Anion-controlled electrocrystallization of perylene cation radical salts

Formation of perylene cation radical salts initiated by the electrochemical oxidation was observed directly on a Pt electrode surface using a microsco pic CCD detection system. Depending on the sort of the coexisting anions (X -) as supporting electrolytes, considerable changes were observed in the de position processes in acetonitrile. That is, while no deposition was observ ed with PF6-, the formation of bold needle-Eke black crystals were observed to grow sparsely on the electrode surface in the case with BF4-. In the la tter, the following reduction and re-oxidation experiments revealed that go lden crystals were formed in diverse shapes as a result of the redox reacti ons. On the other hand, in the oxidation of perylene with ClO4-, very thin golden whisker crystals were found to grow proportionally on the whole elec trode 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 gol den micro whisker crystals that grew densely on the electrode. The differen ce in color is expected to be in relation to the redox states of perylene c ation radical salts. (C) 2001 Elsevier Science B.V. All rights reserved.