Monakhov Kirill Yu, López Xavier, Speldrich Manfred, van Leusen Jan, Kögerler Paul, Braunstein Pierre, Poblet Josep M
Institut für Anorganische Chemie, RWTH Aachen University, Landoltweg 1, 52074 Aachen (Germany); Laboratoire de Chimie de Coordination, Institut de Chimie (UMR 7177 CNRS), Université de Strasbourg, 4 rue Blaise Pascal, 67081 Strasbourg Cedex (France).
Chemistry. 2014 Mar 24;20(13):3769-81. doi: 10.1002/chem.201304177. Epub 2014 Feb 24.
The scaffold geometries, stability and magnetic features of the (pyridine-2-yl)methanolate (L) supported wheel-shaped transition-metal complexes with compositions [M6L12] (1), Na⊂(ML2)6 (2), and M'⊂(ML2)6 (3), in which M=Co(II), Ni(II), Cu(II), and Zn(II) were investigated with density functional theory (DFT). The goals of this study are manifold: 1) To advance understanding of the magnetism in the synthesized compounds Na⊂(ML2)6 and M'⊂(ML2)6 that were described in Angew. Chem. Int. Ed.- 2010, 49, 4443 (I-{Na⊂Ni6}, I-{Ni'⊂Ni6}) and Dalton Trans.- 2011, 40, 10526 (II-{Na⊂Co6}, II-{Co'⊂Co6}); 2) To disclose how the structural, electronic, and magnetic characteristics of 1, 2, and 3 change upon varying M(II) from d(7) (Co(2+)) to d(10) (Zn(2+)); 3) To estimate the influence of the Na(+) and M'(2+) ions (X(Q+)) occupying the central voids of 2 and 3 on the external and internal magnetic coupling interactions in these spin structures; 4) To assess the relative structural and electrochemical stabilities of 1, 2, and 3. In particular, we focus here on the net spin polarization, the determination of the strength and the sign of the exchange coupling energies, the rationalization of the nature of the magnetic coupling, and the ground-state structures of 1, 2, and 3. Our study combines the broken symmetry DFT approach and the model Hamiltonian methodology implemented in the computational framework CONDON 2.0 for the modeling of molecular spin structures, to interpret magnetic susceptibility measurements of I-{Na⊂Ni6} and I-{Ni'⊂Ni6}. We illustrate that whereas the structures, stability and magnetism of 1, 2, and 3 are indeed influenced by the nature of 3d transition-metals in the {M6} rims, the X(Q+) ions in the inner cavities of 2 and 3 impact these properties to an even larger degree. As exemplified by I-{Ni'⊂Ni6}, such heptanuclear complexes exhibit ground-state multiplets that cannot be described by simplistic model of spin-up and spin-down metal centers. Furthermore, we assess how future low-temperature susceptibility measurements at high magnetic fields can augment the investigation of compound 3 with M=Co, Ni.
采用密度泛函理论（DFT）研究了组成分别为[M₆L₁₂]（1）、Na⊂(ML₂)₆（2）和M'⊂(ML₂)₆（3）的（吡啶 - 2 - 基）甲醇盐（L）支撑的轮状过渡金属配合物的支架几何结构、稳定性和磁性特征，其中M = Co(II)、Ni(II)、Cu(II)和Zn(II)。本研究的目标是多方面的：1）增进对《德国应用化学》 - 2010年，49卷，4443页（I - {Na⊂Ni₆}，I - {Ni'⊂Ni₆}）和《道尔顿汇刊》 - 2011年，40卷，10526页（II - {Na⊂Co₆}，II - {Co'⊂Co₆}）中所描述的合成化合物Na⊂(ML₂)₆和M'⊂(ML₂)₆中磁性的理解；2）揭示当M(II)从d⁷（Co²⁺）变化到d¹⁰（Zn²⁺）时，1、2和3的结构、电子和磁性特征如何变化；3）估计占据2和3中心空位的Na⁺和M'(²⁺)离子（X(Q⁺)）对这些自旋结构中外部和内部磁耦合相互作用的影响；4）评估1、2和3的相对结构和电化学稳定性。特别地，我们在此关注净自旋极化、交换耦合能强度和符号的确定、磁耦合性质的合理化以及1、2和3的基态结构。我们的研究结合了破缺对称性DFT方法和在计算框架CONDON 2.0中实现的模型哈密顿方法来模拟分子自旋结构，以解释I - {Na⊂Ni₆}和I - {Ni'⊂Ni₆}的磁化率测量结果。我们表明，虽然1、2和3的结构、稳定性和磁性确实受到{M₆}边缘3d过渡金属性质的影响，但由于2和3内腔中的X(Q⁺)离子，这些性质受到的影响更大。以I - {Ni'⊂Ni₆}为例，这种七核配合物表现出的基态多重态无法用简单的自旋向上和自旋向下金属中心模型来描述。此外，我们评估了未来在高磁场下进行的低温磁化率测量如何能加强对M = Co、Ni的化合物3的研究。
