Electrochemical and electrochromic properties of octathio[8]circulene thin films in ionic liquids.

We studied the electrochemistry of the thin films of octathio[8]circulene (1) in an ionic liquid, N,N-diethyl-N-methyl(2-methoxyethyl) ammonium bis(trifluoromethylsulfonyl)imide (DEME-TFSI). The compound 1 exhibited simultaneous two-electron oxidation in the oxidation scan and then stepwise reductions to the original neutral state, showing significant electrochromism. This color change was well-interpreted in terms of the n-pi transition that is allowed by the vacancy in the HOMO of 1 after electrochemical oxidation.