Abstract

The study described the preparation and characterization of thiophene/pyrazine Schiff base, (E)-N-{(thiophene-2-yl)methylene}pyrazine-2-carboxamide (HL) using melting point and micro (CHN) analysis; vibrational, nuclear magnetic resonance (¹H- and ¹³C-NMR) and electronic (UV–Vis) spectroscopies. HL was also studied for adsorption and corrosion properties. The spectral data were consistent with tridentate bonding nature and enolimine tautomeric arrangement within the ligand assemblage giving credibility to its formation. Density functional theory (DFT) calculations correlated the investigational data, while its percentage inhibition efficiency (IE, %) increased with rise in concentration though declined with increase in temperature (T). The latter indicate that the inhibition proficiency (IP) with T was mixed adsorption, with physisorption dominating the corrosion inhibition process. Similarly, the adsorption of HL on the mild steel (ms) obeys Langmuir adsorption isotherm. However, the negative sign of \(\Delta G_{{{\text{ads}}}}^{^\circ }\) and \(\Delta H_{{{\text{ads}}}}^{^\circ }\) designates that HL adsorption on the ms surface in 1.0 M HCl was instantaneous and exothermic correspondingly. Furthermore, the scanning electron microscopy (SEM) data corroborates that HL hinders ms corrosion through the formation of protective layers on ms surfaces.

中文翻译：

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（E）-N-{-（噻吩-2-基）亚甲基}吡嗪-2-羧酰胺席夫碱配体的制备，光谱表征和缓蚀性能

摘要

该研究描述了噻吩/吡嗪席夫碱，（E）-N -{（噻吩-2-基）亚甲基}吡嗪-2-甲酰胺（HL）的制备和表征。振动，核磁共振（¹ H和¹³ C-NMR）和电子（UV-Vis）光谱。还研究了HL的吸附和腐蚀性能。光谱数据与三齿键合性质和配体组合物中的烯丙胺互变异构体排列相符，从而为其形成提供了可信度。密度泛函理论（DFT）的计算与研究数据相关联，而其抑制效率的百分比（IE，％）随浓度的升高而增加，而随温度的升高而降低（T）。后者表明对T的抑制能力（IP）是混合吸附，而物理吸附在腐蚀抑制过程中占主导地位。同样，HL在低碳钢（ms）上的吸附遵循Langmuir吸附等温线。但是，\（\ Delta G _ {{{text {ads}}}} ^ {^ \ circ} \和\（\ Delta H _ {{{text {ads}}}} ^ {^的负号\ circ} \）表示HL在1.0 M HCl中的ms表面上的HL吸附是瞬时的并且相应地放热。此外，扫描电子显微镜（SEM）数据证实HL通过在ms表面上形成保护层而阻碍了ms腐蚀。