Electrochemistry and Spectroscopy of Sulfate Complexes of (Tetraphenylporphyrinato)manganese

✍ Scribed by Kevin Lawson; Jeff Gross; Philip W. Crawford

• Publisher: John Wiley and Sons
• Year: 2004
• Tongue: German
• Weight: 175 KB
• Volume: 87
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.200490002

✦ Synopsis

Abstract

The electrochemical and spectroscopic properties of [Mn~2~(tpp)~2~(SO~4~)] (H~2~tpp=tetraphenylporphyrin=5,10,15,20‐tetraphenyl‐21__H__,23__H__‐porphine) were studied to characterize the stability of this compound as a function of solvent, redox state, and sulfate concentration. In non‐coordinating solvents such as 1,2‐dichloroethane, the dimer was stable, and two cyclic voltammetric waves were observed in the region for Mn^III^ reduction. These waves correspond to reduction of the dimer to [Mn^II^(tpp)] and [Mn^III^(tpp)(OSO~3~)]^−^, and reduction of [Mn^III^(tpp)(OSO~3~)]^−^ to [Mn^II^(tpp)(OSO~3~)]^2−^, respectively. In the coordinating solvent DMSO, [Mn~2~(tpp)~2~(SO~4~)] was unstable and dissociated to form [Mn^III^(tpp)(DMSO)~2~]^+^. A single voltammetric wave was observed for Mn^III^ reduction in this solvent, corresponding to formation of [Mn^II^(tpp)(DMSO)]. In non‐coordinating solvent systems, addition of sulfate (as the bis(triphenylphosphoranylidene)ammonium (PPN^+^) salt) resulted in dimer dissociation, yielding [Mn^III^(tpp)(OSO~3~)]^−^. Reduction of this monomer produced [Mn^II^(tpp)(OSO~3~)]^2−^. In DMSO, addition of SO$\rm{_{4}^{2-}}$ led to displacement of solvent molecules forming [Mn^III^(tpp)(OSO~3~)]^−^. Reduction of this species in DMSO led to [Mn^II^(tpp)(DMSO)].