Theoretical Study of Hydration Effects on the Selectivity of 18-Crown-6 Between K~＋ and Na~＋

A combination of molecular dynamics （MD） and density functional theory （DFT） calculations were used to study the hydration structures of K＋ and Na＋ ions under the confinement of 18-crown-6 in order to identify the role of water in the selectivity of 18-crown-6 towards K＋.The radial distribution functions,coordination num-bers,orientation structures and interaction energies were analyzed to investigate the hydration of K＋ and Na＋ in 18-crown-6/cation complexes.All calculations of K＋ and Na＋ in bulk water were also conducted for comparison.The simulation results show that the orientation distributions of the water molecules in the first coordination shell of K＋ are more sensitive to the confinement of 18-crown-6 than those of Na＋.It is more favorable to confine a K＋ in 18-crown-6 than a Na＋ in terms of interaction energy.Good agreement is obtained between MD results and DFT results.

[｛Pt_4(en)_4(NHCO^tBu)_4｝｛Tl(18-crown-6)｝_2](PF_6)_6的合成与晶体结构(英文)

The compound [｛Pt4(en)4(NHCOtBu)4｝｛Tl(18-crown-6)｝2](PF6)6 has been synthesized by a simple one-potmulticomponent reaction. Its structure was determined by X-ray single crystal diffraction analysis. The cation ofthe compound consists of one linearly arranged [Pt4(en)4(NHCOtBu)4]4+ chain and two [Tl(18-crown-6)]+ ions located atthe two ends of the platinum chain. The complex crystallizes in a triclinic P1 with a=1.060 5(1), b=1.252 3(1), c=2.015(2) nm, α=107.430(2)°, β=91.032(2)°, γ=101.910(2)°, V=2.489 6(4) nm3, Z=2, R1=0.074 4, wR2(I>2σ(I))=0.2225, S=1.062. CCDC: 294083.

Lanthanum(Ⅲ) sorption studies on poly[dibenzo-18-crown-6] and its separation from uranium(Ⅵ) and thorium(Ⅳ) in L-valine medium

The sorption study of La(Ⅲ) was carried out on poly[dibenzo-18-crown-6] and L-valine medium. The quantitative adsorption of La(Ⅲ) was found at 1×10-2 to 1×10-5 mol/L L-valine. The various eluting agents were found efficient eluents for La(Ⅲ). The capacity of crown polymer for La(Ⅲ) was found to be 0.43 ±0.01 mmol/g. The tolerance limit of various cations and anions for La(Ⅲ) was determined. La(Ⅲ) was quantitatively separated from other metal ions in binary as well as multicomponent mixtures. The study was extended to sequential separation of La(Ⅲ), U(VI) and Th(IV). The good separation yields were obtained and had good reproducibility (±2%). The method incorporated the determination of La(Ⅲ) in real sample. The method was simple, rapid and selective.

Synergistic Effect in Mixed Capillary Gas Chromatographic Stationap Phases Containing Heptakis(2,3,6-tri-o-pentyl)-β-cyclodextrin and Dibenzo-18-crown-6

used－silical capillary columns containing heptakis（2、3、6－tri－o－pentyl）-β-cyclodextrinand dibenzo-18-crown-6 were prepared．By studying the selectivity of mixed stationary phases forsome solute pairs.as well as comparing with the heptakis（2．3、6-tri-O-pentyl）-β-cyclodextrin and thedibenzo-18-crown-6 used as individual stationary phase、the synergistic effects were observed.These effects were affected by the column temperature．mixed ratio and linear velocity of carrier gas．

Synthesis and Crystal Structure of 3,3'-Dimethyl-dibenzo-18-crown-6

3,3′-Dimethyl-dibenzo-18-crown-6 was synthesized and characterized by elemental analysis, FT-IR, ^1H NMR, UV, MS spectra and X-ray single-crystal diffraction. It belongs to orthorhombic, space group Pna21 with a = 8.0790（18）, b = 16.780（4）, c = 15.222（3） .A, Z= 4, V= 2063.6（8） A3 Dc = 1.250 g/cm^3,μ = 0.090 mm^-1, F（000） = 832, R = 0.0474 and wR = 0.1103. According to structural analysis, the title compound possesses a boat-like configuration.

Fluorescence-quenching of Tryptophan Ion-18-crown-6 Complex——A Different Observation from Its Neutral Counterpart

It is well-known that primary amines form inclusive complexes with crown ethers. This kind of noncovalently inclusive complexes, exemplified tryptophan complex with 18-crown-6, was studied by combination of two experimental methods, fluorimetry and mass spectrometry, with theoretical calculation. Fluorescence intensity of tryptophan in the absence and the presence of 18-crown-6 in aqueous HAc-NaAc buffer solution at pH=3.73 has been studied by fluorometry. The fuorescence intensity decreases significantly with increasing the concentration of 18-crown-6. The association constant K for the 1：1 complex of tryptophan ion-18-crown-6 was determined by means of fuorimetry. Mass spectrometric study of the complex gives direct evidence of the complex in the gas phase whose structure and binding energy are properly predicted by ab initio calculation.

{[K.18-Crown-6]Br_3}_n:A tribromide catalyst for the catalytic protection of amines and alcohols

{[K.18-Crown-6]Br3}n,a unique tribromide-type catalyst,was utilized for the N-boc protection of amines and trimethylsilylation(TMS)and tetrahydropyranylation(THP)of alcohols.The method is general for the preparation of N-boc derivatives of aliphatic(acyclic and cyclic)and aromatic,and primary and secondary amines and also various TMS-ethers and THP-ethers.The simple separation of the catalyst from the product is one of the many advantages of this method.

Synthesis and Crystal Structure of a Sandwiched Trinuclear Complex [Tl_2(18-Crown-6)_2Pt(CN)_4]·2H_2O

The trinuclear complex bis（18-crown-6）thallium tetracyanoplatinate [Tl2（1 8-crown- 6）2Pt（CN）4]·2H2O was prepared and its structure was determined by X-ray diffraction analysis. The compound （C28H52N4O14PtTl2, Mr = 1272.57） crystallizes in monoclinic, space group P21/n with a = 10.5180（10）, b = 8.6162（8）, c = 21.118（2） A, β= 92.577（2）°, V= 1911.9（3） A^3, Z = 2, Dc = 2.211 g/cm^3, F（000） = 1200,μ= 12.123 mm^-1, R = 0.0181 and wR = 0.0427. The linearly arranged three metals are sandwiched by two 18-crown-6 molecules.

Bibracchial Lariat Ethers(Ⅰ)——The Synthesis and Crystal Structure of the N,N'-bis(2-Methoxy-1-Naphthylmethyl)-4,13-Diaza-18-Crown-6 Sodium Iodide Complex

Diaza Crown ethers are versatile complexing reagents, their complexing abilities are dramatically modified by the electron donating atoms on substituents attached to the nitrogen if they can give a three-dimensional cavity as in cryptates. Hence the synthesis and characterization of bibracchial lariat ethers (BIBLES) have received much attention. In the preparation of new BIBLES, a complex Ⅱ was unexpectedly obtained.

REGIOSELECTIVE OXIDATION OF KETONE BY AN OXIDATIVE REAGENT SYSTEM KH/O_2/18-CROWN-6/THF:APPLICATION TO SYNTHESIS OF VARIOUS LACTONES

the regioselectivity in the oxidation of different types of ketone compounds 1--6 with an oxidative reagent system,KH/O_2/18- Crown-6/THF is described.From these oxidative products,the various lactones have been prepared.

CdI₂Extraction with 18-Crown-6 Ether into Various Diluents: Classification of Extracted Cd(II) Complex Ions Based on the HSAB Principle

CdI2 in water was extracted with 18-crown-6 ether (L) into 10 diluents at 298 K. The following equilibrium constants were determined or evaluated: some extraction constants (Kex/mol-3·dm9 & Kex,ip/mol-2·dm6 for CdLI2, Kex±/mol-2·dm6 for CdLI+ with I-, & Kex2±/mol-1·dm3 for CdL2+ with 2I-), conditional distribution constants (KD,I for I-, KD,CdLI for CdLI+, & KD,CdL for CdL2+) between the two phases, and an ion-pair formation constant (K1,org/mol-1·dm3) for CdLI+ and that (K2,org/mol-1·dm3) for CdLI2 in the organic (org) phases. Using the K1,org and K2,org values, acidities of the complex ions, CdL2+ and CdLA+ (A- = I-, Br-, & Cl-), in the 11 diluents were classified by applying the HSAB rule. Especially, the CdLA+ ions were classified as the soft acids in 9 diluents. Also, molar volumes (Vj/cm3·mol-1) of j = CdLI2 and CdL2+ were determined with the regular-solution-theory plot of logKex,ip vs. logKD,L and its pseudo-plot of logKD,CdL, respectively. Here, KD,L denotes the distribution constant of L between the two phases. So, sizes among CdLA2 and CdL2+ were compared by using the Vj values. Additionally, some distribution equilibrium potentials (dep/V) between the water and org bulk phases were topically calculated from an equation of KD,I with KSD,I, where the symbol KSD,I shows a standard distribution constant of I- at dep = 0 V for a given diluent.

Chromatographic separation of Be（Ⅱ） from Mg（Ⅱ）, Ca（Ⅱ）, Sr（Ⅱ） and Ba（Ⅱ） using poly[dibenzo-18-crown-6] and L-arginine

A simple and selective method for the separation of Be（Ⅱ） was developed using poly[dibenzo-18-crown-6] as a stationary phase in column chromatography. The study was carried out in L-arginine medium. 1.0-8.0 M HCl and CH3COOH, 0.5-8.0 M HBr, HClO4 and H2SO4, 0.2-1.0 M EDTA and 0.02-0.12 M ammonium oxalate were found to be an efficient eluents for Be（Ⅱ）. The capacity of polymer was 0.554-0.01 mmol/g of crown polymer. The tolerance limit of various cations and anions were reported. Be（Ⅱ） was quantitatively separated from Mg（Ⅱ）, Ca（Ⅱ）, Sr（Ⅱ） and Ba（Ⅱ）. The selective separation of Be（Ⅱ） was possible from multicomponent mixtures. The method was extended to determine Be（Ⅱ） from geological samples. Method was simple, rapid and selective having good reproducibility （approximately4-2%）.

One-dimensional Chain Crown Ether Complexes Synthesis and Crystal Structure of ([K(DB18-crown-6)]_(2)(CH_(3)CN))[Pt(SCN)_(4)]

The complexe{[K(DB18-crown-6)]_(2)(CH_(3)CN)}[Pt(SCN)_(4)]was synthesized and characterized by elemental analysis,IR spectrum and X-ray diffraction analysis.The complexe belongs to monoclinic,space group c2/c with cell dimensions,a=2.5904(8),6=1.3653(4),c-1.84706(6)nm,β=123.811(4)°,V=5-339(3)nm^(3),Z=4,.Dcalcd=l.577 g/cm^(3),F(000)=2552,R_(1)=0.051 l,wR_(2)=0.1411.The complexe shows one-dimensional chain of{[K(DB18-crown-6)]+complex cation and[Pt(SCN),i]2-complex anion bridged by N atom of CHaCN moleculer between two[K(DB18-crown-6)]_(2)[Pt(SCN)_(4)]groups respectively.

CRYSTAL STRUCTURE OF DISODIUM DIAZA-18-CROWN-6-N, N'-DIACETATE PENTAHYDRATE

The title compound was prepared from the reaction of diaza-18-crown-6 and sodium chloroacetate in aqueous solution and crystallized from ethanol solution by standing for a long time. The complex [Na(C16H28N2O8)·Na(H2O)5]2Cl-·2H2O+·H2O (Mr = 655. 45) crystalizes in triclinic system,space group P1 with a = 9. 623(2),b = 10. 902(3),c=15. 867(3) A ;α= 104. 63(2),β= 105. 42(2),γ=99. 88(2)°,V = 1502. 3A3,Dc=1. 09gcm-3,Z = 2,F(000) = 516,final R=0. 075 for 3218 observed reflections. The donor atoms O(4) ,O(7) ,O(13) ,O(16) ,N(1) and N(10) from the crown ether as well as the oxygen atoms O(21) and O(26) from two car boxy lato anions are coordinated cooperatively to the Na(1)+ ion to form crown ether solvated cation in a tetragonal prismatic geometry. The O(22) of one carboxylato anion, which does not coordinate the Na(1) + ion,interacts with the Na(2)+ion together with the oxygen atoms of five water molecules to form a hydrated cation having a deformed octahedral configuration.

CRYSTAL STRUCTURE OF N, N' -BIS ( 2-METHOXY-1-NAPH-THYLMETHYL)-4,13-DIAZA-18-CROWN-6 POTASSIUM IODIDE

Crystal of N , N'-bis(2-methoxy-l-naphthylmethyl)-4,13-diaza-18-crown-6 potassium iodide diethanol solvate[(C36H46N2O6)K]+I- · 2C2H5OH (Mr = 860. 47) is orthorhombic with space group Pcab, a = 17. 531(5), 6 = 21. 149(8), c = 23. 060(4)(?). F=8550. 00(?)3, Z = 8, F(000) = 3167. 64 and Dc=1. 337g/ cm3, μ = 8. 74cm-1, R = 0. 057. In the title complex, the donor atoms of the macro-ring are arranged in a twisted boat conformation. The potassium ion is octa-coordi-nated with four oxygen and two nitrogen atoms of the macro-ring and two oxygen atoms of the two side arms at the same side to form a distorted hexagonal bipyramid.

Crystal Structures of N, N'-Bis (4-chlorophenyl)-1, 10-diaza-18-crown-6 and Its Complex with Ba (SCN)_2

The title compounds,C_(24)H_(32)Cl_2,N_2O_4(I)and C_(26)H_(32)BaCl_2N_4O_4S_2 (Ⅱ)have been synthesized and crystal structures determined. The crystallographic data are as follows: (I)M_r=483. 44,orthorhombic, space group P2_12_12_1,a= 4. 852 (1), b= 11. 989(2), c=41. 231 (8) A, V=2398. 7(8) A￣3, Z=4, μ(MoKa)=3. 07 cm￣(-1), D_c=1. 338 g/cm￣3, F(000)=960, R=0. 0678, R_w=0. 0514. (Ⅱ) M_r=736.93, monoclinic, space group P2_1/c, a=8. 801 (2), b=11. 653(9) , c=15. 756(6) A,β=105. 96(3)°, V=1553. 7(14) A￣3, Z= 2, μ(MoKa)=16. 58 cm￣(-1), D_c=1. 575 g/ cm￣3, F(000)= 740. In compound Ⅱ, the Ba cation is coordinated by four oxygen atoms, two mitrogen atoms of diazo-18-crown-6 and two nitrogen atoms from SCN￣- to form a distorted D_(6h) geometry with the Ba￣(2+) at the center of crystallographic symmetry.

外圆磨削18CrNiMo7-6力模型及表面完整性研究

为了准确和有效地控制磨削参数对磨削力及表面完整性的影响,通过解析法,以磨粒与材料间的塑性变形、压痕理论以及剪切应变效应为理论依据,建立了三阶段的磨削力理论模型。选定棕刚玉砂轮进行磨削试验,探究了磨削参数对磨削力的影响以及磨削参数和磨削力对表面完整性的影响,通过外圆横向磨削正交试验获得了外圆磨削最优工艺参数。结果表明,外圆磨削力模型法向磨削力和切向磨削力的预测平均误差分别为5.56%和7.08%;砂轮径向进给速度f_(r)对磨削力的影响最大,磨削宽度b次之,工件转速n_(w)和砂轮粒度的影响较小;f_(r)和b对残余应力的影响较大,砂轮粒度对表面粗糙度的影响最大;随着磨削力的增大,表面粗糙度值一直增大,残余应力先减小后增大,沿深度方向残余应力最大值先增大后减小,在试验所取参数条件下,影响残余应力的深度分布范围基本在20~40μm;最优工艺参数组合如下:f_(r)=0.15 mm/min,n_(w)=120 r/min,b=10 mm,砂轮粒度80。

一种4 GHz瞬时带宽的6~18 GHz超宽带T/R组件设计

针对现代电子对抗设备的大瞬时带宽要求,文中设计了一种瞬时带宽4 GHz的6~18 GHz超宽带T/R组件。采用砖块式多芯片组件(Multi-Chip Module,MCM)和超宽带信号传输等技术实现了T/R组件高集成、小型化和模块化的要求。对T/R组件组成构架、收发通道指标预算、宽带信号传输特性仿真和电磁兼容性设计进行了详细描述。测试结果显示,T/R组件在12 GHz工作带宽内具有良好的性能,发射功率大于35 dBm,接收增益大于20 dB,噪声系数小于5 dB,延时总量达762 ps。

18CrNiMo7-6齿轮钢的热压缩变形行为及显微组织演变

采用热模拟方法研究了18CrNiMo7-6齿轮钢在变形温度900~1150℃、应变速率0.01~5 s-1条件下的热压缩变形行为;建立了基于Arrhenius模型的全应变本构方程,采用该方程对流变应力曲线进行预测;根据动态材料模型绘制热加工图,并结合热加工图系统地研究显微组织演变特征。结果表明:试验钢的峰值应力随应变速率的增加或变形温度的降低而增大,动态回复和动态再结晶是热变形过程中的主要软化机制;采用建立的全应变本构方程预测得到流变应力曲线与试验结果基本吻合,预测真应力与试验结果的相对误差小于4.715%,说明该模型可以精确地模拟18CrNiMo7-6齿轮钢的热压缩变形行为。试验钢的适合热加工工艺参数为变形温度1050~1150℃、应变速率0.1~1 s^(-1),此时组织为均匀细小的再结晶晶粒,晶粒尺寸在5~15μm。随着变形温度的升高或应变速率的降低,原始奥氏体晶粒不断被动态再结晶晶粒取代,且动态再结晶程度和再结晶晶粒尺寸增大。

车削工艺参数对18CrNiMo7-6钢切削力及表面粗糙度的影响

为了探究车削工艺参数对18CrNiMo7-6钢标准疲劳试样不同位置的切削力和表面粗糙度的影响,采用CAK4085型数控车床对主轴转速n、背吃刀量a_(p)和进给速度v_(f)三个工艺参数进行单因素试验研究。结果表明:对于标准试样的圆弧段和标距段,切削用量对切削力和表面粗糙度的影响规律相同;背吃刀量a_(p)对切削力影响最大,进给速度v_(f)对切削力的影响次之,主轴转速n对切削力的影响最小;拟合的三个切削力分量指数公式中,主切削力的拟合误差为5.25%,背向力的拟合误差为2.29%,相对误差较小。结果显示,影响表面粗糙度Ra的最大因素为进给速度,Ra随v_(f)的增大而增大,圆弧切入段的表面粗糙度Ra比切出段高。综合考虑疲劳试样较好的加工工艺参数为:n=1000r/min,v_(f)=80mm/min,a_(p)=0.3mm。本研究结果可为疲劳试样的车削加工工艺制定提供参考依据。