Electrocrystallisation of organic superconductors

Electrocrystallization allows high-purity materials to be reproducibly obtained only if all materials and chemicals involved are properly
purified beforehand. Hence, the PF₆^- anion for example enters in the electrocrystallization process as a tetrabutylammonium salt which is soluble in a solvent like tetrahydrofuran, THF. One electron is removed from every neutral TMTSF in the anode compartment being oxidized by the current passing through the cell leading in turn to the cation radical TMTSF⁺. Then, two cation radicals combining with one anion of the electrolyte give rise to the simple salt (TMTSF)₂PF₆ which precipitates at the anode as a non soluble molecular salt. This accelerated video (x 20 000) shows how electrocrystallization proceeds, leading to centimeters long high quality single crystals.

Filmed at Orsay, from A. Moradpour's laboratory.