Abstract
The oxidation potentials of MnII in aqueous solutions of bicarbonate, formate, acetate and oxalate are reported as a function of concentration and compared to the rate of photooxidation of these solutions by the Mn-depleted water-oxidizing complex of photosystem II (apo-WOC-PSII) from peas. Although all the carboxylate species lower considerably the oxidation potential of MnII, only bicarbonate stimulates the electron transfer from MnII to apo-WOC-PSII. On the basis of the electrochemical data it is proposed that the unique capability of Mn-bicarbonate complexes to be photooxidized by PSII could be due to four possible reasons: (i) significantly larger decrease in the oxidation potential of MnII (down to 0.52 V); (ii) electroneutrality of the functional electron transfer complex; (iii) the more favorable energetics reflected in the two pKa values for H 2CO3/HCO3 - and HCO3 -/CO3 2- and greater number of proton transfer sites; and (iv) multiple composition possibilities for the MnIII photo-product as MnIII(HCO3 -)3, MnIII(HCO3 -)(CO3 2-) and MnIII(HCO3 -)2(OH-) (due to the high Lewis acidity of MnIII (pK <1).
| Original language | English |
|---|---|
| Pages (from-to) | 4905-4911 |
| Number of pages | 7 |
| Journal | Physical Chemistry Chemical Physics |
| Volume | 6 |
| Issue number | 20 |
| DOIs | |
| Publication status | Published - Oct 21 2004 |
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ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Atomic and Molecular Physics, and Optics
Cite this
Oxidation potentials and electron donation to photosystem II of manganese complexes containing bicarbonate and carboxylate ligands. / Kozlov, Yuri N.; Zharmukhamedov, Serguei K.; Tikhonov, Konstantin G.; Dasgupta, Jyotishman; Kazakova, Alevtina A.; Dismukes, G Charles; Klimov, Vyacheslav V.
In: Physical Chemistry Chemical Physics, Vol. 6, No. 20, 21.10.2004, p. 4905-4911.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Oxidation potentials and electron donation to photosystem II of manganese complexes containing bicarbonate and carboxylate ligands
AU - Kozlov, Yuri N.
AU - Zharmukhamedov, Serguei K.
AU - Tikhonov, Konstantin G.
AU - Dasgupta, Jyotishman
AU - Kazakova, Alevtina A.
AU - Dismukes, G Charles
AU - Klimov, Vyacheslav V.
PY - 2004/10/21
Y1 - 2004/10/21
N2 - The oxidation potentials of MnII in aqueous solutions of bicarbonate, formate, acetate and oxalate are reported as a function of concentration and compared to the rate of photooxidation of these solutions by the Mn-depleted water-oxidizing complex of photosystem II (apo-WOC-PSII) from peas. Although all the carboxylate species lower considerably the oxidation potential of MnII, only bicarbonate stimulates the electron transfer from MnII to apo-WOC-PSII. On the basis of the electrochemical data it is proposed that the unique capability of Mn-bicarbonate complexes to be photooxidized by PSII could be due to four possible reasons: (i) significantly larger decrease in the oxidation potential of MnII (down to 0.52 V); (ii) electroneutrality of the functional electron transfer complex; (iii) the more favorable energetics reflected in the two pKa values for H 2CO3/HCO3 - and HCO3 -/CO3 2- and greater number of proton transfer sites; and (iv) multiple composition possibilities for the MnIII photo-product as MnIII(HCO3 -)3, MnIII(HCO3 -)(CO3 2-) and MnIII(HCO3 -)2(OH-) (due to the high Lewis acidity of MnIII (pK <1).
AB - The oxidation potentials of MnII in aqueous solutions of bicarbonate, formate, acetate and oxalate are reported as a function of concentration and compared to the rate of photooxidation of these solutions by the Mn-depleted water-oxidizing complex of photosystem II (apo-WOC-PSII) from peas. Although all the carboxylate species lower considerably the oxidation potential of MnII, only bicarbonate stimulates the electron transfer from MnII to apo-WOC-PSII. On the basis of the electrochemical data it is proposed that the unique capability of Mn-bicarbonate complexes to be photooxidized by PSII could be due to four possible reasons: (i) significantly larger decrease in the oxidation potential of MnII (down to 0.52 V); (ii) electroneutrality of the functional electron transfer complex; (iii) the more favorable energetics reflected in the two pKa values for H 2CO3/HCO3 - and HCO3 -/CO3 2- and greater number of proton transfer sites; and (iv) multiple composition possibilities for the MnIII photo-product as MnIII(HCO3 -)3, MnIII(HCO3 -)(CO3 2-) and MnIII(HCO3 -)2(OH-) (due to the high Lewis acidity of MnIII (pK <1).
UR - http://www.scopus.com/inward/record.url?scp=8144225860&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=8144225860&partnerID=8YFLogxK
U2 - 10.1039/b406569g
DO - 10.1039/b406569g
M3 - Article
VL - 6
SP - 4905
EP - 4911
JO - Physical Chemistry Chemical Physics
JF - Physical Chemistry Chemical Physics
SN - 1463-9076
IS - 20
ER -