Through space JFH spin-spin coupling constant transmission pathways in 2-(trifluoromethyl)thiophenol: formation of unusual stabilizing bifurcated CFHS and CFSH interactions

Phys Chem Chem Phys. 2021 Apr 22;23(15):9080-9088. doi: 10.1039/d0cp05887d.

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 CFHS H-bond in the cis conformer of 2-trifluoromethylthiophenol and an unusual, bifurcated CFSH interaction in the trans conformer. The JFH 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 JFH 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 σSH bonding orbital.