Spectrophotometric determinations of binding constants between cyclodextrins and aromatic nitrogen substrates at various pH values

The inclusion capacity of native beta -cyclodextrin (1) and mono-(6-amino-6 -deoxy)-beta -cyclodextrin (2) versus aromatic compounds having a nitro or an amino group or both has been investigated at three different pH values. Molecular interactions in inclusion complexes have also been investigated b y means of molecular mechanics (MM2/QD) models. Electrostatic and van der W aals interactions and the formation of a hydrogen bond between the donor am ino group and the oxygen atom of the secondary hydroxyl group seem to be th e more important contributions in determining complex stability. (C) 2001 E lsevier Science Ltd. All rights reserved.