Synthesis, characterization, chelation with transition metal ions, and antibacterial and antifungal studies of the 4-[(E)- -phenyldiazenyl]-2-[(E)-(phenylimino)methyl]phenol dye

New Ni(II), Cu(II) and Co(II) complexes were synthesized with the bidentate azo-azomethine dye, 4-((E)-phenyldiazenyl)-2-((E)-(phenylimino)me- thyl)phenol (dmpH), which was prepared by the reaction of 2-hydroxy-5-((E)- phenyldiazenyl)benzaldehyde with aniline in EtOH. The syntheses of the metal chelates of the azo-azomethine dye were realized by the precipitation techni- que. The synthesized metal complexes were characterized by elemental ana- lysis, molar conductance measurements, as well as infrared and UV-Vis spectral data. Based on these characterizations, the metal complexes of the transition metal ions may be formulated as (M(dmp)Cl(H2O)) where M = Ni(II), Cu(II) and Co(II). The metal complexes were formed by the coordination of N and O atoms of the ligand. The molar conductance values of the Ni(II), Cu(II) and Co(II) complexes of the bidentate ligand indicate their non-ionic character. The free ligand and its metal complexes were tested for their in vitro antimicrobial properties against eight bacteria: Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, Mycobacterium smegmatis, Pseudomonas aeruginosa, Enterococcus cloacae, Bacillus megaterium, and Micrococcus luteus, and three fungi, Kluyveromyces fragilis, Rhodotorula rubra and Saccharomyces cerevi- siae, in order to assess their antimicrobial potential. The (Ni(dmp)Cl(H2O)) chelate exhibited high activity against all the bacteria and fungi, except Rhodotorula rubra.