Physical and Photophysical Properties of Spin-Polarized Molecules

这个奖项在无机，生物无机和有机化学计划支持研究教授詹姆斯K。McCusker在密歇根州立大学研究受海森堡自旋交换影响的化合物的物理和电子物理性质。当两个（或多个）顺磁中心非常接近时，这种现象就会发生，从而提升自旋极化电子态的简并度。本研究将阐明自旋交换对分子光诱导性质的影响。与这项工作相结合的是研究，旨在更全面地了解开壳层分子中自旋和电荷密度之间的相互作用，目的是开发用于操纵分子系统的磁性和光磁性的协议。这些研究目标将沿着沿着三条不同的轨道进行。首先，将对分子中自旋和电荷密度之间的相互作用进行基础研究。计算结果表明，苯氧基自由基的自旋和电荷密度的微分极化可以通过明智地选择苯环上的取代基来实现。 本研究将扩展到半醌和菲并半醌，它们可以作为金属有机杂化化合物的配体。Secpmd，通过计算工作开发的模型，然后将通过制备和表征的Cr（III）和Ni（II）的化合物进行测试，以证明有能力调整分子内的反铁磁和铁磁相互作用，分别通过合成手段。一个系统的检查基态和激发态自旋交换的效果，然后描述通过一系列简单的Cr（III）配位化合物的研究。络合物含有氧化还原活性醌型配体，其允许交换根据配体的氧化态和/或针对光激发的吸收特征的性质而打开或关闭。 第三个项目开始扩展到扩展分子磁系统的领域。双金属半醌络合物将允许在更复杂的系统中系统地操纵自旋耦合。包括在这个项目是一个拟议的光磁实验，将使一个亚铁磁相互作用的瞬态电子激发态的直接检测。此外，该系统提供了一个平台，电化学，磁性和热力学数据的相关性，应该产生的海森堡交换模型的有效性的第一个实验探针。差分自旋和电荷极化的研究结果导致了一个实用的模型，这将使研究人员能够从综合调谐交换相互作用的角度进行思考，这将使那些在单分子磁性领域工作的人受益。自旋耦合系统的电子物理工作将提供洞察力的一个方面的电子结构的一大类化合物，目前有很少的实验信息。参与这项研究的学生将接受合成化学，最先进的光谱方法，磁学以及密度泛函理论在有机和无机分子中的应用方面的广泛培训。

This award in the Inorganic, Bioinorganic and Organometallic Chemistry program supports research by Professor James K. McCusker at Michigan State University to investigate the physical and photophysical properties of compounds subject to Heisenberg spin exchange. This phenomenon can occur whenever two (or more) paramagnetic centers are in close proximity so as to lift the degeneracy of spin-polarized electronic states. The research will elucidate the impact spin exchange on the photo-induced properties of molecules. Coupled to this work are studies geared toward gaining a more general understanding of the interplay between spin and charge density in open-shell molecules with the goal of developing protocols for the manipulation of the magnetic and photomagnetic properties of molecular systems. These research goals will be pursued along three distinct trajectories. First, a fundamental study of the interplay between spin and charge density in molecules will be undertaken. Computational work demonstrates that differential polarization of spin and charge density in phenoxy radicals can be achieved through judicious choice of substituents on the phenyl ring. The study will be expanded to semiquinones and phenanthrosemiquinones which can act as ligands in metalorganic hybrid compounds. Secpmd, the models developed through the computational work will then be tested through the preparation and characterization of Cr(III)- and Ni(II)-containing compounds so as to demonstrate the ability to tune intramolecular antiferromagnetic and ferromagnetic interactions, respectively, through synthetic means. A systematic examination of the effect of ground- and excitedstate spin exchange is then described through the study of a series of simple Cr(III) coordination compounds. The complexes contain redox-active quinoidal ligands that allow exchange to be turned on or off depending on the oxidation state of the ligand and/or the nature of the absorption feature targeted for photoexcitation. The third project begins an expansion into the realm of extended molecular magnetic systems. Dimetallic semiquinone complexes will allow for the systematic manipulation of spin coupling in a more complex system. Included in this project is a proposed photomagnetic experiment that will enable the direct detection of a ferrimagnetic interaction in a transient electronic excited state. In addition, this system provides a platform for the correlation of electrochemical, magnetic, and thermodynamic data that should yield the first experimental probe of the validity of the Heisenberg exchange model. The results of the study of differential spin and charge polarization leads toward a practical model that will allow researchers to think in terms of synthetically tuning exchange interactions, which would benefit those working in the field of single-molecule magnetism. The photophysical work on spin-coupled systems will provide insight into an aspect of the electronic structure of an large class of compounds for which there is currently little experimental information. Students involved in this research will receive broad-based training in synthetic chemistry, state-of-the-art spectroscopic methodology, magnetism, as well as the application of density functional theory to both organic and inorganic molecules.