Constructing, in silico, molecular self-aggregates and micro-hydrated complexes of oxirene and thiirene

Context: Oxirene, surmised to exist in the interstellar medium, was synthesized in the laboratory only recently. The present study investigates theoretically to what extent the two exotic molecules, oxirene and its thia-analogue thiirene, are capable of forming molecular self-aggregates and undergo micro-hydration under cooperative hydrogen bonding as the tour de force. Cogent molecular descriptors, such as binding energies for cluster formation, molecular electrostatic potential (MESP), effective atomic charges, infrared spectroscopic response, criticality profiles from the quantum theory of atoms in molecules (QTAIM), hydrogen bond energies, and reduced density gradient (RDG) maps identifying non-covalent interactions (NCI), all in unison confirm theoretically the existence and characterize the aggregates. In particular, infrared spectra display frequency down-shifts for the hydrogen bonded C-H vibrations in aggregates and for O-H in hydrated complexes. This work carried out in silico, should furnish credible tenets toward identification of oxirene and thiirene self-aggregates and their micro-hydrated complexes that potentially exist in the interstellar medium.

Method: By means of a molecular modeling program AVOGADRO, a multitude of initial-guess clusters under universal force field (UFF) were generated, which were subsequently optimized employing the GAUSSIAN16 suite of programs with the tightest convergence criterion, at the ωB97xD level of density functional theory embodying long-range dispersion effects, in conjunction with a reliable basis set 6-311 ++ G(2d,2p). The versatile package GAUSSVIEW yields the structures, vibrational frequencies, and criticality information, respectively.