Reversible polycolour change of viologens from violet through transparent to white

• Published in: Electrochimica acta Vol. 55; no. 1; pp. 165 - 170
• Main Authors: Hoshino, Katsuyoshi, Oikawa, Yosuke, Sakabe, Ichiro, Komatsu, Toshiki
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 15.12.2009; Elsevier
• Subjects: Chemistry; Electrochemistry; Electronic paper; Exact sciences and technology; General and physical chemistry; Miscellaneous (electroosmosis, electrophoresis, electrochromism, electrocrystallization, ...); Polyelectrochromism; Tribromide; Viologen; Viologen complex; Viologen complex; Tribromide; Viologen; Electronic paper; Polyelectrochromism; Scanning electron microscopy; Organic cation; Indium tin oxide electrode; Iminium compounds; Transition metal; Electrochromism; X ray; Surface structure; Electrodes; Alkali metal Halides; Medium effect; Platinum; Electrode reaction; Morphology; Photoelectron spectrometry; Aqueous solution; Organic dication; Ultraviolet visible spectrometry
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2009.08.029

The electrochromic properties of 1,1′-dibenzyl-4,4′-bipyridinium and 1,1′-diheptyl-4,4′-bipyridinium were investigated in the presence of MBr (M = Li +, Na +, and K +). The cyclic voltammograms of these viologens showed a white-coloured state in addition to the usual violet one-electron reduction state and the colourless divalent state. Chemical analyses (FT-IR and XPS spectra) of the white film and some control experiments with different supporting electrolytes, MX (X = Cl − and I −), revealed that the viologens formed water-insoluble ion pairs with tribromide generated by the electrooxidation of monobromide to produce a white film. The film was reversibly decolourized electrochemically to the initial transparent state, providing the polyelectrochromism using the simple viologen/MBr systems. The colouration efficiencies for the violet and the white-coloured states were 170 cm 2/C and 104 cm 2/C, respectively.