ISSN:
1573-1111
Schlagwort(e):
Dicarboylated calix[4]arenes
;
sodium and potassium complexes
;
solvent extraction
;
selectivity
;
1H-NMR mononuclear and dinuclear species
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Chemie und Pharmazie
Notizen:
Abstract The extraction of sodium and potassium ions by 25,27-dicarboxymethyl-26,28-dimethoxy-5,11,17,23-tetra-tert-butyl calix[4]arene (L1H2) in chloroform shows the formation of MLIH and M2LI complexes (M = Na, K). In 1,2-dichloroethane, the MLIH species are formed in the acidic pH range, while only the Na2LI species is found at high pH values. The corresponding extraction equilibrium constants K11 (M) and K21 (M) have been evaluated and show a selectivity in favour of Na+ as compared to K+, whatever the nature of the complexes. In chloroform, this selectivity is much more pronounced considering the 2 : 1 complexes: K11(Na)/K11(K)≪ K21(Na)/K21(K). The coexistence of 1 : 1 and 2 : 1 metal : ligand complexes is also shown in the extraction of sodium in 1,2-dichloroethane by the 25,27-dicarboxymethyl-26,28-dimethoxyethoxy-5,11,17,23-tetra-tertbutyl calix[4]arene (LIIH2), locked in the cone conformation. Structural data of the complexes are discussed on the basis of 1H-NMR spectra. In particular, for LIH2, a conformational change from cone to partial cone upon metal complexation has been evidenced for the complexes KLIH, K2LI and Na2LI.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1023/A:1007993200050
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