Quantum Chemical Insights Into Noncovalent Interactions Between Aromatic Heterocycles and Formic Acid

Abstract

We employ various electronic structure methods to explore the noncovalent interactions in the formic acid (FA)–aromatic heterocycle (ZC₄H₄, where ZO, S and Se) dimers. The interaction energy (E_int) of these dimeric complexes is calculated within the supermolecular approach and the symmetry-adapted perturbation theory (SAPT). We also investigate the effects of electron correlation and basis set size on the computation of E_int. Our study reveals that furan (OC₄H₄) prefers to interact with formic acid via the nonbonding electron of the O atom, whereas thiophene (SC₄H₄) and selenophene (SeC₄H₄) do the same via π-electrons. Although there is an interplay of charge transfer from the nonbonding- and π-orbital of the aromatic heterocycle moieties to the antibonding orbital of the OH bond in the formic acid, the complexes are primarily stabilized by electrostatic and dispersion forces. The quantum theory of atoms in molecule (QTAIM) analysis further confirms that these complexes involve closed-shell interactions, particularly moderate-strength hydrogen bonding.