Through space JFH spin–spin coupling constant transmission pathways in 2-(trifluoromethyl)thiophenol: formation of unusual stabilizing bifurcated CF⋯HS and CF⋯SH interactions

Abstract

Given its importance and the possibility of organic F to participate in hydrogen bonds (H-bonds), the understanding of its behavior as a H-bond acceptor with different donors is crucial. The interest in organofluorine compounds and the works related to the study of the participation of this atom in non-covalent interactions is constantly growing. Following recent studies in this subject, we evaluated the existence of two bifurcated intramolecular interactions, a bifurcated CF⋯HS H-bond in the cis conformer of 2-trifluoromethylthiophenol and an unusual, bifurcated CF⋯SH interaction in the trans conformer. The J_FH spin–spin coupling constant (SSCC) was evaluated for 2-trifluoromethylthiophenol both experimentally by ¹H and ¹⁹F NMR and theoretically using the natural bond orbitals (NBO), the quantum theory of atoms in molecules (QTAIM) and the non-covalent interactions (NCI) framework. Although both interactions are crucial for the stabilization of the conformer geometries, the observed positive J_FH spin–spin coupling constant (SSCC) is mainly resultant from the trans conformer, which has a large calculated positive SSCC, and is transmitted through steric interactions involving the F lone pairs and the σ_SH bonding orbital.