PLATINUM(II) AND PLATINUM(IV) PORPHYRIN COMPLEXES - SYNTHESIS, CHARACTERIZATION, AND ELECTROCHEMISTRY

Platinum(IV) porphyrins of the type [Pt-IV(p-X)(4)TPP]Cl-2 where (p-X) (4)TPP is a para-substituted tetraphenylporphyrin have been synthesize d by the direct oxidation of their Pt-II precursors with Cl-2. Both th e Pt-II and Pt-IV complexes have been characterized by visible and H-1 NMR spectroscopy and their electrochemical properties. The Soret, alp ha and beta bands of the visible spectra are shifted to longer wavelen gths upon oxidation of the Pt-II. All H-1 resonances experience a down field shift upon oxidation of the Pt-II to Pt-IV. Each [Pt-II(p-X)(4)T PP] complex shows two oxidations and two reductions and their potentia ls are dependent upon the X substituent on the porphyrin ring. In gene ral, the [Pt-IV(p-X)(4)TPP]Cl-2 complexes show a similar oxidation and reduction pattern and a substituent effect is evident. There is an ad ditional reduction that can be attributed to Pt-IV-->Pt-II. (C) 1997 E lsevier Science Ltd.