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Photoredox catalysis has rapidly expanded to become an indispensible tool for synthetic chemists. Recent developments in this field have demonstrated the potential for photoredox systems to activate normally unreactive substrates and leverage reactivity that cannot be accessed in classical two-electron pathways. Organic chromophores offer particular advantages over their transition metal counterparts, and an introduction to the principles of photoredox catalysis and the properties of common organic photoredox catalysts is provided. Given the importance of solution phase redox potentials in selecting successful catalyst/substrate combinations, we have utilized computational methods to predict redox potentials for a large set of representative organic compounds, demonstrating the predictive power of the computational approach by comparing the calculated redox potential values with experimentally measured potentials. The Nicewicz laboratory has made use of acridinium-based photoredox catalysts to accomplish the anti-Markovnikov addition of a number of nucleophiles to alkenes, and these systems were thought to rely on the cooperative activity of the acridinium catalyst and a redox active hydrogen atom donor. An in-depth investigation of the proposed mechanism illuminated key photophysical properties of the acridinium catalyst and confirmed the feasibility of a crucial mechanistic step that unites the activity of the co-catalysts. Observations in the course of this inquiry prompted us to design more robust acridinium catalysts, one of which was employed the development of a photoredox catalytic aryl CH amination reaction. This …