Ab initio study on the coordination structures of AsO 3−, VO 3− and CO 32− with alkali cations

Abstract

This study reports the results of an ab initio Hartree-Fock - Self-Consistent-Field study carried out on D 3h symmetry AsO 3 −, VO 3 − and CO 3 ·- and on the coordination structures of these anions with alkali cations. Geometry optimizations and vibrational frequencies were calculated from polarized split-valence basis sets. Bidentate, monodentate and tridentate coordination structures were considered for LiAsO 3, LiVO 3, Li 2CO 3, Na 2CO 3 and LiNaCO 3. Bidentate binding is the most stable coordination structure for all the molecules, whereas the monodentate structures of Li 2CO 3, Na 2CO 3 and LiNaCO 3 are first-order saddle points with regard to the in-plane migration of the metal atom and are the transition states between equivalent bidentate structures. Monodentate LiAsO 3 and LiVO 3 are second-order saddle points with respect to the in-plane and out-of-plane motion of the alkali metal. The trigonal pyramidal structures of all the molecules are the highest energy configurations and are higher-order saddle points. This work includes MP2/6-31G ∗ geometry optimizations of the bidentate coordination structures of HCO 2Li, HCO 2Na, LiNO 2, NaNO 2, LiPO 2, LiClO 2, LiSO 2, NaSO 2, LiBO 2, NaBO 2 and of LiNO 3 and LiPO 3.