Reactions of polypyridylchromium(II) ions with oxygen: determination of the self-exchange rate constant of O sub 2 /O sub 2 sup minus
- Iowa State Univ., Ames (USA)
Reductive quenching of the {sup 2}E excited states of CrL{sub 3}{sup 3+} complexes, where L is 2,2'-bipyridine (bpy), 1,10-phenanthroline (phen), and their substituted analogues, by disodium ethylenediaminetetraacetate and sodium oxalate was studied by use of laser flash photolysis. The quenching by both compounds results in the rapid, irreversible formation of CrL{sub 3}{sup 2+} with a quantum yield that can approach a value of 2.0. This novel method for the generation of CrL{sub 3}{sup 2+} was utilized to study the reactions of CrL{sub 3}{sup 2+} with ground-state dioxygen. The rate constants for these reactions show a linear dependence on {delta}G{degree} as predicted by Marcus theory and range from 2.5 {times} 10{sup 5} M{sup {minus}1} s{sup {minus}1} (Cr(5-Clphen){sub 3}{sup 2+}) to 2.5 {times} 10{sup 7} M{sup {minus}1} s{sup {minus}1} (Cr(Me{sub 2}phen){sub 3}{sup 2+}). It is postulated that the reactions proceed by outer-sphere electron transfer to yield superoxide ion as the initial product, as supported by the quantity of H{sub 2}O{sub 2} determined after it disproportionation. The electrostatically corrected Marcus cross-relation yielded k{sub 22} = 2 {plus minus} 1 M{sup {minus}1} s{sup {minus}1} for the self-exchange rate constant of the O{sub 2}/O{sub 2}{sup {minus}} couple. A close inspection of the data obtained in this work along with the literature data strongly suggests that the true value of k{sub 22} lies in the range 1-10 M{sup {minus}1} s{sup {minus}1}. 31 references, 3 figures, 1 table.
- DOE Contract Number:
- W-7405-ENG-82
- OSTI ID:
- 5729273
- Journal Information:
- Journal of the American Chemical Society; (USA), Journal Name: Journal of the American Chemical Society; (USA) Vol. 110:15; ISSN 0002-7863; ISSN JACSA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400201* -- Chemical & Physicochemical Properties
400500 -- Photochemistry
AROMATICS
AZAARENES
AZINES
BIPYRIDINES
CHEMICAL REACTIONS
CHROMIUM COMPLEXES
COMPLEXES
DATA
DECOMPOSITION
ELECTROMAGNETIC RADIATION
EXPERIMENTAL DATA
HETEROCYCLIC COMPOUNDS
INFORMATION
LASER RADIATION
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHENANTHROLINES
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
PYRIDINES
RADIATIONS
RADICALS
SUPEROXIDE RADICALS
TRANSITION ELEMENT COMPLEXES