Property-Enhanced Porphyrins

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In natural photosynthesis, the sun light is directly collected and conveyed to a pair of precisely organised porphyrins, the special pair, which undergoes charge separation. The liberated electron is then translated into chemical energy that is used to develop the living organism. In brief, photosynthesis consumes carbon dioxide and water to produce energy-rich molecules and delivers Oxygen as a by-product. While the efficiency of natural photosynthesis is questionable, its molecular building blocks are self-assembled, made from common non-toxic elements and its waste and by-products are environmentally favourable. In relation to our most pressing environmental challenges and ever-increasing energy consumption, photosynthesis thus represents the perfect solution.However, the complexity of the molecular architecture involved in photosynthesis renders it difficult to reproduce artificially. Nevertheless, it is possible to mimic specific aspects of photosynthesis and researchers have concentrated their efforts in the development of carbon capture, bio-fuel production, water splitting and photovoltaic solar cells. Each of these approaches to artificial photosynthesis includes an antenna system to harvest the sun light. Alike in natural photosynthesis, the role of the antenna in these artificial systems can be played by a porphyrin.Within femto- to picoseconds after absorbing the incoming sun light energy, the porphyrin undergoes specific mechanisms. Of particular interest to this project, we will investigate the following mechanisms: internal conversion, inter-system crossing and direct charge separation. Each of these relaxation pathways dictates the overall device's conversion efficiency. It is therefore crucial to understand the factors that can enhance these specific pathways to develop more efficient devices. We propose use the latest laser technology to investigate these mechanisms that are ultrafast by nature. More precisely, we will systematically study the effect of atom substitution, ring bending, and ring expansion in series of unique single-porphyrins that differs from one-another by a single constituent. Similarly, to investigate the effect of host electronegativity, we will investigate porphyrin-embedded complexes (called cytochromes) that differs from one another by the nature of their ligand, and thus electrostatic environment. The outcome of this project is to generate a list of physical characteristics that enhance either internal conversion, inter-system crossing or charge separation. With such list in hand we would then be able to design improved porphyrins for specific applications.