A theoretical investigation on Cu/Ag/Au bonding in XH2P center dot center dot center dot MY(X = H, CH3, F, CN, NO2; M = Cu, Ag, Au; Y = F, Cl, Br, I) complexes

摘要

Intermolecular interaction of XH2P center dot center dot center dot MY (X = H, CH3, F, CN, NO2; M = Cu, Ag, Au; Y = F, Cl, Br, I) complexes was investigated by means of an ab initio method. The molecular interaction energies are in the order Ag Cu Au and increased with the decrease of R-P center dot center dot center dot M. Interaction energies are strengthened when electron-donating substituents X connected to XH2P, while electron-withdrawing substituents produce the opposite effect. The strongest P center dot center dot center dot M bond was found in CH3H2P center dot center dot center dot AuF with -70.95 kcal/mol, while the weakest one was found in NO2H2P center dot center dot center dot AgI with -20.45 kcal/mol. The three-center/four-electron (3c/4e) resonance-type of P:-M-: Y hyperbond was recognized by the natural resonance theory and the natural bond orbital analysis. The competition of P: M-Y - P-M: Y resonance structures mainly arises from hyperconjugation interactions; the bond order of b(P-M) and b(M-Y) is in line with the conservation of the idealized relationship b(P-M) + b(M-Y) approximate to 1. In all MF-containing complexes, P-M: F resonance accounted for a larger proportion which leads to the covalent characters for partial ionicity of MF. The interaction energies of these Cu/Ag/Au complexes are basically above the characteristic values of the halogen-bond complexes and close to the observed strong hydrogen bonds in ionic hydrogen-bonded species. Published by AIP Publishing.