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Slow magnetic relaxation in dinuclear Co(III)-Co(II) complexes containing a five-coordinated Co(II) centre with easy-axis anisotropy.

Mengyao LiuYimou YangRong JingShaojun ZhengAihua YuanZhen-Xing WangShu-Chang LuoXiangyu Y LiuHui-Hui CuiZhong-Wen OuyangLei Chen
Published in: Dalton transactions (Cambridge, England : 2003) (2022)
Two air-stable Co(III)-Co(II) mixed-valence complexes of molecular formulas [Co II Co III (L)(DMAP) 3 (CH 3 COO)]·H 2 O·CH 3 OH (1) and [Co II Co III (L)(4-Pyrrol) 3 (CH 3 COO)]·0.5CH 2 Cl 2 (2) (H 4 L = 1,3-bis-(5-methyl pyrazole-3-carboxamide) propane; DMAP = 4-dimethylaminopyridine; and 4-Pyrrol = 4-pyrrolidinopyridine) were synthesized and characterized by single-crystal X-ray crystallography, high-field electron paramagnetic resonance (HFEPR) spectroscopy, and magnetic measurements. Both complexes possess one five-coordinated paramagnetic Co(II) ion and one six-coordinated Co(III) ion with octahedral geometry. Direct-current magnetic susceptibility and magnetization measurements show the easy-axis magnetic anisotropy that is also confirmed by low-temperature HFEPR measurements and theoretical calculations. Frequency- and temperature-dependent alternating-current magnetic susceptibility measurements reveal their field-assisted slow magnetic relaxation, which is a characteristic behavior of single-molecule magnets (SMMs), caused by the individual Co(II) ion. The effective energy barrier of complex 1 (49.2 cm -1 ) is significantly higher than those of the other dinuclear Co(III)-Co(II) SMMs. This work hence presents the first instance of the dinuclear Co(III)-Co(II) single-molecule magnets with a five-coordinated environment around the Co(II) ion.
Keyphrases
  • single molecule
  • high resolution
  • magnetic resonance imaging
  • molecular docking
  • dual energy