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From unprecedented 2,2′-bisimidazole-bridged rare earth organometallics to magnetic hysteresis in the dysprosium congener
Inorganic Chemistry Frontiers ( IF 6.1 ) Pub Date : 2023-05-31 , DOI: 10.1039/d3qi00546a Florian Benner 1 , Selvan Demir 1
Inorganic Chemistry Frontiers ( IF 6.1 ) Pub Date : 2023-05-31 , DOI: 10.1039/d3qi00546a Florian Benner 1 , Selvan Demir 1
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The first use of the bare 2,2′-bisimidazole (H2bim) ligand in rare earth metal chemistry is presented. A series of symmetric dinuclear complexes [(Cp*2RE)2(μ-bim)] were synthesized from the salt metathesis reaction of the lithium salt Li2(bim) with Cp*2RE(BPh4) (RE = Y (1), Gd (2), Dy (3); Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl). The isostructural complexes 1–3 were unambiguously characterized through elemental analysis, NMR, IR and UV/Vis spectroscopy, single-crystal X-ray diffraction, SQUID magnetometry and density functional theory (DFT) calculations. Intriguingly, the compounds are redox-inactive both on the timescale of chemical and electrochemical experiments. Herein, a rationale for the redox innocence of the bim2− ligand is provided by calculations of the electron affinity and ionization potential, both correlating well with topologically similar structures of comparable complexes. Remarkably, the Dy complex 3 shows open magnetic hysteresis loops up to 5 K which is rare for lanthanide SMMs with bridging diamagnetic entities. AC magnetic susceptibility measurements at zero field revealed slow magnetic relaxation up to 26 K leading to an effective energy barrier to spin reversal of Ueff = 154(2) cm−1 and τ0 = 5(1) × 10−8 s. The lanthanides are weakly antiferromagnetically coupled, where the J value for the Gd-congener 2 was determined to be −0.074(2) cm−1.
中文翻译：
从前所未有的 2,2'-双咪唑桥接稀土金属有机化合物到镝同系物中的磁滞现象
介绍了在稀土金属化学中首次使用裸露的 2,2'-双咪唑 (H 2 bim) 配体。锂盐Li 2 ( bim )与Cp* 2 RE(BPh 4 ) (RE = Y ( 1 ), Gd ( 2 ), Dy ( 3 ); Cp* = 1,2,3,4,5-五甲基环戊二烯基)。同构复合物1–3通过元素分析、NMR、IR 和 UV/Vis 光谱、单晶 X 射线衍射、SQUID 磁力计和密度泛函理论 (DFT) 计算明确表征。有趣的是，这些化合物在化学和电化学实验的时间尺度上都没有氧化还原活性。在此，通过电子亲和力和电离势的计算提供了bim 2−配体的氧化还原无辜性的基本原理，两者都与可比配合物的拓扑相似结构密切相关。值得注意的是，Dy 络合物3显示高达 5 K 的开放磁滞回线，这对于具有桥接抗磁实体的镧系元素 SMM 来说是罕见的。零场下的交流磁化率测量显示缓慢的磁弛豫高达 26 K，导致自旋反转的有效能垒U eff = 154(2) cm -1和τ 0 = 5(1) × 10 -8 s。镧系元素是弱反铁磁耦合的，其中Gd 同系物2的J值确定为 -0.074(2) cm -1。
更新日期：2023-05-31
中文翻译：
从前所未有的 2,2'-双咪唑桥接稀土金属有机化合物到镝同系物中的磁滞现象
介绍了在稀土金属化学中首次使用裸露的 2,2'-双咪唑 (H 2 bim) 配体。锂盐Li 2 ( bim )与Cp* 2 RE(BPh 4 ) (RE = Y ( 1 ), Gd ( 2 ), Dy ( 3 ); Cp* = 1,2,3,4,5-五甲基环戊二烯基)。同构复合物1–3通过元素分析、NMR、IR 和 UV/Vis 光谱、单晶 X 射线衍射、SQUID 磁力计和密度泛函理论 (DFT) 计算明确表征。有趣的是，这些化合物在化学和电化学实验的时间尺度上都没有氧化还原活性。在此，通过电子亲和力和电离势的计算提供了bim 2−配体的氧化还原无辜性的基本原理，两者都与可比配合物的拓扑相似结构密切相关。值得注意的是，Dy 络合物3显示高达 5 K 的开放磁滞回线，这对于具有桥接抗磁实体的镧系元素 SMM 来说是罕见的。零场下的交流磁化率测量显示缓慢的磁弛豫高达 26 K，导致自旋反转的有效能垒U eff = 154(2) cm -1和τ 0 = 5(1) × 10 -8 s。镧系元素是弱反铁磁耦合的，其中Gd 同系物2的J值确定为 -0.074(2) cm -1。
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