Huang Ping, Shaikh Nizamuddin, Anderlund Magnus F, Styring Stenbjörn, Hammarström Leif
Molecular Biomimetics, Department of Photochemistry and Molecular Science, Uppsala University, Villavägen 6, S-75236 Uppsala, Sweden.
J Inorg Biochem. 2006 May;100(5-6):1139-46. doi: 10.1016/j.jinorgbio.2006.02.006. Epub 2006 Mar 6.
Simulation of X- and Q-band electron paramagnetic resonance (EPR) spectra of an unsymmetric dinuclear [Mn(2)(II,III)L(mu-OAc)(2)]ClO(4) complex (1), (L is the dianion of 2-{[N,N-bis(2-pyridylmethyl)amino]methyl}-6-{[N-(3,5-di-tert-butyl-2-hydroxybenzyl)-N-(2-pyridylmethyl)amino]methyl}-4-methylphenol) was performed using one consistent set of simulation parameters. Rhombic g-tensors and hyperfine tensors were necessary to obtain satisfactory simulation of the EPR spectra. The anisotropy of the effective hyperfine tensors of each individual (55)Mn ion was further analyzed in terms of intrinsic hyperfine tensors. Detailed analysis shows that the hyperfine anisotropy of the Mn(III) ion is a result of the Jahn-Teller effect and thus an inherent character. In contrast, the anomalous hyperfine anisotropy of the Mn(II) ion is attributed as being transferred from the Mn(III) ion through the spin exchange interaction. The anisotropy parameter for the Mn(II) is deduced as D(II)=-1.26+/-0.2cm(-1). This is the first reported D(II) value for a Mn(II) ion in a weakly exchange coupled mixed-valence Mn(2)(II,III) complex with a bis-mu-acetato-bridge. The [see text] electronic configuration of the Mn(III) ion in 1 is revealed by the negative sign of its intrinsic hyperfine tensor anisotropy, Deltaa(III)=a(z)-a(x,y)=-46cm(-1). Lower spectral resolution of the Q-band EPR spectrum as compared to the X-band EPR spectrum is associated to large line width broadening of the x- and y-components in contrast to the z-component. The origins of the unequal distribution of line width between the z- and x-, y-components are discussed.
使用一组一致的模拟参数对不对称双核[Mn₂(II,III)L(μ - OAc)₂]ClO₄配合物(1)（L为2-{[N,N - 双(2 - 吡啶甲基)氨基]甲基}-6-{[N - (3,5 - 二叔丁基 - 2 - 羟基苄基)-N - (2 - 吡啶甲基)氨基]甲基}-4 - 甲基苯酚的二价阴离子）的X波段和Q波段电子顺磁共振(EPR)谱进行了模拟。为了获得令人满意的EPR谱模拟结果，需要菱形g张量和超精细张量。根据本征超精细张量进一步分析了每个单独的⁵⁵Mn离子有效超精细张量的各向异性。详细分析表明，Mn(III)离子的超精细各向异性是 Jahn - Teller效应的结果，因此是一种固有特性。相比之下，Mn(II)离子异常的超精细各向异性归因于通过自旋交换相互作用从Mn(III)离子转移而来。推导出Mn(II)的各向异性参数为D(II)= - 1.26±0.2cm⁻¹。这是首次报道的具有双μ - 乙酸根桥的弱交换耦合混合价Mn₂(II,III)配合物中Mn(II)离子的D(II)值。配合物1中Mn(III)离子的[见正文]电子构型由其本征超精细张量各向异性的负号Δa(III)=a(z) - a(x,y)= - 46cm⁻¹揭示。与X波段EPR谱相比，Q波段EPR谱的较低光谱分辨率与x和y分量的大线宽展宽有关，而z分量则相反。讨论了z分量与x、y分量之间线宽分布不均的起源。
