二芳基乙烯-Fe(II/III)自旋交叉分子光开关的设计与性质调控

Spin-crossover (SCO) metal complexes have an ideal molecular bistability (multistability) in which their high-spin and low-spin states can be controlled and switched by external stimuli, such as heat, pressure, light and so on. Hence, SCO complexes are viewed as molecular materials that have potentials for developing molecular switches and information storage devices. The main challenge of SCO systems is having controllable spin transition occurred near room temperature with hysteresis loop through molecular level operation. This project will incorporate photochromic diarylethene into SCO system and further construct Fe(II/III) SCO photoswitches. Our molecular design and research targets are as following: (1) Series of diarylethene ligands and auxiliary building blocks are designed to effectively control the ligand field strength, and hence making the spin transition temperature closed to room temperature; (2) We will synthesize series of mononuclear, dinuclear, and multinuclear metal complexes. Utilizing the intermolecular weak interactions (in case of mononuclear), intramolecular covalent interactions (in case of di- and multinuclear), and solvent effect to enhance the cooperativity of the system; (3) We will mainly study the effect of ligand-driven light-induced spin change (LD-LISC) deriving from the diarylethene ligands. We will establish a correlation between structure, light, and SCO magnetism based on numerous syntheses, characterizations, and analyses from this project. We hope we could lay the foundation for the development of SCO photoswitches which can be used at room temperature.

自旋交叉配合物具有理想的分子双（多）稳态，其高低自旋态可通过外界条件（温度、压力、光辐射等）的刺激相互转换，因此极有可能成为分子开关和信息存储器件。如何通过在分子水平上的结构调控实现室温附近自旋转换并有热滞回线是自旋交叉体系的主要挑战。本项目拟通过引入二芳基乙烯分子作为有机配体来构筑Fe(II/III)自旋交叉分子光开关。本项目的分子设计策略和核心研究思路是：（1）通过设计配位灵活的系列二芳基乙烯配体和辅助构筑基元来实现对配体场的有效调控，从而实现近室温自旋转换；（2）设计合成单核、双核和多核配合物，充分利用分子间弱作用力（单核体系）、分子内共价键作用力（双核和多核体系）和溶剂效应来调节增强体系的协同效应；（3）通过光对二芳基乙烯进行结构调控改变配体场强度从而调控自旋交叉行为，构建新型的“构-光-磁关系”。本课题旨在为室温自旋交叉分子光开关材料的设计开发提供理论支撑。

本项目实现了二芳基乙烯配体对Fe(II/III)配合物结构和磁性调控的研究目标。我们设计合成了一系列具有不同取代基、不同配位点和不同配位模式的二芳基乙烯有机配体，组装了具有不同结构的自旋交叉配合物，探索了光对结构和磁性调控的规律。本项目总结了Fe(II/III)配合物结构和自旋交叉行为的关系，构建了有效的结构-磁性调控关系，主要是配合物结构和自旋转换温度T1/2的关系，为开发自旋交叉分子光开关材料提供了理论指导，实现了本课题最重要的研究目标。. 本项目取得的最重要成果是基于二芳基乙烯配体的多构型、光响应特性，利用配位驱动自组装策略，构筑了三例不同结构的化合物，不仅实现了光对结构的调控，更重要的是实现了光对磁学性质的调控。相关成果发表在了国际顶尖学术期刊《Angew. Chem. Int. Ed.》上：Z. Y. Li*, J. W. Dai, M. Damjanovic, T. Shiga, J. H. Wang, J. Zhao, H. Oshio, M. Yamashita*, X. H. Bu*, Angew. Chem. Int. Ed., 2019, 58, 4339−4344。此外，在本项目的支持下还有7篇SCI论文发表，其中3篇影响因子大于10。