Physical and Photophysical Properties of Spin-Polarized Molecules

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The Chemical Structure, Dynamics and Mechanisms B Program supports Professor James K. McCusker of the Department of Chemistry at Michigan State University for the design and development of chemical systems geared toward determining whether there exists a cause-and-effect relationship between the physical and/or photophysical properties of molecules and their innate spin properties, and if so, to what extent that connection can be exploited in order to manipulate the chemical reactivity of molecular systems. Building on the successful development of a model that led to the first experimental demonstration of spin control of dipolar energy transfer, specific projects being pursued are (1) elaboration of this model to determine the limits of its applicability with regard to Förster theory, (2) extension of this model to exchange energy transfer (i.e., Dexter), (3) the influence of zero-field spin polarization on photo-induced electron transfer processes in spin-coupled transition metal clusters, and (4) the synthesis and characterization of spin-coupled metal-semiquinone complexes molecules in which a combination of synthetic design and theory is being used to manipulate intramolecular spin polarization. In all of these projects, the research is being carried out through a confluence of organic and inorganic synthetic chemistries, steady-state and time-resolved spectroscopic measurements including (but not limited to) emission, ultrafast time-resolved absorption, and electron paramagnetic resonance, as well as theoretical efforts that include density functional theory calculations to explore the incorporation of spin and spin polarization into existing theories to describe electron and energy transfer dynamics.The concepts underpinning this research represent a new area of study concerning the light-induced properties of molecules: this project will provide important insights into an aspect of the electronic structure of an enormous class of compounds for which there is little experimental information presently available. Compounds possessing unique spin (angular momentum of electrons) and/or magnetic properties, particularly those whose properties can be manipulated synthetically in a predictable manner, hold promise as the basis for molecular-based electronic materials. The knowledge gained through this work can provide a foundation for the rational design of molecular systems for next-generation electronic and photo-electronic devices for information storage, energy conversion, and catalysis. The individuals involved in this work, which include men and women at both the undergraduate and graduate level, are receiving broad-based training in synthetic chemistry, state-of-the-art spectroscopic methodology, the study of the magnetic properties of molecular systems, as well as advanced theoretical methods.