Germylenes: Structures, Electron Affinities, and Singlet-Triplet Gaps of the Conventional XGeCY3 (X = H, F, Cl, Br, and I; Y = F and Cl) Species and the Unexpected Cyclic XGeCY3 (Y = Br and I) Systems

A systematic investigation of the X-Ge-CY3 (X = H, F, Cl, Br, and I; Y = F, Cl, Br, and I) species is carried out using density functional theory. The basis sets used for all atoms (except iodine) in this work are of double-zeta plus polarization quality with additional s- and p-type diffuse functions, and denoted DZP++. Vibrational frequency analyses are performed to evaluate zero-point energy corrections and to determine the nature of the stationary points located. Predicted are four different forms of neutral-anion separations: adiabatic electron affinity (EA(ad)), zero-point vibrational energy corrected EA(ad(ZPVE)), vertical electron affinity (EA(vert)), and vertical detachment energy (VDE). The electronegativity (chi) reactivity descriptor for the halogens (X = F, Cl, Br, and I) is used as a tool to assess the interrelated properties of these germylenes. The topological position of the halogen atom bound to the divalent germanium center is well correlated with the trend in the electron affinities and singlet-triplet gaps. For the expected XGeCY3 structures (X = H, F, Cl, Br, and I; Y = F and Cl), the predicted trend in the electron affinities is well correlated with simpler germylene derivatives (J. Phys. Chem. A 2009, 113, 8080). The predicted EA(ad(ZPVE)) values with the BHLYP functional range from 1.66 eV (FGeCCl3) to 2.20 eV (IGeCF3), while the singlet-triplet splittings range from 1.28 eV (HGeCF3) to 2.22 eV (FGeCCl3). The XGeCY3 (Y = Br and I) species are most often characterized by three-membered cyclic systems involving the divalent germanium atom, the carbon atom, and a halogen atom.