Structural diversity in copper(II) complexes of bis(thiosemicarbazone) and bis(semicarbazone) ligands

• Published in: Journal of coordination chemistry Vol. 58; no. 6; pp. 479 - 493
• Main Authors: Seleem, H. S., El-Shetary, B. A., Khalil, S. M. E., Mostafa, M., Shebl, M.
• Format: Journal Article
• Language: English
• Published: Taylor & Francis Group 15.04.2005
• Subjects: Binuclear; Bis(semicarbazone); Bis(thiosemicarbazone); trinuclear and dimeric CuII complexes
• ISSN: 0095-8972; 1029-0389
• DOI: 10.1080/00958970512331334269

Two symmetrical bis(carbazone) ligands, H 4 L 1 and H 4 L 2 , were prepared by condensation of 4,6-diacetylresorcinol with thiosemicarbazide and semicarbazide, respectively. Their structures were elucidated by elemental analyses and IR, electronic and 1 H NMR spectroscopy. Both ligands are tetrabasic and contain two sets of SNO (H 4 L 1 ) or ONO (H 4 L 2 ) coordinating sites. Binuclear, trinuclear and dimeric Cu II complexes and also adducts with organic bases were prepared. Reactions of H 4 L 1 with several Cu II salts, including Cl − , AcO − , , and , in addition to Cu I as CuI, afforded different binuclear complexes depending on the salt and the working conditions, except for CuCl 2 , where a trinuclear complex with a unique mode of bonding was obtained. These complexes reflect the strong coordinating power of Cl − , and AcO − compared to . The mode of bonding and the basicity of the H 4 L 1 ligand are also influenced by the counteranion, the pH of the reaction medium, the working conditions and the oxidation state of copper. The reactivity of the binuclear Cu II complexes of both H 4 L 1 and H 4 L 2 towards 1,10-phenanthroline (Phen), 2,2′-bipyridyl (Bpy), N,N,N′,N′-tetramethylethylenediamine (Tmen) and 8-hydroxyquinoline (Oxine; Ox) were investigated. Adducts with organic bases were obtained in the mole ratio 2 : 1 : 1 for H 4 L 1 and 2 : 1 : 2 for H 4 L 2 [Cu II  : ligand : base (base = Phen, Bpy or Ox)], which reflects the difference in size of S and O. With Tmen, dimeric complexes were obtained containing no Tmen molecules instead of the expected adducts for both H 4 L 1 and H 4 L 2 . Evidently the presence of Tmen in the reaction mixture enhances the dimerization process. Characterization and structure elucidation of the complexes was achieved by elemental and thermal analyses, electronic, IR, mass and ESR spectroscopy, as well as conductance and magnetic susceptibility measurements. Finally, the antifungal and antibacterial activities of H 4 L 1 and its metal complexes were investigated.