Abstract
We present the first high-level ab initio benchmark study of the interaction energy between fluorocyclohexanes and benzene. These compounds form CH···π interactions with aromatic solvents which causes notable shielding of the axial cyclohexane protons. For the recently synthesised all-cis 1,2,3,4,5,6-hexafluorocyclohexane the interaction energy with benzene amounts to -7.9 kcal mol(-1) and -6.4 kcal mol(-1) at the MP2 and SCS-MP2 levels, respectively (extrapolated to the complete basis set limit), which according to dispersion-corrected density functional calculations, is largely due to dispersion.
Highlights
We present the first high-level ab initio benchmark study of the interaction energy between fluorocyclohexanes and benzene
For the recently synthesised all-cis 1,2,3,4,5,6-hexafluorocyclohexane the interaction energy with benzene amounts to À7.9 kcal molÀ1 and À6.4 kcal molÀ1 at the MP2 and SCS-MP2 levels, respectively, which according to dispersion-corrected density functional calculations, is largely due to dispersion
NMR chemical shifts computed for the B3LYP-optimised complexes appeared to reproduce the upfield shifts observed in aromatic solvents better than those using the tighter geometries obtained with dispersion corrections
Summary
We present the first high-level ab initio benchmark study of the interaction energy between fluorocyclohexanes and benzene These compounds form CHÁ Á Áp interactions with aromatic solvents which causes notable shielding of the axial cyclohexane protons. For the recently synthesised all-cis 1,2,3,4,5,6-hexafluorocyclohexane the interaction energy with benzene amounts to À7.9 kcal molÀ1 and À6.4 kcal molÀ1 at the MP2 and SCS-MP2 levels, respectively (extrapolated to the complete basis set limit), which according to dispersion-corrected density functional calculations, is largely due to dispersion. The newly synthesised hexafluorocyclohexane 3 is an ideal target for this purpose, because its complex with the simplest aromatic, benzene, can have high symmetry (C3v, Fig. 3), all CHÁ Á Áp contacts being equivalent We present such a high-level ab initio benchmark for the CHÁ Á Áp binding energies between compound 3 and benzene at MP2 and SCS-MP2 levels, extrapolated to the complete basis set (CBS) limit. À1.7 ppm) to those observed in the all-cis tetrafluoro derivatives 1 and 2.3a
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