Martin Kirk – University of New Mexico: "Spin Control of Ground and Excited State Processes in Donor-Acceptor Systems" (Host: Verani)

Excited state interactions in spin containing Donor-Acceptor and Donor-Bridge-Acceptor systems are important for understanding the impact of electronic coupling (Hab) in molecular electronics and how magnetic exchange interactions affect excited state processes. Our efforts have focused on determining excited state contributions to molecular bridge mediated electronic coupling, understanding how open-shell excited state singlet configurations promote long-range electron correlation, and developing new platforms for spin control of excited state dynamics in photoexcited donor-acceptor molecules. Using novel Donor-Bridge-Acceptor biradical and related complexes, we have been able to test recent theoretical hypotheses in molecular electronics as they relate to coherent superexchange in electron transfer/transport conduits, spin-polarized electron transport, and the control of quantum interference effects. Radical elaborated transition metal complexes represent ideal platforms for exploring the relationship between photoinduced charge separation and long-range spin correlation, impacting the solar energy, organic lighting, and molecular spintronics fields. These systems are also relevant to the emerging molecular quantum information science field, allowing for the optical generation and manipulation of spin qubits. Here we will primarily focus on the optical generation of electron spin polarization using radical elaborated donor acceptor complexes, and this will include the polarization of multiple exchange coupled spins. We will show how we have used a combined spectroscopic approach augmented by detailed bonding calculations to provide keen insight into the electronic structure of these novel transition metal – radical complexes, furthering our understanding of molecular electronic systems at the nanoscale.