Probing aqueous diclofenac potassium: Unveiling molecular interactions through dielectric relaxation spectroscopy and MD simulation

• Published in: Journal of molecular liquids Vol. 414; p. 126118
• Main Authors: Karakthala, J.B., Vankar, H.P., Rana, V.A., Dey, S.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15-11-2024
• Subjects: Diclofenac potassium; Dielectric relaxation spectroscopy; Electrolyte; Hydrogen bond; MD simulation; Stability; MD simulation; Dielectric relaxation spectroscopy; Stability; Diclofenac potassium; Electrolyte; Hydrogen bond
• ISSN: 0167-7322
• DOI: 10.1016/j.molliq.2024.126118

•Dielectric spectra of aqueous DK reveal three relaxation processes: EP, normal (n) and alpha (α) relaxation.•Stokes relation fails to hold strictly to K+ cation in aqueous solutions of DK.•Violation of Stokes law results from the ion’s electric field interaction with the solvent’s dielectric relaxation.•DK’s ionic diffusion in water isn’t governed by chain motion but by local segmental motion.•The average number of H-bond formations between solute and solvent remains constant.
Diclofenac potassium (DK) is a salt and undergoes ionization in an aqueous environment. The detailed information about the molecular structure and interactions of such aqueous ionic solutions holds substantial significance in the field of pharmaceutics. This comprehension facilitates the enhancement of pharmaceutical formulations, leading to improved bioavailability, stability, and therapeutic efficacy. It also contributes to the optimization of drug delivery systems. Molecular interactions in the aqueous solutions of DK were studied using dielectric relaxation spectroscopy (DRS) and molecular dynamic (MD) simulation. In DRS, complex dielectric permittivity, ε∗(f) for aqueous solutions of DK of varying concentrations were measured in the frequency range of 20 Hz to 2 MHz at five different temperatures ranging from 303.15 K to 323.15 K. Complex ac conductivity, σ∗(f) and dc conductivity (σdc) were determined from the complex dielectric permittivity. The effect of concentration and temperature on complex permittivity and allied parameters are discussed. The dielectric spectra of aqueous DK reveal dual relaxation processes i.e., normal (n) relaxation and alpha (α) relaxation. The dielectric strength is predominant for α-process and n-process in the low (0 < X ≤ 0.0299) and high (0.029 < X ≤ 0.0822) concentration range respectively. Moreover, Stoke’s relation between dielectric relaxation time, ion mobility and viscosity of the aqueous solutions is discussed. MD simulation at 303.15 K temperature has also been conducted to get additional information on molecular interactions between DK and/or H2O molecules through hydrogen bonding (HB).