Platinum(II) and platinum(IV) porphyrin complexes: Synthesis, characterization, and electrochemistry

Article abstract of DOI:10.1016/S0277-5387(97)00026-0

Platinum(IV) porphyrins of the type [Pt^IV(p-X)₄TPP]Cl₂ where (p-X)₄TPP is a para-substituted tetraphenylporphyrin have been synthesized by the direct oxidation of their Pt^II precursors with Cl₂. Both the Pt^II and Pt^IV complexes have been characterized by visible and ¹H NMR spectroscopy and their electrochemical properties. The Soret, α and β bands of the visible spectra are shifted to longer wavelengths upon oxidation of the Pt^II. All ¹H resonances experience a downfield shift upon oxidation of the Pt^II to Pt^IV. Each [Pt^II(p-X)⁴TPP] complex shows two oxidations and two reductions and their potentials are dependent upon the X substituent on the porphyrin ring. In general, the [Pt^IV(p-X)₄TPP]Cl₂ complexes show a similar oxidation and reduction pattern and a substituent effect is evident. There is an additional reduction that can be attributed to Pt^IV → Pt^II.