In(OTf)3 Catalyzed Regioselective Approach for Synthesis of Multi-Functionalized Benzopyranophenazine Derivatives as Latent Corrosion Inhibitors on Mild Steel in 1 M HCl

A rapid and regioselective strategy have developed for synthesis of multi-functional phenazine derivatives such as 3- amino-1- (2-hydroxy phenyl) -1H- benzo[a] pyrano [2,3-c] phenazine -2- carbonitrile benzo-pyrano-phenazine (BPP) , 3-amino-1-(2-hydroxy-5-methoxyphenyl)-1H-benzo[a]pyrano[2,3-c]phenazine-2-carbonitrile ( MBPP) and 3-amino-1-(5-bromo-2-hydroxyphenyl)-1 H -benzo[a]pyrano[2,3-c]phenazine-2-carbonitrile (BBPP) using In(OTf) 3 as catalyst in simple one-pot multi-component reaction. Further, the regioselectivity of the product formation was confirmed by DFT studies. In addition, the synthesized compounds were evaluated for their corrosion inhibition strength on mild steel in 1 M hydrochloric acid solution by using weight loss and electrochemical techniques in the first time. Interestingly, the inhibition efficiency was increased up to 98.64 % with an increase in the inhibitor concentration and it was decreased with increases in temperature. These results indicate that our synthesized compounds adopt the Langmuir isotherm model. Further, the polarization measurements clearly indicate that synthesized phenazine derivatives act as mixed-type inhibitors. Also, the electrochemical impedance studies (EIS) strongly revealed that these compounds inhibit corrosion by adsorption mechanism. Moreover, the efficiency of corrosion inhibitors was explained by the surface morphology of the inhibited and uninhibited specimens and was examined using scanning electron microscopy (SEM). Finally, the correlation between the inhibition performance of phenazines and their structural parameters was clearly examined by DFT calculations.