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Novel Bipyridinium Ionic Liquids as Liquid Electrochromic Devices
Author(s) -
Jordão Noémi,
Cabrita Luis,
Pina Fernando,
Branco Luís C.
Publication year - 2014
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201304451
Subject(s) - ionic liquid , electrochromism , cyclic voltammetry , differential scanning calorimetry , bromide , inorganic chemistry , chemistry , iodide , electrochromic devices , glass transition , differential pulse voltammetry , imide , electrochemistry , materials science , analytical chemistry (journal) , polymer chemistry , organic chemistry , polymer , electrode , thermodynamics , physics , catalysis
Abstract Novel mono and dialkylbipyridinium (viologens) cations combined with iodide, bromide, or bis(trifluoromethanesulfonyl)imide [NTf 2 ] as anions were developed. Selective alkylation synthetic methodologies were optimized in order to obtain the desired salts in moderate to high yields and higher purities. All prepared mono‐ and dialkylbipyridinium salts were completely characterized by 1 H, 13 C, and 19 F NMR spectroscopy, Fourier‐transform IR spectroscopy, and elemental analysis (in the case of NTf 2 salts). Melting points, glass transition temperatures by differential scanning calorimetry (DSC) studies, and decomposition temperatures were also checked for different prepared organic salts. Viscosities at specific temperatures and activation energies were determined by rheological studies (including viscosity dependence with temperature in heating and cooling processes). Electrochemical studies based on cyclic voltammetry (CV), differential pulsed voltammetry (DPV), and square‐wave voltammetry (SWV) were performed in order to determine the redox potential as well as evaluate reversibility behavior of the novel bipyridinium salts. As proof of concept, we developed a reversible liquid electrochromic device in the form of a U‐tube system, the most promising dialkylbipyridinium‐NTf 2 ionic liquid being used as the electrochromic material and the room‐temperature ionic liquid (RTIL), 1‐ethyl‐3‐methylimidazolium bis(trifluoromethanesulfonyl)‐imide [EMIM][NTf 2 ], as a stable and efficient electrolyte.