Role of entropy in supramolecular photochirogenesis: enantiodifferentiating photoisomerization of cyclooctenes in chiral sensitizer-immobilized MCM-41 cavities.

To examine the effects of confinement, or low-entropy environments, we employed the mesoporous silicate MCM-41 modified with optically active benzenetetracarboxylates as chiral reaction media to effect the enantiodifferentiating photoisomerization of (Z)-cyclooctene and (Z,Z)-1,5-cyclooctadiene. The ee of the (E)-isomer produced and its temperature dependence behavior in MCM-41 were completely different from those observed in homogeneous solutions. Immobilizing the sensitizer in MCM-41 reduced the contribution of the entropy factor.