Yamashita Masahiro, Manabe Toshio, Inoue Kazuo, Kawashima Takuya, Okamoto Hiroshi, Kitagawa Hiroshi, Mitani Tadaoki, Toriumi Koshiro, Miyamae Hiroshi, Ikeda Ryuichi
Graduate School of Human Informatics and PRESTO (JST), Nagoya University, Chikusa-ku, Nagoya 464-8601, Japan, Department of Applied Physics, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan, Japan Advanced Institute for Science and Technology, Ishikawa 923-1292, Japan, Faculty of Science, Himeji Institute of Technology, Hyogo 678-12, Japan, Department of Chemistry, Jyosai University, Saitama 350-02, Japan, and Department of Chemistry, University of Tsukuba, Tsukuba 305-8571, Japan.
Inorg Chem. 1999 Apr 19;38(8):1894-1899. doi: 10.1021/ic9812499.
A series of quasi-one-dimensional halogen-bridged Ni(III) complexes, [Ni(chxn)(2)X]Y(2) (chxn = 1R,2R-diaminocyclohexane; X = Cl, Br, and mixed halides; Y = Cl, Br, mixed halides, NO(3), BF(4), and ClO(4)) have been synthesized in order to investigate the effect of the bridging halogens and counteranions on their crystal, electronic structures, and moreover the spin density wave strengths. In the crystal structures, the [Ni(chxn)(2)] moieties are symmetrically bridged by halogen ions, forming linear-chain Ni(III)-X-Ni(III) structures. The hydrogen bonds between the aminohydrogens of chxn and the counteranions are constructed not only along the chains but also over the chains, forming the two-dimensional hydrogen-bond networks. While the Ni(III)-X-Ni(III) distances or b axes are almost constant in the compounds with the same bridging halogens, the c axes which correspond to the interchain distances in the directions of the interchain hydrogen bonds are remarkably lengthened with the increase of the ionic radius of the counterions; X < NO(3) < BF(4) < ClO(4). These compounds show the very strong antiferromagnetic interactions among spins on Ni 3d(z)2 orbitals through the superexchange mechanisms via the bridging halogen ions. Judging from the results of X-ray photoelectron spectra (XPS), Auger spectra, and single-crystal reflectance spectra, these Ni compounds are not Mott-insulators but charge-transfer-insulators. Their electronic structures or the spin density wave strengths are found to be tuned by the combinations of the counteranions and the bridging halogens.
为了研究桥连卤素和抗衡阴离子对其晶体结构、电子结构以及自旋密度波强度的影响，合成了一系列准一维卤素桥连的Ni(III)配合物，即[Ni(chxn)(2)X]Y(2)（chxn = 1R,2R - 二氨基环己烷；X = Cl、Br及混合卤化物；Y = Cl、Br、混合卤化物、NO(3)、BF(4)和ClO(4)）。在晶体结构中，[Ni(chxn)(2)]部分由卤素离子对称桥连，形成线性链状的Ni(III)-X-Ni(III)结构。chxn的氨基氢与抗衡阴离子之间不仅沿着链而且跨链形成氢键，构成二维氢键网络。在具有相同桥连卤素的化合物中，Ni(III)-X-Ni(III)距离或b轴几乎恒定，但对应于链间氢键方向链间距离的c轴随着抗衡离子离子半径的增加而显著延长；X < NO(3) < BF(4) < ClO(4)。这些化合物通过桥连卤素离子的超交换机制在Ni 3d(z)2轨道上的自旋之间表现出非常强的反铁磁相互作用。从X射线光电子能谱（XPS）、俄歇能谱和单晶反射光谱的结果判断，这些Ni化合物不是莫特绝缘体而是电荷转移绝缘体。发现它们的电子结构或自旋密度波强度可通过抗衡阴离子和桥连卤素的组合来调节。
