An EPR and 1H NMR active mixed-valence manganese (III/II/III) trinuclear compound.
An EPR and 1H NMR active mixed-valence manganese (III/II/III) trinuclear compound.
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DOI：
10.1021/ic991430x
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发表时间：
2000-06
影响因子：
4.6
通讯作者：
V. Tangoulis;Dora A. Malamatari;G. Spyroulias;C. Raptopoulou;and Aris Terzis;D. Kessissoglou
中科院分区：
文献类型：
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作者：
V. Tangoulis;Dora A. Malamatari;G. Spyroulias;C. Raptopoulou;and Aris Terzis;D. Kessissoglou
用x射线晶体学对一种混合价Mn(III)-Mn(II)-Mn（III）三核配合物MnIIIMnIIMnIII(Hsaladhp)2(Sal)4.2CH3CN(1)进行了结构表征，其中H3saladhp为三齿希夫碱配体。Mn(III)Mn(II)Mn（III）角严格按照晶体反演对称的要求为180度。该配合物被两个末端Mn（III）离子束缚在扭曲的方形金字塔几何结构中。Mn (III)……Mn（II）的分离度为3.495 A。三核配合物表现出小的反铁磁交换J耦合。在10 ~ 300 K温度范围内，拟合得到的磁性参数为J1 = -5.7 cm-1, g = 2.02, zJ = -0.19 cm-1, R = 0.004。在CHCl3和四氢呋喃玻璃中得到了4 K时的EPR光谱。低场EPR信号是两个信号的叠加，一个以g = 3.6为中心，另一个以g = 4.1为中心，观察到超精细结构，表明S = 3/2状态。此外，在g = 2.0处还有一个19线信号。多线信号与S2或S0*态的信号比较好。1H NMR数据显示，三核化合物在CHCl3溶液中保持完整性。配合物1的晶体数据：[C54H52N4O18Mn3]， M = 1209.82，三斜，空间群P1， a = 10.367(6) a, b = 11.369(6) a, c = 13.967(8) a；alpha = 112.56(1)度，beta = 93.42(2)度，gamma = 115.43(1)度，Z = 1
A mixed-valence Mn(III)-Mn(II)-Mn(III) trinuclear complex of stoichiometry MnIIIMnIIMnIII(Hsaladhp)2(Sal)4.2CH3CN (1), where H3saladhp is a tridentate Schiff-base ligand, has been structurally characterized with X-ray crystallography. The Mn(III)Mn(II)Mn(III) angles are strictly 180 degrees as required by crystallographic inversion symmetry. The complex is valence-trapped with two terminal Mn(III) ions in a distorted square pyramidal geometry. The Mn(III)...Mn(II) separation is 3.495 A. The trinuclear complex shows small antiferromagnetic exchange J coupling. The magnetic parameters obtained from the fitting procedure in the temperature range 10-300 K are J1 = -5.7 cm-1, g = 2.02, zJ = -0.19 cm-1, and R = 0.004. The EPR spectrum was obtained at 4 K in CHCl3 and in tetrahydrofuran glasses. The low-field EPR signal is a superposition of two signals, one centered around g = 3.6 and the other, for which hyperfine structure is observed, centered around g = 4.1 indicating an S = 3/2 state. In addition, there is a 19-line signal at g = 2.0. The multiline signal compares well with that observed for the S2 or S0* states of the oxygen-evolving complex. 1H NMR data reveal that the trinuclear compound keeps its integrity into the CHCl3 solution. Crystal data for complex 1: [C54H52N4O18Mn3], M = 1209.82, triclinic, space group P1, a = 10.367(6) A, b = 11.369(6) A, c = 13.967(8) A; alpha = 112.56(1) degree, beta = 93.42(2) degrees, gamma = 115.43(1) degree, Z = 1.