Synthesis, Characterization, Theoretical and Electrochemical Studies of Pyrazoline Derivatives

Abstract

The reaction of 1,3-dipolar cycloaddition of trans-anethole and three different diarylnitrilimines bearing different substituents X= {H, CH₃, Cl} yield to the creation of three 1,3,4,5-tetrasubstituted pyrazoles. These reactions produce a single regioisomer. These compounds' structures were studied using diverse spectroscopic techniques such as ¹H, ¹³C NMR, and HRMS. Afterwards, X-ray diffraction is performed at 5-(4-methoxyphenyl)-4-methyl-1,3-diphenyl-4,5-dihydro-1H-pyrazole. Also, Density Functional Theory (DFT) is performed to characterize these cycloadducts.

Moreover, these synthesized compounds' molecular geometry and electronic structures have been studied using high-level ab initio calculations and DFT using the B3LYP functional. All geometries have been optimized at the B3LYP/6-311+G(d,p) basis set with different kinds of solvents. In the end, the protection against corrosion of copper surface is tested using these pyrazolines. As a result, the experimental analysis proved that the obtained cycloadducts belong to the pyrazoline family. Also, X-ray diffraction determined the stereochemistry of these compounds. DFT-based calculations revealed the existence of three stable conformations of each compound. The theoretical study and the experimental spectroscopic data showed perfect matching. The electrochemical investigation indicates that these pyrazoline compounds exhibit a good inhibition performance, preventing the degradation of copper in NaCl (3%) solution with a high inhibition efficiency of 80%.