A CuII2 Paramagnetic Chemical Exchange Saturation Transfer Contrast Agent Enabled by Magnetic Exchange Coupling
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- 作者：Kang Du ; T. David Harris
- 刊名：Journal of the American Chemical Society
- 出版年：2016
- 出版时间：June 29, 2016
- 年：2016
- 卷：138
- 期：25
- 页码：7804-7807
- 全文大小：266K
- 年卷期：0
- ISSN：1520-5126
文摘
The ability of magnetic exchange coupling to enable observation of paramagnetic chemical exchange saturation transfer (PARACEST) in transition metal ions with long electronic relaxation times (τs) is demonstrated. Metalation of the dinucleating, tetra(carboxamide) ligand HL with Cu2+ in the presence of pyrophosphate (P2O7)4– affords the complex [LCuII2(P2O7)]−. Solution-phase variable-temperature magnetic susceptibility data reveal weak ferromagnetic superexchange coupling between the two S = 1/2 CuII centers, with a coupling constant of J = +2.69(5) cm–1, to give an S = 1 ground state. This coupling results in a sharpened NMR line width relative to a GaCu analogue, indicative of a shortening of τs. Presaturation of the amide protons in the Cu2 complex at 37 °C leads to a 14% intensity decrease in the bulk water 1H NMR signal through the CEST effect. Conversely, no CEST effect is observed in the GaCu complex. These results provide the first example of a Cu-based PARACEST magnetic resonance contrast agent and demonstrate the potential to expand the metal ion toolbox for PARACEST agents through introduction of magnetic exchange coupling.