In addition, continuous electrochromic behavior was demonstrated upon constant-current electrochemical reduction and subsequent oxidation in CH 2 Cl 2 for 2 2+ (BF 4 -) 2 , which was monitored by UV/Vis spectroscopy. For 2a 2+ (BF 4 -) 2 and 2b 2+ (BF 4 -) 2 , clean electrochromism was observed via radical cation species in both redox processes, and the original spectra were regenerated by electrochemical oxidation of as-prepared biradical species (Figures and). Clean electrochromic behavior is noteworthy even when it is realized by involving the biradical state. Therefore, the stacked geometry can certainly stabilize radical cation and biradical species, due to the effective interaction between planar units, as found in the dications.