Metal chelates with some cellulose derivatives. Part I. Preparation and characterization of chromium (III)–carboxymethyl cellulose complexes

A systematic spectrophotometric study on the complexation of chromium (III) ion with sodium carboxymethyl cellulose (CMC) was carried out. The effects of the degree of substitution (DS) of the polymer, the concentrations of Cr(III) and CMC solutions, the pH and temperature on the complex formation were studied in the aqueous state. CMC complexes with Cr(III) were characterized by elemental analysis, magnetic moment and spectral (Vis and IR) data. The results showed that CMC (L) chelated to the metal ion according to the formula CrL₂ · 2H₂O. The ligand field parameters, namely D_q, B and β were calculated; the β-values indicate strong covalency in the ligand σ bond. The IR spectra revealed that the chelating sites of CMC are not only the carboxymethyl groups, via the ether- and the carboxyl-oxygen atoms, but also the secondary hydroxyl groups.     

Some Semiconductor Properties of Carboxymethyl Cellulose-Copper Complexes

Metal chelates of three grades of carboxymethyl cellulose (CMC) (LI-L3) with Cu(II) ions, either originating from CuCl₂ or CuSO₄, were prepared and characterized by elemental analysis, infrared spectra, and electrical conductivity studies. The results showed that the degree of substitution of CMCs and the origin of the Cu(II) ion have a profound effect on the amount of metal included in the polymer complexes and the structure and the electrical conductivity of the prepared complexes. CMC acts as a uninegatively charged bidentate ligand when it is chelated with Cu(II) of CuCl₂ via the carboxymethyl group and exhibits the formula Cu(L)₂, whereas it acts as a binegatively charged bitentate ligand when it is chelated with CuSO₄ via the carboxymethyl and secondary hydroxyl groups and exhibits the formula CuL.2H₂O. The investigation revealed that the electrical conductivity depends on the temperature and has two maximum peaks. The values of the activation energy for the conductivity of CMC and their complexes indicated that the samples changed from a low-semiconductor to a high-semiconductor property with heating. It is found that CMC-Cu(II) complexes formed from CuSO₄ exhibit a high-semiconductor property compared to complexes derived from CuCl₂.     

Polymer Complexes. XLIII. EPR, Spectra, and Stereochemical Versatility of Novel Copper(II)Polymer Complexes

Copper(II) polymer complexes of empirical formula [Cu(ligand)₂X₂] (where X = Cl, Br, I, NO₃, and SO₄) and [Cu(ligand)(CH₃COO)₂] have been prepared with poly(3-phenylacrylidine semicarbazone). All the polymer complexes prepared have been characterized by elemental analysis, magnetic moment, conductance, IR, electronic, ¹H-NMR, and electronic paramagnetic resonance spectral studies. The polymer complexes [Cu(ligand)₂X₂] and [Cu(ligand) (CH₃COO)₂] may have tetragonal symmetry while the [Cu(ligand)₂( SO₄)₂] may be five-coordinate trigonal bipyramidal in structure. All complexes exhibit normal magnetic moments corresponding to one unpaired electron except [Cu(ligand)(CH₃COO)₂] which shows a subnormal magnetic moment. EPR spectra of the polymer complexes have been studied with a view to assigning their stereochemistries. Various EPR parameters have been calculated. The g, A, G values for all the polymer complexes are consistent with a tetragonal 1–5 and trigonal bipyramidal 6 stereochemistry in the Cu(II) polymer complexes of homopolymer.     

Metal Chelates with Some Cellulose Derivatives: V. Synthesis and Characterization of Some Iron(III) Complexes with Cellulose Ethers

Two types of monoligand complexes of FeCl₃, Fe(NO₃)₃ and Fe₂(SO₄)₃ with hydroxyethyl cellulose (HEC) and carboxymethyl cellulose (CMC) were prepared and characterized. Elemental analysis, UV and IR spectro-scopies, conductance and magnetic measurements were used to assign the mode of coordination in the isolated species. The investigation revealed that Fe(III ) exhibits tetrahedral coordination with HEC and CMC. These ligands act as a bidentate chelating agent via the two oxygen atoms of the vicinal hydroxyl and ether groups (ethoxyl or carboxymethyl groups). The prepared complexes have the formula [(HEC) FeCl]Cl, [(HEC) FeNO₃]NO₃, [(HEC)FeSO₄·H₂O]H₂O, [(CMC)FeCl·H₂O]Cl·2H₂O, [(CMC)Fe·2NO₃]3H₂O and [(CMC)-FeSO₄·H₂O]H₂O. The results also showed that the type of cellulose ether (functional group) and the anion of the metal salts used have an effect on the conductivity, structure and absorptivity of Fe(III ) complexes. © of SCI.     

Novel Coumarin-Thiadiazole Hybrids and Their Cu(II) and Zn(II) Complexes as Potential Antimicrobial Agents and Acetylcholinesterase Inhibitors

A series of coumarin-thiadiazole hybrids and their corresponding Cu(II) and Zn(II) complexes were synthesized and characterized with the use of spectroscopic techniques. The results obtained indicate that all the coumarin-thiadiazole hybrids act as bidentate chelators of Cu(II) and Zn(II) ions. The complexes isolated differ in their ligand:metal ratio depending on the central metal. In most cases, the Zn(II) complexes are characteristic of a 1:1 ligand:metal ratio, while in the Cu(II) complexes the ligand:metal ratio is 2:1. All compounds were tested as potential antibacterial agents against Gram-positive (Staphylococcus aureus, Staphylococcus epidermidis) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa) bacterial strains demonstrating activities notably lower than commercially available antibiotics. The more promising results were obtained from the assessment of antineurodegenerative potency as all compounds showed moderate acetylcholinesterase (AChE) inhibition activity     

Metal Chelates with Some Cellulose Derivatives. II. Preparation and Characterization of Co(II)-CMC Complexes

Complexes of three grades of sodium carboxymethyl cellulose (CMC) with cobalt(II) chloride have been prepared and characterized by elemental analysis, magnetic measurements, and infrared (IR) and electronic spectroscopy. The studies revealed that CMCs react with cobalt(II) in the stoichiometric ratio 1:1 (metal ion:ligand). The ligand field parameters of the octahedral Co(II) complexes were calculated. The stability of these complexes was studied in DMF medium using spectrophotometric methods. The optimum conditions favoring complex formation are critically evaluated.     

Interaction of microcrystalline chitosan with Ni(II) and Mn(II) ions in aqueous solution

The protonation constant of the NH₂ function was determined by the method of Katchalsky and Spitnik and by the SUPERQUAD fitting procedure. Samples with higher concentrations of chitosan indicated aggregations of polymer chains, which led to a loss in the effective concentration of the ligand (L). It followed, as a result of potentiometric titrations, that an excess of L of microcrystalline chitosan (MCCh) with a deacetylation degree of 0.90 was a complexing agent toward the metal (M), which was Ni(II) or Mn(II). Species ML and ML₂ were accepted by SUPERQUAD for both of the M's, where coordination occurred via the amino nitrogen. For Ni(II), however, the hydroxyl oxygen may also have been an electron‐pair donor at lower excesses of MCCh and, by that, made possible the formation of five‐membered chelate rings in the hydroxyl deprotonated MLH_‐1 species. The evaluated formation constants were compared with the values known until now for monomeric D ‐glucosamine. Additional confirmation of the M–L interaction was determined by the spectrophotometric titration of a Ni(II)–MCCh solution. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2572–2577, 2005     

Cationic Peptides and Their Cu(II) and Ni(II) Complexes: Coordination and Biological Characteristics

Antimicrobial peptides are a promising group of compounds used for the treatment of infections. In some cases, metal ions are essential to activate these molecules. Examples of metalloantibiotics are, for instance, bleomycin and dermcidin. This study is focused on three new pseudopeptides with potential biological activity. The coordination behavior of all ligands with Cu(II) and Ni(II) ions has been examined. Various analytical methods such as potentiometric titration, UV-Vis and CD spectroscopies, and mass spectrometry were used. All compounds are convenient chelators for metal ion-binding. Two of the ligands tested have histidine residues. Surprisingly, imidazole nitrogen is not involved in the coordination of the metal ion. The N-terminal amino group, Dab side chains, and amide nitrogen atoms of the peptide bonds coordinated Cu(II) and Ni(II) in all the complexes formed. The cytotoxicity of three pseudopeptides and their complexes was evaluated. Moreover, their other model allowed for assessing the attenuation of LPS-induced cytotoxicity and anti-inflammatory activities were also evaluated, the results of which revealed to be very promising.     

Synthesis,crystal structures and biological activities of 2-acetylpyridine N(4)-cyclohexylthiosemicarbazone and its manganese(II) and nickel(II) complexes

2-Acetylpyridine N(4)-cyclohexylthiosemicarbazone (HL) and its manganese(II) and nickel(II) complexes formulated as [Mn(L)₂] (1) and [Ni(L)₂] (2) have been synthesized and characterized by elemental analysis, infrared spectra, mass spectra, and single-crystal X-ray diffraction studies. In the two complexes, the coordination polyhedron approaches an octahedron, where the two ligands coordinate to the metal via the pyridine nitrogen atom and the nitrogen and sulfur donors of the thiosemicarbazide moiety. Biological studies, carried out in vitro against selected bacteria and K562 leukaemia cell line, respectively, have shown that the free ligand and its complexes exhibited distinct differences in the biological activities.     

Polystyrene anchored vanillin Schiff base—Complexation and ion removal studies

A set of six new polystyrene anchored metal complexes have been synthesized by the reaction of the metal salt with the polystyrene anchored Schiff base of vanillin. These complexes were characterized by elemental analyses, Fourier transform infrared spectroscopy, diffuse reflectance studies, thermal studies, and magnetic susceptibility measurements. The elemental analyses suggest a metal : ligand ratio of 1 : 2. The ligand is unidentate and coordinates through the azomethine nitrogen. The Mn(II), Fe(III), Co(II), Ni(II), and Cu(II) complexes are all paramagnetic while Zn(II) is diamagnetic. The Cu(II) complex is assigned a square planar structure, while Zn(II) is assigned a tetrahedral structure and Mn(II), Fe(III), Co(II), and Ni(II) are all assigned octahedral geometry. The thermal analyses were done on the ligand and its complexes to reveal their stability. Further, the application of the Schiff base as a chelating resin in ion removal studies was investigated. The polystyrene anchored Schiff base gave 96% efficiency in the removal of Ni(II) from a 20‐ppm solution in 15 min, without any interference from ions such as Mn(II), Co(II), Fe(III), Cu(II), Zn(II), U(VI), Na⁺, K⁺, NH₄⁺, Ca²⁺, Cl^?, Br^?, NO₃^?, NO₂^?,and CH₃CO₂^?. The major advantage is that the removal is achieved without altering the pH. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1536–1539, 2005     

Potentiometric Studies on Ternary Complex Formation between Cu(II), Ni(II), Zn(II), Cd(II), nitrilotriacetic acid and amino acid

The formation of ternary complexes of the type MAB (where M = Cu(II), Ni(II), Zn(II) or Cd(II); A = nitrilotriacetic acid and B = glycine, α-alanine or dl-aspartic acid) has been shown by potentiometric studies. The nature of titration curves indicates that the secondary ligand B is added stepwise to the initially formed metal nitrilotriacetates. The formation constants (log K_MAB) and the free energies of formation (ΔF°) of the mixed complexes have been calculated at 25 ± 1 °C and m̈ = 0.10 (KNO₃) at different pH values. The formation constants of the resulting 1:1:1 ternary complexes follow the order Cu(II) > Ni(II) > Zn(II) > Cd(II).     

Synthesis and Catalytic Activities of Silica-Supported Multifunctional Azo-Containing Schiff Base Complexes with Cu(II), Co(II), Ni(II) and Mn(II)

A novel 4-((5-formyl-2,4-dihydroxyphenyl)diazenyl)benzylphosphonic acid (FPABP) ligand was synthesized and bound to silica-gel which was activated with 3-aminopropyltriethoxysilane (APTES). Cu(II), Co(II), Ni(II) and Mn(II) complexes of silica-supported ligand (FDPDABP) were synthesized. The ligand and its complexes were characterized by using NMR, FT-IR, elemental analysis, ICP-OES and scanning electron Microscope (SEM). Catalytic properties of the complexes were investigated for the selective oxidation of cyclohexane under microwave power. SiO₂-FDPDABP-Cu(II) complex showed good catalytic activitiy for the selective oxidation of cyclohexane to cyclohexanol with 35.61% yield and cyclohexanone with 7.74% yield.     

Liquid-Phase Catalytic Hydroxylation of Phenol Using Cu(II), Ni(II) and Zn(II) Complexes of Amidate Ligand Encapsulated in Zeolite-Y as Catalysts

Copper(II), nickel(II) and zinc(II) complexes of amidate ligand 1,2-bis(2-hydroxybenzamido)ethane(H₂hybe) encapsulated in the super cages of zeolite-Y have been prepared and characterized by spectroscopic studies and thermal as well as X-ray diffraction (XRD) patterns. These complexes catalyze the liquid-phase hydroxylation of phenol with H₂O₂ to catechol as a major product and hydroquinone as a minor product. Considering the concentration of substrate and oxidant, amount of catalyst, temperature of the reaction and volume of solvent, a best-suited reaction condition has been optimized to get maximum hydroxylation. Under the optimized reaction conditions, [Cu(hybe)]-Y has shown the highest conversion of 40% after 6h, which is followed by [Ni(hybe)]-Y with 37% conversion and [Zn(hybe)]-Y has shown the poorest performance with 33% conversion. All these catalysts are more selective towards catechol formation (90%), irrespective of their catalytic performance.     

Electrophoretic studies of mixed ligand complexes in solution—copper(II), nickel(II), cobalt(II), uranyl(II) and thorium(IV)—tartarate—nitrilotriacetate

Paper electrophoresis has been used for the study of the equilibria in mixed ligand complex systems in solution. The method is based on the migration of a spot of a metal ion, with the complexants added in the background electrolyte (0.1 M perchloric acid), at a fixed pH. The concentration of one of the complexants [A] is kept constant, while that of second ligand [L] is varied. A graph of—log [L] against mobility is used to obtain information on the formation of the mixed ligand complex, and to calculate the stability constant. Using this technique, the values of overall stability constant of the complex metal—tartarate—nitrilotriacetate have been found to be 10^12.25, 10^5.98, 10^?3.56, and 10^3.74 for Cu(II), Ni(II), Co(II), UO₂(II) and Th(IV) complexes, respectively at μ = 0.1 and temp. = 40°C.     

Synthesis and properties of chelate polymers of Cu(II), Ni(II), Co(II), Mn(II) and Zn(II) with a schiff's base of 5,5′-methylene-bis(3,3′-dinitrosalicylaldehyde) with 1,6-hexanediamine

The synthesis, characterization and coordination aspects of the title polymer ligands are reported. The polymeric chelates were prepared by polycondensations of transition metal ions (M) with a poly(Schiff's base) (L). The analytical data propose a (ML)_n formula for the chelates. All the polychelates are stable and insoluble in common organic solvents. The geometry around the central metal ion in each chelate is proposed on the basis of measurements of magnetic susceptibilities and UV reflectance spectra. The ligand field splitting parameters 10 Dq, the interelectronic repulsion parameter B, the nephelauxetric parameter β and ligand field splitting energies (L.F.S.E.) have been calculated for Ni(II) and Co(II) chelates. All chelates are resistant to moderately concentrated acids and dilute alkalies at ambient temperature. They exhibit thermal stabilities to varying degrees. IR spectra show that the ligand usually coordinates via the carbonyl oxygen (C=O) and the phenolic OH with replacement of hydrogen by metal ions.     

Synthesis and characterization of monomeric and polymeric Cu(II) complexes of 3,4-ethylenedioxythiophene-functionalized with cyclam ligand

A functionalized EDOT derivative with 1,4,8,11-tetraazacyclotetradecane (cyclam) ligand pendant to the ethylene bridge (4) and its complexes [M(4)(BF₄)₂], where M(II) = Cu(II), was prepared and characterized. Their electrochemical copolymerization with EDOT was studied. The electro-co-polymerized films were characterized by electrochemical methods, X-ray photoelectron spectroscopy and by X-ray fluorescence spectroscopy. The co-polymerization method was found to afford a good control of the metal concentration in the polymer matrix and represents a good technique for preparing electronically conductive polymers containing redox-active metal complexes.     

Square-planar nickel(II) complexes with a tridentate Schiff base and monodentate heterocycles: self-assembly to dimeric and one-dimensional array via hydrogen bonding

Two nickel(II) complexes having the general formula [Ni(bhac)L] with tridentate ONO-donor acetylacetone benzoylhydrazone (H₂bhac) and monodentate N-donor heterocycles (L=3,5-dimethylpyrazole (Hdmpz) and imidazole (Himdz)) are reported. The complexes were synthesized in ethanol media by reacting Ni(O₂CCH₃)₂·4H₂O, H₂bhac and L in 1:1:1 mole ratio and characterized by analytical, magnetic and spectroscopic methods. X-ray crystal structures of both complexes have been determined. In each complex, the metal ion is in square-planar N₂O₂ coordination geometry. In the solid state, a one-dimensional assembly of the [Ni(bhac)(Himdz)] molecules is formed via intermolecular hydrogen bonds between the imidazole N–H groups and the uncoordinated N-atoms of the deprotonated amide functionalities. On the other hand, two [Ni(bhac)(Hdmpz)] molecules are involved in a pair of complementary hydrogen bonds between the pyrazole N–H groups and the coordinated O-atoms of the deprotonated amide functionalities forming a dinuclear species.     

Bis[4-(methylthio)phenylmethyleneaminophenyl] disulfide, 2-[4-(methylthio)phenyl]-2,3-dihydro-1,3-benzothiazole,and its nickel(II) and cobalt(II) complexes: Synthesis,adsorption on gold surface and electrochemical characterization

2-[4-(Methylthio)phenyl]-2,3-dihydro-1,3-benzothiazole (1) and bis[4-(methylthio)phenylmethylene-aminophenyl] disulfide (2) were synthesized. Novel coordination compounds of Ni(II) and Co(II) with 2-[4-(methylthio)phenylmethyleneamino]thiophenol, M(1)₂ (M=Co (3); M=Ni (4)), were prepared by reacting 1 with M(OAc)₂·6H₂O or MCl₂·6H₂O in EtOH solution. The structure of 2 was proved by X-ray crystallography. Electrochemical behavior of 1–4 in CH₃CN solution and at the surface of a gold electrode was studied by cyclic voltammetry. The modification of the electrode by ligand 1 and its complexes with Ni²⁺ and Co²⁺ is described in detail. Two procedures were used to obtain a self-assembled monolayer of a metal complex on the gold surface: the adsorption of prepared coordination compound 3 or 4 on the electrode and the initial modification of the electrode with ligand 1 followed by the formation of a coordination complex between the ligand adsorbed on the electrode and a metal salt occurring in solution. On the basis of the electrochemical data, it was found that the structure of complexes formed on the surface differs from that of the complexes produced in solution.     

Thin‐Layer Chromatography of Cu(II), Co(II) and Ni(II)

Abstract

The chromatographic behavior of some heavy metals on thin layer of silica gel was studied. The effect of polarity of mixed developing agent systems on the R_f values of metal complexes was investigated. The linear dependence between the R_f values and the polarity of developing agents was deduced and a series of good separations of Cu(II),Co(II) and Ni(II) were obtained successfully. This method was applied to separate Cu(II) and Ni(II) in a real sample.     

Crystal structures of palladium(II) and copper(II) complexes of meso-phenyl tripyrrinone

Meso-phenyl tripyrrinone (2), which is derived directly from N-confused porphyrin by Cu(II)-assisted oxygenolysis, can serve as a metal coordination ligand using three nitrogens and one oxygen in the core. The crystal structures of Pd(II) and Cu(II) complexes show the similar square-planar N₃O-coordination but the mode of oligomeric chains formed in the crystals by π–π stacking interaction is different: zig–zag for Cu(II) and straight for Pd(II) complex.