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The photoreduction of 8‐substituted 5‐deazaflavins and the 5‐deazaflavin catalyzed photoreduction of methyl viologen
Author(s) -
Link Paul A. J.,
Van Der Plas Henk C.,
Müller Franz
Publication year - 1988
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570250204
Subject(s) - chemistry , substituent , viologen , photochemistry , steric effects , dimer , kinetics , reactivity (psychology) , medicinal chemistry , catalysis , autocatalysis , electron donor , stereochemistry , organic chemistry , physics , alternative medicine , pathology , quantum mechanics , medicine
Prolonged illumination of 8‐X‐5‐deazaflavins (X = C1, N(CH 3 ) 2 , NH 2 , p ‐NH 2 ‐C 6 H 4 ) in the presence of an electron donor leads to the formation of a 5,5′‐dimer and/or a 6,7‐dihydro compound. The course and rate of these photoreductions were established and discussed in terms of electronic and steric effects, exerted by the substituent at position 8 and the electron donor. Pseudo first‐order kinetics were found to apply to the photoreduction of 8‐X‐5‐deazaflavins (X = Cl, NH 2 , p ‐NH 2 ‐C 6 H 4 ) while the rate of the photoreduction of 8‐X‐5‐deazaflavin (X = N(CH 3 ) 2 ) appeared to contain an autocatalytic element. The catalytic effect of 8‐X‐5‐deazaflavins in the photoreduction of methyl viologen by EDTA was investigated. The substituent effect on the rate of the 8‐X‐5‐deazaflavin mediated photoreduction of methyl viologen by EDTA was found to be comparable with that on the photoreduction rate of 8‐X‐5‐deazaflavin in the presence of EDTA with the exception of 8‐X‐5‐deazaflavin (X = N(CH 3 ) 2 ), which showed a remarkable relative enhancement of the reactivity towards methyl viologen photoreduction.