Collaborative Research: Infra-red Control of Electron Transfer Mechanisms

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In this collaborative project funded by the Chemical Structure, Dynamics & Mechanisms B Program of the Chemistry Division, Professors David N. Beratan and Peng Zhang of the Department of Chemistry at Duke University and Professors Igor V. Rubtsov and Russell H. Schmehl of the Department of Chemistry at Tulane University are developing novel ways to control the flow of electrical charge through molecules. Electron transfer at the molecular scale is essential in naturally occurring reactions and in devices of technological significance. The ability to dial in the rate of electronic motion and to control the directionality of these reactions on the molecular scale is a significant challenge that could open up new strategies for solar energy conversion, for understanding of biological energy conversion schemes, and for developing new strategies for devices of technological significance. The project includes intensive collaborations among chemical synthesis, ultrafast spectroscopy, and theory to establish a very rich interdisciplinary training environment for students. The team is promoting science and education by providing summer research opportunities to economically-disadvantaged and historically underrepresented groups. In addition, novel curriculum developments involve multi-university, multi-faculty teaching of courses that address the chemical and physical principles underpinning the research. The overall aim of the project is to understand the chemical and physical approaches that use infrared perturbations to control charge flow at the molecular scale. The research also includes the design of novel molecular structures where the charge flow is strongly influenced by the infra-red radiation. The project combines the power of theoretical and experimental approaches to manipulate charge flow in molecules. The researchers use ultrafast multi-pulse spectroscopic methods in the laboratory to drive and to perturb the reaction dynamics of donor-bridge-acceptor compounds. Several classes of donor-bridge-acceptor molecular systems are prepared and studied, including transition-metal complexes, bimetallic complexes, hydrogen-bonded systems, and systems with bi-stable bridges. Using newly developed methods of non-equilibrium molecular dynamics, the same molecular systems examined in the experimental laboratory are simulated, targeting the development of understanding vibrational excitation that may perturb both reaction coordinate motion and donor-acceptor electronic coupling interactions.