Exploring Inner-Sphere Water Interactions of Fe(II) and Co(II) Complexes of 12-Membered Macrocycles To Develop CEST MRI Probes
Exploring Inner-Sphere Water Interactions of Fe(II) and Co(II) Complexes of 12-Membered Macrocycles To Develop CEST MRI Probes
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DOI：
10.1021/acs.inorgchem.9b01072
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发表时间：
2019-07-01
影响因子：
4.6
通讯作者：
Morrow, Janet R.
中科院分区：
文献类型：
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作者：
Bond, Christopher J.;Sokolow, Gregory E.;Morrow, Janet R.
几个顺磁性Co（II）和Fe（II）的大环配合物的制备与引入结合水配体的目标，产生顺磁位移水H-1共振和顺磁性化学交换饱和转移（paraCEST）的应用。三个含酰胺侧基的12元大环，包括1，7-双（氨甲酰基甲基）-1，4，7，10-四氮杂环十二烷（DCMC），4，7，10-三合成了4，7，10-三氮杂-12-冠醚（N3 OA）和4，10-双（氨甲酰基甲基）-4，10-二氮杂-12-冠醚（NODA），并对它们的Co（II）配合物进行了固态和溶液的表征。[Co（DCMC）]Br-2的晶体结构为六配位的Co（II）中心，具有扭曲的八面体几何构型，而[Co（NODA）（OH 2）]Cl-2和[Co（N3 OA）]（NO3）（2）为七配位。成功地制备了NODA和NO 3A的类似Fe（II）配合物，但DCMC的配合物迅速氧化为Fe（III）形式。类似地，[Fe（NODA）]（2+）在几天内氧化，形成分离为mu-O桥接二聚体的Fe（III）络合物的晶体。磁化率值和顺磁NMR光谱的Fe（II）配合物的NODA和N3 OA，以及钴（II）配合物的DCMC，NODA，和N3 OA，是一致的高自旋复合物。确定了范围为60 ppm至70 ppm的CEST峰，其归因于酰胺侧基的NH基团。可变温度的O-17 NMR光谱的Co（II）和Fe（II）NODA配合物与水配体与散装水的快速交换是一致的。值得注意的是，这里提出的Co（II）和Fe（II）络合物产生大量的顺磁位移的本体水H-1共振，独立于具有内球水。
Several paramagnetic Co(II) and Fe(II) macrocyclic complexes were prepared with the goal of introducing a bound water ligand to produce paramagnetically shifted water H-1 resonances and for paramagnetic chemical exchange saturation transfer (paraCEST) applications. Three 12-membered macrocycles with amide pendent groups including 1,7-bis(carbamoylmethyl)-1,4,7,10-tetraazacyclodocane (DCMC), 4,7,10-tris(carbamoylmethyl)-,4,7,10-triaza-12-crown-ether (N3OA), and 4,10-bis(carbamoylmethyl)-4,10-diaza-12-crown-ether (NODA) were prepared and their Co(II) complexes were characterized in the solid state and in solution. The crystal structure of [Co(DCMC)]Br-2 featured a six-coordinated Co(II) center with distorted octahedral geometry, while [Co(NODA)(OH2)]Cl-2 and [Co(N3OA)](NO3)(2) were seven-coordinated. The analogous Fe(II) complexes of NODA and NO3A were successfully prepared, but the complex of DCMC oxidized rapidly to the Fe(III) form. Similarly, [Fe(NODA)](2+) oxidized over several days, forming crystals of the Fe(III) complex isolated as the mu-O bridged dimer. Magnetic susceptibility values and paramagnetic NMR spectra of the Fe(II) complexes of NODA and N3OA, as well as Co(II) complexes of DCMC, NODA, and N3OA, were consistent with high spin complexes. CEST peaks ranging from 60 ppm to 70 ppm, attributed to NH groups of the amide pendents, were identified. Variable-temperature O-17 NMR spectra of Co(II) and Fe(II) NODA complexes were consistent with rapid exchange of the water ligand with bulk water. Notably, the Co(II) and Fe(II) complexes presented here produced substantial paramagnetic shifts of bulk water H-1 resonances, independent of having an inner-sphere water.