Alkyl chain length effect on experimental density of three iodide anion-based ionic liquid at high-pressure and application of four group contribution estimation methods for ionic liquids density

[Display omitted] •New high-pressure density data for three iodide anion-based ionic liquids.•Alkyl chain length affects ionic liquids’ structural packing efficiency.•Intermolecular forces interactions provoke a crossing point in internal pressure.•Four group contribution estimation methods were used for density estimation. Ionic liquids (ILs) constitute a captivating class of materials that has garnered significant attention from research and industrial applications, being recognized as promising substitutes for organic solvents in industrial processes. Consequently, comprehensive experimental physicochemical characterization, explicitly focusing on density data complemented by computational tools, is imperative. In pursuit of this objective, the present study explores the density behavior, both experimentally and computationally, of three iodide-based ionic liquids under high-pressure and high-temperature (HPHT) conditions. Here, it was studied the alkyl chain impact on density for 1-propyl-3-methylimidazolium iodide ([C3C1Im][I]), 1-butyl-3-methylimidazolium iodide ([C4C1Im][I]), and 1-hexyl-3-methylimidazolium iodide ([C6C1Im][I]) ILs. The vibrating tube method was utilized to determine the density over a range of pressure (P = 0.20 to 100.00 MPa) and temperature (T = 298.15 to 398.15 K). The density of the ionic liquids (ILs) was found to be influenced by the length of the cation alkyl chain, exhibiting the following sequence of increasing density: [C6C1Im][I]