Ferrocene-naphthoquinone

The applicability of the Marcus equation (Eq. 14) to MCET reactions was examined using a ferrocene-naphthoquinone dyad (Fc—NQ) as discussed below (Scheme 19)(121,122). No ET from the Fc to NQ moiety occurs in Fc—NQ with a... 

The benzannulation approach has been applied to aromatic molecules of biological interest. Alkynes bearing porphyrin (for example 37) [51a, 51b], ferrocene (for example 39) [51c], and carbohydrate functionalities [51d, 51e] have been incorporated into the (hydro)quinone skeleton, as demonstrated for porphyrinyl and ferrocenyl naphthoquinones 38 and 40 (Scheme 18). 

Scheme 20. The M" —promoted intramolecular ET in a ferrocene—1,4-naphthoquinone (Fc—NQ) dyad (122).

The photoreaction of 2-substituted-1,4-naphthoquinones is accelerated by ionic surfactants but suppressed by cationic ones. Conversely, the flash photolysis of an amphipathic dodecylcarboxamide derivative of a pyridine—ruthenium(ii) complex gives the highest yield for photoreduction in cationic micelles.Anionic micelles increase electron transfer from iron(n) to iron(iii) by ca. 10 —and also the oxidation of ferrocenes by iron(in), but inhibit the oxidation by ferrocyanide. 

Twelve quinone derivatives and three ferrocene derivatives were examined. Their cyclic voltammograms were measured with a film-coated GOD (0.5 Mg) CPE without mixed-in mediator immersed in the basal solution containing 1 mmol/dm mediator. However, for some mediators, such as tetra-methyl p-benzoquinone, 1,2-naphthoquinone, 1,4-naphthoquinone, ferrocene, and 1,1 -dimethyl-ferrocene a saturated solution (generally, of low solubility) was used. Figures 5 and 6 show the cyclic voltammograms of 2,6-dichoro-p-benzoquinone and BQ. The mid-point potential, Emid, was obtained from the cathodic and anodic peak potentials, Epc and Epa, respectively, by Emid (Epc+Epa)/2. All compounds examined were active as electron transfer mediators for bioelectrocatalysis with the GOD CPEs with mixed-in mediator (usually mn = 5%), except tetramethyl-p-benzoquinone (that is. 

---