Binding and catalysis with a metal-induced ternary complex of an ethylenediamine-substituted cyclodextrin
- 1 January 1992
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 3,p. 387-391
- https://doi.org/10.1039/p29920000387
Abstract
The binary complex (CDen2Cu) from 6-(2-aminoethyl)amino-6-deoxy-β-cyclodextrin (CDen) and Cu2+ binds methyl orange (MO) about twice as efficiently as CDen alone, whereas brilliant yellow (BY), owing to the extended shape of this substrate, shows an approximately sevenfold increase in K. Deacylation of p-nitrophenyl benzoate (PNPB) shows, with an ethylenediamine model compound, the expected rate enhancement, which is retarded upon addition of sufficient Cu2+ to block the N lone pairs. In sharp contrast, deacylation of PNPB is accelerated by CDen2Cu, whereas the ‘shorter’p-nitrophenyl acetate (PNPA), being less suited to formation of a ternary inclusion complex, again exhibits a rate decrease. Catalytic rate constants kc and Michaelis–Menten constants KD are obtained from Lineweaver–Burk or Eadie plots; equilibrium constants for MO and BY have been studied at different wavelengths. The problems associated with the evaluation of the multiple variables in such equilibria are illustrated.Keywords
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