RELATIVISTIC EFFECTS IN CATIONIC GOLD(I) COMPLEXES - A COMPARATIVE-STUDY OF AB-INITIO PSEUDOPOTENTIAL AND DENSITY-FUNCTIONAL METHODS

The cationic gold(I) complexes Au+(H2O), Au+(CO), Au+(NH3), and Au+(C2H4) have been examined by different ab initio and density functional methods using nonrelativistic and relativistic ECPs and a quasi-relativistic approach, where relativistic effects are explicitly taken into account. On the one hand, Au+(H2O) and Au+(CO) exhibit binding energies (35.9 and 44.1 kcal/mol, respectively, at the CCSD(T) level of theory) which are comparable with those of the complexes of the group 11 congeners Cu+ and Ag+ While for Au+(NH3) and Au+(C2H4) a large relativistic stabilization is observed, such that the binding energies (65.3 and 68.8 kcal/mol, respectively, at the CCSD(T) level of theory) are almost twice as high as for M(+)(NH3) and M(+)(C2H4) for M = Cu and Ag. With respect to the computational methods applied, structural features and energetics obtained with different ab initio (MP2, CCSD(T)) and DFT (ADF/BP, B3LYP) methods are in reasonable agreement with each other. In general, the relativistic effects on structures and energetics of these gold(I) compounds are quite large, and the interplay of electron correlation and relativistic effects is discussed.