Spectral, theoretical, physicochemical and corrosion inhibition studies of ortho-, meta- and para-hydroxyphenyl-benzoylthiourea ligands

Spectral and physicochemical properties of three substituted (ortho-, meta- and para-) hydroxyphenyl-benzoylthiourea ligands namely, 1-benzoyl-3-(2-hydroxy-phenyl)-thiourea (o-HPBT), 1-benzoyl-3-(3-hydroxy-phenyl)-thiourea (m-HPBT) and 1-benzoyl-3-(4-hydroxy phenyl)-thiourea (p-HPBT) were studied. The corresponding structures were described by elemental analysis, infrared spectroscopy, ¹H and ¹³C nuclear magnetic resonance (NMR) and UV spectroscopies. Besides, density functional theory (DFT) computations were conducted to study structures and energetics of the prepared ligands. TD-DFT method was employed to study the electronic states and the results were in notable alignment with the experimental data. Moreover, o-HPBT was studied as a corrosion inhibitor for mild steel (MS) in acidic mediums (1 N HCl and 1 N H₂SO₄). The inhibition efficiency (I) of o-HPBT was increased by rising its concentration attaining maximum value (79.28 %) at 1.00 × 10^-2 M in 1 N H₂SO₄ solution at 30 °C.