First electrogeneration of a platinum(iv) porphyrin: elucidation of the PtII/IV and PtIV/IIoxidation-reduction processes in nonaqueous media

Abstract

The first example for electrogeneration of a Pt(IV) porphyrin from its Pt(II) form is presented and the Pt^II/IV and reverse Pt^IV/II oxidation-reduction processes are elucidated by electrochemistry and thin-layer UV-visible spectroelectrochemistry. Three products, [(TPP˙⁺)Pt^II]⁺, [(TPP)Pt^IV]²⁺ and [(TPP˙⁺)Pt^IV]³⁺, produced by electrooxidation of the Pt(II) porphyrin have been characterized by in situ spectroelectrochemistry and ESR measurements after controlled potential bulk electrolysis. The first definitive evidence for the electrochemical conversion of a Pt(IV) porphyrin to its Pt(II) form is also presented. The potential for this electroreduction is highly dependent upon the nature of the anion, ClO₄⁻ or Cl⁻. A mechanism for the reversible conversion between Pt(II) and Pt(IV) tetraphenylporphyrins is proposed.