Site of one-electron reduction of Ni(II) porphyrins. Formation of Ni(I) porphyrin or Ni(II) porphyrin. pi. -radical anion

Journal Article · Thu Aug 23 00:00:00 EDT 1990 · Journal of Physical Chemistry; (USA)

DOI:https://doi.org/10.1021/j100380a026· OSTI ID:6380922

Nahor, G S; Neta, P ^[1]; Hambright, P; Robinson, L R ^[2]; Harriman, A ^[3]

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1. National Institute of Standards and Technology, Gaithersburg, MD (USA)
2. Howard Univ., Washington, DC (USA)
3. Univ. of Texas, Austin (USA)

The products of one-electron reduction of a series of nickel(II) porphyrins (Ni{sup II}P) have been examined by radiolytic reduction in protic media to determine whether Ni{sup I}P or the {pi}-radical anion Ni{sup II}P{sup {sm bullet}{minus}} is formed. Kinetic spectrophotometric detection was utilized to record absorption spectra of the product immediately after one-electron reduction, and {gamma}-radiolysis was used for recording spectra of the stable reduction products. In the submillisecond time scale, certain Ni{sup II}-porphyrins were found to be reduced to Ni{sup I}P, whereas others gave Ni{sup II}P{sup {sm bullet}{minus}}. The initial reduction product was dependent on the nature of substituents on the porphyrin but not on the redox potential; a meso-4-pyridyl group seems to direct the reduction toward the porphyrin ring, whereas in most other cases reduction occurred on the metal. On longer time scales (minutes) all porphyrins produced to two-electron reduced products, chlorin or phlorin anion. This suggests that both Ni{sup I}P and Ni{sup II}P{sup {sm bullet}{minus}} disproportionate to give Ni{sup II}P and Ni{sup II}P{sup 2{minus}}, such that for Ni{sup I}P an intramolecular electron transfer takes place from Ni{sup I} to its porphyrin ligand.

• OSTI ID: 6380922
• Journal Information: Journal of Physical Chemistry; (USA), Journal Name: Journal of Physical Chemistry; (USA) Vol. 94:17; ISSN 0022-3654; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ABSORPTION SPECTRA
ANIONS
CARBOXYLIC ACIDS
CHARGED PARTICLES
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTIONS
CHEMISTRY
COMPLEXES
DECOMPOSITION
ELECTRON TRANSFER
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
IONS
KINETICS
NICKEL COMPLEXES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PORPHYRINS
RADIATION CHEMISTRY
RADIATION EFFECTS
RADIOLYSIS
REDUCTION
SPECTRA
TRANSITION ELEMENT COMPLEXES