Hirshfeld, surface analysis, DFT and corrosion inhibition mechanism of vanillin 4-ethylthiosemicarbazone on mild steel in 1M HCl

• Published in: Moroccan Journal of Chemistry
• Main Author: Baharin N.A.N.K.; Ghazali S.A.I.S.M.; Razak F.I.A.; Sirat S.S.; Tajuddin A.M.; Kamarudin S.R.M.; Dzulkifli N.N.
• Format: Article
• Language: English
• Published: University Mohammed Premier Oujda 2025
• Online Access: https://www.scopus.com/inward/record.uri?eid=2-s2.0-85215371731&doi=10.48317%2fIMIST.PRSM%2fmorjchem-v13i1.50111&partnerID=40&md5=f4f80aff06a9aa547883f9cc4b52ac7c

Vanillin 4-ethyl thiosemicarbazone (V4TSC) was synthesized effectively, and single crystal X-ray diffraction was used to validate its structural structure. The compound establishes a monoclinic crystal structure with the P 1 21/n 1 space group. The following are the V4TSC cell's dimensions and volume: V = 1190.3(10) ų, α = 90°, β = 98.083(18)°, γ = 90°, and a = 8.533(4) Å, b = 8.537(5) Å, and c = 16.504(8) Å. Intramolecular hydrogen bond namely N1—H1…N4 and intermolecular hydrogen bonds which are N1—H1…O1, O2—H2…S1, and N3—H3…S1 stabilize the crystal structure. The Hirshfeld surface was analyzed to investigate intermolecular interactions inside the crystal structure. V4TSC has been shown through weight loss, SEM-EDX, and AFM studies to be a good corrosion inhibitor in HCl. It forms a protective layer on mild steel surfaces by following the Langmuir adsorption isotherm (R² = 0.999) and exhibiting mixed adsorption (-22.638 kJ/mol). Higher inhibitor concentrations increased inhibitory effectiveness at 1 mM with 97.29 %. When mild steel was exposed to the ideal 1.0 mM concentration of V4TSC inhibitors, its surface roughness was considerably lower than it was in the uninhibited solution, as demonstrated by the SEM-EDX and AFM images. Spark emission shows that the composition of the S atom on mild steel in V4TSC increased compared to the blank. The optimal structures (thione and thiol) of the compound were computed using density functional theory (DFT) with the 6-311G++(d, p) basis set and the B3LYP technique. DFT was also examined by assessing the chemical reactivity descriptors, frontier molecular orbitals, and molecular electrostatic potential of V4TSC. Comparing the thione and thiol forms of V4TSC, the research showed that the thione form had a greater inhibitory efficiency. © 2024 School of Science, DUTH. All rights reserved.