Effect of magnetic fields on the methyl rotation in a paramagnetic cobalt( ii ) complex. Quasielastic neutron scattering studies
Effect of magnetic fields on the methyl rotation in a paramagnetic cobalt( ii ) complex. Quasielastic neutron scattering studies
复制标题
磁场对顺磁性钴(ii)络合物中甲基旋转的影响。
DOI：
10.1039/c8cp01660g
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发表时间：
2018
影响因子：
3.3
通讯作者：
Xue, Zi-Ling
中科院分区：
文献类型：
--
作者：
Stavretis, Shelby E.;Mamontov, Eugene;Moseley, Duncan H.;Cheng, Yongqiang;Daemen, Luke L.;Ramirez-Cuesta, A. J.;Xue, Zi-Ling
分子动力学是金属配合物的基本性质。这些动力学过程，特别是对外部磁场作用下的顺磁配合物的动力学过程，通常还没有得到很好的理解。采用准弹性中子散射（QENS）方法研究了Co(acac)2(D2O)2 （1-d4, acac = acetylacetonate）在0 - 4t磁场中的动力学。在80-100 K时，acac配体上甲基的旋转是主要的动力学过程。这种旋转由于磁场的增加而减慢。QENS的研究表明，这些顺磁性Co（II）分子中的甲基不表现为孤立的单元，这与早期磁化率研究的结果一致，表明存在分子间相互作用。DFT计算表明，1中的未配对电子自旋密度分散到acac和H2O配体的原子上。在5-100 K的非弹性中子能谱（INS）中也观察到1-d4的甲基扭转。这里的QENS和INS结果有助于理解化合物在固体状态下的动力学。
Molecular dynamics is a fundamental property of metal complexes. These dynamic processes, especially for paramagnetic complexes under external magnetic fields, are in general not well understood. Quasielastic neutron scattering (QENS) in 0–4 T magnetic fields has been used to study the dynamics of Co(acac)2(D2O)2 (1-d4, acac = acetylacetonate). At 80–100 K, rotation of the methyl groups on the acac ligands is the dominant dynamical process. This rotation is slowed down by the magnetic field increase. Rotation times at 80 K are 5.6(3) × 10−10 s at 0 T and 2.04(10) × 10−9 s at 4 T. The QENS studies suggest that methyl groups in these paramagnetic Co(II) molecules do not behave as isolated units, which is consistent with results from earlier magnetic susceptibility studies indicating the presence of intermolecular interactions. DFT calculations show that unpaired electron spin density in 1 is dispersed to the atoms of both acac and H2O ligands. Methyl torsions in 1-d4 have also been observed at 5–100 K in inelastic neutron spectroscopy (INS). The QENS and INS results here help understand the dynamics of the compound in the solid state.