Chiral discrimination is the ability of a chiral molecule to exhibit different weak intermolecular interactions than its mirror image, and in this study it is investigated for dimers of oxiranemethanol (glycidol). For this purpose, high-level ab initio calculations were performed to explore the chiral self-recognition effects in the homo and heterochiral dimers of glycidol. Fourteen dimer structures were studied including, seven homochiral and seven heterochiral complexes. They all possess two intermolecular O−H...O hydrogen bonds. These structures were determined with the second-order Møller−Plesset perturbation theory (MP2) using the aug-cc-pVTZ basis set and then verified to pertain to actual local minima. The interaction energies for the 14 structures were computed at various levels of electronic structure theory and basis set up to the complete basis set (CBS) limit of the coupled-cluster approach with single, double, and perturbative triple excitations (CCSD(T)). Among all 14 structures, a homochiral one, possessing two hydrogen bonds forming a part of a ring with eight heavy atoms, is the global minimum. A similar heterochiral structure has the next strongest binding energy, about 0.6 kcal/mol smaller than the global minimum structure. Further insight into the origins of chiral self-recognition effects was provided by symmetry-adapted perturbation theory (SAPT) and a functional-group SAPT (F-SAPT) difference analysis to investigate the direct and indirect effects of two −H/−CH2OH substitutions leading from an achiral ethylene oxide dimer to the chiral glycidol dimer. Furthermore, harmonic frequency shifts relative to a non-interacting glycidol molecule were studied and analyzed for all conformations to acquire insight into the origins of chiral discrimination. It is shown that the largest frequency shifts come from the effect of hydrogen bonding on the O−H stretch mode, the stability of the ring involving both hydrogen bonds, and the transition between two non-equivalent minima of the glycidol molecule.

Chiral self-recognition: Interactions in the glycidol dimer

ACS Spring Meeting 2021

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