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Indium(III) and Gallium(III) Complexes of Bis(aminoethanethiol) Ligands with Different Denticities: Stabilities, Molecular Modeling, and in Vivo Behavior
 

Summary: Indium(III) and Gallium(III) Complexes of Bis(aminoethanethiol) Ligands with
Different Denticities: Stabilities, Molecular Modeling, and in Vivo Behavior
Yizhen Sun, Carolyn J. Anderson,*, Tammy S. Pajeau, David E. Reichert, Robert D. Hancock,,
Ramunas J. Motekaitis, Arthur E. Martell, and Michael J. Welch
Department of Chemistry, Texas A&M University, College Station, Texas 77843-3255, and The Edward Mallinckrodt Institute
of Radiology, Washington University School of Medicine, St. Louis, Missouri 63110
Received August 10, 1995X
Complexes of Ga(III) and In(III) radionuclides are widely used in diagnostic imaging. In this
study, the following ligands of denticities 4, 5, and 6 respectively were prepared: N,N-bis-
(2,2-dimethyl-2-mercaptoethyl)ethylenediamine (4SS), 1-carboxy-N,N-bis(2,2-dimethyl-2-mer-
captoethyl)ethylenediamine (5SS), and N,N-bis(2,2-dimethyl-2-mercaptoethyl)ethylenediamine-
N,N-diacetic acid (6SS). Syntheses of the two new ligands, 5SS and 6SS, are described.
Equilibrium constants for their In(III) and Ga(III) complexes were determined by both direct
and ligand-competitive potentiometric methods. The formation constant (KML ) [ML]/[M][L])
of In(III)-6SS in 0.100 M KNO3 at 25.0 C is 1039.8, and its pM at physiological pH (7.4 with
100% excess of the ligand) is 30.9. These values are higher than those of any other previous
reported ligand for In(III). The stability constants of the complexes of 4SS, 5SS, 6SS, and the
analogous ligand EDDASS, N,N-bis(2-mercaptoethyl)ethylenediamine-N,N-diacetic acid, which
does not contain gem-dimethyl groups, are compared. The thermodynamic stabilities of the
In(III) complexes of all ligands except 6SS are greater than those of the corresponding Ga(III)

  

Source: Anderson, Carolyn J. - Department of Molecular Biology and Pharmacology, Washington University in St. Louis

 

Collections: Biology and Medicine