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Magnetic Anisotropy drives Magneto-Chiral Dichroism in a Chiral Molecular Helix probed with Visible Light
Journal of the American Chemical Society ( IF 15.0 ) Pub Date : 2020-07-16 , DOI: 10.1021/jacs.0c06166
Matteo Atzori 1 , Fabio Santanni 2 , Ivan Breslavetz 1 , Kévin Paillot 1 , Andrea Caneschi 3 , Geert L J A Rikken 1 , Roberta Sessoli 2 , Cyrille Train 1
Affiliation  

Magneto-Chiral Dichroism (MChD) is a non-reciprocal manifestation of light-matter interaction that can be observed in chiral magnetized systems. It features a differential absorption of unpolarized light depending on the relative orientation of the magnetic field and the light wavevector and on the absolute configuration of the system. The relevance of this effect for optical readout of magnetic data calls for a complete understanding of the microscopic parameters driving MChD with an easy-accessible and non-demaging light source, such as visible light. For this purpose, here we report on MChD detected with visible light on a chiral magnetic helix formulated as [MnIII(cyclam)(SO4)]ClO4∙H2O (cyclam = 1,4,8,11-tetraazacyclotetradecane) featuring antiferromagnetically coupled anisotropic MnIII ions. Alternate current susceptibility measurements revealed the existence of a single-chain magnet behavior hidden below the canted antiferromagnetism (TN = 5.8 K) already evidenced by direct current magnetometry. A detailed analysis of the optical absorption gives access to the value of the zero-field splitting parameter D (2.9 cm-1), which quantifies the magnetic anisotropy of the MnIII centers. Below the magnetic ordering temperature of the material, the MChD spectra exhibit intense absolute configuration dependent MChD signals reaching record values of ca. 12% of the absorbed intensity for the two electronic transitions most influenced by the spin-orbit coupling of the MnIII ion. These findings set a clear route towards the design and preparation of highly MChD-responsive molecular materials.

中文翻译:

磁各向异性驱动可见光探测的手性分子螺旋中的磁手性二色性

磁手性二色性 (MChD) 是光与物质相互作用的非互易表现,可以在手性磁化系统中观察到。它的特点是对非偏振光的不同吸收取决于磁场和光波矢量的相对方向以及系统的绝对配置。这种效应与磁性数据的光学读出的相关性要求完全了解驱动 MChD 的微观参数,使用易于访问且不会损坏的光源,例如可见光。为此,我们在这里报告了在手性磁性螺旋上用可见光检测到的 MChD,公式为 [MnIII(cyclam)(SO4)]ClO4∙H2O(cyclam = 1,4,8,11-四氮杂环十四烷),具有反铁磁耦合各向异性 MnIII离子。交流磁化率测量表明存在隐藏在倾斜反铁磁性 (TN = 5.8 K) 之下的单链磁铁行为,直流磁力测量法已经证明了这一点。对光吸收的详细分析提供了零场分裂参数 D (2.9 cm-1) 的值,该值量化了 MnIII 中心的磁各向异性。在材料的磁性有序温度以下,MChD 光谱表现出强烈的绝对构型依赖 MChD 信号,达到了约 100 的记录值。受 MnIII 离子的自旋轨道耦合影响最大的两个电子跃迁的吸收强度的 12%。这些发现为设计和制备高 MChD 响应分子材料设定了明确的路线。
更新日期:2020-07-16
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