A spectrofluorimetric study of binary fluorophore–cyclodextrin complexes used as chiral selectors

Abstract

Abstract-Six binary complexes between three fluorophores (pyrene, xanthone and anthraquinone) and b-cyclodextrin (b-CD) or heptakis-(6-amino)-(6-deoxy)-b-cyclodextrin (am-b-CD) were tested at two pH values (8.0 and 9.0) as chiral selectors for three a-amino acids chosen as model. The conditional constant (b 2T ) values for ternary complexes (fluorophore-CD-amino acid), determined by means of fluorescence spectroscopy, showed that the binary complexes are suitable receptors for chiral recognition. The effect of a-amino acids on stability and stoichiometric ratio of the binary complexes has also been studied. The binary complexes were in most cases stabilized by adding the ternary agent. The trend of stoichiometric ratios found is supported by variations in fluorescence spectra. Those relative to pyrene (Py) show little changes going from binary to ternary complexes, while those recorded in the presence of xanthone (Xan) give the most significant variations underlining a deep reorganization of guest. Anthraquinone (Aq) shows an intermediate behavior.

Self-Assembled Vesicles Prepared from Amphiphilic Cyclodextrins as Drug Carriers

“…As a result, the natural properties of the cyclodextrin amphiphile were greatly affected and vesicles will not be able to form. Since it was reported that anthraquinone can form inclusion complex with β-cyclodextrin, − the possible intermolecule inclusion model cannot be ignored.…”

Chiral recognition of protected amino acids by means of fluorescent binary complex pyrene/heptakis-(6-amino)-(6-deoxy)-β-cyclodextrin

“…So the complex stability can be altered by adding a ternary agent. 11,12 As previously reported, 12 a stoichiometric ratio (1/2/2) (fluorophore-cyclodextrin-ternary agent) for ternary complexes studied was determined by means of Job plot analysis. 16 The b 2 value for the ternary complex can be either higher or lower than that for the binary complex.…”

“…Recently, we have reported results about the chiral discrimination ability of the binary complexes formed by Py, xanthone and anthraquinone in the presence of both b-cyclodextrin and am-b-CD versus enantiomers of phenylalanine, methionine and histidine. 12 Collected data have shown that the chiral discrimination ability is influenced by the structure of the fluorescent guest and the binary complex symmetry. In this light, both in the presence of the b-CD and am-b-CD, the binary complex formed by Py was the best chiral selector.…”