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首页> 外文期刊>Physical chemistry chemical physics: PCCP >A combined high-field EPR and quantum chemical study on a weakly ferromagnetically coupled dinuclear Mn(III) complex. A complete analysis of the EPR spectrum beyond the strong coupling limit
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A combined high-field EPR and quantum chemical study on a weakly ferromagnetically coupled dinuclear Mn(III) complex. A complete analysis of the EPR spectrum beyond the strong coupling limit

机译：弱铁磁耦合双核Mn（III）配合物的高场EPR和量子化学研究相结合。超出强耦合极限的EPR频谱的完整分析

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摘要

The electronic and magnetic properties of polynuclear complexes, in particular the magnetic anisotropy (zero field splitting, ZFS), the leading term of the spin Hamiltonian (SH), are commonly analyzed in a global manner and no attempt is usually made to understand the various contributions to the anisotropy at the atomic scale. This is especially true in weakly magnetically coupled systems. The present study addresses this problem and investigates the local SH parameters using a methodology based on experimental measurements and theoretical calculations. This work focuses on the challenging mono μ-oxo bis μ-acetato dinuclear Mn~(-1) complex: [Mn2~(III)(μ-O)(μ-OAc)2L2](PF6)2 (with L = trispyrrolidine-1,4,7-triazacydononane) (1), which is particularly difficult for EPR spectroscopy because of its large magnetic anisotropy and the weak ferromagnetic interaction between the two Mn'" ions. High field (up to 12 T) and high frequency (190-345 GHz) EPR experiments have been recorded for 1 between 5 and 50 K. These data have been analyzed by employing a complex Hamiltonian, which encompasses terms describing the local and inter-site interactions. Density functional theory and multireference correlated ab initio calculations have been used to estimate the ZFS of the Mn~(III) ions (D_(Mn) = +4,29 cm~(-1), E_(Mn)/D_(Mn) = 0.19) and the Euler angles reflecting the relative orientation of the ZFS tensor for each Mn~(III) (α = -52°, β = 28°, γ = 3°). This analysis allowed the accurate determination of the local parameters: D_(Mn) = +4.50 cm"', E_(Mn)/D_(Mn) = 0.07, α = -35°, β = 23°, γ = 2°. The spin ladder approach has also been applied, but only the parameters of the ground spin state of 1 have been accurately determined (D4 = +1.540 cm~(-1), E4/D4 = 0.107). This is not sufficient to allow for the determination of the local parameters. The validity and practical performance of both approaches have been discussed.
机译：多核配合物的电子和磁性，特别是磁各向异性（零场分裂，ZFS），自旋哈密顿量（SH）的主要术语，通常以全局方式进行分析，通常不尝试理解各种形式。在原子尺度上对各向异性的贡献。在弱磁耦合系统中尤其如此。本研究解决了这个问题，并使用基于实验测量和理论计算的方法研究了局部SH参数。这项工作的重点是具有挑战性的单μ-氧代双μ-乙酰双核Mn〜（-1）配合物：[Mn2〜（III）（μ-O）（μ-OAc）2L2]（PF6）2（L =三吡咯烷-1,4,7-三氮杂十二碳四烯烷（1），由于其大的磁各向异性和两个Mn'“离子之间的弱铁磁相互作用，因此在EPR光谱分析中特别困难。高磁场（最高12 T）和高频率（190-345 GHz）EPR实验记录了5至50 K之间的1，这些数据已通过使用复杂的哈密顿量进行了分析，其中包含描述局部和站点间相互作用的术语密度泛函理论和多参考相关的从头算计算已用于估计Mn〜（III）离子的ZFS（D_（Mn）= +4.29 cm〜（-1），E_（Mn）/ D_（Mn）= 0.19）和欧拉角反射每个Mn〜（III）的ZFS张量的相对方向（α= -52°，β= 28°，γ= 3°）。这种分析可以精确确定局部参数：D_（Mn）= +4.50厘米“'，E_（Mn） / D_（Mn）= 0.07，α= -35°，β= 23°，γ= 2°。自旋阶梯方法也已被应用，但是仅精确地确定了地面自旋状态1的参数（D4 = +1.540 cm〜（-1），E4 / D4 = 0.107）。这不足以允许确定局部参数。讨论了两种方法的有效性和实际性能。

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