Anion Photoelectron Spectroscopy and Theoretical Studies of Ge_3n+1O (n = 1–3) Clusters with the C_3v Symmetric Ge₃ Structural Unit

We investigate Ge3n+1O–/0 (n = 1–3) clusters using anion photoelectron spectroscopy and theoretical calculations. The results show that the lowest energy structure of Ge4O– is a bent Cs symmetric trigonal bipyramidal structure, while Ge4O has a C3v symmetric trigonal bipyramidal structure. Ge7O– has two coexisting low-lying isomers, the first one can be viewed as a Ge2O unit interacting with a Ge5 trigonal bipyramid, the second one can be regarded as an O atom interacting with a Ge7 pentagonal bipyramid; whereas Ge7O has a C3v symmetric structure with a Ge atom and an O atom capping a Ge6 trigonal antiprism from the bottom and top, respectively. The structures of Ge10O– and Ge10O can be obtained by adding an O atom to different binding sites of a C3v symmetric Ge10. Chemical bonding analyses of Ge3n+1O (n = 1–3) reveal that the O atom interacts with its neighboring three Ge atoms forming one 4c–2e σ bond and two 4c–2e π bonds in the top Ge3O trigonal pyramid, while the terminal Ge atom forms one 4c–2e σ bond in the bottom Ge4 trigonal pyramid. The large HOMO–LUMO gaps of Ge3n+1O (n = 1–3) indicate that they have good stabilities. Ab initio molecular dynamics simulations suggest that both Ge7O and Ge10O are dynamically stable in general at 300 and 500 K. The current work suggests that the C3v symmetric Ge3 units and the insertion growth pattern may be viable for constructing 1D germanium oxide nanostructures with the chemical formula of Ge3n+1O.