TOWARD LIGAND-DRIVEN LIGHT-INDUCED SPIN CHANGE - INFLUENCE OF THE CONFIGURATION OF 4-STYRYLPYRIDINE (STPY) ON THE MAGNETIC-PROPERTIES OF FEII(STPY)4(NCS)2 COMPLEXES - CRYSTAL-STRUCTURES OF THE SPIN-CROSSOVER SPECIES FE(TRANS-STPY)4(NCS)2 AND OF THE HIGH-SPIN SPECIES FE(CIS-STPY)4(NCS)2
TOWARD LIGAND-DRIVEN LIGHT-INDUCED SPIN CHANGE - INFLUENCE OF THE CONFIGURATION OF 4-STYRYLPYRIDINE (STPY) ON THE MAGNETIC-PROPERTIES OF FEII(STPY)4(NCS)2 COMPLEXES - CRYSTAL-STRUCTURES OF THE SPIN-CROSSOVER SPECIES FE(TRANS-STPY)4(NCS)2 AND OF THE HIGH-SPIN SPECIES FE(CIS-STPY)4(NCS)2
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DOI：
10.1021/ic00088a033
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发表时间：
1994-05-11
影响因子：
4.6
通讯作者：
CLAUDE, R
中科院分区：
文献类型：
--
作者：
ROUX, C;ZAREMBOWITCH, J;CLAUDE, R
介绍了一种在过渡金属分子化合物中获得配体驱动的光致自旋变化（LD-LISC）的方法。它基于能够被光化学修饰的配体的利用，例如顺-反光异构化配体。在配体光异构化后观察到的自旋转换的先决条件是与配体异构体形成的两个络合物中的至少一个呈现热诱导的自旋交叉。本文报道了两个FeL_4（NCS）_2型配合物，其中L = trans-stpy（配合物1）和L = cis-stpy（配合物2），stpy代表4-苯乙烯基吡啶。描述了它们的合成。测定了它们的X射线衍射结构。1的晶体属于正交晶系空间群Pna 2（1），Z = 4，a = 32.004（26）埃，B = 15.394（13）埃，c = 9.842（10）埃。2以单斜空间群P2（1）/n结晶，Z = 2，a = 13.115（2）埃，B = 12.569（3）埃，c = 14.574（3）埃，β = 91.90（1）度。在这两种配合物中，配位核具有相同的几何形状，NCS-基团处于反式位置。变温磁化率测量表明，1呈现S = 2 S = 0交叉，中心在108 K附近，而2保持高自旋状态低至4.2 K。因此，这对化合物确实满足观察到LD-LISC效应的自旋状态条件。然而，实验可能进行的最高温度约为90 K。为了使配体光异构化以合适的量子产率发生，现在必须通过化学改性络合物来提高该温度。
A method to obtain ligand-driven light-induced spin changes (LD-LISC) in transition-metal molecular compounds is described. It is based on the utilization of ligands capable of being photochemically modified, such as cis-trans photoisomerizable ligands. A prerequisite for the spin conversion to be observed upon ligand photoisomerization is that one at least of the two complexes formed with ligand isomers presents a thermally-induced spin crossover. Two complexes of the type FeL4(NCS)2 with L = trans-stpy (complex 1) and L = cis-stpy (complex 2), stpy standing for 4-styrylpyridine, are presented. Their syntheses are described. Their X-ray diffraction structures were determined. 1 crystallizes in the orthorhombic space group Pna2(1), with Z = 4, a = 32.004(26) angstrom, b = 15.394(13) angstrom, and c = 9.842(10) angstrom. 2 crystallizes in the monoclinic space group P2(1)/n, with Z = 2, a = 13.115(2) angstrom, b = 12.569(3) angstrom, c = 14.574(3) angstrom, and beta = 91.90(1)-degrees. In both complexes, the coordination core has the same geometry, with the NCS- groups in the trans position. Variable-temperature magnetic susceptibility measurements show that 1 presents a S = 2 S = 0 crossover, centered around 108 K, whereas 2 retains the high-spin state down to 4.2 K. So, this pair of compounds do fulfill the spin-state conditions for the LD-LISC effect to be observed. However, the highest temperature at which the experiment might be carried out is about 90 K. For ligand photoisomerization to occur with suitable quantum yields, this temperature has now to be increased by modifying the complexes chemically.