<p>The present study explores the sustainable synthesis method for the preparation of a notable heterocyclic compound of N-(benzo[d]thiazol-2-yl) nicotinamide through environmentally benign propylphosphonic anhydride (T3P) as a coupling agent. The structure of the synthesised molecule has been characterized by using specific spectroscopic techniques, including UV–Visible, Fourier Transform Infrared (FT-IR), and NMR spectroscopy. The thermal behaviour of the molecule has been assessed through the thermogravimetric analysis (TGA) plot. Additionally, the cyclic voltametric technique has been used to understand the electrochemical profile. Using potentiodynamic polarisation and AC impedance spectroscopy techniques, the corrosion inhibition property of N-(benzo[d]thiazol-2-yl) nicotinamide on mild steel in 1&#xa0;M HCl solution was investigated. Density Functional Theory (DFT) and Monte Carlo (MC) simulation techniques have been employed to compute the electronic distributions of the molecule, which is crucial in elucidating the structure–property relationship of the molecule. The inhibitor was discovered to influence both anodic and cathodic corrosion processes by forming a protective layer on the Fe (110) surface. The Temkin adsorption isotherm is compatible with the spontaneous formation of this protective layer. N-(Benzo[d]thiazol-2-yl) nicotinamide inhibitor spontaneously adsorbed onto the mild steel surface by both physical and chemical adsorption modes, as indicated by the computed Gibbs free energy (ΔG_ads), which was − 34.816&#xa0;kJ/mol. The experimental results were further supported by computational investigations using density functional theory (DFT) and Monte Carlo (MC) simulations, which verified that bonds were formed between the Fe (110) surface and N-(benzo[d]thiazol-2-yl) nicotinamide in the 1&#xa0;M HCl solution.</p> Graphical Abstract <p></p>