Synthesis, self-aggregation, thermal stability and cytotoxicity trends of alkyloxypropoxycyclohexane based pyridinium ionic liquids

Abstract

New ether-functionalized pyridinium ionic liquids (ILs) has been synthesized by simple methodology and described by different spectroscopic techniques. Presence of two positional isomers has been confirmed with the help of NMR spectroscopy. The critical micelle concentration and other surface parameters of these ILs were deduced by conductivity, surface tension and fluorescence method. A collection of useful physical parameters i.e. critical micelle concentration (cmc), surface tension accomplished at cmc (γcmc), effectiveness of diminution in surface tension (Πcmc), maximum surface excess concentration (Ʈmax) and minimum surface area per molecule (Amin) at the air–water interface were also estimated. The average size of aggregates formed by investigated pyridinium ILs have been well examined by dynamic light scattering (DLS) experiments. The thermal degradation analysis of the present ILs has also been suggested that these ILs possessed thermal stability ranges from 200 °C to 240 °C. The investigated ILs have also been tested by MTT assay (3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide) on the C6 glioma cell line and found to revealed very low cytotoxicity in the concentration range required for biomedical applications. Such a low cytotoxicity of present ILs opens several new applications in the many biological purposes like drug and gene delivery agents. The physical study of investigated ILs indicate that the presence of ether functionality and varying hydrophobic chain length significantly altered the physicochemical properties of these pyridinium ILs than related to earlier synthesized N-(cyclohexanoxycarbonylmethyl) and 3-Cyclohexyloxy-2-Hydroxypropyl Pyridinium and Imidazolium surface active ILs.