Do Deuteriums Form Stronger CH−π Interactions?

The D/H isotope effect for the CH−π interaction
was
studied experimentally and computationally. First, a series of molecular
balances that are very sensitive to changes in the strength of the
CH−π interactions in solution were designed. Balances
with deuterated and non-deuterated alkyl groups were synthesized,
and their intramolecular CH−π interactions were compared.
The geometries of their intramolecular CH−π and CD−π
interactions were characterized in the solid state by X-ray analysis,
and the strength of each interaction was characterized in solution
by the folded/unfolded ratio as measured by 1H NMR spectra.
Second, the relative strengths of the CH−π and CD−π
interactions were also assessed computationally using dispersion-corrected
DFT (PDE-D2/6-31+G*). No significant differencee was observed in either
the experimental or theoretical studies, indicating that the D/H isotope
effect for the CH−π interaction is either very small
or nonexistent.