Electron transfer reactions of excited dyes with metal complexes. Progress report, May 1, 1976--January 31, 1977. [Fe(III)--thionine reaction]
A study was initiated of the factors which determine quantum efficiency of transfer of reducing equivalents between excited dye molecules and metal complexes in their ground state and composition and dynamics of formation and decay of related photostationary states. A ruby laser capable of delivering a 3.6 J, 19 nsec flash was acquired and assembly of an apparatus for laser flash photolysis begun. At the same time, conventional flash photolysis was used to pursue investigation of the dependence upon solvent, anions, pH, and ionic strength of the kinetics of the spontaneous dark reaction of Fe(H/sub 2/O)/sup 3 +//sub 6/ with leucothionine and with semithionine, reactions which contribute to the composition and dynamics of formation and decay of the photostationary state of the iron-thionine photoredox reaction. Results are consistent with formation of an intermediate complex between leucothionine and Fe(III), K/sub A/ = 380 M/sup -1/ and k(elec. transfer) = 0.88 s/sup -1/ at approximately 22/sup 0/ in water solution at pH2, with sulfate as anion and ..mu.. = .05 - .1 M. Under similar conditions in 50 v/v percent aqueous CH/sub 3/CN, K/sub A/ = 780 M/sup -1/, k(elec. transfer) = 0.55 s/sup -1/. In both solvents, sulfate produces a large positive salt effect. Intermediacy of a complex was not established for the faster reaction of Fe(III) with semithionine under similar conditions: K/sub A/ . k(elec. transfer) approximately 3.5 x 10/sup 5/ M/sup -1/s/sup -1/ in H/sub 2/O, approximately 1.0 x 10/sup 4/ in 50 v/v percent aqueous CH/sub 3/CN.
- Research Organization:
- Boston Univ., MA (USA)
- DOE Contract Number:
- EY-76-S-02-2889
- OSTI ID:
- 7311301
- Report Number(s):
- COO-2889-1
- Country of Publication:
- United States
- Language:
- English
Similar Records
Photochemical conversion of solar energy. Third quarter progress report, July 1, 1974--September 30, 1974. [Iron--thionine]
Photochemical conversion of solar energy. Annual progress report, 1 January--31 Dec 1976. [Iron--thionine and iron--thiozine]
Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
IRON COMPLEXES
CHEMICAL REACTION KINETICS
THIONINE
ELECTRON TRANSFER
NITRILES
PHOTOLYSIS
SULFATES
WATER
AMINES
CHEMICAL REACTIONS
COMPLEXES
DECOMPOSITION
HETEROCYCLIC COMPOUNDS
HYDROGEN COMPOUNDS
KINETICS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC SULFUR COMPOUNDS
OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
REACTION KINETICS
SULFUR COMPOUNDS
TRANSITION ELEMENT COMPLEXES
400201* - Chemical & Physicochemical Properties
400301 - Organic Chemistry- Chemical & Physicochemical Properties- (-1987)