Photo-Induced Spin Transition of Iron(III) Compounds with π-π Intermolecular Interactions
Photo-Induced Spin Transition of Iron(III) Compounds with π-π Intermolecular Interactions
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DOI：
10.1002/chem.200802395
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发表时间：
2009-01-01
影响因子：
4.3
通讯作者：
Sato, Osamu
中科院分区：
文献类型：
--
作者：
Hayami, Shinya;Hiki, Kenji;Sato, Osamu
铁（III）自旋交叉化合物[Fe（pap）（2）] ClO 4（1）、[Fe（pap）（2）] BF 4（2）、[Fe（pap）（2）] PF 6（3）、[Fe（qsal）（2）]NCS（4），和[Fe（qsal）（2）]NCSe（5）（Hpap=2-（2-吡啶基亚甲基氨基）苯酚和Hqsal=2-[（8-喹啉基亚氨基）甲基]苯酚），并通过磁化率和穆斯堡尔谱研究了它们的自旋跃迁性质。铁（III）化合物表现出自旋转变与热滞后。单晶的铁（III）化合物作为合适的溶剂加合物的X-射线分析，并在高自旋（HS）和低自旋（LS）状态的结构被揭示。铁（III）化合物的光诱导激发自旋态捕获（LIESST）效应通过在532 nm下对1-3进行光照射以及在800 nm下对4和5进行光照射来诱导。通过HS -> LS弛豫实验，估计铁（III）LIESST化合物1的活化能E-a和低温隧穿速率k（HL）（T -> 0）分别为1079 cm（-1）和2.4 × 10（-8）s（-1）。还估计黄-里斯因子S为1，为50，这与铁（II）络合物的预期相似。据认为，铁（III）系统中的缓慢弛豫是通过HS和LS状态之间的大的结构畸变实现的。引入强分子间相互作用，如π-π堆积，也可以在弛豫行为中发挥重要作用，因为它可以增强LIEST复合物的结构畸变。
Iron(III) spin-crossover compounds [Fe(pap)(2)]ClO4 (1), [Fe(pap)(2)]BF4 (2), [Fe(pap)(2)]PF6 (3), [Fe(qsal)(2)]NCS (4), and [Fe(qsal)(2)]NCSe (5) (Hpap=2-(2-pyridylmethyleneamino)phenol and Hqsal=2-[(8-quinolinylimino)methyl]phenol) were prepared and their spin-transition properties investigated by magnetic susceptibility and Mossbauer spectroscopy Measurements. The iron(III) compounds exhibited spin transition with thermal hysteresis. Single crystals of the iron(III) compounds were obtained as suitable solvent adducts for X-ray analysis, and structures in high-spin (HS) and low-spin (LS) states were revealed. Light-induced excited-spin-state trapping (LIESST) effects of the iron(III) compounds were induced by light irradiation at 532 nm for 1-3 and at 800 nm for 4 and 5. The activation energy E-a, and the low-temperature tunneling rate k(HL)(T -> 0) of iron(III) LIESST compound 1 were estimated to be 1079 cm(-1) and 2.4 x 10(-8) s(-1), respectively, by HS -> LS relaxation experiments. The Huang-Rhys factor S of 1 was also estimated to be 50, which was similar to that expected for iron(II) complexes. It is thought that the slow relaxation in iron(III) systems is achieved by the large structural distortion between HS and LS states. Introduction of strong intermolecular interactions, such as pi-pi stacking, can also play an important role in the relaxation behavior, because it can enhance the structural distortion of the LIESST complex.