State Key Laboratory of Coordination Chemistry, Collaborative Innovation Center of Advanced Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China.
Dalton Trans. 2018 Jun 19;47(24):7925-7933. doi: 10.1039/c8dt01112e.
A novel nitronyl nitroxide diradical based on the pyrazine ring, BNITPz (1, BNITPz = 2,2'-(3,6-dimethylpyrazine-2,5-diyl)bis(1-hydroxy-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-1-oxyl-3-oxide)) and six new dinuclear compounds based on the reduced form of 1, namely [Ln(hfac)3]2(BHIMPz)(H2O)2 (Ln = Gd (2Gd), Dy (3Dy), Ho (4Ho), Er (5Er), Tm (6Tm), Yb (7Yb); BHIMPz = 2,2'-(3,6-dimethylpyrazine-2,5-diyl)bis(4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide); hfac = hexafluoroacetylacetonate) were prepared and characterized. Single crystal X-ray crystallographic analyses confirmed the diradical structure of 1, and revealed that complexes 2Gd-7Yb are isostructural and crystallize in the triclinic space group P1[combining macron]. The reduced form BHIMPz was confirmed by its longer N-O bond lengths and the characteristic N-H stretching absorption at 3500-3300 cm-1 of the IR spectroscopy of 2Gd-7Yb. In 2Gd-7Yb, the lanthanide ions are eight-coordinated in a square antiprism environment (D4d). Two symmetric related Ln(iii) ions are bridged by the reduced BHIMPz ligand to form a dinuclear structure. Magnetic measurements revealed the antiferromagnetic exchange interaction between the two radicals of the diradical ligand 1 through the pyrazine ring. For complexes 2Gd to 7Yb with the reduced non-radical ligand, their magnetic properties are consistent with the isolated LnIII centers. Alternating-current (ac) magnetic susceptibility investigations indicate that complexes 3Dy and 7Yb exhibit field-induced frequency dependence, which indicates the presence of slow relaxation of the magnetization. Ab initio calculations were performed on these compounds to understand their magnetic anisotropy and their different magnetic dynamics.
一种基于吡嗪环的新型硝酰氮自由基化合物 BNITPz（1，BNITPz = 2,2'-(3,6-二甲基吡嗪-2,5-二基)双(1-羟基-4,4,5,5-四甲基-4,5-二氢-1H-咪唑-1-氧-3-氧化物)）和六个基于 1 的还原形式的新双核化合物，即[Ln(hfac)3]2(BHIMPz)(H2O)2（Ln = Gd（2Gd），Dy（3Dy），Ho（4Ho），Er（5Er），Tm（6Tm），Yb（7Yb）；BHIMPz = 2,2'-(3,6-二甲基吡嗪-2,5-二基)双(4,4,5,5-四甲基-4,5-二氢-1H-咪唑-3-氧化物)；hfac = 乙酰丙酮酸盐）被制备并进行了表征。单晶 X 射线晶体学分析证实了 1 的自由基结构，并表明配合物 2Gd-7Yb 是同构的，在三斜晶系 P1[组合]空间群中结晶。还原形式 BHIMPz 通过其较长的 N-O 键长和 IR 光谱中 3500-3300 cm-1 处的特征 N-H 伸缩吸收得到证实 2Gd-7Yb。在 2Gd-7Yb 中，镧系离子在八配位的四方反棱柱体环境（D4d）中。两个对称相关的 Ln(iii)离子被还原的 BHIMPz 配体桥接，形成双核结构。磁测量表明，通过吡嗪环，自由基配体 1 的两个自由基之间存在反铁磁交换相互作用。对于具有还原非自由基配体的 2Gd 至 7Yb 配合物，它们的磁性与孤立的 LnIII 中心一致。交流（ac）磁化率研究表明，配合物 3Dy 和 7Yb 表现出磁场诱导的频率依赖性，这表明磁化的缓慢弛豫存在。对这些化合物进行了从头算计算，以了解它们的磁各向异性和不同的磁动力学。
