Very Large Magnetic Anisotropy of Cage Cobalt(II) Complexes with a Rigid Cholesteryl Substituent from Paramagnetic NMR Spectroscopy

Alexander A Pavlov; Svetlana A Savkina; Alexander S Belov; Yan Z Voloshin; Yulia V Nelyubina; Valentin V Novikov

doi:10.1021/acsomega.8b00772

Very Large Magnetic Anisotropy of Cage Cobalt(II) Complexes with a Rigid Cholesteryl Substituent from Paramagnetic NMR Spectroscopy

ACS Omega. 2018 May 4;3(5):4941-4946. doi: 10.1021/acsomega.8b00772. eCollection 2018 May 31.

Authors

Alexander A Pavlov¹, Svetlana A Savkina¹, Alexander S Belov¹, Yan Z Voloshin^{1

2}, Yulia V Nelyubina^{1

2}, Valentin V Novikov¹

Affiliations

¹ Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilova Street, 28, 119991 Moscow, Russia.
² Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Leninskii prospekt, 31, 117901 Moscow, Russia.

Abstract

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 ¹H and ¹³C 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.