Stability Constants of the Inclusion Complexes of ß-Cyclodextrin with Various Adamantane Derivatives. A UV-Vis Study

Abstract

The stability constants for the inclusion complexes of ß-cyclodextrin (ß-CD) with various adamantane derivatives (ADA), namely the amantadinium (AM), rimantadinium (RIM), and memantinium (MEM) cations have been determined by UV-Vis spectrophotometry. All experiments have been performed at a pH of 1.7 and 25 º C on aqueous solutions adjusted to an ionic strength of 0.05 M (Na+, H+)ClO4. The competitive binding method has been used whereby methyl orange (MO) is first encapsulated by ß-CD and is then substituted by ADA. It has been shown that the derivatives studied form host-guest type complexes. The calculated stability constants, reported as log K1, were estimated to be 3.9 ± 0.1, 5.1 ± 0.2 and 3.3 ± 0.1, for AM, RIM and MEM, respectively. The factors that govern the strength of binding ADA with ß-CD have been discussed and an attempt was made to rationalise the variation in the established stability constants for the ADA-ß-CD complexes. General experimental conditions required for the determination of the stability constants of ADA with ß-CD with the use of MO as an auxiliary agent were evaluated. The optimised experimental conditions are recommended. It has been concluded that MO, even though commonly used in this type of study, does not meet the optimal and recommended conditions.


South African Journal of Chemistry Vol.54 2001: 84-101