APPROACHES TO IMPROVEMENT OF METAL-ION SELECTIVITY BY CRYPTANDS

Citation
Xx. Zhang et al., APPROACHES TO IMPROVEMENT OF METAL-ION SELECTIVITY BY CRYPTANDS, Coordination chemistry reviews, 174, 1998, pp. 179-189
Citations number
39
Language
INGLESE
art.tipo
Review
Categorie Soggetti
Chemistry Inorganic & Nuclear
ISSN journal
0010-8545
Volume
174
Year of publication
1998
Pages
179 - 189
Database
ISI
SICI code
0010-8545(1998)174:<179:ATIOMS>2.0.ZU;2-G
Abstract
Several approaches to improvement of metal ion selectivity by mixed ox ygen-nitrogen donor cryptands are discussed. Because of the relatively rigid structures of cryptands, thermodynamic stabilities of the crypt ate complexes strongly depend on the match of the cation size and cryp tand cavity diameters. Symmetry is an important factor influencing the properties of cryptand complexation. One rule to improve metal ion se lectivity by oxygen-nitrogen donor cryptands is to obtain the ligand t hat has the best size-match cavity with the cation while keeping a sym metric spherical-coordination array. High selectivity for a small cati on can be obtained when the cryptand is able to form a number of six-m embered chelate rings with the metal ion while the requirements of the high-symmetric donor atom array and size-matched cavity are met. On t he other hand, introduction of benzene rings and other groups to crypt ands usually decreases metal ion binding and selectivity. (C) 1998 Els evier Science S.A. All rights reserved.