Substituent effects on ferrocenes in aluminum chloride-butylpyridinium chloride molten-salt mixtures

The visible absorption spectra and reduction potentials of 11 ferrocenes containing electron-withdrawing substituents were determined in an N-n-butylpyridinium chloride-aluminum chloride molten salt. When the substituent(s) on the cyclopentadienyl ring(s) of ferrocene were varied, the reduction potential was caused to range over 1.25 V, and the wavelength for maximum absorption of visible light was varied by nearly 200 nm. These changes are greater than have been observed for similar ferrocenes in other nonaqueous solvents. Evidence is presented for specific interactions of particular ferrocenes with the molten salt.