o-Aminophenol-N,N,O-triacetate, known as APTRA, is one of the most well-established ligands for targeting magnesium ions but, like other aminocarboxylate ligands, it binds Ca²⁺ much more strongly than Mg²⁺. The synthesis of an O-phosphinate analogue of APTRA is reported here, namely o-aminophenol-N,N-diacetate-O-methylene-methylphosphinate, referred to as APDAP. Metal binding studies monitored using UV-visible spectroscopy show that the affinity of APDAP for Ca²⁺ is reduced by over two orders of magnitude compared to APTRA, and for Zn²⁺ by over three orders of magnitude, whereas the affinity for Mg²⁺ is attenuated to a much lesser extent, by a factor of only about 7. The selectivity towards Mg²⁺ is thus substantially improved. DFT calculations support the notion that longer P–O and P–C bonds in APDAP (compared to corresponding C–O and C–C bonds in APTRA) favour a larger angle at the metal, an effect that is less unfavourable for smaller ions like Mg²⁺ than for larger ions such as Ca²⁺. Derivatives of APDAP can be anticipated that will offer improved sensing of Mg²⁺ in the presence of Ca²⁺, in the physiologically important millimolar concentration range.

中文翻译：

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基于次膦酸盐的螯合物 提高了对Mg ^2+的选择性：APDAP与APTRA †

邻氨基苯酚-N，N，O-三乙酸酯，称为APTRA，是最成熟的靶向镁离子的配体之一，但与其他氨基羧酸盐配体一样，它与Ca ^2+的结合比与Mg ^2+的结合要牢固得多。一个的合成Ô APTRA的-phosphinate类似物这里报道，即ø -aminophenol- Ñ，Ñ -diacetate- ö亚甲基-甲基次膦酸，称为APDAP。使用紫外-可见光谱监测的金属结合研究表明，与APTRA和Zn相比，APDAP对Ca ²⁺的亲和力降低了两个数量级以上^{2 +}超过三个数量级，而对Mg ²⁺的亲和力衰减的程度要小得多，仅为约7倍。因此，对Mg ²⁺的选择性大大提高了。DFT计算支持以下观点：APDAP中较长的P–O和P–C键（与APTRA中相应的C–O和C–C键）有利于金属的更大角度，这种效果对于较小的离子（如较小的离子）不利Mg ²⁺比较大的离子（例如Ca ^2+）高。可以预料，在生理上重要的毫摩尔浓度范围内，如果存在Ca ²⁺，则APDAP的衍生物将改善Mg ^2+的感测。