Radiolytic and electrochemical reduction of Ru(bpz)/sub 3//sup 2 +/ in aqueous solution. Stability, redox, and acid-base properties of Ru(bpz)/sub 3//sup +1/
The reduction of Ru(bpz)/sub 3//sup 2 +/ in aqueous solution has been investigated by using radiolytic and electrochemical techniques. The one-electron reduction of Ru(bpz)/sub 3//sup 2 +/ by e/sub aq//sup -/, CO/sub 2//sup -/, and (CH/sub 3/)/sub 2/COH radicals is rapid (k = (5-9) x 10/sup 10/, and 3.5 x 10/sup 9/ M/sup -1/ s/sup -1/, respectively) and quantitative; the products of these reactions are Ru(bpz)/sub 3//sup +/, which can be represented as Ru(bpz)/sub 2/(bpz/sup -/)/sup +/, in alkaline solution and its conjugate acid Ru(bpz)/sub 2/(bpzH)/sup 2 +/ (pK/sub a/ = 7.1 +/- 0.3) in acidic solution. In the absence of oxygen, Ru(bpz)/sub 3//sup +/ is stable; in the presence of MV/sup 2 +/, an equilibrium is established with k(Ru(bpz)/sub 3//sup +/ + MV/sup 2 +/) = 1.3 x 10/sup 8/ M/sup -1/ s/sup -1/, k(Ru(bpz)/sub 3//sup 2 +/ + MV/sup +/) 1.7 x 10/sup 7/ M/sup -1/ s/sup -1/, and K/sub eq/ = 7.6. From these data and from cyclic voltammetric measurements a value of E/sup 0/(Ru(bpz)/sub 3//sup 2+/+/) = 0.50 V has been derived for alkaline aqueous solution. When the pH of the solution is changed from alkaline to acidic, E/sub pc/ shifts toward less negative potentials by about 170 mV. Accordingly, Ru(bpz)/sub 2/(bpzH)/sup 2 +/ is unable to reduce MV/sup 2 +/; it is unstable (t/sub 1/2/ approx. 20 s), presumably toward a disproportionation reaction leading to the starting material and to the doubly reduced species Ru(bpz)/sub 2/(bpzH/sub 2/)/sup 2 +/. The latter is also generated by controlled-potential electrolysis of Ru(bpz)/sub 3//sup 2 +/ in acidic solution; it can be electrochemically oxidized back to Ru(bpz)/sub 3//sup 2 +/, or it can generate Ru(bpz)/sub 2/(bpz/sup -/)/sup +/ slowly (t/sub 1/1/ approx. 1 h) upon reaction with OH/sup -/ under oxygen-free conditions.
- Research Organization:
- Universita di Bologna, Italy
- OSTI ID:
- 7073846
- Journal Information:
- Inorg. Chem.; (United States), Journal Name: Inorg. Chem.; (United States) Vol. 25:25; ISSN INOCA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400400* -- Electrochemistry
400600 -- Radiation Chemistry
AQUEOUS SOLUTIONS
AZINES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIPYRIDINES
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTIONS
CHEMISTRY
COBALT 60
COBALT ISOTOPES
COMPLEXES
DATA
DECOMPOSITION
DISPERSIONS
ELECTROCHEMISTRY
EXPERIMENTAL DATA
HETEROCYCLIC COMPOUNDS
INFORMATION
INTERMEDIATE MASS NUCLEI
INTERNAL CONVERSION RADIOISOTOPES
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
MINUTES LIVING RADIOISOTOPES
MIXTURES
NUCLEI
NUMERICAL DATA
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PH VALUE
PYRIDINES
RADIATION CHEMISTRY
RADIATION EFFECTS
RADICALS
RADIOISOTOPES
RADIOLYSIS
REDOX REACTIONS
REDUCTION
RUTHENIUM COMPLEXES
SOLUTIONS
TRANSITION ELEMENT COMPLEXES
VOLTAMETRY
YEARS LIVING RADIOISOTOPES