AB-INITIO STUDY OF THE ELECTRONIC-STRUCTURE OF THE (SO2)(SO2-) DIMER - A ONE-ELECTRON S-S-BOND FORMATION

The structure of the (SO2) (SO2-) anion with a S-S linkage is studied by means of ab initio calculations at the PUMP4/6-31+G//UMP2/6-31+G* level. The trans structure is found to be a minimum on the potential e nergy surface and is mainly characterized by a long (286 pm) one-elect ron SS bond. The theoretical dimerization enthalpy is in agreement wit h experiment. Moreover, this structure in which the unpaired electron is used to bind the sulfur atoms might well explain the smaller enthal py variations associated with further addition of SO2 molecules.