A comparative interplay between small heterorings and hypofluorous acids.

Through the B3LYP/6-311++G(d,p) calculations, theoretical studies of structural parameters, electronic properties, infrared vibration modes, and charge density topologies on the C2H4O∙∙∙HX and C2H5N∙∙∙HX (X = F or O-F) heterocylic hydrogen complexes are presented. The H-bond distances and high energies point out strong contacts and stable interactions in these complexes, and the relationships between the frequency shifts on the H-F and H-O bonds as well as O-F σ-holes with the interaction strength are the benchmarks of this current work. The computations of charge transfer amounts in light of the ChelpG and NBO approaches revealed a separation of charge density on the O-F σ-holes, whose statement is reinforced by the QTAIM descriptors. Despite that O∙∙∙H and N∙∙∙H H-bonds have been characterized as closed-shell interactions, qualitatively the appearance of a partial covalent profile also was unveiled by the QTAIM protocol.