A β-cyclodextrin-resveratrol inclusion complex and the role of geometrical and electronic effects on its electronic induced circular dichroism

Complexation of trans-resveratrol with beta-cyclodextrin results in an induced Cotton effect (ICD). On the basis of NMR T-ROESY experiments and molecular dynamics simulations a preferential orientation mode of resveratrol within the cyclodextrin is proposed, in which the dihydroxyl ring is oriented towards the narrow side of the beta-cyclodextrin. TD-DFT calculations showed that the observed ICD is caused by orbital mixing on trans-resveratrol upon complexation with beta-cyclodextrin, being geometry effects averaged out by the flexibility of resveratrol inside the CD cavity. Computations also show that Harata-Kodaka rules are not of direct applicability to systems like resveratrol where the chromophore is only partially buried into the cyclodextrin cavity.