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

自旋交叉(SCO)金属络合物是一类最著名的分子双稳系统，它的磁性可以通过改变温度、外加压力、电场和磁场或光照射来可逆地切换。最常见的SCO物种是铁(II)络合物，它提供了通过外部刺激在抗磁低自旋态和顺磁高自旋态之间切换的绝佳机会。通过光照射来控制分子的状态是非常有吸引力的，因为它具有极高的开关速度、简单和精确的寻址以及高选择性，这表明SCO络合物可以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。最近，我们开发了一种独特的分子开关1-具有光活性的二芳基乙烯衍生配体L的SCO铁(II)配合物。将可光异构化的配体L整合到SCO物种1中，使我们能够在室温(RT)下用光(RT)以适度的效率实现可逆的磁性开关。在本工作中，我们将对配体L进行化学修饰，并合成相应的SCO铁(II)配合物。L提出的化学修饰的目标如下：1)基于1)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时的光磁效应，4)允许分子开关嫁接到金表面。因此，将合成一系列基于母体络合物1的分子开关，并将研究它们在溶液和固体中的光磁性质。将进行分子开关接枝到金表面的初步实验，并研究其表面的光磁性质。本项目所取得的成果可能为在RT中有效地、可逆地切换薄膜和单分子中的分子的磁性提供了机会，这将在分子电子学和自旋电子学中得到广泛的应用。

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.