Showing papers in "Transition Metal Chemistry in 2008"

Synthesis and characterization of transition metal complexes of N ′-[(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)methylene]thiophene-2-carbohydrazide

Abstract: A hydrazone ligand (HL) containing the thiophene moiety has been prepared via condensation of thiophene-2-carbohydrazide with 1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazole-4-carbaldehyde. The complexes of copper(II), nickel(II), cobalt(II), manganese(II), zinc(II), palladium(II), iron(III), ruthenium(III), uranyl(VI), and titanium(IV) with the ligand were prepared in good yield from the reaction of the ligand with the corresponding metal salts. The ligand and complexes were characterized using infrared, mass spectra, nuclear magnetic resonance, electronic absorption spectra, electron spin resonance, and magnetic moment measurements as well as elemental and thermal analyses. The results showed that the complexes are enolic by nature, whilst the ratio between the metal ion and the ligand depends on the acidity of the metallic ions and their oxidation numbers.

Synthesis, characterization, DNA binding and nuclease activity of binuclear copper(II) complexes of cuminaldehyde thiosemicarbazones

Abstract: Binuclear copper(II) complexes of thiosemicarbazones derived from cuminaldehyde (p-isopropyl benzaldehyde) and substituted thiosemicarbazides NH2NHC(S)NHR, where R = H, Me, Et or Ph have been synthesized and characterized. The ESR indicates that the dissociation of dimeric complex into mononuclear [Cu(L)Cl(DMSO)3] units in polar solvents like DMSO, where L = monoanionic thiosemicarbazone. The molecular ion peak in the LC-MS coincides with the formula weight of the complexes. The absorption titration studies revealed that each of these complexes is an avid binder to calf thymus-DNA. The apparent binding constants are in the order of 107–108 M−1. The nucleolytic cleavage activities of the ligands and their complexes were assayed on pUC18 plasmid DNA using gel electrophoresis in the presence and absence of H2O2. The ligands showed increased nuclease activity when administered as copper complexes. All these copper(II) complexes behave as an efficient chemical nucleases with hydrogen peroxide activation. These studies revealed that the complexes exhibit both oxidative and hydrolytic chemistry in DNA cleavage.

Copper(II) ion selective electrode based on a newly synthesized Schiff-base chelate

Abstract: A new Cu (II) ion-selective electrode has been fabricated in poly (vinyl chloride) matrix based on a recently synthesized Schiff-base chelate. The addition of sodium tetraphenylborate (NaTPB) and various plasticizers viz. TBP, TEHP, DOS, and CN have been found to substantially improve the performance of the electrode. The membrane of various compositions of the ionophore (I) were investigated and it was found that the best performance was obtained with the membrane having (I): PVC: NaTPB: CN in the ratio 4: 140: 3: 80 (mg). The electrode exhibits a Nernstian response over a wide concentration range (1.9 × 10−6–1.0 × 10−1 M) with 30.0 mV/decade of concentration between pH 3.0 and 7.5. The response time of the electrode is about 12 s and it can be used over a period of 3 months without any divergence in potential. The potentiometric selectivity coefficient values as determined by fixed interference method indicate excellent selectivity for Cu2+ ions over interfering cations. The electrode has also been used successfully in partially non-aqueous media having a 25% (v/v) methanol, ethanol or acetone content without showing any considerable change in the value of slope or working concentration range. The electrode has been used in the potentiometric titration of Cu2+ with EDTA.

Synthesis of iron oxide nanoparticles using chitosan and starch templates

Abstract: Natural polymers like chitosan and starch have been employed as templates for the preparation of iron oxide nanoparticles The templates offer selective binding sites for Fe(II) under aqueous conditions Controlled drying and subsequent removal of the template backbone enables the synthesis of spatially separated iron oxide nanoparticles The crystalline character of the iron oxide and near narrow particle size distribution pattern have been confirmed through powder XRD, Photon Correlation Spectroscopy, and TEM measurements The crystallite sizes of the particles were found to be 26–35 nm irrespective of the nature of the template

Spectral and biocidal studies of palladium(II) and platinum(II) complexes with monobasic bidentate Schiff bases

Abstract: The monobasic bidentate Schiff base complexes of palladium(II) and platinum(II) derived from 1H-indol-2,3-dione thiosemicarbazone (L1H) and 1H-indol-2,3-dione semicarbazone (L2H) have been characterized on the basis of elemental analysis, molecular weight determinations, i.r., 1H n.m.r. and u.v. spectral studies. Based on these studies a square planar environment around the metal atoms has been proposed. Antimicrobial effects of both the ligands and their complexes on different species of pathogenic fungi and bacteria have been recorded and these are found to possess significant fungicidal and bactericidal properties.

Ruthenium(II) complexes containing 2,9-dimethyl-1,10-phenanthroline and 4,4′-dimethyl-2,2′-bipyridine as ancillary ligands: synthesis, characterization and DNA-binding

Abstract: Two new Ruthenium (II) polypyridyl complexes [Ru(dmp)2(ipbp)](ClO4)2 (1) (dmp = 2,9-dimethyl-1,10-phenanthroline, ipbp = 3-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)-4H-1-banzopyran-2-one) and [Ru(dmb)2(ipbp)](ClO4)2 (2) (dmb = 4,4′-dimethyl-2,2′-bipyridine) have been synthesized and characterized by elemental analysis, FAB-MS, ES-MS and 1H NMR and cyclic voltammetric methods. The DNA-binding behaviors of these complexes were investigated by spectroscopic titration, viscosity measurements, and thermal denaturation. Absorption titration and thermal denaturation studies reveal that these complexes are moderately strong binders of calf thymus DNA (CT-DNA). Viscosity measurements show that the complexes 1 and 2 interact with CT-DNA by intercalative mode. The DNA-binding affinity of the complex 2 is larger than that of complex 1.

Biologically active 2-thione-4,6-diamino-5-hydroxypyrimidine transition metal complexes

Abstract: New complexes of 2-thione-4,6-diamino-5-hydroxypyrimidine (HTDAHP) with Fe(III), Ni(II), Ag(I) and Ru (II) are described. IR, 1H-NMR and mass spectra, conductivity, magnetic and thermal measurements of the complexes are reported and their structures discussed. HTDAHP behaves as a bidentate ligand, forming five membered hydroxyl-amino chelates or four-membered cyclic nitrogen-sulphur chelates without any participation of the pendant amino or hydroxy groups in complexation. The biological activities of the Ag(I) complexes against fungi (Aspergillus niger and Candida albicans) and bacteria (Staphylococcus aureus and Pseudomonas aeruginosa) have been investigated.

Syntheses, characterization, antimicrobial and genotoxic activities of new Schiff bases and their complexes

Abstract: Two new Schiff base ligands (L1, L2) have been prepared from the reaction of 2,6-diacetylpyridine and 2-pyridinecarboxyaldehyde with 4-amino-2,3-dimethyl-1-phenyl-3-pyrozolin-5-on, and their Co(II), Cu(II), Ni(II), Mn(II), and Cr(III) metal complexes have also been prepared. The complexes are formed by coordination of N and O atoms of the ligands. Their structures were characterized by physico-chemical and spectroscopic methods. The analytical data shows that the metal to ligand ratio in the Schiff base complexes is 1:2. The Schiff base ligands and all complexes were evaluated for their in vitro antibacterial and antifungal activities by the disc diffusion method. In addition, the genotoxic properties of the ligands were studied.

Studies of the electrocatalytic activity of binary palladium ruthenium anode catalyst on Ni support for ethanol alkaline fuel cells

Abstract: In extension to our earlier study on the electro-catalytic activity of binary palladium ruthenium anode catalyst on Ni support for ethanol alkaline fuel cells, we hereby report the optimum loading of Pd Ru electro-deposit and concentration of ethanol for better performance of the system. It is observed that the electro-catalytic activity increases with increase of loading of electro-catalyst on planar Ni foil electrode but decreases with its excess. The order with respect to ethanol and hence its adsorption in the process of its oxidation has been found to be both potential and concentration dependent. The results have been obtained from the studies on cyclic voltammetry, steady state polarization, scanning electron microscopy, energy dispersive X-ray spectroscopy and further analysis of our chronopotentiometric study executed previously. Electrodes constructed by deposition at the rate of current density, 5 mA cm−2 for 10 min and 0.2 M ethanol concentration have been recommended for the better performance of this system.

Studies on ruthenium(II) Schiff base complexes as catalysts for transfer hydrogenation reactions

Abstract: The reactions of [RuHCl(CO)(B)(EPh3)2] (B = EPh3 or Py; E = P or As) and Schiff bases in 1:1 molar ratio led to the formation of [RuCl(CO)(EPh3)(B)(L)] (E = P or As; B = PPh3, AsPh3 or Py; L = Schiff base ligand). The new complexes have been characterized by analytical and spectroscopic (IR, electronic and 1H NMR) data. They have been assigned an octahedral structure. The new complexes were found to catalyse the transfer hydrogenation of ketones.

Synthesis, characterisation and antifungal activity of a series of Cobalt(II) and Nickel(II) complexes with ligands derived from reduced N, N′-o-Phenylenebis(Salicylideneimine)

Abstract: The synthesis and characterisation by elemental analysis, conductivity, FTIR, UV–Visible, ESR and magnetic measurements are described for a series of complexes of nickel(II) and cobalt(II) with three ligands (H2L1–3) derived from reduced N, N′-o-Phenylenebis(salicylideneimine). The complexes formed are identified as neutral species, where the ligands are coordinated through N and O donor atoms. The formulae obtained for the complexes are: [CoL(H2O)2] with octahedral geometry and [NiL] with tetrahedral geometry. Their antifungal activity is evaluated towards human pathogenic fungi including yeasts of the Candida genus, some opportunistic moulds belonging to the Aspergillus, Scedosporium genus and some dermatophytes. The cobalt complexes show a significant growth inhibition of yeasts tested and also to fungi of the genus Scedosporium which is of interest because these fungi are usually poorly susceptible to current antifungal including Amphotericin B and Itraconazole, chosen as reference in this study. The activity data show that the metal complexes are more potent than the parent ligand.

Template synthesis and physicochemical studies of 14-membered hexaazmacrocyclic complexes with Co(II), Ni(II), Cu(II) and Zn(II): a comparative spectroscopic approach on DNA binding with Cu(II) and Ni(II) complexes

Abstract: A new series of 14-membered pendant arm hexaazamacrocyclic complexes of the type [MLX2] · [M = Co(II), Ni(II), Cu(II) or Zn(II) for X = Cl; Co(II), Ni(II), Cu(II) or Zn(II) for X = NO3] has been synthesized by metal template condensation of 1,2-phenylenediamine and 1,4-phenylenediamine with formaldehyde in methanol. The mode of bonding and overall geometry of these complexes have been deduced by elemental analyses, molar conductance values, FT-IR, 1H-NMR, 13C-NMR, EPR, ESI-mass and UV–VIS along with magnetic measurement studies. The fluorescence and UV–VIS studies revealed a significant binding ability to DNA.

Synthesis, characterization and antiprotozoal studies of some metal complexes of antimalarial drugs

Abstract: Metal complexes of the antimalarials trimethoprim (TMP), chloroquine (CQ), and pyrimethamine (pyrm) formulated as [Mn(TMP)Cl2(CH3OH)], [Co(TMP)2Cl2(CH3OH)], [Pt(CQ)2Cl2] and [Cu(pyrm)2(CH3COO)2] have been synthesized and characterized by elemental analysis, magnetic susceptibility measurements, IR and UV-Vis spectroscopy. The IR and electronic spectra are consistent with the proposed geometry for the complexes. The Mn(II) and Pt(II) complexes are four coordinate while the Cu(II) and Co(II) have octahedral geometry. The complexes were tested for in vitro activity against cultures of Trypanosoma cruzi, L. donovani, T. b. rhodesiense and the resistant strains of Plasmodium falciparum to determine their antiprotozoal activities and for their cytotoxicity with L-6 cells. The Pt(II) complex of chloroquine showed enhanced activity against the resistant strain of Plasmodium falciparum.

Synthesis and spectroscopic characterization of asymmetric Schiff bases derived from 4′-formylbenzo-15-crown-5 containing recognition sites for alkali and transition metal guest cations

Abstract: Asymmetric salen-type Schiff base ligands have been synthesized via a stepwise approach. In the first step, mono-Schiff base compounds were prepared by condensation of salicylaldehyde, 2-hydroxy-3-methoxybenzaldehyde, 2-hydroxy-5-methoxybenzaldehyde and 2-hydroxy-1-naphthaldehyde with hydrazine hydrate. These compounds were then reacted with 4′-formylbenzo-15-crown-5 to prepare asymmetric ligands. 1H-NMR spectra indicate that the mono- and asymmetric bis-Schiff base compounds exist in both (E) and (Z) isomeric forms in CDCl3 solution. The asymmetric crown compounds form crystalline 1:1 (Na+:ligand) complexes with sodium perchlorate. Homo-metallic Ni(II) and Zn(II) complexes with 1:2 (metal:ligand) stoichiometries have also been synthesized. The results indicate that the Schiff base ligands coordinate through the azomethine nitrogen and phenolic oxygen.

Synthesis and antibacterial activity of copper(II) complexes with sulphathiazole and cephalosporin ligands

Abstract: Copper(II) reacts with cephalosporins plus sulphathiazole (Hstz) to form the following mixed complexes: [Cu(cefazol)(stz)(H2O)], [Cu(cephalot)(stz)(H2O)2], [Cu(cefotax)(stz)], [Cu(ceftria)(Hstz)] and [Cu(cefepime)(stz)Cl] (Hcefazol = cefazolin, Hcephalot = cephalothin, Hcefotax = cefotaxime and H2ceftria = ceftriaxone) which were characterized by physicochemical and spectroscopic methods. The spectra indicated that most of the cephalosporins are probably acting as monoanionic multidentate chelating agents, the exception being ceftriaxone which is dianionic. The complexes are insoluble in water and common organic solvents and probably have polymeric structures. They have been screened for activity against several bacteria, and the results are compared with the activity of cephalosporins.

Synthesis and structural studies of new Mannich base ligands and their metal complexes

Abstract: The new Mannich bases bis(1,4-diphenylthiosemicarbazide methyl) phosphinic acid H3L1 and bis(1,4-diphenylsemicarbazide methyl) phosphinic acid H3L2 were synthesised from the condensation of phosphinic acid, formaldehyde with 1,4-diphenyl thiosemicarbazide and 1,4-diphenylsemicarbazide, respectively. Monomeric complexes of these ligands, of general formulae K2[CrIII(L n )Cl2], K3[MnII(L n )Cl2] and K[M(L n )] (M = Co(II), Ni(II), Cu(II), Zn(II) or Hg(II); n = 1, 2), are reported. The mode of bonding and overall geometry of the complexes were determined through physico-chemical and spectroscopic methods. These studies revealed octahedral geometries for the Cr(III), Mn(II) complexes, square planar for Co(II), Ni(II) and Cu(II) complexes and tetrahedral for the Zn(II) and Hg(II) complexes.

A mononuclear cobalt(II) hydroxo complex: synthesis, molecular structure, and reactivity studies

Abstract: A novel Co(II) hydroxo complex Co{HB(3-tBu-5-iPrpz)3}(OH) 4 {where HB(3-tBu-5-iPrpz)3 = hydrotris(3-tert-butyl-5-isopropylpyrazol-l-yl)borate} has been prepared and its molecular structure has been determined by X-ray crystallography. This complex is mononuclear with distorted tetrahedral geometry. The reaction of CO2 with Co{HB(3-tBu-5-iPrpz)3}(OH) resulted in the formation of a μ-carbonato bridged binuclear complex [Co{HB(3-tBu-5-iPrpz)3}]2(CO3) wherein the carbonate group is bound to both metal centers in an asymmetrical manner. In order to explore the role of labile metal complexes in promoting ester hydrolysis, complexes [Co{HB(3,5-iPr2pz)3}]2(OH)2 and Co{HB(3-tBu-5-iPrpz)3}(OH) have been used as catalysts in the hydrolysis of both carboxylate as well as phosphate esters. The product of 4-nitrophenylacetate hydrolysis with Co{HB(3-tBu-5-iPrpz)3}(OH) was isolated as four coordinate Co{HB(3-tBu-5-iPrpz)3}(OC6H4-4-NO2) 6, whereas the reaction of 4-nitrophenyltrifluoroacetate with [Co{HB(3,5-iPr2pz)3}]2(OH)2 resulted the formation of the six coordinate Co{HB(3,5-iPr2pz)3}(OC6H4-4-NO2)(MeCN)2 species.

Oxidation of electron deficient olefins using a copper(II) complex based on a bis-benzimidazole diamide ligand

Abstract: New bis-benzimidazole based diamide ligands N, N′-bis(2-methyl benzimidazolyl)-benzene-1,3-dicarboxamide [GBBA] and N-Octyl-N, N′-bis(2-methyl benzimidazolyl)-benzene- 1,3-dicarboxamide [O-GBBA] have been synthesized and utilized to prepare Cu(II) complexes of general composition [Cu(GBBA)X 2] · nH2O and [Cu(O-GBBA)X2] · n H2O, where X is an exogenous anionic ligand (X = Cl−, NO 3 − , SCN−). The oxidation of electron deficient olefins has been investigated using [Cu(O-GBBA)X2] · nH2O as catalyst and TBHP as an alternate source of oxygen. The respective ketonic products have been isolated and characterized by 1H-NMR. The complex [Cu(GBBA)(NO3)2] · 4H2O has been characterized structurally. It crystallizes in a monoclinic space group C2/c. Low temperature EPR spectra have been obtained for the complexes that shows gII > gI > 2.0024, indicating a tetragonal geometry in the solution state. The complexes display a quasi reversible redox wave due to the Cu(II)/Cu(I) reduction process. The E1/2 values shift anodically as NO 3 − < SCN− < Cl−.

Novel vic-dioxime ligands and their poly-metal complexes bearing 1,8-diamino-3,6-dioxaoctane: synthesis, characterization, spectroscopy and electrochemistry

Abstract: Three novel vic-dioxime ligands containing the 1,8-diamino-3,6-dioxaoctane group, N,N′-(1,8-diamino-3,6-dioxaoctane)-p-tolylglyoxime (L1SL1H4), N,N′-(1,8-diamino-3,6-dioxaoctane)-phenylglyoxime (L2SL2H4), and N,N′-(1,8-diamino-3,6-dioxaoctane)-glyoxime (L3SL3H4) have been prepared from 1,8-diamino-3,6-dioxaoctane with anti-p-tolylchloroglyoxime, anti-phenylchloroglyoxime or anti-monochloroglyoxime. Polynuclear complexes [M(L x SL x )] n or [M(L x SL x )(H2O)] n (x = 1, 2 and 3), where M = CuII, CoII, and NiII, have been obtained with 1:1 metal/ligand ratio. The CuII and NiII poly-metal complexes of these ligands are proposed to be square planar, while also the prepared CoII complexes are proposed to be octahedral with two water molecules as axial ligands. The detection of H-bonding in the [Ni(L1SL1)] n , [Ni(L2SL2)] n and [M(L3SL3)(H2O)] n metal complexes by FT i.r. spectra revealed the square planar or octahedral [MN4·H2O)] n coordination of poly-nuclear metal complexes. [MN4] n coordination of the [Ni(L1SL1)] n and [Ni(L2SL2)] n complexes were also determined by 1H-n.m.r. spectroscopy. The ligands and poly-metal complexes were characterized by elemental analyses, FT-i.r., u.v.-vis., 1H and 13C-n.m.r. spectra, magnetic susceptibility measurements, molar conductivity, cyclic voltammetry, and differential pulse voltammetric (DPV) techniques.

Synthesis, electrochemistry, thin-layer UV-vis and fluorescence spectroelectrochemistry of a new salicylaldimine ligand and its copper complex

Abstract: The new asymmetric, fluorescent Schiff-base ligand, N-(pyrene)-salicylaldimine (L), and its copper complex having an ONNO donor set, [Cu(L) 2 ], were synthesized and characterized using elemental analysis, IR, UV-vis, 1H and 13C-NMR spectroscopies. Their electrochemical and spectroelectrochemical behaviors were investigated in a detail by using cyclic voltammetry (CV), square wave voltammetry (SWV), in-situ UV-vis, and fluorescence spectroelectrochemistry. The formation of the complex was monitored by the in-situ fluorescence technique based on the quenching of the fluorescence-probe ligand. Electrochemical studies showed that L exhibits a single irreversible reduction process. However, the SWV indicated that this process was not totally irreversible in the time scale of the measurement. The cathodic peak potential of the reduction process occurred at E pc = −1.35 V vs Ag/AgCl (scan rate: 0.025 Vs−1). On the other hand, [Cu(L) 2 ] showed one quasi-reversible one-electron reduction process in the scan rates of 0.025–0.50 Vs−1, which was assigned to metal-based one-electron process; [Cu(2+)(L)2] + e− → [Cu(+)(L)2]−. The value of half-wave potential (E 1/2) of the reduction process was −0.54 V vs Ag/AgCl (scan rate: 0.025 Vs−1). The time-resolved spectra showed, when the potential (E app = −1.60 V) was applied in a thin-layer cell, that the main and shoulder bands of (L) at 385, 336, and 407 nm almost disappeared and a new band at 443 nm with a shoulder formed during the reduction process. No change was observed on the final spectrum of the totally reduced ligand for long period under nitrogen atmosphere, which indicated that the singly reduced species remained stable and was not accompanied by a chemical reaction in the time scale of the spectroelectrochemical measurement. The spectral changes during the reduction process of [Cu(L) 2 ] confirmed the metal-centered reduction process. The fluorescence intensity of L decreased during the reduction process in the thin-layer cell, as result of the perturbation of the conjugated system of the reduced species.

A new vic-dioxime ligand containing two azo substituents and its mononuclear nickel(II), cobalt(II), and copper(II) complexes; synthesis, characterization, spectroscopic and biological studies

Abstract: A new vicinal dioxime ligand containing azo and thione chromophores, namely 1,3-bis[4-(phenyldiazenyl)phenyl]-2-thiooxaimidazoline-4,5-dione dioxime (bppH2), was synthesized by the reaction of cyanogen di-N-oxide with N,N′-bis(4-phenylazophenyl) thiourea in dichloromethane solution at −10 °C. Mononuclear complexes of bppH2 with nickel(II), cobalt(II), and copper(II) were synthesized. The complexes, [Ni(bppH)2], [Cu(bppH)2], and [Co(bppH)2] were characterized by several techniques using elemental analyses, conductivity measurements, FT-IR, and electronic spectral studies. The data suggest that the ligand coordinates through the N,N atoms, as do most vic-dioximes. The molar conductivities in DMF solution indicate nonelectrolytic nature for the complexes. Antimicrobial activities of the ligand and its metal complexes were estimated for five bacteria, namely Klebsiella pneumoniae, Micrococcus luteus, Mycobacterium smegmatis, Enterobacter cloaca and Bacillus megaterium and three fungi, namely Candida albicans, Kluyveromyces marxianus, and Rhodotorula rubra.

Synthesis, spectral, thermal, solid-state DC electrical conductivity and biological studies of Co(II) complexes with Schiff bases derived from 3-substituted-4-amino-5-hydrazino-1,2,4-triazole and substituted salicylaldehydes

Abstract: A series of Co(II) complexes have been synthesized with Schiff bases derived from 3-substituted-4-amino-5-hydrazino-1,2,4-triazole and substituted salicylaldehydes. These complexes are insoluble in water but more soluble in DMF and DMSO. The complexes have been characterized by elemental analyses, spectral (IR, UV–Vis, 1H-NMR, FAB-mass, fluorescence), magnetic, thermal, solid-state DC electrical conductivity and molar conductance data. The molar conductivity values indicate that they are non-electrolytes. The elemental analyses of the complexes suggest a stoichiometry of the type Co · L1–L16 · 2H2O. The complexes have been considered as semiconductors on the basis of the solid-state DC electrical conductivity data. Fluorescence spectra of one Schiff base and its complex were investigated in various solvents and some of the Schiff bases and their complexes were evaluated for their antimicrobial activities.

Syntheses, structures and electrochemical properties of complexes of nickel(II) with triethylenetetramine and bidentate nitrogen donor co-ligands

Abstract: Three new polyamine Ni(II) complexes, namely [Ni(trien)(phen)](BF4)21, [Ni(trien)(bipy)](ClO4)22 and [Ni(trien)(en)](ClO4)23 [trine = triethylenetetramine, phen = 1,10-phenanthroline, bipy = 2,2′-bipyridyl, en = ethylenediamine] have been synthesized and characterized by physico-chemical and spectroscopic methods. Complexes 1 and 2 crystallize in monoclinic space group P21/c, and possess a distorted octahedral geometry. Significant hydrogen bonding interactions are found in both complexes.

Syntheses, crystal structures, and properties of two salts based on Ni(mnt)2 (mnt2− = maleonitriledithiolate) anion and substituted triphenylphosphonium cation

Abstract: Two new salts, [oClBzTPP] 2 + [Ni(mnt)2]2−(1) and [oClBzTPP]+[Ni(mnt)2]−(2) ([oClBzTPP]+ = 1-(2′-chlorobenzyl)triphenylphosphonium and mnt2− = maleonitriledithiolate) have been prepared and characterized by elemental analyses, UV, IR, MS spectra, single crystal X-ray diffraction, and magnetic susceptibility. The Ni ions of the Ni(mnt)2 anions for 1 and 2 exhibit the square-planar coordination geometry. The Ni(III) ions of 2 form a 1D zigzag alternating magnetic chain within a Ni(mnt) 2 − column through Ni···S, S···S, or Ni···Ni interactions. The C–H···N, C–H···S, C–H···π hydrogen bonds or π···π stacking interactions play important roles in the molecular stabilizing and stacking of 1 and 2. Magnetic susceptibility measurements in the temperature range 1.8−300 K show that 2 exhibits diamagnetic behavior.

Kinetics and mechanism of the reduction of gold(III) by glycine in acetate buffer

Abstract: The kinetics of reduction of tetrachloroaurate(III) by glycine has been spectrophotometrically studied in NaOAc–AcOH buffer in the pH range 3.73–4.77. The reaction is first order with respect to both Au(III) and glycine. Both H+ and Cl− ions have inhibiting effects on the reaction rate. The rate decreases with a decrease in the dielectric constant of the medium. AuCl 4 − and AuCl3(OH)− are presumed to be the predominant oxidizing species under the conditions of the experiment. The reaction of gold(III) and zwitterionic species of glycine proceeds with the intermediate formation of gold(I) and iminic cation and the latter subsequently hydrolyses in a fast step to produce formaldehyde and ammonium ion. Formaldehyde was identified as the only organic product by 1H NMR spectroscopy.

The synthesis, characterization and antimicrobial activity of N,N′-bis(2-thiophenecarboxamido)-1,3-diaminopropane and N,N′-bis (2-furancarboxamido)-1,3-diaminopropane and their Cu(II), Zn(II), Co(III) complexes

Abstract: Metal complexes derived from amides; N,N′-bis(2-thiophenecarboxamido)-1,3-diamino propane (1) and N,N′-bis(2-furancarboxamido)-1,3-diaminopropane (2) were characterized by elemental analysis, spectral (NMR, FT-IR, LC-MS) methods, magnetic moment, molar conductance, and TGA/DTA studies. The complexes were dimeric and have the general formula [ML.Clm.(H2O)n]2Cl2 where M=Cu(II), Zn(II), Co(III); m = 1, 2; n = 0, 1. The antimicrobial activities of the amides and their complexes were studied against the bacteria; Escherichia coli (ATCC 11230), Yersinia enterocolitica (ATCC 1501), Bacillus magaterium (RSKK 5117), Bacillus cereus (RSKK 863), Bacillus subtilis (RSKK 863) and yeast; Candida albicans (ATCC 10239).

Fabrication of an iron(III)-selective PVC membrane sensor based on a bis-bidentate Schiff base ionophore

Abstract: A Fe3+ ion-selective membrane sensor was fabricated from polyvinyl chloride (PVC) matrix membrane containing bis-bidentate Schiff base (BBS) as a neutral carrier, sodium tetraphenyl borate (NaTPB) as anionic excluder, and o-nitrophenyloctyl ether (NPOE) as a plasticizing solvent mediator. The effects of the membrane composition, pH, and additive anionic influence on the response properties were investigated. The best performance was obtained with a membrane containing 32% PVC, 62.5% NPOE, 3% BBS, and 2.5% NaTPB. The electrode shows a Nernstian behavior (slope of 19.3 ± 0.6) over a very wide iron ion concentration range (1.0 × 10−7–1.0 × 10−2 M) and has a low detection limit (7.4 × 10−8 M). The potentiometric response of the sensor is independent of pH of the solution in the pH range 1.9–5.1. The proposed sensor has a very low response time (<15 s) and a good selectivity relative to a wide variety of other metal ions including common alkali, alkaline earth, heavy, and transition metal ions. The electrode can be used for at least 60 days without any considerable divergence in potentials. The proposed sensor was successfully applied as an indicator electrode for the potentiometric titration of 1.0 × 10−2 M Fe3+ ions with a 1.0 × 10−4 M EDTA and the direct determination of Fe3+ in mineral water and wastewater samples.

Synthesis and kinetic studies in aqueous solution on chromium(III) complexes with isocinchomeronic acid—potential new biochromium sources

Abstract: The chromium(III) complexes with a new potential chromium transporting ligand—2,5-pyridinedicarboxylic acid (isocinchomeronic acid, icaH2):[Cr(icaH)3]0, [Cr(icaH)2 (H2O)2]+ and [Cr(icaH)(H2O)4]2+ (where icaH = N,O-bonded isocinchomeronic acid anion), have been obtained and characterized in solution. The [Cr(icaH)3]0 complex undergoes aquation in acidic media to the diaqua-product. Kinetics of this process was studied spectrophotometrically in the 0.1–1.0 M HClO4 range, at I = 1.0 M. The first aquation stage, the chelate-ring opening at the Cr–N bond, is a much faster than the second one. The rate laws are of the form: k obs = k 1 + k −1/Q 1[H+] and k obs = k 2 Q 2[H+]/(1 + Q 2[H+]), where k 1 and k 2 are the rate constants for the chelate-ring opening and the ligand liberation, respectively, k −1 is the rate constant of the chelate-ring closure, Q 1 and Q 2 are the protonation constants of the pyridine nitrogen and 5-carboxylate group in the one-end bonded intermediate, respectively. The results are discussed in terms of potential pharmaceutical application of the complex.

The ONN-complexes of dioxomolybdenum(VI) with dibasic 2-hydroxy-1-naphthaldehyde S-methyl/allyl-4-phenyl-thiosemicarbazones

Abstract: New dioxomolybdenum(VI) complexes were prepared by reacting S-methyl/allyl-4-phenyl-thiosemicarbazones of 2-hydroxy-1-naphthaldehyde (L 1 H2 and L 2 H2) and [MoO2(acac)2] in methyl, ethyl and propylalcohols. In the complexes the doubly deprotonated ligands are coordinated to molybdenum as tridentate ONN-donors through phenolic-oxygen, azomethine- and thioamide-nitrogen. The solid complexes of general formula [MoO2L(ROH)] which contain an alcohol (ROH) as second ligand were characterized by physico-chemical and spectroscopic methods. The fluorescence emission intensities of the compounds were recorded in chloroform, and the intensity changes were evaluated depending on chelation and time. The structure of the S-allyl-4-phenyl-thiosemicarbazone complex has been determined by the single crystal X-ray diffraction method.

Synthesis of water-soluble Mo(0) tetracarbonyl complexes containing nitrogen donor ligands and polymerization of methyl methacrylate

Abstract: Water-soluble Mo(0) tetracarbonyl complexes containing a α-diimine ligand have been prepared. All the complexes were characterized by elemental, LC-MS (APCI), FT-IR, 1H-NMR, and 13C-NMR spectroscopy. The pH dependent phase transfer of these complexes was investigated. This pH dependent phase transfer was accomplished over 10 times with no evidence of complex decomposition. Their catalytic activities on methyl methacrylate polymerization were determined.