A Monolithium Monohydrogen Porphyrin

Abstract

Abstract Porphyrins and their metal complexes play essential roles in biological and industrial processes, functioning as key components in catalysis, photodynamic therapy, and organic (opto‐)electronic materials. Despite their significance, the intermediate states involved in metal incorporation into porphyrins remain poorly understood and are rarely observed as stable compounds. Here, we report the solvent‐free synthesis of the first neutral alkali metal monohydrogen porphyrin, which was selectively obtained by reaction of lithium vapor with thin films of tetraphenylporphyrin (H 2 TPP) under ultrahigh vacuum (UHV) conditions. The resulting monolithium monohydrogen tetraphenylporphyrin (LiHTPP) exhibits remarkable thermal stability and can be sublimated under UHV at 485 K without disproportionation, enabling its isolation. LiHTPP reacts with additional lithium to form dilithium tetraphenylporphyrin (Li 2 TPP), as confirmed through product analysis and reaction monitoring via photoelectron spectroscopy and mass spectrometry. Complementary theoretical simulations provide deeper insight into the chemical structure of this non‐planar complex and the energetics of its formation. This study advances the understanding of monohydrogen metalloporphyrins and their role in metalation pathways, introducing a novel synthetic route for stable intermediates. The study also underscores the potential of monohydrogen metalloporphyrins for developing catalysts and electronic materials with tunable properties.