Abstract
A series of viologens containing 4-n-alkylbenzenesulfonates were synthesized by the metathesis reaction of 4-n-alkylbenzenesulfonic acids or sodium 4-n-alkylbezenesulfonates with the respective viologen dibromide in alcohols. Their chemical structures were characterized by Fourier Transform Infrared, 1H and 13C Nuclear Magnetic Resonance spectra and elemental analysis. Their thermotropic liquid-crystalline (LC) properties were examined by differential scanning calorimetry and polarizing optical microscopy. They formed LC phases above their melting transitions and showed isotropic transitions. As expected, all the viologen salts had excellent stabilities in the temperature range of 278–295 °C as determined by thermogravimetric analysis.
Highlights
The 1,10 -dialkyl-4,40 -bipyridium salts are commonly known as viologens
As a continuation of our research efforts in the ionic liquid crystals (ILCs), we describe the synthesis of a series of symmetric viologen compounds with 4-n-alkylbenzenesulfonates (n = 6, 7, 8, 9, 10, 12, 14, 16, 18); wherein n denotes the carbon atoms in the alkyl chain), determine both their chemical structures by
The thermal stabilities of the viologen salts were determined by thermogravimetric analysis (TGA)
Summary
The 1,10 -dialkyl-4,40 -bipyridium salts are commonly known as viologens. They are an important class of dicationic salts and appropriately called advanced functional materials. The anions to date include bromide, iodide [14,15], − BF4 , − PF6 [22,24], − OTf, − SCN, − NTf2 , 4-n-alkylsulfonates [24], 4-n-alkylbenzenesulfonates [16], and 3,4,5-tri-n-dodecyloxybenzenesulfonate [23] Their use in energy-related systems stemming from the unique properties of redox properties as well as LC properties of viologen moieties has given the boost for the exploration of this class of materials. In contrast to other anions, reports of ILCs on these anions are relatively less, studied [16]
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