Alternatives to Iridium: A Polyaza[7]helicene as a Strongly Reductive Visible Light Photoredox Catalyst

The use of a readily accessible polyazahelicene as a strongly reducing metal-free alternative to the commonly used precious metal based photoredox catalysts is demonstrated. An improved two-step synthesis of the catalyst is described, and its photophysical properties with respect to its use as a photoredox catalyst are evaluated. Its activity under visible light irradiation is proven by application in two double radical light-driven multicomponent reactions. The azahelicene gave comparable results to an iridium-based catalyst originally used for the same transformations.

Automated summary

This study demonstrates the use of a readily accessible polyazahelicene as a strongly reducing metal-free alternative to commonly used precious metal-based photoredox catalysts. An improved two-step synthesis of the catalyst is described, and its photophysical properties as a photoredox catalyst are evaluated. The polyazahelicene exhibits comparable activity to an iridium-based catalyst in two double radical light-driven multicomponent reactions.