge{single bond}H at theoretical levels

F₃C{single bond}over(Ge, ̈){single bond}Ge{triple bond, long}Ge{single bond}H, with two unpaired electrons, is the only triplet (t) ground state germylene found among 30 divalent species, with XHGe₃ formula, at six reasonably high ab initio and DFT levels (X = H, NH₂, SiH₃, and CF₃). Its corresponding singlet (s) appears at a higher energy while showing a negative force constant. The crossing angle (F{cyrillic}) between the above s and t states is 90°. Replacement of CF₃ with H and NH₂ increases F{cyrillic} to 120° and 160°, respectively. No crossing of the s and t states occurs for H₃Si{single bond}Ge{single bond}Ge{triple bond, long}Ge{single bond}H, whose s state is its global minimum. Having X directly attached to the divalent germylene in X{single bond}Ge{single bond}Ge{triple bond, long}Ge{single bond}H, increases the X effects on ΔE_s-t,X compared to the isomeric species: 3-X-1,2,3-trigermapropargylene, 3-X-1,2,3-trigermavinylidene and 2-X-1,2,3-trigermacyclopropenylidene, respectively. Nonetheless, the latter cyclic divalent species appear relatively more stable with the highest LUMO-HOMO energy gaps, while their NICS calculations show their aromatic character change as a function of X (SiH₃ > H > CF₃ > NH₂). Finally, the global minimum among the 30 isomeric XHGe₃ is found to be SiH₃ substituted singlet trigermacyclopropenylidene.