Towards control of the intrinsic characteristics of Spin-crossover in ferrous materials

自旋交叉配合物可以通过改变温度、施加压力或光照射在低自旋和高自旋状态之间切换。因此，这些复合物不仅在基础研究中具有很高的兴趣，而且在全息光学信息存储设备和显示设备中也是有前途的材料。图卢兹和l<e:1>贝克的研究团队的这个联合项目的目的是量化决定自旋交叉的重要参数的因素，如转变温度、热滞后或转变的特征（渐进或突然）。量化这些因素将是这些材料未来技术应用的重要前提。该项目将从图卢兹实验室已经提供的一组大型复合物的调查开始。这些样品包含给定的铁（II）配合物阳离子和许多不同的反阴离子，它们对材料的自旋交叉行为有相当大的影响。该项目将继续合成新的配合物，这将以现有样品的光谱实验和理论计算结果为指导。配合物的实验表征将使用几种互补技术进行，包括红外光谱、拉曼光谱和Mössbauer光谱、磁化率测量、核正向散射和核非弹性散射实验。理论表征将在密度泛函计算和ising模型模拟的帮助下进行。两个研究团队在自旋交叉领域都有长期的研究经验。两个实验室使用的实验和理论工具在很大程度上是互补的。两个研究小组对这些复合物的联合研究不仅会导致对研究对象的更完整的描述，而且对于合成，实验表征和理论计算之间的持续反馈至关重要。

Spin-crossover complexes can be switched between low-spin and high-spin states by changing temperature, applied pressure, or by irradiation with light. These complexes are therefore not only of high interest for basic research, they are also promising materials for holographic optical information storage devices and for display devices. The aim of this joint project between the research teams in Toulouse and in Lübeck is to quantify the factors that determine important parameters of the spin crossover like the transition temperature, the thermal hysteresis or the character of the transition (gradual or abrupt). Quantifying these factors will be an important prerequisite for future technical applications of these materials. This project will start with the investigation of a large set of complexes that are already available in the Toulouse laboratory. These samples consist in a given iron(II) complex cation and many different counteranions, which have a considerable influence on the spin-crossover behaviour of the material. The project will continue with the synthesis of new complexes, which will be guided by the results of spectroscopic experiments and theoretical calculations for the existing samples. The experimental characterization of the complexes will be carried out using several complementary techniques including IR, Raman and Mössbauer spectroscopy, susceptibility measurements, nuclear forward scattering and nuclear inelastic scattering experiments. The theoretical characterization will be performed with the help of density functional calculations and simulations with Ising-like models. Both research teams have long-standing experience in the field of spin-crossover research. The experimental and theoretical tools used in the two laboratories are complementary to a large extent. A combined investigation of these complexes by both research teams will not only lead to a more complete description of the subject under study, but is essential for a continuous feedback between synthesis, experimental characterization and theoretical calculations.