Density functional study of interactions between fluorinated cyclohexanes and arenes

Abstract

1H-NMR Chemical shifts of all-syn-1,2,4,5-tetrafluorocyclohexane (1), all-syn-1,2,3,4-tetrafluorocyclohexane (2), and their complexes with benzene are calculated at the BHandH/6-311+G(2d,p) level. The observed shielding of certain resonances on going from CD2Cl2 to (D8)toluene solution is qualitatively reproduced in these model calculations, in particular when standard B3LYP/def2-TZVP optimised geometries are employed. The results are interpreted with the quantum theory of atoms in molecules (QTAIM) and non-covalent interactions (NCI) methods, and they indicate that aromatic molecules bind strongly (1.6 kcal mol−1) to the ‘positive face’ of these molecules. The level of theory is validated for the new compound all-syn-1,2,4,5-tetrafluoro-3-phenylcyclohexane (3), where a recently developed QM/MM protocol for optimisation of molecular crystals afforded excellent agreement between the B3LYP/def2-TZVP structure and that observed in the solid.