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Redox-Induced Single-Molecule Magnetism in Mixed-Valent [2 × 2] Co4 Grid Complexes
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2016-04-18 00:00:00 , DOI: 10.1021/acs.inorgchem.6b00106 Jin Tong 1 , Serhiy Demeshko 1 , Michael John 1 , Sebastian Dechert 1 , Franc Meyer 1
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2016-04-18 00:00:00 , DOI: 10.1021/acs.inorgchem.6b00106 Jin Tong 1 , Serhiy Demeshko 1 , Michael John 1 , Sebastian Dechert 1 , Franc Meyer 1
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Homovalent [2 × 2] Co4 grid complexes [CoII4LH4](BF4)4 (1) and [CoII4LMe4](BF4)4 (2) with two new bis(terdentate) pyrazolate-bridged ligands, HLH = 3,5-bis(6-(1H-pyrazol-1-yl)pyrid-2-yl)pyrazole and HLMe = 4-methyl-3,5-bis(6-(1H-pyrazol-1-yl)pyrid-2-yl)pyrazole, were synthesized and comprehensively characterized. X-ray crystallographic analyses of 1 and 2 showed a square arrangement of cobalt(II) ions, each metal ion in distorted octahedral {N6} coordination created by two terdentate compartments from orthogonal ligand strands. Magnetic measurements revealed the metal ions’ high-spin (S = 3/2) state and moderate antiferromagnetic interactions to give an overall diamagnetic ST = 0 ground state of 1 and 2. Twofold oxidation, electrochemically or chemically, led to the dimixed-valent [2 × 2] Co4 grids [CoII2CoIII2LH4](BF4)6 (3) and [CoII2CoIII2LMe4](BF4)6 (4). ESI mass spectrometry confirmed the ruggedness of all grids 1–4 and their integrity in solution, and analysis of the UV/vis/NIR spectra suggested moderate electronic coupling. Solution 1H and 13C NMR spectra of paramagnetic 1–4 were recorded and confirmed that the dimixed-valent CoII2CoIII2 grids are charge-localized on the NMR time scale. X-ray crystallography revealed significant structural grid distortion upon oxidation, with the low-spin CoIII at opposite corners and in almost octahedral {N6} environment but the remaining CoII ions’ coordination sphere approaching a trigonal prism. SQUID studies showed the high-spin CoII to be magnetically isolated in the dimixed-valent CoII2CoIII2 grids, and both 3 and 4 to display frequency-dependent peaks in the out-of-phase (χ”) component of the alternating-current (ac) magnetic susceptibility data, characteristic for single molecule magnet (SMM) properties (with energy barriers Ueff/kB = 16 and 26 K, and relaxation times τ0 = 6.7·10–6 and 5.0·10–6 s for 3 and 4, respectively). The results are discussed in terms of cooperative effects that originate from elastic coupling within the grids, mediated by the rigid bridging ligands. These effects synergistically lead to the preferred trans configuration of the dimixed-valent CoII2CoIII2 grids and to structural distortions that are beneficial for SMM properties.
中文翻译：
混合价[2×2] Co 4网格配合物中氧化还原诱导的单分子磁性
同价[2×2] Co 4网格络合物[Co II 4 L H 4 ]（BF 4）4（1）和[Co II 4 L Me 4 ]（BF 4）4（2），带有两个新的双（terdentate）吡唑基桥联的配体，HL H = 3,5-双（6-（1 H-吡唑-1-基）吡啶-2-基）吡唑和HL Me = 4-甲基-3,5-双（6-（合成并全面表征了1 H-吡唑-1-基）吡啶-2-基）吡唑。1和2的X射线晶体学分析钴（II）离子呈方形排列，每个金属离子处于扭曲的八面体{N 6 }配位，由正交配体链的两个齿状隔室产生。磁测量表明，金属离子的高自旋（S = 3/2）状态和适度的反铁磁相互作用，从而使整体抗磁S T = 0基态为1和2。通过电化学或化学方法两次氧化，生成二价二价[2×2] Co 4网格[Co II 2 Co III 2 L H 4 ]（BF 4）6（3）和[Co II 2 Co III 2 L Me 4 ]（BF 4）6（4）。ESI质谱确认所有网格的坚固性1 - 4的UV / VIS和它们在溶液中的完整性，并分析/ NIR光谱表明中度的电子耦合。溶液1 H和13的顺磁性C NMR光谱1 - 4，记录和确认dimixed价钴II 2钴III 2网格在NMR时间尺度上是电荷局部的。X射线晶体学分析显示氧化后结构网格明显变形，低自旋Co III在相对的角和几乎八面体{N 6 }环境中，但其余Co II离子的配位球接近三角棱镜。SQUID研究表明，高自旋Co II在二价混合的Co II 2 Co III 2网格中被磁隔离，并且3和4都在异相中显示出频率相关的峰（χ”的交流（AC）的成分）磁化率数据，对于单分子磁铁特性（SMM）特性（与能量壁垒ü EFF / ķ乙= 16和26 K，和弛豫时间τ 0 = 6.7·10 -6和3和4分别为5.0·10 –6 s ）。讨论了结果，这些结果是由刚性桥接配体介导的，源自网格内弹性耦合的协同效应引起的。这些作用协同产生二价的Co II 2 Co III 2的优选反式构型 网格以及对SMM属性有利的结构变形。
更新日期：2016-04-18
中文翻译：
混合价[2×2] Co 4网格配合物中氧化还原诱导的单分子磁性
同价[2×2] Co 4网格络合物[Co II 4 L H 4 ]（BF 4）4（1）和[Co II 4 L Me 4 ]（BF 4）4（2），带有两个新的双（terdentate）吡唑基桥联的配体，HL H = 3,5-双（6-（1 H-吡唑-1-基）吡啶-2-基）吡唑和HL Me = 4-甲基-3,5-双（6-（合成并全面表征了1 H-吡唑-1-基）吡啶-2-基）吡唑。1和2的X射线晶体学分析钴（II）离子呈方形排列，每个金属离子处于扭曲的八面体{N 6 }配位，由正交配体链的两个齿状隔室产生。磁测量表明，金属离子的高自旋（S = 3/2）状态和适度的反铁磁相互作用，从而使整体抗磁S T = 0基态为1和2。通过电化学或化学方法两次氧化，生成二价二价[2×2] Co 4网格[Co II 2 Co III 2 L H 4 ]（BF 4）6（3）和[Co II 2 Co III 2 L Me 4 ]（BF 4）6（4）。ESI质谱确认所有网格的坚固性1 - 4的UV / VIS和它们在溶液中的完整性，并分析/ NIR光谱表明中度的电子耦合。溶液1 H和13的顺磁性C NMR光谱1 - 4，记录和确认dimixed价钴II 2钴III 2网格在NMR时间尺度上是电荷局部的。X射线晶体学分析显示氧化后结构网格明显变形，低自旋Co III在相对的角和几乎八面体{N 6 }环境中，但其余Co II离子的配位球接近三角棱镜。SQUID研究表明，高自旋Co II在二价混合的Co II 2 Co III 2网格中被磁隔离，并且3和4都在异相中显示出频率相关的峰（χ”的交流（AC）的成分）磁化率数据，对于单分子磁铁特性（SMM）特性（与能量壁垒ü EFF / ķ乙= 16和26 K，和弛豫时间τ 0 = 6.7·10 -6和3和4分别为5.0·10 –6 s ）。讨论了结果，这些结果是由刚性桥接配体介导的，源自网格内弹性耦合的协同效应引起的。这些作用协同产生二价的Co II 2 Co III 2的优选反式构型 网格以及对SMM属性有利的结构变形。
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