Structure, binding energy and chiral discrimination in oxathiirane homodimers
Oxathiirane (XHCSO) homodimers bonded by hydrogen bonds (HB) and chalcogen bonds (YB) were studied at the Møller-Plesset (MP2) computational level. Binding energies obtained at the Coupled-Cluster level up to the Complete Basis Set limit [CCSD(T)/CBS] indicate that HB complexes present stronger binding modes than the YB complexes. In terms of chiral discrimination energy, R,S complexes are favored over R,Rcomplexes with the exceptions of SiCl3 and SiF3 derivatives. Natural Bond Orbital (NBO) results are in agreement with the interaction energies in the case of the HB complexes, but could not discriminate between R,R and R,S in the YB complexes. The lack of correlation between molecular electrostatic values on the 0.001 a.u. and binding energies, in addition to the discrepancies between Atoms in Molecules (AIM) and NBO results may suggest that the electrostatics is not the dominant term in the interaction energy. This was corroborated by the Localized Molecular Orbital Energy Decomposition Analysis (LMOEDA) calculations which showed that the exchange and dispersion terms are the most important attractive components for all the complexes studied, contributing up to 50.6% and 42.5% to the total attractive forces respectively.