Tunable Redox Potential Photocatalyst: Aggregates of 2,3-Dicyanopyrazino Phenanthrene Derivatives for the Visible-Light-Induced α-Allylation of Amines

This work highlights the tunable redox potential of 6,11-dibromo-2,3-dicyanopyrazinophenanthrene (DCPP3) aggregates, which can be formed through physical π-π stacking interactions with other DCPP3 monomers. Electrochemical and scanning electron microscopy showed that the reduction potential of [DCPP3]_n aggregates could be increased by decreasing their size. The size of [DCPP3]_n aggregates could be regulated by controlling the concentration of DCPP3 in an organic solvent. As such, a fundamental understanding of this tunable redox potential is essential for developing new materials for photocatalytic applications. The [DCPP3]_n aggregates as a visible-light photocatalyst in combination with Pd catalysts in the visible-light-induced α-allylation of amines were used. This [DCPP3]_n photocatalyst exhibits excellent photo- and electrochemical properties, including a remarkable visible-light absorption, long excited-state lifetime (16.6 μs), good triplet quantum yield (0.538), and high reduction potential (E_red([DCPP3]_n/[DCPP3]_n^-) > -1.8 V vs SCE).