Late transition metal complexes of oxypyriporphyrin and the platinum(II) complex of oxybenziporphyrin

Even though oxypyriporphyrin, a pyridone-containing porphyrinoid system, has the equivalent coordination core to true porphyrins, its coordination chemistry has been little explored. In this study, the first examples of palladium(II), platinum(II) and silver(II) oxypyriporphyrins have been synthesized. Conventional conditions failed to result in the formation of a platinum(II) complex, but moderate yields were obtained when oxypyriporphyrin was reacted with platinum(II) chloride in refluxing mixtures of DMF and acetic acid containing potassium acetate. The palladium(II) and platinum(II) derivatives were characterized by X-ray crystallography. The structurally analogous carbaporphyrinoid system oxybenziporphyrin was also shown to react with platinum(II) chloride under the same conditions to give a platinum(II) hydroxybenziporphyrin complex. Unlike oxybenziporphyrin, this complex is only weakly diatropic. In the presence of base, the diatropic character was reasserted to afford an aromatic anionic species.

Stepwise conversion of two pyrrole moieties of octaethylporphyrin to pyridin-3-ones: synthesis, mass spectral, and photophysical properties of mono and bis(oxypyri)porphyrins

Free-base octaethylporphyrin (OEP) was converted in two steps (beta,beta'-dihydroxylation and oxidative diol cleavage with concomitant aldol condensation) to the corresponding oxypyriporphyrin. This conversion was previously described to be applicable only to the Ni(II) complex of OEP. Modified diol cleavage conditions made this reaction sequence now applicable to free-base OEP. The single-crystal structure of the resulting free-base oxypyriporphyrin was determined, proving its near-perfect planarity. The reaction sequence can also be applied to oxypyriporphyrin itself, generating the unprecedented bacteriochlorin-type bis(oxypyri)porphyrin as two separable isomers. The ground-state (UV/Vis and fluorescence spectroscopies) and excited-state (transient triplet-triplet absorption, triplet lifetimes, and triplet EPR spectroscopy) photophysical properties of all chromophores are compared with those of OEP, chlorins, and oxochlorins. The pyridone-modified porphyrins possess unique spectroscopic signatures that distinguish them from regular porphyrins or chlorins. The presence of the pyridone moiety alters the ESI(+) collision-induced fragmentation properties of these oxypyriporphyrins only to a minor degree when compared with those of OEP or chlorins, confirming their stability.