Abstract

The monomeric species, [CuII{Hx (tmdnTAA)}] z+ (x = 0, 1, and 2, and (tmdnTAA)2- = [5,7,12,14]-tetramethyldinaphtho[b,i][1,4,8,11]tetraaza[14]annulenato(2-) = 7,9,18,20-tetramethyldinaphtho[2,3-b :2',3'-i] [1,4,8,11] tetraazacyclotetradecinato(2 -)) catalyze the electrochemical reduction of SO2(aq) in homogeneous solution. A pulse-radiolytic study of the reaction of the [Cu1(tetraazaannulene)] complexes with SIV species revealed the formation of CuI-SO2 adducts. The formation of CuI-SO2 adducts prevents the disproportionation of the Cu1 complexes and precedes the reduction of the SIV species to S2O2- 4. DFT Calculations were carried out to establish the structure and stability of the CuI-SO2 adducts. A good agreement between the calculated and recorded electronic spectrum of the CuI-SO2 adducts corroborated the formation of species with SO2 coordinated to Cu I through the O-atom. © 2009 Verlag Helvetica Chimica Acta AG, Zurich.