Synthesis, characterization, crystal structures and biological activity of novel NiII2ZnII2 complexes derived from 2-(3-ethoxy-2-hydroxybenzylideneamino)-4-methylphenol

Abstract

Molecular nanoclusters comprising heterometallic Ni-Zn cores are an interesting class of compounds. In this paper, five novel NiII-ZnII complexes [Ni2Zn2ClL3(HL)3]·0·.25H2O (1), [Ni2Zn2BrL3(HL)3]·0·.25H2O (2), [Ni2Zn2Br2L2(N3)2(MeOH)2]·2MeOH (3), [Ni2Zn2I2L2(N3)2(MeOH)2]·2MeOH (4), and [Ni2Zn2I2L2(N3)2(DMF)2] (5), were prepared from the Schiff base 2-(3-ethoxy-2-hydroxybenzylideneamino)-4-methylphenol (H2L). The complexes have been characterized by elemental analysis, IR, UV–Vis spectra. Molecular structures of the complexes have been determined by single crystal X-ray determination. In complexes 1 and 2, three of the Schiff bases coordinate to the metal atoms via ether oxygen, imino nitrogen and two phenolate oxygen atoms, while the fourth one coordinates through ether oxygen, imino nitrogen and one phenolate oxygen atoms. In complexes 3, 4 and 5, all the donor atoms in the Schiff base ligands participate in coordination. The Ni and Zn atoms in the complexes are in octahedral and trigonal bipyramidal coordination, respectively. The anions of the metal salts and the azide anion, as well as methanol and DMF molecules furnish the coordination sphere. The compounds were evaluated for their antibacterial activities on Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Pseudomonas fluorescens, and antifungal activities on Candida albicans and Aspergillus niger. Interestingly, the complexes have effective activities against Bacillus subtilis and Staphylococcus aureus.