Electrochemical and DFT insights into 2-amino-4-(4-hydroxy-3-methoxyphenyl)-7-methyl-4H-chromene-3-carbonitrile: an innovative strategy for antibacterial activity and corrosion protection of carbon steel

This study explored the potential of a newly synthesized derivative, 2-amino-4-(4-hydroxy-3-methoxyphenyl)-7-methyl-4H-chromene-3-carbonitrile (AHMCC), as a broad-spectrum antibacterial agent and a corrosion inhibitor for carbon steel (C.STL) in 0.5 M HCl solution. AHMCC demonstrated remarkable antibacterial efficacy against Gram-negative (Escherichia coli, Klebsiella pneumoniae) and Gram-positive (Bacillus subtilis, Staphylococcus aureus) bacteria, as evidenced by agar plate tests and cell viability assays. In the corrosion inhibition studies, AHMCC exhibited mixed-type inhibitor behavior as revealed by potentiodynamic polarization (PDP) measurements. The inhibition efficiency increased with rising AHMCC concentration, confirmed by a significant enhancement in charge transfer resistance (R-ct) observed in electrochemical impedance spectroscopy (EIS) analysis. Electrochemical frequency modulation (EFM) data with obtained CF2 and CF3 values further corroborated these findings. Langmuir isotherm modeling suggested AHMCC molecules followed a monolayer adsorption pattern on the C.STL surface. UV-visible spectroscopy indicated the formation of a protective layer through chemical interaction between AHMCC and the metal surface. Atomic force microscopy (AFM) provided visual confirmation of this protective film shielding the C.STL from the corrosive environment. Additionally, theoretical calculations supported the proposed adsorption mechanism of AHMCC molecules onto the C.STL surface.