Piperine derivatives as green corrosion inhibitors on iron surface; DFT, Monte Carlo dynamics study and complexation modes

In the present paper, the interaction of three Piperine derivatives namely: 5-(1,3-benzodioxol-5-yl)-1-(piperidin-1-yl) pent-2-en-1-one (S1), 5-(1,3-benzodioxol-5-yl)-1-(piperidin-1-yl) penta-2,4-dien-1-one (S2) and 5-(1,3-benzodioxol-5-yl) penta-2,4-dienoic acid (S3) with iron (Fe) have been investigated theoretically by means of DFT method at the B3LYP/LANL2DZ high basis set. The interaction with iron surface therefore all possible Fe-inhibitor interaction modes at ―O― and >N― active sites. The preferred complexes are those in which the Fe-atoms is in mono-dentate mode to the studied inhibitors. The quantum chemical properties most relevant to their potential action as corrosion inhibitors have also been calculated in both isolated and Fe-inhibitor (Si) complex form for comparison. The values of the calculated interaction energy are consistent with the experimentally observed highest corrosion inhibition efficiency trend for the three S1FeN26, S2FeN24 & S3FeO26 complexes. The chemical reactivity and site selectivity of the molecule has been determined with the help of global and local reactivity descriptors of Fe-inhibitor (Si) complexes. The calculations show that S1FeN26, S2FeN24 and S3FeO26 complexes have thermodynamically favorable binding (ΔG〈0), whereas the other inactive Fe-(Si)complexes were characterized by slightly positive binding free energy values (ΔG〉0). Furthermore, molecular dynamics simulation was applied to investigate the final and most stable configuration of the inhibitors Si over Fe (111) in aqueous solution of hydrochloric acid (1.0 M HCl).