Reduction reactions of water soluble cyano-cobalt(III)-porphyrins: Metal versus ligand centered processes
- National Institute of Standards and Technology, Gaithersburg, MD (USA)
Reduction reactions of dicyano-cobalt(III)-porphyrins (potential in vivo cyanide scavenger drugs) were studied by radiolytic and electrochemical methods using the water soluble tetrakis(4-sulfonatophenyl)porphyrin (TPPS) and tetrakis(N-methyl-4-pyridyl)porphyrin (TMPyP). For ((CN)2CoIIITPPS)-, reduction occurs stepwise to the CoII, CoI, and finally to the phlorin anion. This behavior is similar to that of the cobalt porphyrins in the absence of cyanide, except that the cyanide ligand shifts the reduction potentials to much more negative values. On the other hand, under radiolytic conditions, ((CN)2CoIIITMPyP)- is reduced on the porphyrin macrocycle by one electron to give the CoIII pi-radical anion, which disproportionates into the initial complex and the two-electron ring reduced CoIII phlorin. The radical anion is also formed by intramolecular electron transfer subsequent to the reaction of CoIITMPyP and cyanide. The results are compared with the chemistry of Vitamin B-12.
- OSTI ID:
- 6551863
- Journal Information:
- Journal of Inorganic Biochemistry; (USA), Journal Name: Journal of Inorganic Biochemistry; (USA) Vol. 39:2; ISSN JIBID; ISSN 0162-0134
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
560300* -- Chemicals Metabolism & Toxicology
59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ANIONS
CARBOXYLIC ACIDS
CHARGED PARTICLES
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTIONS
CHEMISTRY
COBALT
COMPARATIVE EVALUATIONS
CYANIDES
DECOMPOSITION
DRUGS
ELECTROCHEMISTRY
ELECTRON TRANSFER
ELECTRONS
ELEMENTARY PARTICLES
ELEMENTS
FERMIONS
HEMATINICS
HEMATOLOGIC AGENTS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
IONS
LEPTONS
LIGANDS
METABOLISM
METALS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PORPHYRINS
RADIATION CHEMISTRY
RADIATION EFFECTS
RADICALS
RADIOLYSIS
REDOX REACTIONS
TRANSITION ELEMENTS
VITAMIN B GROUP
VITAMIN B-12
VITAMINS