Université Joseph Fourier Grenoble 1/CNRS, Département de Chimie Moléculaire, UMR-5250, Laboratoire de Chimie Inorganique Redox, Institut de Chimie Moléculaire de Grenoble FR- CNRS-2607, BP-53, 38041 Grenoble Cedex 9, France.
Inorg Chem. 2009 Nov 2;48(21):10281-8. doi: 10.1021/ic901409y.
The trinuclear oxo bridged manganese cluster, Mn(IV)(3)O(4)(terpy)(terpyO(2))(2)(H(2)O)(2) (5) (terpy = 2,2':2'',6'-terpyridine and terpyO(2) = 2,2':2'',6'-terpyridine 1,1''-dioxide), was isolated in an acidic aqueous medium from the reaction of MnSO(4), terpy, and oxone as chemical oxidant. The terpyO(2) ligands were generated in situ during the synthesis by partial oxidation of terpy. The complex crystallizes in the monoclinic space group P21/n with a = 14.251(5) A, b = 15.245(5) A, c = 24.672(5) A, alpha = 90.000(5) degrees, beta = 92.045(5) degrees, gamma = 90.000(5) degrees, and Z = 4. The triangular {Mn(IV)(3)O(4)}(4+) core observed in this complex is built up of a basal Mn(mu-O)(2)Mn unit where each Mn ion is linked to an apical Mn ion via mono(mu-O) bridges. The facial coordination of the two tridentate terpyO(2) ligands to the Mn(mu-O)(2)Mn unit allows the formation of the triangular core. 5 is also the first structurally characterized Mn complex with polypyridinyl N-oxide ligands. The variable-temperature magnetic susceptibility data for this complex, in the range of 10-300 K, are consistent with an S = 1/2 ground state and were fit using the spin Hamiltonian H(eff) with S(1) = S(2) = S(3) = 3/2, J(a) = -37 (+/-0.5) and J(b) = -53 (+/-1) cm(-1), where J(a) and J(b) are exchange constants through the mono-mu-oxo and the di-mu-oxo bridges, respectively. The doublet ground spin state of 5 is confirmed by EPR spectroscopic measurements. Density functional theory (DFT) calculations based on the broken symmetry approach reproduce the magnetic properties of 5 very well (calculated values: J(a) = -39.4 and J(b) = -55.9 cm(-1)), thus confirming the capability of this quantum chemical method for predicting the magnetic behavior of clusters involving more than two metal ions. The nature of the ground spin state of the magnetic {Mn(IV)(3)O(4)}(4+) core and the role of ancillary ligands on the magnitude of J are also discussed.
三核氧桥联锰簇Mn(IV)(3)O(4)(terpy)(terpyO(2))(2)(H(2)O)(2) (5) (terpy = 2,2':2'',6'-三联吡啶和 terpyO(2) = 2,2':2'',6'-三联吡啶 1,1''-二氧化物)，在酸性水溶液中从 MnSO(4)、terpy 和 Oxone 作为化学氧化剂的反应中分离得到。在合成过程中，terpyO(2)配体通过部分氧化原位生成。该配合物结晶于单斜晶系 P21/n 空间群，a = 14.251(5)A, b = 15.245(5)A, c = 24.672(5)A, alpha = 90.000(5)°，beta = 92.045(5)°，gamma = 90.000(5)°，Z = 4。在这个配合物中观察到的三角形{Mn(IV)(3)O(4)}(4+)核心是由一个基底 Mn(mu-O)(2)Mn 单元组成的，其中每个 Mn 离子通过单(mu-O)桥与一个顶端 Mn 离子相连。两个三角吡啶基 terpyO(2)配体与 Mn(mu-O)(2)Mn 单元的面配位允许形成三角形核心。5 也是第一个结构上被表征的具有多吡啶基 N-氧化物配体的 Mn 配合物。该配合物在 10-300 K 范围内的变温磁化率数据与 S = 1/2 基态一致，并使用自旋哈密顿 H(eff)进行拟合，其中 S(1) = S(2) = S(3) = 3/2，J(a) = -37(+/-0.5)和 J(b) = -53(+/-1)cm(-1)，其中 J(a)和 J(b)分别是通过单 mu-氧和双 mu-氧桥的交换常数。5 的二重基自旋态通过电子顺磁共振光谱测量得到证实。基于破缺对称方法的密度泛函理论(DFT)计算很好地再现了 5 的磁性性质(计算值：J(a) = -39.4 和 J(b) = -55.9cm(-1))，从而证实了这种量子化学方法预测涉及两个以上金属离子的簇磁性行为的能力。磁性{Mn(IV)(3)O(4)}(4+)核心基态自旋的性质和辅助配体对 J 值大小的影响也进行了讨论。
