Weak M(II)-Azide-4,4‘-Bipy Ferromagnets Based on Unusual Diamondoid (M = Mn) and 2D Arrays (M = Co, Ni)

Four compounds of general formula [M(4,4‘bipy)(N3)2]n (M = Mn (1), Zn (2), Co (3), Ni (4)) have been synthesized
and magnetostructurally characterized by means of X-ray diffraction analysis, IR and ESR spectroscopies, and
measurements of the magnetic susceptibility and magnetization. Compound 1 (C10H8N8Mn) crystallizes in the
tetragonal P43212 space group, Z = 4, with a = 8.229(2), b = 8.229(2), and c = 16.915(2) Å. It exhibits an
acentric 3D structure where Mn(II) ions are linked through EE-azide groups resulting in a diamondoid network.
The 4,4‘bipy ligands are coordinated on the axial positions of the octahedral spheres reinforcing the intermetallic
connections. Weak ferromagnetism arising from spin canting is observed for compound 1. Compounds 2, 3, and
4 are proposed to be isomorphous and would consist of a 2D array where alternating EO + EE/EO + EE/EO +
EO azide-chains are linked by 4,4‘bipy ligands resulting in π−π stacked pyridyl-columns. The azido ligand
dispositions in compounds 3 and 4 make possible systems of type −AF−AF−F−, which would give rise to a
topological ferromagnetic behavior.

本研究合成了通式为[M(4,4'-联吡啶(4,4'-bipyridine, 4,4'bipy))(叠氮根(N3))₂]ₙ的四种配合物，其中金属中心M分别为Mn(1)、Zn(2)、Co(3)和Ni(4)。通过X射线衍射分析（X-ray diffraction analysis）、红外光谱（IR）与电子顺磁共振光谱（ESR）表征，以及磁化率（magnetic susceptibility）和磁化强度（magnetization）测量，完成了这四种配合物的磁结构表征。配合物1（化学式为C₁₀H₈N₈Mn）结晶于四方晶系P43212空间群（tetragonal P43212 space group），晶胞参数Z=4，轴长参数为a=8.229(2)、b=8.229(2)、c=16.915(2) Å。该配合物具有非中心对称三维结构，二价锰离子(Mn(II))通过端基桥联(EE, end-to-end)叠氮根连接形成金刚石型网络(diamondoid network)；4,4'-联吡啶配体配位于八面体配位场（octahedral coordination spheres）的轴向位置，强化了金属离子间的桥联作用。配合物1表现出由自旋倾斜(spin canting)引发的弱铁磁性(weak ferromagnetism)。研究认为配合物2、3、4为同构体（isomorphous），其结构为二维阵列(2D array)：交替的EO+EE/EO+EE/EO+EO型叠氮根链通过4,4'-联吡啶配体相互连接，形成π-π堆叠(π−π stacked)的吡啶柱(pyridyl-columns)结构。配合物3和4中的叠氮根配位模式可形成−AF−AF−F−型磁耦合系统，该系统将呈现拓扑铁磁行为。