Title: Optically Switching Charge – and Energy – Transfer Processes: Molecules to Devices

Abstract: Functional materials that undergo changes in magnetic, optical, and conducting properties upon application of external stimuli (light, electric field, or magnetic field) are central to the development of non-volatile memory technologies, spintronics devices, and sensors. Current challenges involve developing materials that switch between two functional states with light for scalable memory and sensor development. We have developed a novel strategy for light-driven advanced materials through functionalization with optically bistable photochromes. Photochromes undergo light-induced isomerization between two states that differ in the electronic structure of their ground and metastable states. We have developed photochromic spirooxazine ligands that can be bound to metal centers or incorporated into organic multichromophoric arrays. Once bound, light-induced changes in spirooxazine structure lead to changes in the redox potential, ground state energies, and excited state energies at the functional target component (metal center or chromophore). Such structural changes can then trigger energy-transfer or charge-transfer processes between two organic chromophores, organic ligands, or two metal centers in a mixed-valence state. Her we present proof-of-principle for photochrome-induced charge transfer in an electronically bistable cobalt complex, photochrome-induced energy transfer in fluorescent conjugated polymer nanoparticles, and optical triggering of gate voltages in graphene OFETs for sensor applications. The long-range goals of the work are to utilize optically-gated functional materials for scalable memory devices and fluorophore-based biosensors for medical diagnostics.