Stabilizing radical cation and dication of a tetrathiafulvalene derivative by a weakly coordinating anion
After the chemical oxidation of the neutral tetrakis(methylthio) tetrathiafulvalene (TMT-TTF, 1) by specific oxidation agents with weakly coordinating anion, [Al(ORF)4]- [ORF = OC(CF3)3], the radical cation TMT-TTF•+ (1•+) and dication TMT-TTF2+ (12+) were successfully stabilized and isolated. All the compounds are well-soluble in some solvents and have been systematically investigated by absorption spectra, 1H NMR, electron paramagnetic resonance (EPR) measurements. Their crystal structures and electronic properties have been studied in conjunction with theoretical calculation. The synthetic approach for chemical oxidation by specific salts of weakly coordinating anions is useful for stable radical cations of tetrathiafulvalene (TTF) and its derivatives in both solution and solid state, which will extend the further research, including structure-property relations on stable radicals for TTF derivatives and new functional materials based on them.