Mono-, di-, tri-, and tetranuclear compounds of nickel(II) of formula [Ni(dppn)₃](NCS)₂·0.5dppn (1), [{Ni(dppn)(NCS)}₂(μ-dppn)(μ-NCS)]NCS (2), [Ni₃(dppn)₂(N₃)₂(μ-dppn)₂(μ-N₃)₂](ClO₄)₂·CH₃CH₂OH·2H₂O (3), and [Ni₄(μ-dppn)₄(μ-N₃)₄]Cl₄·5H₂O (4) [dppn = 3,6-bis(2′-pyridyl)pyridazine] have been prepared and their structures determined by single crystal X-ray diffraction. Compound 1 is made up of mononuclear tris-chelated [Ni(dppn)₃]²⁺ units, thiocyanate counterions, and dppn molecules of crystallization. 2 contains cationic dinuclear units, the six coordination around each metal center being achieved with a pyridazine-dppn and one end-on thiocyanate nitrogen as bridges, a didentate dppn ligand and a terminally bound N-thiocyanate. The electroneutrality in 2 is reached by free thiocyanato anions. 3 contains bent trinuclear cationic units where all nickel(II) ions exhibit a NiN₆ chromophore with two bridging bis-didentate dppn and two end-on azide groups connecting the metal centers. Didentate dppn and monodentate azide ligands complete the six coordination at the peripheral nickel(II) ions. The charge in 3 is counterbalanced by perchlorate anions and ethanol and water molecules of crystallization are also present. 4 exhibits a [2 × 2] grid-type of nickel(II) ions where each pair of metal atoms are connected across a pyridazine-dppn fragment and one end-on azido group. Free chloride anions neutralize the positive charge of the grid and water molecules of crystallization are also present. Cryomagnetic susceptibility measurements on crushed crystals of 1–4, in the temperature range 1.9–300 K, reveal the occurrence of a Curie law for 1 and overall ferromagnetic behavior for 2–4 [J = +4.52(2) (2), +1.32(1) (3), and +10.50(2) and +9.10(2) cm^–1 (4)]. The dominant ferromagnetic contribution across the single end-on thiocyanato (2) or azido bridges (3 and 4) versus the antiferromagnetic one through the pyridazine (2–4) is at the origin of this behavior. The values of the intramolecular ferromagnetic interactions in 3 and 4 were substantiated by DFT-type calculations. No ac signals were observed for 2–4 either in the lack of or under nonzero applied dc fields.

中文翻译：

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从单核化合物到[2×2]金属对映体：由镍（II）和3,6-双（2'-吡啶基）哒嗪（dppn）构建的铁磁耦合系统

式[Ni（dppn）₃ ]（NCS）₂ ·0.5dppn（1），[{Ni（dppn）（NCS）} ₂（μ的镍（II）的单，二，三和四核化合物-dppn）（μ-NCS）] NCS（2），[倪₃（dppn）₂（N ₃）₂（μ-dppn）₂（μ-N ₃）₂ ]（CLO ₄）₂ ·CH ₃ CH ₂ OH·2H ₂ O（3）和[镍₄（μ-dppn）₄（μ-N ₃）₄ ]氯₄ ·5H ₂制备了O（4）[dppn = 3,6-双（2'-吡啶基）哒嗪]，并通过单晶X射线衍射确定了它们的结构。化合物1由单核三螯合的[Ni（dppn）₃ ] ²⁺单元，硫氰酸根抗衡离子和dppn结晶分子组成。2包含阳离子双核单元，每个金属中心周围的六个配位是通过哒嗪-dppn和一个末端硫氰酸酯氮作为桥，二齿dppn配体和末端结合的N-硫氰酸酯实现的。游离的硫氰酸根合阴离子达到2的电子中性。3包含弯曲的三核阳离子单元，其中所有镍（II）离子均显示NiN ₆发色团，带有两个桥接的双齿dppn和两个连接金属中心的端基叠氮化物基团。精确的dppn和单齿的叠氮化物配体完成了周围镍（II）离子的六配位作用。3中的电荷被高氯酸根阴离子抵消，乙醇和结晶水分子也存在。图4显示[2×2]网格型镍（II）离子，其中每对金属原子通过哒嗪-dppn片段和一个末端叠氮基连接。游离氯离子会中和栅极的正电荷，并且还会出现结晶水分子。压碎晶体的低温磁化率测量。1 - 4，在温度范围1.9-300 K，揭示了一个居里定律为发生1和整体铁磁行为2 - 4 [ Ĵ = 4.52（2）（2），1.32（1）（3） ，以及+10.50（2）和+9.10（2）cm ^–1（4）]。横跨单个主导铁磁贡献端上氰硫基（2）或叠氮基桥（3和4）相对于通过所述哒嗪（反铁磁性一个2 - 4）是在此行为的原点。分子内铁磁相互作用的值3和4通过DFT型计算得到证实。在没有或没有非零施加的直流场的情况下，没有观察到2 – 4的交流信号。