Spectral, magnetic and electrochemical properties of metal oxa- and oxathia-porphyrins

Bashyam Sridevi, Seenichamy Jeyaprakash Narayanan, Alagar Srinivasan, Tavarekere K. Chandrashekar, Japyesan Subramanian
1998 Journal of the Chemical Society, Dalton Transactions  
Metal derivatives (Cu II , Ni II ) of monooxa-, dioxa-and oxathia-tetraphenylporphyrins and their one-electron oxidised and reduced species have been studied. Electronic spectra of the monooxa and oxathia derivatives exhibit split Soret bands and a complicated pattern of Q-bands revealing their lower symmetry. The spectra of one-electron reduced species show only marginal shifts while the one-electron oxidised product of copper monooxaporphyrins show broad, red-shifted bands. Cyclic
more » ... Cyclic voltammetric studies indicated one-electron metalcentered reduction at fairly low potentials forming copper() and nickel() porphyrins. The ring-oxidised product exhibits weak antiferromagnetic interaction between the unpaired electrons of copper and the porphyrin ring. The ESR spectra of the copper dioxa-and oxathia-porphyrins exhibit rhombic symmetry with unusually small metal hyperfine couplings. A comparison of A Cu values and the E ₂  ₁ values for metal reduction suggests that distortion towards tetrahedral symmetry and the presence of a soft donor atom like sulfur in porphyrins are required to generate spectral and electrochemical properties like those observed for the type I copper center in proteins.
doi:10.1039/a801934g fatcat:per3whzqtvbfzoadapae336ywu