Triplet germylenes with separable minima at ab initio and DFT levels

Six ground state triplet germylenes, with HGeX and GeX2 formulae, are reached at QCISD(T)/6-311++G** and B3LYP/6-311++G** levels of theory (X = Li, Na, and K). Their corresponding less stable electronic isomers appears as singlet germylene minima. Scanning Ф as a function of energy for every triplet species gives two energy minima, separated by significant energy barriers. The same scanning gives merely one minimum for most singlet species, at the potential energy hyper-surface. Thus, only the open-shell (σ1π1) triplet states exhibit bond-angle isomerism, since no such isomers could be found for the (σ2π0) singlet states except for singlet GeLi2 which shows a possible covalent bonding interaction between the two Li atoms. All triplet XGeX species appear more linear than their corresponding triplet HGeX. As the electro-positivity of X increases, the GeX bond distances in all species lengthen, while their singlet-triplet energy separations (ΔEs-t) decrease, with the lowest ΔEs-t given for HGeK. The ΔELUMO-HOMO for singlet HGeX and GeX2 species appear inversely proportional to the size of X, showing a trend of K > Na > Li. Interestingly, for both singlet HGeX and GeX2 species, linear correlations are found between the ΔELUMO-HOMO and their corresponding ΔEs-t,X.