EFFECT OF OUTER-SPHERE HYDRATION ON LIQUID-LIQUID PARTITION OF TRIS-p-DIKETONATES OF 3d METAL IONS

Macrocyclic complexes of scandium radionuclides as precursors for diagnostic and therapeutic radiopharmaceuticals

“…We have found that the 46 Sc-DOTA complex was more hydrophilic than 177 Lu-DOTA and less hydrophilic than 68 Ga-DOTA, which suggests different coordination spheres in these complexes. Since Sc 3+ is smaller than Lu 3+ therefore, according to the rule stating that in aqueous solutions coordinatively saturated complexes of smaller cations are more strongly hydrated in the outer coordination sphere [50], the 46 Sc-DOTA peak appeared before the peak of 177 Lu-DOTA. 68 Ga-DOTA, which has two free carboxylate groups, appeared to be the most hydrophilic complex.…”

Outer-Sphere Hydration - a Factor Differentiating Tetrakis(acetylacetonato)actinides(IV) in Liquid-Liquid Partition Systems

“…2a the Μ-Ο distances have been taken from crystallographic data for solid acetylacetonates of tetravalent metals [11 -13], except for Pu and Bk, which were calculated by adding Shannon's ionic radii of M 4+ (CN 8) [14] to the O 2 " radius (140 pm). An approximately linear relationship can be observed between the logarithm of the partition coefficients and the reciprocal of the metal-to-ligand distance in the chelates, similar to that found for acetylacetonates of trivalent metals [6]. In Fig.…”

“…Also the literature AS 0 values for U(acac) 4 (230 J K" 1 mol" 1 [3]) and Np(acac) 4 (250 J · K" 1 • mol -1 [2]) belong to the same set of values when taking into account the differences in the systems studied. Thus the differences observed in the P 4 values are mainly of enthalpic character, as it has also been found for the M(acac) 3 species [6], Fig. 2 shows the log Ρ values plotted as a function of the metal-to-ligand distance in the chelate.…”

“…Recently, it has been found that partition coefficients of coordinatively saturated acetylacetonates of trivalent 3 d cations decrease with decreasing radius of the central metal ion [6]. The aim of the present work was to examine whether partition coefficients of acetylacetonates of tetravalent actinides also decrease with decreasing radius of the central metal ions, and if the differences can be similarly explained by the effect of outer-sphere hydration [7,8] of the chelates in the aqueous phase, i.e.…”

Features of Solvent Extraction of Lanthanides and Actinides

“…However, metal complexes in the aqueous phase undergo also 'outer-sphere hydration' by means of hydrogen bond formed between water molecules and the donor oxygen atoms of the coordinated ligands [22,23]. It can been shown that the extent of this hydration depends on the central metal ion which affects proton-acceptor properties of the ligand oxygen atoms [24]. For acetylacetonates of tetravalent actinides, in particularly for U, Np, Pu and Bk, the values of partition coefficient regularly decrease with increasing atomic number of metal.…”