Dissociation kinetics of 1,10-diaza-4,7,13,16-tetraoxacyclooctadecane-N,N'-diacetic acid complexes of lanthanides

Journal Article · Wed Jun 17 04:00:00 EDT 1987 · Inorg. Chem.; (United States)

DOI:https://doi.org/10.1021/ic00259a033· OSTI ID:6295259

Chang, C A; Sekhar, V C

The dissociation kinetics of 1,10-diaza-4,7,13,16-tetraoxacyclooctadecane-N,N'-diacetic acid (K22DA) complexes of lanthanide(III) ions were studied in perchloric acid and other media, over the concentration range 5 x 10 U to 7.5 x 10 T M and at a constant ionic strength of 0.1 M (LiClO4). Copper (II) was used as the scavenger of free ligand, and the rates of dissociation of these complexes have been found to be independent of (CuS ). All the complexes exhibit acid-dependent and acid-independent pathways in a manner similar to those of LnCyDTA complexes (CyDTA = trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetate ion). Unlike lanthanide (Ln) complexes of 1,7-diaza-4,10,13-trioxacyclopentadecane-N,N'-diacetic acid (K21DA), LnK22DA complex dissociation rates are independent of (anion) and (electrolyte). There is also no general-acid catalysis. The overall results are compared with those of complexes that are structural analogues such as LnK21Da , LnMEDTA (MEDTA = N-methyl-ethylenediamine-N,N,N'-triacetate ion), and LnCyDTA . A rationalization is given to account for similarities and differences with respect to observed kinetic characteristics. A number of postulates concerning the relationship between thermodynamic and kinetic stabilities and the detailed reaction mechanisms of lanthanide complxes of polyamino polyacetate ligands are proposed. 19 references, 1 figure, 7 tables.

• Research Organization: Univ. of Texas, El Paso
• DOE Contract Number: FG05-84ER13292
• OSTI ID: 6295259
• Journal Information: Inorg. Chem.; (United States), Journal Name: Inorg. Chem.; (United States) Vol. 26:12; ISSN INOCA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ACETIC ACID
CARBOXYLIC ACIDS
COMPLEXES
DATA
DISSOCIATION
EXPERIMENTAL DATA
INFORMATION
KINETICS
MONOCARBOXYLIC ACIDS
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
RARE EARTH COMPLEXES
REACTION KINETICS
THERMODYNAMICS