This study explored the possibility of Schiff-base ligand compound, 2-acetylpyridine 4-ethyl-3thiosemicarbazone (LH) and its organotin(IV) complex (BuSn(L)Cl2) as a corrosion inhibitor for mild steel in 1M hydrochloric acid (HCl) medium. The chemical structures of the synthesised compounds were confirmed by performing elemental analysis, FT-IR, UV-Vis, NMR spectroscopy, and X-ray crystallography diffraction study. The structure showed the LH served as a tridentate (N, N', S) donor to tin through its pyridyl, azomethine nitrogen, and thiolate sulphur. The corrosion inhibition characteristics of the free Schiff-base ligand and its organotin complex were studied by the standard weight loss method. They showed inhibition activity through adsorption, and this phenomenon was found to obey Langmuir adsorption isotherm. The inhibition efficiency of both compounds was found to increase as their concentration was increased from 1 to 3mM, but the efficiency achieved with the tin complex was greater, being 98.98% at 3mM concentration.
The asymmetric unit of the title crystal structure is shown in the figure. Tables 1 and 2 contain details of the measurement method and a list of the atoms including atomic coordinates and displacement parameters.
Source of material3-(2-Bromo-acetyl)-chromen-2-one (0.05 mol) and selenourea (0.05 mol) were dissolved in 5 mL methanol-water (1 : 1) contaning 0.08 g NaF. The mixture was stirred at room temperature for 30 minutes. After the completion of the reaction, water (10 mL) was added to the reaction mixture and extracted with ethyl acetate. The organic layer was dried over anhydrous Na 2 SO4. The solvent was evaporated under reduced pressure and the resulting product was further purified by column chromatography (hexane:ethyl acetate, 7 : 3) [3,4]. Single crystals suitable for X-ray structure analysis were obtained by dissolving the compound in methanol and DMF. Then, the solvents were concentrated using a rotary evaporator. The mixture was cooled to room temperature and allowed to rest overnight. The title compound formed reddish brown parallelepipeds in a yield of 50%.
Experimental detailsThe C-H atoms were constrained to an ideal geometry, with C-H distances of 0.93-0.96 Å. The U iso values of the hydrogen
In the title compound, the dihedral angles between the 1-methyl indole units (A and B) and the benzoic acid moiety (C) are A/B = 64.87 (7), A/C = 80.92 (8) and B/C = 75.05 (8)°. An intramolecular C—H⋯O interaction arising from the methyne group helps to establish the conformation. In the crystal, (8) carboxylic acid inversion dimers linked by pairs of O—H⋯O hydrogen bonds are observed.
Two pyridine-2,6-dicarboxylates each containing butynyl and pentynyl at position 2 and 6 were synthesized by esterification of 2,6-pyridinedicarbonyl dichloride with N-alkyne alcohol. All compounds were characterized by using nuclear magnetic resonance spectroscopy (NMR), infrared spectroscopy (IR) and mass spectrometry (MS) techniques. Crystallographic studies showed that both compounds, 3-dibutynyl pyridine-2,6-dicarboxylate (3a) and 4-dipentynyl pyridine-2,6-dicarboxylate (3b) crystallized in monoclinic system with same space group of C 2/c.
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