Synthesis, NMR characterization, DFT and anti-corrosion on carbon steel in 1M HCl of two novel 1,5-benzodiazepines

Benzodiazepines are known for their variety of applications. Herein, the corrosion inhibition efficiency on carbon steel in 1 M HCl solution in the presence and absence of two synthesized benzodiazepines 4-(2-Oxopropylidene)-1-propargyl-1,2,4,5-tetrahydro-3H-1,5-benzodiazepin-2-one (PTB) and 1-decyl-4-(2-oxopropylidene)-1,2,4,5-tetrahydro-3H-1,5-benzodiazepine-2-one (DTB) was investigated using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) methods at various concentrations from 10−3 to 10−6 K. The obtained structures were characterized using NMR spectroscopy. Potentiodynamic polarization measurements showed that 1,5-benzodiazepine derivatives act as a mixed type inhibitor. The various parameters of activation determining the kinetic data such as energy, enthalpy and entropy of the inhibitors were evaluated and discussed. The adsorptive behavior of PTB and DTB followed Langmuir-type isotherm. The standard free energies of adsorption were negative due to better inhibition performance. DFT calculations at the B3LYP/6-31 + G (d,p) level of theory in polarizable continuum model reveal that the high inhibition of efficiency of DTB compared with PTB may refer mainly to the easy electron transfer from the former to the carbon steel surface. © 2019 Elsevier B.V.