Ekanger Levi A, Mills Devin R, Ali Meser M, Polin Lisa A, Shen Yimin, Haacke E Mark, Allen Matthew J
Department of Chemistry, Wayne State University , 5101 Cass Avenue, Detroit, Michigan 48202, United States.
Department of Neurology, Henry Ford Hospital , 1 Ford Place, Detroit, Michigan 48202, United States.
Inorg Chem. 2016 Oct 17;55(20):9981-9988. doi: 10.1021/acs.inorgchem.6b00629. Epub 2016 May 31.
The 3+ and 2+ oxidation states of europium have drastically different magnetic and spectroscopic properties. Electrochemical measurements are often used to probe Eu oxidation state changes, but a full suite of spectroscopic characterization is necessary to demonstrate conversion between these two oxidation states in solution. Here, we report the facile conversion of an europium(III) tetraglycinate complex into its Eu analogue. We present electrochemical, luminescence, electron paramagnetic resonance, UV-visible, and NMR spectroscopic data demonstrating complete reversibility from the reduction and oxidation of the 3+ and 2+ oxidation states, respectively. The Eu-containing analogue has kinetic stability within the range of clinically approved Gd-containing complexes using an acid-catalyzed dissociation experiment. Additionally, we demonstrate that the 3+ and 2+ oxidation states provide redox-responsive behavior through chemical-exchange saturation transfer or proton relaxation, respectively. These results will be applicable to a wide range of redox-responsive contrast agents and Eu-containing complexes.
铕的 +3 和 +2 氧化态具有截然不同的磁性和光谱性质。电化学测量常被用于探测铕氧化态的变化，但要证明这两种氧化态在溶液中的相互转化，全套的光谱表征是必要的。在此，我们报告了一种铕（III）四甘氨酸配合物向其 Eu 类似物的简便转化。我们展示了电化学、发光、电子顺磁共振、紫外可见和核磁共振光谱数据，分别证明了 +3 和 +2 氧化态还原和氧化的完全可逆性。通过酸催化解离实验，含 Eu 的类似物在临床批准的含 Gd 配合物范围内具有动力学稳定性。此外，我们证明 +3 和 +2 氧化态分别通过化学交换饱和转移或质子弛豫提供氧化还原响应行为。这些结果将适用于广泛的氧化还原响应造影剂和含 Eu 配合物。
