SYNTHESIS, STABILITY, AND STRUCTURE OF GADOLINIUM(III) AND YTTRIUM(III) MACROCYCLIC POLY(AMINO CARBOXYLATES)
SYNTHESIS, STABILITY, AND STRUCTURE OF GADOLINIUM(III) AND YTTRIUM(III) MACROCYCLIC POLY(AMINO CARBOXYLATES)
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DOI：
10.1021/ic00094a021
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发表时间：
1994-08-03
影响因子：
4.6
通讯作者：
TWEEDLE, MF
中科院分区：
文献类型：
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作者：
KUMAR, K;CHANG, CA;TWEEDLE, MF
用电位法和分光光度法分别测定了DO3A、HP-DO3A和DOTA三种大环多氨基羧酸酯在25.0+/-0.1度-C、离子强度为0.1M((TMA)CI)下的配体质子化常数及其与Gd(III)和Y(III)形成络合物的稳定常数。在Na+离子存在下，配体的第一质子化常数降低，表明配体优先与Na+结合。对溴化钠和DOTA的四叔丁酯的络合物的晶体结构分析证实了这一发现，表明Na+离子被深深地络合在配体笼子中。Gd(III)和Y(III)配合物的热力学稳定常数顺序为：DOTA>；HP-DO3A>；DTPA>；DO3A>；EDTA。测定了Hp-DO3A的Gd(III)、Y(III)等结构配合物、[Na(TBU-DOTA)]Br配合物和DO3A的H_2SO4盐的晶体结构。九配位的Gd(III)和Y(III)离子是配位为八配位的，其中水分子占据第九(顶端)位置。Na+在DOTA四酯中的八配位结合构型与(Gd/Y)HP-DO3A络合物中的构型相似，不同之处在于钠离子在配位体腔中的深度约为0.3埃。无金属的D03A配体(在SEC和跨环氮上质子化)是为了金属配位而预先组织的。
The ligand protonation constants of three macrocyclic poly(amino carboxylates), DO3A, HP-DO3A, and DOTA, and stability constants governing formation of their Gd(III) and Y(III) complexes have been determined by potentiometric and spectrophotometric methods, respectively, at 25.0 +/- 0.1-degrees-C and at a constant ionic strength of 0.1 M ((TMA)CI). The first protonation constant of the ligands was lowered in the presence of Na+ ions, indicating a preferred binding of the ligands to Na+. Corroborating this finding, a crystal structure analysis of a complex of NaBr and of the tetra-tert-butyl ester of DOTA revealed that the Na+ ion was chelated deep in the ligand cage. The thermodynamic stability constants of the Gd(III) and Y(III) complexes followed the order: DOTA > HP-DO3A > DTPA > DO3A > EDTA. Crystal structures of the isostructural Gd(III) and Y(III) complexes of HP-DO3A, the [Na(tBu-DOTA)] Br complex, and the H2SO4 salt of DO3A were determined. The nine-coordinated Gd(III) and Y(III) ions were eight-coordinate by the ligand, with a water molecule occupying the ninth (apical) position. The geometry of the eight-coordinate binding of Na+ in the DOTA tetraester was similar to that in the (Gd/Y)HP-DO3A complexes, except that sodium was approximately 0.3 angstrom deeper in the ligand cavity. The metal-free D03A ligand (protonated on the sec and transannular nitrogens) was preorganized for metal coordination.