A multi-faceted study combining quantum chemical, Hammett parameters, and antibacterial assessment for imidazole:...

Stringent environmental regulations drive the quest for green corrosion inhibitors (greenish), with ionic liquids being prime candidates due to their high stability and low volatility and non-flammability. The present work investigates the synthesis, characterization, and corrosion inhibition performance of green ionic liquids based (ILs) on imidazole. The newly synthesized 1-acetyl-3-benzoyl-1H-imidazol-3-ium derivatives (ACIM), were successfully characterized. Their structures were validated using Fourier transform infrared spectroscopy (FT-IR), ¹H nuclear magnetic resonance (¹H NMR), Carbon-13 (¹³C NMR) and Mass spectrometry (MS). Their corrosion inhibition performance in 8 M H₃PO₄ was evaluated using Galvanostatic polarization and weight loss methods. We measured the limiting current value and the mass transfer rate which revealing excellent protection efficiency for ACIM-OMe (81.08% at 20.58 × 10⁻⁵ M, 298 K). Thermodynamic parameters confirmed spontaneous adsorption, evidenced by negative ΔG_ads values (- 29.77 to - 38.26 kJ mol⁻¹). Based on the typical energy range of - 20 to - 40 kJ mol⁻¹, the mechanism is interpreted as mixed, involving both physical (electrostatic) and chemical (coordinate bonding) interactions. This aligns with the El-Awady's adsorption isotherm model. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS) were employed. These techniques were used to analyze and visualize the modifications of the CSs' surface following ACIM adsorption. Atomic absorption spectroscopy (AAS) confirmed the inhibitor's effectiveness, showing a 77.17% efficiency for ACIM-OMe based on reduced Fe²⁺ ion concentration in solution. Antibacterial testing revealed that only ACIM-H showed measurable antibacterial activity against Salmonella (positive inhibition zone), though it was less potent than the Kanamycin standard. Additionally, the substituent groups of ACIM derivatives can impact the inhibitors' coordination ability and binding potential in the corrosion process. The influence of these substituent groups on the inhibition efficiency was quantitatively rationalized and correlated using Hammett (σ) and Taft dual parameter (σ*), respectively. Hammett analysis of the meta/para-substituted derivatives confirmed that inhibition efficiency increases with electron-donating ability, evidenced by a negative reaction constant (ρ = - 0.313). Complementing the experimental work, theoretical studies using molecular dynamics (MD) and detailed density functional theory (DFT) successfully modeled the adsorption and surface interactions of ACIM on CS. Finally, theoretical insights align with the experimental findings.