Redox-Switched Amphiphiles: Oxidized Ferrocene Derivatives Form Stable Vesicles When Either One or Two Alkyl Tails Are Present

Thirty ferrocene derivatives were prepared and their ability to form vesicles in aqueous solution when oxidized was assessed. The compounds included alkyl ferrocenylmethyl ether derivatives of the form C10H9FeCH2OR in which R=octyl, dodecyl, tetradecyl, hexadecyl, octadecyl and eicosanyl. One single-tailed amine derivative, C10H9FeCH2NR2, R=octadecyl, was studied. Alkylferrocene derivatives had the form C10H9FeR in which R=butyl, decyl, tetradecyl, hexadecyl, octadecyl, eicosanyl and docosanyl. Sixteen symmetrical 1,1′-disubstituted ferrocenes were also studied. Three ethers were of the form C10H8Fe-1,1′-(CH2OR),2, R=tetradecyl, hexadecyl and octadecyl. Four corresponding dialkyl derivatives of the form C10H8Fe-1,1′-R2, R=decyl, tetradecyl, hexadecyl and octadecyl, were assessed. Finally, a range of 1,1′-disubstituted ferrocene derivatives were analyzed. These all had the form C10H8Fe-1,1′-(COR)2, for which R has the following identities: octyl, tridecyl, pentadecyl and heptadecyl (ketones); heptadecyloxy, 3-cholesteryl and 3-cholestanyl (esters); and two amides, R=NHC18H37 and N(C18H37)2. The alkyl and ether derivatives could be readily oxidized and formed vesicular aggregates upon sonication. The ketones, esters and amides could be oxidized but the ferricenium derivatives did not form stable aggregates. An interesting observation is that the aggregates formed were vesicular whether the ferrocene derivative had one or two alkyl tails.