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 by means of molecular mechanics (MM2/QD) models. Electrostatic and van der Waals interactions and the formation of a hydrogen bond between the donor amino group and the oxygen atom of the secondary hydroxyl group seem to be the more important contributions in determining complex stability. (C) 2001 Elsevier Science Ltd. All rights reserved.