Showing papers in "Transition Metal Chemistry in 2006"

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

Abstract: 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

Crystal Structure of 2-[2-hydroxy-3-methoxyphenyl]-3-[2-hydroxy-3-methoxybenzylamino]-1,2-dihydroquinazolin-4(3H)-one and the Synthesis, Spectral and Thermal Investigation of its Transition Metal Complexes

Abstract: A new 1,2-dihydroquinazolin-4(3H)-one ligand, 2-[2-hydroxy-3-methoxyphenyl]-3-[2-hydroxy-3-methoxybenzylamino]-1,2-dihydroquinazolin-4(3H)-one (Hmpbaq), formed by the condensation of 2-aminobenzoylhydrazide with 2-hydroxy-3-methoxybenzaldehyde and its copper(II), nickel(II), cobalt(II), manganese(II), zinc(II) and cadmium(II) complexes, have been synthesized. Their structures have been elucidated on the basis of elemental analyses, conductance measurements, magnetic moments, spectral (i.r., 1H-n.m.r., u.v.–vis., e.p.r. and FAB-mass) and thermal studies. The formation of 1,2-dihydroquinazolin-4(3H)-one rather than hydrazone in the reaction of 2-aminobenzoylhydrazide with 2-hydroxy-3-methoxybenzaldehyde is confirmed by the 1H-n.m.r. spectra and single crystal X-ray diffraction studies. The tridentate behavior of the ligand was proposed on the basis of spectral studies. X-band e.p.r. spectra of the copper(II) and manganese(II) complexes in the polycrystalline state at room temperature and liquid nitrogen temperature were recorded and their salient features are reported. Thermal stabilities of the manganese(II) and zinc(II) complexes have been studied.

Template synthesis, spectroscopic studies and biological screening of macrocyclic complexes derived from thiocarbohydrazide and benzil

Abstract: A novel series of complexes of the type [M(TML)X2]; where TML is a tetradentate macrocyclic ligand; M = Co(II), Ni(II), Cu(II) or Zn(II); X = Cl−, CH3COO− or NO3− have been synthesized by template condensation of benzil and thiocarbohydrazide in the presence of divalent metal salts in methanolic medium. The complexes have been characterized with the help of elemental analyses, conductance measurements, molecular weight determination, magnetic measurements, electronic, NMR, infrared and far infrared spectral studies. Electronic spectra along with magnetic moments suggest the six coordinate octahedral geometry for these complexes. The low value of molar conductance indicates them to be non-electrolytes. The biological activities of metal complexes have been tested in vitro against a number of pathogenic bacteria to assess their inhibiting potential.

X-ray Crystal Structure of the N -(2-hydroxy-1-naphthalidene)phenylglycine Schiff Base. Synthesis and Characterization of its Transition Metal Complexes

Abstract: The design and synthesis of the new amino acid Schiff base, N-(2-hydroxy-1-naphthalidene)phenylglycine (Hhnpg) has been described along with the single crystal X-ray crystallographic studies. Copper(II), nickel(II), cobalt(II), manganese(II) and zinc(II) complexes of Hhnpg were synthesized for the first time, and were characterized on the basis of elemental analysis, conductivity measurements, spectral (i.r., 1H-n.m.r., u.v.–vis., e.p.r.), magnetic and thermal studies. The i.r. spectral studies of all the complexes exhibit a similar feature about the ligating nature of the ligand to the metal ions and reveal that the ligand has coordinated through the carbonyl oxygen, azomethine nitrogen and deprotonated hydroxyl oxygen. The conductance data of the complexes suggest them to be non-electrolytes. The microbial activity of the ligand and the complexes was investigated.

Mixed-ligand copper(II) complexes: Investigation of their spectroscopic, catalysis, antimicrobial and potentiometric properties

Abstract: Schiff base ligands HL1–HL6 have been prepared from the reaction of 2,6-diformyl-4-t-butylphenol and 2,6-di-formyl-4-methylphenol with various aromatic amines in ethanolic solution. The Schiff base ligands 2,2′-dipyridine (dp) mixed-ligand CuII complexes have been obtained. Mixed-ligand CuII complexes containing the dp ligand have ionic nature and they conduct the electricity in solution media. The complexes have been obtained in two different forms: one of them is [Cu2(Ln)Cl3] (n: 1, 2, 3, 4, 5 and 6) and other complexes have the general formula [Cu2(Ln)(dp)2]3Cl. Ligands and their complexes have been characterized by elemental analyses, FT-IR, electronic spectra, molar conductance, 1H(13C)-n.m.r. and mass spectral data. Their stoichiometric protonation constants have been determined potentiometrically in dioxan using a combined pH electrode at 25 °C, under a nitrogen atmosphere. For the calculation of the protonation constants, PKAS computer programme has been used. The effects of the substituents on the protonation constants and the additivities of these effects are discussed. The antimicrobial activity studies of the ligands and their complexes have been studied against the Bacillus megaterium, Micrococcus luteus, Corynebavterium xenosis, Enterococcuc faecalis, bacteria and Saccoramyces cerevisia, yeast. The catalytic properties of the complexes have been studied on the ascorbic acid, catechol and 2,6-di-t-butylphenol substrates. Thermal behaviour of the complexes has been studied by thermal techniques.

Synthesis and characterization of some Schiff base transition metal complexes derived from vanillin and L(+)alanine

Abstract: The cobalt(II), nickel(II), copper(II) and zinc(II)-vanillidene-L(+)alanine complexes were synthesized and characterized by elemental analysis, conductivity measurements, magnetic behavior, infrared, electronic spectral measurements, X-ray powder diffraction and biological studies. The conductance measurements indicate that all the complexes are non-electrolytes. The infrared spectra indicate the coordination of imino nitrogen, phenolic oxygen and carboxylato oxygen atoms. The electronic spectral measurements demonstrate that cobalt(II) and nickel(II)-vanillidene-L(+)alanine complexes are tetrahedral, while copper(II)-vanillidene-L(+)alanine complex has square planar geometry. The cobalt(II) complex is found to be ferromagnetic. The powder XRD studies confirm the crystalline nature of the complexes. The ligand and complexes were less active against PN, PA and BC, whereas copper complex shows moderate activity against AN.

Synthesis, characterization, catalytic, electrochemical and thermal properties of tetradentate Schiff base complexes

Abstract: In this study, the Schiff base ligands H2L1–H2L3 and their CuII, CoII, NiII, FeIII RuIII and VOIV complexes have been prepared and characterized by spectroscopic and analytical techniques All the complexes are mononuclear Keto-enol tautomeric forms of the ligands have been investigated in polar and apolar solvents The ligands favor the keto-form in the C7H8 and C6H14 The C–C coupling reaction of the 2,6-di-t-butylphenol has been investigated by the CoII and CuII complexes Thermal properties of the complexes have been assessed using thermal techniques and similar properties were found In the FeIII and RuIII complexes, firstly, the coordinated water molecule is lost from the complex; in the second step, the chloride ion leaves the molecule in the 300–350 °C temperature range Finally, the complexes decompose to the appropriate metal oxide at the higher temperature ranges The electrochemical properties of the complexes have been studied in the two different solvents (DMF and CH3CN)

Synthesis, Characterization, Electrochemical Properties and Antibacterial Activity of Some Transiton Metal Complexes with [(2-hydroxy-1-naphthaldehyde)-3-isatin]-bishydrazone

Abstract: A bishydrazone was prepared by reacting isatin monohydrazone with 2-hydroxy-1-naphthaldehyde and a series of metal complexes with this new ligand were synthesised by reaction with MnII, FeII, CoII, NiII, CuII and ZnII salts. The complexes were characterised on the basis of elemental analysis, molar conductance, magnetic susceptibility data, u.v.–visible, i.r., e.s.r. and n.m.r. spectral studies, wherever possible and applicable. Analytical data reveal that the nickel(II), copper(II) and zinc(II) complexes possess 1:1 metal–ligand ratios and that manganese(II), iron(II) and cobalt (II) complexes exhibit 1:2 ratios. Infrared spectral data suggest that the bishydrazone behaves as a monobasic tridentate ligand with ONO donor sequence towards the metal ions. X-ray diffraction study of the copper(II) complex indicated an orthorhombic crystal lattice. The e.p.r. spectral data show that the metal–ligand bond has considerable covalent character. The electrochemical behaviour of the copper(II) complex was investigated by cyclic voltammetry (CV). Antibacterial tests of the ligand and the metal complexes were also carried out and it has been observed that the complexes are more potent bactericides than the ligand.

Binuclear Copper(II), Nickel(II) and Cobalt(II) Complexes with N2O2 Chromophores of Glycylglycine Schiff-Bases of Acetylacetone, Benzoylacetone and Thenoyltrifluoroacetone

Abstract: Binuclear copper, nickel and cobalt complexes of the Schiff-bases obtained by condensation of glycylglycine with acetylacetone, benzoylacetone, dibenzoylmethane and thenoyltrifluoroacetone were prepared by template synthesis. The complexes were characterized by elemental analysis, conductivity measurements, magnetic moments, i.r., u.v.–vis. spectra, e.s.r., X-ray diffraction, t.g.a., d.t.a. and d.s.c. thermal analysis. All the complexes are non-electrolytes with low magnetic moments that indicate spin–spin or antiferromagnetic exchange interactions. Spectral properties support square planar and square pyramidal or trigonal bipyramidal structure provided by the N2O2 chromophores. E.s.r. spectra of the copper complex confirm the binuclear structure and the presence of magnetic interaction. Thermal studies supported the chemical formulation of these complexes and showed that they decompose in three to four steps depending on the type of ligand. Activation energies Ea and enthalpies ΔH, associated with the thermal decomposition of the complexes were calculated and correlated with the type of complexed metal. A mechanism for thermal decomposition is proposed for the complexes.

The preparation, characterization and biological activity of palladium(II) and platinum(II) complexes of tridentate NNS ligands derived from S-methyl- and S-benzyldithiocarbazates and the X-ray crystal structure of the [Pd(mpasme)Cl] complex

Abstract: New complexes of general formula, [M(NNS)Cl] (M = PdII, PtII; NNS = anionic forms of the 6-methyl-2-formylpyridine Schiff bases of S-methyl- and S-benzyldithiocarbazates) have been prepared and characterized by a variety of physico-chemical techniques. Based on conductance and spectral evidence, a square-planar structure is assigned to these complexes. The crystal and molecular structure of the [Pd(mpasme)Cl] complex (mpasme=anionic form of the 6-methyl-2-formylpyridine Schiff base of S-methyldithiocarbazate) has been determined by X-ray diffraction. The complex has a distorted square-planar geometry with the ligand coordinated to the palladium(II) ion via the pyridine nitrogen atom, the azomethine nitrogen atom and the thiolate sulfur atom; the fourth coordination position around the palladium(II) ion is occupied by the chloride ligand. The distortion from a regular square-planar geometry is ascribed to the restricted bite angle of the ligand. Both the Schiff bases exhibit strong cytotoxicity against the human ovarian cancer (Caov-3) cell lines, the S-methyl derivative being two times more active than the S-benzyl derivative. The [Pt(mpasme)Cl] complex is moderately active but the palladium(II) complex is weakly active against this cancer. None of the complexes of Hmpsbz are active against Caov-3. The Schiff base, Hmpasme exhibits moderate activity against the bacteria, MRSA, P. aeruginosa and S. typhimurium but is inactive against B. subtilis. Coordination of the ligand with palladium(II) substantially reduces its activity. The Schiff base, Hmpasbz and its palladium(II) and platinum(II) complexes are inactive against these bacteria. The Schiff bases and their palladium(II) and platinum (II) complexes are inactive against the pathogenic fungi, C. albican, Aspergillus ochraceous and Saccharomyces cerevisiae.

Structural and mechanistic aspects of platinum anticancer agents

Abstract: After the discovery of the anticancer activity of cisplatin many studies have focused on elucidating its mechanism of action. The antitumor effects of platinum complexes originate from their interaction with DNA, which causes interference with normal transcription or DNA replication. Pt–DNA adducts produced by cisplatin and many of its analogues are almost identical, and would explain their similar patterns of tumor sensitivity and susceptibility to resistance. However, platinum compounds bearing trans-amine (ammine) ligands, and those of multinuclear Pt complexes give rise to radically different DNA–Pt adducts. Platinum–sulfur interactions are associated with undesired phenomena such as resistance and toxicity. Modern multinuclear n.m.r. approaches are very powerful for the investigation of thermodynamics and kinetics of the reactions of metal compounds with biomolecules, and it is possible to study the coordination chemistry of platinum drugs under physiological relevant conditions. In this review biocoordination chemistry of platinum anticancer drugs and various mechanistic aspects related to the antitumor effects of platinum complexes have been explained.

Physicochemical and biological characterization of transition metal complexes with a nitrogen donor tetra-dentate novel macrocyclic ligand

Abstract: A novel tetradentate nitrogen donor [N4] macrocyclic ligand, i.e. 3,5,13,15,21,22-hexaaza-2,6,12,16-tetramethyl-4,14-dithia-tricyclo[15.3.1.1(7–11)]docosane-1(21),2,5,7,9,11(22),12,15,17,19-decaene, has been synthesized. Mn(II), Co(II), Ni(II) and Cu(II) complexes with this ligand have been prepared and subjected to elemental analyses, molar conductance measurements, magnetic susceptibility measurements, mass, 1H-n.m.r. (Ligand), i.r., electronic, and e.p.r. spectral studies. On the basis of molar conductance the complexes may be formulated as [M(L)X2] and [Ni(L)]X2 [where M = Mn(II), Co(II) and Cu(II), and X = Cl− and NO 3 − ] due to their nonelectrolytic nature in dimethylsulphoxide (DMSO). All the complexes are of the high spin type and are six coordinated. On the basis of i.r., electronic and e.p.r. spectral studies an octahedral geometry has been assigned to Mn(II) and Co(II), square planar for Ni(II) complexes, and tetragonal for Cu(II) complexes. The antimicrobial activities of the ligand and its complexes, as growth inhibiting agents, have been screened in vitro against several species of bacteria and plant pathogenic fungi.

Biologically Relevant Macrocyclic Complexes of Copper Spectral, Magnetic, Thermal and Antibacterial Approach

Abstract: Copper(II) macrocyclic complexes have been synthesized with five novel ligands: L1-1,7,10,16-tetraaza-2,6,11,15-tetraone-4,13-dithiacycloocta-decane, L2-1,7,11,17-tetraaza-2,6,12,16-tetraone-4,14-dithia-cyclocosane, L3-1,7,10, 13,19,22-hexaaza-2,6,14,18-tetraone-4,16-dithiacyclo-tetracosane, L4-1,7,14,20,tetraaza-2,6,15,19-tetraone-4,17,di- thiatricyclo [22, 4, O21,26, O8,13] hexacosa-8,10,12,21,23,25-hexene, L5- 1,7,13,19,25,26-hexaaza-2,6,14,18 tetraone-4,16 dithia tricyclo [23, 3, 1, I8,12] hexacosa [8(26), 10, 12, 20(25), 22, 24] hexane and characterized by elemental analysis, molar conductance, magnetic susceptibility, i.r, u.v.–vis, EPR spectral studies, thermal studies and electrochemical properties. The molar conductance measurements of the complexes in DMSO correspond to 1:2 electrolytes. g-Values are calculated for all of the complexes in the polycrystalline form as well as in DMSO solution. On the basis of i.r, electronic and EPR spectral studies a square planar geometry has been assigned to these complexes. Cyclic voltammograms for all the complexes are similar to quasi-reversible redox processes CuIICuII⇆CuIICuI⇆CuICuI. The complexes were also evaluated against the growth of bacteria (S. fecalis and E.coli) in vitro.

Synthesis and characterization of new azo-linked Schiff bases and their cobalt(II), copper(II) and nickel(II) complexes

Abstract: Azo compounds were prepared by the reaction between benzenediazonium chloride and 4-amino-5-hydroxy-2,7-naphthalenedisulfonic acid monosodium salt under alkaline conditions. Two new azo-linked Schiff base ligands, 4-(3-methoxysalicylidene)-5-hydroxy-6-(2-hydroxyphenylazo)-2,7-naphthalene disulfonic acid disodium salt (H2L) and 4-(3-methoxysalicylidene)-5-hydroxy-6-(2-hydroxy-4-cholorophenylazo)-2,7-naphthalenedisulfonic acid disodium salt (H2L1), have been synthesized. Also, the new CuII, NiII and CoII complexes of the azo-linked Schiff base ligands were prepared and characterized by infrared spectra, UV–Vis, 1H- and 13C-n.m.r., attached proton test (APT) and distortionless enhancement by polarization transfer (DEPT) and atomic absorption spectroscopy, mass spectrocopy, elemental analyses, thermogravimetric analysis, conductivity and magnetic measurements. It was determined that the synthesized ligands were comprised of six-membered rings due to intramolecular hydrogen bonding. The results suggested that condensation of the azo-derivative compounds and o-vanillin in a 1:1 molar ratio produces mononuclear Schiff base ligands with an ONO donor set. Preliminary histological studies were made. Magnetic moment studies showed that all complexes have a tetrahedral configuration.

Synthesis and characterization of cobalt(II) and nickel(II) complexes of some Schiff bases derived from 3-hydrazino-6-methyl[1,2,4] triazin-5(4H)one

Abstract: Cobalt(II) and nickel(II) complexes of bidentate and tridentate Schiff bases derived from the condensation of 3-hydrazino-6-methyl[1,2,4]triazin-5(4H)one and aromatic aldehyde derivatives were synthesized and characterized. Elemental and thermal analyses as well as i.r., electronic spectra, molar conductance and magnetic moment measurements were utilized for the investigation of the complexes. From these investigation data, the structural formulae, the mode of bonding, and geometry of the complexes were obtained. The photolysis of the complexes was investigated. The photolysis is enhanced by the presence of H2O2 due to the hydroxyl radicals generated during the photochemical reaction. Mechanisms of the pyrolysis and the photolysis of the complexes are suggested.

Synthesis, Characterization and the Antioxidative Activity of Copper(II), Zinc(II) and Nickel(II) Complexes with Naringenin

Abstract: New complexes of Cu(II), Zn(II) and Ni(II) with naringenin have been synthesized and characterized on the basis of elemental analyses, molar conductivities, 1H-n.m.r., i.r. spectra, u.v. spectra, thermal analyses, and fluorescence spectra. In addition, the suppression ratio for O2−· (a) and OH· (b) of the complexes were studied by spectrophotometric methods. The results show that the effect of the Cu(II)-complex IC50 (a) = 0.003 μm, IC50 (b) = 0.06 μm is the most remarkable, and the average scavenger ability of the complexes (IC50=0.06–2.67μm) against OH· is higher than that of the ligand (IC50 = 28.5 μm). Taken together, these results indicate that the scavenger effect can be enhanced by the formation of metal-ligand coordination complexes, and the transition-metal ions may have differential and selective roles.

Synthesis, spectral characterization and electrochemical properties of new vic-dioxime complexes bearing carboxylate

Abstract: Three new vic-dioxime ligands, [N-(ethyl-4-amino-1-piperidine carboxylate)-phenylglyoxime (L1H2), N-(ethyl-4-amino-1-piperidine carboxylate)-glyoxime (L2H2), and N,N′-bis(ethyl-4-amino-1-piperidine carboxylate)-glyoxime (L3H2)], and their Co(II) with Cu(II) metal complexes, were synthesized for the first time. Mononuclear complexes of these ligands with a 1:2 metal-ligand ratio were prepared with Co(II) and Cu(II) salts. The BF 2 + -capped Co(II) and mononuclear complexes of the vic-dioxime were prepared for [Co(L1·BF2)2] and [Co(L2·BF2)2]. The ligands act in a polydentate fashion bonding through nitrogen atoms in the presence of a base, as do most vic-dioximes. The cobalt(II) and copper(II) complexes are non-electrolytes as shown by their molar conductivities (Λ M ) in DMF. The structures of the ligands and complexes were determined by elemental analyses, FT-i.r., u.v.–vis., 1H- and 13C-n.m.r. spectra, magnetic susceptibility measurements, and molar conductivity. The comparative electrochemical studies show that the stabilities of the reduced or oxidized species and the electrode potentials of the complexes are affected by the substituents attached on the oxime moieties of the complexes.

Synthesis and Characterization of Bis(Macrocyclic) Nickel(II) Complexes Containing Aromatic Nitrogen–Nitrogen Linkers Produced by Template Condensation

Abstract: Bis(macrocyclic)dinickel(II) complexes containing phenylene bridges between 16-membered pentaaza macrocyclic subunits have been synthesized via one-pot template condensation of nitrogen–nitrogen linker (1,4-phenylenediamine; benzidine; 4,4′-diaminodiphenylmethane; 4,4′-diaminodiphenylether; 4,4′-diaminodiphenylsulfone), formaldehyde, 1,3-diaminopropane, nickel(II) and 2,4-pentanedione in a 1:4:4:2:2 molar ratio. Elemental analyses, i.r., u.v.–vis, H-n.m.r. spectroscopy, cyclic voltametry, conductometric and magnetic measurements have been used to characterize the new complexes.

Synthesis, spectral characterization, biological and fluorescence studies of lanthanum(III) complexes with 3-substituted-4-amino-5-hydrazino-1,2,4-triazole Schiff bases

Abstract: Some lanthanum(III) complexes have been synthesized by reacting lanthanum(III) nitrate with Schiff bases derived from 3-substituted-4-amino-5-hydrazino-1,2,4-triazole and substituted salicylaldehydes. All these complexes are soluble in DMF and DMSO and the low molar conductance values observed indicates that they are non-electrolytes. Elemental analyses suggest the complexes have 1:1 stoichiometry of the type La · L · NO3 · H2O, and they were characterized further by spectral and thermogravimetric methods. Fluorescence spectra of one of the representative Schiff bases (II) and its lanthanum(III) complex were investigated in various solvents; the complexes were evaluated for their biological activity.

Transition metal complexes of propranolol dithiocarbamate : synthesis, characterization, analytical properties and biological activity

Abstract: Propranolol dithiocarbamate (PDTC) and its complexes with Cu(II), Co(II), Ni(II), Zn(II) and Cd(II) have been synthesized and characterized by elemental analyses, FT-IR, electronic spectra, atomic absorption spectra, molar conductance, mass and 1H-n.m.r. spectral data. Information on the stoichiometry of the complexes was obtained from the continuous variation method (Job’s method). The thermal decomposition behaviour of PDTC metal complexes was investigated in a nitrogen atmosphere using TG and DTA techniques. The antimicrobial activity studies of the metal complexes have been recorded against the Bacillus megaterium, Bacillus brevis, Yersinia enterocolitica, Micrococcus luteus, Pseudomonas aeruginosa, Enterococcus faecalis, Kluyveromyces marxianus, Candida tropicalis, Candida albicans and Kluvyeromyces fragilis.

Spectroscopic Characterization and Catalytic Activity of Some Cu(II)-thiosemicarbazide Complexes

Abstract: The complexes of thiosemicarbazide (HTS) have been prepared and characterized by spectral, thermal and magnetic studies. The deprotonation constant of HTS and the formation constants of its complexes were evaluated pH-metrically. The Cu(II) acetate-HTS system gave high stability. The catalytic activity of Co(II), Ni(II) and Cu(II) complexes was tested to decompose H2O2. The Co(II) complex has no activity whereas the Cu(II) complex was found to be more active than Ni(II). The different Cu(II) complexes were tested; [Cu2(TS)(OH)2(OAc)] was highly active. All parameters affecting the reaction rate (concentration of H2O2, weight of catalyst, temperature and pH) were studied and the optimum conditions were evaluated. Attempts to increase the activity of [Cu2(TS)(HO)2(OAc)] by mixing with superconducting cuprate sample, Nd0.1Y0.9Ba2Cu3O7-δ, will be the subject of further studies.

Spectroscopic and biochemical studies of some manganese(II), oxovanadium(V) and dioxomolybdenum(VI) complexes S/O and N donor agents synthesized under microwave conditions

Abstract: The synthesis of some new manganese(II), oxovanadium(V) and dioxomolybdenum(VI) complexes with 5-chloro-1,3-dihydro-3-[2-(phenyl)-ethylidene]-2H-indol-2-one-hydrazinecarbothioamide (L1H) and 5-chloro-1,3-dihydro-3-[2-(phenyl)-ethylidene]-2H-indol-2-one-hydrazinecarboxamide (L2H) were carried out in unimolar and bimolar ratios. All the new derivatives have been characterized by elemental analyses, molecular weight determinations, molar conductance, magnetic measurements, i.r., 1H-n.m.r. and e.s.r. studies. The i.r. and n.m.r. spectral data suggest the involvement of sulphur/oxygen and azomethine nitrogen in coordination to the central metal ion. The magnetic moment values of the manganese(II) complexes are in the 5.85–6.13 B.M. range, suggesting a high spin state in these complexes. Based on these spectral studies tetrahedral geometry for the manganese(II) complexes and octahedral geometry for the molybdenum complexes has been proposed. In the case of the oxovanadium complexes vanadium is in the penta and hexa coordinated environments. Compounds have been synthesized in an open vessel under microwave irradiation (MWI) using a domestic microwave oven. The reaction time decreases from hours to minutes with improved yield as compared to conventional heating. The free ligands and their metal complexes have been tested in vitro against a number of microorganisms in order to assess their antimicrobial properties. The results indicate that the ligands and their respective metal derivatives possess antimicrobial properties.

Synthesis, characterization and antibacterial activity of some transition metal cis -3,7-dimethyl-2,6-octadiensemicarbazone complexes

Abstract: The synthesis and characterization of some transition metal cis-3,7-dimethyl-2,6-octadiensemicarbazone (CDOSC) complexes are reported. The ligand CDOSC yields: [ML2 Cl2] and [ML2 Cl2] Cl type complexes, where M = CrIII, MnII, FeIII, CoII, NiII, CuII, ZnII, CdII and HgII, L = CDOSC. Structures of the complexes were determined using elemental analysis, molar conductivity, magnetic measurements, i.r. and electronic, as well as n.m.r spectra. CDOSC acts as a bidentate ligand in all the complexes. All the newly synthesized metal complexes, as well as the ligand, were screened for their antibacterial activity. All the complexes exhibit strong inhibitory action against Gram (+) bacteria Staphylococcus aureus and Gram (−) bacteria Escherichia coli. The antibacterial activities of the complexes are stronger than those of the ligand CDOSC itself.

Synthesis and Antibacterial Activity of Cefixime Metal Complexes

Abstract: Cefixime (H2cefixi) reacts with transition metal(II) ions to give [M(cefixi)(H2O)2] complexes (M = Mn, Co, Ni and Cd) and [Fe(cefixi)Cl(H2O)], which were characterized by physicochemical and spectroscopic methods, and an octahedral geometry is suggested for their structure. The complexes are polymers with high temperature decomposition points and are insoluble in water and common organic solvents. The complexes have been screened for antibacterial activity against several bacteria, and the results are compared with the activity of cefixime.

Spectroscopic characterization and biological activity of salicylaldehyde thiazolyl hydrazone ligands and their metal complexes

Abstract: Two novel bidentate Schiff base ligands, 2-(2-hydroxy-3,5-dichloro/diboromo) benzaldehyde-[4-(3-methyl-3-mesitylcyclobutyl)-1,3-thiazol-2-yl]hydrazone, L1H, L2H and their transition metal complexes are reported. The new ligands and their complexes have been characterized by elemental analyses, ΛM, infrared, u.v.–vis, 1H- and 13C-n.m.r. spectroscopy, and magnetic susceptibility measurements. The thermal properties of all complexes have been investigated by TG technique. The complexes contain two monoanionic, bidentate NO ligands. It was found that all the complexes are mononuclear. Antimicrobial activities of the ligands and their complexes have been tested against five different microorganisms, and some of the complexes were found to be active against some of the microorganisms studied.

Synthesis, Structural Characterization and Chromotropism of a Ni(II) and a Co(II) Compound with Acesulfamate as a Ligand

Abstract: The novel bis(acesulfamato-O)tetraaquanickel(II) and bis(acesulfamato-N)tetraaquacobalt(II) complexes have been synthesized and characterized by elemental analyses, magnetic measurements, u.v.–vis and FT-IR spectra. The thermal behavior of the complexes was also studied by simultaneous TG, DTG and DTA methods in a static air atmosphere. The crystal structure of bis(acesulfamato-O)tetraaquanickel(II) complex has been identified by single-crystal X-ray diffraction analyses. The acesulfamate ligand (acs) acts as an O-donor through the carbonyl oxygen as a monodentate ligand in the Ni(II) complex. The Ni(II) ion structure resides on a two-fold axis and is coordinated by four aqua ligands defining the basal plane, and by two monodentate acesulfamate ligands occupying the axial positions. The chromotropism of both complexes has been studied using thermal and spectral analysis. The bis(acesulfamato-N)tetraaquacobalt(II)complex is found to be very soluble in water and organic solvents and exhibits a reversible thermochromism from pink to violet depending on deaquation, which occurs in two steps, in the solid state. The bis(acesulfamato-O)tetraaquanickel(II) complex has shown two thermochromic properties one of which is a reversible and changes the color from green to yellow by an endothermic effect, whereas the other one is irreversible and changes from yellow to brown depending on deaquation, in the solid state. The bis(acesulfamato-N)tetraaquacobalt(II) complex exhibits solvatochromism in solvents with different donor number and ionochromism in the presence of various cations in solution.

Metallosurfactants of Chromium(III) Coordination Complexes. Synthesis, Characterization and Determination of CMC Values

Abstract: A number of mixed ligand chromium(III)–surfactant coordination complexes, of the type cis-[Cr(en)2(A)X]2+ and cis-α-[Cr(trien)(A)X]2+ (A = Dodecyl or Cetylamine; X = F−, Cl−, Br−) were synthesized from the corresponding dihalogeno complexes by ligand substitution. These compounds form foam in aqueous solution when shaken. The critical micelle concentration (CMC) values of these surfactant metal complexes in aqueous solution were obtained from conductance measurements. Specific conductivity data (at 303, 308 and 313 K) served for evaluation of the temperature-dependent critical micelle concentration (cmc) and the thermodynamics of micellization (Δ G m 0 , Δ H m 0 and Δ S m 0 ).

Unsymmetrical Tetradentate Schiff Base Complexes Derived from 2,3-diaminophenol and Salicylaldehyde or 5-bromosalicylaldehyde

Abstract: Salicylaldehyde or 5-bromosalicylaldehyde reacted with 2,3-diaminophenol in absolute EtOH in a 2:1 molar ratio to give new unsymmetrical Schiff bases (H2L). The bases were used as ligands to coordinate Mn(III), Ni(II) and Cu(II) chlorides leading to [MnIIIClL] · EtOH and [MIIL] or [MIIL] · 2H2O (M = Ni or Cu) complexes. Their structures were determined using mass spectroscopy, IR, u.v.–vis and 1H-n.m.r. The cyclic voltammetry in acetonitrile showed irreversible waves for both ligands. Under the same experimental conditions, the complexes exhibited mainly the non-reversible reduction of the Ni(II) or Cu(II) ion to Ni(0) or Cu(0), while the reduction of Mn(III) to Mn(II) was found to be a quite reversible phenomenon.

Synthesis and Biological Activity of Novel (E,E)-vic-dioximes

Abstract: A novel vic-dioxime ligand containing the thiourea group, (4E,5E)-1,3-bis{4-[(4-methylphenylamino)methyl] phenyl}- 2-thiooxaimidazoline-4,5-dione dioxime, (4) mmdH2 has been prepared from N,N′-bis{4-[(4-methylphenylamino)methyl]phenyl}thiourea, (3) mft and cyanogen di-N-oxide. Mononuclear [M(mmdH)2], where M = NiII, CoII and CuII complexes of the (4) mmdH2 bidentate ligand have been obtained with a 1:2 metal:ligand ratio, as do most the vic-dioximes. The complexes are formed by coordination of N, N atoms of the ligand. The vic-dioxime ligand and its some transition metal complexes have been characterized by elemental analyses, molar conductance data, magnetic susceptibility, i.r., 1H-n.m.r and u.v.–vis. spectroscopy. Conductivity measurements have shown that mononuclear complexes are non-electrolytes. In addition, the ligands and metal complexes were screened for antibacterial and antifungal activities by agar well diffusion techniques using DMF as solvent.

Three Novel Rare-earth Complexes with Nitronyl Nitroxide Radical [RE(hfac)3 (NITPhOCH3)2] [RE = GdIII, YIII and ErIII]: Syntheses, Crystal Structures and Magnetic Properties

Abstract: Three novel isomorphous complexes of formula [RE(hfac)3(NITPhOCH3)2], where RE = GdIII, YIII and ErIII; hfac = hexafluoroacetylacetonate; NITPhOCH3 = 4′-methoxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, were synthesized, structurally and magnetically characterized. The crystal structure consists of isolated molecules where the nitronyl nitroxide radicals act as monodentate ligands towards RE(III) through the oxygen atom of the N–O group. The magnetic properties of the complexes were studied by measuring their magnetic susceptibilities at various temperatures in the 5–300 K range. The analyses of these magnetic measurements showed that the spin coupling between the gadolinium ion and the radicals in the GdIII complex is ferromagnetic, while antiferromagnetic superexchange interaction exists between the two radicals in the GdIII and YIII complexes. The ErIII complex reveals an overall intramolecular antiferromagnetic exchange interaction.