pH dependence of relaxivities and hydration numbers of gadolinium(III) complexes of macrocyclic amino carboxylates
- Bristol-Myers Squibb Pharmaceutical Research Inst., New Brunswick, NJ (United States)
In the authors' previous paper, they reported the pH dependence of T[sub 1] relaxivities (R[sub 1], the second-order rate constant that describes the catalytsis of T[sub 1] relaxation by a paramagnetic species) for Gd(III) complexes, and hydration numbers (q, the number of inner-sphere coordinated water molecules) for analogous Tb(III) complexes of the linear amino carboxylic acid ligands: EDTA, HEDTA, EGTA, DTPA, and TTHA. A plot of R[sub 1] vs q values for all the complexes of the linear amino carboxylic acids in monomeric forms gave a straight line with an intercept of 2.2[plus minus]0.1 (mM s)[sup [minus]1] and a slope of 1.6[plus minus]0.1 (mM s)[sup [minus]1] per coordinated water. It was concluded that the intercept represents the outer-sphere relaxivity for these Gd(III) complexes, and the slope represents the estimated contribution of each inner-sphere water to R[sub 1]. To further examine the effect of charge and ligand structure on the relaxation behavior, they have determined the relaxivities and inner-sphere hydration numbers of Gd(III) and Tb(III) complexes of three macrocyclic amino carboxylic acids, i.e., DO3A, HP-DO3A, and DOTA as a function of solution pH. An energy-transfer quenching experiment using Eu(III) and Tb(III) complexes was carried out to detect any marked tendency to form oligomers in these macrocyclic complex solutions. 24 refs., 4 figs., 1 tab.
- OSTI ID:
- 7070105
- Journal Information:
- Inorganic Chemistry; (United States), Vol. 31:26; ISSN 0020-1669
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
GADOLINIUM COMPLEXES
HYDRATION
SPIN-LATTICE RELAXATION
AMINES
CARBOXYLIC ACIDS
EUROPIUM COMPLEXES
LIGANDS
LUMINESCENCE
PH VALUE
TERBIUM COMPLEXES
COMPLEXES
ORGANIC ACIDS
ORGANIC COMPOUNDS
RARE EARTH COMPLEXES
RELAXATION
SOLVATION
400201* - Chemical & Physicochemical Properties