Cyclic M(SO2) (M=Zn, Cd) and its Anions: Matrix Infrared Spectra and DFT Calculations

Abstract

Reaction of laser ablated zinc and cadmium atoms with SO2 molecules was studied by low temperature matrix isolation infrared spectroscopy. Cyclic M(SO2) and anion M(SO2)− (M=Zn, Cd) were produced in excess argon and neon, which were identified by 34SO2 and S18O2 isotopic substitutions. The observed infrared spectra and molecular structures were confirmed by density functional theoretical calculations. Natural charge distributions indicated significant electron transfer from s orbitals of zinc or cadmium metal atom to SO2 ligand and cyclic M(SO2) complexes favored “ion pair” M+(SO2)− formation, which were trapped in low temperature matrices. In addition Zn-O or Cd-O bond in M(SO2) exhibited strong polarized covalent character. Reaction of Hg atom with SO2 was also investigated, but no reaction product was observed, due to the relativistic effect that resulted in the contraction of 6s valence shell and high ionization potential of Hg atom.