Investigation of Noncovalent Interactions in Organofluorine Compounds with C-F bonds in different Electronic Environment

Abstract

We have synthesized a series of fluorine substituted 2-methylpropanamide compounds including a pair of polymorphs with the fluorine substitution at aromatic ring and methyl carbon to investigate the relevance of weak non-covalent interactions in the solid-state. The compounds are structurally characterized by single crystal X-ray diffraction technique and their supramolecular behaviour are explored methodically regarding the contribution of strong hydrogen bonds like N‒H•••O, acting in conjunction with C‒H•••O, and the ancillary support of weak C‒H•••F interaction. PIXEL calculations allowed for the estimation of the different intermolecular interaction energies of the derived dimers and the overall lattice energies of the different crystalline solids. It is observed that the molecular motifs consisting of C(sp2)‒H•••F‒C(sp2) interaction are more stable in comparison to other C‒H•••F interactions. QTAIM analysis further supports these interactions via a topological analysis of the electron density distribution at the bond critical point. A detailed experimental and computational evaluation have been carried out to evaluate the effect of the environment surrounding the carbon atom, i.e. the role of hybridization of the carbon atom, connected to the acceptor fluorine atom and the donor hydrogen atom as well.