Critical evaluation of stability constants and thermodynamic functions
of metal complexes of crown ethers (IUPAC Technical Report)
F. Arnaud-Neu, R.
Delgado*, and S. Chaves
Abstract: Stability constants and thermodynamic functions of
metal complexes of crown ethers in various solvents published between
1971 and the beginning of 2000 have been critically evaluated. The most
studied crown ethers have been selected: 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, Ag+, Tl+, Cd2+,
and Pb2+. The solvents considered are: water, methanol, ethanol,
and their mixtures, as well as acetonitrile, N,N'-dimethylformamide,
dimethylsulfoxide, and propylene carbonate. The published data have
been examined and grouped into two categories, accepted
and rejected. The accepted values were considered
as: (i) recommended (R), when the standard deviations (s.d.)
on the constant K or on DrH
were inferior to 0.05 lg unit or inferior to 1 kJ mol1,
respectively; (ii) provisional (P), when s.d. is superior to
0.05 and inferior to 0.2 for lg K or s.d. is superior to 1 and
inferior to 2 kJ mol1 for DrH;
(iii) recommended 1 (R1), if the values were obtained by a single
research group, but were considered reliable in comparison with related
systems, and considering that the research team usually presents R-level
values for other similar systems.
* Corresponding author
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