Probing Au•••O and Au•••P regium bonding interaction in AuX (X = F, Cl, Br)•••RPHOH (R = CH3, F, CF3, NH2, CN) complexes

CCSD(T) and MP2/aug-cc-pVTZ (PP) calculations have been carried out to investigate interaction energies and binding properties on the regium bonding intermolecular interaction between AuX (X = F, Cl, Br) and RPHOH (R=CH3, F, CF3, NH2, CN). For the AuX.RPHOH complexes, four types of configurations (trans-P, trans-O, cis-P and cis-O) are observed. The magnitude of molecular interaction energies is in the order of NH2 > CH3 > F > CF3 > CN, F > Cl > Br with the nature of the substituent directly affecting the strength of the interaction. The transition structures which present the energy barriers to the inter-conversion between the trans-type and the cis-type structures and the Boltzmann distribution to quantitatively determine the proportion of the cis-type and the trans-type geometries have been obtained. The natural resonance theory confirms the presence of the Au center dot center dot center dot O and the Au center dot center dot center dot P regium bonds with two major secondary resonance structures X-Au:RPHOH (omega I) <-> X:Au-RPHOH (omega II). In addition, LMO-EDA energy decomposition analysis is performed on the regium bonded complexes to predict the dominant energy component and the nature of the Au center dot center dot center dot O and the Au center dot center dot center dot P regium bonded interaction.