Abstract:
Three pyrazolo-pyridine derivatives namely, (PPs) (4-(4-methoyphenyl)3,5-dimethyl-1,4,7,8-tetrahydrodipyrazolopyridine)
(PP-1), 3,5dimethyl-4-phenyl-1,4,7,8-tetrahydrodipyrazolopyridine (PP-2) and (3,5-
dimethyl-4-(3-nitrophenyl)-1,4,7,8-tetrahyddrodipyrazolopyridine) (PP-3) having different substituents was
synthesized using ultrasound mediated one step multicomponent reactions and evaluated as corrosion inhibitors
for mild steel in acidic medium of 1M HCl. Protection ability of the synthesized PPs was determined using
several experimental and computational modeling methods. Results showed that PP-3 having electron withdrawing
nitro (–NO2) substituent showed lowest inhibition ability and PP-1 having electron releasing methoxy
(–OCH3) substituent showed the highest inhibition efficiency. Inhibition efficiencies of the tested PP molecules
followed the order: PP-1 (96.4%; –OCH3) > PP-2 (94.2%; –H) > PP-1 (91.1%; –NO2). Electrochemical studies
suggested that PPs acted as interface and mixed type of corrosion inhibitors and their adsorption at the metalelectrolyte
interfaces obeyed the Langmuir adsorption isotherm model. SEM and AFM analyses were adopted to
measure the surface morphology of inhibited and uninhibited metallic surfaces. Experimental results were
corroborated by results derived from DFT modeling and MD simulations
