Pavlov Alexander A, Savkina Svetlana A, Belov Alexander S, Voloshin Yan Z, Nelyubina Yulia V, Novikov Valentin V
Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilova Street, 28, 119991 Moscow, Russia.
Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Leninskii prospekt, 31, 117901 Moscow, Russia.
ACS Omega. 2018 May 4;3(5):4941-4946. doi: 10.1021/acsomega.8b00772. eCollection 2018 May 31.
Variable-temperature NMR spectroscopy has recently emerged as a new alternative to the magnetometry methods for studying single molecule magnets. Its use is based on an accurate determination of magnetic susceptibility tensor anisotropy Δχ, which is not always achievable due to some contact contribution to NMR chemical shifts and possible conformational dynamics. Here, we applied this approach to cholesteryl-substituted cage cobalt(II) complexes featuring a very large magnetic anisotropy. Conformational rigidity and large size of the cholesteryl substituent with many magnetically nonequivalent nuclei resulted in an excellent convergence of experimental and calculated H and C chemical shifts, thus allowing for the determination of Δχ value for all of the synthesized cobalt(II) complexes with a very high accuracy and providing a more reliable zero-field splitting energy for further calculations.
可变温度核磁共振光谱法最近已成为研究单分子磁体的磁强计方法的一种新替代方法。它的应用基于对磁化率张量各向异性Δχ的精确测定，由于核磁共振化学位移的一些接触贡献和可能的构象动力学，这并非总是能够实现。在这里，我们将这种方法应用于具有非常大磁各向异性的胆固醇取代的笼状钴（II）配合物。胆固醇取代基具有构象刚性且尺寸较大，带有许多磁不等价核，这导致实验和计算得到的氢和碳化学位移具有出色的一致性，从而能够以非常高的精度确定所有合成钴（II）配合物的Δχ值，并为进一步计算提供更可靠的零场分裂能。
