Cationic systems as self-assembled monolayers on gold surfaces

Dipodand tetracations derived from 1-(11-mercaptoundecyl)-4-aza-1-azonia-bi cyclo[2.2.2]octane bromide (1) and substituted bis(bromomethyl)benzenes hav e been self-assembled on a gold surface. Such SAMs are permeable to electro lytes but show some inhibition of redox processes at the electrode. Inhibit ion of oxidation of ferrocyanide is observed, the extent of inhibition vary ing with the structure of the attached species. Oxidation of bromide is enh anced, the extent again depending on the nature of the species, with compou nd 4, derived from 1,4-bis(bromomethyl)-2,5-dimethylbenzene, being the most efficient at both depressing oxidation of ferrocyanide and enhancing the o xidation of bromide. A model to explain these results is advanced. (C) 1999 Elsevier Science S.A. All rights reserved.