The effect of heterocyclization of 2-mercaptobenzimidazole on its strength of coordination to iron: A dispersion-corrected DFT study

Benzimidazole derivatives have been widely investigated as corrosion inhibitors due to their unique chemical reactivity with different metal surfaces. Herein, the effect of heterocyclization on corrosion inhibition mechanisms and bonding of two 2-mercaptobenzimidazole derivatives (MBIs) -2,3-dihydrobenzo[4,5]imidazo[2,1-b] thiazole (2HBIT) and 3,4-dihydro-2H-benzo[4,5]imidazo[2,1-b]thiazole (3HBIT) - with Fe(1 1 0) surface was comprehensively evaluated using dispersion-corrected density functional theory (DFT). The interaction energies computed from DFT calculations successfully predicted the experimental inhibition performance. The effect of protonation on the adsorption strength of molecules was also investigated. We have found strong covalent bond formation between S, C, and N atoms of molecules and Fe-atoms. The excellent charge transfer between molecules' atoms and Fe(1 1 0) surface was further confirmed by the projected density of states and electron density difference plots. The adsorption energy of MBI adsorbed on Fe(1 1 0) surface was also determined for comparison purposes. This study showed that the heterocyclization of 2-mercaptobenzimidazole increased the charge transfer and bonding between MBIs and the Fe(1 1 0) substrate, thereby improving their corrosion inhibition performance.