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 β-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 β-cyclodextrin. TD-DFT calculations showed that the observed ICD is caused by orbital mixing on trans-resveratrol upon complexation with β-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.