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1.
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The series of complexes [Mn(IV)(X-SALPN)(2-O)]2, 1: X=5-OCH3; 2: X=H; 3: X=5-Cl; 4: X=3,5-diCl; 5: X=5-NO2, contain [Mn2O2]4+ cores with Mn-Mn separations of 2.7 . These molecules can be protonated to form [Mn(IV)(X-SALPN)(2-O,OH)]2 + in which a bridging oxide is protonated. The pKa values for the series of [Mn(IV)(X-SALPN)(2-O,OH)]2 + track linearly versus the shift in redox potential with a slope of 84 mV/pKa. This observation suggests that the [Mn2O2]4+ core can be considered as a unit in which the free energy of protonation is directly related to the ability to reduce the Mn(IV) ion. The marked sensitivity of the reduction potential to the presence of protons presents a mechanism in which an enzyme can control the oxidizing capacity of an oxo manganese cluster by the degree and timing of oxo bridge protonation.Abbreviations AnH+CF3SO3 - anilinium triflate - DMA N,N-dimethyl acetamide - H2SALPN 1,3-bis(salicylideneiminato)propane - H2(5-Cl-SALPN) 1,3-bis(5-chlorosalicylideneiminato)propane; - H2(3,5-diCl-SALPN) 1,3-bis(3,5-dichlorosalicylideneiminato)propane - H2(5-NO2-SALPN) 1,3-bis(5-nitorosalicylideneiminato)propane - H2(5-OMe-SALPN) 1,3-bis(5-methoxysalicylideneiminato)propane - LuH+CF3SO3 - 2,4-lutidinium triflate - ME3NH+Ph4B- trimethylammonium tetraphenylborate - OEC oxygen evolving complex - PyH+ClO4 - pyridinium perchlorate - SCE saturated calomel electrode  相似文献   

3.
Oxygen-17 and tungsten-183 NMR studies on solutions of orange tungsten(IV), prepared in 2 M p-toluenesulphonic acid (Hpts) solution via acid catalyzed hydrolysis of potassium hexachlorotungstate(IV) in 2 M Hpts followed by treatment with a single DOWEX 50W X2 cation-exchange column, confirm the formation of the species; [W33-O)(μ2-O)3(OH2)8Cl]3+ as major product in addition to [W33-O)(μ2-O)3(OH2)9]4+ under these conditions in a manner not possible by spectrophotometric means. Further characterization of the green W(III,III,IV) mixed-valence reduction product has also been carried out with in addition an estimation of the formal reduction potential for the W(IV)3/W(III,III,IV) redox couple.  相似文献   

4.
Available data on the kinetic processes in H2-O2-O2(a 1Δ g ) mixtures are analyzed theoretically, and the ranges in which the rate constants of these processes can vary are determined. The processes of energy transformation in an O2(a 1Δ g )-H2-H-HO2 system in the approximations of the fast and slow (in comparison with the vibrational relaxation time of the HO2 radical) quenching of the electronically excited state are considered. The experiments on the quenching of singlet delta oxygen (SDO) molecules O2(a 1Δ g ) excited in a microwave discharge at a temperature of 300 K and pressure of 6 Torr in a lean hydrogen-oxygen mixture are simulated (by a lean fuel mixture is meant a mixture in which the ratio of the fuel to the oxidizer mass fraction is less than the stoichiometric ratio, which is 2: 1 for a hydrogen-oxygen mixture). It is shown that, over the experimental observation times, the SDO quenching frequency depends on the concentration of molecular hydrogen, the residual odd oxygen fraction in the gas flow, and the ratio between the rate constants of kinetic processes involving HO2 and HO2* radicals. Simulations of the microwave discharge and the transport of excited oxygen along the drift tube make it possible to determine the residual odd oxygen concentration in the gas flow. Recommendations on the choice of the rate constants for the O2(a 1Δ g ) + HO2)A″, v3″ = 0) ? O2 + HO2*(A′, v3′ = 1), HO2*(A′v3′ ≤ 1) + O2(a 1Δ g ) → HO2*(A′,v3′ ≥ 6) + O2, and HO2*(A′,v3′ ≤ 1) + O2(a 1Δ g ) → H + O2 + O2 processes are given. It is shown that, in the case of slow quenching in a H2-O2-O2(a 1Δ g ) mixture at a low temperature, the intensity of hydrogen oxidation is enhanced due to the reaction + HO2*(A′,v3′ ≤ 1) + O2(1Δ) → H + O2 + O2.  相似文献   

5.
Dinuclear cobalt(II) complexes Co2(bpmp)(OAc)3 (1) and Co2(bpcp)(OAc)3 (2) have been synthesized by using acyclic ligands 2,6-bis((4-(pyridin-2-yl)pyrimidin-2-ylthio)methyl)-4-methylphenol [H(bpmp)] and 2,6-bis((4-(pyridin-2-yl)pyrimidin-2-ylthio)methyl)-4-chlorophenol [H(bpcp)] with versatile coordination sites. X-ray analysis uncovered that complex 1 · 3H2O contains a μ-phenoxo-μ-acetato-bis(η2-acetato) dicobalt(II, II) core. Magnetic susceptibility was measured for 1 over the temperature range 1.8-300 K, and the best theoretical fitting parameters were g = 2.12(6), J = −3.63(9) cm−1 and D = −12(4) cm−1.  相似文献   

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7.
[Ru2O(L)6(acetate)2](PF6)2 {L = pyridine 1; 4-picoline 2} undergo aquation in acetone-water (60:40 v/v) mixed solvent to form diaquo complexes in solution as shown by proton NMR studies. Ligands trans to the μ-oxo group are substituted. These diaquo complexes react with substituted pyridines and imidazoles to form respective disubstituted complexes. Rate constants for aquation and complexation under pseudo first order conditions of ligand are reported. Rate constants increase with increase in the basicity of incoming ligand. Disubstituted complexes proposed to be formed in solution have been isolated and characterized by elemental analyses, visible spectra, proton NMR. Single crystal X-ray structures of 4-picoline and 4-methylimidazole disubstituted complexes are reported. All the isolated complexes exhibit a strong peak between 570 and 585 nm in their visible absorption spectra. λmax varies linearly with ∑pka of terminal ligands. In disubstituted complexes of 1 with 2-methyl and 4-methyl imidazole deprotonation of N(1)H of methylimidazoles takes place in solution.  相似文献   

8.
In the murine IgH gene intronic enhancer (ENHiH), two major functional domains were reported. One is the E4/octomer region and another includes the A and B motifs. In the human ENHiH, it was reported that the HE2, which corresponds to the murine B, and E6 motifs play an important role in an enhancer activity and a tissue-specificity at cellular level. Here we examined thein vivo function of the E6, A and HE2 motifs within the human ENHiH by using the transgenic mice technique. The A and HE2 motifs together revealed almost the same enhancer function as the whole human ENHiH, but the E6 motif had lesser enhancer acitivty and tissue-specificity.  相似文献   

9.
A series of dinickel acetato complexes [LNi2(OAc)(solvent)x](ClO4)2 (1-3, 5) as well as related complexes [LNi2(OAc)2](OAc) (4) and [LNi2(OAc)(NO3)2] (6), all derived from three pyrazolate-based binucleating ligands, have been prepared and characterized by X-ray crystallography. The solid state structures reveal different acetate binding modes (μ1,3-bridging and bidentate chelating) plus severe twisting and tilting of the μ1,3-acetate bridges with respect to their bimetallic scaffolds, reflecting the great flexibility of carboxylate coordination. Magnetic properties of all six complexes have been investigated, and the strength of antiferromagnetic coupling is discussed in the light of the structural differences, suggesting a magnetostructural correlation for acetato-bridged complexes.  相似文献   

10.
《Inorganica chimica acta》2006,359(11):3632-3638
Synthesis and characterization of linked cluster [{Os3(CO)102-H)}222-NC6H4C6H4N}] (1) from the reaction of [Os3Rh(μ-H)3(CO)12] with aniline in the presence of an excess amount of 4-vinyl phenol in refluxing heptane is reported. A similar reaction with [Os3(CO)10(NCMe)2] as starting material gave a known compound, [Os3(CO)102-H)(μ2-HNC6H5)] (2). The treatment of complexes 1 and 2 with Wilkinson’s catalyst in refluxing heptane respectively, yielded [{Os3(CO)92-H)PPh3}222-NC6H4C6H4N}] (3). An interesting and unexpected C–C coupling of phenyl-amido ligands was observed in complexes 1 and 3, which is believed to be catalysed by the organometallic rhodium species. The newly synthesized compounds 1 and 3 were fully characterized by IR, 1H NMR spectroscopy, mass spectroscopy, elemental analysis, and X-ray crystallography. Both structures 1 and 3 comprise two triangles of osmium atoms. The two triangular osmium metal cores are linked by a bi-amido ligand via the two nitrogen atoms N(1) and N(1)* and N(1) and N(2), at their equatorial sites. The electronic absorption spectra of complexes 1, 2, and 3 display both low energy absorption, dπ (Os)  π* (amido) metal-to-ligand charge-transfer (MLCT) transition, and π  π* intra-ligand electronic transitions of the amido and bi-amido ligands.  相似文献   

11.
Three doubly-bridged, trinuclear copper(II) compounds with hydroxo and carboxylato bridges, 1[Cu3(L1)2(μ-OH)2(μ-propionato)2](1), [Cu3(L2)2(μ-OH)2(μ-propionato)2(DMF)2] (2) and 1{[Cu3(L3)2(μ-OH)2(μ-propionato)2]} [Cu3(L3)2(μ-OH)2(μ-propionato)2(DMF)2]} (3) [HL1 = N-(pyrid-2-ylmethyl)benzenesulfonylamide, HL2 = N-(pyrid-2-ylmethyl)toluenesulfonylamide, HL3 = N-(pyrid-2-ylmethyl)naphthalenesulfonylamide], have been synthesized and characterized. 1 is built from [Cu3(L1)2(μ-OH)2(μ-propionato)2] clusters. Each unit contains three copper(II) with two different coordination environments: the terminal centers are square-base pyramidal whereas the central copper is square planar. 2 presents a similar square-base pyramidal geometry in the terminal centers, but the central copper is six-coordinate. 3 shows an unusual 1D coordination polymer comprised of two distinct building blocks: one similar to that found in 1 and the other similar to that found in 2. The magnetic susceptibility measurements (2-300 K) reveal a ferromagnetic interaction between the Cu(II) ions with J values of 76.0, 55.0, and 48.0 cm−1 for 1, 2, and 3, respectively. Emission spectroscopy, thermal denaturation, viscosimetry and cyclic voltammetry show an interaction of the complexes with DNA through the sugar-phosphate backbone. All three Cu(II) complexes were found to be very efficient agents of plasmid DNA cleavage in the presence of ascorbato or mercaptopropionic acid. Both the kinetics and the mechanism of the cleavage reaction have also been examined.  相似文献   

12.
The synthesis, structure and characterization of the dinuclear Mn(II) complex [Mn2(LO)(μ-OAc)2](ClO4) (1) where LOH = 2,6-bis{bis(2-(2-pyridyl)ethyl)aminomethyl)}-4-methylphenol are reported. The reaction of Mn(ClO4)2 · 6H2O with the dinucleating ligand LOH and H3CCOONa in the presence of NEt3 in dry, degassed methanol and under an argon atmosphere, yields 1 as a colorless powder. The crystal structure of 1, determined by X-ray diffraction methods, shows a dinuclear Mn(II) complex in which two Mn(II) ions, each in six-coordinate approximate octahedral coordination, are bridged by the phenolate oxygen of LO and by two acetate ions in a syn,syn-1,3-bridging mode. The Mn-Mn distance is 3.557(1) Å and Mn-Ophenolate-Mn angle is 112.50(9)°. Cyclic voltammetry of 1 in acetonitrile solution shows a quasi-reversible wave at E1/2 = 0.65 V, for the Mn2(II,II)/Mn2(II,III) redox process, and an irreversible oxidation peak at Ep,c = 1.22 V versus Ag/AgCl for the Mn2(II,III) to Mn2(III,III) oxidation process. Controlled potential electrolysis of 1 in acetonitrile solution at 0.85 V (versus Ag/AgCl) takes up 1 F of charge per mole of 1 to yield a brown solution of the Mn2(II,III) state of the complex, which, however, is unstable and reverts back to the Mn2(II,II) state in solution at room temperature. Least square fitting of the variable temperature magnetic susceptibility measurements on powdered sample of 1 is obtained with g = 1.888, J = −2.75 cm−1, Par = 0.008, TIP = 0. The low −J value and the room temperature calculated magnetic moment of the complex (5.30 BM per Mn(II)), which is less than the spin-only moment of Mn(II), show that the two Mn(II) ions are weakly antiferromagnetically coupled.  相似文献   

13.
Here we report on a method to track individual molecules on nanometer length and microsecond timescales using an optical microscope. Our method is based on double-labeling of a molecule with two spectrally distinct fluorophores and illuminating it with laser pulses of different wavelengths that partially overlap temporally. We demonstrate our method by using it to resolve the motion of short DNA oligomers in solution down to a timescale of 100 μs.  相似文献   

14.
15.
《Inorganica chimica acta》2006,359(7):2029-2040
Two μ-alkoxo-μ-carboxylato bridged dinuclear copper(II) complexes, [Cu2(L1)(μ-HCO2)] (1) ((H3L1 = 1,3-bis(5-bromosalicylideneamino)-2-propanol)), [Cu2(L2)(μ-HCO2)] · dmf (2) (H3L2 = 1,3-bis(3,5-chlorosalicylideneamino-2-propanol)), and two μ-alkoxo-μ-dicarboxylato doubly bridged tetranuclear copper(II) complexes, [{Cu2(L3)}2(μ-O2C–C(CH3)2–CO2)] · 5H2O · 3CH3OH (3) ((H3L3 = 1,3-bis(salicylid-deneamino)-2-propanol)) and [{Cu2(L3)}2(μ- O2CCH2–C6H4–CH2CO2)] · 2H2O (4) have been prepared and characterized. The single crystal X-ray analysis shows that the structures of complexes 1 and 2 are dimeric with two adjacent copper(II) atoms bridged by μ-alkoxo-μ-carboxylato ligands with the Cu⋯Cu distances and Cu–O(alkoxo)–Cu angles are 3.511 Å and 132.85° for 1, 3.517 Å and 131.7° for 2, respectively. Complexes 3 and 4 consist of μ-alkoxo-μ-dicarboxylato doubly bridged tetranuclear Cu(II) complexes with mean Cu–Cu distances and Cu–O–Cu angles of 3.158 Å and 108.05° for 3 and 3.081 Å and 104.76° for 4, respectively. Magnetic measurements reveal that 1 and 2 are strong antiferromagnetically coupled with 2J = −156 and −152 cm−1, respectively, while 3 and 4 exhibit ferromagnetic coupling with 2J = 86 and 155.2 cm−1, respectively. The 2J values of 14 are linearly correlated to the Cu–O–Cu angles. Dependence of the pH at 25 °C on the reaction rate of oxidation of 3,4-di-tert-butylcatechol (3,5-dtbc) to the corresponding quinone catalyzed by 14 was studied. Complexes 14 exhibit high catecholase-like activity at pH 9.0 and 25 °C for oxidation of 3,5-di-tert-butylcatechol.  相似文献   

16.
The syntheses, structures, and magnetic properties of two new μ-alkoxo-μ-pyrazolato heterobridged compounds, [Cu II2(L1-F)(μ-prz)] (1) and [Cu II2(L1-2OMe) (μ-prz)] · 0.5 CH3CN (2) (prz=pyrazolato; H2L1-F=1,3-bis(3-fluorosalicylideneamino)-2-propanol; H2L1-2OMe=1,3-bis(4,6-dimethoxy salicylideneamino)-2-propanol) have been reported. Compound 1 crystallizes in triclinic space group with a=8.6392(10) Å, b=10.6431(9) Å, c=11.6809(13) Å, α=85.972(8)°, β=71.492(9)°, and γ=72.221(9)°, while the unit cell parameters of 2 are as follows: space group: monoclinic C2/c, a=28.2948(5) Å, b=7.3033(2) Å, c=26.3933(5) Å, and β=96.243(1)°. The variable-temperature magnetic susceptibility measurements reveal that the metal centers in both the compounds are antiferromagnetically coupled with J=−200 cm−1 for 1 and J=−175 cm−1 for 2. The magnetic behaviors have been explained on the basis of two opposing factors, complementarity and countercomplementarity of magnetic orbitals.  相似文献   

17.
The trinuclear complex [L2Cu3(CF3CO2)4] (1) has been synthesized and its crystal structure determined. It consists of a linear arrangement of Cu(II) centers. The central copper atom is bonded to six oxygen atoms and has a tetragonally distorted octahedral geometry, while the terminal copper atoms are bonded to three oxygen and two nitrogen atoms and show a distorted square pyramidal geometry. The complex shows di-μ(O,O′) syn-syn carboxylate bridging as well as monoatomic (μ-O) bridging, along with phenolate (μ-O) oxygen bridging. Cryomagnetic investigations in the range 2-300 K revealed an antiferromagnetic spin exchange interaction with J = −95.7 cm−1, based on the isotropic exchange model Hex = −2J[S1 · S2 + S2 · S3].  相似文献   

18.
Unlike other chlorometallate complexes that catalyze the photodecomposition of haloalkanes through photodissociation of a chlorine atom, both and catalyze chloroform decomposition through a process that appears to involve C-H bond breakage from an excited state association complex with chloroform. This would account for the greatly retarded rate of decomposition in CDCl3 and for the generation of CCl4 as a side product. In chloroform, and are in slow equilibrium with each other. The rate for the conversion of - in chloroform at 23 °C obeys the expression (0.03 M−1 s−1) [][Cl]. The equilibrium constant, K = [][Cl]2/[]2, was estimated to be 3 × 10−3 M in CHCl3.  相似文献   

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20.
Seven diiridium(II) complexes were synthesized by ligand substitution reactions of [Ir2(μ-O2CMe)2Cl2(CO)2] (1) and [Ir2(μ-O2CMe)2Cl2(CO)2(py)2] (2).The reaction of 2 with the silver salt of a less coordinating anion, AgSbF6, gave a cationic complex [Ir2(μ-O2CMe)2Cl(CO)2(py)3]SbF6 (3).A tricarbonyl cationic complex [Ir2(μ-O2CMe)2(CO)3Cl(py)2]SbF6 (4) was obtained under a CO atmosphere.Complex 2 reacted with AgO2CCF3 to give [Ir2(μ-O2CMe)2Cl(O2CCF3)(CO)2(py)2] (5) in toluene.[Ir2(μ-hiq)2(CO)2Cl2] (Hhiq = 1-hydroxyisoquinoline, 6) was synthesized by the bridging-ligand substitution of 1 with Hhiq.Its axial adducts [Ir2(μ-hiq)2Cl2(CO)2L2] (L = Mepy (4-methylpyridine), 7 or PPh3, 8) were synthesized by addition of the ligands to a suspension of 6.In the structures of 7 and 8, two iridium atoms are bridged by two hiq ligands in a head-to-tail arrangement.The reaction of 1 with Hmhp (2-hydroxy-4-methylpyridine) led to triply bridged [Ir2(μ-mhp)3(CO)2Cl(Hmhp)] (9).In complex 9, all the mhp ligands bridge between the Ir atoms in a head-to-head manner.The Ir-Ir distances of 3, 4, 5, 7 and 8 are 2.6047(7), 2.6216(9), 2.5899(9), 2.5933(5) and 2.634(2) Å, respectively, which are similar to those observed in[Ir2(μ-O2CMe)2Cl2(CO)2L2]. The Ir-Ir distance of 2.5512(4) Å in 9 is shorter than in the other complexes.  相似文献   

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