Oxidation and reduction of manganese porphyrins in aqueous solutions by free radicals: a pulse radiolysis investigation

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1986

OSTI ID:6303398

Morehouse, K M

The one-electron transfer reactions of water soluble manganese porphyrins, MnP, (P = TPPS, TPPC, TMPyP or TPyP) have been investigated by steady-state and pulse radiolysis. Most porphyrins are reduced by e/sub aq/ with diffusion-controlled rate constants (approx.10 M s ). Thus reduction of Mn(III)P yields Mn(II)P which upon further reduction forms Mn(II)P (ligand -radical anion). The one-electron oxidation of porphyrins is carried out by Br2 , Cl2 and CH2CHO radicals. The rate constants are in the range of 10Y-10 M s depending on the redox potentials of the porphyrin and the radical used, and on their electrostatic charges. Oxidation of Mn(II)P by Br2 involves a rapid reaction (k = 2 x 10Z M s ) to form an intermediate complex Br-Mn(III)P, which hydrolizes to aqueous Mn(III)P in a first order process (k approx. 10Us ). Oxidation of Mn(III)P by the above radicals yields Mn(IV)P. The latter is further oxidized by Br2 at high pH to form either Mn(V)P or Mn(IV)P . Formation of the Mn(IV)P is favored over that of Mn(IV)P as the pH is increased (from 11 to 14) and in the order of porphyrins TPPS > TPPC > TMPyP.

• Research Organization: Notre Dame Univ., IN (USA)
• OSTI ID: 6303398
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400301* -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
AQUEOUS SOLUTIONS
CARBOXYLIC ACIDS
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISTRY
DATA
DECOMPOSITION
DIFFUSION
DISPERSIONS
ELECTRIC CHARGES
ELECTRON TRANSFER
ELEMENTS
EXPERIMENTAL DATA
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
INFORMATION
KINETICS
LIGANDS
MANGANESE
METALS
MIXTURES
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXIDATION
PORPHYRINS
PULSE TECHNIQUES
RADIATION CHEMISTRY
RADIATION EFFECTS
RADICALS
RADIOLYSIS
REACTION INTERMEDIATES
REACTION KINETICS
REDOX POTENTIAL
REDUCTION
SOLUTIONS
STEADY-STATE CONDITIONS
TRANSITION ELEMENTS
VALENCE