A greener tetraphenylporphyrin synthesis and metallation: an undergraduate teaching experiment

ABSTRACT

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.

GRAPHICAL ABSTRACT

KEYWORDS:

• Undergraduate
• porphyrin
• mechanochemistry
• microwave
• metalloporphyrin

Acknowledgements

This research was supported, in part, by Colorado State University Pueblo (CSUP) Department of Chemistry (M.A.C), SFU Chemistry Department (E.P.Z.), and the University of Toronto Department of Chemistry (J.R.D.). This research was also support by a CSUP Communities to Build Active STEM Education (CBASE) fellowship (M.A.N.) and the Saint Francis University Office of Student Research (E.P.Z.). The authors wish to thank Prof. Kyle A. Grice (DePaul University) for testing the optimized microwave-assisted porphyrin synthesis. We also thank Beyond Benign, with support from Millipore Sigma, for bringing the authors together within the green chemistry community and for additional support including a Faculty Fellowship (J.R.D.).

Disclosure statement

No potential conflict of interest was reported by the authors.