Light-driven electron and energy transfer in metallocorrole complexes: A combined femtosecond visible/IR and nanosecond EPR investigation

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Corroles, a rapidly developing class of tetrapyrroles, retain the aromatic character of porphyrins but differ by their ability to accommodate metals in higher oxidation states, and thus exhibit exceptional photophysical and chemical properties, relevant to basic science as well as technological applications. In this research proposal we concentrate on the influence of the core metal ion and axial ligands on photophysical and photochemical processes in the metallocorroles, and corrole based donor-acceptor complexes. The focus will be on metallocorroles with Al(lll), Ga(lll), Sb(lll), or Sb(V) as the central metal ion, covering the range from light to fairly heavy metal ions, and allowing the study of the influence of the oxidation state. The kinetics and structural dynamics of newly synthesized metallocorroles will be characterized on femtosecond to millisecond timescales, using polarizationresolved femtosecond visible and infrared spectroscopy, multimode electron paramagnetic resonance (EPR), and laser flash photolysis. The impact of the core metal ion and its oxidation states on the 3-dimensional structure will be studied. The results on isolated metallocorroles will be implemented in studies of photoinduced electron and energy transfer in corrole based donor-acceptor complexes. Particular emphasis will be devoted to the dependence of electron and energy transfer on the donor-acceptor distance, their mutual orientation, and the nature of their linkage such as covalent, electrostatic, coordinative, and hydrogen bonding. The information gained will enhance the development of advanced catalytic processes and the design of efficient biomimetic systems.