Comparative study of anti-ulcer drugs with benzimidazole ring as green corrosion inhibitors in acidic solution: Quantum chemical studies

The corrosion of metals in acidic environments is a grave concern, with the conventional use of commercial corrosion inhibitors leading to environmental toxicity. To address this issue, non-toxic, cost-effective drugs that have a minimal impact on the environment have the potential to replace traditional toxic inhibitors. This study aims to evaluate the molecular orbital properties of benzimidazole-containing drugs such as omeprazole, esomeprazole, and pantoprazole, through density functional theory (DFT), to assess their ability to act as corrosion inhibitors and explore their mechanism of inhibition. The study found that all three compounds have the ability to form a barrier film on the metal surface, with omeprazole being slightly more reactive than the others. Omeprazole and esomeprazole were found to be softer than pantoprazole, indicating that they are more reactive towards the metal surface. The study also found that the active sites of all compounds are located in the benzimidazole ring along with the methyl and methoxy groups. Additionally, the inhibitor molecules are adsorbed onto the metal surface through the active sites by transferring their electrons towards the metal surface. The adsorption energy calculation indicates that Omeprazole and Pantoprazole, with more negative adsorption free energy, exhibit superior corrosion inhibition ability compared to Pantoprazole. Overall, the study provides valuable insights into the potential use of these drugs as effective corrosion inhibitors.