Department of Chemistry, College of Science, Taif University, P.O. Box 11099, Taif 21944, Saudi Arabia.
Chemistry Department, Faculty of Science, New Valley University, Kharga 72511, Egypt.
Molecules. 2022 Sep 5;27(17):5733. doi: 10.3390/molecules27175733.
Novel cyano-benzylidene xanthene derivatives were synthesized using one-pot and condensation reactions. A diprotic Brønsted acid (i.e., oxalic acid) was used as an effective catalyst for the promotion of the synthesis process of the new starting xanthene-aldehyde compound. Different xanthene concentrations (ca. 0.1-2.0 mM) were applied as corrosion inhibitors to control the alkaline uniform corrosion of aluminum. Measurements were conducted in 1.0 M NaOH solution using Tafel extrapolation and linear polarization resistance (LPR) methods. The investigated xanthenes acted as mixed-type inhibitors that primarily affect the anodic process. Their inhibition efficiency values were enhanced with inhibitor concentration, and varied according to their chemical structures. At a concentration of 2.0 mM, the best-performing studied xanthene derivative recorded maximum inhibition efficiency values of 98.9% (calculated via the Tafel extrapolation method) and 98.4% (estimated via the LPR method). Scanning electron microscopy (SEM) was used to examine the morphology of the corroded and inhibited aluminum surfaces, revealing strong inhibitory action of each studied compound. High-resolution X-ray photoelectron spectroscopy (XPS) profiles validated the inhibitor compounds' adsorption on the Al surface. Density functional theory (DFT) and Monte Carlo simulations were applied to investigate the distinction of the anticorrosive behavior among the studied xanthenes toward the Al (111) surface. The non-planarity of xanthenes and the presence of the nitrile group were the key players in the adsorption process. A match between the experimental and theoretical findings was evidenced.
新型氰基苄叉氧杂蒽衍生物通过一锅和缩合反应合成。使用双质子布朗斯台德酸（即草酸）作为有效催化剂，促进新型起始氧杂蒽-醛化合物的合成过程。不同的氧杂蒽浓度（约 0.1-2.0 mM）作为缓蚀剂应用于控制铝的碱性均匀腐蚀。在 1.0 M NaOH 溶液中使用塔菲尔外推法和线性极化电阻（LPR）方法进行测量。所研究的氧杂蒽作为混合类型抑制剂，主要影响阳极过程。它们的抑制效率值随抑制剂浓度的增加而提高，并根据其化学结构而变化。在 2.0 mM 的浓度下，表现最好的研究的氧杂蒽衍生物记录了 98.9%的最大抑制效率值（通过塔菲尔外推法计算）和 98.4%（通过 LPR 法估计）。扫描电子显微镜（SEM）用于检查腐蚀和抑制的铝表面的形态，揭示了每种研究化合物的强烈抑制作用。高分辨率 X 射线光电子能谱（XPS）剖面验证了抑制剂化合物在 Al 表面上的吸附。密度泛函理论（DFT）和蒙特卡罗模拟被应用于研究研究的氧杂蒽对 Al（111）表面的防腐蚀行为的区别。氧杂蒽的非平面性和腈基的存在是吸附过程中的关键因素。实验和理论结果之间存在匹配。
