Premium
Die Koordinationszahl von Lanthaniden: Thermodynamik der Ln III EDTA‐Mischkomplexe mit den Anionen der 8‐Hydroxychinolin‐5‐sulfonsäure, Iminodiessigsäure und Nitrilotriessigsäure
Author(s) -
Geier G.,
Karlen U.
Publication year - 1971
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19710540113
Subject(s) - chemistry , lanthanide , nitrilotriacetic acid , coordination number , titration , iminodiacetic acid , chelation , equilibrium constant , inorganic chemistry , molecule , dota , stability constants of complexes , coordination complex , actinide , crystallography , ion , metal , aqueous solution , organic chemistry
The values of Δ G , Δ H and Δ S for the formation of the mixed 1:1:1 lanthanide EDTA complexes with the anions of 8‐hydroxyquinoline‐5‐sulfonic acid, iminodiacetic acid and nitrilotriacetic acid were determined by pH‐titrations and a direct calorimetric method. These thermodynamic data are discussed and compared with those for the formation of the Ln(III)EDTA complexes. Contrary to current opinion it is concluded that all trivalent lanthanide aquoions have the same coordination number in dilute solution. However, in the series of the lanthanide EDTA complexes the coordination number changes between Sm and Tb. In this region, equilibria occur between two types of EDTA complexes with different numbers of coordinated water molecules:The corresponding equilibrium constants could be evaluated. The coordination number changes also in many other Ln complexes along the lanthanide series, and similar equilibria occur.