Abstract
An effective method for designing new heterocyclic compounds of 6,7-dihydro-5H-cyclopenta[b]pyridine-3-carbonitrile derivatives (CAPDs) was presented through cyclocondensation reaction between 2,5-diarylidenecyclopentanone derivatives and propanedinitrile, and the cyclocondensation reaction succeeded using a sodium alkoxide solution (sodium ethoxide or sodium methoxide) as the reagent and the catalyst. The synthesized CAPD derivatives were employed as novel inhibitors for carbon steel (CS) corrosion in a molar H2SO4 medium. The corrosion protection proficiency was investigated by electrochemical measurements (open circuit potential vs time (E-OCP vs t), potentiodynamic polarization plots (PDP), and electrochemical impedance spectroscopy (EIS)) and surface morphology (scanning electron microscopy (SEM)) examinations. The results show that the CAPD derivatives exhibit mixed type inhibitors and a superior inhibition efficiency of 97.7% in the presence of 1.0 mM CAPD-1. The adsorption of CAPD derivatives on the CS interface follows the Langmuir isotherm model, including physisorption and chemisorption. Scanning electron microscopy (SEM) exploration confirmed the adsorption of the CAPD derivatives on the CS substrate. Monte Carlo (MC) simulations and DFT calculations revealed that the efficacy of the CAPD molecules correlates well with their structures, and this protection was attributed to their adsorption on the CS surface.