Anion-controlled electrocrystallization of perylene cation radical salts

Abstract

Formation of perylene cation radical salts initiated by the electrochemical oxidation was observed directly on a Pt electrode surface using a microscopic CCD detection system. Depending on the sort of the coexisting anions (X −) as supporting electrolytes, considerable changes were observed in the deposition processes in acetonitrile. That is, while no deposition was observed with PF 6 −, the formation of bold needle-like black crystals were observed to grow sparsely on the electrode surface in the case with BF 4 −. In the latter, the following reduction and re-oxidation experiments revealed that golden crystals were formed in diverse shapes as a result of the redox reactions. On the other hand, in the oxidation of perylene with ClO 4 −, very thin golden whisker crystals were found to grow proportionally on the whole electrode surface, and then they became dense in course of time. However, after 1 min, black thin needle-like crystals were initiated to form over the golden micro whisker crystals that grew densely on the electrode. The difference in color is expected to be in relation to the redox states of perylene cation radical salts.