Drastic influence of amide functionality and alkyl chain length dependent physical, thermal and structural properties of new pyridinium-amide cation based biodegradable room temperature ionic liquids

•Here in we report a series new amide functionalized room temperature ionic liquid (RTIL) based on pyridinium core moiety as cation and conformationally flexible NTf2 as anion.•Raman spectroscopic studies of structure indicates the dependence of NTf2 anion conformation on the size of alkyl chain length.•Considering the fact, alkyl chain creates hydrophobic core in nanostructured ionic liquids, our data project an interaction between anionic core with hydrophobic region of cation, which is not anticipated till date.•Drastic changes in thermo-physical properties on amide functionalization is found to be interesting.•In addition, varying the alkyl chain length attached to cation, one can tune the thermo-physical properties to a significant extent.