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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Mn~(2+) complexes of 1-oxa-4,7-diazacyclononane based ligands with acetic, phosphonic and phosphinic acid pendant arms: Stability and relaxation studies
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Mn~(2+) complexes of 1-oxa-4,7-diazacyclononane based ligands with acetic, phosphonic and phosphinic acid pendant arms: Stability and relaxation studies

机译：基于1-oxa-4,7-二氮杂环壬烷的配体与乙酸，膦酸和次膦酸侧链的Mn〜（2+）配合物：稳定性和弛豫研究

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摘要

A new class of macrocyclic ligands based on 1-oxa-4,7-diazacyclononane was synthesized and their Mn~(2+) complexes were investigated with respect to stability and relaxation properties. Each ligand has two pendant arms involving carboxylic (H_2L~1 - 1-oxa-4,7-diazacyclononane-4, 7-diacetic acid), phosphonic (H_4L~2 - 1-oxa-4,7- diazacyclononane-4,7-bis(methylenephosphonic acid)), phosphinic (H _2L~3 - 1-oxa-4,7-diazacyclononane-4,7- bis(methylenephosphinic acid)) or phenylphosphinic (H_2L~4 - 1-oxa-4,7-diazacyclononane-4,7-bis[methylene(phenyl)phosphinic acid]) acid moieties. H_2L~3 and H_2L~4 were synthesized for the first time. The crystal structure of the Mn~(2+) complex with H_2L~4 confirmed a coordination number of 6 for Mn~(2+). The protonation constants of all ligands and the stability constants of their complexes with Mn~(2+) and some biologically or biomedically relevant metal ions were determined by potentiometry. The protonation sequence of H_2L~3 was followed by ~1H and ~(31)P NMR titration and the second protonation step was attributed to the second macrocyclic nitrogen atom. The potentiometric data revealed a relatively low thermodynamic stability of the Mn~(2+) complexes with all ligands investigated. For H_2L~3 and H_2L ~4, full Mn~(2+) complexation cannot be achieved even with 100% ligand excess. The transmetallation of MnL~1 and MnL~2 with Zn~(2+) was too fast to be followed at pH 6. Variable temperature ~1H NMRD and ~(17)O NMR measurements have been performed on MnL~1 and MnL~2 to provide information on water exchange and rotational dynamics. The ~(17)O chemical shifts indicate hydration equilibrium between mono- and bishydrated species for MnL~1, while MnL~2 is monohydrated. The water exchange is considerably faster on MnL~1 (k_(ex)~(298) = 1.2 × 10~9 s~(-1)) than on MnL~2 (k_(ex)~(298) = 1.2 × 10~7 s~(-1)). Small endogenous anions (phosphate, carbonate, citrate) do not replace the coordinated water in either of the complexes, but they induce their slow decomposition. All Mn~(2+) complexes are stable toward air-oxidation.
机译：合成了一类基于1-oxa-4,7-二氮杂环壬烷的大环配体，并研究了其Mn〜（2+）配合物的稳定性和弛豫性能。每个配体具有两个侧基臂，涉及羧酸（H_2L〜1-1-氧杂-4,7-二氮杂环壬烷-4、7-二乙酸），膦酸（H_4L〜2-1-氧杂-4,7-二氮杂环壬烷-4,7） -双（亚甲基膦酸）），次膦酸（H _2L〜3-1-氧杂-4,7-二氮环壬烷-4,7-双（亚甲基次膦酸））或苯基次膦酸（H_2L〜4-1-氧杂-4,7-二氮杂环壬烷-4，7-双[亚甲基（苯基）次膦酸]酸部分。首次合成了H_2L〜3和H_2L〜4。 Mn〜（2+）与H_2L〜4的配合物的晶体结构证实了Mn〜（2+）的配位数为6。用电位法测定了所有配体的质子化常数及其与Mn〜（2+）以及某些生物学或生物医学上有关的金属离子的配合物的稳定性常数。 H_2L〜3的质子化序列之后是〜1H和〜（31）P NMR滴定，第二个质子化步骤归因于第二个大环氮原子。电位数据表明，Mn〜（2+）配合物与所有配体的热力学稳定性相对较低。对于H_2L〜3和H_2L〜4，即使配体过量100％，也无法完全实现Mn〜（2+）络合。 MnL〜1和MnL〜2与Zn〜（2+）的金属化太快而无法在pH 6下进行追踪。在MnL〜1和MnL〜上进行了〜1H NMRD和〜（17）O NMR可变温度测量2提供有关水交换和旋转动力学的信息。 〜（17）O化学位移表明MnL〜1为一水合物和二水合物之间的水合平衡，而MnL〜2为一水合物。 MnL〜1（k_（ex）〜（298）= 1.2×10〜9 s〜（-1））上的水交换比MnL〜2（k_（ex）〜（298）= 1.2×10 〜7 s〜（-1））。较小的内源性阴离子（磷酸根，碳酸根，柠檬酸根）不能代替任何一种配合物中的配位水，但会引起其缓慢分解。所有的Mn〜（2+）配合物对空气氧化均稳定。

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