Number: 2001-040-1-500 (previously 560/40/97)
Title: Critical evaluation of stability constants and thermodynamic
functions of metal complexes of crown ethers
Task Group
Chairmen: F. Arnaud-Neu
and R. Delgado
Member: S. Chaves
Completion Date: 2002 - project completed
Objective:
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+, Zn2+ and Cd2+. The solvents studied
are: water, methanol, ethanol, and their mixtures, as well as acetonitrile,
dimethylformamide, dimethylsulphoxide and propylene carbonate.
Progress:
The first draft of the report was completed in March 2001. Revision
will be included starting Sep 2001.
Project completed - IUPAC Technical Report published in Pure
Appl. Chem.
75(1), 71-102, 2003.
Last update: 27 February 2003