Project Details:

Critical evaluation of stability constants and thermodynamic functions of metal complexes of crown ethers

Project No.:	2001-040-1-500
Start date:	1997-01-01
End date:	2003-02-27
Division:	Analytical Chemistry Division

Objective:

(previously 560/40/97)

Critical review of thermodynamic data concerning the complexation of main group cations by crown ethers in various solvents

Description:

Macrocyclic compounds are synthetic or natural polydentate ligands containing donor atoms that are incorporated in a cyclic backbone or/and in substituents attached to it. They contain at least three donor atoms, and the ring should have a minimum of nine atoms. There is strong need for a critical review of stability constants and thermodynamic functions of macrocyclic metal complexes. Currently, only data compilations have been published, and divergent data have not yet been reconciled. In view of the very large body of previous data, critical evaluations have to be restricted to systems for which more data are available. Among the macrocyclic compounds we have selected the most studied crown ethers (with only oxygen as donor atoms): 1,4,7,10-tetraoxacyclododecane (12C4), 1,4,7,10,13-pentaoxacyclopentadecane (15C5) and 1,4,7,10,13,16-hexaoxacyclooctadecane (18C6). The metal ions chosen are: alkali and alkaline earth metal ions and Ag^+-, Tl^+-, Zn^2+- and Cd^2+-. The solvents studied are: water, methanol, ethanol, and their mixtures, as well as acetonitrile, dimethylformamide, dimethylsulphoxide and propylene carbonate.