Theoretical Study Of The Nature Of The Bonding Interactions Between Cu/Ag/Au-containing Compounds And Small

Gold、silver and copper compounds play an important role in chemical industrybecause of their unique characteritics. Haruta reported their prior study about goldnanomaterials, which performs catalytic properties at carbonyl compounds such asCO at low temperature. The theoretical study about the interaction between gold、silver and copper compounds with H2O/H2S、C2H2/C2H4molecule futher indicateshyperconjucation plays an important role in these kinds of interactions.We analyzed the topology properties of hydrogen/halogen and Cu/Ag/Au bonds byusing Bader’s “atoms in molecules”(AIM) theory. We have theoretically studied thenature of the Cu/Ag/Au bond using natural bond orbital (NBO) analysis. All thecomplexes were fully optimized and characterized with the Gaussian09programpackage at second-order M ller-Plesset (MP2) level of theory, and the aug-cc-pVTZbasis set was adopted for all the atoms. The main work and the conclusions are asfollows:Firstly, the theoretical study about several kinds of simple complexes H2O···AgCl/CuCl and H2S···AgCl/CuCl reported by Anthony C. Legon et al. was performed atthe MP2level. The distinguishing feature of Cu/Ag/Au bonds is their bonding interms of the hyperconjugation interaction, apart from the expected σ-donationinteraction. Although the Cu/Ag/Au-bonded complexes are structurally similar to thehydrogen-and halogen-bonded analogues, they offer quite a different pattern ofchanges such as stretching frequency shifts and binding energies. The calculatedbinding energy of the Cu/Ag/Au bond ranges from9.03to21.64kcal/mol, whereasthe binding energy ranges from0.745to3.398kcal/mol in their hydrogen and halogenbonds. Cu, Ag, and Au bonds are all partially covalent and partially electrostatic innature. Secondly, the theoretical study was further performed on the interaction betweenπ-moieties and CuCl/AgCl/AuCl such as C2H2···CuCl、C2H2···AgCl、C2H2···AuCl、C2H4···CuCl、C2H4···AgCl and C2H4···AuCl. Furthermore, the NBO analysis indicatesthat the large charge transfer (0.0380e-0.1752e) occurs mainly between donorπ-moieties and the empty ns (n=4,5, and6) orbital of the coinage metal atoms.The three kinds of delocalization interactions (π�'TM，π*←TM�'�π�'σ*) are thedistinguishing features of these complexes. The hyperconjugation effect can also notbe neglected in these complexes.Thirdly, we studied the effect of the cooperativity between Cu/Ag/Au bond andhydrogen bond. The cooperative energy (Ecoop) is the most effective method forevaluating the cooperativity. The negative Ecoop indicates a positive cooperativity inall the dimmers. The increase of the interaction energy for all types of interactions intrimer indicates that there is slight interplay between the two interactions in the trimer.Furthermore，the effect of Cu/Ag/Au bond on the hydrogen bond is a little larger thanthat of the hydrogen bond on the Cu/Ag/Au bond.The NBO analysis indicates the hyperconjugation effect plays an important roleboth in C2H2/C2H4···MCl and H2O/H2S···MCl(M=Cu, Ag, Au). As Igor V. Alabuginwrote in his latest review,“with the arrival of powerful computational techniqueswhich can assist future experimental studies in disentangling the relative importanceof hyperconjugation in comparison to other electronic and steric effects, the true roleof hyperconjugation will continue to reveal itself in many chemical phenomena.”There is interplay between the Cu/Ag/Au bond and the hydrogen bond in the trimer.