Synthesis and Properties of Photomagnetic Molecular Switches based on Spin Crossover Iron(II) Complexes Featuring Photoisomerizable Ligands

自旋交叉（SCO）金属配合物是最著名的一类分子双稳态系统，其磁性可以通过改变温度、施加压力、电场和磁场或光照射可逆地切换。最常见的SCO种类是铁（II）配合物，它提供了一个绝佳的机会，通过外部刺激在抗磁性低自旋和顺磁性高自旋状态之间切换。通过光照射来控制分子状态是非常有吸引力的，因为它具有非常高的开关速度、简单精确的寻址和高选择性，这表明SCO配合物作为分子电子学和自旋电子学、通信网络、超高密度存储器等的光开关构建块的应用。最近，我们开发了一种独特的分子开关1 - SCO铁（II）配合物，该配合物具有光活性二乙烯基衍生配体L.将光异构配体L整合到SCO物种1中，使我们能够在室温（RT）下以中等效率和光可逆地切换磁性。在本工作中，我们将化学修饰配体L并合成相应的SCO铁（II）配合物。所提出的L的化学修饰追求以下目标：1)在1的基础上改善分子开关的光物理性质，2)增加开关的热稳定性，3)增加RT下的光磁效应，4)允许分子开关接枝到金表面。因此，基于母体配合物1的整个分子开关家族将被合成，并将在溶液和固体状态下研究它们的光磁性。将进行分子开关接枝到金表面的初步实验和表面光磁性的研究。本项目的研究结果为薄膜分子和单分子在室温下的磁性转换提供了一个有效和可逆的机会，可以在室温下的分子电子学和自旋电子学中找到不同的应用。

Spin crossover (SCO) metal complexes are among the best known classes of molecular bistable systems which magnetic properties can be reversibly switched by changing temperature, applied pressure, electric and magnetic field, or irradiation with light. The most common SCO species are iron(II) complexes that offer a brilliant opportunity to switch between a diamagnetic low-spin and paramagnetic high-spin states via external stimuli. Controlling a molecule's state via light irradiation is very attractive due to the extraordinary high speed of switching, easy and precise addressing and high selectivity that suggests application of SCO complexes as photoswitchable building blocks for molecular electronics and spintronics, communication networks, ultra-high density memories, and others. Recently we developed a unique molecular switch 1 - a SCO iron(II) complex featuring a photoactive diarylethene derived ligand L. The integration of the photoisomerizable ligand L into the SCO species 1 allowed us to switch reversibly magnetic properties with moderate efficiency with light at room temperature (RT). In the present work we will chemically modify the ligand L and synthesize corresponding SCO iron(II) complexes. The proposed chemical modifications of L pursue the following goals: 1) to improve the photophysical properties of molecular switches based on 1, 2) to increase the thermal stability of the switches, 3) to increase a photomagnetic effect at RT, 4) to allow the grafting of molecular switches to the gold surface. Thus, a whole family of molecular switches based on the parent complex 1 will be synthesized and their photomagnetic properties will be investigated in solution and in the solid state. Initial experiments on grafting of molecular switches to the gold surface and investigation of their photomagnetic properties at the surface will be performed. The results obtained on this project may open a great opportunity to switch efficiently and reversibly magnetic properties of molecules in thin films and single molecules with light at RT that could find diverse applications in molecular electronics and spintronics at RT.