Helicity discrimination in diselenides by chiral substituents-a circular dichroism study

Diselenides substituted with chiral alkyl groups exhibit, in solution and in the crystal form, Cotton effects within the diselenide chromophore absorption region. The origin is traced to steric effects, leading to a non-uniform distribution of diastereomeric P and M forms of the diselenide chromophore. A DFT computational model presented herein allows us to predict the preferred helicity of the diselenide chromophore from the sign of the experimental n-σ∗ Cotton effect, that is, a positive long-wavelength Cotton effect is due to a P conformer and a negative Cotton effect corresponds to an M conformer.