A novel 1,1’-bis-[2-(1H-indole-3-yl)-ethyl]-4,4′-bipyridinium diperchlorate (viologen) for a high contrast electrochromic device

Ghosh, Arnab and M, Deepa (2014) A novel 1,1’-bis-[2-(1H-indole-3-yl)-ethyl]-4,4′-bipyridinium diperchlorate (viologen) for a high contrast electrochromic device. Masters thesis, Indian Institute of Technology, Hyderabad.

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Abstract

A new organic electrochromic material, 1,1’-bis-[2-(1H-indole-3-yl)-ethyl]-4,4′-bipyridinium diperchlorate (viologen) was synthesized by di-quaternization of 4,4′-bipyridyl using 3-(2-bromoethyl)-indole under the assistance of microwave irradiation with high yields and in short reaction times. The compound (IEV) was characterized by 1H-NMR, 13C-NMR and FTIR spectroscopic methods. Thermal decomposition temperature of indole viologen perchlorate is above 3000C. An electrochromic device, containing IEV salt in N,N-Dimethylformamide (DMF) and 1-ethyl-3-methylimidazolium bis-(trifluoromethylsulfonyl)-imide (ionic liquid) as electrolyte was constructed, where Prussian blue was used as counter electrode. IEV is a cathodically coloring organic electrochromic material and thus the device underwent reversible transitions between transparent and deep blue hues; the color change was accompanied by an excellent optical contrast (57% at 605 nm), a large coloration efficiency of 533 cm2 C-1 at 605 nm and switching times of 2 s. The device was subjected to repetitive switching between the colored and bleached states and was found that almost no loss in redox activity up to 2000 cycles, ratifying its suitability for electrochromic window/display applications.

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