Water-soluble 2-hydroxypropyl-beta-cyclodextrin (Hp-beta-CyD), a cyclic and nonreducing oligosaccharide was used to enclose a hydrophobic guest molecule 1,1’-dimethylferrocene (DMF) to form a water-soluble yellow complex. At high concentrations (300 mM), Hp-beta-CyD enclosed up to 100 mM DMF. The yellow complex was electrochemically oxidized (platinum vs Ag/AgCl poised at +450 mV) to form a blue dye, 1,1’-dimethylferricinium (DMF(+)). This is a one-electron transfer process and the ferricinium cation formed exhibited an absorption peak at 650 nm. The concentrated DMF(+) was stable for at least 4 mo at 4 degrees C and insensitive to a wide pH variation (pH 2-11).