Light- and Chemical-Doping-Induced Magnetic Behavior of Eu Molecular Systems
Light- and Chemical-Doping-Induced Magnetic Behavior of Eu Molecular Systems
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DOI：
10.1021/acs.inorgchem.3c01154
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发表时间：
2023-07-28
影响因子：
4.6
通讯作者：
Hla，Saw-Wai
中科院分区：
文献类型：
--
作者：
Rajh，Tijana;Masson，Eric;Hla，Saw-Wai
利用变温电子顺磁共振（VT-EPR）研究了环境和氧化态对几种铕配位化合物的影响。我们发现，虽然Eu（III）螯合物是抗磁性的，但简单的化学还原可以形成顺磁性物质。与本研究中研究的Eu分子配合物的扭曲的dd3h对称性一致，还原配合物的EPR谱显示了轴对称信号（g⊥= 2.001和g∥= 1.994），这些信号是用两个核自旋为5/2的Eu同位素（151Eu和153Eu分别具有48%和52%的自然丰度）和核因子151Eu/153Eu = 2.27成功模拟的。水溶性配合物Eu(dipic)3at 4 K光照导致配体-金属电荷转移（LMCT），导致Eu（II）在菱形环境中形成（gx= 2.006,gy= 1.995,gz= 1.988）。LMCT的存在影响了Eu(dipic)3的发光，配合物预还原为Eu(II)(dipic)3可逆地降低了红色发光，呈现微弱的CT蓝色发光。此外，南瓜形大环Cucurbit b[7]uril包封了大部分二配体，抑制了配体到金属的电荷转移，防止了光照下Eu（II）的形成。
Variable temperature electron paramagnetic resonance (VT-EPR) was used to investigate the role of the environment and oxidation states of several coordinated Eu compounds. We find that while Eu(III) chelating complexes are diamagnetic, simple chemical reduction results in the formation of paramagnetic species. In agreement with the distortedD3hsymmetry of Eu molecular complexes investigated in this study, the EPR spectrum of reduced complexes showed axially symmetric signals (g⊥= 2.001 andg∥= 1.994) that were successfully simulated with two Eu isotopes with nuclear spin 5/2 (151Eu and153Eu with 48% and 52% natural abundance, respectively) and nuclearg-factors151Eu/153Eu = 2.27. Illumination of water-soluble complex Eu(dipic)3at 4 K led to the ligand-to-metal charge transfer (LMCT) that resulted in the formation of Eu(II) in a rhombic environment (gx= 2.006,gy= 1.995,gz= 1.988). The existence of LMCT affects the luminescence of Eu(dipic)3, and pre-reduction of the complex to Eu(II)(dipic)3reversibly reduces red luminescence with the appearance of a weak CT blue luminescence. Furthermore, encapsulation of a large portion of the dipic ligand with Cucurbit[7]uril, a pumpkin-shaped macrocycle, inhibited ligand-to-metal charge transfer, preventing the formation of Eu(II) upon illumination.