Dynamical Spin Crossover Phenomenon in Organic-Inorganic Composite Complex and Its Development to Molecular System

对于自旋态位于自旋交叉区的混合价配合物，为了使整个体系的自由能最小化，预计相邻金属离子之间会发生自旋和电荷的协同作用.从这个观点出发，我们研究了（n-C_nH_&lt;2n+1&gt;）_4N[Fe^<II>Fe^<III>（dto）_3]（n=3-6，dto=C_2O_2S_2）的电荷转移相变，它是一种自旋和电荷耦合的共轭现象。当n =5和6时，在300 ~ 4K之间不发生电荷转移相变。为了揭示电荷转移相变的动力学，我们研究了n - 3和5的μ子自旋弛豫（μSR）。在n = 3的电荷转移相变温度范围内，在80 K附近观察到了具有热滞回线的μ子自旋动态退极化率的反常增强， ...更多信息 化率我们成功地把这种异常的起因归结为Fe ~（2+）与Fe ~（2+）之间的电子转移动力学过程<II><III>，并由LF-μSR估算出其频率约为0.1MHz量级。此外，为了利用光辐射调控dto桥联铁混合价体系的磁性和电子态，我们合成了一种光敏有机-无机杂化体系（SP）[Fe^<II>Fe^<III>（dto）_3]（SP = spiropyran），并通过测量磁化率、UV-vis和~ 1Fe穆斯堡尔谱研究了光诱导对磁性的影响<57>。紫外光照射使（SP）[Fe^ Fe^（dto）_3]中螺吡喃的结构由封闭型转变为开放型<II><III>，从而导致[Fe^ Fe^（dto）_3]的二维蜂窝状网络结构发生电荷转移相变<II><III>，并改变铁磁转变温度。少

In the case of mixed-valence complexes whose spin states are situated in the spin-crossover region, it is expected that a cooperative phenomenon coupled with spin and charge takes place between neighboring metal ions in order to minimize the free energy in the whole system. From this viewpoint, we have investigated the charge transfer phase transition, which is a conjugated phenomenon coupled with spin and charge, (n-C_nH_<2n+1>)_4N[Fe^<II>Fe^<III> (dto)_3] (n=3-6,dto=C_2O_2S_2). The charge transfer phase transition takes place for n = 3 and 4, while it does not take place between 300 K and 4 K for n=5 and 6. In order to reveal the dynamics of the charge transfer phase transition, we have investigated muon spin relaxation (μSR) for n - 3 and 5. In the temperature range of the charge transfer phase transition for n = 3, an anomalous enhancement of the dynamic muon-spin depolarization rate with thermal hysteresis loop was observed at around 80 K in the temperature dependence of the depol … More arization rate. The origin of this anomaly has been successfully assigned to the dynamic process of electron-transfer between Fe^<II> and Fe^<III> and its frequency has been estimated from LF-μSR to be about the order of 0.1 MHz. This result is the first observation of dynamical electron transfer process by μSR technique for such mixed valence complexes.Moreover, in order to control the magnetic properties and the electronic state in the dto-bridged iron mixed-valence system by means of photo-irradiation, we have synthesized a photo-sensitive organic-inorganic hybrid system, (SP)[Fe^<II>Fe^<III>(dto)_3] (SP = spiropyran), and investigated the photo-induced effect on the magnetic properties by the measurements of magnetic susceptibility, UV-vis and ^<57>Fe Mossbauer spectra. The UV irradiation changes the structure of spiropyran from the closed form to the open one in (SP)[Fe^<II>Fe^<III> (dto)_3], which induces the charge transfer phase transition in the two-dimensional honeycomb network structure of [Fe^<II>Fe^<III>(dto)_3]., and changes the ferromagnetic transition temperature. Less