Tetra(Pentafluorophenyl)porphyrin [H2.(TFPP)] in refluxing acetic acid with AgNO3 converts to tetrafpenta- fluorophenyl)porpholactone, I; i.e. one exo C2H2 unit becomes CO2. This change is proven by mass spectrometry and supported by 1H NMR, 19F NMR, and FTIR. I has a porphyrinic absorption spectrum and a strong fluorescence, with a quantum yield of 0.2. Addition of oxalic acid allows reproducible conversion of H2(TFPP)→I, and a 15% yield has been obtained. Iterative extended Hückel (IEH) calculations confirm a porphyrinic electronic structure with the π orbitals on both the oxa and oxo oxygen present in three of the porphyrin “four orbitals'1responsible for the optical spectra. Under similar conditions another metal-free porphyrinic substance has been made, which is tentatively identified as a porphodilactone. Also Ag, Ni, and Cu derivatives have been made that are presumed to be porpholactones or porphodilactones. IEH calculations predict that in the free bases the central protons are trans, avoiding the azlactone ring in the porpholactone and the opposite porphodilactone; in the adjacent porphodilactone, they are also predicted to be trans rather than cis.
ASJC Scopus subject areas
- Colloid and Surface Chemistry