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1.

Abstract  

Acetone [N-(3-hydroxy-2-naphthoyl)] hydrazone (H2AHNH) has been prepared and its structure confirmed by elemental analysis and 1H NMR spectroscopy. It has been used to produce diverse complexes with Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and U(VI)O2 ions. The complexes obtained have been investigated by thermal analysis, spectral studies (1H NMR, IR, UV–visible, ESR), and magnetic measurements. IR spectra suggest that H2AHNH acts as a bidentate ligand. The electronic spectra of the complexes and their magnetic moments provide information about geometries. The ESR spectra give evidence for the proposed structure and the bonding for some Cu(II) complexes. Thermal decomposition of the Ni(II) and Cu(II) complexes afforded metal oxides as final products. Kinetic data were obtained for each stage of thermal degradation of some of the complexes using the Coats–Redfern method. The formation of complexes in solution was studied pH-metrically and the order of their stability constants (log K) was found to be U(VI)O2 > Cu(II) > Zn(II) > Ni(II) > Cd(II) > Co(II). Antimicrobial and eukaryotic DNA studies were carried out.  相似文献   

2.

Abstract  

The complexation of a tripodal amine-catechol ligand tris((2,3-dihydroxybenzylamino)ethyl)amine (TRENCAT, L) with group-13 metal ions, viz., Al(III), Ga(III), and In(III), were investigated by means of potentiometric titrations and spectrophotometric measurements in an aqueous medium of 0.1 M KCl at 25 ± 1 °C. The ligand shows the potential to form various monomeric complexes of the types MLH3, MLH2, MLH, and ML. At low pH, the ligand is coordinated through three more acidic ortho-catecholic O-atoms to give MLH3 species. With the rise in pH, the species MLH3 releases three protons in steps from the meta-catecholic O-atoms to form MLH2, MLH, and ML. The order of stability Ga(III) > Al(III) > In(III) for the species MLH3 and MLH2 is changed into Al(III) > Ga(III) > In(III) for the species MLH and ML. The coordination modes, binding ability, selectivity, and the change in stability order were explained with the help of experimental evidence, molecular modeling calculations, and available literature.  相似文献   

3.
The competitive sorption of Cu(II), Eu(III) and U(VI) ions in aqueous solutions by TiO2, has been investigated by potentiometry at I = 0.1 M NaClO4, 25 °C and under atmospheric conditions. For Cu(II) ions the investigation was performed directly by means of a Cu2+ ion selective electrode, whereas for the Eu(III) and U(VI) ions indirectly based on competition reactions between the Cu(II) ion and the Eu(III) and U(VI) ions. Numerical analysis of the experimental data supports the formation of inner-sphere surface complexes and allows the evaluation of the formation constant of the (TiO)2Cu, which is found to amount to log β* = 4.3 ± 0.4. Addition of competing Eu(III) and U(VI) ions in the aqueous system leads to replacement of the Cu(II) by the competitor metal ion. Evaluation of the potentiometric data obtained from competition experiments indicates on an ion exchange mechanism. The formation constant of the Eu(III) and U(VI) species adsorbed on TiO2 is found to be log β* = 4.4 ± 0.7 and 4.8 ± 0.8, respectively. The relative affinity of the TiO2 surface for the metal ions under investigation is U(VI) > Eu(III) > Cu(II).  相似文献   

4.
Uranium triflate complexes. We review here the different preparations of uranium triflates that we have developed in the course of these last years in our laboratory. Protonation of 〚U〛–R and 〚U〛–NR2 (R = alkyl) bonds with pyridinium triflate constitutes a general and efficient route towards triflate complexes. This method is very suitable for the preparation of organometallic compounds such as U(Cp)3(OTf), U(Cp)2(OTf)2(py), U(Cp*)2(OTf)2, and U(Cot)(OTf)2(py), which have been crystallographically characterised. The homoleptic species U(OTf)n (n = 3, 4) are easily prepared by heating a mixture of uranium turnings or UH3 in triflic acid. By adjusting the temperature to 120 or 180 °C, either U(OTf)3 or U(OTf)4 is isolated. Treatment of UO3 with pure or aqueous solution of triflic acid leads to the non-solvated uranyl triflate UO2(OTf)2, which is more conveniently obtained by heating a suspension of UO3 in triflic anhydride. This reactant is an excellent dehydrating agent and enables the preparation of UO2(OTf)2 and Ce(OTf)4 from the hydrated starting materials.  相似文献   

5.
Uranium nitride compounds are important molecular analogues of uranium nitride materials such as UN and UN2 which are effective catalysts in the Haber–Bosch synthesis of ammonia, but the synthesis of molecular nitrides remains a challenge and studies of the reactivity and of the nature of the bonding are poorly developed. Here we report the synthesis of the first nitride bridged uranium complexes containing U(vi) and provide a unique comparison of reactivity and bonding in U(vi)/U(vi), U(vi)/U(v) and U(v)/U(v) systems. Oxidation of the U(v)/U(v) bis-nitride [K2{U(OSi(OtBu)3)3(μ-N)}2], 1, with mild oxidants yields the U(v)/U(vi) complexes [K{U(OSi(OtBu)3)3(μ-N)}2], 2 and [K2{U(OSi(OtBu)3)3}2(μ-N)2(μ-I)], 3 while oxidation with a stronger oxidant (“magic blue”) yields the U(vi)/U(vi) complex [{U(OSi(OtBu)3)3}2(μ-N)2(μ-thf)], 4. The three complexes show very different stability and reactivity, with N2 release observed for complex 4. Complex 2 undergoes hydrogenolysis to yield imido bridged [K2{U(OSi(OtBu)3)3(μ-NH)}2], 6 and rare amido bridged U(iv)/U(iv) complexes [{U(OSi(OtBu)3)3}2(μ-NH2)2(μ-thf)], 7 while no hydrogenolysis could be observed for 4. Both complexes 2 and 4 react with H+ to yield quantitatively NH4Cl, but only complex 2 reacts with CO and H2. Differences in reactivity can be related to significant differences in the U–N bonding. Computational studies show a delocalised bond across the U–N–U for 1 and 2, but an asymmetric bonding scheme is found for the U(vi)/U(vi) complex 4 which shows a U–N σ orbital well localised to U Created by potrace 1.16, written by Peter Selinger 2001-2019 N and π orbitals which partially delocalise to form the U–N single bond with the other uranium.

The first examples of molecular compounds containing the cyclic (U(vi)N)2 and (U(v)U(vi)N)2 cores were obtained by oxidation of the (U(v)U(v)N)2 analogue. Different bonding within these complexes yields different stability and reactivity with CO and H2.  相似文献   

6.

Abstract  

Three new transition metal complexes [CuL2Cl2], [NiL2Cl2], and [ZnL2Cl2], where L = Schiff base derived from isatin (1H-indole-2,3-dione) and tyramine (4-(2-aminoethyl)phenol), have been synthesized and characterized spectroscopically. The binding properties of these complexes with calf thymus DNA have been investigated by use of electronic absorption spectroscopy, viscosity measurement, cyclic voltammetry, and molecular docking analysis. Moreover, these complexes have been found to promote the cleavage of pUC19 DNA from the supercoiled form I to the open circular form II in the presence of hydrogen peroxide. The newly synthesized compounds were screened for antibacterial activity and subjected to molecular docking studies for inhibition of the enzyme Staphylococcus aureus sortase-A, which is a novel target for antibacterials.  相似文献   

7.
A new resin- Diphonix® in Diffusive Gradients in Thin Films (DGT) technique for the determination of uranium was investigated and compared with previously used binding phases for uranium, Chelex®-100 and Metsorb™. The DGT gel preparation and the elution procedure were optimized for the new resin. The U uptake on Diphonix® resin gel was 97.4 ± 1.5% (batch method; [U] = 20 μg L−1; 0.01 M NaNO3; pH = 7.0 ± 0.2). The optimal eluent was found to be 1 M 1-hydroxyethane-1, 1-diphosphonic acid (HEDPA) with an elution efficiency of 80 ± 4.2%. Laboratory DGT study on U accumulation using a DGT samplers with Diphonix® resin showed a very good performance across a wide range of pH (3–9) and ionic strength (0.001–0.7 M NaNO3). Diffusion coefficients of uranium at different pH were determined using both, a diffusion cell and the DGT time-series, demonstrating the necessity of the implementation of the effective diffusion coefficients into U-DGT calculations. Diphonix® resin gel exhibits greater U capacity than Chelex®-100 and Metsorb™ binding phase gels (a Diphonix® gel disc is not saturated, even with loading of 10.5 μmol U). Possible interferences with Ca2+ (up to 1.33 × 10−2 M), PO43−PO43 (up to 1.72 × 10−4 M), SO42−SO42 (up to 4.44 × 10−3 M) and −HCO3HCO3 (up to 8.20 × 10−3 M) on U-DGT uptake ([U] = 20 μg L−1) were investigated. No effect or minor effect of Ca2+, PO43−PO43, SO42−SO42, and −HCO3HCO3 on the quantitative measurement of U by Diphonix®-DGT was observed. The results of this study demonstrated the DGT technique with Diphonix® resin is a reliable and robust method for the measurement of labile uranium species under laboratory conditions.  相似文献   

8.
Batchwise uptake of Am(III), Pm(III), Eu(III), U(VI) and Pu(IV) by dihexyl-N,N-diethylcarbamoylmethylphosphonate (CMP) adsorbed on chromosorb (CAC) at nitric acid concentrations between 0.01 to 6.0M has been studied. The difference between the uptake behavior of Pu(IV) as compared to other actinides and lanthanides is discussed. The Am(III) and U(VI) species taken up on CAC were found to be Am(NO3)3·3CMP and UO2(NO3)2·2CMP, respectively. The equilibrium constants for the formation of these species have been evaluated and compared with those of similar species formed in liquid-liquid extraction. Batchwise loading of Pm(III) on CAC from 3.0M HNO3 has also been studied.  相似文献   

9.
1.  As the number of fused rings in the ligand of the cuprous organoacetylenides with the general formula ArCCCu, where Ar may be phenyl, -naphthyl, -naphthyl, or 9-anthracenyl, is increased, there is a tendency toward a bathochromic shift in the absorption, photoconductivity, and photoelectromotive-force spectra. Para substituents in the phenyl ring cause increasing bathochromic shifts in the absorption maxima along the series CH3 < h=">< cl=">< i="><>3 <>2.
2.  The photoeleetromotive-force spectra are similar to the absorption spectra, and the principal photoconductivity maximum is located on the edge of the absorption band.
3.  The photoconductivities determined from the absorption spectra and the energies of the forbidden gaps determined from the photoelectromotive-force spectra correlate well with each other. This indicates that the conductivity of the cuprous organoacetylenides is intrinsic. The p type of the photocurrent carrier has been established.
4.  The nature of the spectra of the cuprous organoacetylenides as a function of the method of construction has been discussed, and the decisive role of the steric factors in the migration of the photocurrent carriers has been shown.
  相似文献   

10.

Abstract  

A series of novel acenaphthopyrazine derivatives was synthesized from acenaphthylene-1,2-dione via three steps, including bromination, cyclization, and SNArH reaction. These new compounds exhibited potential antiproliferative activity against MCF-7 cells in vitro, and 3-[2-(dimethylamino)ethylamino]acenaphtho[1,2-b]pyrazine-8,9-dicarbonitrile exhibited the highest activity (IC 50 = 4.60 μM). DNA-binding experiments suggested that these derivatives bind to DNA through intercalation with intrinsic binding constants K all above 105 M−1. Optical property studies indicated that these compounds have long emission wavelength (λ em > 560 nm), high quantum yields in toluene (Φf = 0.59 for 3-(morpholin-4-yl)acenaphtho[1,2-b]pyrazine-8,9-dicarbonitrile), and large Stokes shift (ΔS > 130 nm).  相似文献   

11.
The redox chemistry of uranium is dominated by single electron transfer reactions while single metal four-electron transfers remain unknown in f-element chemistry. Here we show that the oxo bridged diuranium(iii) complex [K(2.2.2-cryptand)]2[{((Me3Si)2N)3U}2(μ-O)], 1, effects the two-electron reduction of diphenylacetylene and the four-electron reduction of azobenzene through a masked U(ii) intermediate affording a stable metallacyclopropene complex of uranium(iv), [K(2.2.2-cryptand)][U(η2-C2Ph2){N(SiMe3)2}3], 3, and a bis(imido)uranium(vi) complex [K(2.2.2-cryptand)][U(NPh)2{N(SiMe3)2}3], 4, respectively. The same reactivity is observed for the previously reported U(ii) complex [K(2.2.2-cryptand)][U{N(SiMe3)2}3], 2. Computational studies indicate that the four-electron reduction of azobenzene occurs at a single U(ii) centre via two consecutive two-electron transfers and involves the formation of a U(iv) hydrazide intermediate. The isolation of the cis-hydrazide intermediate [K(2.2.2-cryptand)][U(N2Ph2){N(SiMe3)2}3], 5, corroborated the mechanism proposed for the formation of the U(vi) bis(imido) complex. The reduction of azobenzene by U(ii) provided the first example of a “clear-cut” single metal four-electron transfer in f-element chemistry.

Both a masked and the actual complex [U(ii){N(SiMe3)2}3]+ effect the reduction of azobenzene to yield a U(vi) bis-imido species providing the first example of a “clear-cut” metal centred four-electron reduction in f-element chemistry.  相似文献   

12.

Abstract  

Cyclization of a variety of chalcones to flavanones catalyzed by 1 mol% phosphomolybdic acid (PMA) supported on silica as a mild, efficient, and reusable catalyst was carried out in high yields. PMA-SiO2 is an efficient, inexpensive, and green catalyst which gave high conversion yields and could be recycled up to three times without significant loss in activity.  相似文献   

13.

Abstract  

Three nickel(II) complexes, namely [Ni(BH)3](H2O)(NO3)(ClO4) 1, [Ni(BH)2(NO3)2] 2 and [Ni(BH)(Tren)](ClO4)2 3 (BH = Benzoylhydrazine, Tren = Tris(2-aminoethyl)amine) have been synthesized and characterized by physico-chemical techniques. X-ray crystallographic analysis shows the nickel to be six-coordinated in these complexes. The complexes are efficient catalysts for the dismutation of superoxide in alkaline DMSO-NBT assays. The IC50 values are 74,108 and 105 μM for 1, 2 and 3, respectively.  相似文献   

14.
Abstract  Acetone [N-(3-hydroxy-2-naphthoyl)] hydrazone (H2AHNH) has been prepared and its structure confirmed by elemental analysis and 1H NMR spectroscopy. It has been used to produce diverse complexes with Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and U(VI)O2 ions. The complexes obtained have been investigated by thermal analysis, spectral studies (1H NMR, IR, UV–visible, ESR), and magnetic measurements. IR spectra suggest that H2AHNH acts as a bidentate ligand. The electronic spectra of the complexes and their magnetic moments provide information about geometries. The ESR spectra give evidence for the proposed structure and the bonding for some Cu(II) complexes. Thermal decomposition of the Ni(II) and Cu(II) complexes afforded metal oxides as final products. Kinetic data were obtained for each stage of thermal degradation of some of the complexes using the Coats–Redfern method. The formation of complexes in solution was studied pH-metrically and the order of their stability constants (log K) was found to be U(VI)O2 > Cu(II) > Zn(II) > Ni(II) > Cd(II) > Co(II). Antimicrobial and eukaryotic DNA studies were carried out. Graphical abstract     相似文献   

15.
Solvent extraction of U(VI) with di-isodecyl phosphoric acid (DIDPA)/dodecane from nitric acid medium has been investigated for a wide range of experimental conditions. Effect of various parameters including nitric acid concentration, DIDPA concentration, temperature, stripping agents, and other impurities like rear earths, transition metal ion, boron, aluminum ion on U(VI) extraction has been studied. The species extracted in the organic phase is found to be UO2(NO3)(HA2)·H2A2 at lower acidity (<3.0 M HNO3). Increase in temperature lead to the decrease in extraction with the enthalpy change by ∆H = −16.27 kJ/mol. Enhancement in extraction of U(VI) from nitric acid medium was observed with the mixture of DIDPA and tri butyl phosphate (TBP). The stripping of U(VI) from organic phase (DIDPA–U(VI)/dodecane) with various reagents followed the order: 4 M H2SO4 > 5% (NH4)2CO3 > 8 M HCl > 8 M HNO3 > Water. High separation factors between U(VI) and impurities suggested that the use of DIDPA for purification of uranium from multi elements bearing solution.  相似文献   

16.

Abstract  

Two new neutral mononuclear Zn(II) and Mn(II) complexes with pyridine-2-amidoxine and carboxylate ligands, [Zn(paH)2(OAc)2]·2CH3OH (paH = pyridine-2-amidoxine, HOAc = acetic acid) (1), and [Mn(paH)2(OAc)2]·C2H5OH·2H2O (2), have been prepared and characterized structurally by X-ray crystallography. 1 and free paH exhibit photoluminescence at room temperature in solid state, which is rare so fare for metal complexes with oxime-based ligand. The emissions of 1 and free paH arise from the metal-perturbed paH-based π → π* ligand-to-ligand charge transfer transition (LLCT) and π → π* charge transfer transition in nature, respectively, in terms of the density functional theory level calculations and molecular orbital analyses.  相似文献   

17.
The compounds RbAuUSe3, CsAuUSe3, and RbAuUTe3 were synthesized at 1073 K from the reactions of U, Au, Q, and A2Q3 (A=Rb or Cs; Q=Se or Te). The compound CsAuUTe3 was synthesized at 1173 K from the reaction of U, Au, Te, and CsCl as a flux. These isostructural compounds crystallize in the KCuZrS3 structure type in space group Cmcm of the orthorhombic system. The structure consists of layers that contain nearly regular UQ6 octahedra and distorted AuQ4 tetrahedra. The infinite layers are separated by bicapped trigonal prismatic A cations. The magnetic behavior of RbAuUSe3 deviates significantly from Curie–Weiss behavior at low temperatures. For T>200 K, the values of the Curie constant C and the Weiss constant θp are 1.82(9) emu K mol−1 and −3.5(2)×102 K, respectively. The effective magnetic moment μeff is 3.81(9) μB. Formal oxidation states of A/Au/U/Q may be assigned as +1/+1/+4/−2, respectively.  相似文献   

18.
In this paper the dependence of build-up233U,232U,233Pa and fission products from ThO2 irradiated in HFETR on integral thermal neutron fluxes and neutron spectra have been investigated. The yields of all above nuclides in ThO2 increase with the increase of integral thermal neutron fluxes at different neutron spectra. The values of233U/232Th increase with the increases of th and decreases with the increase of fast/thermal neutron ratios (f/th). The values of232U/233U increase with the increase of both th and f/th ratio. The amount of fission products relative to original irradiated thorium decreases with the increase of f/th ratios. These results could be used to evaluate the behaviour of thorium-based nuclear fuel in reactor.  相似文献   

19.

Abstract  

The behavior of N2O adsorbed on the external surface of H-capped (6,0), (7,0), (8,0), and Al-doped (6,0) zigzag single-walled carbon nanotubes was studied by using density functional calculations. Geometry optimizations were carried out at the B3LYP/6-31G* level of theory using the Gaussian 03 suite of programs. We present the nature of the N2O interaction in selected sites of the nanotubes. Binding energies corresponding to adsorption of the N2O are calculated to be in the range 4–21 kJ mol−1. More efficient binding energies cannot be achieved by increasing the nanotube diameter. We also provide the effects of N2O adsorption on the electronic properties of the nanotubes.  相似文献   

20.

Abstract  

Quantum mechanical density functional theory (DFT) calculations were used to derive the most probable structures of the bambus[6]uril·H3O+ and bambus[6]uril·(H3O+)2 cationic complex species. In these two complexes, each of the considered H3O+ ions is bound by three strong linear hydrogen bonds to the three corresponding carbonyl oxygens of the parent macrocyclic receptor.  相似文献   

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