Effects of spacer-chain length on the photoelectrochemical responses of monolayer assemblies with ruthenium tris(2,2′-bipyridine) - viologen linked disulfides

Abstract

Photochemical and photoelectrochemical properties of ruthenium tris(2,2′-bipyridine) (Ru 2+)-viologen (V 2+) linked disulfides [RuCnVC 6S] 2 ( n (number of methylene groups)=3, 7) with different spacer-chain lengths and Ru 2+ disulfides [RuC m S] 2 ( m=13, 17) were compared. The luminescence intensity in CH 3CN was in the order of [RuC 13S] 2≈[ RuC 17 S] 2>[ RuC 7 VC 6 S] 2⪢[ RuC 3 VC 6 S] 2 , implying efficient photoinduced electron-transfer between Ru 2+ and V 2+ moieties in the linked compounds. The monolayer assembly of the compound was fabricated on a gold surface. In the presence of triethanolamine, the anodic photocurrent was clearly observed from the RuC n VC 6S/Au ( n=3, 7) electrode (gold electrode modified with [RuCnVC 6S] 2), and its intensity was substantially larger for n=7 than for n=3. Photocurrent action spectra for the RuC n VC 6S/Au ( n=3, 7) electrodes were well correlated with the corresponding electronic absorption spectra in solution. The photocurrent from the RuC 7VC 6S/Au electrode was reduced more effectively by the coexistence of a water-soluble viologen as compared with the RuC 3VC 6S/Au electrode. The photocurrent from the RuC m S/Au ( m=13, 17) electrode was very small. The results suggest that the spacer-chain length between the Ru 2+ and the V 2+ moieties profoundly affects the Ru 2+-sensitized photocurrent.