Biological phosphates can coordinate metal ions and their complexes are common in living systems. Dynamics of mutual oxygen atom exchange in the tetrahedral group in complexes has not been investigated. Here, we present a direct experimental proof of the exchange (“phosphonate rotation”) in model Ln(III) complexes of monophosphonate H4dota analogue which alters phosphorus atom chirality of coordinated phosphonate monoester. Combination of macrocycle‐based isomerism with P‐based chirality leads to several diastereoisomers. The (non)‐coordinated oxygens were distinguished through 17O‐labelled phosphonate group and their mutual exchange was followed by various NMR techniques and DFT calculations. The process is sterically demanding and occurs through bulky bidentate (k2‐PO2)– coordination. It was observed on complexes of large Ln(III) ions in twisted‐square antiprism diastereoisomers. The process energy increases for smaller Ln(III) ions (298ΔG‡(exp./DFT) = 51.8/52.1 and 61.0 / 71.5 kJ mol−1 for La(III) and Eu(III), respectively). These results are helpful in design of such complexes for MRI and protein paramagnetic NMR probes. It demonstrates usefulness of 17O NMR to study solution dynamics in complexes involving phosphorus acid derivatives. The results may inspire use of this method to study dynamics of phosphoric acid derivatives (as e.g. phosphorus acid‐based inhibitors of metalloenzymes) in different areas of chemistry.

中文翻译：

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通过 17O-NMR 直接观察单（膦酸乙酯）DOTA 类似物的镧系元素 (III) 配合物中配位膦酸基团的动力学。

生物磷酸盐可以配位金属离子，其配合物在生命系统中很常见。配合物中四面体基团中相互氧原子交换的动力学尚未被研究。在这里，我们提出了单膦酸酯 H4dota 类似物的模型 Ln(III) 复合物中交换（“膦酸酯旋转”）的直接实验证明，它改变了配位膦酸酯单酯的磷原子手性。基于大环的异构体与基于P的手性的组合产生了几种非对映异构体。 （非）配位氧通过 17O 标记的膦酸酯基团进行区分，并通过各种 NMR 技术和 DFT 计算跟踪它们的相互交换。该过程对空间要求很高，并且通过大体积的双齿 (k2-PO2)-配位发生。在扭曲方形反棱镜非对映异构体中的大 Ln(III) 离子复合物上观察到了这一现象。对于较小的 Ln(III) 离子，过程能量会增加（La(III) 和 Eu(III) 分别为 298ΔG‡(exp./DFT) = 51.8/52.1 和 61.0 / 71.5 kJ mol−1）。这些结果有助于设计用于 MRI 和蛋白质顺磁 NMR 探针的复合物。它证明了 17O NMR 在研究涉及磷酸衍生物的配合物中的溶液动力学方面的有用性。结果可能会启发使用这种方法来研究不同化学领域中磷酸衍生物（例如基于磷酸的金属酶抑制剂）的动力学。