Synthesis, characterization, X-ray structure, spectroscopic and electrochemical studies of copper and zinc complexes with two new polydentate ligands

• Two ligands form bi- and tri-nuclear complexes.
• All complexes are alkoxide bridge compounds.
• Cu complexes with Schiff base and its reduced form have different redox potentials.
• The hydroxyl and phenol oxygens participate as anionic oxygens in complexation.

Two new N2O5 donor type ligands, 2-{[(2-{2-hydroxy-3-[2-({[(2-hydroxyphenyl)methylidene]amino}methyl)phenoxy]propoxy}benzyl)imino]methyl}phenol (H3L1) and 2-[({2-[2-hydroxy-3-{[(2-hydroxybenzyl)amino]methyl}phenoxy)propoxy]benzyl} amino)methyl]phenol (H3L2) and their metal complexes with Cu(II) and Zn(II) salts were prepared and characterized by NMR, FT-IR, UV–Vis absorption spectroscopy, single crystal X-ray diffraction, CHN elemental analysis and cyclic voltammetry. Complexes were formulated as Cu2L1(CH3COO) (1), Cu2L2(CH3COO) (2), Zn3L1(CH3COO)3 (3), and Zn2L2(CH3COO)·0.5H2O (4). Cyclic voltammograms of copper(II) complexes recorded in DMF showed two quasi-reversible reduction peaks related to (CuII–CuII/CuII–CuI) and (CuII–CuI/CuI–CuI) couples and their corresponding oxidation potential peaks. Both Zn(II) complexes display only one irreversible reduction wave which can be attributed to the ZnII/Zn0 redox system. The X-ray structure analysis of the trinuclear complex [Zn3L1(CH3COO)3] shows that Zn(II) centers are coordinated to five atoms. The core of the structure is a triangle of Zn atoms. The Zn centers are bridged with deprotonated alkoxide and phenolate oxygens and two acetate groups. The π–π interactions between phenyl rings of the adjacent molecules in the complex are significant. The centroid–centroid distance is 3.6933(15) Å.

Two new N2O5 donor type ligands and their metal complexes with Cu(II) and Zn(II) salts were prepared and characterized by NMR, FT-IR, UV–Vis absorption spectroscopy, single crystal X-ray diffraction, CHN elemental analysis and cyclic voltammetry.Figure optionsDownload as PowerPoint slide