Effect of diffusion on the photoinduced reaction between a tetra-anionic porphyrin and methylviologen cation in methanol.
The quenching of the fluorescence decay of electronically excited 5,10,15,20-tetraphenyl- 21H, 23H-porphinetetrasulfonate (TPPS (4-)*) in the presence of methylviologen cations (MV (2+)) was measured at various ionic strengths in methanol. Analysis of the fluorescence decay curves revealed strong evidence for the presence of a second fluorescent species over the entire range of ionic strength used in this work, which is attributed to solvent-separated ion pairs (TPPS (4-)-S-MV (2+)). Transient effects of the fluorescence decays were analyzed, and values for the effective reaction distance, R NH, and the diffusion coefficients, D, were obtained. Diffusion coefficients were independently measured for TPPS (4-) and MV (2+) using the Taylor dispersion method. The values for D obtained by the analysis of the transient effect were found to be smaller than those for the sum of the diffusion coefficients of TPPS (4-) and MV (2+) obtained by the Taylor dispersion method and a possible explanation for this result is given.
Department of Applied Chemistry, Okayama University of Science, 1-1 Ridai-cho, Okayama 700-0005 Japan.
Sanjay
S
Pant
Hiroyasu
H
Ohtaka-Saiki
Makoto
M
Takezaki
Andrew D
AD
Scully
Satoshi
S
Hirayama
Toshihiro
T
Tominaga
D002412:Cations / Q000737:chemistry; D004058:Diffusion; D005453:Fluorescence; D007700:Kinetics; D000432:Methanol / Q000737:chemistry*; D009994:Osmolar Concentration; D010269:Paraquat / Q000737:chemistry*; D011166:Porphyrins / Q000737:chemistry*
C529851:5,10,15,20-tetraphenyl- 21H, 23H-porphinetetrasulfonate; D002412:Cations; D011166:Porphyrins; D010269:Paraquat; D000432:Methanol