Reaction of 3-(2-pyridyl)pyrazole (HL1) and 6-(3-pyrazolyl)-2,2′-bipyridine (HL2) with nickel(II) and zinc(II) salts afforded the simple mononuclear pseudo-octahedral complexes [M(HL1)3][PF6]2 and [M(HL2)2][PF6]2 respectively (M = Ni or Zn) in which the ligands co-ordinate as neutral mononucleating chelates in the same manner as e.g. 2,2′-bipyridine or 2,2′∶6′,2″-terpyridine respectively. However with CuII the complexes [Cu4(L1)6(solv)2][PF6]2 (solv = dmf or MeOH) and [Cu4(L2)4(dmf)4][PF6]4 were isolated and crystallographically characterised, in all cases containing four tetragonally elongated square-pyramidal copper(II) ions which are linked by pyrazolate bridges from the now deprotonated ligands L1 and L2. The approximate orthogonality of the different ligands within each complex and the approximately square array of metal ions result in a grid-like structure. In [Cu4(L1)6(solv)2][PF6]2 there are successively two, one, two and one pyrazolate bridges between adjacent copper(II) ions around the Cu4 square resulting in two clearly different magnetic coupling pathways; in [Cu4(L2)4(dmf)4][PF6]4 however, which has approximate S4 symmetry, each Cu· · ·Cu edge has a single pyrazolate bridge and the coupling pathways are all virtually equivalent. Prolonged drying of these compounds resulted in loss of the axial dmf ligands to give [Cu4(L1)6][PF6]2 and [Cu4(L2)4][PF6]4. Magnetic susceptibility studies on these showed the presence of two antiferromagnetic exchange pathways for [Cu4(L1)6][PF6]2 with J > 172 cm–1 and J′ < 155 cm–1 (strong correlation between the parameters precludes a more precise determination), but only one antiferromagnetic exchange pathway for [Cu4(L2)4][PF6]4 with J = 63.5 cm–1, consistent with the crystal structures of the dmf adducts. The EPR spectra of [Cu4(L1)6][PF6]2 and [Cu4(L2)4][PF6]4 at a variety of frequencies and temperatures can be well simulated as arising from triplet species; however the spectrum of [Cu4(L1)6][PF6]2 also contains a feature which may be ascribed to the expected thermally populated quintet state.
3-(2-
吡啶基)
吡唑 (HL1) 和 6-(3-
吡唑基)-
2,2'-联吡啶 (H
L2) 与
镍 (II) 和
锌 (II) 盐反应得到简单的单核假八面体配合物分别为 [M(HL1)3][PF6]2 和 [M(H
L2)2][PF6]2(M=Ni 或 Zn),其中
配体以中性单核螯合物的形式以与例如相同的方式配位。分别为2,2′-联
吡啶或2,2′∶6′,2″-三联
吡啶。然而,使用 CuII,复合物 [Cu4(L1)6(solv)2][PF6]2(solv = dmf 或 MeOH)和 [Cu4(
L2)4(dmf)4][PF6]4 被分离并进行晶体学表征,所有情况均含有四个四方拉长的方形锥体
铜 (II) 离子,这些离子通过来自现已去质子化的
配体 L1 和
L2 的
吡唑酯桥连接。每个配合物内不同
配体的近似正交性和
金属离子的近似方形阵列导致网格状结构。在 [Cu4(L1)6(solv)2][PF6]2 中,Cu4 方块周围的相邻
铜 (II) 离子之间依次存在两个、一个、两个和一个
吡唑盐桥,从而产生两个明显不同的磁耦合路径;然而,在具有近似 S4 对称性的 [Cu4(
L2)4(dmf)4][PF6]4 中,每个 Cu· ···Cu 边缘都有一个
吡唑桥,并且耦合路径实际上都是等效的。这些化合物的长时间干燥导致轴向 dmf
配体损失,得到 [Cu4(L1)6][PF6]2 和 [Cu4(
L2)4][PF6]4。对这些的磁化率研究表明 [Cu4(L1)6][PF6]2 存在两条反
铁磁交换路径,J > 172 cm–1 和 J' < 155 cm–1(参数之间的强相关性妨碍了更精确的计算)测定),但 [Cu4(L2)4][PF6]4 只有一种反铁磁交换途径,J = 63.5 cm–1,与 dmf 加合物的晶体结构一致。 [Cu4(L1)6][PF6]2 和 [Cu4(
L2)4][PF6]4 在不同频率和温度下的 EPR 光谱可以很好地模拟为三重态物种;然而,[Cu4(L1)6][PF6]2 的光谱还包含一个特征,该特征可能归因于预期的热填充五重态。