Vukadin M. Leovac

Reaction of copper(II) with 1-carboxamide-3,5-dimethylpyrazole, 1-carboxamidine-3,5-dimethylpyrazole, 4-acetyl-3-amino-5-methylpyrazole and 5-amino-4-carboxamide-1-phenylpyrazole ☆

Abstract Complex formation of copper(II) bromide and acetate with 1-carboxamide-3,5-dimethylpyrazole (HL3) and copper(II) bromide with 5-amino-4-carboxamide-1-phenylpyrazole (L2), 4-acetyl-3-amino-5-methylpyrazole (HL4) and 1-carboxamidine-3,5-dimethylpyrazole (HL5), was studied. The obtained compounds, CuBr2(L2)2, Cu(L3)2, CuBr2(HL4)2, CuBr2(HL5)2 and [CuBr(HL1)(L3)]2 (HL1 denotes the 3,5-dimethylpyrazole), are characterized by elemental analysis, FT-IR spectrometry, molar conductivity, TG-MS and DSC. The X-ray structure of [CuBr(HL1)(L3)]2 and Cu(L3)2 is discussed. For [CuBr(HL1)(L3)]2 a dimeric penta-co-ordinated structure has been found; the co-ordination around the metal in Cu(L3)2 is trans-square planar. To CuBr2(L2)2 and CuBr2(HL4)2 a nearly tetrahedral, while for CuBr2(HL5)2 an octahedral geometry may be assumed. It means that the geometry of the compounds in the first place depends on the ligand substituents. The course of the complex formation reaction is anion-dependent and may be explained on the basis of Pearsons theory, taking into account the steric factors. A low stability intermediate formation was observed in the thermal decomposition of Cu(L3)2.

Synthesis and structure of aqua-2′,‴-(2,6-pyridindiyldiethylidene) dioxamohydrazide-copper(II) hydrate

Abstract In a template synthesis from copper(II) acetate, 2,6-diacetylpyridine, and semioxamazide (NH2CO CONHNH2), two copper(II) complexes, [Cu(dapsox)(H2O)]·H2O and [Cu(Hdapsox)](H2O)]ClO4, (where H2dapsox = 2′,2‴-(2,6-pyridindiyldiethylidene)dioxamohydrazide) were obtained and characterized. The structure of the former complex was determined by a single-crystal X-ray analysis. CuII is located in a square pyramidal environment. The polydentate ligand, dapsox2− is coordinated in dianionic form, as an unsymmetrical quadridentate planar system forming one-membered and two-five-membered metal-chelate rings. The fifth coordination site is occupied by a water molecule.

Metal complexes with pyrazole-derived ligands Part I. Synthesis and crystal structures of 3-amino-4-acetyl-5-methylpyrazole (L) and of the tetrahedral complexes ZnL2(NO3)2 and ML2Cl2 (M=Cu(II), Hg(II))

A new pyrazole-derived ligand 3-amino-4-acetyl-5-methylpyrazole (L) has been synthesized and structurally characterized. In order to examine its coordination properties the metal complexes ZnL2(NO3)2, CuL2Cl2 and HgL2Cl2 have been prepared and their crystal and molecular structures determined by X-ray structure analysis. The crystals of the ligand are triclinic, space group P with unit cell dimensions a=14.433(4), b=7.406(1), c=6.794(4) A, α=99.81(4), β=92.10(9), γ=105.55(6)°, V= 686.8(5) A3; ZnL2(NO3)2 is orthorhombic, space group Pbca,a=18.420(2), b=14.892(2), c=14.114(2) A, V=3872(1) A3; CuL2Cl2 is monoclinic, space group I2/a,a=13.804(3), b=8.835(1), c=14.264(4) A, β=100.50(3)°, V=1710.5(7) A3; HgL2Cl2 is monoclinic, space group I2/a,a=14.075(2), b=9.002(2), c=14.303(3) A, β=97.39(2)°, V=1797.2(6) A3. The two latter complexes are isostructural. The ligand L acts as a monodentate ligand through the tertiary ring nitrogen atom. The complexes contain metal atoms in the distorted tetrahedral coordination realized by two nitrogen atoms from the two ligands L and two nitrate-oxygen atoms in the zinc complex and two chlorine atoms in the copper and mercury complexes. All four structures are built up from individual molecules linked together by hydrogen bonding interactions NH…O achieved between ‘pyrrole’ ring nitrogens of one molecule and the acetyl-oxygen atoms from the adjacent molecules. In the free ligand the additional hydrogen bondings NH…N occur also between amino and ‘pyridine’ nitrogen atoms of the neighboring molecules. The general physicochemical characteristics as well as the IR and 1H NMR spectra are in accordance with the observed molecular structures.

Synthesis and structure of aquamethanol-2′,2‴-(2,6-pyridin-diyldiethylidene)-dioxamohydrazidocobalt(II) perchlorate

Abstract The complex [Co(H 2 L)(H 2 O)(MeOH)](ClO 4 ) 2 [H 2 L] = 2′,2‴-(2,6-pyridindiyl-diethylidene)-dioxamohydrazide] has been prepared by direct and template syntheses and characterized by elemental analysis, IR spectroscopy, and magnetic susceptibility measurements. The crystal structure of the complex has also been determined. The cobalt atom is seven coordinated with approximately pentagonal-bipyramidal geometry. The H 2 O and methanol are axial with the planar pentadentate H 2 L ligand forming the equatorial plane. The possible reaction mechanism has been proposed.

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 PYRAZOLE-BASED LIGANDS Part 8. Characterization and thermal decomposition of zinc(II) complexes with di- and trisubstituted pyrazoles

We report the synthesis and the characterization (elemental analysis, FT-IR spectroscopy, thermal methods and molar conductivity measurements) of the mixed complexes of zinc with acetate and 3-amino-5-methylpyrazole, HL1, [Zn(OAc)2(HL1)2], or 3-amino-5-phenylpyrazole, HL2 [Zn(OAc)2(HL2)2], or 4-acetyl-3-amino-5-methylpyrazole, HL3, [Zn(OAc)(L3)(HL3)]2, with isothiocyanate and HL2 [Zn(SCN)2(HL2)2], or HL3 [Zn(SCN)2(HL3)2], and with nitrate, isothiocyanate and 3,5-dimethyl-1-carboxamidinepyrazole, HL4 [Zn(NO3)(NCS)(HL4)2].The thermal decomposition of the complexes is generally continuous resulting zinc oxide as end product,except [Zn(OAc)(L3)(HL3)]2 in which case a well-defined intermediate was observed between 570–620 K. On the basis of the IR spectra and elemental analysis data of the intermediate a decomposition scheme is proposed.

Transition metal complexes with the thiosemicarbazide-based ligands—I. Nickel(II) complexes with the quadridentate ligands based on S-methylisothiosemicarbazide; X-ray crystal structure of (acetyl-acetone N(1)-salicylidene-S-methylizothiosemicarbazonato) nickel(II)

Abstract The reaction of a warm ethanolic solution of [Ni(SALSMeTSC-H)Py]Cl·0.5Py (SALSMeTSC = salicylaldehyde S-methylisothiosemicarbazone) with salicylaldehyde and acetylacetone (HACAC), yielded the corresponding square-planar complexes [Ni(SAL 2 SMeTSC-2H)] ( A ) and [Ni(SALACACSMeTSC-2H)] ( B ) (SAL 2 SMeTSC, and SALACACSMeTSC = quadridentate 2O2N ligand: N(1),N(3)- bis (salicylidene)-S-methylisothiosemicarbazide, and acetylacetone N(1)-salicylidene-S-methylisothiosemicarbazone, respectively). An X-ray analysis of complex B showed that in the reaction of the starting complex with HACAC a rearrangement of the salicylaldehyde moiety takes place (while the CN(3) bond of the azomethine group is ruptured) and its binding to the N(1) nitrogen. At the same time, HACAC is simultaneously bonded to the liberated N(3)-nitrogen of the hydrazine fragment. Crystal data for the complex B (NiC 14 H 15 N 3 O 2 S) are: M r = 348.0, orthorhombic, space group Pna2 1 , a = 7.484(3), b = 21.995(8), c = 8.866(3) A; V = 1459.44 A 3 , Z = 4, F (000) = 720, Dc = 1.58 g cm −1 , Do = 1.56 g cm −1 , μ(MoKα) = 14.45 cm −1 . The structure was solved by the heavy-atom method and refined anisotropically to an R value of 0.078 for 1174 non-zero reflections. The complex molecules are planar, the NiNi distance of nearest molecules being about 3.76 A. The compounds have been characterized by elemental analysis as well as by IR and electronic spectra.

Synthesis and molecular structure of salicylaldehydeS-methyl-isothiosemicarbazone, C9H11N3OS

AbstractThe crystal structure of salicylaldehyde S-methylisothiosemicarbazone together with the synthesis applied are reported: C9H11N3OS, monoclinic, P21/n,a=5.169(4),b=16.853 (10),c=11.367(5)Å, β=92.48(1)°,V=989.3(18)Å3,Z=4,dx=1.405g cm−3. The structure was solved by the heavy atom method and refined anisotropically to a residualR=0.046. The molecule is practically co-planar. There is only one basic difference between the title compound H2L and its deprotonated and complexed forms reported hitherto: the nearly 180° difference in rotation about the formal double bond C1—N2. The molecules form hydrogen bonded dimers around