Micellar effects on photoinduced redox reactions of Fe(bpy)2(CN)2

O. Horváth, Kenneth L. Stevenson

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Excitation of solutions of Fe(bipy)2(CN)2 by a 266-nm laser pulse produces a hydrated electron and the oxidized complex, Fe(bipy)2 (CN)2+, in the primary photochemical step, in homogeneous aqueous solution as well as in aqueous solutions containing cetyltrimethylammonium bromide (CTAB) or sodium dodecyl sulfate (SDS) micelles. In all cases nascent hydrated electrons react with ground state Fe(bipy)2(CN)2 to form Fe(bipy)2(CN)2-, and comparison of the decay constants in the three media (H2O: k = 2.8 × 1010 M-1 s-1; CTAB: k = 2.9 × 1010 M-1 s-1; SDS: k = 5.5 × 109 M-1 s-1), shows that the reaction is essentially unaffected by CTAB micelles but is much slower in SDS solution. Similar micellar effects were found for the back reaction between eaq- and Fe(bpy)2(CN)2+. Rate constants for the scavenging of the photogenerated hydrated electrons by methyl viologen (MV2+) cations and NO3- anions were measured in the three systems, and the results indicate that for scavenging by MV2+ the rate constants are decreased in the micelle systems (k in H2O, 8.4 × 1010; CTAB, 3.5 × 1010 and SDS, 1.58 × 1010 M-1 s-1), whereas for NO3- the CTAB micelle decreases while the SDS micelle enhances the scavenging compared to water solution (k in H2O, 8.3 × 109; CTAB, 7 × 108; and SDS, 2.05 × 1010 M-1 s-1). For the comproportionation reaction between Fe(bipy)2(CN)2+ and Fe(bipy)2(CN)2- both micelles reduce the rate (k in H2O, 3.3 × 1010; CTAB, 2.3 × 1010; and SDS, 1.05 × 1010 M-1s-1), but while the reaction of Fe(bipy)2(CN)2+ with MV+ is increased in CTAB compared to water, it is slowed in SDS (k in H2O, 2.4 × 1010; CTAB, 8.9 × 1010; and SDS, 1.8 × 1010 M-1s-1). All effects observed in these microheterogeneous systems can be uniformly interpreted in terms of Coulombic interactions between the actual reactants and the charged surface of the micelles.

Original languageEnglish
Pages (from-to)185-190
Number of pages6
JournalJournal of Photochemistry and Photobiology A: Chemistry
Volume120
Issue number3
Publication statusPublished - Feb 2 1999

Fingerprint

Redox reactions
Sodium dodecyl sulfate
sodium sulfates
Sodium Dodecyl Sulfate
bromides
Micelles
micelles
Scavenging
scavenging
Electrons
Rate constants
aqueous solutions
cetrimonium
Paraquat
electrons
Water
Ground state
water
Anions
Cations

Keywords

  • Fe(bpy) (CN)
  • Micellar effects
  • Redox reactions

ASJC Scopus subject areas

  • Bioengineering
  • Physical and Theoretical Chemistry

Cite this

Micellar effects on photoinduced redox reactions of Fe(bpy)2(CN)2. / Horváth, O.; Stevenson, Kenneth L.

In: Journal of Photochemistry and Photobiology A: Chemistry, Vol. 120, No. 3, 02.02.1999, p. 185-190.

Research output: Contribution to journalArticle

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abstract = "Excitation of solutions of Fe(bipy)2(CN)2 by a 266-nm laser pulse produces a hydrated electron and the oxidized complex, Fe(bipy)2 (CN)2+, in the primary photochemical step, in homogeneous aqueous solution as well as in aqueous solutions containing cetyltrimethylammonium bromide (CTAB) or sodium dodecyl sulfate (SDS) micelles. In all cases nascent hydrated electrons react with ground state Fe(bipy)2(CN)2 to form Fe(bipy)2(CN)2-, and comparison of the decay constants in the three media (H2O: k = 2.8 × 1010 M-1 s-1; CTAB: k = 2.9 × 1010 M-1 s-1; SDS: k = 5.5 × 109 M-1 s-1), shows that the reaction is essentially unaffected by CTAB micelles but is much slower in SDS solution. Similar micellar effects were found for the back reaction between eaq- and Fe(bpy)2(CN)2+. Rate constants for the scavenging of the photogenerated hydrated electrons by methyl viologen (MV2+) cations and NO3- anions were measured in the three systems, and the results indicate that for scavenging by MV2+ the rate constants are decreased in the micelle systems (k in H2O, 8.4 × 1010; CTAB, 3.5 × 1010 and SDS, 1.58 × 1010 M-1 s-1), whereas for NO3- the CTAB micelle decreases while the SDS micelle enhances the scavenging compared to water solution (k in H2O, 8.3 × 109; CTAB, 7 × 108; and SDS, 2.05 × 1010 M-1 s-1). For the comproportionation reaction between Fe(bipy)2(CN)2+ and Fe(bipy)2(CN)2- both micelles reduce the rate (k in H2O, 3.3 × 1010; CTAB, 2.3 × 1010; and SDS, 1.05 × 1010 M-1s-1), but while the reaction of Fe(bipy)2(CN)2+ with MV+ is increased in CTAB compared to water, it is slowed in SDS (k in H2O, 2.4 × 1010; CTAB, 8.9 × 1010; and SDS, 1.8 × 1010 M-1s-1). All effects observed in these microheterogeneous systems can be uniformly interpreted in terms of Coulombic interactions between the actual reactants and the charged surface of the micelles.",
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N2 - Excitation of solutions of Fe(bipy)2(CN)2 by a 266-nm laser pulse produces a hydrated electron and the oxidized complex, Fe(bipy)2 (CN)2+, in the primary photochemical step, in homogeneous aqueous solution as well as in aqueous solutions containing cetyltrimethylammonium bromide (CTAB) or sodium dodecyl sulfate (SDS) micelles. In all cases nascent hydrated electrons react with ground state Fe(bipy)2(CN)2 to form Fe(bipy)2(CN)2-, and comparison of the decay constants in the three media (H2O: k = 2.8 × 1010 M-1 s-1; CTAB: k = 2.9 × 1010 M-1 s-1; SDS: k = 5.5 × 109 M-1 s-1), shows that the reaction is essentially unaffected by CTAB micelles but is much slower in SDS solution. Similar micellar effects were found for the back reaction between eaq- and Fe(bpy)2(CN)2+. Rate constants for the scavenging of the photogenerated hydrated electrons by methyl viologen (MV2+) cations and NO3- anions were measured in the three systems, and the results indicate that for scavenging by MV2+ the rate constants are decreased in the micelle systems (k in H2O, 8.4 × 1010; CTAB, 3.5 × 1010 and SDS, 1.58 × 1010 M-1 s-1), whereas for NO3- the CTAB micelle decreases while the SDS micelle enhances the scavenging compared to water solution (k in H2O, 8.3 × 109; CTAB, 7 × 108; and SDS, 2.05 × 1010 M-1 s-1). For the comproportionation reaction between Fe(bipy)2(CN)2+ and Fe(bipy)2(CN)2- both micelles reduce the rate (k in H2O, 3.3 × 1010; CTAB, 2.3 × 1010; and SDS, 1.05 × 1010 M-1s-1), but while the reaction of Fe(bipy)2(CN)2+ with MV+ is increased in CTAB compared to water, it is slowed in SDS (k in H2O, 2.4 × 1010; CTAB, 8.9 × 1010; and SDS, 1.8 × 1010 M-1s-1). All effects observed in these microheterogeneous systems can be uniformly interpreted in terms of Coulombic interactions between the actual reactants and the charged surface of the micelles.

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