Synthesis and crystal structure of the trimetallic erbium tetrahydride complex [Li(THF)4][{(ButCp)2Er(μ-H)} 3-(μ3-H)]

Reaction of [(Bu′tCp)2Er(μ-CI)]2 with Bu′Li in 1:1 molar ratio in THF at -78℃, after work-up, afforded the trimetallic erbium tetrahydride complex [Li(THF)4][{(Bu′Cp)2Er(μ-H)}3(μ3-H)] (1) by β-hydrogen elimination reaction. Crystal structure determination reveals that complex 1 has discrete ion pair structure. The anion is composed of three (Bu′Cp)2Er units to form a triangle array connected by three bridged hydrogen atoms, and the fourth hydrogen atom coordinated to three Er^3 ions. The coordination num-ber for each Er^3 ion is 9.     

Unexpected carbon-oxygen bond cleavage of THF promoted by guanidinate titanium complex/lithium diisopropylamide： Synthesis and crystal structure

An unexpected carbon-oxygen bond cleavage of THF （THF = tetrahydrofuran） promoted by guanidinate titanium complex was described. Guanidinate lithium [Pr2 ^1NC（NCy）2]Li （Cy = cyclohexyl） formed in situ reacted with TiCl4（THF）2 in a 2：1 molar ratio to produce the guanidinate titanium chloride [Pr2 ^1NC（NCy）2]2TiCl2 （1） in good yield. The reaction of [Pr2 ^1NC（NCy）2]2TiCl2 with lithium diisopropylamide in THF afforded an unexpected [Pr2 ^1NC（NCy）2]2Ti（OBu^n）2 （2）, which was formed by the cleavage of carbon-oxygen bond of THF. Complexes 1 and 2 were fully characterized by elemental analysis, NMR and IR spectroscopies, and X-ray crystal structure determination for complex 2.     

The concentration quenching characteristics of 5D3-7FJ and 5D4-7FJ (J=0―6) transitions of Tb3+ in YBO3:Tb3+ phosphor

The photoluminescence quenching behaviors of ^5D3-^7Fj and ^5D4-^7Fj （J = 0—6） transitions of Tb^3＋ in YBO3：Tb under 130—290 nm excitation were systematically investigated. The results revealed that the quenching concentrations of both ^5D3-^7Fj and ^5D4-^7Fj transitions of Tb^3＋ in YBO3：Tb were mainly dependent on excitation wavelength. Particularly, the quenching concentrations of ^5D4-^7Fj transitions of Tb^3＋ under 130—290 nm excitation were correlated with excitation bands of YBO3：Tb. The quenching concentrations of ^5D3-^7Fj transitions remained at low concentration （2%） under 186—290 nm excitation and then increased gradually with energy of incoming excitation photon when excited at 130—186 nm. This dependence should be involved in their excitation mechanisms and quenching pathway in particular excitation region.[第一段]     

Half-sandwich β-diketonato complexes of zirconium and their application as catalysts to ethylene polymerization

The bis(β-diketonato) Zr complexes CpZr(acac)2Cl (acac = acetylacetonato) (1) and Cp*Zr(acac)2Cl (2) can be synthesized by the reac-tion of Cp′ZrCl3(Cp′ = Cp or Cp*) with 2 equiv of lith-ium acetylacetonate. CpZr(acac)2Cl (1) can be quan-titatively prepared by treatment of Cp2ZrCl2 with ex-cess acetylacetone. The tris(β-diketonato) Zr com-plex CpZr(tfac)3 (tfac = trisfluoroacetylacetonato) (3) has been prepared by treatment of CpZrCl3 with so-dium trisfluoroacetylacetonate. The replacement of both chlorine atoms and one Cp group from zir-conocene dichloride by nonfluorinated diketone,acetylacetone,readily occurs at room temperature in triethylamine medium,offering the tris(β-diketonato) Zr complex CpZr(acac)3 (4). The complexes were characterized by 1H NMR spectroscopic methods. In addition,the molecular structures of complexes 3 and 4 have been determined by X-ray diffraction methods. When activated by excess methylaluminoxane (MAO),these complexes were active for ethylene polymerization,offering polyethylenes with high mo-lecular weights and narrow molecular weight distribu-tions. Complex 4 showed a very high ethylene po-lymerization activity of up to 7100 kg PE/mol Zr·h at 5 atm. Complexes 1 and 2 were also active for ethyl-ene/1-hexene copolymerization.     

δ13CSC values of the loess-paleosol sequence in Dali area, Shaanxi Province, China, and paleoenvironmental implications

The carbon isotopic ratios of carbonate in the two profiles of the Dali area were analyzed and some new understandings on the influencing factors of the δ^13Csc value of the Iocss-paleosol sequence and its paleoenvironmental implications were discussed preliminarily in this report. The δ^13Csc value of the Dali Ioess-paleasol sequence is synchronizing with the variance of magnetic susceptibility basically and the negative peaks of the δ^13Csc curves are corresponding to the different developmental periods of the paleosol. It is believed that the intervention of the CO2 produced by plants will cause the decrease of the δ^13Csc value, the amplitude of which may be relevant to the paleovegetation density and the ancient humidity. The relative biomass of C4 plants in the vegetation will affect the sublevel change of the δ^13Csc. Low δ^13Csc value by and large indicates the environmental conditions of the relatively abundant vegetation and humid climate. During the last 250000 years, the period with the sparsest vegetation and the most arid climate is the phase of the loess in L2 depositing and the period with the most abundant vegetation and the most humid climate is the last interglacial period. The δ^13Csc curves of Dali also show that the High Temperature and Large Precipitation Event of the Qinghai-Tibetan Plateau during 40-30 kaBP had affected the Central Shaanxi Plain with relatively humid climate, and had apparent influence on the local vegetation and humidity.     

Theoretical study on photophysical property of C60M（CO）5 （M=Cr,Mo and W）

Configurations of three η2 models of transition-metal [60]fullerene derivatives C60M（CO）5（M=Cr, Mo and W） have been optimized at B3LYP/LanL2DZ level. On the basis of the optimized geometrical structures, their electronic spectra and the frequency dependence of third-order nonlinear optical polarizabilities γ in different optical processes of third-harmonic generation （THG）, electric-field-induced second-harmonic generation （EFISHG） and degenerate four-wave mixing （DFWM） are calculated by using TDB3LYP model based on LanL2DZ level coupled with the SOS （sum-over-state） method. The obtained results show that their electronic spectra have a red shift compared with that of [60]fullerene and different transition-metal functional groups added to C60 cage may result in different spectrum properties. For the three studied species, （η^2-C60）Mo（CO）5 has the largest third-order nonlinear optical polarizability.     

Synthesis of [(C5H5Y (η2-PzMe2)(η-PzMe2)]2 and [Y(η2-PzMe2)2(η-PzMe2)(η-THF)]2 and the insertion of Me2SiO into the Y-N bond

3,5-Dimethylpyrazole (HPzMe2) reacted with (C5H5)3Y in THF to yield dinuclear complexes [(C5H5)Y-(η2-PzMe2)(μ-PzMe2)]2 (I) and [Y(η 2-PzMe2)2(μ-PzMe2)-(μ-THF)]2 (II), revealing a new method for synthesizing tris(pyrazolate) complexes of lanthanide metals. The X-ray crystallographic analysis showed that complex II crystallizes in space group P 1 , with unit cell dimensions a = 1.0798(1), b = 1.0818(1), c = 1.1313(1) nm, α= 76.914(2)°, β= 68.940(2)°, (R= 60.510(2)°, V = 1.0715(2) nm3, Z = 1. The final R factor is 0.0445. The investigation results showed that Me2SiO can only be inserted into the Y-N (bridging) bond of complex I to form [(C5H5)Y(η 2-PzMe2)(μ-OSiMe2 PzMe2)]2 (Ⅲ), but cannot be inserted into the Y-N (bridging) bond of complex Ⅱ due to the bulky crowding of the tetraple bridge structure.     

Synthesis,structure and catalytic behavior of yttrium complexes bearing a diaminobis（phenolate） ligand

Yttrium complexes stabilized by a diaminobis（phenolate） ligand were synthesized and their catalytic behavior was explored. Reaction of YCI3 with 1 equiv of LNa2 [L= Me2NCH2CH2N{CH2-（2-O-C6H2-^1Bu2-3,5）}2] gave the yttrium chloride LYCI（THF） （1） in 92% yield. Complex I can be used as starting material to prepare the yttrium amido derivative. Complex 1 reacted with 1 equiv of LiNPh2 in THF to afford the expected yttrium amido complex LYNPh2 （2） in high yield. Both of complexes 1 and 2 have been well detected by elemental analysis, NMR spectra and single-crystal X-ray analysis. It was found that complex 2 can efficiently initiate the ring-opening polymerization of L-lactide and ε-caprolactone, and a controlled manner is observed in the former case.     

Synthesis of monosubstituted N-arylamidines by divalent diaminobisphenolate ytterbium complex catalyzed addition of amines to nitriles

Divalent ytterbium complex YbL^（ONNO）（THF）2 （L^（ONNO）= Me2NCH2CH2N（CH2-2-O-3,5-C6H2（^1Bu）2）2） （1） has first been found to serve as a catalyst for addition of amines to nitriles to give monosubstituted N-arylamidine in moderate to good yields. The aromatic amines and nitriles showed better activity. The outcome of the addition reaction was greatly affected by the structure of divalent ytterbium complexes. The reaction mechanism was proposed and the benzonitrile-coordinated divalent ytterbium phenoxide Yb（OAr）2（C6H5CN）（THF）2 （Ar = 2,6-di^tBu-4-MeC6H3） was isolated as one of the intermediates.     

Research of Inclusion Complexation of 4,4＇-Thiodiphenol Effected by β-Cyclodextrin in Aqueous Solutions and the Effect on Photodegradation

The inclusion behavior of 4, 4＇ -Thiodiphenol （TDP）, a typical bisphenol and endocrine disruptor, reacts with β-cyclodextrin （β-CD） in aqueous solutions has been investigated by means of UV absorption spectrum and quantum-chemical calculation with Gaussian 98 software. The results show that the inclusion behavior of TDP is quite different in acidic solutions （pH 5.9） from that in alkaline solutions （pH 10.0）. This behavior difference is attributed to the different formula structures in aqueous solutions at acidic and alkaline pH values that are demonstrated by quantum- chemical modeling and calculation. TDP forms a 1 ： 1 fl-CD inclusion complex in aqueous solutions. The equiiibrium constant K was calculated to be 553.49 L/mol at pH 5.9 and 1 318.20 L/mol at pH 10.0 respectively for the inclusion complex reaction by using the modified Benesi-Heldbrand equation. After inclusion TDP＇s structure is changed especially at the inclusion part with the bond order becoming larger, which results in inhibitive photodegradation during direct photooxidation and H2O2 assisted photooxidation.     

Synthesis and characterization of N-aryloxo-functiona- lized β-ketoiminate rare-earth complexes and their catalytic activity for the polymerization of ε-caprolactone

The synthesis and characterization of dimeric rare-earth amides stabilized by a dianionic N-aryloxo functionalized ,8-ketoiminate ligand are described. Reactions of 4-（2-hydroxy-5-methyl-phenyl） imino-2-pentanone （LH2） with Ln[N（SiMe3）2]3（μ-Cl）Li（THF）3 in a 1：1 molar ratio in THF gave the dimeric rare-earth amido complexes [LLn{N（SiMe3）2}（THF）]2 [Ln = Nd （1）, Sm （2）, Yb （3）, Y （4）]. These complexes were well characterized, and the definitive molecular structures of complexes 3 and 4 were determined. It was found that complexes 1-4 can initiate the ring-opening polymerization of ε-caprolactone, and the ionic radii of the central metals have significant effect on the catalytic activity.     

Variation of soil Δδ13C values in Xifeng loess-paleosol sequence and its paleoenvironmental implication

The carbon isotopic compositions of soil organic matter （SOM） and total carbonate （TC） in Xifeng Ioess-paleosol sequence have been studied. The δ^13CsoM values vary from -23.8‰ to -20.2‰, which are higher in interglacial than in glacial stages. Contrary to δ^13Csoi values, the δ^13CTc values vary from -8.5‰ to -3.6‰ and are lower in interglacial than in glacial stages. The differences （△δ^13C） between the δ^13CsoM and δ^13CTc values vary from 14.1‰ to 19.4‰. Our results from the Xifeng loesspaleosol sequence indicate that the △δ^13C values represent the ratio of primary carbonate （PC） to secondary carbonate （SC）. The △δ^13C values were high in the loess stages, and the maximal PC-to-SC ratio can reach 6：4. But in the paleosol stages, the △δ^13C values were low, with a small proportion of PC. The △δ^13C values in Ioess-paleosol sequence also indicate the contributions of the dust to the loess sediment in the Chinese Loess Plateau because the dust contains the PC.     

Resonance-enhanced multiphoton ionization spectroscopy on the B′2Σ+ and B2Π states of NS

Resonance-enhanced multiphoton ionization （REMPI） spectra of N^32S and N^34S have been recorded in the range of 35700-40200 cm^-1. The radical was generated by a pulsed dc discharge of a mixture of SF6 and N2 under a supersonic free jet condition. All the 16 observed bands of N^32S radicals have been assigned, among which 12 bands belong to three transition progressions （v′=0-4, 0）, （v′=1-4, 1） and （v′=2-4, 2） from the X^2П ground state to the B′^2∑^＋ upper state and the rest correspond to （9, 0）, （10, 0）, （11, 0） and （12, 0） bands of B^2П-X^2П transition, respectively. Analysis of the rotationally resolved spectra yields exhaustive spectroscopic constants of both the X^2П ground state and the B′^2∑^＋ excited state. The electronic transition bands of the isotopic molecule N^34S have been rotationally analyzed for the first time and the rotational constants of the ground and upper states have been determined simultaneously.     

Theoretical study on photophysical property of C_(60)M(CO)_5 (M=Cr,Mo and W)

Configurations of three η2 models of transition-metal 60 fullerene derivatives C60M(CO)5(M=Cr,Mo and W) have been optimized at B3LYP/LanL2DZ level.On the basis of the optimized geometrical structures,their electronic spectra and the frequency dependence of third-order nonlinear optical polarizabilities γ in different optical processes of third-harmonic generation(THG),electric-field-induced sec-ond-harmonic generation(EFISHG) and degenerate four-wave mixing(DFWM) are calculated by using TDB3LYP model based on LanL2DZ level coupled with the SOS(sum-over-state) method.The obtained results show that their electronic spectra have a red shift compared with that of 60 fullerene and dif-ferent transition-metal functional groups added to C60 cage may result in different spectrum properties.For the three studied species,(η2-C60)Mo(CO)5 has the largest third-order nonlinear optical polarizability.     

Reactivity and structural characterization of divalent samarium aryloxide with diethylaluminum chloride

Reaction of (ArO)2Sm(THF)4 (ArO=2,6-ditert-butyl-4-methylphenolate) with Et2AICI in THF gives SmCI2 (1) and (ArO)AIEt2(THF) (2) via ligand exchange.Complex 1 reacts with cyclooctatetraene (C8H8) to give [(C8H8)SmCI(THF)2]2 (3). Crystal structural determinations show that complex 2 has a monomeric structure, the aluminum atom is coordinated by two carbon atoms and two oxygen atoms, to form a distorted tetrahedron. Complex 3 has a dimeric structure, the samarium atom is coordinated by a cyclooctatetraenyl ring, two chorine atoms and two oxygen atoms, the coordination number of the central metal is 9.     

Cyclic voltammetry,convolutive voltammetry,chronopotentiometry and disital simulation studies of [Pt（C≡C tol）2（dppm）2lr（CO）2]^＋PF^-6 complex

The electrochemical behaviour of the heterobimetallic complex [Pt（C≡C tol）2（dppm）2lr（CO）2]^＋PF^-6 was studied via cyclic voltammetry, convolutive voltammetry and chronopotentiometry at glassy carbon electrode in dichloromethane solution. The electrochemical parameters calculated from experimental data were tested and confirmed by matching the experimental cyclic voltammograms with the simulated data. It was found that convolutive voltammetry provided higher sensitivity, better resolution and more accurate method for determination of the electrochemical parameters than ordinary cyclic voltammetry.     

Synthesis, crystal structure and properties of binuclear manganese complex [(bipy)2Mn2(μ-O)(μ-Ac)2(H2O)2](ClO4)2

Binuclear manganese complex [(bipy)2Mn2(μ-O)(μ-Ac)2(H2O)2](ClO4)2 was synthesized by the reaction of MnAc3·2H2O with 2,2′- -bipyridine in the HAc-NaAc buffer (pH = 4.0). X-ray diffraction result for the single crystal shows that the crystal is monoclinic, space group C2/C, with a = 3.408 2(7), b = 0.864 4(2), c = 2.174 9(4) nm, β=105.2°,V =6.186(2) nm3, Z = 8. There are two very strong peaks of UV-Vis spectrum in the range of 400-600 nm, which are similar to those of Mn catalase and Mn ribonuleotide reductase extracted from organisms. Cyclic voltammogram shows that the complex in CH3CN undergoes quasi-reversible one-electron reduction and oxidation at E1/2=1.15 V.     

Different climatic controls of soil δ 13Corg in three mid-latitude regions of the Northern Hemisphere since the Last Glacial period

Paleoecological records of soil δ^13Corg from three regions in the middle latitudes of the Northern Hemisphere, including the Chinese Loess Plateau （CLP）, the Great Plains and adjacent areas of North America and northwestern Europe, showed different variations since the Last Glacial period. An attempt was made to evaluate the causes for the difference in δ^13Corg on the basis of the modern climatic data collected in these regions and of the modern C3 and C4 plant distributions. The analysis indicates that temperature, especially the growing season temperature, has a dominant control on the growth of C4 plants. When the mean annual or growing season temperatures are below the ＂threshold value＂, the growth of C4 plants is limited. When the temperature is above the ＂threshold value＂, C4 plants can grow under a wide range of precipitation. However, when the precipitation is high enough to favor the growth of trees, the proportions of C4 plants in local biomass will decline. The implicit control factor recovered by sedimentary records is consistent with the control factor on modern C3/C4 distribution. Pure C3 plants have been dominating the local biomass since the Last Glacial period in European loess region, mainly owing to the low local temperature. The increases in C4 plants from the late Pleistocene to the Holocene in the Chinese Loess Plateau, the Great Plains and adjacent areas, mainly reflect the influence of increasing temperature.     

Exotic structure of the third excited state in ^21Na

The probability of the last proton being out of the binding potential, P and the root-mean-square （rms） radius （〈r^2〉^1/2=of the third excited state in ^21Na are calculated by means of asymptotic normalization coefficient （ANC） method with the experimental date existing. The results are P=54.73% and 〈r^2〉^1/2=5.28 fm respectively. The P value and the contribution of the asymptotic part to the 〈r^2〉^1/2 are compared with those of several other low energy states in ^21Na. It is found that the valence particle in the third excited state has an obvious larger P than those of other states. The density distribution of the valence proton in this state is also compared with the nucleons in the nuclear core ^20Ne, and a far extended tail can be seen clearly. These results show that the third excited state in ^21Na is a proton halo state.     

Synthesis of 1 -（5 - nitro - 3 - phenylazophenyl）-triazene and Its Color Reaction with Cobalt

A new chromogenie reagent, 1 -(5-nitro- 3-benzopsendothiazde)- 3 -(4-phenylazophenyl)-triazene (NBPTPAPT) has been synthesized and used as a sensitive reagent for the spectrophotometric determination of cobalt.In the presence of Tween-80, the reagent with Co (Ⅱ)forms a yellow complex (1 2) in the buffer solution of Na2B4O7-NaOH at pH 10.54. The apparent molar range of 0-240 μg/ L for Co (Ⅱ) by dual-wavelength spectrophotometry. Trace cobalt in vitamin B12 and tea samples has been determined with satisfactory results.