Solution, Thermal and Optical Properties of Bis(pyridinium salt)s as Ionic Liquids

Authors

Tae Soo Jo, University of Nevada, Las VegasFollow
Jung Jae Koh, University of Nevada, Las VegasFollow
Haesook Han, University of Nevada, Las VegasFollow
Pradip K. Bhowmik, University of Nevada, Las VegasFollow

Document Type

Article

Publication Date

5-15-2013

Publication Title

Materials Chemistry and Physics

Volume

139

Issue

2-3

First page number:

901

Last page number:

910

Abstract

Bis(pyridinium salt)s containing different alkyl chain lengths and various organic counterions were prepared by the ring-transmutation reaction of bis(pyrylium tosylate) with aliphatic amines in dimethyl sulfoxide at 130–135 °C for 18 h and their tosylate counterions were exchanged to other anions such as triflimide, methyl orange, and dioctyl sulfosuccinate by the metathesis reaction in a common organic solvent. Their chemical structures were established by using ¹H, ¹⁹F, and ¹³C NMR spectra. The thermal properties of bis(pyridinium salt)s were studied by DSC and TGA measurements. Some of the dicationic salts provided low melting points below 100 °C and some of them displayed amorphous properties. Polarized optical microscopy studies revealed the crystal structures prior to melting temperatures in some cases. Their optical properties were examined by using UV–Vis and photoluminescent spectrometers; and they emitted blue light both in the solution and solid states regardless of their microstructures, counterions, and the polarity of organic solvents. However, most of these salts exhibited hypsochromic shifts in their emission peaks in the solid state when compared with those of their solution spectra. Due to unique properties of methyl orange anion as a pH indicator, two of the salts showed different color change in varying concentrations of triflic acid in common organic solvents, demonstrating their potential use as an acid sensor in methanol, acetonitrile and acetone.

Keywords

Differential scanning calorimetry (DSC); Gravimetric analysis; Luminescence; Nuclear magnetic resonance; NMR; Salts; Thermogravimetric analysis (TGA); Thermogravimetry

Disciplines

Analytical Chemistry | Chemistry

Language

English

Permissions

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Repository Citation

Jo, T., Koh, J. J., Han, H., Bhowmik, P. K. (2013). Solution, Thermal and Optical Properties of Bis(pyridinium salt)s as Ionic Liquids. Materials Chemistry and Physics, 139(2-3), 901-910.