Salen and tetrahydrosalen nickel(II) and copper(II) complexes

The synthesis and characterisation of novel bis salen complexes, M(salenH2), N,N-bis-[5(1,1,3,3-tetramethyl- butyl)salicylidene]-1,2-diaminoethane complexes, (M=Ni or Cu), and the corresponding less studied, bis-tetrahydrosalen complexes, M[H2(salenH2)], N,N-bis-[2-hydroxy-5(1,1,3,3-tetramethylbutyl)benzyl]-1,2-diaminoethane complexes, (M=Ni or Cu), with a highly branched substitution pattern at C-5 of the benzene ring is described. The Schiff bases behave as dibasic tetradentate ligands. The tetrahydrosalen complexes show structural properties, chemical and thermal behaviour which is different from those of the corresponding salen complexes. The melting points and decomposition temperatures of these complexes were determined by d.s.c. and t.g.a.     

High-performance thin-layer chromatography of metal complexes ofmeso-tetrakis(p-tolyl)porphyrin on cellulose and silica gel

Summary The migration behavior of metal complexes ofmeso-tetrakis(p-tolyl)porphyrin (TTP) are studied in HPTLC systems with cellulose and silica gel thin-layers and various organic solvents of relatively low polarity. The mobility of the metal complex tends to increase in the following orders of its central-metal elements: on cellulose, Mg(II)<Zn(II)<V(IV)<(H)<Pd(II)< Ni(II)Cu(II); on silica gel, Mg(II)<V(IV)<Zn(II)= (H)<Ni(II)Pd(II)Cu(II). Recommendable phase system for the separation of metal-TTP complexes is a combination of silica gel thin-layer with a carbon disulfide-m-xylene mixture though the complexes of Ni, Cu and Pd are not completely resolved.     

Silicon-titanium xerogels: Synthesis and application to the determination of ascorbic acid and polyphenoles

Titanium and silicon-titanium xerogels have been obtained and it has been demonstrated that titanium(IV) incorporated into the xerogel matrix can participate in complexation reactions with ascorbic, gallic, ferulic, and caffeic acids and also rutin, quercetin, and dihydroquercetin present in aqueous solutions. In the case of dihydroquercetin 1 min of contact has been sufficient for achieving the equilibrium; the other compounds required 7–10 min. The stability constants of titanium(IV) complexes incorporated into xerogels reduced in the order dihydroquercetin > gallic acid > ascorbic acid > quercetin > caffeic acid > rutin. The procedures have been developed for solid-phase spectrophotometric determination of ascorbic, gallic, ferulic, caffeic acid as well as rutin, quercetin, and dihydroquercetin. The accuracy of the procedure has been examined by the standard addition method. The procedures for the determination of dihydroquercetin and ascorbic acid have been applied to the analysis of pharmaceutical preparations.     

Einfluß der Alkylgruppen auf die Struktureigenschaften der Cyanato-Kupfer(II)-Komplexe mit Alkylpyridinen

New cyanato-copper(II) complexes of the type Cu(NCO)₂ L ₂ (L=2,3-, 2,5-, 3,4- or 3,5-lutidine, 3- or 4-ethylpyridine) and Cu(NCO)₂ L (L=2,3- or 2,5-lutidine, 2-ethylpyridine) were prepared. Solid state electronic, ESR and IR spectral results show, that Cu(NCO)₂ L ₂ complexes have tetragonal structures varying from pseudooctahedral to practically planar forms, also involving a square-pyramidal arrangement. The -form of Cu(NCO)₂(2-picoline)₂ was isolated and found to be a distortion isomer of the known -form. According to physical results, Cu(NCO)₂ L complexes exhibit highly distorted five-coordinate structures. Further knowledge about the influence of type, number and position ofL ligand alkyl groups on the structure-bonding properties of cyanato-copper(II) complexes was obtained.

18. Mitt.:Valach, F., Dunaj-Juro, M., Handlovi, M., J. Cryst. Mol. Struct.10, 61 (1980).     

Solvent Sublation Using Dithizone as a Ligand for Determination of Trace Elements in Water Samples

Solvent sublation was studied as a method of separating and pre-concentrating traces of Zn(II), Cd(II) and Cu(II) as diphenylthiocarbazone (dithizone) complexes for their determination. The experimental conditions, such as pH of solution, amount of dithizone as ligand, stirring time, gas flow rate and flotation time, were optimized. Different non-ionic surfactants and types of organic solvents were optimized for efficient sublation. The analyte ions in a 350mL sample were complexed as metal-dithizone complexes by adding 10mL of 0.084% dithizone, 0.5mL of 0.1% nonylphenol polyoxyethylene ether (NP) and 10mL of pH 4.3 potassium hydrogen phthalate-sodium hydroxide buffer solution. The solution was stirred with a mechanical stirrer for 30min. It was transferred to a flotation cell, and the complexes were floated by bubbling air and extracted into 10mL of methylisobutyl ketone (MIBK) on the surface of the aqueous solution. The analytes in the organic phase were determined by flame atomic absorption spectrometry (F-AAS) for Zn(II) and by graphite furnace atomic absorption spectrometry (GF-AAS) for Cd(II) and Cu(II). The proposed method was applied to determine Zn(II), Cd(II) and Cu(II) in real water samples; the enrichment factor was more than 37, the RSD was less than 4.26%, recoveries ranged from 92.7 to 107.3%, and the detection limits were 1.0µgL^–1 for Zn(II), 0.006µgL^–1 for Cd(II) and 0.06µgL^–1 for Cu(II). The results obtained were satisfactory.     

Synthesis of 4-Dicyclohexylaminomethyl Antipyrine and Its Metal Complexes: Spectral Characterization and Evaluation of Thermodynamic Parameters

Complexes of Fe(III), Co(II), Ni(II), and Cu(II) with 4-dicyclohexylaminomethyl antipyrine (DCHAMA, L) were prepared and characterized by elemental and chemical analyses, IR, electronic absorption, ¹H NMR and EPR spectroscopies, thermal analysis, and magnetic susceptibility measurements. The stoichiometry of the complexes was found to be MLX₂, MLX₃, or MLX₂(H₂O)₂ where X = Cl or NO₃. The ligand exhibits a bidentate mode of coordination. Thermal analysis of the chloro complexes shows a three stage decomposition pattern for the Cu(II) complex and a two stage decomposition pattern for Fe(III) and Co(II) complexes to yield the respective metal oxides as the end product. Kinetic and thermodynamic parameters such as n, E _a, H ^#, S ^#, and G ^# were calculated using Coats–Redfern and Madhusudhanan–Krishnan–Ninan integral methods. The coordination number of the metal atom is found to influence the thermal stability of the complexes. The antimicrobial screening shows that the four-coordinated complexes are more active than the five- and six-coordinated ones and DCHAMA.     

Bivalent 3d-metal complexes of malonyl- and succinyldihydrazide based macrocyclic ligands. Synthesis and characterization

Summary The macrocycles 2,10-dimethyl-3,4,8,9,15-pentaazabicyclo-[9.3.1]-pentadeca-1 (15),2,9,11,13-penta-ene-5,7-dione (L) and 2,11-dimethyl-3,4,8,9,10,16-pentaazabicyclo[10.3.1]-hexadeca-1 (16),2,10,12,14-penta-ene-5,8-dione (L) were prepared and characterized by elemental, i.r. and mass spectral data. The macrocycles react with various metal(II) chlorides to yield complexes of the types [MLCl₂H₂O] (M = Mn, Co, Ni, Cu or Zn), [MLCl₂H₂O] (M = Mn, Ni, Cu or Zn) and [Co₃L₂Cl₄]Cl₂. The complexes were characterized by physico-chemical and spectroscopic methods.     

Complexes of Some Metal Nitrates with 4′-Nitrobenzo-15-Crown-5

Complexes of Ag, Cu, Ca, Nd, and Er nitrates with 4-nitrobenzo-15-crown-5 (NB15C5) were synthesized and their IR absorption spectra were studied. Macrocyclic conformation in the complexes was determined. The structures of the complexes were proposed with account of the data of IR absorption spectra and of the previous X-ray diffraction study. In the Ag, Cu, and Ca complexes, NB15C5 was found in the inner sphere, while in the Nd and Er complexes, it was found to be the outer-sphere ligand.     

Application of EXAFS and XANES Methods in Coordination Chemistry of Carbohydrates and Their Derivatives

A summary is presented of the results obtained on metal complexes of carbohydrates (aldoses, ketoses and mono-, di- and polysaccharides) and their derivatives (aldonic and alduronic acids, polyalcohols, amino sugars, and amino acid sugar adducts). The structural parameters (coordination number, bond distance, and Debye–Waller factor) measured by extended X-ray absorption fine structure (EXAFS) spectroscopy obtained earlier on transition metals [Cu(II), Fe(III), Ni(II), Zn(II), Co(II), Ag(I), Mn in different oxidation states and organotin(IV)] complexes are discussed. In addition we report here the preparation of Bu₂Sn(IV)²⁺ complexes of rutin {3-[6-O-(6-deoxy--L-mannopyranosyl)-(-D-glucopyranosyl)oxy]-2-(3,4-dihydroxyphenyl)-5,7-dihydroxy-4H-1-benzopyran-4-one} and quercetin (containing {O,O} donor atoms) in ligand to metal ratios of 1:1 and 1:2. The analytical data revealed the formation of well-defined complexes. The local structures of the complexes were determined by an EXAFS method. It was found that the Sn–O bond distances in the first coordination sphere are closed the values found in Et₂Sn(IV) complexes with nonprotected carbohydrates.     

Synthesis,characterization and biological analysis of transition metal complexes with macro cyclic ligands derived from adipic acid,ethylenediamine with diethyloxalate and diethylmalonate

Macro-cyclic ligands from adipic acid, ethylenediamine with diethyloxalate and diethylmalonate and their respective metal complexes of Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) with macro cyclic ligands (LO) and (LM) L [N,N′-bis(2-aminoethyl)hexanediamide] were synthesized successfully. These metal complexes were characterized by Fourier transform infrared, ultraviolet visible spectrometry, proton nuclear magnetic resonance spectroscopy, and mass Spectrometry, CHNS and thermogravimetric analysis. The elemental analysis confirms the structures for Mn(II), Co(II) and Ni(II) complexes similar to octahedral geometry, Cu(II) complexes as a square planar geometry and Zn(II) complexes in the tetrahedral geometry. The molar conductivities of all the metal complexes were taken in 10^?3 M DMSO, and values of all the metal complexes showed their electrolytic nature which indicates the presence of chloride ions. Thermal analysis supports as the metal complexes are thermally stable. The result of antimicrobial activity against various microorganisms confirms that the metal complexes are potent bactericides and fungicides than the ligand. Metal complexes of LO with Cu(II) and Zn(II) were found to be highly active against S. typhimurium than the complexes of LM.

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Steric effect on construction of Cu(II) complexes with pyridine carboxamide ligands

The structures of three new Cu(II) complexes with pyridine carboxamide ligands (Me₂bpb, 6-Me₂-Mebpb, and 6-Me₂-Me₂bpb) have been determined. 6-Methyl-substituted pyridyl bpb ligands produced dimeric compounds with Cu(II) ions, and weak interactions between dimers can make even polymeric compounds, while bpb ligands without 6-methyl substitution produced monomeric Cu(II) complexes. The large distortion effects of 6-methyl-substitution are shown in Cu(II) complexes with 6-methyl-substituted pyridyl bpb ligands. This result suggests that the steric effect of 6-methyl-substitution plays important role for distortion of the structure, and 6-methyl-substitution can also influence to make polymeric compounds with interactions between Cu(II) ions and neighbor carbonyl oxygen atoms. In addition, the voltammetric behaviors of the Cu complexes were examined and classified into two groups, with/without 6-methyl group. The complexes without 6-methyl group show reversible redox waves at −1.6 V, and the complexes with 6-methyl group do irreversible redox ones at −1.3 V, indicating that the presence of the methyl group of 6-position of the complex makes the reduction of the complexes easier.     

Thermal properties of cyanatocopper(II) complexes with pyridine,bipyridine and phenanthroline

The thermal properties of cyanatocopper complexes with pyridine, bipyridine and phenanthroline are described in this paper. It was found that the thermal stabilities of the complexes were found to increase in the order pybipy2(NCS)₂ (L=pyridine and its methyl derivates) which are composed of the liberation of ligandsL and redox reactions of thiocyanate ligands with the central Cu(II) atom [1, 2]. The decomposition temperature of thiocyanate ligands depends on the properties of the ligandsL present in the coordination sphere. An analogous course of thermal decomposition was also observed for [Cu(bipy)₂(NCX)](NCX) (X=S or Se) [3]. For the phenanthroline complexes [Cu(phen)₂(NCX)₂] (X=S or Se) the thermal stability was found to increase significantly (by about 140C) and the decomposition stoichiometry was also changed [3].The present paper contains the results of thermoanalytical studies on bipyridine and phenanthroline cyanatocopper complexes, and a comparison of the thermal properties of pyridine cyanato and isothiocyanatocopper complexes.     

Fast Atom Bombardment Mass Spectroscopic Investigation of Inclusion Complexes of Cyclodextrins with 4-Nitrophenol and Benzoic Acid

Mixtures of -, -, and -cyclodextrins and 4-nitrophenol (or benzoic acid) were investigated by means of fast atom bombardment mass spectroscopy. In the gas phase, inclusion complexes of -, , and -cyclodextrins with 4-nitrophenolate and benzoate, which have a 1 : 1 cyclodextrin–guest stoichiometry, were observed in negative-ion mode. In addition, guest anions, clusters of two and three guest molecules, and guest–matrix complexes were observed.     

Radiation decomposition of metal acetyl acetonates

Studies on the thermal decomposition of the acetyl acetonate complexes of transitional metal ions Cu/II/, Cr/III/, Mn/II/, Co/II/, Fe/III/, Vo/II/, Zn/II/, and Cd/II/ have been performed by thermogravimetric method. Taking the initial decomposition temperature as a measure of thermal stability, the relative order of the thermal stability of these complexes shows the following order: Zn/II/<Cd/II/< VO/II/<Fe/III/<Cr/III/<Cu/II/Co/II/< Mn/II/. The nature of decomposition of Cu/II/ and Cr/III/ complexes is similar, a sigmoid curve exists. In other cases a long linear decomposition follows the sigmoid pattern. The linear decomposition is a function of final decomposition temperature and percentage of decomposition. The kinetics of the decomposition is analyzed according to the Coats-Redfern equation. The results are discussed on the basis of structural and other aspects leading to the decomposition.     

Antioxidant effects of dihydroquercetin and rutin in peroxidase reactions catalyzed by cytochrome <Emphasis Type="Italic">c</Emphasis>

The combination of cytochrome c (Cyt c) and cardiolipin is known to catalyze free radical oxidation of membrane lipids, thereby triggering the cascade of reactions that lead to programmed cell death (apoptosis). It was interesting to estimate the possibility of controlling this reaction with the use of inhibitors of free radical reactions (antioxidants). The effects of bovine heart cardiolipin (BCL) and synthetic 1,1′,2,2′-tetraoleyl cardiolipin (TOCL) on the Cyt c peroxidase activity detected by luminol-enhanced chemiluminescence (CL) were studied. The CL amplitude substantially increased in the presence of TOCL and BCL in the ranges of the cardiolipin to Cyt c molar ratios from 0 to 30 and from 0 to 50, respectively, and insignificantly increased upon further increase in these ratios to 640: 1 and 320: 1. This dependence of the CL amplitude on the cardiolipin to protein ratio may have been accounted for by saturation of the protein surface with cardiolipin molecules reached at a certain molar ratio. The effects of the antioxidants rutin and dihydroquercetin (DHQ) on the peroxidase activity of Cyt c in combination with BCL was studied in the presence of the CL activator coumarine C-525 at a BCL to Cyt c molar ratio of 32: 1. In both cases, the peroxidase activity decreased as the antioxidant content of the system increased. A 50% inhibition of the reaction was observed at DHQ and rutin concentrations of 10 and 3 μM, respectively. It is supposed that the use of antioxidants will make it possible to control the formation of lipid radicals on membrane-bound Cyt c, which is the key stage of apoptosis.     

Studies on methylatedβ-cyclodextrins and C60 inclusion complexes

Solid, water-soluble inclusion complexes: DMCD/C₆₀ (1:1) and DMCD/C₆₀ (2:1) can be obtained by kneading. Their formation has been confirmed by UV-vis spectroscopy, X-ray diffraction and DSC studies. UV-vis studies also reveal the transformation between the two complexes in aqueous solution. TMCD has also been studied as the host of an inclusion complex with C₆₀.     

Binary and Ternary Complexes Between Lauryl Hexaoxyethylene, Benzoate and Cyclodextrin. Part I. α-CD

The characterization of binary and ternary complexes of benzoate, lauryl hexaoxyethylene (C₁₂E₆) and -CD is presented. Complexation was characterized by capillary zone electrophoresis and titration microcalorimetry. These techniques suggested that -CD formed two qualitatively different complexes with C₁₂E₆. The stoichiometric ratio of -CD : C₁₂E₆ in the individual complexes was 1 : 1 and 1.4 : 1, with stability constants of2.0 × 10³ M^-1 and 6.4 × 10⁵ M^-1.4, respectively. At higher concentrations of interacting species (10 mM), a precipitate formed. Addition of benzoate seemed to prevent precipitate formation and appeared to increase the stability constants of both binary complexes. Both techniques also indicated formation of ternary complexes between -CD, C₁₂E₆ and benzoate.     

Octahedral and tetrahedral configuration changes of nickel(II) chloro complexes from spectrophotometric studies in aprotic solvents

Four NiII chloro complexes were identified spectrophotometrically in aprotic media such as DMSO, DMF and propylene carbonate for the first time. An original multiwavelength numerical treatment, based on a Marquardt method, results in the determination of the individual electronic spectra of the mononuclear chloro complexes and of their stability constants, the values of which indicate the presence of rather weak complexes in DMSO and DMF, much stronger in the less solvating propylene carbonate solvent. The overall stability constants calculated for the NiII chloro complexes are: 1=52, 2=140, 3=160, 4=210 in DMSO, 1=60, 2=110, 3=900, 4=15000 in DMF, 1=1.6×109, 2=6.4×1015, 3=2.7×1021, 4= 5.1×1026 in PC.The solvent effect is discussed in terms of the quantitative results obtained from this spectrophotometric study and reveals that the stability of the complexes is an inverse function of the donor properties of the solvent. This result illustrates the general behavior of complex formation in dipolar aprotic solvents, i.e. the substitution of one solvent molecule in the inner coordination sphere by the ligand is easier if the solvation strength of the solvent is lower. The solvent effect is also described in terms of the variation of shifts of the calculated absorption maxima for the individual electronic spectra of the chloro complexes. This result is used to identify clearly at which step of coordination the octahedral configuration of the nickel ion changes to the tetrahedral configuration, by comparison with the well-known structural properties of these complexes in the solid state.