The synthesis of ligand L based on a 2,6-bis[(N,N-bis(methylene phosphonic acid)aminomethyl] pyridine scaffold is described. Potentiometry combined with UV-Vis absorption spectrophotometric titrations were used to determine the protonation constants of the ligand and the stability constants of its corresponding Cu(II), Ni(II), Zn(II) and Ga(III) cations (0.1 M NaClO4, 25.0 °C). The physico–chemical approach revealed very large stability constants for Cu(II) complexation (logKCuL = 22.71(7)) reflected in a very high pCuII value of ∼ 15.5 (pH = 7.4, [L]tot = 10−5 M, [Cu]tot = 10−6 M), close to those measured for the strong methylphosphonate functionalized cyclen chelators. Based on a literature survey, a correlation is proposed between the pK values of branched polyamine ligands and their stability constants for Cu(II) complexation, allowing for an estimation of the latter on the basis of the protonation constants of L. Ligand L was also shown to be very selective towards Cu(II) compared to the other cations studied (ΔlogK > 4). UV-Vis spectroscopy and kinetic measurements indicated that the formation of the cupric complexes with L is very fast, which, in combination with all other properties, makes it an excellent non-cyclic target for Cu(II) radiopharmaceutical within the frame of 64Cu positron emission tomography imaging and radiotherapy.
描述了基于2,6-bis[(N,N-bis(亚
甲基膦酸)胺基甲基]
吡啶骨架的
配体L的合成。采用电位法结合UV-Vis吸收光谱滴定法确定了该
配体的质子化常数以及其对应的Cu(II)、Ni(II)、Zn(II)和Ga(III)阳离子的稳定常数(0.1 M NaClO4,25.0 °C)。物理
化学方法揭示了Cu(II)络合的非常大稳定常数(logKCuL = 22.71(7)),在pCuII值约为15.5(pH = 7.4, [L]tot = 10−5 M, [Cu]tot = 10−6 M)中体现出来,接近于强
甲基膦酸功能化环烯
配体测得的值。根据文献调查,提出了支链聚胺
配体的pK值与其Cu(II)络合稳定常数之间的相关性,允许根据L的质子化常数估算后者。与研究中的其他阳离子相比,
配体L对Cu(II)表现出很强的选择性(ΔlogK > 4)。UV-Vis光谱和动力学测量表明,L与Cu(II)形成的络合物的反应非常迅速,这与其他所有性质结合在一起,使其成为64Cu正电子发射断层成像和放射治疗领域中一种优秀的非环状Cu(II)放射药物目标。