Molecular Interaction between l-Leucine and Glycyl-l-leucine in 1-Decyl-3-methylimidazolium Bromide Solution: Volumetric, Acoustic, and Density Functional Theory Approaches

In order to achieve an optimal design, a comprehensive study at the molecular level between drug molecules and biological membranes is required. Investigation using both computational and experimental methods on the interaction between the ionic liquid 1-decyl-3-methylimidazolium bromide ([C₁₀MIm][Br]) and l-leucine/glycyl-l-leucine was conducted at an experimental pressure of p = 0.1 MPa and a temperature that varied from 288.15 to 318.15 K. The density and speed of sound for mixtures of l-leucine and glycyl-l-leucine with water and [C₁₀MIm][Br] were measured. Through the correlation of the measured parameters using established relationships, the partial molar parameters, such as apparent molar volumes (V_ϕ) and apparent molar isentropic compression (K_ϕ,S), have been calculated. Furthermore, the apparent molar isobaric expansion (ϕ_E⁰) and Hepler’s constant have been determined based on the density and speed of sound data. By obtaining these quantities, we have achieved a more accurate representation of the thermodynamic behavior of the system, providing valuable insights into the interactions and properties of the glycyl dipeptide in the solvent mixtures. Density functional theory was employed to calculate the interaction energies, electrostatic potentials, and FT-IR spectra of the system.