How magnetic interaction between two distant paramagnetic metals is influenced by central diamagnetic cyanidometal?
Magnetism is an ancient and classic physical phenomenon and will be forever interesting topics. Molecule-based magnetic materials, in which the structural building blocks are molecular in nature, are of increasing interest because they provide fundamental insight into magnetic phenomena and are potential in applications such as molecular switches, high-density information storage and quantum computation and so on. As important molecule-based magnetic materials, cyanide-bridged complexes have been obtained extensive attention due to their variable molecular structures and interesting magnetic coupling between paramagnetic metal centers through the cyanide bridge, such as photomagnetic materials, high Tc magnets, single-molecule magnets, single-chain magnets, and spin crossover materials.
Generally, magnetic coupling between two paramagnetic metal centers directly bridged by the CN– ions, namely Mp-C≡N-Mp (Mp = paramagnetic metal ion), is strong. In contrast, cyanide-bridged complexes in which paramagnetic metal centers are separated by a diamagnetic cyanidometal bridge, namely Mp-N≡C-Md-C≡N-Mp (Md = diamagnetic metal ion, Mp = paramagnetic metal ion), exhibit only very weak and even disappeared magnetic coupling. Therefore, the preparation of such compounds with a strong magnetic coupling is still a great challenge in this field. We are interested in investigating the distant magnetic coupling across a diamagnetic cyanidometal bridge, because we believe that spin delocalization along Mp-N≡C-Md-C≡N-Mp may increase magnetic coupling. Recently, we have synthesized a series of cyanide-bridged complexes with diamagnetic building blocks, some of which exhibit strong magnetic coupling. For example, the magnetic exchange constant J of the two distant FeIII centers in compound [Cp(dppe)FeIII(NC)MII(bpy)2(CN)FeIII(dppe)Cp][PF6]4 1 (bpy = 2, 2’- bipyridine, dppe = bis(diphenylphosphino)ethane, Cp = cyclopentadienide anion) is high up to -13.6 cm-1 even though separated by the diamagnetic cyanidometal NC-RuII-CN bridge. It should be mentioned that J is positive for ferromagnetic coupling and negative for antiferromagnetic coupling. And, the stronger the magnetic coupling is, the greater the︱J︱value is. The theoretical investigation has shown that the spin delocalization mechanism should be responsible for the strong magnetic coupling. Furthermore, one would like to know how the magnetic coupling between the distant FeIII ions is influenced by the central diamagnetic cyanidometal bridge. To understand this, the isostructural compounds [Cp(dppe)FeIII(NC)MII(bpy)2(CN)FeIII(dppe)Cp][PF6]4 (M = Os 2, Fe 3) have been synthesized and characterized, their magnetic properties have also been investigated. The molecular structures of compounds 1-3 are shown in Figure 1.
The experimental results show that compound 2 exhibit a strong antiferromagnetic coupling between the two distant FeIII ions although separated by the diamagnetic cyanidometal NC-OsII(bpy)2-CN bridge ( J = -25.8 cm-1). To the best of our knowledge, this is the strongest magnetic coupling between the distant paramagnetic metal ions across a diamagnetic cyanidometal bridge reported by far. For compound 3 with the diamagnetic cyanidometal NC-FeII(bpy)2-CN bridge, however, the distant two FeIII ions posses only very weak antiferromagnetic coupling (J = -0.15 cm-1). The magnetic susceptibilities studies indicate the magnetic coupling strength between the distant paramagnetic FeIII ions across diamagnetic cyanidometal NC-MII-CN (M = Fe, Ru, Os) bridge increases with the central metal in the order of Fe < Ru < Os, as shown in Figure 2. Most importantly, this work reveals that for the investigated system the distant magnetic interaction strength is directly associated with the degree of electron density delocalization over the cyanide groups in the central diamagnetic cyanidometal.
State Key Laboratory of Structural Chemistry
Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences
Influence of the central diamagnetic cyanidometal on the distant magnetic interaction in cyanide-bridged Fe(III)-M(II)-Fe(III) complexes.
Wang Y, Lin C, Ma X, Xue Z, Zhu X, Cao W, Hu S, Sheng T, Wu X.
Dalton Trans. 2015 Apr 28
|Short hydrogen bonds in proteins and their quantum… The assembly of linear polypeptide chains into functional three-dimensional protein architectures involves a unique force called hydrogen bonding. A typical hydrogen bond forms when the donor and acceptor groups approach…|
|Soil and water bioengineering – Sustainable erosion… Accelerated soil erosion and loss is a serious environmental problem, particularly for the Mediterranean region, due to its long history of human pressures, seasonally contrasting climate and rugged topography. Anthropogenic…|
|The complex regulation and functional significance… Across animals, variation in body size is often influenced by environmental conditions and is considered to have adaptive value. In bees, in which many species show various degrees of sociality,…|
|Magnetic chitosan hydrogel: a good choice for… Hydrogels as three-dimensional polymeric networks have been of longstanding interest due to their biocompatibility, hydrophilic nature, desired functionality, high elasticity, and superb capacities for retaining large amount of water and…|
|Ultralong room-temperature phosphorescence of a… Glows in the dark after removing energy input, named room-temperature phosphorescence (RTP), has got enormous attention because of its various application in biological imaging, light-emitting devices, information storage and encryption,…|
|WRGSD: improving reliability and efficiency for… Water-quality response grid-based sampling design (WRGSD) using optimization and multi-factors assessment can reliably detect a variety of the impact of human activities. The sampling design are optimized by clustering and…|