A greener tetraphenylporphyrin synthesis and metallation: an undergraduate teaching experiment

While porphyrin-related syntheses have become classic experiments in the undergraduate curriculum, traditional syntheses of the free-base meso-tetraphenylporphyrin (H2TPP) and its metallated derivatives can be energy-intensive, use hazardous solvents, and generate appreciable amounts of waste. In an attempt to make the synthesis of H2TPP and its metallated derivatives (MTPP where M = metal) better aligned with the principles of green chemistry, we optimized a microwave-assisted, microscale synthesis of H2TPP and alternative routes toward the metallation of H2TPP including solvent-substituted reflux and mechanochemical syntheses for the undergraduate teaching laboratory. The greenness of these syntheses were evaluated using various green metrics and qualitative comparison to previously reported syntheses.

Automated summary

Traditional syntheses of free-base meso-tetraphenylporphyrin (H2TPP) and its metallated derivatives are energy-intensive, use hazardous solvents, and generate waste. To align with green chemistry principles, we optimized a microwave-assisted, microscale synthesis of H2TPP and alternative routes for metallation including solvent-substituted reflux and mechanochemical syntheses for undergraduate teaching. Green metrics and qualitative comparison to previous syntheses were used to evaluate the greenness of these syntheses.