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Livramento, JB ; Sour, A ; Borel, A ; Merbach, AE ; Tóth, E

Six Gd3+ ions densely packed in a starburst-shaped heterometallic compound

Chemistry-A European Journal 12 (4) 989-1003

par Administrateur - publié le

Abstract :

The heterotritopic ligand [bpy(DTTA)(2)](8-) has two diethylenediamine e-tetra acetate units for selective lanthanide(III) coordination and one bipyridine function for selective Fe-II coordination. In aqueous solution and in the presence of these metals, the ligand is capable of self-assembly to form a rigid supramolecular metallostar structure, Fe[Gd(2)bpy(DTTA)(2)(H(2)0)(4)](3)(4-). We report here the physicochemical characterization of the dinuclear complex [Gd(2)bpy(DTTA)(2)(H2O)(4)](2-) and the metallostar Fe[Gd(2)bpy(DTTA)(2)(H2O)(4)](3)(4-) with regard to potential MRI contrast agent applications. A combination of pH potentiometry and H-1 NMR spectroscopy has been used to determine protonation constants for the ligand [bpy(DTTA)(2)](8-) and for the complexes [Febpy(DTTA)(2)(3)](22-) and [Y(2)bpy(DTTA)(2)](2-). In addition, stability constants have been measured for the dinuclear chelates [M(2)bpy(DTTA)(2)](n-) formed with M = Gd3+ and Zn2+ (logK(GdL) = 18.2 ; logK(ZnL) = 18.0 ; logK(ZnHL) = 3.4).