Probing Bis-FeIV MauG: Isolation of Highly Reactive Radical Intermediates

5 years ago

Probing Bis-FeIV MauG: Isolation of Highly Reactive Radical Intermediates

Sankar Prasad Rath, Sabyasachi Sarkar, Tapas Guchhait, Younis Ahmad Pandit

MauG is a diheme enzyme that utilizes two covalently bound c-type heme centers. We report here step-wise oxidations of a synthetic analogue of MauG in which two heme centers are bridged covalently through a flexible linker containing a pyrrole moiety. One- and two-electron oxidations produce monocation radical and dication diradical intermediates, respectively, which, being highly reactive, undergo spontaneous intramolecular rearrangement involving the pyrrole bridge itself to form indolizinium-fused chlorin–porphyrin and spiro–porphyrinato heterodimers. Unlike in MauG, where the two oxidizing equivalents produce the bis-FeIV redox state, the synthetic analogue of the same, however, stabilizes two ferric hemes, each coupled with a porphyrin π-cation radical. The present study highlights the possible role played by the bridge in the electronic communication. Step-wise oxidations of a synthetic analogue of diheme MauG enable isolation and structural characterizations of a dication diradical, an indolizinium-fused chlorin–porphyrin heterodimer and a spiro-porphyrinato heterodimer. The active role played by the bridge in the electronic communication has been explored.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/chem.201702321