Metal(II) complexes of compartmental polynuclear schiff bases containing phenolate and Alkoxy Groups

Abstract

Five mono-nuclear Cu(II) and Ni(II) complexes and one dinuclear Zn(II) complex were synthesized from the Schiff bases N,N'-bis(3-ethoxy-2-hydroxybenzylidene)-1,2-phenylenediamine (H2LOEt-phda) and 2-ethoxy-6-({2-[(3-ethoxy-2-hydroxybenzylidene)amino]-benzyl}iminomethyl)phenol (H2LOEt-ambza): [Cu(LOEt-phda)(H2O)].H2O (1), [Ni(LOEt-phda)].H2O (2), [Cu(LOEt-ambza)].H2O·EtOH (3), [Cu(LOEt-ambza)].H2O (4), [Ni(LOEt-ambza)] (5) and [Zn2(LOEt-ambza)(μ-OAc)(OAc)] (6). The complexes were structurally characterized with elemental microanalyses, IR, UV-Vis and ESI-MS spectroscopic techniques as well as single crystal X-ray crystallography. The metal centers display distorted square planar geometries in 2–4 and 5 and distorted square pyramidal (SP) in 1, whereas in 6 an intermediate geometry between SP and TBP was observed around the first Zn2+ ion and a tetrahedral around the second ion, with one acetate is acting as a bridging ligand. In all cases, metal ions were incorporated into the N2-O2 binding site with no involvement of the alkoxy groups in the coordination. The LOEt-ambza-complexes 3–6 revealed significant dihedral angles between the phenol rings and the plane containing the central benzene ring, and large O2-O2 bond distances (5.1-5.9 Ǻ). Results are discussed in relation to other related Schiff base complexes.