Acid-catalysed reduction of flavin analogues by an NADH model compound, 10-methyl-9,10-dihydroacridine and cis-dialkylcobalt(III) complexes
- 1 January 1989
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 8,p. 1047-1053
- https://doi.org/10.1039/p29890001047
Abstract
An acid-stable NADH model compound, 10-methyl-9,10-dihydroacridine (AcrH2)(3), and cis-dialkylcobalt(III) complexes, cis-[R2Co(bipy)2]+(R = Me, Et; bipy = 2,2′-bipyridine), can reduce flavin analogues {Fl: 3-methyl-l0-phenylbenzo[g]pteridine-2(1H),4(3H)-dione (1) and riboflavin (2)}, efficiently in the presence of perchloric acid (HClO4) in acetonitrile (MeCN) at 298 K to yield the corresponding dihydroflavin radical cations (FIH2 +˙). Essentially, no reaction occurs in the absence of HClO4 under the same conditions. The radical cations (FIH2 +˙) formed are very stable to oxygen in the presence of HClO4 in MeCN. Large primary kinetic isotope effects [kH/kD 9.6 ± 0.8 and 9.9 ± 0.8 for (1) and (2), respectively] have been observed for the formation of FIH2 +˙, indicating that hydride transfer from AcrH2 to the protonated flavins (FIH+) to give the dihydroflavins (FIH2) is followed by fast comproportionation between FIH2 and FIH+ to yield FIH2 +˙ in the presence of HClO4 in MeCN. The reaction mechanisms of hydride transfer from AcrH2 to FIH+ are compared with the acid-catalysed electron-transfer reactions from cis-[R2Co(bipy)2]+ to FIH+.Keywords
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