Mixed Ligand Complexes of 5-arylazo-8-hydroxyquinoline and α-amino Acids with Co(II), Ni(II) and Cu(II)

Ten mixed ligand complexes of the type [M(X-QA)(aa)] and [Ni(X-QA)₂(Haa)(H₂O)],where X-HQA=5-arylazo-8-hydroxyquinoline derivatives, M=Co(II) orCu(II) and Haa=glycine (gly), alanine (ala) or methionine (met), have been prepared. The complexes have been characterized by elemental analysis, IR and electron spectra and thermal analysis. A tetrahedral structure has been proposed for the cobalt(II) and copper(II) complexes with bidentate coordination of amino acids. The nickel(II) complexes have been assigned an octahedral structure with the amino acids acting as monodentate ligands. The thermal behaviour of the complexes has been studied before and after γ-irradiation. This revised version was published online in August 2006 with corrections to the Cover Date.     

Infrared Spectroscopic and Gravimetric Studies on the Dicyclopentylaminemetal(II) Tetracyanonickellate(II) Host–Aromatic Guest Systems

The host complexes M(Cyclopentylamine)₂Ni(CN)₄ (M=Co or Cd) havebeen prepared in powder form. The spectral data suggest that the structures of thesecompounds are similar to those of the Hofmann-dma-type hosts. The absorptionand the liberation processes of the aromatic guests (benzene, toluene, 1,2-, 1,3-,1,4-dichlorobenzene, 1,4-dibromobenzene o-, m-, p-xylene, naphthalene)in these hosts have been examined at room temperature by gravimetric and spectroscopicmeasurements. The desorption of the benzene guest against time has been measured. Thehost structures do not change on inclusion and liberation of the guests. The host compoundshave been suggested as sorbents for isomeric separations.     

Molecular and Supramolecular Structures of a Nickel(II)–Copper(II)–Nickel(II) Trinuclear Complex Containing a New Macrocyclic Oxamido Complex Ligand

The title complex, [Cu(NiL)₂(H₂O)₂](ClO₄)₂, has been obtained by self-assembly, where [NiL] is a new macrocyclic oxamido complex ligand. In the crystal, a new kind of supramolecular interaction between the carbon atoms of the oxamido group of each [NiL] complex ligand in a [Cu(NiL)₂(H₂O)₂]^{2 +} cation and the oxygen atom of one of the ester carbonyls of another [Cu(NiL)₂(H₂O)₂]^{2 +} cation, and C—HO, O—HO and interactions are observed and link the trinuclear fragments and perchlorate ions to form a 3D supramolecular network.     

Mixed Ligand Complex Formation Reactions and Equilibrium Studies of Cu(II) with Bidentate Heterocyclic Alcohol (N,O) and Some Bio-Relevant Ligands

The formation equilibria of copper(II) complexes and the ternary complexes Cu(HMI)L (HMI=4-Hydroxymethyl-imidazole, L=amino acid, amides or DNA constituents) have been investigated. Ternary complexes are formed by a simultaneous mechanism. The results showed the formation of Cu(HMI)L and Cu(HMI,H₋₁)(L) complexes. The stability of ternary complexes was quantitatively compared with their corresponding binary complexes in terms of the parameters Δlog ₁₀ K and log ₁₀ X. The effect of the side chains of amino acid ligands (Δ_R) on complex formation was discussed. The concentration distributions of various species formed in solution were also evaluated as a function of pH. The thermodynamic parameters ΔH° and ΔS° calculated from the temperature dependence of the equilibrium constants are investigated. The effects of dioxane as a solvent, on the protonation constant of HMI and the formation constants of Cu^II–HMI complexes, were discussed.     

Synthesis and Structural Studies of Some β-Diketone Phenylhydrazones and their Complexes with Co(II), Ni(II), and Cu(II)

Summary.  New β-diketone phenylhydrazones prepared by condensation of substituted 3-arylidene-2,4-pentanediones with phenylhydrazine, have been characterized by their elemental analyses, IR, ¹H NMR, and mass spectra. Some complexes of these Schiff bases with Co(II), Ni(II), and Cu(II) ions have been synthesized; in addition to the above methods, their structures were studied by magnetic susceptibility and thermogravimetry measurements. Received January 26, 2000. Accepted (revised) April 14, 2000     

Heterospin Copper(II) Catecholate Complex with the TEMPO–Iminopyridine Ligand

Russian Journal of Coordination Chemistry - The heterospin copper(II) complex, ((pyridin-2-ylmethylene)-4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl)-3,6-di-tert-butylcatecholatocopper(II) (I), is...     

Electrochemical and Spectroscopic Studies on Interaction between Complex of Copper(Ⅱ) with Schiff Base Ligand and DNA

The crystal structure of ( [CuL (H2O) 2 ] (ClO4) 2 · 2H2O, CuL) (L ＝ N- (5-sulfosalicylidene)-4' -bromoaniline) was determined by means of X-ray crystallography. The interaction between CuL and salmon sperm DNA in a 0. 1 mol/L HOAc-NaOAc buffer solution (pH 5.10) was investigated by cyclic voltammetry and UV-Vis spectroscopy. A couple of redox peaks of CuL in the cyclic voltammograms(CV) can be seen at the glassy carbon electrode. It was found that the peak current of CuL decreased significantly with a negative shift of the peak potential in the presence of DNA compared with that in the absence of DNA. In addition,the decreased absorbance of CuL was observed with increasing the concentration of DNA; the absorption spectrum of an ethidium bromide(EB)-DNA system inthe presence of CuL confirms that the binding mode of CuL to DNA is different from the intercalation of EB with DNA. All the experimental results indicate that CuL can bind to DNA by electrostatic binding and form a 1:1 association complex with a binding constant of 2.72×104 L/mol.     

Experimental and Theoretical Study of the Stability of the Complex Fisetin–Cu(II) and A Comparative Study of Free Ligand and Complex Interaction with Molecular Singlet Oxygen

In this work, the flavonol fisetin was selected in order to study its reactivity against Cu(II), a metal ion of interest in biological media and industry. The stoichiometry and apparent formation constant of the complex in ethanolic medium at 25°C were evaluated using spectrophotometric techniques. The resulting stoichiometry was a 1:1 ligand:metal complex, and a log K = 5.17 ± 0.12 was determined. Since two possible chelation sites can be proposed for the complex formation, quantum chemistry calculations were performed on these structures. Calculations suggest that the hydroxyl-keto site is more stable for the complex formation than the catechol site. Flavonoids could exert protection against oxidative damage caused by reactive oxygen species, and this biological activity could be affected by chelation with metal ions. This led us to perform a study on the interaction of both, free flavonoid and complex, with reactive oxygen species. Our results showed both compounds quench molecular singlet oxygen photogenerated with visible light, mainly in a physical fashion. In order to analyze a possible protective effect of flavonoid and its complex against oxidative damage in biological environments, the amino acid tryptophan was selected as a model oxidation system. Free flavonoid does not have a marked protective effect, whereas its complex showed a relevant protective effect.     

Synthesis and Crystal Structure of Ni(Ⅱ) Complex with N-Salicylaldehyde-N''''-phenoxyacetylhydrazine Ligand

1INTRODUCTIONHydrazoneshavebeenattractingmuchatten-tionfromchemistsinrecentyearsbecauseoftheirbiologicalactivities,chemicalandindustrialversa-tility,andstrongtendencytochelatetotransitionmetals[1,2],lanthanidemetals[3]andmaingroupmetals[4,5].Inthehydrazonecomplexes,thehydra-zoneligandcanactasaneutralormononegativebidentateligand,orevenasadianionictridentateliganddependingonthedonoratomsoftheligandsandthereactionconditions.Ontheotherhand,variouscompoundsderivedfromphenoxyaceticacidareveryus…     

Studies on the Crystal Structure and Photoluminescence of a Mercury(Ⅱ)Complex Based on a Novel Pyridine Ligand

<正>A novel mercury(n)complex HgL_2Br_2 was prepared from HgBr_2 and the organic ligand 2-(N-methyl-N-(4-((E)-2-(pyridine-4-yl)vinyl)phenyl)amino)ethanol(L).The ligand was synthesized and then characterized by FT-IR spectroscopy,~1H NMR,mass spectrum and elemental analysis,while the single-crystal diffraction data of the complex were collected on a Siemens Smart CCD diffractometer.The complex crystallizes in triclinic space group P_1~-with a=5.367(5),b= 12.466(5),c=23.945(5)(?),α=90.812(5),β=96.318(4),γ=96.093(5)°,Z=2,D_c=1.817g·cm~(-3),μ=7.395 mm~(-1),S=0.825,and the final R=0.0396.The Hg(Ⅱ)ion in the distorted tetrahedral mercury(Ⅱ)complex C_(32)H_(36)HgBr_2N_4O_2 is coordinated by two N atoms from the two ligands together with two bromide ions.Solid-state emission of the ligand and its complex has been investigated at room temperature.     

Crystal Structure and Third-order Nonlinear Optical Property Studies on Copper(Ⅱ) Complex Containing NS Donor Ligand

Recently,thestudyofrelationshipsbetweenstructureandpropertyforseriesofcompoundhavingenhancedopticalnonlinearityhasincreaseourunderstandingofwhatmolecularleveIdesigncriteriaareimPortantformaximizingthesecondandthethird-ordernonlinearity'.lngeneral,thesestudieshavefocusedonmanipulationoftheeffectiveconjugationlengthforavarietyofn-electronbackbones,mostlyrelatedto.-PvariousorganiccomPoundscontainingdonorandacceptorgroups'.InthispaPer,wewillstudytheinteractionamongdonor-metal-donorinx-conjugation…     

Kinetic Studies on the Reaction of Sodium Hexa-cyanoferrate(II) Complex with Peroxydisulfate Anion

Introduction In the previous studies on the oxidation reaction,peroxydisulfate was widely used as an oxidizingagent.1-5 One of the advantages of this oxidant lies in itsstability in a wide range of pH values. The reaction be-tween Fe(CN)5L3- (L=N-aromatic heterocyclic li-gands) and S2O8 2- has been proved to proceed throughan outer-sphere electron transfer mechanism.5 For a re-action [(Eq. (1)] to be under an outer-sphere mechanismthe steps involved are the formation of a reactant …     

Complex Long-Range Magnetic Ordering Behaviors in Anisotropic Cobalt(II)–Azide Multilayer Systems

The crystal structures and magnetic properties of two new Co^II molecular magnets, [Co(N₃)₂(btzb)] ( 1 ) and [Co(N₃)₂(btze)₂] ( 2 ), are described and discussed (btzb=1,4-bis(tetrazol-1-yl)butane and btze=1,4-bis(tetrazol-1-yl)ethane). In the materials, (4,4) layers with μ-1,3-azide bridges are cross-linked by the monolayered btzb bridging ligands or spaced by bilayered btze terminal ligands to give a 3D ( 1 ) or 2D ( 2 ) coordination network with significantly different interlayer separations (10.6 vs. 15.2 Å). The observation that the layers in 1 and 2 are almost identical have not only allowed us to determine how the interlayer separation imposes its influences on their magnetic behavior, but also helps us understand the complex magnetic behavior of each structure. In the high-temperature range (>25 K), almost identical magnetic behaviors, typical of 2D antiferromagnetic systems, are observed for 1 and 2 . At low temperature they exhibit unusual and different behaviors that combine spin canting (weak ferromagnetism), metamagnetism, and stepped hysteresis. It has been found that the interlayer separation has little influence on the ordering temperature (23 vs. 22 K), but imposes very-strong influence on the metamagnetic critical field (6500 vs. 450 Oe), the coercivity (7500 vs. 650 Oe), and the hysteresis-step size. It may also play an adjusting role in determining the canting angle. Taking into account the strong anisotropy of the systems and the interlayer dipolar interactions, we have reasonably interpreted the unusual metamagnetic and hysteresis behaviors and the differences between 1 and 2 . In particularly, the stepped hysteresis loops have been explained by two weak ferromagnetic states.     

Synthesis, Crystal Structure and Thermal Stability of (Diacetylacetone)(diimidazole)Nickel(II) Complex

1 INTRODUCTION Acetylacetone is well known as the intermediate product of organic synthesis reaction, which can be used as annexing agent in gasoline, lubricant and desiccant in paint. Also it has been found to possess fungicidal and insecticidal activi…     

Synthesis and Crystal Structure of a Copper(II) Complex with 2,4-Dihydroxybenzylidene Benzoylhydrazone Ligand

1 INTRODUCTION The chemical properties of acylhydrazones Schiff bases and their complexes with some transition metal ions have been intensively investigated in several re- search areas because of their chelating capability and pharmacological applications[1～10]. Intriguingly, the copper(II) complexes are shown to be signifycantly more potent than the metal free chelate, suggesting that the metal complex is the biologically active species. Owing to the biological interest in these types …     

Crystal Structure of a Nickel(II) Complex with Asymmetric _L-Histidine Ligand

1 INTRODUCTION Metal-amino acid complexes are involved in the process of some important metal transport in humans. These complexes and their derivatives are important due to their biochemical and pharmacological pro- perties[1～5]. Nickel(II), as a Jahn-Teller center, when complexed with amino acids, adopts a variety of coordination geometries from distorted square plane, flattened tetrahedron and distorted square pyramid to distorted octahedron as observed in structures reported[6, 7], …     

Photo- and Electronically Switchable Spin-Crossover Iron(II) Metal–Organic Frameworks Based on a Tetrathiafulvalene Ligand

A major challenge is the development of multifunctional metal–organic frameworks (MOFs), wherein magnetic and electronic functionality can be controlled simultaneously. Herein, we rationally construct two 3D MOFs by introducing the redox active ligand tetra(4-pyridyl)tetrathiafulvalene (TTF(py)₄) and spin-crossover Fe^II centers. The materials exhibit redox activity, in addition to thermally and photo-induced spin crossover (SCO). A crystal-to-crystal transformation induced by I₂ doping has also been observed and the resulting intercalated structure determined. The conductivity could be significantly enhanced (up to 3 orders of magnitude) by modulating the electronic state of the framework via oxidative doping; SCO behavior was also modified and the photo-magnetic behavior was switched off. This work provides a new strategy to tune the spin state and conductivity of framework materials through guest-induced redox-state switching.