Versatile chelating behavior of benzil bis(thiosemicarbazone) in zinc, cadmium, and nickel complexes

Reactions of benzil bis(thiosemicarbazone), LH(6), with M(NO(3))(2).nH(2)O (M = Zn, Cd, and Ni), in the presence of LiOH.H(2)O, show the versatile behavior of this molecule. The structure of the ligand, with the thiosemicarbazone moieties on opposite sides of the carbon backbone, changes to form complexes by acting as a chelating molecule. Complexes of these metal ions with empirical formula [MLH(4)] were obtained, although they show different molecular structures depending on their coordinating preferences. The zinc complex is the first example of a crystalline coordination polymer in which a bis(thiosemicarbazone) acts as bridging ligand, through a nitrogen atom, giving a 1D polymeric structure. The coordination sphere is formed by the imine nitrogen and sulfur atoms, and the remaining position, in a square-based pyramid, is occupied by an amine group of another ligand. The cadmium derivative shows the same geometry around the metal ion but consists of a dinuclear structure with sulfur atoms acting as a bridge between the metal ions. However, in the nickel complex LH(6) acts as a N(2)S(2) ligand yielding a planar structure for the nickel atom. The ligand and its complexes have been characterized by X-ray crystallography, microanalysis, mass spectrometry, IR, (1)H, and (13)C NMR spectroscopies and for the cadmium complex by (113)Cd NMR in solution and in the solid state.     

Mononuclear and polynuclear chelates of picolinoyldithiocarbazate

Mononuclear and polynuclear chelates of potassium picolinoyldithiocarbazate (KHPcDC) with Mn(II), Fe(ll1), Fe(II), Co(Il), Ni(II), Cu(II), Zn(II), Cd(II), Hg(II), Pd(II) and U(VI)O2 have been prepared and characterized by chemical and thermal (TG, DTG, DTA) analyses, molar conductivities, spectral (UV-Visible, IR, NMR, ESR) and magnetic moment measurements. The molar conductivities of the complexes lie in the non-electrolyte range whilst KHPcDC is a 1:1 electrolyte. Changes in selected vibrational absorption of the ligand upon coordination indicate that KHPcDC behaves as monoanionic and coordinates in a bidentate, tridentate and/or bridging tetradentate manner. Trans-form structure is proposed for [Pd(HPcDC)2] x 2H20 and [Cd(HPcDC)2] complexes on the basis of NMR data. An octahedral structure is proposed for Fe(III), Fe(II) and Ni(II) complexes, a square-planar structure for Co(II) and Pd(II) complexes and a tetragonally distorted octahedral structure for the Cu(II) chelate on the basis of spectroscopic and magnetic data. The ligand field parameters (B, Dq, beta) for the Fe(III) and Ni(II) chelates were calculated. TG, DTG and DTA studies support the different modes of chelation of KHPcDC. The solid metal acetate chelates have a unique decomposition exotherm profile which can be used as a rapid and sensitive tool for the detection of acetate-containing complexes.     

Synthesis and magnetic,spectral and thermal eukaryotic DNA studies of some 2-acetylpyridine- [N-(3-hydroxy-2-naphthoyl)] hydrazone complexes

Complexes of Ni(II), Co(II), Cu(II), Zn(II), Cd(II), Hg(II) and U(VI)O₂ with 2-acetylpyridine-[N-(3-hydroxy-2-naphthoyl)] hydrazone (H₂APHNH) have been prepared and characterized by elemental analysis, molar conductance, thermal (TG, DTG), spectral (¹H NMR, IR, UV–Vis, ESR) and magnetic measurements. ¹H NMR spectrum of the ligand suggests the presence of intramolecular hydrogen bonding. IR spectra show that H₂APHNH is a bidentate, tridentate and/or tetradentate ligand. Thermal decomposition of some complexes ended with metal oxide as a final product. ESR spectra gave evidence for the proposed structure and the bonding for some Cu(II) complexes. Biological activity measurements were carried out.     

Metal-catalysed oxidation processes in thiosemicarbazones: new complexes with the ligand N-{2-([4-N-ethylthiosemicarbazone]methyl)phenyl}-p-toluenesulfonamide

The coordination behaviour of a new thiosemicarbazone Schiff-base building block, N-{2-([4-N-ethylthiosemicarbazone]methyl)phenyl}-p-toluenesulfonamide, H2L1 (1), incorporating a bulky tosyl group, towards Mn II, Fe II, Co II, Ni II, Cu II, Zn II, Cd II, Ag I, Sn II, and Pb II has been investigated by means of an electrochemical preparative procedure. Most metal complexes of L1 have the general formula [M(L1)]2.nX (M=Mn, Fe, Co, Ni, Cu, Cd, Pb; n=0-4, X=H2O or CH3CN), as confirmed by the structure of [Pb(L1)]2 (15), in which the lone pair on lead is stereochemically active. This lead(II) complex shows an intense fluorescence emission with a quantum yield of 0.13. In the case of silver, the complex formed was found to possess a stoichiometry of [Ag2(L1)]2.3H2O. During reactions with manganese and copper metals, interesting catalysed processes have been found to take place, with remarkable consequences regarding the ligand skeleton structure. In synthesising the manganese complex, we obtained an unexpected dithiolate thiosemicarbazone tosyl ligand, H2L2, as a side-product, which has been fully characterised, including by X-ray diffraction analysis. In the case of copper, the solid complex has the formula [CuL1]2, but the crystallised product shows the copper atoms coordinated to a new cyclised thiosemicarbazone ligand, H2L3, as in the structures of the complexes [Cu(L3)]2.CH3CN (8) and [Cu(L3)(H2O)]2.CH3CN.H2O (9). The zinc complex [Zn(L1)]4 (12) displays a particular tetranuclear zeolite-type structure capable of hosting small molecules or ions, presumably through hydrogen bonding.     

Syntheses, electronic structures, and EPR/UV-vis-NIR spectroelectrochemistry of nickel(II), copper(II), and zinc(II) complexes with a tetradentate ligand based on S-methylisothiosemicarbazide

Template condensation of 3,5-di-tert-butyl-2-hydroxybenzaldehyde S-methylisothiosemicarbazone with pentane-2,4-dione and triethyl orthoformate at elevated temperatures resulted in metal complexes of the type M(II)L, where M = Ni and Cu and H(2)L = a novel tetradentate ligand. These complexes are relevant to the active site of the copper enzymes galactose oxidase and glyoxal oxidase. Demetalation of Ni(II)L with gaseous hydrogen chloride in chloroform afforded the metal-free ligand H(2)L. Then by the reaction of H(2)L with Zn(CH(3)COO)(2)·2H(2)O in a 1:1 molar ratio in 1:2 chloroform/methanol, the complex Zn(II)L(CH(3)OH) was prepared. The three metal complexes and the prepared ligand were characterized by spectroscopic methods (IR, UV-vis, and NMR spectroscopy), X-ray crystallography, and DFT calculations. Electrochemically generated one-electron oxidized metal complexes [NiL](+), [CuL](+), and [ZnL(CH(3)OH)](+) and the metal-free ligand cation radical [H(2)L](+?) were studied by EPR/UV-vis-NIR and DFT calculations. These studies demonstrated the interaction between the metal ion and the phenoxyl radical.     

Spectral,Thermal, and Antimicrobial Studies on the Copper(II), Zinc(II), Cadmium(II), and Mercury(II) Chelates of a New Antimetabolite–5-Dimethylaminomethyl-2-Thiouracil

Owing to the presence of multiple donor atoms such as N(1)H, C(2)SH, N(3), C(4)O, and CNC in the newly synthesized antimetabolite, namely, 5-dimethylaminomethyl-2-thiouracil, preferences of the hetero-atoms for coordination with metal ions like Cu(II), Zn(II), Cd(II), and Hg(II) were explored. The complexes isolated were characterized by chemical analysis and spectroscopic techniques. The ligand behaves as a bidentate/tetradentate chelating ligand. Invariably in all the complexes, one of the donor atoms is the soft C(2)SH. The kinetic and thermodynamic parameters for the thermal decomposition of the metal chelates were evaluated using (Coats–Redfern) and (Madhusudanan–Krishnan–Ninan) equations. The antimicrobial studies show that the copper(II) complexes are more active than the other complexes.     

Structural and spectral studies of copper(II) and nickel(II) complexes of pyruvaldehyde mixed bis{N(4)-substituted thiosemicarbazones}

Pyruvaldehyde mixed bis(thiosemicarbazones) have been prepared in which the two thiosemicarbazone moieties have different N(4)-substituents. The mixed bis(thiosemicarbazones) and their copper(II) and nickel(II) complexes have been characterized with IR, electronic, mass, ¹H NMR (Ni) and EPR (Cu) spectra. Representative crystal structures have been solved of nickel(II) complexes with either a pyruvaldehyde mixed bis(thiosemicarbazone) or a bis(thiosemicarbazone) with identical N(4)-substituents acting as a tetradentate ligand. [Ni(Pu4M4DE)] has an N(4)-methylthiosemicarbazone substituent on the keto “arm” and N(4)-diethylthiosemicarbazone substituent on the aldehyde arm. [Ni(Pu4M)] contains two N(4)-methylthiosemicarbazone moieties. Both bis(thiosemicarbazones) form square-planar N₂S₂ complexes with nickel(II) and copper(II).     

Complexes of 3d(n) metal ions with thiosemicarbazones: synthesis and antimicrobial activity

The chelating behavior of the thiosemicarbazone derivatives of 2-hydroxy-8-R-tricyclo[7.3.1.0.(2,7)]tridecane-13-one (where R = H, CH3, C6H5) towards Co(II), Ni(II) and Cu(II) has been investigated by elemental analysis, molar conductivity measurements, UV-VIS, IR, ESR spectroscopy and thermal studies. It was deduced from the experiments performed that the ligands coordinate to metal ions in different ways--neutral bidentate or mononegative bidentate--depending on the nature of R. Also, if metal acetates are used instead of metal chlorides, the ligands coordinate in a mononegative bidentate fashion, regardless of the nature of R or the thiosemicarbazone type ligand. The antimicrobial activity of the ligands and of the complexes towards samples of Acinetobacter boumanii, Klebsiella pneumoniae, Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa was determined.     

Synthesis, spectral characterization, solution equilibria, in vitro antibacterial and cytotoxic activities of Cu(II), Ni(II), Mn(II), Co(II) and Zn(II) complexes with Schiff base derived from 5-bromosalicylaldehyde and 2-aminomethylthiophene

Schiff base namely 2-aminomethylthiophenyl-4-bromosalicylaldehyde (ATS)(4-bromo-2-(thiophen-2-yl-imino)methylphenol) and its metal complexes have been synthesized and characterized by elemental analyses, IR, 1H NMR, solid reflectance, magnetic moment, molar conductance, mass spectra, ESR and thermal analysis (TGA). The analytical data of the complexes show the formation of 1:2 [M:L] ratio of the formula [ML2], where M represents Ni(II), Zn(II) and Cu(II) ions, while L represents the deprotonated Schiff base. IR spectra show that ATS is coordinated to the metal ions in a bidentate manner through azomethine-N and phenolic-oxygen groups. The ligand and their metal chelates have been screened for their antimicrobial activities using the disc diffusion method against the selected bacteria. A cytotoxicity of the compounds against colon (HCT116) and larynx (HEP2) cancer cells have been studied. Protonation constants of (ATS) ligand and stability constants of its Cu2+, Co2+, Mn2+, Zn2+ and Ni2+ complexes were determined by potentiometric titration method in 50% (v/v) DMSO-water solution at ionic strength of 0.1 M NaNO3.     

Synthesis and genotoxicity of Schiff base transition metal complexes

A new ONNO‐type azomethine ligand, 2,2′‐(ethane‐1,2‐diylidenedinitrilo)dibenzoic acid, (YLH₂) ( 1 ) has been prepared by the condensation of 2‐aminobenzoic acid and glyoxal. The coordination compounds [Ni(YL)] ( 2 ), [Co(YL)] ( 3 ), [Cu(YL)(H₂O)] ( 4 ), [Zn(YL)] ( 5 ), and [Cd(YL)] ( 6 ) of the YLH₂ ligand with five transition metal ions, Ni(II) Co(II), Cu(II), Zn(II), and Cd(II) have been prepared. The structures of these new azomethine compounds are proposed on the basis of the elemental analyses, proton nuclear magnetic resonance, infrared, ultraviolet–visible spectroscopy, and X‐ray powder diffraction patterns. Elemental analyses indicate a ligand metal ratio of 1:1 in the coordination compounds. X‐ray powder diffraction parameters for [Cu(YL)(H₂O)] and [Cd(YL)] compounds correspond to orthorhombic and monoclinic structures, respectively. The ligand acts as a tetradentate ligand bending through oxygen atoms of the hydroxyl groups of benzoic acid and nitrogen atoms of the azomethine groups. In addition, the ligand and its metal complexes have been studied for their possible genotoxic potential. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:119–130, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20665     

Synthesis and spectroscopic studies of CoII, NiII, FeIII and ThIV complexes derived from 2,2'-dihydroxy-3,3'-di(carboxymethyl)-1,1'-binaphthyl

The synthesis of 2,2'-dihydroxy-3,3'-di(carboxymethyl)-1,1'-binaphthyl (H2L) and its novel metal complexes with Co(II), Ni(II), Fe(III) and Th(IV) salts are reported. The ligand and its metal complexes have been characterized on the basis of analytical, conductance, spectral (IR, UV-vis, 1H NMR, mass) and magnetic susceptibility measurements. The M?ssbauer spectrum of the Fe(III) complex indicates a low-spin octahedral geometry around the Fe(III) ion. The IR and 1H NMR spectral data show that the ligand behaves in a dibasic bidentate fashion coordinating to two metal atoms through the two deprotonated naphthyl OH groups and acts in a dibasic tetradentate manner using both carbonyl oxygen's and the deprotonated naphthyl OH groups coordinating to two metal ions. Thermal studies (TGA, DTA) confirm the presence of solvents either inside or outside the coordination sphere and support the mechanism of the decomposition process. The value of [alpha]D20 for the ligand has been determined in DMSO.     

Synthesis and studies on metal coordination with a novel carboxyamide ligand

Novel complexes of Co(II), Ni(II), Cu(II) and Pd(II) with the new ligand [N,N'-bis(2-carboxy-1-oxo-phenelenyl)ethylenediamine] (H2L) have been synthesized and characterized on the basis of elemental analyses, magnetic susceptibility, thermal, infrared, electronic, 1H NMR and EPR spectral studies. Infrared and 1H NMR spectra show that H2L acts as a binegative tetradentate ligand. Coordination occurs through deprotonated carboxylate oxygens and nondeprotonated amido nitrogens in all the complexes. Electronic spectral studies and magnetic moment values suggest N2O2 coordination around each metal centre with strong field square planar chromophores. The probable structures of the complexes have been assigned on the basis of spectral studies. The complex formation between M(II) [M(II) = Mn(II), Co(II), Ni(II), Cu(II) and Zn(II)] and (L2-) has also been studied potentiometrically in 75% aqueous DMF at 25 degrees C in 0.1 M NaClO4. The stability constants were found to follow the order: Mn(II) < Co(II) < Ni(II) < Cu(II) > Zn(II).     

Metal Complexes of Saccharin with the N-(2-hydroxyethyl)-ethylenediamine Ligand: Synthesis,Characterization and Spectroscopic Examination. Crystal Structures of trans- Bis(Saccharinato)Bis{N-(2-hydroxyethyl)-Ethylenediamine} copper(II) and Cadmium(II)

The novel transition metal saccharinato complexes of N-(2-hydroxyethyl)-ethylendiamine (HydEt-en) have been synthesized and characterized by elemental analyses, magnetic moments, UV-Vis and IR spectra. Coordination behaviour of HydEt-en has been studied. The Mn(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) form mononuclear complexes, while the Fe(II) and Co(II) complexes are dimeric. The crystal structures of the [Cu(sac)₂(HydEt-en)₂] and [Cd(sac)₂(HydEt-en)₂] complexes, where sac is the deprotonated form of saccharin, were determined by x-ray diffraction. The metal ions are octahedrally coordinated by these ligands. The amine ligand acts as a bidentate N-donor ligand and its ethanol group is not involved in coordination. The sac ions coordinate through the deprotonated N as a monodentate ligand. The NH and OH groups of the amine ligand are involved in intra- and intermolecular hydrogen bonding with the carbonyl and sulphonyl oxygens of the sac ions to form a three-dimensional infinite network.     

Spectral,thermal and magnetic investigations of Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) 4-methylphthalates

Conditions for the preparation of Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) 4-methylphthalates were investigated and their composition, solubility in water at 295 K and magnetic moments were determined. IR spectra and powder diffraction patterns of the complexes prepared with molar ratio of metal to organic ligand of 1.0:1.0 and general formula: M [ CH₃C₆H₃(CO₂)₂]·nH₂o (n=1-3) were recorded and their decomposition in air were studied. During heating the hydrated complexes are dehydrated in one (Mn, Co, Ni, Zn, Cd) or two steps (Cu) and next the anhydrous complexes decompose to oxides directly (Cu, Zn), with intermediate formation of carbonates (Mn, Cd), oxocarbonates (Ni) or carbonate and free metal (Co). The carboxylate groups in the complexes studied are mono- and bidentate (Co, Ni), bidentate chelating and bridging (Zn) or bidentate chelating (Mn, Cu, Cd). The magnetic moments for paramagnetic complexes of Mn(II), Co(II), Ni(II) and Cu(II) attain values 5.92, 5.05, 3.36 and 1.96 M.B., respectively. This revised version was published online in July 2006 with corrections to the Cover Date.     

Transition metal complexes of a Schiff base: synthesis,characterization, and antibacterial studies

Synthesis of a new Schiff base derived from 2-hydroxy-5-methylacetophenone and glycine and its coordination with compounds Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and UO₂(VI) are described. The ligand and complexes have been characterized on the basis of analytical, electrical conductance, infrared, ESR and electronic spectra, magnetic susceptibility measurements, and thermogravimetric analysis. The ligand is a dibasic tridentate (ONO) donor in all the complexes except Zn(II), where it is a monobasic bidentate (OO) donor. The solid state DC electrical conductivity of ligand and its complexes have been measured over 313–398 K, and the complexes were semiconducting. Antibacterial activities of ligand and its metal complexes have been determined by screening the compounds against various Gram (+) and Gram (?) bacterial strains.     

Bis(diamino-diamido)-tetrathiafulvalene, a redox active sensor for proton, anions, and cations

A bis(diamino-diamido) tetrathiafulvalene (TTF) derivative H(4)L(2) has been designed and synthesized. Experiments of pH titration reveal that integrating the redox active TTF unit with the diamino-diamido moiety adds new properties to the traditional ligand. Oxidation of the TTF moiety increases the acidity of the amido group, and the coordination of metal ions is also sensitive to the oxidation state of the ligand. This compound is capable of acting as a leaving or accepting ligand for proton and metal ions. The electrochemistry of the protonated TTF derivative of H(4)L(2) was studied in the presence of a series of oxo anions and metal cations. The results indicate that the redox potentials selectively respond to HC(2)O(4)(-) and SO(4)(2-) anions, and Ni(II) and Cu(II) cations. Solid-state structures of a cation-anion salt H(8)L(2)·2SO(4)·8H(2)O and a nickel coordination compound [Ni(2)L(2)]·2DMF have been characterized by means of X-ray crystallography which are helpful in understanding the inter-ion interactions.     

EPR, mass, electronic, IR spectroscopic and thermal studies of bimetallic copper(II) complexes with tetradentate ligand, 1,4-diformyl piperazine bis(carbohydrazone)

The synthesis of novel bimetallic Cu(II) complexes with general stoichiometry [Cu(2)(H(2)L)X(2)(H(2)O)(2)], [Cu(2)(H(2)L)(CH(3)COO)(2)] and [Cu(2)(H(2)L)SO(4)(H(2)O)(2)] (where H(2)L=dideprotonated ligand and X=NO(3)(-) and Cl(-)) derived from tetradentate ligand obtained by the condensation of 1,4-diformyl piperazine with carbohydrazide has been discussed. The complexes were characterized by elemental analyses, molar conductance measurements, magnetic susceptibility measurements, IR, mass, UV, EPR spectral studies and thermogravimetric analyses. The value of magnetic moments indicates that the complexes are paramagnetic and show the antiferromagnetic interaction between the two metal centres. The complexes possess the square planar coordination environment. The values of covalency measurements, i.e., in-plane sigma-bonding alpha(2), in-plane pi-bonding beta(2) and orbital reduction factor k indicate the covalent nature of complexes.     

Crystal structure of (1,10-phenanthroline-N,N')(1,4,7,10-tetraazacyclododecane-N,N',N",N"')nickel(II) diperchlorate.

The crystal structure of the title compound, [Ni(C8H20N4)(C12H8N2)](ClO4)2, has been determined by X-ray diffraction. The Ni(II) ion is six coordinated with four nitrogen atoms of the tetradentate macrocyclic ligand and two nitrogen atoms of the bidentate ligand in a distorted octahedron geometry. The folded tetradentate macrocyclic ligand adopts a configuration having four five-membered chelate rings in distorted eclipsed conformations. The four hydrogen atoms of the amine groups of the macrocyclic ligand are on the same side towards the bidentate ligand.     

Spectral, thermal, electrochemical and analytical studies on Cd(II) and Hg(II) thiosemicarbazone complexes

The coordination characteristic of the investigated thiosemicarbazones towards hazard pollutants, Cd(II) and Hg(II), becomes the first goal. Their complexes have been studied by microanalysis, thermal, electrochemical and spectral (electronic, IR and MS) studies. The substitutent (salicylaldehyde, acetophenone, benzophenone, o-hydroxy-p-methoxybenzophenone or diacetylmonoxime) plays an important role in the complex formation. The coordination sites were the S for thiosemicarbazide (HTS); NN for benzophenone thiosemicarbazone (HBTS); NS for acetophenone thiosemicarbazone (HATS) and salicylaldehyde thiosemicarbazone (H(2)STS); NNS or NSO for diacetylmonoxime thiosemicarbazone (H(2)DMTS). The stability constants of Hg(II) complexes were higher than Cd(II). The kinetic and thermodynamic parameters for the different thermal decomposition steps in the complexes have been evaluated. The activation energy values of the first step ordered the complexes as: [Cd(H(2)STS)Cl(2)]H(2)O>[Cd(H(2)DAMTS)Cl(2)]>[Cd(HBTS)(2)Cl(2)]2H(2)O>[Cd(HATS)(2)Cl(2)]. The CV of [Cd(H(2)STS)Cl(2)]H(2)O and [Hg(HBTS)Cl(2)] were recorded. The use of H(2)DMTS as a new reagent for the separation and determination of Cd(II) ions from water and some synthetic samples using flotation technique is aimed to be discussed.     

Stereochemistry,structural and models of novel 5-(4'-derivatives phenyldiazo)-3-phenyl-2-thioxo-4-thiazolidinone complexes

Copper(II) and cadmium(II) complexes of 5-(4'-derivatives phenyldiazo)-3-phenyl-2-thioxo-4-thiazolidinone (HLn) were prepared, their compositions and physicochemical properties were characterized by elemental analysis, magnetic suseptibility measurements, and infrared, electronic spectra. The novel complexes have the stoichiometric formulae [Cu(HLn)(OAc)n(H2O)(X)] (OAc = acetate, X = H2O or acetate) and [Cd(L)(OAc)(H2O)], respectively. Elemental analysis and IR spectra denote, that two types of complexes with different octahedral and tetrahedral structure for Cu(II) and Cd(II) ions. I.R. spectra show that the ligand is monobasic/neutral bidentate forming thereby a six-membered chelating ring and concomitant formation of an intramolecular hydrogen bond. The stoichiometeries of these complexes were determined conductometrically and indicated the formation of 1:1 and 1:2 (metal:ligand) complexes.