Thermophysical Properties of [EMIM][SCN] in Hydroxy-Based Solvents: Combined Experimental and Theoretical Analysis

A comprehensive framework is presented for estimating the thermophysical properties, including densities (ρ), sound velocities (u), and dynamic viscosities (η) of [EMIM]-[SCN], 2-methoxyethanol (MEO), and 1-pentanol (PEN), and binary mixtures ([EMIM]-[SCN] + MEO) and ([EMIM]-[SCN] + PEN) at 1 atm pressure and various temperatures. To understand the molecular interactions and deviations in behavior, properties such as excess molar volumes (V^E ), deviations in isentropic compressibilities (Δκ_s ), excess sound velocity (u ^E ) and dynamic viscosity deviations (Δη) were calculated. The derived parameters were fitted to the Redlich-Kister equation, yielding fitting coefficient parameters (Ai), standard deviations (σ), and correlation coefficients (R²), which indicate the quality and consistency of the experimental data. Fourier transform infrared (FTIR) analysis was conducted to elucidate potential interactions in these binary mixtures. Furthermore, the Prigogine-Flory-Patterson (PFP) theory was used to explain the potential excess-volumetric behavior and to forecast interaction trends in binary mixtures. Additionally, Density Functional Theory (DFT) was employed to study the electronic and intermolecular properties of pure and binary systems in terms of HOMO-LUMO gaps, reduced density gradient (RDG), noncovalent interactions (NCI), electrostatic potential (ESP) maps, and QTAIM analysis. For further analysis, molecular dynamics (MD) simulations were performed, which give density, radial distribution function, mean square displacement (MSD), and self-diffusion coefficient (D). Taken together, these methods provide a detailed understanding of the thermophysical and molecular interactions in binary mixtures.