Photo- and electro-chemical processes at organic crystal electrodes. II. Oxidation of a solute in water by positive holes from an anthracene crystal

Abstract

Although aqueous electrodes have been used often to discharge positive holes emerging from an anthracene crystal, the mechanism has not yet been elucidated in any one case. We have found that p-anilinobenzenesulphonate (1) prevents all oxidation of the water, itself being oxidized with very nearly 100% efficiency. To oxidize one negative ion, 1.99 ± 0.01 holes are needed. The product was N,N '-(1,1'-biquinone-4,4'-diimine)bisbenzene-p-suphonic acid (2). An induction period before the production appeared in solution and small deficiencies in the 100% oxidation were attributed to adsorption of a monolayer (3.4 x 10¹³ ions cm^-2) of the product ions on the anthracene crystal, agreeing with an expected area of 2.6 nm² for an adsorbed ion. A 1 : 3 complex of iron(1) and 1,l0-phenanthroline gave similar results requiring one electron to oxidize a (+ 2) positive ion with an adsorbed monolayer concentration of 7.3(±:0.1) x 10¹³ ions cm^-1.