Faraday effect of imidazole and pyrrolidine and their N-alkyl derivatives

Abstract

Ionic liquids (ILs) are of great interest because of their spectacular physicochemical properties and applications. Recent research suggests the possible application of magnetic ILs (MILs) in photonics. That fact motivated us to start with magnetooptical (MO) studies on the precursor compounds of most known ILs based on imidazolium and pyrrolidinium cations to gain information allowed tailoring the magnitude of the Faraday effect (FE) in this kind of materials. Herein, we present results of the magnetooptical rotatory dispersion (MORD) and refractive index (RI). The MORD spectrum was described by the Faraday B-terms according to the Serber theory. The respective parameters describing the FE and RI were evaluated and correlated with the position of the experimentally observed optical edge for the compounds studied. The Verdet constant varies very slightly with temperature as expected for diamagnetic materials. Comparison measurements for other precursors of heterocyclic ring compounds of cations of Ils, i.e. pyridine, piperidine, pyrazole, and pyrrole, as well as their methyl derivatives, were also made. The results obtained allow to establish the empirical relation between the Verdet constant and the N-alkyl chain length, as well as the diamagnetic susceptibility and optical polarizability, which were evaluated for studied materials. Comparison of the obtained results with the data for benzene and cyclohexane allowed for the correlation of the V constant with the degree of aromaticity of the studied compounds. RI was also correlated with the N-alkyl chain length. The developed relations will be useful for designing new MILs and tailoring their MO properties.