Ljiljana S. Jovanović

Synthesis, characterization and antitumor activity of polymeric copper(II) complexes with thiosemicarbazones of 3-methyl-5-oxo-1-phenyl-3-pyrazolin-4-carboxaldehyde and 5-oxo-3-phenyl-3-pyrazolin-4-carboxaldehyde.

New polymeric copper(II) complexes with two tridentate ONS thiosemicarbazone ligands containing substituted pyrazolone moiety were synthesized and characterized by means of spectroscopic, electrochemical and crystallographic techniques. While both ligands exist as different tautomers in the solid state and DMSO-d(6) solution, Cu(II) ion coordinates the ligands from the same tautomeric form with square-pyramidal geometry around each Cu atom. In the crystal structures, the copper(II) complex cation forms polymeric chains {[Cu(L)Cl](+)}(n) with a bridging chlorine atom. One of the complexes was found to have a significantly higher cytotoxic potential in comparison with cisplatin in inhibition of several cell lines (HL60, REH, C6, L929 and B16). The results obtained on the basis of flow cytometry indicated that apoptosis could be possible mechanism of cell death.

Transition metal complexes with the thiosemicarbazide-based ligands—III. Synthesis, physico-chemical properties and voltammetric characterization of some FeIII complexes with ter- and quadridentate S-methylisothiosemicarbazide derivatives

Abstract Several high-spin Fe III complexes of the type Fe(HL)Cl 2 and Fe(L)Cl (HL = monoanion of terdentate NNO ligand and L = dianion of quadridentate ONNO ligand, respectively), based on the condensation products of S-methylisothiosemicarbazide and different aromatic 2-hydroxy-aldehydes, have been prepared and characterized by elemental analysis, conductivity and magnetic measurements, IR and electronic spectra, as well as by cyclic voltammetry. For all solid complexes a pentacoordinated structure is proposed, while in DMF solutions hexacoordination is suggested. Differences in some physico-chemical properties, arising from structural changes in the coordinated ligand, are discussed.

Synthesis, physicochemical properties and voltammetric characterization of some new Fe(III) complexes with semicarbazone-based ligands

Abstract Several bis(ligand) octahedral complexes of iron(III) with salicylaldehyde semi-, thiosemi-, and S-methylthiosemi- carbazones have been synthesized and characterized by elemental analysis, conductivity and magnetic measurements, electronic and IR spectra, as well as by linear sweep and cyclic voltammetry. General procedures for the syntheses of all types of complexes have been established, giving better defined reaction conditions. Physicochemical properties of the novel complexes have been related to those of the already known compounds of the same type.

Transition metal complexes with the thiosemicarbazide-based ligands—XXIII. Synthesis, physicochemical properties and voltammetric characterization of iron(III) complexes with terdentate and quadridentate thiosemicarbazide derivatives

Abstract Two iron(III) complexes with the terdentate ONS and ONN ligands benzoylacetone thiosemi- and S-methylisothiosemicarbazone, respectively, of the general formula [Fe(HL)Cl2], were synthesized. Besides, the iron(III) complexes of the general formula [Fe(L)Cl] involving the quadridentate ONNO ligands N(1)-benzoylisopropilidene-N(4)-salicylidene (5-chloro-, 3,5-dichloro-, or 5-nitro-salicylidene) S-methylisothiosemicarbazide were also prepared. The complexes were characterized by elemental analysis, molar conductivity and magnetic measurements, IR and electronic spectra, as well as by cyclic voltammetry. It was found that the complexes are high-spin pentacoordinated. In addition, a detailed voltammetric study in DMF solutions has shown that the electrochemical processes are frequently accompanied by various chemical reactions.

Activation of glassy carbon electrode in aqueous and non-aqueous media

Abstract By recording the cyclic voltammograms at a freshly polished and electrochemically pretreated (ex situ) Tokai gce for the ferric/ferrous reaction in water, water + DMF, and water + ethanol, it was established that the activating effect of electrochemical pretreatment decreases with increasing content of the organic solvent in the solution.

Electrochemistry of iron(III) complexes with salicylaldehyde thiosemicarbazone and its S-methyl derivative

Abstract A detailed electrochemical study of Fe(III) chelate complexes with salicylaldehyde thiosemicarbazone (H2L1) and its S-methyl derivative (H2L2), of general formulae Fe(HL)Cl2, [Fe(HL)2]Cl, Fe(HL)L and Li[FeL2] was carried out at a glassy carbon electrode in a DMF + LiCl system. Both the cation and anion of the supporting electrolyte affect the behaviour of the complexes significantly: Li+ by forming ion pairs with the reduced bis(ligand) anions and Cl− via replacement of HL− in corresponding complexes. In addition, H+ plays an important role in both the heterogeneous and homogeneous processes. While all complex species are reduced in a one-electron process, those containing the L2− form can also be oxidized. The H2L1 complexes are more easily reduced/oxidized than the analogous H2L2 complexes. Chemical reactions associated with electron transfer processes make the overall behaviour of the compounds rather complex. All heterogeneous and homogeneous reactions are presented in a common reaction scheme, and the overall mechanism is discussed.

Transition metal complexes with the thiosemicarbazide-based ligand—XVI. Novel iron(IV) complexes with pentane-2,4-dione bis(s-methylisothiosemicarbazone)

Abstract Several square-pyramidal iron(IV) complexes with the quadridentate ligand pentane-2,4-dione bis(S-methylisothiosemicarbazone) (H3L) of the type [Fe(L)X], where X = Cl, Br, NCO or NCS, were synthesized and their physicochemical characteristics, together with those of previously reported [Fe(L)I] and [Fe(L)]2O, are described. The complexes were characterized by elemental analysis, molar conductivity and magnetic measurements, IR and electronic spectra. In addition, cyclic voltammetry is used to study the redox behaviour of the complexes in their DMF solutions and especially of the dimermonomer equilibria influenced by the acidity of the solution.

Synthesis, Structural, DFT, and Cytotoxicity Studies of CuII and NiII Complexes with 3-Aminopyrazole Derivatives*.

Template synthesis of N,N′-bis(4-acetyl-5-methylpyrazole-3-yl)formamidine (ampf) was performed starting from 4-acetyl-3-amino-5-methylpyrazole (aamp) and CH(OC2H5)3 in methanol in the presence of CuCl2, Cu(NO3)2, or Ni(NO3)2. The ligand was isolated in coordinated form as [Cu(ampf)Cl2], [Cu(ampf)(MeOH)(NO3)2]MeOH, and [Ni(ampf)(MeOH)2(NO3)]NO3 correspondingly. The compounds were characterized by elemental analysis, Fourier-transform IR and electronic spectroscopy, thermal analysis, single-crystal X-ray diffraction, and quantum chemical (density functional theory) calculations. The density functional theory calculations provided information on the metal–ligand interactions in the complexes and assisted the assignment of the FT-IR spectra. The antiproliferative activity of the complexes and the ligand precursor, aamp, was tested against human myelogenous leukaemia K562, colon adenocarcinoma HT29, and cervix carcinoma HeLa.

Complexes of iron(III) with benzoylacetone 1-naphthoylhydrazone

Abstract One mono(ligand) and three bis(ligand) octahedral complexes (cationic, anionic and non-electrolyte type) of iron(III) and benzoylacetone 1-naphthoylhydrazone have been prepared and characterized by elemental analysis, conductivity measurements, IR and electronic spectra, as well as by linear sweep and cyclic voltammetry. It has been found that formation of these complexes can be explained by the nature of this tridentate (ONO) ligand, taking part in coordination as both a mono- and a dianion.

Syntheses, crystal structures, and electrochemical characterizations of two octahedral iron(III) complexes with Schiff base of pyridoxal and aminoguanidine

This article presents the synthesis, physico-chemical, in particular voltammetric, characteristics of two iron(III) complexes with pyridoxal aminoguanidine (PLAG), [Fe(PLAG)Cl2(H2O)]Cl (1) and [Fe(PLAG)2](NO3)3 (2). As expected, the zwitterion of the chelate ligand is coordinated tridentate through oxygen of phenol and nitrogen atoms of azomethine and imino groups of the aminoguanidine fragment. In both complexes, Fe(III) is distorted octahedral. [Fe(PLAG)2](NO3)3 (2) is the first bis(ligand) complex with this ligand. Cyclic voltammetric characteristics of the ligand and complexes were studied in DMF in the presence of TBAP or LiCl as supporting electrolytes. The complexes are unstable in this solvent, especially in the presence of an excess of chloride, thus forming several reducible species whose stabilities and behaviors were characterized.