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SYNTHESES AND PHOTOREDOX PROPERTIES OF POLYELECTROLYTES FUNCTIONALIZED WITH 5‐DEAZAFLAVIN
Author(s) -
Morishima Yotaro,
Kitani Toru,
Kobayashi Takaomi,
Saeki Yasuhiro,
Nozakura Shunichi,
Ohno Takeshi,
Kato Shunji
Publication year - 1985
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1985.tb01595.x
Subject(s) - polyelectrolyte , chemistry , photosensitizer , electron transfer , reaction rate constant , radical , quantum yield , viologen , photochemistry , triplet state , excited state , polymer , kinetics , molecule , organic chemistry , fluorescence , physics , quantum mechanics , nuclear physics
— Anionic polyelectrolytes functionalized with the 5‐deazaflavin group (dFl) were synthesized. The lifetime of the triplet excited dFl in the polyelectrolytes with a 2‐mol% dFl content (AdFl‐2) was about 10 times longer than that of a low molecular weight analog (AdFl‐M). 2‐Mercaptoethanol (RSH) reduced the triplet dFl with the rate constant of k red = 2.01 × 10 8 M −1 s −1 for AdFl‐M and k red = 4.4 × 10 7 M −1 s −1 for AdFl‐2. A zwitterionic viologen (SPV) oxidized the triplet dFl with the rate constant of k red = 3.69 × 10 9 M −1 s −1 for AdFl‐M and k ox = 7.4 × 10 8 M −1 s −1 for AdFl‐2. The smaller rate constants for the polymer system were discussed in terms of the hindering effect of the macromolecular microenvironment. The back electron transfer was shown to be drastically slowed in the AdFl‐2‐SPV system as a result of the intensive electrostatic effect of the polyelectrolytes. The buildup of the viologen radicals was studied under the steady‐state illumination of the three component systems including viologen and RSH. The dFl group was demonstrated to serve as a very efficient photosensitizer in the oxidative cycle in case back electron transfer was retarded. This is the case of the AdFl‐2‐SPV system which gave the quantum yield of about 0.4 for the SPV − buildup. By comparison, the AdFl‐2‐MV 2 + system resulted in a much slower buildup of MV +radicals.