School of Chemistry, University of Southampton, Highfield Campus, Southampton, SO17 1BJ, UK.
Department of Chemistry, Durham University, South Road, Durham, DH1 3LE, UK.
Angew Chem Int Ed Engl. 2017 Sep 25;56(40):12215-12218. doi: 10.1002/anie.201706931. Epub 2017 Aug 24.
A detailed analysis of paramagnetic NMR shifts in a series of isostructural lanthanide complexes relavant to PARASHIFT contrast agents reveals unexpected trends in the magnetic susceptibility anisotropy that cannot be explained by the commonly used Bleaney's theory. Ab initio calculations reveal that the primary assumption of Bleaney's theory-that thermal energy is larger than the ligand field splitting-does not hold for the lanthanide complexes in question, and likely for a large fraction of lanthanide complexes in general. This makes the orientation of the magnetic susceptibility tensor differ significantly between complexes of different lanthanides with the same ligand: one of the most popular assumptions about isostructural lanthanide series is wrong.
对一系列结构同型的镧系金属配合物的顺磁 NMR 位移进行详细分析，揭示了 PARASHIFT 对比剂的顺磁各向异性中无法用通常使用的 Bleaney 理论解释的意外趋势。从头算计算表明，Bleaney 理论的主要假设——热能大于配体场分裂——不适用于所研究的镧系金属配合物，而且可能不适用于大多数镧系金属配合物。这使得具有相同配体的不同镧系金属配合物的磁化率张量的方向有很大差异：关于结构同型镧系元素系列的最常见假设之一是错误的。
