Chiral Discrimination of camphorquinone Enantiomers by Cyclodextrins: A Spectroscopic and Photophysical Study

The complexation of (1R)-(-)-camphorquinone and (1S)-(+)-camphorquinone with a-, b- and g-cyclodextrins (CD) is elucidated by a combination of spectroscopic techniques and theoretical methods applying a Dynamic Monte Carlo procedure. The absorption, induced circular dichroism (icd), luminescence and transient triplet-triplet absorption properties of the two enantiomers are modified by the CDs in agreement with the formation of 2:1 host:guest complexes with a-CD and 1:1 complexes with b- and g-CD. The equilibrium constants and, in part, the triplet lifetimes indicate a distinct chiral discrimination of cyclodextrins towards the two camphorquinone enantiomers. These results were in addition supported by conformational calculations and theoretical interpretation of icd spectra, which also provided detailed structural data on the complexes.