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1.
Rui Yang  Yu Gong  Mingfei Zhou   《Chemical physics》2007,340(1-3):134-140
The reaction products of palladium atoms with molecular oxygen in solid argon have been investigated using matrix isolation infrared absorption spectroscopy and quantum chemical calculations. In addition to the previously reported mononuclear palladium–dioxygen complexes: Pd(η2–O2) and Pd(η2–O2)2, dinuclear palladium–dioxygen complexes: Pd22–O2) and Pd22–O2)2 were formed under visible light irradiation and were identified on the basis of isotopic substitution and theoretical calculations. In addition, experiments doped with xenon in argon coupled with theoretical calculations suggest that the Pd(η2–O2), Pd22–O2) and Pd22–O2)2 complexes are coordinated by two argon or xenon atoms in solid argon matrix, and therefore, should be regarded as the Pd(η2–O2)(Ng)2, Pd22–O2)(Ng)2 and Pd22–O2)2(Ng)2 (NgAr or Xe) complexes isolated in solid argon.  相似文献   

2.
The solid–liquid equilibria of the ternary system H2O–Fe(NO3)3–Co(NO3)2 were studied by using a synthetic method based on conductivity measurements.

Two isotherms were established at 0 and 15 °C, and the stable solid phases which appear are the iron nitrate nonahydrate (Fe(NO3)3·9H2O), the iron nitrate hexahydrate (Fe(NO3)3·6H2O), the cobalt nitrate hexahydrate (Co(NO3)2·6H2O) and the cobalt nitrate trihydrate (Co(NO3)2·3H2O).  相似文献   


3.
We reported here four structures of lanthanide–amino acid complexes obtained under near physiological pH conditions and their individual formula can be described as [Tb2(dl-Cys)4(H2O)8]Cl2 (1), [Eu43-OH)4(l-Asp)2(l-HAsp)3(H2O)7] Cl · 11.5H2O (2), [Eu8(l-HVal)16(H2O)32]Cl24 · 12.5H2O (3), and [Tb2(dl-HVal)4(H2O)8]Cl6 · 2H2O (4). These complexes showed diverse structures and have shown potential application in DNA detection. We studied the interactions of the complexes with five single-stranded DNA and found different fluorescence enhancement, binding affinity and binding stoichiometry when the complexes are bound to DNA.  相似文献   

4.
The reaction of Cp(dppe)FeI with the ligands 2,2′- and 4,4′-dithiobispyridine (S2(Py)2) give the mononuclear or binuclear complexes of the type [Cp(dppe)Fe-S2(Py)2]PF6, [Cp(dppe)Fe---SPy]PF6 or [{Cp(dppe)Fe}2-μ-SPy](PF6)2 depending on the reaction condition. Reaction of Cp(dppe)FeI with dithiobispyridines in presence of TlPF6 as halide abstractor and using CH2Cl2 as a solvent gives the complexes [Cp(dppe)Fe-4,4′-S2(Py)2)2]PF6 (1) and [CpFe(dppe)-2,2′-S2(Py)2]PF6 (2) whereas the same reaction using CH3OH as a solvent and NH4PF6 as the halide abstractor leads to the formation of the FeIII–thiolate complex [Cp(dppe)Fe-2,2′-SPy]PF6 (3) and the mixed-valence complex [Cp(dppe)FeIII-μSPy-FeII(dppe)Cp](PF6)2 (4). Magnetic and ESR measurements are in agreement with one unpaired electron delocalized between them. Mössbauer data indicate clearly the presence of two different iron sites, each one of the N-bonded and S-bonded iron atoms, with intermediate oxidation state FeII---FeIII. An electron transfer intervalence absorption was observed for this complex at 780 nm (in CH2Cl2). By applying the Hush theory the intervalence parameters were obtained; =0.028, Hab=361 cm−1 which indicate Class II Robin–Day. Estimation of the rate electron transfer affords a value kth=6.5×106 s−1. Solvent effect on the intervalence transition follow the Hush prediction for high dielectric constants solvents which permit the evaluation of the outer and inner-sphere reorganizational parameters, which were analyzed and discussed. The electronic interaction parameters compare well with those found for electron transfer in metalloproteins.  相似文献   

5.
A novel dinuclear complex [Cu2(μ-L)4(HL)2] (1) was isolated from starting 2-pyridone (HL) via a resonance and a tautomeric transformation. Each copper centre is in a square-pyramidal coordination sphere, defined by two oxygen atoms (Cu–O4 1.978(5), Cu–O11 1.964(4) Å) and two nitrogen atoms (Cu–N2 2.003(5), Cu–N3 2.007(5) Å) of four bridging deprotonated pyridin-2-olates and an oxygen atom on the top from a neutral 2-pyridone (Cu–O2 2.227(5) Å), analogous to tetracarboxylate paddle-wheel complexes. Compound 1 was compared with mixed pyridin-2-olato/methanoato analogues [Cu2(μ-HCO2)2(μ-L)2(HL)2] · 2CH3CN (2) and [Cu2(μ-HCO2)2(μ-L)2(HL)2] (2a) (2a is an air stable form obtained from 2 outside mother-liquid). The EPR spectra of air stable 1 and 2a show three signals Hz1, H2 and Hz2, typical for the binuclear systems with spin S = 1, both revealing strong antiferromagnetism 2J = −334 (1) and −324 cm−1 (2a). Interestingly, only for 1 additional H1 signal at 100 mT is noticed (D(1) = 0.293 cm−1 <  = 0.320 cm−1 < D(2a) = 0.347 cm−1). On the other hand, several broad signals in the 100–450 mT region, only in the high temperature spectrum for 2a are observed. These results are in agreement with the magnetic susceptibility analysis.  相似文献   

6.
The rare earth(III) salt catalysed asymmetric Diels–Alder reaction of cyclopentadiene with a chiral dienophile in supercritical carbon dioxide (scCO2) proceeded rapidly to give the adduct with a higher diastereoselectivity than that in dichloromethane; Yb(ClO4)3 gave the endo adduct with value up to 77% de at 40°C, 8 MPa. The chiral rare earth diketonate catalyzed hetero Diels–Alder reaction of the Danishefsky's diene with benzaldehyde gave a higher yield and an enantioselectivity in scCO2 than that in dichloromethane. Scandium/pybox 8a complex catalysed asymmetric Diels–Alder reaction of 3-crotonoyl-2-oxazolidinone with cyclopentadiene in the presence of MS4A proceeded smoothly in scCO2 to give the endo adduct 10 in a good yield with up to 88% ee.  相似文献   

7.
Four novel tetranuclear macrocyclic complexes of the formula [(CuLi)3Fe](ClO4)3·3H2O (i=1–4, Li are the dianions of the [14]N4 and [15]N4 macrocyclic oxamides, namely 2,3-dioxo-5,6:13,14-dibenzo-7,12-bis(ethoxycarbonyl)-1,4,8,11-tetraazacyclotetradeca-7,11-diene, 2,3-dioxo-5,6:13,14-dibenzo-9-methyl-7,12-bis(ethoxycarbonyl)-1,4,8,11-tetraazacyclotetradeca-7,11-diene and 2,3-dioxo-5,6:14,15-dibenzo-7,13-bis(ethoxycarbonyl)-1,4,8,12-tetraazacyclotetradeca-7,12-diene] have been prepared and characterized. These complexes are the first examples of oxamido-bridged Cu(II)–Fe(III) heterometallic species. Cryomagnetic studies on [(CuL1)3Fe](ClO4)3·3H2O (1) and [(CuL3)3Fe](ClO4)3·3H2O (3) (77–300 K) revealed that the Cu(II) and Fe(III) ions interact antiferromagnetically through the oxamido bridge, with the exchange integral J=−30.8 cm−1 for 1 and J=−28.7 cm−1 for 3 based on . The interaction parameters have been compared with that of the related [Cu3Mn] compound.  相似文献   

8.
The bimetallic [Pt(NH3)4]2[W(CN)8][NO3]·2H2O is characterised by single-crystal X-ray diffraction [S.G.P21/m(11), a=8.0418(7), b=19.122(2), c=9.0812(6) Å, Z=2]. All platinum centres have the square-plane D4h geometry with average dimensions Pt(1)–N 2.042(2) and Pt(2)–N 2.037(10) Å. The octacyanotungstate anion has the square-antiprismatic D4d configuration with average dimensions W(1)–C 2.164(13), C–N 1.140(12), W(1)–N 3.303(5) Å. The structure exhibits two different mutual orientations of Pt versus W units resulting in Pt(2)–W(1), W(1)* separations of 4.77(2), 4.55(2)* and Pt(1)–W(1) of 6.331(8) Å. A centrosymmetric structure reveals groups of two distinct columns: the first is formed by intercalated NO3 between parallel [Pt(1)(NH3)4]2+ planes and the second consists of [W(CN)8]3− interlayered by, parallel to square faces of W-antiprisms, [Pt(2)(NH3)4]2+. The structure is stabilised through a three-dimensional hydrogen bond network via nitrogen atoms of cyanide ligands, hydrogen atoms of NH3 ligands, water molecules and oxygen atoms of NO3 counteranions. The vibrational pattern and the range of ν(CN) frequencies attributable to the electronic environment of W(V) and W(IV) are consistent with the ground state Pt(II)↔W(V) charge transfer.  相似文献   

9.
The synthesis and characterization of ruthenium(II) complexes, [RuCl2(dmso)2(bfmh)] (1; dmso = dimethyl sulfoxide, bfmh = benzoic acid furan-2-ylmethylene-hydrazide), [RuCl2(dmso)2(btmh)](2; btmh = benzoic acid thiophen-2-ylmethylene-hydrazide), [RuCl2(dmso)2(bfeh)](3; bfeh = benzoic acid (1-furan-2-yl-ethylidene)-hydrazide) and [RuCl2(dmso)2(bpeh)](4; bpeh = benzoic acid (1-pyridin-2-yl-ethylidene)-hydrazide) are described. The ligands, when treated with either cis-[RuCl2(dmso)4] or trans(Cl)–[RuCl2(dmso)2(bpy)], resulted in the same products. This has been confirmed by IR spectra and single crystal X-ray diffraction studies. The redox behaviors of the complexes have been found to be strongly dependent on the electronic nature of the moieties present in the hydrazone ligands. The binding of the complexes to Herring sperm DNA has been studied by absorption titration and cyclic voltammetry. But, due to the random change in the absorption on the addition of DNA, only a qualitative result rather than a quantitative result has been obtained. All the complexes have been found to bind DNA through different modes to different extents. The antibacterial properties of the ligands and the complexes have been studied against five pathogenic bacteria and also the minimum inhibitory concentrations (MIC) of all the ligands and complexes 2 and 4 have been evaluated.  相似文献   

10.
Electrocatalytic water oxidation to evolve O2 was studied on a Nafion–RuO2–Ru(bpy)32+ composite electrode. The O2 evolution current efficiency was largely improved for the multi-component electrode over the Nafion–RuO2 and Nafion–Ru(bpy)32+ individuals. The redox mediation through the Ru(bpy)32+ was found to dominate over the RuO2 catalytic effect in the water oxidation mechanism. The specific surface area of the RuO2, which was prepared at different temperatures (300–700°C), used in fabricating the composite electrode also played an important role in the overall water oxidation mechanism. Both the reaction and electrode parameters were optimized to get effective electrocatalytic current values in this study.  相似文献   

11.
Unsaturated fatty acids [C8H17CH=CH(CH2)nCO2H] (n=7, 11) acids are cleanly dihydroxylated by hydrogen peroxide in the presence of catalytic amounts of H2WO4. Under molecular oxygen, in the presence of catalytic amounts of N-hydroxyphthalimide and Co(acac)3, the diols resulting from erucic (n=11) and oleic (n=7) acid undergo C–C cleavage.  相似文献   

12.
Several types of Cr bound siloxane polymers were prepared by various modes of polymerization. The co-polymerization of (EtO)3SiPhCr(CO)3 and Si(OMe)4 by the sol–gel process, and its subsequent curing, led to a hydrogenation reactive polymer catalyst. Its catalytic reactivity was retained throughout several cycles, contrary to siloxane polymers prepared by different methods. The hydrogenation reaction was studied with methyl sorbate, 3-nonen-2-one, and 1-octyne. Regio- and stereoselectivities were studied. Cyclohexane as solvent was found to be superior to THF in retaining the catalytic activity upon recycling of the polymeric catalyst in the hydrogenation reactions.  相似文献   

13.
Poly(methyl methacrylate) (PMMA) modified titanium and zirconium n-butoxide–ethyl acetoacetate (EAA) complex [M5-Ti(OBun)2(EAA)2 and M5-Zr(OBun)2(EAA)2] were obtained from trialkoxysilane-functional PMMA and EAA modified titanium and zirconium alkoxide via the sol–gel method. Infrared (IR), 13C nuclear magnetic resonance (NMR) spectroscopy, and thermogravimetric analysis (TGA) were used to analyze the structures and properties of the hybrids with various proportions of metal oxide species. The effect of the complex of metal oxides and EAA ligands on structure and thermo-oxidative degradation of the M5-Ti(OBun)2(EAA)2 and M5-Zr(OBun)2(EAA)2 hybrids were investigated in this study. The 1H spin–diffusion path length of the hybrids was in a nanometer scale as estimated from the spin–lattice relaxation time in a rotating frame (TH). The apparent activation energies (Ea), evaluated by van Krevelen’s method, for random scission of PMMA segments in hybrids decreased with increasing metal oxide content.  相似文献   

14.
The sulfoxides of penicillin derivatives are important pharmaceutical intermediates and can be prepared by air oxidation of corresponding sulfides catalyzed by cobalt(III) acetylacetonate (Co(acac)3). However, when using the homogeneous catalyst, it is very difficult to separate the catalyst from product, which makes it impossible to reuse the catalyst directly. While the heterogeneous Co(acac)3 encapsulated by sol–gel method can solve the problem. They have high selectivity and activity. They are leach proof and can be recycled in numerous runs. The sol–gel precursor can be tetraethoxysilane (TEOS) or tetrabutyl titanate (TBOTi) or triisopropyl aluminate (TIOAl). FT-IR and N2 adsorption was employed to characterize the sol–gel catalyst. HPLC was used to analyze the conversion of penicillin derivatives.  相似文献   

15.
Infrared and Raman spectra for metal–string complexes M3(dpa)4X2 (M = Ni, Co, dpa = di(2-pyridyl)amido, and X = Cl, NCS) are studied. We assign the Ni3 asymmetric stretching vibration to infrared lines at 304 and 311 cm−1 for Ni3(dpa)2Cl2 and Ni3(dpa)2(NCS)2, respectively. A Raman shift at 242 cm−1 is assigned to the Ni3 symmetric stretching mode. For Co3 complexes a line for the Co3 asymmetric stretching mode appears at 313 and 331 cm−1 for Co3(dpa)2Cl2 and Co3(dpa)2(NCS)2, respectively.  相似文献   

16.
The reactions of R2P–P(SiMe3)2 (R = Ph, iPr and iPr2N) with BuLi in THF or DME solution lead to ion-contacted lithium derivatives R2P–P(SiMe3)Li · 3THF (R = iPr, iPr2N) with tetrahedrally surrounded Li atoms and to the solvent-separated ionic [Li · 3DME]+[Ph2P–PSiMe3] with an octahedrally surrounded Li atom as confirmed by X-ray crystal structure analysis. The reaction of BuLi with Ph2P–P(SiMe3)2 is accompanied with a significant side-reaction leading to Ph2P–PPh2 and to LiP(SiMe3)2.  相似文献   

17.
The reactions of the diruthenium carbonyl complexes [Ru2(μ-dppm)2(CO)4(μ,η2-O2CMe)]X (X=BF4 (1a) or PF6 (1b)) with neutral or anionic bidentate ligands (L,L) afford a series of the diruthenium bridging carbonyl complexes [Ru2(μ-dppm)2(μ-CO)22-(L,L))2]Xn ((L,L)=acetate (O2CMe), 2,2′-bipyridine (bpy), acetylacetonate (acac), 8-quinolinolate (quin); n=0, 1, 2). Apparently with coordination of the bidentate ligands, the bound acetate ligand of [Ru2(μ-dppm)2(CO)4(μ,η2-O2CMe)]+ either migrates within the same complex or into a different one, or is simply replaced. The reaction of [Ru2(μ-dppm)2(CO)4(μ,η2-O2CMe)]+ (1) with 2,2′-bipyridine produces [Ru2(μ-dppm)2(μ-CO)22-O2CMe)2] (2), [Ru2(μ-dppm)2(μ-CO)22-O2CMe)(η2-bpy)]+ (3), and [Ru2(μ-dppm)2(μ-CO)22-bpy)2]2+ (4). Alternatively compound 2 can be prepared from the reaction of 1a with MeCO2H–Et3N, while compound 4 can be obtained from the reaction of 3 with bpy. The reaction of 1b with acetylacetone–Et3N produces [Ru2(μ-dppm)2(μ-CO)22-O2CMe)(η2-acac)] (5) and [Ru2(μ-dppm)2(μ-CO)22-acac)2] (6). Compound 2 can also react with acetylacetone–Et3N to produce 6. Surprisingly [Ru2(μ-dppm)2(μ-CO)22-quin)2] (7) was obtained stereospecifically as the only one product from the reaction of 1b with 8-quinolinol–Et3N. The structure of 7 has been established by X-ray crystallography and found to adopt a cis geometry. Further, the stereospecific reaction is probably caused by the second-sphere π–π face-to-face stacking interactions between the phenyl rings of dppm and the electron-deficient six-membered ring moiety of the bound quinolinate (i.e. the N-included six-membered ring) in 7. The presence of such interactions is indeed supported by an observed charge-transfer band in a UV–vis spectrum.  相似文献   

18.
A mild new procedure for preparing protected peptide thioesters, based on Ca2+-assisted thiolysis of peptide–Kaiser oxime resin (KOR) linkage, is described. Ac-Ile-Ser(Bzl)-Asp(OcHx)-SR (Ac: acetyl; Bzl: benzyl; cHx: cyclohexyl), model peptide, was readily released from the resin by incubating the peptide–KOR at 60 °C in mixtures of DMF with n-butanethiol [R = (CH2)3CH3] or ethyl 3-mercaptopropionate [R = (CH2)2COOCH2CH3] containing Ca(CH3COO)2. After serine and aspartic acid side-chain deprotection under acid conditions, Ac-Ile-Ser-Asp-S(CH2)2COOCH2CH3 was successfully obtained with good quality and high yield. This type of C-terminal modified peptide may act as an excellent acyl donor in peptide segment condensation by the thioester method, native chemical ligation and enzymatic methods.  相似文献   

19.
Cheng S  Gao F  Krummel KI  Garland M 《Talanta》2008,74(5):1132-1140
Two different organometallic ligand substitution reactions were investigated: (1) an achiral reactive system consisting of Rh4(CO)12 + PPh3  Rh4(CO)11PPh3 + CO in n-hexane under argon; and (2) a chiral reactive system consisting of Rh4(CO)12 + (S)-BINAP  Rh4(CO)10BINAP + 2CO in cyclohexane under argon. These two reactions were run at ultra high dilution. In both multi-component reactive systems the concentrations of all the solutes were less than 40 ppm and many solute concentrations were just 1–10 ppm. In situ spectroscopic measurements were carried out using UV–vis (Ultraviolet–visible) spectroscopy and UV–vis CD spectroscopy on the reactive organometallic systems (1) and (2), respectively. The BTEM algorithm was applied to these spectroscopic data sets. The reconstructed UV–vis pure component spectra of Rh4(CO)12, Rh4(CO)11PPh3 and Rh4(CO)10BINAP as well as the reconstructed UV–vis CD pure component spectra of Rh4(CO)10BINAP were successfully obtained from BTEM analyses. All these reconstructed pure component spectra are in good agreement with the experimental reference spectra. The concentration profiles of the present species were obtained by performing a least square fit with mass balance constraints for the reactions (1) and (2). The present results indicate that UV–vis and UV–vis-CD spectroscopies can be successfully combined with an appropriate chemometric technique in order to monitor reactive organometallic systems having UV and Vis chromophores.  相似文献   

20.
The rhodium-catalyzed hydroformylation of 1-dodecene was investigated with a series of sulfonated water-soluble phosphine ligands at a pressure of 60 bar CO/H2 and a temperature of 120 °C. Seven different groups of water-soluble phosphines were used for our investigations. We established an optimized ligand/rhodium ratio of 5 for the phosphines 1a, [Ph2P(CH2)2S(CH2)2SO3Na], and 1b, [Ph2P(CH2)2S(CH2)3SO3Na]. The utilized arylphosphino-thioether-alkylsulfonates formed with Rh(I) compounds highly active catalysts which could be recycled. The addition of detergents speeds up the hydroformylation reaction, but disturbs the phase separation (recycling). The best promotion effect and the smallest negative influence on phase separation gave polyoxyethylene–polyoxypropylene–polyoxyethylene triblock co-polymers. The ratio of 1-dodecene/rhodium could be increased up to 10.000 and we achieved turnover numbers (TONs)>50.000 without any surfactant and TONs of about 65.000 in presence of the co-polymers owing to the recycling on the catalytic system.  相似文献   

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