Phenoxazine photocatalysts (Phenox O-PC™) are some of the strongest reducing visible light PCs available. Phenoxazine PCs can be tuned for long excited state lifetimes, high triplet yields, and redox reversibility, properties advantageous for photocatalysis. Phenoxazine PCs are strong excited state reductants capable of reducing alkyl and aryl halides via an electron transfer mechanism. The alkyl radicals formed can partake in substitution or addition reactions on unsaturated vinyl or aromatic groups e.g., atom transfer radical polymerization, atom transfer radical addition and trifluoromethylation