Departamento de Química Inorgánica, Facultad de Ciencias, Universidad de Granada, Av. Fuentenueva S/N, 18071 Granada, Spain.
Dalton Trans. 2012 Dec 21;41(47):14265-73. doi: 10.1039/c2dt31643a.
Four new dinuclear complexes [Ni(μ-L)(μ-OAc)Ni(H2O)2]NO3 (1), Ni(μ-L)(μ-OBz)Ni(H2O)(MeOH)]NO3·3MeOH (2), [Ni(μ-L)(μ-9-An)Ni(H2O)(MeOH)]NO3 (3) and [Ni(μ-L)(μ-OAc)Ni(H2O)(N3)]·CH3OH (4) have been prepared from the compartmental ligand N,N′,N′′-trimethyl-N,N′′-bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylenetriamine (H2L) and different carboxylate ligands (OBz = benzoate and 9-An = 9-anthracenecarboxylate), and then magnetically and structurally characterized. The X-ray structures of these complexes reveal that the Ni2+ ions are bridged by two phenoxo groups belonging to the L2− ligand and one syn–syn carboxylate group, giving rise to diphenoxocarboxylate triply bridged dinuclear nickel(II) complexes. The syn–syn carboxylate bridging group folds the structure with hinge angles (β) in the range 32–36°. The folding of the structure takes place with a concomitant decrease of the O–Ni–O bridging angle (θ) and an increase of the shift carbon atom directly linked to the phenoxo oxygen atom with respect to the Ni–Ni–O plane in the bridging region (τ angle). All the complexes exhibit ferromagnetic interactions between the slightly distorted octahedral Ni2+ ions. A comparative analysis of the magneto-structural data for 1–4 and other diphenoxocarboxylate bridged complexes clearly show that not only the θ angle, but also the τ and β angles play a significant role in determining the sign and magnitude of the magnetic exchange coupling in these complexes. The ferromagnetic behaviour observed for 1–4 has been justified on the basis of their relatively low θ and high β and τ values, all of them decreasing the antiferromagnetic contribution in complexes 1–4, as well as the countercomplementarity effects between the diphenoxo and carboxylate bridging ligands. DFT theoretical calculations unequivocally demonstrate that the countercomplementarity mechanism is operative in compounds 1–4.
四种新的双核配合物[Ni(μ-L)(μ-OAc)Ni(H2O)2]NO3(1)、[Ni(μ-L)(μ-OBz)Ni(H2O)(MeOH)]NO3·3MeOH(2)、[Ni(μ-L)(μ-9-An)Ni(H2O)(MeOH)]NO3(3)和[Ni(μ-L)(μ-OAc)Ni(H2O)(N3)]·CH3OH(4)已由分隔配体 N,N′,N′′-三甲基-N,N′′-双(2-羟基-3-甲氧基-5-甲基苄基)二乙三胺(H2L)和不同的羧酸盐配体(OBz=苯甲酸盐和 9-An=9-蒽甲酸盐)制备得到，然后对其进行了磁性和结构表征。这些配合物的 X 射线结构表明，Ni2+离子由两个属于 L2−配体的酚氧基和一个顺-顺羧酸盐基团桥接，形成了二苯并氧羧酸三桥双核镍(II)配合物。顺-顺羧酸盐桥接基团将结构折叠，铰链角(β)在 32-36°范围内。结构的折叠伴随着 O-Ni-O 桥接角(θ)的减小和与桥接区域中酚氧基氧原子直接相连的碳原子相对于 Ni-Ni-O 平面的位移(τ角)的增加。所有配合物都表现出轻微扭曲的八面体 Ni2+离子之间的铁磁相互作用。对 1-4 和其他二苯并氧羧酸桥接配合物的磁结构数据的比较分析清楚地表明，不仅θ角，而且 τ角和β角在确定这些配合物中磁交换耦合的符号和大小方面起着重要作用。1-4 中观察到的铁磁行为是基于它们相对较低的θ值和较高的β和τ值来解释的，所有这些值都降低了配合物 1-4 中的反铁磁贡献，以及二苯并氧和羧酸盐桥接配体之间的互补效应。DFT 理论计算明确证明，互补机制在化合物 1-4 中起作用。
