Environmental influence on the single-molecule magnet behavior of [Mn(III)6Cr(III)]3+: molecular symmetry versus solid-state effects.
Environmental influence on the single-molecule magnet behavior of [Mn(III)6Cr(III)]3+: molecular symmetry versus solid-state effects.
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环境对 [Mn(III)6Cr(III)]3 单分子磁体行为的影响：分子对称性与固态效应。
DOI：
10.1021/ic301406j
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发表时间：
2012
影响因子：
4.6
通讯作者：
T. Glaser
中科院分区：
文献类型：
--
作者：
V. Hoeke;Maik Heidemeier;E. Krickemeyer;A. Stammler;H. Bögge;J. Schnack;A. Postnikov;T. Glaser
[Mn（III）（6）Cr（III）]（3+）系列配合物的结构、光谱和磁性用X射线单晶衍射（XRD）、傅里叶变换红外光谱（FT-IR）、电子吸收光谱、元素分析等方法对[{（t-Bu（2））Mn（III）（3）}（2）{Cr（III）（CN）（6）}]（3+）化合物进行了研究，电喷雾电离质谱（ESI-MS）和基质辅助激光解吸电离质谱（MALDI-MS）、循环伏安法、AC和DC磁性测量以及理论分析。以[Cr（III）（CN）（6）]（3-）为配位基的晶体结构表现出由氢键（1）或共价键（2）三价阳离子和三价阴离子形成的（准）一维（1D）链。棒状阴离子乳酸盐使[Mn（III）（6）Cr（III）]（3+）配合物在高度对称的空间群R3[overline]（3）中形成棒状堆积，分子S（6）轴共线排列。球形阴离子BPh（4）（-）的引入导致[Mn（III）（6）Cr（III）]（3+）配合物具有非共线取向的较不对称的晶体结构（4-6），如近似分子C（3）轴之间的角度在2°-69°范围内没有特定值所证明的。对新鲜分离的晶体（1a和3a-6a）、空气干燥的晶体（3b-6 b）和真空干燥的粉末样品（3c-6c）的交流磁性测量表明，所有样品的U（eff）值高达28 K时都具有单分子磁体（SMM）行为。直流磁数据进行了分析，适当的自旋哈密顿量，包括各向同性交换，零场分裂，塞曼相互作用，考虑到相对取向的D-张量的全矩阵对角化。对3a-6a和3c-6c的模拟表明，三核亚基中Mn（III）离子之间存在弱反铁磁交换（J（Mn-Mn）= -0.70至-0.85 cm（-1），（ex）= -2∑（i<j）J（ij）∑（i）·∑（j）），其通过Cr-C N-Mn途径被更强的反铁磁相互作用克服（J（Cr-Mn）= -3.00至-5.00 cm（-1）），得到了S（t）=（21）/（2）自旋基态的整体亚铁磁耦合方案。在U（eff），J（锰锰），和J（铬锰）的研究样品的差异合理化的分子和晶体结构的细微变化。特别是，Mn-N（C N）键长和J（Cr-Mn）交换耦合之间的磁结构相关性推断从磁性测量和DFT计算证实。对[Mn（III）（6）Cr（III）]（3+）的详细研究结果允许制定一些关键配方，以合理改善SMM行为。
The structural, spectroscopic, and magnetic properties of a series of [Mn(III)(6)Cr(III)](3+) (= [{(talen(t-Bu(2)))Mn(III)(3)}(2){Cr(III)(CN)(6)}](3+)) compounds have been investigated by single-crystal X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and electronic absorption spectroscopy, elemental analysis, electro spray ionization-mass spectrometry (ESI-MS) and matrix-assisted laser desorption ionization-mass spectrometry (MALDI-MS), cyclic voltammetry, AC and DC magnetic measurements, as well as theoretical analysis. The crystal structures obtained with [Cr(III)(CN)(6)](3-) as a counterion exhibit (quasi-)one-dimensional (1D) chains formed by hydrogen-bonded (1) or covalently linked (2) trications and trianions. The rod-shaped anion lactate enforces a rod packing of the [Mn(III)(6)Cr(III)](3+) complexes in the highly symmetric space group R3[overline] (3) with a collinear arrangement of the molecular S(6) axes. Incorporation of the spherical anion BPh(4)(-) leads to less-symmetric crystal structures (4-6) with noncollinear orientations of the [Mn(III)(6)Cr(III)](3+) complexes, as evidenced by the angle between the approximate molecular C(3) axes taking no specific values in the range of 2°-69°. AC magnetic measurements on freshly isolated crystals (1a and 3a-6a), air-dried crystals (3b-6b), and vacuum-dried powder samples (3c-6c) indicate single-molecule magnet (SMM) behavior for all samples with U(eff) values up to 28 K. The DC magnetic data are analyzed by a full-matrix diagonalization of the appropriate spin-Hamiltonian including isotropic exchange, zero-field splitting, and Zeeman interaction, taking into account the relative orientation of the D-tensors. Simulations for 3a-6a and 3c-6c indicate a weak antiferromagnetic exchange between the Mn(III) ions in the trinuclear subunits (J(Mn-Mn) = -0.70 to -0.85 cm(-1), Ĥ(ex) = -2∑(i<j )J(ij)Ŝ(i)·Ŝ(j)) that is overcome by the stronger antiferromagnetic interaction via the Cr-C≡N-Mn pathway (J(Cr-Mn) = -3.00 to -5.00 cm(-1)), leading to an overall ferrimagnetic coupling scheme with an S(t) = (21)/(2) spin ground state. The differences in U(eff), J(Mn-Mn), and J(Cr-Mn) for the investigated samples are rationalized in terms of subtle variations in the molecular and crystal structures. In particular, a magnetostructural correlation between the Mn-N(C≡N) bond length and the J(Cr-Mn) exchange coupling is inferred from the magnetic measurements and corroborated by DFT calculations. The results of this detailed study on [Mn(III)(6)Cr(III)](3+) allow the formulation of some key recipes for a rational improvement of the SMM behavior.
影响因子：
15
作者：
Karotsis, Georgios;Kennedy, Stuart;Brechin, Euan K.
通讯作者：
Brechin, Euan K.
影响因子：
38.3
作者：
Timco, Grigore A.;Carretta, Stefano;Winpenny, Richard E. P.
通讯作者：
Winpenny, Richard E. P.