Carbon dioxide fixation by copper and silver halide. Matrix-isolation FTIRspectroscopic and DFT studies of the XMOCO (X = Cl and Br, M = Cu and Ag) molecules

The ClCuOCO and BrCuOCO molecules have been observed by cocondensation of t he species generated from 1064 nm laser ablation of CuCl2 and CuBr2 targets with CO2/Ar mixtures. With the aid of density functional calculations and isotopic substituted experiments, infrared absorptions at 2383.9 and 2381.4 cm(-1) are assigned to the antisymmetric CO2 stretching vibrations of the ClCuOCO and BrCuOCO molecules in solid argon, respectively, Theoretical cal culations predicted these molecules to be linear with a (1)Sigma (+) ground state. The interaction between CuX and CO2 is mainly electrostatic and thu s induces a blue shift of the CO2 antisymmetric stretching vibration. The b inding energies for ClCuOCO and BrCuOCO with respect to those for CuX and C O2 were calculated to be 12.5 and 11.4 kcal/mol, respectively. Similar expe riments with AgCl and AgBr gave the analogous ClAgOCO and BrAgOCO. The bind ing energies were estimated to be 6.5 and 5.9 kcal/mol for ClAgOCO and BrAg OCO, respectively.