Thiosemicarbazone complexes of copper(II): structural and biological studies

In the present contribution, some novel Cu(II) complexes were synthesized from tri- and tetradentate imine ligands. All the prepared compounds were elucidated by different physicochemical methods. Density Functional Theory calculations were carried out to explain the equilibrium geometry of the bsisnph and npisnph ligands and their Cu(II) complexes. Interaction of the synthesized ligands with Cu(II) affords nano-sized particles via TEM. The catalytic potentials of the prepared complexes has been tested within the oxidation of benzyl alcohol using an environmental friendly terminal oxidant, i.e. H2O2. The effect of various parameters, e.g. solvents, temperature and amount of catalyst was investigated. A mechanistic pathway of the catalytic oxidation was tentatively described and discussed.

Some New Nano-sized Mononuclear Cu(II) Schiff Base Complexes: Design, Characterization, Molecular Modeling and Catalytic Potentials in Benzyl Alcohol Oxidation

A novel Schiff base, namely Z-3-((2-((E)-(2-hydroxynaphthyl)methylene)amino)-5-nitrophenylimino)-1,3-dihydroindin-2-one, was synthesized from the condensation of 2-hydroxy-1-naphthaldehyde and isatin with 4-nitro-o-phenylenediamine. It was structurally characterized on the basis of 1H NMR, 13C NMR and infrared spectra and elemental analyses. In addition, Ni(II) and Cu(II) complexes of the Schiff base ligand were prepared. The nature of bonding and the stereochemistry of the investigated complexes were elucidated using several techniques, including elemental analysis (C, H, N), Fourier transform infrared and electronic spectroscopies and molar conductivity. The thermal behaviours of the complexes were studied and kinetic–thermodynamic parameters were determined using the Coats–Redfern method. Density functional theory calculations at the B3LYP/6-311G++ (d, p) level of theory were carried out to explain the equilibrium geometry of the ligand. The optimized geometry parameters of the complexes were evaluated using LANL2DZ basis set. The total energy of highest occupied and lowest unoccupied molecular orbitals, Mullikan atomic charges, dipole moment and orientation are discussed. Moreover, the interaction of the metal complexes with calf thymus DNA (CT-DNA) was explored using electronic spectra, viscosity measurements and gel electrophoresis. The experimental evidence indicated that the two complexes could strongly bind to CT-DNA via an intercalation mechanism. The intrinsic binding constants of the investigated Ni(II) and Cu(II) complexes with CT-DNA were 1.02 × 106 and 2.15 × 106 M−1, respectively, which are higher than that of the standard ethidium bromide. Furthermore, the bio-efficacy of the ligand and its complexes was examined in vitro against the growth of bacteria and fungi to evaluate the antimicrobial potential. Based on the obtained results, the prepared complexes have promise for use as drugs. Copyright © 2016 John Wiley & Sons, Ltd.

Ni(II) and Cu(II) complexes with ONNO asymmetric tetradentate Schiff base ligand: synthesis, spectroscopic characterization, theoretical calculations, DNA interaction and antimicrobial studies

Mono- and binuclear complexes of malonyl bis(thiosemicarbazide), H4 MBT, with VO2+, Co2+, Ni2+, Cu2+, Cd2+ and Pt4+ have been isolated. The elemental analyses, magnetic moments, spectra [u.v.–vis., i.r., e.s.r. (for Cu2+; VO2+) and mass], thermal and voltammetric measurements [for Co2+ and Ni2+] have been used to characterize the isolated complexes. The ligand behaves as binegative quadridentate with Cu2+, Co2+ and VO2+ ions, binegative pentadentate with Pt4+ and hexadentate, either as trinegative in [Cd2(HMBT)(OC2H5)(C2H5OH)]H2O or mononegative in [Ni2(H3MBT)(OAc)3(C2H5OH)]. The lack of thiol and/or enol hydrogen during the complex formation was confirmed pH-metrically. The pK’s (10.70, 8.50 and 8.15) of H4MBT reveal the removal of CSNH protons in one step and CONH in two steps. Also, the stability constants reveal a higher value for the Cu2+ complex and a lower one for VO2+. The TG analyses suggest high stability for most complexes followed by thermal decomposition in different steps. The kinetic and thermodynamic parameters for some decomposition steps in VO2+and Pt4+ thermograms have been calculated

Spectral, magnetic, electrical and thermal studies on malonyl bis(thiosemicarbazide) complexes

The coordination behaviour of phthaloyl bis(thiosemicarbazide), H4PBT, towards VO2+, Co(II), Ni(II), Cu(II), Zn(II) and ions has been investigated. The elemental analyses, magnetic moments, spectra [UV-Vis, IR, ESR and MS] and thermal studies were used to characterize the isolated complexes. Cyclic voltammetry was used to study the electrochemical behaviour of the Cu(II) complex. The IR spectra showed that the ligand is deprotonated in the complexes and acts as a binegative SSNN donor. The f U–O (mdyn A−1) and the length r U−O (A) of the UO bond are calculated spectroscopically from the IR data. The loss of thiol hydrogen during the formation of complexes was confirmed from the pH-metric titrations of the ligand and its metal(II) complexes. The protonation constants of the ligand (pK1 = 9.45 and pK2 = 7.25) as well as the stability constants of its complexes were calculated. The intensity and position of the V=O band in the IR spectra reflect the geometry of the formed complex. Also, its colour (dark gree...

Spectral, magnetic, thermal and electrochemical studies on phthaloyl bis(thiosemicarbazide) complexes

Spectral, magnetic and electrical properties of 1-succinyl bis(4-phenylthiosemicarbazide) complexes

Several new complexes of the title ligand (H2MPTS) with CoII, NiII, CuII, and CdII have been prepared. Structural assignments of the complexes have been made based on elemental analysis, molar conductivity, magnetic moment and spectral (i.r.,1H n.m.r., reflectance) studies. The compounds are non-conductors in dimethylsulphoxide. The neutral molecule is coordinated to the metal(II) sulphate as a bidentate ligandvia the two carbonyl groups. The ligand reacts with the metal(II) chlorides with the liberation of two hydrogen ions, behaving as a bianionic quadridentate (NONO) donor. Enolization is confirmed by the pH-titration of H2 MPTS and its metal(II) complexes against NaOH. A distorted octahedral structure is proposed for the CuII complex, while a square planar structure is suggested for both CoII and NiII complexes. The stoichiometry of the complexes formed in EtOH and buffer solutions, their apparent formation constants and the ranges for obedience to Beer's law are reported for CoII, NiII and CuII ions. The ligand pK values are calculated. The antimicrobial activity of H2 MPTS and its CoII, NiII, CuII and MnII complexes is demonstrated.

Structural studies on cadmium(II), cobalt(II), copper(II), nickel(II) and zinc(II) complexes of 1-malonyl-bis(4-phenylthiosemicarbazide)

Metal complexes formed by the interaction of 1-acetylacetone-4-ethylthiosemicarbazone(AET) with Co(II), Ni(II), Cu(II) and UO2(II) have been prepared and characterized. The ligand acts as a bidentate and it exhibits the thione structure in the complexes. The stereochemistry of these complexes is discussed based upon their spectral and magnetic properties. The electrical conductivities of the metal complexes indicate a semiconducting character for the Co(II) and Ni(II) complexes. The antimicrobial activity of AET and its Co(II) and Cu(II) complexes is also described.

Transition Metal Complexes of 1-Acetylacetone-4-Ethylthiosemicarbazone

Complexes of CoII, NiII, CuII, ZnII, CdII, HgII and UO
 2
 II
 with benzil bis(4-phenylthiosemicarbazone), H2BPT, have been synthesized and their structures assigned based on elemental analysis, molar conductivity, magnetic susceptibility and spectroscopic measurements. The i.r. spectra suggest that the ligand behaves as a binegative quadridentate (NSSN) (CoII, CuII, HgII and UO
 2
 II
 complexes) or as a binegative quadridentate-neutral bidentate chelating agent (NiII, ZnII and CdII complexes). Octahedral structures for the CoII and NiII complexes and square-planar structure for the CuII complex are suggested on the basis of magnetic and spectral evidence. The crystal field parameters (Dq, B andμ
B) for the CoII complex are calculated and agree fairly well with the values reported for known octahedral complexes. The ligand can be used for the microdetermination of NiII ions of concentration in the 0.4–6×10−4 mol l−1 range and the apparent formation constant for the species generated in solution has also been calculated.

T. Y. Al-Ansi

Papers

Spectral, magnetic and electrical properties of 1-succinyl bis(4-phenylthiosemicarbazide) complexes

Structural studies on cadmium(II), cobalt(II), copper(II), nickel(II) and zinc(II) complexes of 1-malonyl-bis(4-phenylthiosemicarbazide)

Transition Metal Complexes of 1-Acetylacetone-4-Ethylthiosemicarbazone

Chelated complexes of cadmium(II), cobalt(II), copper(II), mercury(II), nickel(II), uranyl(II) and zinc(II) with benzil bis(4-phenylthiosemicarbazone)

Physicochemical studies on transition metal complexes of 1-oxalylbis(4-phenyl-thiosemicarbazide) (H2OPTS)