Synthesis and Molecular Recognition of Novel Oligo(ethylenediamino) Bridged Bis(-cyclodextrin)s and Their Copper(II) Complexes: Enhanced Molecular Binding Ability and Selectivity by Multiple Recognition

Abstract

Four bridged bis(b-cyclodextrin)s tethered by different lengths of oligo(ethylenediamine)s have been synthesized and their inclusion complexation behavior with selected substrates elucidated by circular dichroism spectroscopy and fluorescence decay. In order to study their binding ability quantitatively, inclusion complexation stability constants with four dye guests, that is, brilliant green (BG), methyl orange (MO), ammonium 8-anilino-1naphthalenesulfonic acid (ANS), and sodium 6-(p-toluidino)-2-naphthalenesulfonate (TNS), have been determined in aqueous solution at 25 8C with spectrophotometric, spectropolarimetric, or spectrofluorometric titrations. The results obtained indicate that the two tethered cyclodextrin units might cooperatively bind to a guest, and the molecular binding ability toward model substrates, especially linear guests such as TNS and MO, could be extended. The tether length plays a crucial role in the molecular recognition, the binding constants for ANS and TNS decrease linearly with an increase in the tether length of dimeric cyclodextrin. The Gibbs free energy changes (À DG o ) for the unit increment per ethylene are 0.99 kJ mol À1 for ANS and 0.44 kJ mol À1 for TNS, respectively. On the other hand, the presence of a copper(ii) ion in metallobis(b-cyclodextrin)s oligo(ethylenediamino) tethers enhances not only the original binding ability, but also the molecular selectivity through triple or multiple recognition, as compared with the parent bis(b-cyclodextrin)s.

Suppression effect of guanidine hydrochloride on α-cyclodextrin-assisted refolding of denatured α-amylase

“…Therefore, significant increase in the fluorescence intensity of ANS at high a-CD concentrations cannot be attributed to a simple stoichiometric interaction between a-CD and ANS. Such an increase in the emission intensities is generally believed to be due to decrease in the internal relaxation of the fluorophore (ANS) in a spatially restricted environment [21,22]. Control ANS fluorescence experiments in maltose solution (0-0.6 M) showed that ANS emission increased steadily, but not sharply, following the increase in the maltose concentration (Fig.…”

“Three-in-one” Complexes Formed by Anionic Guests and Monosubstituted Cationic Alkyldiamino β-Cyclodextrin Derivatives

“…They also observed a larger enhancement in the stability of the complexes in the presence of Cu(II). They finally concluded that this cyclodextrin dimer acts as a ternary recognition host, in which two hydrophobic and one electrostatic/ coordination sites are responsible for the stability of the supramolecular structure obtained [26,27].…”

Synthesis of ethylamine-bridged β-cyclodextrins and adsorption properties of thorium

“…Hence, numerous bridged cyclodextrins with different structural materials have been synthesized, and applied to a variety of areas of science and technology such as molecular receptors [14,15], electrochemical sensors [16], drug carriers [17] and monomer of polymer [18] in the last years. But the study of bridged b-cyclodextrins applied for recovery of thorium in waste warter has not been extensively investigated.…”