Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong, China.
Chemistry. 2010 Mar 15;16(11):3524-35. doi: 10.1002/chem.200902047.
Four cyano-bridged 1D bimetallic polymers have been prepared by using the paramagnetic building block trans-Ru(acac)(2)(CN)(2) (Hacac=acetylacetone): {[{Ni(tren)}{Ru(acac)(2)(CN)(2)}][ClO(4)].CH(3)OH}(n) (1) (tren=tris(2-aminoethyl)amine), {[{Ni(cyclen)}{Ru(acac)(2)(CN)(2)}][ClO(4)].CH(3)OH}(n) (2) (cyclen=1,4,7,10-tetraazacyclododecane), {[{Fe(salen)}{Ru(acac)(2)(CN)(2)}]}(n) (3) (salen(2-)=N,N'-bis(salicylidene)-o-ethyldiamine dianion) and [{Mn(5,5'-Me(2)salen)}(2){Ru(acac)(2)(CN)(2)}][Ru(acac)(2)(CN)(2)].2CH(3)OH (4) (5,5'-Me(2)salen=N,N'-bis(5,5'-dimethylsalicylidene)-o-ethylenediimine). Compounds 1 and 2 are 1D, zigzagged NiRu chains that exhibit ferromagnetic coupling between Ni(II) and Ru(III) ions through cyano bridges with J=+1.92 cm(-1), zJ'=-1.37 cm(-1), g=2.20 for 1 and J=+0.85 cm(-1), zJ'=-0.16 cm(-1), g=2.24 for 2. Compound 3 has a 1D linear chain structure that exhibits intrachain ferromagnetic coupling (J=+0.62 cm(-1), zJ'=-0.09 cm(-1), g=2.08), but antiferromagnetic coupling occurs between FeRu chains, leading to metamagnetic behavior with T(N)=2.6 K. In compound 4, two Mn(III) ions are coordinated to trans-Ru(acac)(2)(CN)(2) to form trinuclear Mn(2)Ru units, which are linked together by pi-pi stacking and weak Mn...O* interactions to form a 1D chain. Compound 4 shows slow magnetic relaxation below 3.0 K with phi=0.25, characteristic of superparamagnetic behavior. The Mn(III)...Ru(III) coupling constant (through cyano bridges) and the Mn(III)...Mn(III) coupling constant (between the trimers) are +0.87 and +0.24 cm(-1), respectively. Compound 4 is a novel single-chain magnet built from Mn(2)Ru trimers through noncovalent interactions. Density functional theory (DFT) combined with the broken symmetry state method was used to calculate the molecular magnetic orbitals and the magnetic exchange interactions between Ru(III) and M (M=Ni(II), Fe(III), and Mn(III)) ions. To explain the somewhat unexpected ferromagnetic coupling between low-spin Ru(III) and high-spin Fe(III) and Mn(III) ions in compounds 3 and 4, respectively, it is proposed that apart from the relative symmetries, the relative energies of the magnetic orbitals may also be important in determining the overall magnetic coupling in these bimetallic assemblies.
四种氰桥联的 1D 双金属聚合物已通过使用顺式-[Ru(acac)(2)(CN)(2)]-（Hacac=乙酰丙酮）作为磁性构建块来制备：{[{Ni(tren)}{Ru(acac)(2)(CN)(2)}][ClO4]·CH3OH}(n) (1) (tren=三(2-氨基乙基)胺)、{[{Ni(cyclen)}{Ru(acac)(2)(CN)(2)}][ClO4]·CH3OH}(n) (2) (cyclen=1,4,7,10-四氮杂环十二烷)、{[{Fe(salen)}{Ru(acac)(2)(CN)(2)}]}(n) (3) (salen(2-)=N,N'-双(水杨醛基)-o-乙二胺二阴离子)和[{Mn(5,5'-Me2salen)}(2){Ru(acac)(2)(CN)(2)}][Ru(acac)(2)(CN)(2)]·2CH3OH (4) (5,5'-Me2salen=N,N'-双(5,5'-二甲基水杨醛基)-o-乙二亚胺)。化合物 1 和 2 是 1D 的交错 NiRu 链，通过氰桥在 Ni(II)和 Ru(III)离子之间表现出铁磁耦合，J=+1.92 cm-1，zJ'=-1.37 cm-1，g=2.20 对于 1 和 J=+0.85 cm-1，zJ'=-0.16 cm-1，g=2.24 对于 2。化合物 3 具有 1D 线性链结构，表现出链内铁磁耦合（J=+0.62 cm-1，zJ'=-0.09 cm-1，g=2.08），但 FeRu 链之间发生反铁磁耦合，导致具有 T(N)=2.6 K 的 metamagnetic 行为。在化合物 4 中，两个 Mn(III)离子与顺式-[Ru(acac)(2)(CN)(2)]-配位形成三核 Mn(2)Ru 单元，这些单元通过π-π堆积和弱 Mn...O*相互作用连接在一起，形成 1D 链。化合物 4 在 3.0 K 以下表现出缓慢的磁弛豫，phi=0.25，表现出超顺磁行为。Mn(III)...Ru(III) 耦合常数（通过氰桥）和 Mn(III)...Mn(III) 耦合常数（在三聚体之间）分别为+0.87 和+0.24 cm-1。化合物 4 是一种通过非共价相互作用构建的新型单链磁体，由 Mn(2)Ru 三聚体组成。密度泛函理论（DFT）与破对称态方法相结合，用于计算分子磁轨道和 Ru(III)与 M（M=Ni(II)、Fe(III)和 Mn(III)）离子之间的磁交换相互作用。为了解释化合物 3 和 4 中分别为低自旋 Ru(III)和高自旋 Fe(III)和 Mn(III)离子之间有些出人意料的铁磁耦合，提出除了相对对称性外，磁轨道的相对能量也可能在确定这些双金属组装体中的整体磁耦合中很重要。
