Institut Parisien de Chimie Moléculaire, Université Pierre et Marie Curie-Paris 6, UMR 7201, F-75005, Paris, France.
Dalton Trans. 2010 May 28;39(20):4786-801. doi: 10.1039/b926709c.
Homo- and heterometallic octanuclear complexes of formula Na₂{[Cu₂(mpba)₃][Cu(Me₅dien)]₆}-(ClO₄)₆·12H₂O (1), Na₂{[Cu₂(Mempba)₃][Cu(Me₅dien)]₆}(ClO₄)₆·12H₂O (2), Na₂{[Ni₂(mpba)₃]-[Cu(Me₅dien)]₆}(ClO₄)₆·12H₂O (3), Na₂{[Ni₂(Mempba)₃][Cu(Me₅dien)]₆}(ClO₄)₆·9H₂O (4), {[Ni₂(mpba)₃][Ni(dipn)(H₂O)]₆}(ClO₄)₄·12.5H₂O (5), and {[Ni₂(Mempba)₃][Ni(dipn)-(H₂O)]₆}(ClO₄)₄·12H₂O (6) [mpba = 1,3-phenylenebis(oxamate), Mempba = 4-methyl-1,3-phenylenebis(oxamate), Me₅dien = N,N,N',N'',N''-pentamethyldiethylenetriamine, and dipn = dipropylenetriamine] have been synthesized through the "complex-as-ligand/complex-as-metal" strategy. Single-crystal X-ray diffraction analyses of 1, 3, and 5 show cationic M(II)₂M'(II)₆ entities (M, M' = Cu and Ni) with an overall double-star architecture, which is made up of two oxamato-bridged M(II)M'(II)₃ star units connected through three meta-phenylenediamidate bridges between the two central metal atoms leading to a binuclear metallacryptand core of the meso-helicate-type. Dc magnetic susceptibility data for 1-6 in the temperature range 2-300 K have been analyzed through a "dimer-of-tetramers" model [H = - J(S(1A)·S(3A) + S(1A)·S(4A) + S(1A)·S(5A) + S(2B)·S(6B) + S(2B)·S(7B) + S(2B)·S(8B)) - J'S(1A)·S(2B), with S(1A) = S(2B) = S(M) and S(3A) = S(4A) = S(5A) = S(6B) = S(7B) = S(8B) = S(M')]. The moderate to strong antiferromagnetic coupling between the M(II) and M'(II) ions through the oxamate bridge in 1-6 (-J(Cu-Cu) = 52.0-57.0 cm⁻¹, -J(Ni-Cu) = 39.1-44.7 cm⁻¹, and -J(Ni-Ni) = 26.3-26.6 cm⁻¹) leads to a non-compensation of the ground spin state for the tetranuclear M(II)M'(II)₃ star units [S(A) = S(B) = 3S(M') - S(M) = 1 (1 and 2), 1/2 (3 and 4), and 2 (5 and 6)]. Within the binuclear M(II)₂ meso-helicate cores of 1-4, a moderate to weak antiferromagnetic coupling between the M(II) ions (-J'(Cu-Cu) = 28.0-48.0 cm⁻¹ and -J'(Ni-Ni) = 0.16-0.97 cm⁻¹) is mediated by the triple m-phenylenediamidate bridge to give a ground spin singlet (S = S(A) - S(B) = 0) state for the octanuclear M(II)₂Cu(II)₆ molecule. Instead, a weak ferromagnetic coupling between the Ni(II) ions (J'(Ni-Ni) = 2.07-3.06 cm⁻¹) operates in the binuclear Ni(II)₂ meso-helicate core of 5 and 6 leading thus to a ground spin nonet (S = S(A) + S(B) = 4) state for the octanuclear Ni(II)₈ molecule. Dc magnetization data for 5 reveal a small but non-negligible axial magnetic anisotropy (D = -0.23 cm⁻¹) of the S = 4 Ni(II)₈ ground state with an estimated value of the energy barrier for magnetization reversal of 3.7 cm⁻¹ (U = -DS²). Ac magnetic susceptibility data for 5 show an unusual slow magnetic relaxation behaviour at low temperatures which is typical of "cluster glasses". The temperature dependence of the relaxation time for 5 has been interpreted on the basis of the Vogel-Fulcher law for weakly interacting clusters, with values of 2.5 K, 1.4 × 10⁻⁶ s, and 4.0 cm⁻¹ for the intermolecular interaction parameter (T₀), the pre-exponential factor (τ₀), and the effective energy barrier (U(eff)), respectively.
通过“配合物作为配体/配合物作为金属”策略合成的同核和异核八核配合物
我们通过“配合物作为配体/配合物作为金属”策略合成了具有化学式 Na₂{[Cu₂(mpba)₃][Cu(Me₅dien)]₆}-(ClO₄)₆·12H₂O（1）、Na₂{[Cu₂(Mempba)₃][Cu(Me₅dien)]₆}(ClO₄)₆·12H₂O（2）、Na₂{[Ni₂(mpba)₃]-[Cu(Me₅dien)]₆}(ClO₄)₆·12H₂O（3）、Na₂{[Ni₂(Mempba)₃][Cu(Me₅dien)]₆}(ClO₄)₆·9H₂O（4）、{[Ni₂(mpba)₃][Ni(dipn)(H₂O)]₆}(ClO₄)₄·12.5H₂O（5）和{[Ni₂(Mempba)₃][Ni(dipn)-(H₂O)]₆}(ClO₄)₄·12H₂O（6）的 Homo- 和 Heterometallic 八核配合物 [mpba = 1,3-亚苯基双（氧代乙酸），Mempba = 4-甲基-1,3-亚苯基双（氧代乙酸），Me₅dien = N,N,N',N'',N''-五甲基二乙三胺，dipn = 二丙三胺]。单晶 X 射线衍射分析表明 1、3 和 5 中的阳离子 M(II)₂M'(II)₆实体（M、M'=Cu 和 Ni）具有整体双星结构，由两个 oxamato-桥接的 M(II)M'(II)₃星单元组成，通过两个中心金属原子之间的三个 meta-苯二亚胺桥连接，形成介螺旋型的双核金属笼核。1-6 在 2-300 K 温度范围内的 dc 磁化率数据通过“二聚体-四聚体”模型进行了分析 [H = - J(S(1A)·S(3A) + S(1A)·S(4A) + S(1A)·S(5A) + S(2B)·S(6B) + S(2B)·S(7B) + S(2B)·S(8B)) - J'S(1A)·S(2B)，其中 S(1A) = S(2B) = S(M) 和 S(3A) = S(4A) = S(5A) = S(6B) = S(7B) = S(8B) = S(M')]。通过 oxamate 桥在 1-6 中在 M(II)和 M'(II)离子之间产生中等至强的反铁磁耦合（-J(Cu-Cu) = 52.0-57.0 cm⁻¹、-J(Ni-Cu) = 39.1-44.7 cm⁻¹ 和 -J(Ni-Ni) = 26.3-26.6 cm⁻¹）导致 tetranuclear M(II)M'(II)₃星单元的基态自旋非补偿 [S(A) = S(B) = 3S(M') - S(M) = 1（1 和 2）、1/2（3 和 4）和 2（5 和 6）]。在 1-4 的双核 M(II)₂介螺旋核中，M(II)离子之间的中等至弱反铁磁耦合（-J'(Cu-Cu) = 28.0-48.0 cm⁻¹ 和 -J'(Ni-Ni) = 0.16-0.97 cm⁻¹）通过三重 m-苯二亚胺桥进行介导，为八核 M(II)₂Cu(II)₆分子提供基态单重态（S = S(A) - S(B) = 0）状态。相反，在 5 和 6 的双核 Ni(II)₂介螺旋核中，Ni(II)离子之间的弱铁磁耦合（J'(Ni-Ni) = 2.07-3.06 cm⁻¹）起作用，从而为八核 Ni(II)₈分子提供基态非单重态（S = S(A) + S(B) = 4）状态。5 的 dc 磁化率数据显示 S = 4 Ni(II)₈基态具有微小但不可忽略的轴向各向异性（D = -0.23 cm⁻¹），估计磁反转的能垒为 3.7 cm⁻¹（U = -DS²）。5 的交流磁化率数据显示低温下存在异常缓慢的磁弛豫行为，这是“簇玻璃”的典型特征。根据弱相互作用簇的 Vogel-Fulcher 定律，解释了 5 的弛豫时间的温度依赖性，其中参数值为 2.5 K、1.4×10⁻⁶ s 和 4.0 cm⁻¹，分别为分子间相互作用参数（T₀）、前指数因子（τ₀）和有效能垒（U(eff)）。
