THERMODYNAMIC STUDY OF COMPLEXATION OF ALKALI AND ALKALINE-EARTH METAL-IONS WITH BENZENE-CONTAINING CRYPTANDS

Citation
Xx. Zhang et al., THERMODYNAMIC STUDY OF COMPLEXATION OF ALKALI AND ALKALINE-EARTH METAL-IONS WITH BENZENE-CONTAINING CRYPTANDS, Inorganica Chimica Acta, 278(1), 1998, pp. 6-9
Citations number
17
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Chemistry Inorganic & Nuclear
Journal title
ISSN journal
0020-1693
Volume
278
Issue
1
Year of publication
1998
Pages
6 - 9
Database
ISI
SICI code
0020-1693(1998)278:1<6:TSOCOA>2.0.ZU;2-8
Abstract
Log K, Delta H, and Delta S values for interactions of four benzene-co ntaining cryptands (1-4) with alkali metal ions, Sr2+, and Ba2+ were d etermined at 25 degrees C by calorimetric titration in absolute methan ol. The cryptands form stable complexes with the metal ions (except Li +). Log K values range from 2.90 (2-Cs+ interaction) to 5.10 (4-K+ int eraction). Very low reaction heats for Li+ complexation with 1-4 indic ate that the cavity sizes of these cryptands are too large to match th e small Li+. Different structures of the benzo bridges of the cryptand s have an effect on cation complexation. All cryptands studied selecti vely bind K+ over the other cations. Cryptand 4 selects K+ over Ba2+ b y a factor of 10, which is a reversal of the common Ba2+ over K+ selec tivity order demonstrated by most [2,2.2]-type cryptands. Cryptands 1 and 2 show more negative (favorable) Delta H values and more negative or less positive (unfavorable) Delta S values for the interactions wit h the metal ions (except Li+ and 2-Cs+) than cryptands 3 and 4. (C) 19 98 Elsevier Science S.A. All rights reserved.