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1.
The Knudsen mass-loss effusion technique was used to measure the vapour pressures at different temperatures of two crystalline ruthenium complexes: tris(1,1,1-trifluoro-2,4-pentanedionate)ruthenium(III) {Ru(tfacac)3}, between T =  350.20 K and T =  369.17 K and tris(1,1,1,5,5,5-hexafluoro-2,4-pentanedionate)ruthenium(III) {Ru(hfacac)3} between T =  299.15 K and T =  313.14 K. From the temperature dependence of the vapour pressure of the crystalline compounds, the standard molar enthalpies of sublimation were derived by the Clausius–Clapeyron equation and the molar entropies of sublimation at equilibrium pressures were calculated. By using an estimated value for the heat capacity differences between the gas and the crystal phases the standard, po =  105Pa, molar enthalpies, entropies, and Gibbs energies of sublimation at T =  298.15 K, were derived:  相似文献   

2.
Mononuclear ruthenium(III) complexes of the type [RuX(EPh3)2(L)] (E = P or As; X = Cl or Br; L = dibasic terdentate dehydroacetic acid thiosemicarbazones) have been synthesized from the reaction of thiosemicarbazone ligands with ruthenium(III) precursors, [RuX3(EPh3)3] (where E = P, X = Cl; E = As, X = Cl or Br) and [RuBr3(PPh3)2(CH3OH)] in benzene. The compositions of the complexes have been established by elemental analysis, magnetic susceptibility measurement, FT-IR, UV–vis and EPR spectral data. These complexes are paramagnetic and show intense d–d and charge transfer transitions in dichloromethane. The complexes show rhombic EPR spectra at LNT which are typical of low-spin distorted octahedral ruthenium(III) species. All the complexes are redox active and display an irreversible metal centered redox processes. Complex [RuCl(PPh3)2(DHA–PTSC)] (5) was used as catalyst for transfer hydrogenation of ketones in the presence of isopropanol/KOH and was found to be the active species.  相似文献   

3.
Reactions of Schiff bases (H2apahR) derived from acetophenone and acid hydrazides, triethylamine and [Ru(PPh3)3Cl2] (1:2:1 mole ratio) in methanol provide cyclometallated ruthenium(III) complexes of formula trans-[Ru(apahR)(PPh3)2Cl] in 74–81% yields. The complexes have been characterized by elemental analysis, magnetic susceptibility, spectroscopic (infrared, electronic and EPR) and electrochemical measurements. X-ray crystal structures of two representative complexes have been determined. In each complex, the metal centre is in distorted octahedral CNOClP2 coordination sphere assembled by the C,N,O-donor meridionally spanning apahR2?, the chloride and the two mutually trans-oriented PPh3 molecules. All the complexes are one-electron paramagnetic (μeff. = 1.85–1.98 μB) and display rhombic EPR spectra in frozen (120 K) dichloromethane-toluene (1:1) solution. Electronic spectra of the complexes display several absorptions within 470–270 nm due to ligand-to-metal charge transfer and ligand centred transitions. The complexes are redox active and display a Ru(III)  Ru(II) reduction and a Ru(III)  Ru(IV) oxidation in the potential ranges ?0.66 to ?0.70 V and 0.75 to 0.80 V (vs. Ag/AgCl), respectively.  相似文献   

4.
The present work introduces thiacalix[4]arene adopting 1,3-alternate conformation with alkyl-malonate terminal substituents as ligands for Gd(III) ions. pH-dependent complex formation of Gd(III) ions via alkyl-malonate substituents in aqueous DMSO solutions results in a precipitation. The precipitated complexes were converted into hydrophilic colloids of “plum-pudding” morphology, where the Gd(III) complexes form hard small (1.5–4 nm) cores included into larger (about 180 nm) soft PSS shells. The precipitate-to-colloid transformation is facilitated by polystyrolsulfonate (PSS) for Gd(III) complexes with thiacalix[4]arene bearing propyl-malonate groups, while the presence of PSS triggers a dissolution of the precipitated complexes for thiacalix[4]arenes with pentyl-malonate substituents. To a lesser extent the similar tendency disturbs the formation of PSS-stabilized colloids on the basis of butyl-malonate substituted thiacalix[4]arene. The PSS-stabilized colloids exhibit high longitudinal and transverse relaxivities (r1 = 23.8 and r2 = 29.4 mM−1 s−1 at 0.47 T, respectively), while the recoating of the PSS-stabilized colloids with polyethyleneimine is accompanied by the dissolution of the hard cores. High relaxivity along with low cytotoxicity of PSS-stabilized colloids indicates their applicability as contrast agents in MRI.  相似文献   

5.
Electrospray ionization quadrupole ion trap mass spectrometry (ESI-QIT/MS) of the ammonium cerium(III) phosphomolybdate complex (NH4)11[Ce(III)(PMo11O39)2] in aqueous media has revealed a concentration-dependent behavior. Under fixed instrumental parameters, the Ce-containing polyoxomolybdate complexes H2Ce(III)P2Mo22O753? and Ce(III)PMo11O382? are the primary species present at 11 mM (pH = 4.3); at 0.7 mM (pH = 3.6), Ce(III)PMo10O352? is the predominant species, Ce(III)PMo11O382? is quite diminished, and H2Ce(III)P2Mo22O753? is absent. As a result of the complex isotopic fingerprints from multiple molybdenums, compositions of such ions are difficult to assign—successive collision induced dissociation (CID) of large ions produced smaller ions for which calculated and experimental isotopic patterns could be compared. The oxidation state of Ce and the number of counter cations on negative complexes was discerned from spectra of ions containing 1H+ and 7Li+. The overall result is an ESI method applicable to phosphomolybdate complexes containing redox sensitive f-block metal ions such as Ce(IV) and Pu(III/IV). Dissociation studies also gave insight into favored fragmentation pathways, and generated gas ions with empirical formulae similar to known condensed-phase ions. Deconvolution of concentration- and pH-dependent solution behavior via ESI/MS and 31P NMR spectroscopy showed speciation dependent on solution concentration, not on pH.  相似文献   

6.
Gold nanorods (GNRs) were synthesized by a seed–mediated growth approach followed by TEOS polymerization leading to the formation of silica layer surrounding the gold nanorod core. TEM images showed that the silica-coated gold nanorods (GNRs@SiO2) were dispersed with an average aspect ratio of 3.1 for the GNRs cores and a uniform thickness of the silica shell. The core/shell nanocomposites were further used as efficient supports for the immobilization of hemoglobin (Hb) to fabricate a novel biosensor. The immobilized Hb showed an enhanced electron transfer for its heme Fe(III) to Fe(II) redox couple. This biosensor showed an excellent bioelectrocatalytic activity towards H2O2 with a linear range from 8.0 × 10−7 to 6.1 × 10−5 M, and the detection limit was 6.0 × 10−8 M at 3σ. The apparent Michaelis–Menten constant of the immobilized hemoglobin was calculated to be 0.13 mM.  相似文献   

7.
The characterisation of light lanthanide(III) complexes with pyridine-3,5-dicarboxylic acid of the formula Ln2pdc3·nH2O where Ln denotes lanthanides from La to Gd, pdc = C7H5NO42−; n = 6 for Ce(III), n = 7 for Pr(III) and Sm(III), n = 8 for La and n = 13 for Nd(III), Eu(III) and Gd(III) was performed by the thermal analysis TG-DTA and the simultaneous infrared evolved gas analysis TG-FTIR. Heating of the crystalline complexes resulted in the dehydration process at first. Next, dehydrated compounds decompose releasing of CO2, CO, CH4 and hydrocarbons. Free pyridine molecules were detected only in the gaseous products of lanthanum(III) complex decomposition.  相似文献   

8.
《Comptes Rendus Chimie》2014,17(5):490-495
A new complex of [Ni3(dcp)2(H2O)10] (1) (H3dcp = 3,5-pyrazoledicarboxylic acid) has been synthesized from H3dcp and Ni(NO3)2·6H2O by hydrothermal reaction. Complex 1 has the discrete trinuclear structure. Three Ni(II) ions are bridged by two dcp3− ligands, with 10 coordinated water molecules as terminal ligands. The molecules of [Ni3(dcp)2(H2O)10] extend into three-dimensional supramolecular architectures by intermolecular O–H···O hydrogen bonds as well as π-π stacking interactions. Magnetic susceptibility measurement shows that a weak antiferromagnetic interaction is operative between nickel(II) ions and an excellent simulation of the experimental data gives D = 5.27 cm−1, J = −2.19 cm−1 and g = 2.05.  相似文献   

9.
Six Ru(II) complexes of formula [Ru(L)2(PPh3)2] have been prepared where LH = 4-(aryl)thiosemicarbazones of thiophen-2-carbaldehyde. X-ray crystal structures of five of the complexes are reported. In all the complexes ruthenium is six coordinate with a distorted octahedral cis-P2, cis-N2, trans-S2 donor environment, and each of the two thiosemicarbazone ligands are coordinated in a bidentate fashion forming a four membered chelate ring. The complexes undergo a one-electron oxidation at ~0.5 V vs. Ag/AgCl. The EPR spectrum of the electrochemically oxidized solution at 100 K shows a rhombic signal, with transitions at g1 = 2.27, g2 = 2.00 and g3 = 1.80. DFT calculations on one of the complexes suggest that there is 35% ruthenium and 17% sulfur orbital contribution to the HOMO. These results suggest that the assignment of metal atom oxidation states in these compounds is not unambiguous.  相似文献   

10.
Binding of copper to three peptide fragments of prion (Cu2+ binding sites: 60–91, 92–96 and 180–193 amino acid residues) was investigated by anodic stripping voltammetry to determine the stoichiometries of Cu2+-prion peptide interactions. The method relies on the synthesis of N-terminally acetylated/C-terminally amidated peptide fragments of prion by solid-phase synthesis and direct monitoring of the oxidation current of copper in the absence and presence of each prion fragment. Titration curves of Cu2+ with Ac-PHGGGWGQ-NH2, Ac-GGGTH-NH2 and Ac-VNITKQHTVTTTT-NH2 were obtained in concentrations ranging from 8.52 × 10?7 to 5.08 × 10?6, 3.95 × 10?7 to 1.94 × 10?6 and 7.82 × 10?8 to 4.51 × 10?7 M, respectively. The acquired data were used to calculate the stoichiometries (one peptide per Cu2+ ion for all the three studied systems) and apparent dissociation constants (Kd = 4.37 × 10?8–3.50 × 10?10 M) for the three complexes.  相似文献   

11.
The mononuclear oxalato-containing chromium(III) complexes of general formula [Cr(AA)(C2O4)2]? (AA = α-diimine type ligand) are able to produce a large variety of heterometallic complexes by acting as ligands towards either fully solvated metal ions or preformed cationic complexes with available coordination sites. This review focuses on the structural diversity of the polynuclear complexes (oligonuclear and coordination polymers) which are generated by the bis(oxalato)chromate(III) species, with a special emphasis to their magnetic properties.  相似文献   

12.
A new Mn (III) Schiff-base coordination compound, [Mn(L)(NCS)]2 (H2L = N,N′-bis(5-chlorosalicylidene)-1,2-diaminoethane), has been synthesized and characterized structurally and magnetically. The target compound is a phenoxo-bridged dimeric compound with the isothiocyanate coordinating in a usual bent mode. A magnetic susceptibility study reveals that the target compound exhibits antiferromagnetic intra-dimer coupling between Mn (III) ions. The low temperature heat capacity of the compound over the temperature range (2 to 300) K has been measured using the heat capacity option of a Quantum Design Physical Property Measurement System (PPMS). The thermodynamic functions in the experimental temperature range have been determined by curve fitting. The standard entropy and enthalpy of the as-prepared compound at T = 298.15 K have been calculated to be (924.52 ± 10.17) J · K−1 · mol−1 and (133.47 ± 1.47) kJ · mol−1, respectively.  相似文献   

13.
A series of novel neutral nickel complexes, aryl (phenyl or naphthyl) nickel N-alkyl-6-(1-(arylimino)ethyl)picolinamides, were synthesized and characterized by NMR and IR spectroscopy and elemental analysis. Single-crystal X-ray diffraction analyses of the complexes C2, C3 and C7 reveal distorted square-planar geometry along with the molecular structure of one free ligand L1. On activation with diethylaluminum chloride (Et2AlCl), the nickel complexes exhibited moderate catalytic activities for ethylene oligomerization, and the catalytic activity was up to 2.45 × 105 g mol?1(Ni) h?1 in the presence of 1 equiv. PPh3. Moreover, these complexes also exhibit moderate activities for Kumada–Corriu reaction and polymerization of methyl methacrylate.  相似文献   

14.
Novel Schiff base Cu(II), Ni(II), Co(II) and Zn(II) complexes have been designed and synthesized using the macrocyclic ligand derived from the condensation of diethylphthalate with Schiff base, obtained from benzene-1,2-diamine and 3-benzylidene-pentane-2,4-dione. The ligand and its complexes have been characterized by analytical and spectral techniques. DNA binding properties of these complexes have been investigated by UV–vis, viscosity measurements, cyclic voltammetric and differential pulse voltammogram studies. The intrinsic binding constants for Co(II), Ni(II), Cu(II) and Zn(II) complexes are 1.6 × 106, 1.8 × 106, 2.0 × 106 and 1.5 × 106 M?1 respectively which are obtained from electronic absorption experiment. Control DNA cleavage experiments using pUC19 supercoiled (SC) DNA and minor groove binder (distamycin) suggest the major groove binding tendency for the synthesized complexes. In the presence of a reducing agent like 3-mercaptopropionic acid (MPA), the synthesized complexes show chemical nuclease activity under dark reaction condition. The complexes also show efficient photo-induced DNA cleavage activity on irradiation with a monochromatic UV light of 360 nm in the presence of inhibitors. Control experiments show inhibition of cleavage in the presence of singlet oxygen quencher like sodium azide and enhancement of cleavage in D2O, suggesting the formation of singlet oxygen as a reactive species in a type-II process.  相似文献   

15.
《Polyhedron》2007,26(9-11):2330-2334
The precursors [Fe(III)(SYL)Cl] (SYLH2) = N,N′-bis(1-hydroxy-Y-2-benzyliden)-1,6-diamino-3-thiohexane, (Y = H, 3EtO, 5Me) are high-spin (S = 5/2) complexes. The precursors are combined with [Fe(II)(CN)6]4− and [Co(III)(CN)6]3− to yield star-shaped heptanuclear clusters, [Fe(II)(CN–Fe(III)SYL)6]Cl2 and [Co(III)(CN–Fe(III)SYL)6]Cl3. The star-shaped compounds are high-spin (HS) systems at room temperature. On cooling to 20 K some of the iron(III) centers perform some HS–HS transition.  相似文献   

16.
A new PVC membrane based strontium(II) ion-selective electrode has been constructed using acetophenone semicarbazone as a neutral carrier. The sensor exhibits a Nerstian response for strontium(II) ion over a wide concentration range 1.0 × 10−2–1.0 × 10−7 M with the slope of 29.4 mV/per decade. The limit of detection was 2.7 × 10−8 M. It was relatively fast response time (<10 s for concentration ⩾1.0 × 10−3 and <15 s for concentration of ⩾1.0 × 10−6 M) and can be used for 8 months without any considerable divergence in potentials. The proposed sensor revealed relatively good selectivity and high sensitivity for strontium(II) over a mono, di, trivalent cation and can be used in a pH range of 2.5–10.5. It was also successfully used as an indicator electrode in potentiometer titration and in the analysis of concentration in various real samples.  相似文献   

17.
The precursor [FeIII(L)Cl] (LH2 = N,N′-bis(2′-hydroxy-benzyliden)-1,6-diamino-3-azahexane) has been prepared and Mössbauer spectroscopy assigned a high-spin (S = 5/2) state at room temperature. The precursor is combined with the bridging units [SbV(X)6]? (X = CN?, NCS?) to yield star-shaped heptanuclear clusters [(LFeIII–X)6SbV]Cl5. The star-shaped compounds are in general high-spin systems at room temperature. On cooling to 20 K some of the iron(III) centers switch to the low-spin state as indicated by Mössbauer spectroscopy, i.e. multiple electronic transitions. While the cyano-bridged complex performs a multiple spin transition the thiocyanate-compound shows no significant population at both temperatures.  相似文献   

18.
Chemical speciation [Sb(V) and Sb(III)] affects the mobility, bioavailability and toxicity of antimony. In oxygenated environments Sb(V) dominates whereas thermodynamically unstable Sb(III) may occur. In this study, a simple method for the determination of Sb(III) in non acidic, oxygenated water contaminated with antimony is proposed. The determination of Sb(III) was performed by anodic stripping voltammetry (ASV, 1–20 μg L−1 working range), the total antimony, Sb(tot), was determined either by inductively coupled plasma mass spectrometry (ICP-MS, 1–100 μg L−1 working range) or inductively coupled plasma optical emission spectrometry (ICP-OES, 100–10,000 μg L−1 working range) depending on concentration. Water samples were filtered on site through 0.45 μm pore size filters. The aliquot for determination of Sb(tot) was acidified with 1% (v/v) HNO3. Different preservatives, namely HCl, L(+) ascorbic acid or L(+) tartaric acid plus HNO3, were used to assess the stability of Sb(III) in synthetic solutions.The method was tested on groundwater and surface water draining the abandoned mine of Su Suergiu (Sardinia, Italy), an area heavily contaminated with Sb. The waters interacting with Sb-rich mining residues were non acidic, oxygenated, and showed extreme concentrations of Sb(tot) (up to 13,000 μg L−1), with Sb(III) <10% of total antimony. The stabilization with L(+) tartaric acid plus HNO3 appears useful for the determination of Sb(III) in oxygenated, Sb-rich waters. Due to the instability of Sb(III), analyses should be carried out within 7 days upon the water collection. The main advantage of the proposed method is that it does not require time-consuming preparation steps prior to analysis of Sb(III).  相似文献   

19.
In this paper, we discuss the synthesis and electrochemical properties of a new material based on iron oxide nanoparticles stabilized with poly(diallyldimethylammonium chloride) (PDAC); this material can be used as a biomimetic cathode material for the reduction of H2O2 in biofuel cells. A metastable phase of iron oxide and iron hydroxide nanoparticles (PDAC–FeOOH/Fe2O3-NPs) was synthesized through a single procedure. On the basis of the Stokes–Einstein equation, colloidal particles (diameter: 20 nm) diffused at a considerably slow rate (D = 0.9 × 10? 11 m s? 1) as compared to conventional molecular redox systems. The quasi-reversible electrochemical process was attributed to the oxidation and reduction of Fe3+/Fe2+ from PDAC–FeOOH/Fe2O3-NPs; in a manner similar to redox enzymes, it acted as a pseudo-prosthetic group. Further, PDAC–FeOOH/Fe2O3-NPs was observed to have high electrocatalytic activity for H2O2 reduction along with a significant overpotential shift, ΔE = 0.68 V from ? 0.29 to 0.39 V, in the presence and absence of PDAC–FeOOH/Fe2O3-NPs. The abovementioned iron oxide nanoparticles are very promising as candidates for further research on biomimetic biofuel cells, suggesting two applications: the preparation of modified electrodes for direct use as cathodes and use as a supporting electrolyte together with H2O2.  相似文献   

20.
Some new metal(II) complexes, ML2[M = Co, Ni, Cu and Zn], of 2-acetylthiophene benzoylhydrazone ligand (HL) containing a trifunctional SNO-donor system have been synthesized and characterized on the basis of physicochemical data by elemental analysis, magnetic moment, molar conductance, thermogravimetric and spectroscopic (electronic, IR, 1H NMR and 13C NMR) data. The ligand functions as monobasic SNO tridentates where the deprotonated enolic form is preferred in the coordination producing distorted octahedral complexes.  相似文献   

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