Fluorescence study of an immobilized ligand—metal ion complex

A ligand known to form a fluorescent complex with aluminum ion was immobilized on silica gel. The immobilization sequence was verified by cross-polarization magicangle spinning n.m.r. spectroscopy and diffuse reflectance u.v. spectroscopy. The solid-state fluorescence of the immobilized ligand complexed with aluminum ion was similar to the fluorescence of a solvated complex of a model ligand. The potential to eliminate possible interfering species by isolating the complex from solution was demonstrated.     

Preparation of a copper ion complex of sterically congested diphenyldiazomethanes having a pyridine ligand and characterization of their photoproducts

To show that persistent high-spin polycarbenes can be realized by utilizing hetero spin systems, two diphenyldiazomethanes having pyridyl groups, i.e., bis{4-(4-pyridyl)-2,6-dimethylphenyl}diazomethane (4,4'-DPy-1-N(2)) and {2,4-di(4-pyridyl)-6-bromophenyl}(2,6-dimethyl-4-tert-butylphenyl)diazomethane (2,4-DPy-1-N(2)), were prepared. Triplet carbenes, 4,4'-DPy-1 and 2,4-DPy-1, generated by photolysis of the corresponding diazomethanes were characterized by spectroscopic means (ESR and UV/vis in matrix at low temperatures and laser flash photolysis in solution at room temperature). The results showed that they were fairly persistent. Magnetic properties of the photoproducts from a 1:1 complex between DPy-1-N(2) and Cu(hfac)(2) (hfac = hexafluoroacetylacetonate) were characterized by ESR and a superconducting quantum interference device (SQUID) magneto/susceptometer. The field dependences of magnetization for the complexes, expressed by using M versus H/T plots, were analyzed in terms of the Brillouin function to be S = 6.80 (F = 0.60) for the 1:1 complex of 4,4'-DPy-1 and Cu(hfac)(2) and S = 3.71 (F = 0.73) for the 1:1 complex of 2,4-DPy-1 and Cu(hfac)(2) at 2.0 K. Thus, it has been demonstrated that a high-spin species is actually generated in the photoproducts and that the complexed carbenes showed significant stability.     

Synthesis of an asymmetrical tripodal tetraamine ligand and its five-coordinate copper(II) complex

A simple synthesis has been devised for the tripodal 3,3,4-tetraamine ligand N{(CH2)3NH2}2{(CH2)4NH2} (L). This ligand forms a copper(II) complex, [Cu (LH)Cl2]ClO4 (7), the structure of which has been determined by X-ray diffraction. The cation contains a five-coordinate copper atom, bonded to two chloride ions, the two propylamine groups and the tertiary nitrogen atom of the ligand; the arrangement is a distorted trigonal bipyramid, in which the two primary amine groups occupy the axial positions. The butylamine group of the ligand does not coordinate to copper but is protonated. It is involved in hydrogen bonding to the perchlorate ion. The e.p.r. spectrum of [Cu(dpt)Cl2] is very similar to that of (7), suggesting that it also has a trigonal bipyramidal structure. This revised version was published online in June 2006 with corrections to the Cover Date.     

Synthesis and spectral characteristics of the combined ligand copper complex with proline and corazole

Synthesis of the combined ligand complex of copper(II) prolinate bis(1,5-pentamethylenetetrazole) [Cu(PMT)₂](Pro)₂ was carried out. The product is interesting as a biologically active compound. It is obtained by reaction of copper carbonate with proline followed by further reaction with corazole. The composition and structure of the complex were confirmed by elemental analysis and data of UV, IR, and ¹H NMR spectroscopy. The complex was characterized in detail by the method of circular optical dichroism.     

X-Ray and EPR study on copper (II) complexes with an enamine ligand

The enamine (HEAID) obtained from aniline and 2-acetyl-1,3-indandione (2AID) behaves as a bidentate ligand in coordination with copper (II) ion. Two types of crystals, apparently different in shape, were isolated and studied by single-crystal X-ray diffraction. The X-ray data for the brown rhombic crystals of compound 1 shows a mononuclear complex of Cu(II) coordinated with two EAID-anions, Cu(EAID)₂. The X-ray data for the green crystals of compound 2 shows a dinuclear Cu(II) complex with two OH⁻ groups acting as bridging ligands, [Cu₂(μ-OH)₂(EAID)₂]. In both cases the ligand coordinates after deprotonation of the amine group.     

A gadolinium(III) complex with 8-amidequinoline based ligand as copper(II) ion responsive contrast agent

A new Cu(2+)-responsive MRI contrast agent (Gd-QDOTAMA) with a quinoline-based ligand was synthesized and characterized. Relaxivity studies on Gd-QDOTAMA showed that the relaxivity increased from 4.27 mM(-1) s(-1) to 7.29 mM(-1) s(-1) in response to equimolar amounts of copper(II) ion, corresponding to ca. 71% relaxivity enhancement. Distinct changes in relaxivity were undetected upon addition of physiologically relevant alkali metal cations (K(+) or Na(+)), alkaline earth metal cations (Mg(2+) or Ca(2+)), or d-block metal cations (Zn(2+), Cu(+), Fe(2+), Fe(3+)), indicating a high selectivity for Cu(2+) over other biologically relevant metal ions. Moreover, the influence of common biological anions at physiological levels on the Cu(2+)-responsive contrast agent was also studied. Luminescence studies on the Eu counterpart Eu-QDOTAMA suggest that the enhancement in relaxivity for Gd-QDOTAMA in response to Cu(2+) is most likely due to the increased number of inner-sphere water molecules around Gd(3+) upon Cu(2+) binding to the 8-amidequinoline moiety. In vitro T(1)-weighted phantom images of Gd-QDOTAMA confirmed that signal intensity was markedly increased by the addition of equimolar amounts of Cu(2+).     

Synthesis,crystal structure and antimicrobial properties of a copper(II) complex of an unsymmetrical tripodal ligand

A new copper(II) complex of an unsymmetrical tripodal ligand (NN₂O222) derived from tris(2-aminoethylamine)amine (tren) by substitution of one aminoethyl group by an hydroxyethyl group has been synthesized and characterized by X-ray crystallographic methods as [(NN₂O222)Cu(ImH)](ClO₄)₂·0.5H₂O (NN₂O222?=?2-[bis(2-aminoethyl)amino]ethanol; ImH?=?imidazole). Crystals of the complex are orthorhombic, space group Pna2₁, with a?=?29.983(10), b?=?15.568(5), c?=?8.127(3)?Å. Two similar monometallic cations exist in the asymmetric unit and in each case the Cu(II) ion is five-coordinate with tetragonally distorted trigonal bipyramidal geometry. Variable-temperature magnetic measurements show that there is very weak antiferromagnetic interaction between the metal ions. Cyclic voltammetry indicates quasi-reversible Cu^II/Cu^I redox behavior at +44?mV vs SCE. An antimicrobial activity study found that the complex is active against Candida albican, Staphylococcus aureus, Bacillus pumilus, Klebosiella pneumoniae and Escherichia coli, but to no greater extent than Cu(ClO₄)₂·6H₂O.     

Synthesis and the crystal structures of a monoanionic tetrafluorodentate ligand and its complex with lanthanum ion

New organotitanium fluorides [Hdmpy]⁺[(C₅Me₄R)₂Ti₂F₇]⁻ (R=Me 4, Et 5, dmpy=2,6-dimethylpyridine, lutidine) have been prepared from (C₅Me₄R)TiF₃ and 2,6-dimethylpyridine·(HF)₂. The compounds 4 and 5 react with La(CF₃SO₃)₃ to give [La{(C₅Me₄R)₂Ti₂F₇}₃] (R=Me 6, Et 7) containing the [(C₅Me₄R)₂Ti₂F₇]⁻ anion as a tetrafluorodentate ligand in the crystal structures of 4 and 7. The cation–anion pair is connected by a hydrogen bond in 4 and the all-fluorine environment of 12 fluorine atoms coordinated to a lanthanum ion is found in 7.     

Anionic copper complex fragmentations from enkephalins under low-energy collision-induced dissociation in an ion trap mass spectrometer

Peptide metallation with Cu2+ was explored in the negative ESI mode using an ion trap mass spectrometer. Under these conditions, the [(M-3H) + CuII]- species formed were investigated under low-energy collision-induced dissociation conditions. MS2 experiments indicate a very different behavior of CuII metallated complexes compared with [M-H]- species. CuII induces an easy loss of CO2 and specific side-chain cleavages (by radical losses) at the C-terminal residue, as observed previously by prompt 'in source' dissociation experiments. The loss of CO2 yields an unstable carbylide that leads to further dissociations involving the migration of a proton or a hydrogen radical (through the reduction of CuII). Multistage MS3 experiments were carried out to rationalize this behavior. Fragmentation pathways are proposed in order to explain the product ions observed. The side-chain radical loss at the C-terminus was demonstrated to be a consecutive process. Finally, evidence is provided that the specific side-chain cleavages can be used for the differentiation of Leu/Ile and Gln/Lys residues when they are located at the C-terminus. The existence of a zwitterionic form in the case of the anionic YGGFK-CuII complex is proposed.     

Kinetics and mechanisms of the catalytic reactions of formaldehyde with copper oxides and a copper ion complex in aqueous alkali

The kinetics of the autocatalytic reactions of formaldehyde with copper(II) and copper(I) oxides and with the Cu²⁺ ion of the copper EDTA complex, as well as formaldehyde disproportionation in the presence of copper metal, have been investigated in aqueous solutions of sodium hydroxide. Two likely reaction mechanisms are presented. The difference between these mechanisms does not alter the observed kinetics of the processes, whose rate is determined by their first, slow step, namely, the oxidation of the methylene glycol anion adsorbed on the copper surface into formic acid. In the slow step of the first mechanism, a hydride ion is abstracted from the methylene glycol anion and is transferred to copper. In the slow step of the second mechanism, the methylene glycol anion undergoes anodic oxidation, releasing a hydrogen atom and an electron. In the rapid steps of the first mechanism, the hydride ion undergoes anodic oxidation to hydrogen, the copper compound undergoes cathodic reduction to copper metal, and, simultaneously, the electron and hydrogen are transferred to a nonionized formaldehyde molecule to yield methanol. Mathematical models are suggested for the reactions. The effective rate constants and activation energies of the slow steps of the reactions have been determined. The effective rate constants of the noncatalytic reduction reactions of the copper compounds and the ratios of the rates of the rapid hydrogen and methanol formation reactions have been estimated.     

丝光沸石骨架中Fe的XAFS表征

通过水热法合成了骨架含铁的杂原子丝光沸石,采用XRD,FT-IR及TPR等表征技术确认铁进入了分子筛骨架。利用XAFS地分子筛中铁的精细结构和配位环境进行了表征和计算,近边吸收的Fe-K边前跃迁证实铁在分子筛骨架中位于四面体配位环境中,与邻近原子存在共价键作用;铁-氧配位键长为0.188～0.189nm.     

X-ray diffraction study of copper(II) hexafluoroacetylacetonato-benzoylacetonate,Cu(HFA-BA), a mixed ligand complex

Conclusions An x-ray diffraction method was used to study polycrystalline samples and monocrystals of cupric hexafluoroacetylacetonato-benzoylacetonate. The molecular packing may be described as dimers arranged along the b-axis. The Cu-Cu distance in the dimer is 3.2 Å and the distance between the dimers is 5.8 Å.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1405–1406, June, 1989.     

High-energy complex copper(II) perchlorate with 1,5-pentamethylenetetrasole as ligand

Possibility of obtaining an energy-saturated metal complex, copper tetrakis[cyclopentamethylenetetrasol] perchlorate, was studied by reacting copper(II) perchlorate hexahydrate with cyclopentamethylenetetrazol. The composition and structure of the complex were confirmed by elemental analysis and UV, IR, ¹H NMR, and ESR spectroscopies. The thermal decomposition of the metal complex synthesized was analyzed and its explosive characteristics and combustion law, as well as the combustion law of a model formulation of a composite solid propellant with addition of the complex, were determined.     

A study on dismutation mechanism of superoxide ion by a macrocyclic copper(II) complex of dioxotetraamine

The mechanism of catalytic dismutation of superoxide anion by copper(II) complex of 12-(4′-nitro)-benzyl-1,4,7,10-tetraazacyclotridecane-11,13-dione was studied by using pulse radiolysis and cyclic voltammetry. The redox potential of Cu(II)/Cu(III) was obtained to be E⁰=0.590 V (SCE) in solution of 0.5 mol·dm⁻³ Na₂SO₄. The rate constant of catalytic dismutation was determined to be k_cat=1.9×10⁶ (pH=7.0) and 1.1×10⁶ mol·dm³·s⁻¹ (pH=7.8) by pulse radiolysis and it was suggested that mechanism of catalytic dismutation of O₂⁻ is alternate oxidation and reduction of Cu(II) complex by O₂⁻.     

Structure and magnetic properties of a mixed‐ligand copper(II) complex

The hydrothermal synthesis of the novel complex poly[[μ₂‐N¹,N⁴‐bis(pyridin‐3‐yl)naphthalene‐1,4‐dicarboxamide‐κ²N³:N^3′](μ₄‐phthalato‐κ⁴O¹:O¹:O^1′:O^2′)copper(II)], [Cu(C₈H₄O₄)(C₂₂H₁₆N₄O₂)]_n, is described. With the phthalate ligand connecting neighbouring Cu^II cations, an infinite one‐dimensional chain is formed. Adjacent one‐dimensional chains are connected by the dicarboxamide ligand, forming an intriguing two‐dimensional framework. The magnetic properties and thermal stability of this complex are also described.     

Preparation and electrochemical study of an iron(II) complex of a pentadentate planar macrocyclic ligand

The macrocycle L, prepared by template condensation of bis-6,6-(-methylhydrazino)-4-phenyl-2,2:6,2-terpyridine with glyoxal, forms a stable crystalline complex of Fe^II, [Fe(L)(H₂O)₂][PF₆]₂, which has been used as a starting material for electrochemical studies on a series of seven coordinate Fe^II complexes [Fe(L)X₂]²⁺ (X=pyridine, 4-cyanopyridine, 4-aminopyridine, 4-dimethylaminopyridine, thiophene, imidazole, 2-methylimidazole or 1,2-dimethylimidazole). Cyclic voltammetry of the aquo complex in MeCN shows three reversible one electron redox waves in the range –0.35–1.70V versus Ag/AgBF₄ reference electrode.     

Magnetic and esr study of a dimeric copper(II) complex with a schiff base ligand derived from salicylhydrazide and o-hydroxypropiophenone

The ESR spectra and temperature dependence of the magnetic susceptibility of a Cu(II) complex with a Schiff-base ligand derived from salicylhydrazide and o-hydroxy-propiophenone suggest a dimeric structure with strong antiferromagnetic interactions within the pairs. A superexchange pathway via the oxygen atom is proposed.     

Tetranuclear copper(II) complex with the heterocyclic azomethine ligand: Crystal structure and magnetic properties

A tetranuclear copper(II) complex based on azomethine, which is the condensation product of 1-phenyl-3-methyl-4-formylpyrazol-5-one with 1,3-diaminopropan-2-ol, is synthesized. The complex includes two different tetranuclear clusters: symmetrical and unsymmetrical. They have a pseudo-cubane structure and are in a ratio of 1 : 2. The quantum-chemical calculation shows that the “unsymmetrical” conformer does not correspond to the local minimum on the molecular potential energy surface. Its existence is thus determined by the crystalline packing effects. According to the results of measurements of the temperature dependence of the magnetic susceptibility, the ground spin state is a singlet caused by the overall antiferromagnetic interaction between the copper ions. Accepting the molar magnetic susceptibility of the complex to be equal to the sum of susceptibilities of the “symmetrical” and “unsymmetrical” clusters and assuming that the spin-Hamiltonian for both clusters includes three exchange parameters, the temperature dependence of the magnetic susceptibility of the complex is satisfactorily described with the following parameters of the model: J _1A = ?178, J _2A = 80, J _3A = 18, J _1B = ?26, J _2B = ?74, J _3B = 46 cm^?1, g _A = g _B = 2.05.