Light Modulation of Charge Transfer Processes in Inorganic-Organic Materials

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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 functional materials through functionalization with optically bistable photochromes. Photochromes undergo light-induced isomerization between two states that differ in the electronic structures 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, and charge-transfer processes between two organic chromophores, organic ligands, and metal centers, or between two metal centers in a mixed valence state. Previous work in our lab has demonstrated proof-of-principle for photochrome-induced charge transfer or energy transfer processes in an electronically bistable cobalt complex, fluorescent conjugated polymer nanoparticles, and fluorescent organic dyads. In this proposal, we describe experiments designed to understand the fundamental structural and electronic factors that govern these phenomena, the limits of photochrome-gated processes, and the kinetic and thermodynamic factors that regulate signal-to-noise ratios for optimizing light-induced gating for sensors and memory applications.