Panda Suvam Kumar, Torres Julia, Kremer Carlos, Singh Akhilesh Kumar
Indian Institute of Technology Bhubaneswar, Khordha, Odisha 752050, India.
Área de Química Inorgánica - DEC, Facultad de Química, Universidad de la República, Montevideo, 11800, Uruguay.
Dalton Trans. 2023 Oct 3;52(38):13594-13607. doi: 10.1039/d3dt01422c.
Co(II) and Ni(II) complexes of two tri-pyridine-based ligands with two hydroxy and two amide exchangeable protons (TDTA) and with six amide exchangeable protons (TMTP) were investigated for application as paraCEST-based magnetic resonance imaging (MRI) contrast agents. The two hydroxy groups present in the TDTA ligand were found to be passive while the amide group was active towards the CEST process. In the case of the Co(II) and Ni(II) complexes of the TMTP ligand, all three coordinated amide groups participated in the exchange process, and excellent CEST signals were observed. The X-ray structure of the four complexes revealed the seven-coordinate geometry of Co(II) complexes and the six-coordinate geometry of Ni(II) complexes. The presence of amide protons and hydroxy protons in the complexes was detected by the NMR method. The stability of the complexes in solution at high temperatures, in different pH ranges and acidic conditions, in the presence of competing cations, and biologically relevant anions was investigated. Potentiometric titrations were carried out to determine the ligand's protonation constants and the complexes' thermodynamic stability constant at 25.0 °C and = 0.15 mol L NaClO. ParaCEST studies of [Co(TMTP)] and [Ni(TMTP)] at variable pH and variable pulse power are highlighted.
研究了两种含两个羟基和两个可交换酰胺质子的三吡啶基配体（TDTA）以及含六个可交换酰胺质子的三吡啶基配体（TMTP）的钴（II）和镍（II）配合物作为基于顺磁化学交换饱和转移（paraCEST）的磁共振成像（MRI）造影剂的应用。发现TDTA配体中的两个羟基是惰性的，而酰胺基对CEST过程具有活性。在TMTP配体的钴（II）和镍（II）配合物中，所有三个配位酰胺基都参与了交换过程，并观察到了出色的CEST信号。四种配合物的X射线结构揭示了钴（II）配合物的七配位几何结构和镍（II）配合物的六配位几何结构。通过核磁共振（NMR）方法检测了配合物中酰胺质子和羟基质子的存在。研究了配合物在高温、不同pH范围和酸性条件下、存在竞争阳离子和生物相关阴离子时在溶液中的稳定性。进行了电位滴定，以确定配体在25.0 °C和离子强度I = 0.15 mol L NaClO条件下的质子化常数和配合物的热力学稳定性常数。重点介绍了[Co(TMTP)]和[Ni(TMTP)]在可变pH和可变脉冲功率下的paraCEST研究。
