Light-Induced Magnetic Switching as a Trigger for Phase Transitions in Molecular Materials

化学部化学结构、动力学与机制B项目将通过该奖项资助一个由佛罗里达州立大学化学与生物化学系的Mykhailo Shatruk教授和Nar S. Dalal教授领导的合作研究小组，研究光敏分子，这种分子可以将热、压力或光照射的作用转化为材料磁性和结构特性的实质性变化。这一设计原理的成功实施可能会导致新的铁电体和导体，它们可以由光的作用来驱动。利用Shatruk和Dalal团队在磁性和光磁性材料、铁电材料和有机导体的合成和表征方面的专业知识，该团队旨在创造可用于电子设备或光激活开关的新型多功能材料。该项目将积极吸引研究生和本科生参与实验室研究，包括来自物理科学领域代表性不足的群体的学生。研究小组计划继续他们在2012年和2014年夏季组织的本科磁性暑期学校，下一所学校计划在2016年夏季举办。该项目的目标是合成和表征光响应分子，这些分子能够将系统的温度、压力或光诱导的磁性状态变化转化为实质性的结构变化，从而引发材料中的另一种相变。Shatruk/Dalal团队将探索将分子水平上的光致磁双稳定性与分子基材料中的远程金属绝缘体跃迁和铁有序（磁性或电性）耦合在一起的方法。特别是，该团队将研究具有自旋交叉（SCO）行为的Fe（II）配合物，这种行为源于Fe（II）离子的抗磁性低自旋（LS）和顺磁性高自旋（HS）状态之间的温度或光诱导转变。为了通过光激发获得铁电性和电导率等特性，将调用光诱导LS到HS的转变。SCO与导电性共存的材料将提供一个平台来测试与SCO相关的协调原子位移对有机亚结构导电性的影响，并有可能通过化学压缩实现光致超导性。另一个重点是在无金属有机体系中探索类似于SCO的光诱导磁开关，其中磁状态的变化是由于顺磁性自由基和抗磁性自由基二聚体之间的相互转换。对这种无金属体系的研究可以在分子磁场中开辟一个新的领域，与目前对过渡金属配合物的研究平行。

With this award, the Chemical Structure, Dynamics & Mechanisms B Program of the Chemistry Division is funding a collaborative research team led by Professors Mykhailo Shatruk and Nar S. Dalal of the Department of Chemistry and Biochemistry at Florida State University to investigate photoresponsive molecules that can translate the action of heat, pressure, or light irradiation into substantial changes into changes in the magnetic and structural properties of materials. The successful implementation of this design principle could potentially lead to new ferroelectrics and conductors that could be actuated by the action of light. Leveraging the expertise of the Shatruk and Dalal groups in the synthesis and characterization of magnetic and photomagnetic materials, ferroelectric materials, and organic conductors, the team aims to create novel multifunctional materials that can be employed in electronic devices or light-activated switches. The project will actively involve graduate and undergraduate students in laboratory research, including students from groups underrepresented in physical sciences. The research team plans to continue their Undergraduate Summer Schools on Magnetism, first organized in Summers of 2012 and 2014, with the next school scheduled for Summer 2016.This project targets the synthesis and characterization of photoresponsive molecules capable of translating temperature-, pressure-, or light-induced changes in the magnetic state of the system into substantial structural changes, which consequently would trigger another type of phase transition in the material. The Shatruk/Dalal team will explore approaches to couple the photoinduced magnetic bistability at the molecular level to long-range metal-insulator transitions and ferroic orderings (magnetic or electric) in molecule-based materials. In particular, the team will study Fe(II) complexes with spin crossover (SCO) behavior, which stems from the temperature or light-induced transition between diamagnetic low-spin (LS) and paramagnetic high-spin (HS) states of the Fe(II) ion. The photoinduced LS to HS transitions will be invoked in order to achieve properties such as ferroelectricity and conductivity via photoexcitation. Materials in which SCO coexists with conductivity will provide a platform to test the effects of concerted atomic displacements associated with SCO on the conductivity of the organic substructure, with the potential to achieve photoinduced superconductivity via chemical compression. Another thrust aims to explore photoinduced magnetic switching, akin to SCO, in metal-free organic systems, where the change in the magnetic state is due to interconversions between paramagnetic radicals and diamagnetic dimers of radicals. The study of such metal-free systems could open up a new area in the molecular magnetism field that would parallel the studies currently performed on transition metal complexes.