Ab initio study on the radical anions SO −3 and CO −2 and on the charge-transfer complexes MSO 3 and MCO 2 (M = Li, Na)

Abstract

The structures of the MSO 3 ion pairs (M = Li, Na) and the effects of coordination on the vibrational modes of the radical anion SO − 3 were examined by means of ab initio molecular orbital calculations. Both the bidentate and tridentate structures of LiSO 3 and NaSO 3 were predicted to be stable isomers and bidentate binding was inferred as the preferred coordination model. The stability of the lowest energy structures was tested against frozen-core UMP2, UMP3 and UMP4 calculations. Harmonic frequencies were calculated for the bidentate and tridentate LiSO 3 and NaSO 3 complexes and 34S and 18O frequency shifts reported for the two stable structures of NaSO 3. The study was extended to the radical anion CO − 2 and to the bidentate and monodentate isomers LiCO 2 and NaCO 2. The geometry, stability and vibrational spectra of the stable bidentate and monodentate isomers of LiCO 2 and NaCO 2 are discussed.