Spectrophotometric Study of Selective Binding Behaviors of Dye Molecules by Pyridine-and Bipyridine-Modified beta-Cyclodextrin Derivatives with a Functional Tether in Aqueous Solution

摘要

Four beta-cyclodextrin (beta-CD) derivatives bearing pyridine or bipyridine linkers,i.e.,mono[6-(3-pyridinecar-boxamide)ethyleneamino-6-deoxy]-beta-CD (2),mono[6-(4-pyridinecarboxamide)ethyleneamino-6-deoxy]-beta-CD (3),W,W-bis(2-aminoethyl)-2,2'-bipyridine-4,4'-dicarboxamide-bridged bis(6-amino-6-deoxy-beta-CD) (4),N,N'-bis(2-aminoethyl)-2,2'-bipyridine-3,3'-dicarboxamide-bridged bis(6-amino-6-deoxy-beta-CD) (5),and their copper-(II) complexes (6 and 7) were selected as molecular receptors to explore the conformation-function relationship of oligo(beta-CD)s.The original conformations of hosts 4-7 and their inclusion complexation behaviors with some guest molecules,i.e.,ammonium 8-anilino-l-naphthalenesulfonate (ANS),sodium 6-(be-toludino)-2-naphthalenesulfonate (TNS),and rhodamine B (RhB),were comprehensively investigated by means of UV- vis,2D NMR,and fluorescence spectroscopy.The results indicated that these oligo(beta-CD)s,especially bis(beta-CD) 5 and its copper(II) complex 7,exhibited the significantly enhanced binding abilities toward guest molecules as compared with native beta-CD.Typically,hosts 5 and 7 efficiently enhanced the original binding ability of native beta-CD toward ANS by a factor of 38-42 times.These increased binding abilities of oligomeric hosts were discussed from the viewpoint of the size/shape-fit and multipoint recognition between host and guest.