Ball-milling for efficient synthesis of pyridine-containing iron(ii) photosensitizers

Photoredox catalysis is becoming more and more prevalent in the 21st century as a new tool for organic and polymer synthesis. In addition, this domain clearly fits the expectations of the twelve principles of green chemistry. However, access to metal containing photosensitizers is not always straightforward and can require long reaction times, the use of toxic solvents and multi-step synthesis. These are definitely drawbacks that could be overcome with the use of novel technologies. In this report, we develop a one-pot two-step synthesis of iron(ii) photosensitizers using ball-milling. Overall reaction times were drastically reduced, no solvent was needed during the reaction, and ten complexes could be isolated in high yields (73–99%). Using a transparent milling jar, the formation of the complexes could be followed using in situ Raman spectroscopy.