Time-resolved optical magnetic-circular-dichroism study of ligand-driven light-induced spin-change complexes

配体驱动光诱导自旋变化配合物的时间分辨光磁圆二色性研究

• 批准号: 35800054
• 负责人: Dr. Mark D. Thomson, Ph.D.
• 金额: --
• 依托单位: Physikalisches Institut
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2007
• 资助国家: 德国
• 起止时间: 2006-12-31 至 2011-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/35800054?language=en
• 关键词: Time; resolved; optical; magnetic; circular

In this project, we intend to apply our recently developed time-resolved magnetic circular dichroism (MCD) techniques to the study of metal complexes exhibiting the photomagnetic effect – light-induced excited-spin-state trapping (LIESST), where below a critical temperature one can reversibly switch the metal ion between a low-spin (LS) and high-spin (HS) state via irradiation. The target compound for the study is the well-established spin-crossover (SCO) complex Fe(II)phen2(NCS-)2 (phen = 1,10-phenanthroline). Previous investigations of related LS-Fe(II) complexes in room temperature solutions indicate that upon excitation, the LS compound reaches the HS state on a sub-picosecond time scale. This remarkable result demonstrates that the classical rules concerning spin dynamics (intersystem crossing rates) in organic systems need not apply in such metal-organic compounds. The precise excited-state dynamics dictates the quantum efficiency for magnetic switching and hence the performance of a given LIESST compound. Here we propose experiments for solid-state samples at low temperature (where the LIESST effect is operative), using paramagnetic UV-vis MCD as a sensitive probe of the spin state. We will determine the time scale for formation of the HS state using our femtosecond optical-pump MCD-probe system (in addition to transient absorption measurements), as well as addressing the role of intermediate triplet states during the LS-HS conversion. We will also further evaluate the use of continuous-wave MCD for characterising the SCO vs. temperature and LIESST effect during irradiation, and compare the results to corresponding SQUID magnetometry measurements.

在这个项目中，我们打算将我们最近开发的时间分辨磁性圆二色性（MCD）技术应用于金属配合物的研究，这些金属配合物表现出光磁效应-光诱导激发自旋态捕获（LIESST），在临界温度以下，人们可以通过照射可逆地在低自旋（LS）和高自旋（HS）状态之间切换金属离子。研究的目标化合物是已被广泛接受的自旋交叉（SCO）配合物Fe（II）phen 2（NCS-Phe）2（phen = 1，10-菲咯啉）。以前的研究相关的LS-Fe（II）配合物在室温下的解决方案表明，激发后，LS化合物达到HS状态的亚皮秒的时间尺度。这一显著的结果表明，有机体系中关于自旋动力学（系间交叉率）的经典规则不一定适用于这种金属有机化合物。精确的激发态动力学决定了磁开关的量子效率，从而决定了给定LIESST化合物的性能。在这里，我们建议在低温下（LIESST效应是操作），使用顺磁性紫外可见MCD作为自旋状态的敏感探针的固态样品的实验。我们将使用我们的飞秒光泵MCD探测系统（除了瞬态吸收测量）确定HS状态形成的时间尺度，以及解决中间三重态在LS-HS转换过程中的作用。我们还将进一步评估使用连续波MCD表征SCO与温度和照射过程中的LIESST效应，并将结果与相应的SQUID磁强计测量结果进行比较。