Green synthesis of pyrazolo[3,4-b]pyridine derivatives by ultrasonic technique and their application as corrosion inhibitor for mild steel in acid medium

Abstract

A green and convenient method using ultrasonic irradiation for the synthesis of pyrazolo[3,4-b]pyridine [PP] derivatives such as 4-(4-bromophenyl)-3-methyl-6-oxo-4,5,6,7-tetrahydro-2H-pyrazolo[3,4-b]pyridine-5-carbonitrile (PP-1), 4-(4-chlorophenyl)-3-methyl-6-oxo-4,5,6,7-tetrahydro-2H-pyrazolo[3,4-b]pyridine-5-carbonitrile (PP-2), 3-methyl-6-oxo-4-(3 phenoxyphenyl)-4,5,6,7-tetrahydro-2H-pyrazolo[3,4-b]pyridine-5-carbonitrile (PP-3) has been derived. The inhibition performance of the synthesized compounds on mild steel (MS) in 1M HCl has been investigated using weight loss, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques. The results of electrochemical studies reveal that pyrazolo[3,4-b]pyridine derivatives are mixed type inhibitor and they inhibit corrosion by adsorption mechanism.