ENERGY & CHARGE MIGRATION & ANNIHILATION IN MULTICHROMOPHORIC NANOSTRUCTURES

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The complex molecular photoprocesses observed in photosynthetic/photovoltaic devices, such as energy migration and annihilation, functional photoswitching, and spatially extended electron transfer, occur not in isolated molecules, but require chemical integration of communicating subunits. The aim of the proposed project is to construct novel, multifunctional, supramolecular arrays of tetrapyrrolic compounds in solution, and characterize their stationary and dynamic physio-chemical properties with respect to energy migration and electron transfer mechanisms, as well as their deactivating interactions with molecular oxygen and organic quenchers of excited states. By the methods of stationary and kinetic fluorescent and phosphorescent spectroscopy, transient absorption spectroscopy (ms-fs time resolution), and computational molecular modeling of nuclear and electronic structure, the principal mechanisms of electronic energy excitation deactivation, and the processes which enable interchromophoric communication, will be studied in extended porphyrin assemblies. Particular attention will be afforded to the intermolecular interactions between the assemblies, molecular oxygen, and other excited state quenchers. The structures to be synthesized and investigated include a range of covalently linked chemical dimers and trimers, as well as self-assembling non-covalently bound arrays with additional active chromophores. Possible market applications of the project results would include: (1) aid in the design of molecular photochemical sensors of singlet oxygen, and (2) development in photodynamic cancer therapy.