Gold electrodes modified with 16H,18H-dibenzo[c,l]-7,9-dithia-16,18-diazapentacene for electrocatalytic oxidation of NADH

16H,18H-Dibenzo[c,1]-7,9-dithia-16,18-diazapentacene (DDDP), a new phenothi azine derivative containing two linearly condensed phenothiazine rings, str ongly adsorbs on polyoriented gold resulting in a modified electrode with e lectrocatalytic activity for beta -nicotinamide adenine dinucleotide (NADH) oxidation. Cyclic voltammetry (CV) measurements, performed in aqueous buff er solutions at different PH values, allowed to: (i) estimate the standard heterogeneous rate constants (k(S) approximate to s(-1), at PH 7.0) in the PH range between 4 and 8; (ii) demonstrate the electro catalytic activity o f the investigated compound for NADH oxidation. The second-order electrocat alytic rate constant k(1) was evaluated from the rotating disk electrode (R DE) technique (k(1),([NADH]=0) = 5.0 x 10(3) M-1 s(-1), at PH 7.0). The ele ctrochemical behavior and electrocatalytic activity of DDDP are markedly in fluenced by the intramolecular interaction between the two conjugate phenot hiazine rings. The electrocatalytic activity of DDDP (1e(-), 1H(+) acceptor ) was assigned to its ability to extract rapidly from NADH the first electr on and the proton. (C) 2001 Published by Elsevier Science B.V.