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)-propylidenel-hydrazide (H(2)hbpp) 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(11) 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 HCI medium has also been performed and the activity is found in the order: H(2)hbpp < Cu(II) complex < Mn(II) complex < Zn(II) complex. (C) 2014 Elsevier Ltd. All rights reserved.