Donor-Acceptor Interactions and Their Relationship to Molecular Electronics and Excited State Processes.

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In this project funded by the Chemical Structure, Dynamics and Mechanism B Program of the Chemistry Division, Professor Martin L. Kirk of the Department of Chemistry and Chemical Biology at the University of New Mexico is studying how electronically active molecules can be used in molecular electronics and other molecule-based technologies. Prof. Kirk is studying (1) how electrons flow through the molecules and can be controlled, (2) how the structures of the molecules affect their absorption of light, and (3) the nature of the molecules' excited states after light has been absorbed. The research is interdisciplinary and positioned at the interface of organic, inorganic, and physical chemistry and is providing enhanced opportunities for the education and training of next generation scientists. Professor Kirk is involved in teaching, training and mentoring student researchers, including those from underrepresented groups. He is also participating in outreach projects in New Mexico including those associated with the Albuquerque Explora! Museum and NanoDays.The project goals focus on using creatively designed magnetic exchange coupled Donor-Bridge-Acceptor biradical systems to explore (1) molecular quantum interference and molecular rectification, (2) anisotropic covalency induced spin orbit coupling contributions to excited state lifetimes, and (3) how excited state magnetic exchange interactions affect magneto-optical activity, spin polarization, and excited state relaxation pathways. The project utilizes a combined spectroscopic approach augmented by theory and computations to address these problems. Regarding molecular electron transport phenomena, Donor-Bridge-Acceptor electronic coupling in the context of molecular conductance is studied in order to test recent theoretical hypotheses and compare results to those that have been obtained under device conditions. This work could directly impact the molecular electronics field. Modulation of spin orbit coupling through anisotropic covalency impacts the ability to control relaxation rates and pathways in photoexcited states. Work using magnetic circular dichroism and transient spectroscopies reveals the nature of complex multi-spin excited state magnetic exchange interactions that derive from photoexcitation. The research contributes to a greater understanding of excited state magnetism, exciton-polaron coupling, and solar energy conversion. The project advances knowledge and understanding in the field of donor-acceptor interactions and contribute substantially to the understanding of molecular electronics, atom level control of excited state lifetimes, and spin effects on excited state processes.