AB-INITIO STUDY OF THE HCO3- H2O EXCHANGE-3 IN THE (NH3)(3)ZN-II(HCO3-) COMPLEX/

The displacement of bicarbonate anion in the (NH3)(3)Zn-II(HCO3-) comp lex with water has been studied through ab initio calculations. It has been found that H2O binds to the (NH3)(3)Zn-II(HCO3-) species yieldin g a stable pentaco ordinate (NH3)(3)Zn-II(HCO3-)(H2O) complex. The res ults also indicate that deprotonation of water in the pentacoordinate species facilitates the release of HCO3-, although, the presence of HC O3- in the coordination sphere of Zn-II makes such deprotonation more difficult. Environmental effects have been considered in the study of HCO3/H2O exchange.