Metal Complexes of Donor-Bridge Acceptor Biradical Ligands: Testing Models for Electron Transfer/Transport/Quantum Interference and Controlling Excited State Wave Functions

North Carolina State University, Raleigh NC

Investigators

Abstract

In this project funded by the Chemical Structure, Dynamic & Mechanism B Program of the Chemistry Division, Professor David A. Shultz of the Department of Chemistry at North Carolina State University will develop detailed relationships between a molecule's structure and how it transports electrons. The goal of this research is to develop lucid connections between a molecule's shape and structure and electron transport, which are useful to the design of materials and devices that rely on electron transport. The results will have application in the next generations of molecular electronics and "spintronics" (electron spin-based electronics), photonics, organic light-emitting diodes and artificial photosynthetic reactors. The proposed research contains elements of molecular synthesis, structure, spectroscopy, reactivity and theory, and is thus well suited for an integrated education of scientists. The Shultz group has extensive experience in training scientists (including undergraduates and those from underrepresented groups) who go on to careers in academia, government laboratories, industry and entrepreneurship. Outreach activities involve hosting and training undergraduate summer researchers from Shaw University, a local Historically Black College/University (HBCU). Electron donor-acceptor interactions control electron transfer and transport at the molecular level. They are thus crucial, foundational elements in biological and artificial electron transfer and photosynthesis, solar energy conversion and molecular electronics/spintronics. The first thrust of the proposed research describes continued efforts in the Schultz group toward an elucidation of electronic coupling in Donor-Bridge-Acceptor systems in which the donor fragment is a metal-semiquinone and the acceptor is a nitronylnitroxide radical, and the magnetic electron spin-spin exchange coupling between the two is directly proportional to the square of the Donor-Acceptor electronic coupling. The second thrust of the proposed research describes studies aimed at using exchange coupling in photogenerated biradical excited states (via ligand-to-ligand charge transfer) to probe and ultimately to control excited state processes and to mimic exciton-polaron interactions.