Spin Crossover in Fe(II)-M(II) Cyanoheterobimetallic Frameworks (M = Ni, Pd, Pt) with 2-Substituted Pyrazines
Spin Crossover in Fe(II)-M(II) Cyanoheterobimetallic Frameworks (M = Ni, Pd, Pt) with 2-Substituted Pyrazines
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DOI：
10.1021/acs.inorgchem.6b00446
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发表时间：
2016-05-16
影响因子：
4.6
通讯作者：
Gural'skiy, Il'ya A.
中科院分区：
文献类型：
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作者：
Kucheriv, Olesia I.;Shylin, Sergii I.;Gural'skiy, Il'ya A.
Fen基Hofmann包合物家族中自旋交叉（SCO）行为的发现引发了分子材料领域的“新热潮”。迄今为止，这类SCO配合物以几十种单独的化合物为代表，并且它们的潜在应用领域稳步增加。以Fe ~（2+）、四氰合物M-II（CN）（4）（2-）（Mn = Ni，Pd，Pt）和2-取代吡嗪Xpz（X = Cl，Me，I）为共配体，合成了9个新的Hofmann笼形配位结构。X-射线衍射表明，配合物中Fen离子为假八面体配位环境，由四个μ（4）-四氰尿酸盐支持，形成赤道配位环境。根据X和M的性质，轴向位置被两个2X-吡嗪占据（X = Cl，M-II = Ni（1），Pd（2），Pt（3）; X = Me和M-II = Ni（4）、Pd（5））或一个2X-吡嗪和一个水分子（X = I和M-II = Ni（7），Pd（8），Pt（9）），或者，可替代地，观察到具有两个吡嗪或两个水分子的两个不同的Fe-II位置（X = Me和M-II = Pt（6））。磁化率的温度行为表明，所有含FeN 6单元（1-6）的化合物都表现出协同自旋跃迁，而在N_5O或N_4O_2周围的Fe-II离子则表现为高自旋（HS）。在最近的Fen环境中，低自旋（LS）到HS转变时的结构变化，其中包括ca。10% Fe-N间距增加，导致晶胞膨胀。穆斯堡尔谱用于表征所有HS，LS和1-9的中间相的自旋状态（见摘要图）。吡嗪取代基和M-II性质的超精细参数在两个自旋状态的影响。
Discovery of spin-crossover (SCO) behavior in the family of Fen-based Hofmann clathrates has led to a "new rush" in the field of bistable molecular materials. To date this class of,SCO complexes is represented by several dozens of individual compounds, and areas of their potential application steadily increase. Starting from Fe2+, square planar tetracyanometalates M-II(CN)(4)(2-) (Mn = Ni, Pd, Pt) and 2-substituted pyrazines Xpz (X = Cl, Me, I) as coligands we obtained a series of nine new Hofmann clathrate-like coordination frameworks. X-ray diffraction reveals that in these complexes Fen ion has a pseudo-octahedral coordination environment supported by four mu(4)-tetracyanometallates forming its equatorial coordination environment. Depending on the nature of X and M, axial positions are occupied by two 2X-pyrazines (X = Cl and M-II = Ni (1), Pd (2), Pt (3); X = Me and M-II = Ni (4), Pd (5)) or one 2X-pyrazine and one water molecule (X = I and M-II = Ni (7), Pd (8), Pt (9)), or, alternatively, two distinct Fe-II positions with either two pyrazines or two water molecules (X = Me and M-II = Pt (6)) are observed. Temperature'behavior of magnetic susceptibility indicates that all compounds bearing FeN6 units (1-6) display cooperative spin transition, while Fe-II ions in N5O or N4O2 surrounding are high spin (HS). Structural changes in the nearest Fen environment upon low-spin (LS) to HS transition, which include ca. 10% Fe-N distance increase, lead to the cell expansion. Mossbauer spectroscopy is used to characterize the spin state of all HS, LS, and intermediate phases of 1-9 (see abstract figure). Effects of a pyrazine substituent and M-II nature on the hyperfine parameters in both spin states are established.