Binuclear and mononuclear Cu(II) and Ni(II) complexes of tetra- and hexadentate ligands: Synthesis, antifungal activity, spectroscopic and thermal characterization

Two tetradentate ligands, 1,2-bis(2-hydroxyethylthio)ethane S 2 O 2 ( L 1 ) and N , N ′-bis(2-hydoxypropyl)piperazine N 2 O 2 ( L 2 ), were prepared by organization of some mononuclear complexes of Cu(II) and Ni(II). A new binuclear Schiff base ligand with a 1,4-dipropoxybutane spacer provided by the reaction of salicylaldehyde and 1,4-bis(3-aminopropoxy)butane served as an octadentate, N 2 O 4 ( L 3 ) ligand, in designing some binuclear complexes with metal ions. All the ligands were characterized by elemental analyses, FTIR, 1 H and 13 C NMR and GC–MS. The complexes were characterized by elemental analyses, FTIR, thermal methods, electronic spectra, conductivity and magnetic measurements. The metal ions coordinate to the ligands with four donor atoms in square planar geometry. The thermal stabilities of the complexes were discussed in terms of metal ions and type of donor atoms. The complexes were characterized by electronic spectra and magnetic susceptibility measurements to establish the proposed four-coordinated square planar geometry. The TG chart indicates high thermal stability for complexes. The decomposition processes consisted of three stages: The first two stages involve the loss of water and chloride anions and the last stage indicates degradation of the organic ligands. The antifungal activity of the ligands and their complexes was tested against several fungal species: Aspergillus nigar , Aspergillus flavus and Candida albicans. The results show that complexes have significant antifungal activities compared to their parent ligands.