Departamento de Química Fundamental, Facultade de Ciencias, Universidade da Coruña, Campus da Zapateira, Rúa da Fraga 10, 15008 A Coruña, Spain.
Inorg Chem. 2012 Oct 15;51(20):10893-903. doi: 10.1021/ic301369z. Epub 2012 Sep 27.
A new macrocyclic ligand, N,N'-bis[(6-carboxy-2-pyridyl)methyl]-2,11-diaza3.3pyridinophane (H(2)BPDPA), was prepared, and its coordination properties toward the Ln(III) ions were investigated. The hydration numbers (q) obtained from luminescence lifetime measurements in aqueous solution of the Eu(III) and Tb(III) complexes indicate that they contain one inner-sphere water molecule. The structure of the complexes in solution has been investigated by (1)H and (13)C NMR spectroscopy, as well as by theoretical calculations performed at the density functional theory (B3LYP) level. The minimum-energy conformation calculated for the Yb(III) complex is in excellent agreement with the experimental structure in solution, as demonstrated by analysis of the Yb(III)-induced paramagnetic (1)H shifts. Nuclear magnetic relaxation dispersion (NMRD) profiles and (17)O NMR measurements recorded on solutions of the Gd(III) complex were used to determine the parameters governing the relaxivity. The results show that this system is endowed with a relatively fast water-exchange rate k(ex)(298) = 63 × 10(6) s(-1). Thermodynamic stability constants were determined by pH-potentiometric titration at 25 °C in 0.1 M KCl. The stability constants, which fall within the range logK(LnL) = 12.5-14.2, point to a relatively low stability of the complexes primarily as a consequence of the low basicity of the ligand.
一种新的大环配体，N,N'-双[(6-羧基-2-吡啶基)甲基]-2,11-二氮杂3.3吡啶并菲（H(2)BPDPA），被制备出来，并研究了其对 Ln(III)离子的配位性质。在 Eu(III)和 Tb(III)配合物的水溶液中通过荧光寿命测量得到的水合数（q）表明它们含有一个内界水分子。通过（1）H和（13）C NMR 光谱以及在密度泛函理论（B3LYP）水平上进行的理论计算，研究了配合物在溶液中的结构。对于 Yb(III)配合物，计算出的最低能量构象与溶液中的实验结构非常吻合，这可以通过分析 Yb(III)诱导的顺磁（1）H位移得到证明。在 Gd(III)配合物的溶液中记录的核磁共振弛豫分散（NMRD）谱和（17）O NMR 测量用于确定控制弛豫率的参数。结果表明，该体系具有相对较快的水交换速率 k(ex)(298) = 63 × 10(6) s(-1)。在 25°C 下，在 0.1 M KCl 中通过 pH 电位滴定法确定热力学稳定常数。稳定常数的范围为 logK(LnL) = 12.5-14.2，表明配合物的稳定性相对较低，主要是由于配体的碱性较低。
