Journal of Chemical Physics vol:124 issue:21 pages:1-12
Quantum chemical calculations were applied to investigate the electronic structure of mono, di-, and trilithiated digermanium (Ge2Lin) and their cations (n=0-3). Computations using a multiconfigurational quasidegenerate perturbation approach based on complete active space self-consistent-field wave functions, and density functional theory reveal that Ge2Li has a B-2(1) ground state with a doublet-quartet energy gap of 33 kcal/mol. Ge2Li2 has a singlet ground state with a (3)A(u)-(1)A(1) gap of 29 kcal/mol, and Ge2Li3 a doublet ground state with a B-4(2)-(2)A(2) separation of 22 kcal/mol. The cation Ge2Li+ has a B-3(1) ground state, being 13 kcal/mol below the open-shell B-1(1) state. The computed electron affinities for diatomic germanium are EA((1)) = 1.9 eV, EA((2)) = -2.5 eV, and EA((3)) = -6.0 eV, for Ge-2(-), Ge-2(2-), and Ge-2(3-), respectively, indicating that only the monoanion is stable with respect to electron detachment, in such a way that Ge2Li is composed by Ge-2(-)center dot Li+ ions. An "atoms-in-molecules" analysis shows the absence of a ring critical point in Ge2Li. An electron localization function analysis on Ge2Li supports the view that the Ge-Li bond is predominantly ionic; however, a small covalent character could be anticipated from the analysis of the Laplacian at the Ge-Li bond critical point. The ionic picture of the Ge-Li bond is further supported by a natural-bond-order analysis and the Laplacian of the. electron density. The calculated Li affinity value for Ge-2 is 2.08 eV, while the Li+ cation affinity value for Ge-2(-) is 5.7 eV. The larger Li+ cation affinity value of Ge-2(-) suggests a Ge2-Li+ interaction and thus supports the ionic nature of Ge-Li bond. In GeLi4 and Ge2Li, the presence of trisynaptic basins indicates a three-center bond connecting the germanium and lithium atoms. (c) 2006 American Institute of Physics.