1. Modulation of the magnetic dynamics of pentagonal-bipyramidal Co(II) complexes by fine-tuning the coordination microenvironment.
- Author
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Qin, Yuanyuan, Wu, Yuewei, Luo, Shuchang, Xi, Jing, Guo, Yan, Ding, Yi, Zhang, Jun, and Liu, Xiangyu
- Subjects
MAGNETIC anisotropy ,LIGAND field theory ,LIGANDS (Chemistry) ,AB-initio calculations ,ACTIVATION energy ,SINGLE crystals ,X-ray diffraction - Abstract
Four air-stable mononuclear Co(II) complexes, with the formulas [Co(dapbh)(H
2 O)(CH3 OH)] (1), [Co(Hdapbh)(N3 )(CH3 OH)]·(CH3 OH) (2), [Co(H2 aapbh)(CH3 OH)2 ]·(NO3 )2 (3) and [Co(H2 bapbh)(H2 O)(NO3 )]·(NO3 ) (4), have been synthesized and structurally characterized by single crystal X-ray diffraction. In all of the complexes, the Co(II) centers constrained by the rigid pentadentate ligand H2 LR with two protonable hydrogens adopt a heptacoordinated pentagonal-bipyramidal geometry. The combined analyses of magnetic data and ab initio calculations unveil large easy-plane magnetic anisotropies for these complexes (D = +37.338, +37.273, +41.138 and +41.139 cm−1 for 1–4, respectively), which indicate that the chemical alterations of the equatorial ligand and the ligand field strength in the axial positions synergistically fine-tune the magnitude of the D values. Magnetic investigations demonstrate the field-induced single-ion magnetic behavior in complexes 1, 2 and 4 with diverse energy barriers (Ueff ) of 12.25 for 1, 44.15 for 2 and 48.72 K for 4, corresponding to the geometrical distortion of the heptacoordinated Co(II) ion. That is, the greatest deviation from the ideal D5h symmetry in 4 is responsible for the highest barrier. [ABSTRACT FROM AUTHOR]- Published
- 2022
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