[Complexation properties of the ligand EOB-DTPA and the kinetic stability of Gd(EOB-DTPA)].
Due to the presence of the ethoxy-benzyl group, the lipophilicity of the complex Gd(EOB-DTPA)2- is higher than that of Gd(DTPA)2- and thus Gd(EOB-DTPA)2- can be used as a liver specific contrast agent in Magnetic Resonance Imaging. The stability constants of the complexes of Fe2+, Fe3+, Zn2+ and Cu2+ formed with EOB-DTPA practically agree with those of the respective DTPA complexes. The complexes of EOB-DTPA formed with larger metal ions, like Ca2+, Ba2+, Gd3+ and other lanthanides, exhibit larger stability constants than the complexes of DTPA by 0.5-1 logK unit. The stability constants of the complexes Ln(EOB-DTPA)2- increase with increasing atomic number till the middle of the series. For the elements Tb to Ho the logKLnL values are approximately equal and a weak decrease can be observed for the heaviest elements, probably because of steric hindrance between the functional groups. The exchange reactions between the complex Gd(EOB-DTPA)2- and Y3+ ions occur predominantly through the formation and rate determining dissociation of the mono- and diprotonated complexes. The rate constants characterizing these reaction pathways are lower by a factor of three than the respective rate constants, known for the dissociation of Gd(DTPA)2-. On the basis of its higher kinetic stability, Gd(EOB-DTPA)2- can be used for in vivo investigations in medical diagnosis.
Burai
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L
Debreceni Egyetem, Szervetlen és Analitikai Kémiai Tanszék, 4010 Debrecen.
Brücher
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E
Király
R
R
Solymosi
P
P
Víg
T
T
D003287:Contrast Media / Q000737:chemistry*; D003300:Copper; D004355:Drug Stability; D019786:Gadolinium DTPA / Q000737:chemistry*; D007501:Iron; D007700:Kinetics; D008024:Ligands; D004369:Pentetic Acid / Q000737:chemistry; D013329:Structure-Activity Relationship; D015032:Zinc
D003287:Contrast Media; D008024:Ligands; C073590:gadolinium ethoxybenzyl DTPA; D003300:Copper; D004369:Pentetic Acid; D007501:Iron; D015032:Zinc; D019786:Gadolinium DTPA