Synthesis, structural and corrosion inhibition studies on Mn(II), Cu(II) and Zn(II) complexes with a Schiff base derived from 2-hydroxypropiophenone

A Schiff base, 2-hydroxy-benzoic acid [1-(2-hydroxy-phenyl)-propylidene]-hydrazide (H2hbpp) and its Mn(II), Cu(II) and Zn(II) complexes have been synthesized. These compounds have been characterized by different physico-chemical and spectroscopic techniques (UV–Vis, IR, NMR and ESI-Mass). The molecular structure of H2hbpp and its Mn(II) and Zn(II) complexes are determined by single crystal X-ray diffraction technique. In Mn(II) and Cu(II) complexes, the ligand coordinates through azomethine-N, carbonyl-O and phenolate-O (2-hydroxypropiophenone) forming a mono-nuclear 6-coordinate distorted octahedral geometry around metal. However, Zn(II) complex forms a phenoxo-bridged centrosymmetric dimer with 5-coordinate distorted square pyramid geometry around each metal ion. In this complex, the ligand bonds through azomethine-N, carbonylate-O and two phenolate-O, and a DMSO molecule occupies one of the vacant site of each metal. The structure of Cu(II) complex has been satisfactorily modeled by density functional theory (DFT) and time dependent-DFT (TD-DFT) calculations. The corrosion inhibition study of the synthesized compounds for mild steel in 1 M HCl medium has also been performed and the activity is found in the order: H2hbpp < Cu(II) complex < Mn(II) complex < Zn(II) complex.

Graphical abstractMononuclear Mn(II), Cu(II) and phenoxo-bridged dimeric Zn(II) complexes of 2-hydroxy-benzoic acid[1-(2-hydroxy-phenyl)-propylidene]-hydrazide have been synthesized and characterized by different spectral and X-ray diffraction techniques. These compounds have also been analyzed for corrosion-inhibition properties for mild steel in 1 M HCl medium.Figure optionsDownload full-size imageDownload as PowerPoint slide