Organic, inorganic, mediators redox couples

For electrodes based on conducting organic charge-transfer salts such as TTF + TCNQ (a complex of the radical cation of tetrathiafulvalene and the radical anion tetracyano-p-quinodimethane) or NMP +TCNQ " (N-methylphenaziniumtetracyano-p-quinodimethane), direct [155, 169] and mediated [154] electron transfer mechanisms have been described. In analogy with the theory of outer-sphere electron transfer [170], Kulys and co-workers [118,171] have developed a mathematical model which permits to evaluate the depth of the active site of some oxidoreductases from the steric requirements of inorganic redox couples (Table 14-4). 

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