Voltammetric and in Situ Spectroscopic Investigations on the Redox Processes of Trioxotriangulene Neutral Radicals on Graphite Electrodes

To investigate the microscopic electrochemical dynamics of a stable trioxotriangulene (TOT) organic neutral π-radical on a graphite electrode surface, voltammetric and in situ infrared (IR) spectroelectrochemical studies were conducted using electrolyte solutions containing TOT monoanions. Upright columnar crystals (face-on alignment) of the TOT neutral radical were preferentially formed and dissolved in a rather reversible manner in the electrolyte with a low concentration of TOT monoanion under electrochemical conditions; however, more flat-lying columnar crystals (edge-on alignment) were formed in a higher concentration electrolyte. The flat-lying crystals remained on the graphite surface even at a fully reduced potential, owing to the lack of direct π-π interactions between the molecules and the graphite electrode. In situ IR attenuated total reflectance spectroscopy analyses successfully characterized the alignment of the columnar crystals of the TOT neutral radicals and their electrochemical behaviors, including the possible origins of the irreversible redox reaction of TOT on the graphite electrode.