四齿四棱草根部环肽化合物的分离及鉴定

通过正相和反相硅胶柱层析,从四齿四棱草根部的乙醇提取物中分离纯化出4个环肽化合物,经波谱分析等鉴定了其结构,其中2个新化合物的结构分别为cyclo(-N-Pro¹-Pro²-Phe¹-Phe²-Leu¹-Ser-Thr-Leu²-CO)(1,四棱草肽C)和cyclo(-N-Pro¹-Pro²-His-Gly-Val-Asn-Ile-Trp-CO)(2,四棱草肽D).     

n—GaAs（100）,Si（111）表面修饰卟啉分子的光致界面电荷转移…

利用表面光电压谱研究了四碘化四－（４－三甲胺苯基）卟啉（ＴＴＭＡＰＰＩＨ２）修饰ｎ－ＧａＡＳ（１００）和ｎ－Ｓｉ（１１１）半导体表面的光致界面电荷转移特性。结果表明，ｎ－ＧａＡｓ（１００）表面修饰ＴＴＭＡＰＰＩＨ２分子的光致界面电荷转移效率远比ｎ－Ｓｉ（１１１）表面修饰的高，并且发现在该卟啉分子的非吸收区也有明显的光致界面电荷转移现象，而与ｎ－Ｓｉ（１１１）间则没有这种转移特性。用电化学测量和ＵＶ     

四甲基碳酸氢铵的合成研究

四甲基氢氧化铵(TMAH)是一种有机碱,因其在较低的加热温度下即可分解变为气体[1,2],作为催化剂来应用时不残留,所以在工业催化、科研及电子工业领域都有着极为广泛的应用.     

高比表面积二硫化钼的制备及其对喹啉选择加氢反应的催化性能

通过四硫代钼酸铵与四甲基氯化铵的甲基取代反应合成了四甲基四硫代钼酸铵,并通过四甲基四硫代钼酸铵热解制备了具有较高比表面积的二硫化钼. 结果显示,由四甲基四硫代钼酸铵热解可以得到比表面积为108 m2/g以上的二硫化钼,而由四硫代钼酸铵热解得到的二硫化钼样品的比表面积仅为16 m2/g. 由四甲基四硫代钼酸铵热解得到的二硫化钼样品具有较低的结晶度,样品具有像干酪样状的半球形和卵形孔穴排列的特点,其孔径尺寸为4～12 nm. 四甲基四硫代钼酸铵热解制备的二硫化钼在喹啉选择加氢中显示出较高的催化活性和选择性.     

四溴四苯基卟啉及其金属配合物的电子结构和四溴四苯基卟啉Ni(Ⅱ)的晶体结构

本文合成了7,8,17,18-四溴-5,10,15,20-四苯基-21,23(H)-卟啉(H_2TPPBr_4)及其金属配合物MTPPBr_4[M=Cu(Ⅱ),Ni(Ⅱ),Co(Ⅱ)和Zn(Ⅱ)],测定了它们的可见紫外光谱和循环伏安,用四轨道模型(Four Orbital Model)计算了MTPPBr_4的相对前线轨道,并解释了配合物的可见紫外光谱及电化学性质.测定了NiTPPBr_4的晶体结构,晶体属单斜晶系,空间群为C2/c,a=2.6077(7),b=1.0414(4),c=1.9312(3)nm,β=137.1(7)°,Z=4,最后偏离因子R=0.067,晶体结构直接证明了卟啉亲电溴化反应具有区域选择性,四个溴分布在相对两个吡咯环上.     

四氮大环席夫碱配合物研究（Ⅱ）：1,3：6,7：10,11：14,15—四苯并—1,4,9,12四 …

自从1968年Jager合成第一个四氮[14]大环席夫碱配合物以来[1],四氮大环席夫碱配合物的研究受到人们很大的关注.这类配体与天然卟啉环非常相似,对小分子如O2、CO、CO2等均有较强的键联能力,对于研究生物体内的金属蛋白质及酶有着重要的意义[2,3].].另外,这类配合物具有作为催化剂、萃取剂、导体等潜在的应用价值.     

化学师范生“四层次四维度”教师技能竞赛体系研究

为进一步激发师范生的学习兴趣、促进教师职业技能的生成,依托竞赛激励机制,构建了“四层次四维度”竞赛实践体系,即先整合教师技能为“基础技能、教学技能、综合技能、学科专项技能”4个维度技能,再通过“院级、校级、省级、国家级”4个层次进行竞赛实践,这有助于提升师范生的教学能力、实践能力和创新能力。     

电解四甲基碳酸氢铵制备四甲基氢氧化铵

以四甲基碳酸氢铵为原料,钛基二氧化钌为阳极,不锈钢为阴极,在H型电解槽中恒电流密度电解合成四甲基氢氧化铵,主要考察了合成工艺中离子交换膜种类、原料浓度、电解温度和电流密度对电流效率的影响。研究结果表明,当采用旭化成F4403D为阳离子交换膜,在四甲基碳酸氢铵浓度为1.41mol·L-1,电解液温度40℃～60℃,电流密度792A.m-2的条件下,电流效率可达83.5%。     

以四硝基铝酞菁为荧光探针测定葡萄糖的荧光分析新方法

建立以四硝基铝酞菁为荧光探针测定葡萄糖的荧光分析新方法。方法基于四硝基铝酞菁苯环上的硝基与葡萄糖发生还原反应,形成铝酞菁的氨基化产物;氨基化铝酞菁具有红区激发和发射的特性,在强酸性介质中可发射较强荧光;体系的荧光强度和葡萄糖的含量呈良好的线性关系,并具有较好的准确性和稳定性。方法用于测定发酵样品中的还原糖,结果满意。     

水溶液中新型四氮杂二乙酸基取代大环及其镧系配合物的热力学研究

The protonation constants of the macrocycle H₂L¹ (c-meso-2,4,4,11,13,13-hexamethyl-1,5,10,14-tetraazacyclooctadecane-N,N＂-diacetic acids)were determined potentiometricly and by computer fitting in 0.5 mol·L^-1 KNO₃ solution at 25±0.1℃, 30±0.1℃ and 40±0.1℃. The stability constants of the 1∶1 complexes of H₂L¹ with La³⁺, Nd³⁺, Sm³⁺, Eu³⁺, Gd³⁺, Dy³⁺, Yb³⁺ were determined by the same method at 40±0.1℃. The ΔH、 ΔS and ΔG of the coodination reaction of H₂L¹ with H⁺ in the aqueous solution were found.     

Tuning facial-meridional isomerisation in monometallic nine-co-ordinate lanthanide complexes with unsymmetrical tridentate ligands

The unsymmetrical tridentate benzimidazole-pyridine-carboxamide units in ligands L1-L4 react with trivalent lanthanides, Ln(III), to give the nine-co-ordinate triple-helical complexes [Ln(Li)3]3+ (i = 1-4) existing as mixtures of C3-symmetrical facial and C1-symmetrical meridional isomers. Although the beta13 formation constants are 3-4 orders of magnitude smaller for these complexes than those found for the D3-symmetrical analogues [Ln(Li)3]3+ (i = 5-6) with symmetrical ligands, their formation at the millimolar scale is quantitative and the emission quantum yield of [Eu(L2)3]3+ is significantly larger. The fac-[Ln(Li)3]3+ <--> mer-[Ln(Li)3]3+ (i = 1-4) isomerisation process in acetonitrile is slow enough for Ln = Lu(III) to be quantified by 1H NMR below room temperature. The separation of enthalpic and entropic contributions shows that the distribution of the facial and meridional isomers can be tuned by the judicious peripheral substitution of the ligands affecting the interstrand interactions. Molecular mechanics (MM) calculations suggest that one supplementary interstrand pi-stacking interaction stabilises the meridional isomers, while the facial isomers benefit from more favourable electrostatic contributions. As a result of the mixture of facial and meridional isomers in solution, we were unable to obtain single crystals of 1:3 complexes, but the X-ray crystal structures of their nine-co-ordinate precursors [Eu(L1)2(CF3SO3)2(H2O)](CF3SO3)(C3H5N)2(H2O) (6, C45H54EuF9N10O13S3, monoclinic, P2(1)/c, Z = 4) and [Eu(L4)2(CF3SO3)2(H2O)](CF3SO3)(C4H4O)(1.5) (7, C51H66EuF9N8O(15.5)S3, triclinic, P1, Z = 2) provide crucial structural information on the binding mode of the unsymmetrical tridentate ligands.     

Homotrinuclear lanthanide(III) arrays: assembly of and conversion from mononuclear and dinuclear units

The reactions of potentially hexadentate H2bbpen (N,N'-bis(2-hydroxybenzyl)-N,N'-bis(2-pyridylmethyl)-ethylenediamine, H2L1), H2(Cl)bbpen (N,N'-bis(5-chloro-2-hydroxybenzyl)-N,N'-bis(2-pyridylmethyl)ethylenediamine, H2L2), and H2(Br)bbpen (N,N'-bis(5-bromo-2-hydroxybenzyl)-N,N'-bis(2-pyridylmethyl)ethylenediamine, H2L3) with Ln(III) ions in the presence of a base in methanol resulted in three types of complexes: neutral mononuclear ([LnL(NO3)]), monocationic dinuclear ([Ln2L2(NO3)]+), and monocationic trinuclear ([Ln3L2(X)n(CH3OH)]+), where X = bridging (CH3COO-) and bidentate ligands (NO3-, CH3COO-, ClO4-) and n is 4. The formation of a complex depends on the base (hydroxide or acetate) and the size of the respective Ln(III) ion. All complexes were characterized by infrared spectroscopy, mass spectrometry, and elemental analyses; in some cases, X-ray diffraction studies were also performed. The structures of the neutral mononuclear [Yb(L1)(NO3)], dinuclear [Pr2(L1)2(NO3)(H2O)]NO3.CH3OH and [Gd2(L1)2(NO3)]NO3.CH3OH.3H2O, and trinuclear [Gd3(L3)2(CH3COO)4(CH3OH)]ClO4.5CH3OH and [Sm3(L1)2(CH3COO)2(NO3)2(CH3OH)]NO3.CH3OH.3.65H2O were solved by X-ray crystallography. The [LnL(NO3)] or [Ln2L2(NO3)]+ complexes could be converted to [Ln3L2(X)n(CH3OH)]+ complexes by the addition of 1 equiv of a Ln(III) salt and 2-3 equiv of sodium acetate in methanol. The trinuclear complexes were found to be the most stable of the three types, which was evident from the presence of the intact monocationic high molecular weight parent peaks ([Ln3L2(X)n]+) in the mass spectra of all the trinuclear complexes and from the ease of conversion from the mononuclear or dinuclear to the trinuclear species. The incompatibility of the ligand denticity with the coordination requirements of the Ln(III) ions was proven to be a useful tool in the construction of multinuclear Ln(III) metal ion arrays.     

以氧、氮为配位原子的某些铅(Ⅱ)混合配体化合物的稳定性研究(Ⅱ)

前文报告了Pb(Ⅱ)-en-Ox1:1:1型混合配合物的稳定性。虽然稳定常数(logβ)高于统计效应的期望值,但其ΔlogK却是较大的负值。一些共轭氮杂环碱如2,2′-联吡啶、邻二氮菲等氮氮型配体,能与氧氧型配体协同作用,同过渡金属形成相当稳定的三元混合配合物,其ΔlogK可为正值,即共轭氮杂环碱在金属上的配位可促进氧氧型配体的配位。但对于非过渡金属,是否也有类似的情况则尚无定论。     

Heterobimetallic Zn(II)-Ln(III) phenylene-bridged schiff base complexes, computational studies, and evidence for singlet energy transfer as the main pathway in the sensitization of near-infrared Nd3+ luminescence

A series of 3d-4f heterobimetallic phenylene-bridged Schiff base complexes of the general formula [Zn(mu-L1)Ln(NO3)3(S)n] [Ln = La (1), Nd (2), Gd (3), Er (4), Yb (5); S = H(2)O, EtOH; n = 1, 2; H2L1 = N,N'-bis(3-methoxysalicylidene)phenylene-1,2-diamine] and [Zn(mu-L2)Ln(NO3)3(H2O)n] [Ln = La (6), Nd (7), Gd (8), Er (9), Yb (10); n = 1, 2; H(2)L(2) = N,N'-bis(3-methoxy-5-p-tolylsalicylidene)phenylene-1,2-diamine] were synthesized and characterized. Complexes 1, 2, 4, and 7 were structurally characterized by X-ray crystallography. At room temperature in CH(3)CN, both neodymium(III) (2 and 7) and ytterbium(III) (5 and 10) complexes also exhibited, in addition to the ligand-centered emission in the UV-vis region, their lanthanide(III) ion emission in the near-infrared (NIR) region. The photophysical properties of the zinc(II) phenylene-bridged complexes (ZnL1 and ZnL2) were measured and compared with those of the corresponding zinc(II) ethylene-bridged complexes (ZnL3 and ZnL4). Our results revealed that, at 77 K, both ligand-centered triplet (3LC) and singlet (1LC) states existed for the ethylene-bridged complexes (ZnL3 and ZnL4), whereas only the (1)LC state was detected for the phenylene-bridged complexes (ZnL1 and ZnL2). NIR sensitization studies of [Zn(mu-L')Nd(NO3)3(H2O)n] (L' = L1-L4) complexes further showed that Nd3+ sensitization took place via the 3LC and 1LC states when the spacer between the imine groups of the Schiff base ligand was an ethylene and a phenylene unit, respectively. Ab initio calculations show that the observed differences can be attributed to the difference in the molecular vibrational properties and electron densities of the electronic states between the ethylene- and phenylene-bridged complexes.     

Multiple-path dissociation mechanism for mono- and dinuclear tris(hydroxamato)iron(III) complexes with dihydroxamic acid ligands in aqueous solution

Linear synthetic dihydroxamic acids ([CH3N(OH)C=O)]2(CH2)n; H2Ln) with short (n = 2) and long (n = 8) hydrocarbon-connecting chains form mono- and dinuclear complexes with Fe(III) in aqueous solution. At conditions where the formation of Fe2(Ln)3 is favored, complexes with each of the two ligand systems undergo [H+]-induced ligand dissociation processes via multiple sequential and parallel paths, some of which are common and some of which are different for the two ligands. The pH jump induced ligand dissociation proceeds in two major stages (I and II) where each stage is shown to be comprised of multiple components (Ix, where x = 1-3 for L2 and L8, and IIy, where y = 1-3 for L2 and y = 1-4 for L8). A reaction scheme consistent with kinetic and independent ESI-MS data is proposed that includes the tris-chelated complexes (coordinated H2O omitted for clarity) (Fe2(Ln)3, Fe2(L2)2(L2H)2, Fe(LnH)3, Fe(L8)(L8H)), bis-chelated complexes (Fe2(Ln)2(2+), Fe(LnH)2+, Fe(L8)+), and monochelated complexes (Fe(LnH)2+). Analysis of kinetic data for ligand dissociation from Fe2(Ln)(LnH)3+ (n = 2, 4, 6, 8) allows us to estimate the dielectric constant at the reactive dinuclear Fe(III) site. The existence of multiple ligand dissociation paths for the dihydroxamic acid complexes of Fe(III) is a feature that distinguishes these systems from their bidentate monohydroxamic acid and hexadentate trihydroxamic acid counterparts and may be a reason for the biosynthesis of dihydroxamic acid siderophores, despite higher environmental molar concentrations necessary to completely chelate Fe(III).     

Influence of Schiff base and lanthanide metals on the synthesis, stability, and reactivity of monoamido lanthanide complexes bearing two Schiff bases

The monoamido lanthanide complexes stabilized by Schiff base ligand L(2)LnN(TMS)(2) (L = 3,5-Bu(t)(2)-2-(O)-C(6)H(2)CH═N-8-C(9)H(6)N, Ln = Yb (1), Y (2), Eu (3), Nd (4), and La (5)) were synthesized in good yields by the reactions of Ln[N(TMS)(2)](3) with 1.8 equiv of HL in hexane at room temperature. It was found that the stability of 1-5 depends greatly on the size of the lanthanide metals with the increasing trend of Yb ≈ Y < Nd < La. The amine elimination of Ln[N(TMS)(2)](3) with the bulky bidentate Schiff base HL' (L' = 3,5-Bu(t)(2)-2-(O)-C(6)H(2)CH═N-2,6-Pr(i)(2)-C(6)H(3)) afforded the monoamido lanthanide complexes L'(2)LnN(TMS)(2) (Ln = Yb (9), Y (10), Nd (11), and La (12)). While the amine elimination with the less bulky Schiff base HL' (L' = 3,5-Bu(t)(2)-2-(O)-C(6)H(2)CH═N-2,6-Me(2)-C(6)H(3)) yielded the desired monoamido complexes with the small metals of Y and Yb, L'(2)LnN(TMS)(2) (Ln = Yb (13) and Y (14)), and the more stable tris-Schiff base complexes with the large metals of La and Nd, yielded L'(3)Ln as the only product. Complexes 1-14 were fully characterized including X-ray crystal structural analysis. Complexes 1-5, 10, and 14 can serve as the efficient catalysts for addition of amines to carbodiimides, and the catalytic activity is greatly affected by the lanthanide metals with the active sequence of Yb < Y < Eu ≈ Nd ≈ La.     

Synthesis and reactivity of rare earth metal alkyl complexes stabilized by anilido phosphinimine and amino phosphine ligands

Anilido phosphinimino ancillary ligand H(2)L(1) reacted with one equivalent of rare earth metal trialkyl [Ln{CH(2)Si(CH(3))(3)}(3)(thf)(2)] (Ln=Y, Lu) to afford rare earth metal monoalkyl complexes [L(1)LnCH(2)Si(CH(3))(3)(THF)] (1 a: Ln=Y; 1 b: Ln=Lu). In this process, deprotonation of H(2)L(1) by one metal alkyl species was followed by intramolecular C--H activation of the phenyl group of the phosphine moiety to generate dianionic species L(1) with release of two equivalnts of tetramethylsilane. Ligand L(1) coordinates to Ln(3+) ions in a rare C,N,N tridentate mode. Complex l a reacted readily with two equivalents of 2,6-diisopropylaniline to give the corresponding bis-amido complex [(HL(1))LnY(NHC(6)H(3)iPr(2)-2,6)(2)] (2) selectively, that is, the C--H activation of the phenyl group is reversible. When 1 a was exposed to moisture, the hydrolyzed dimeric complex [{(HL(1))Y(OH)}(2)](OH)(2) (3) was isolated. Treatment of [Ln{CH(2)Si(CH(3))(3)}(3)(thf)(2)] with amino phosphine ligands HL(2-R) gave stable rare earth metal bis-alkyl complexes [(L(2-R))Ln{CH(2)Si(CH(3))(3)}(2)(thf)] (4 a: Ln=Y, R=Me; 4 b: Ln=Lu, R=Me; 4 c: Ln=Y, R=iPr; 4 d: Ln=Y, R=iPr) in high yields. No proton abstraction from the ligand was observed. Amination of 4 a and 4 c with 2,6-diisopropylaniline afforded the bis-amido counterparts [(L(2-R))Y(NHC(6)H(3)iPr(2)-2,6)(2)(thf)] (5 a: R=Me; 5 b: R=iPr). Complexes 1 a,b and 4 a-d initiated the ring-opening polymerization of d,l-lactide with high activity to give atactic polylactides.     

Rare earth metal complexes bearing thiophene-amido ligand: synthesis and structural characterization

2,6-diisopropyl-N-(2-thienylmethyl)aniline (H2L) has been prepared, which reacted with equimolar rare earth metal tris(alkyl)s, Ln(CH2SiMe3)3(THF)2, afforded rare earth metal mono(alkyl) complexes, LLn(CH2SiMe3)(THF)3 (:Ln=Lu; :Ln=Y). In this process, H2L was deprotonated by one metal alkyl species followed by intramolecular C-H activation of the thiophene ring to generate dianionic species L2- with the release of two tetramethylsilane. The resulting L2- combined with three THF molecules and an alkyl unit coordinates to Y3+ and Lu3+ ions, respectively, in a rare N,C-bidentate mode, to generate distorted octahedron geometry ligand core. Whereas, with treatment of H2L with equimolar Sc(CH2SiMe3)3(THF)2, a heteroleptic complex (HL)(L)Sc(THF) () was isolated as the main product, where the dianionic L2- species bonds to Sc3+ via chelating N,C atoms whilst the monoanionic HL connects to Sc3+ in an S,N-bidentate mode. All complexes have been characterized by NMR spectroscopy and X-ray diffraction analysis.     

Structural and photophysical properties of lathanide(III) complexes with a novel octadentate iminophenolate bibracchial lariat ether

We report here a structural and photophysical study of lanthanide complexes with the di-deprotonated form of the bibracchial lariat ether N,N'-bis(2-salicylaldiminobenzyl)-4,10-diaza-12-crown-4 (L(3)) (Ln = Ho(III)-Lu(III)). The X-ray crystal structures of [Ho(L(3)-2H)](ClO(4)) (1) and [Er(L(3)()-2H)](ClO(4)) (2) show the metal ion being eight-coordinate and deeply buried in the cavity of the dianionic receptor. Both sidearms of L(3) are on the same side of the crown moiety, resulting in a syn conformation. Likewise, the lone pair of both pivotal nitrogen atoms is directed inward of the receptor cavity in an endo-endo arrangement and the coordination polyhedron around the lanthanide ion may be described as a distorted square antiprism that shows a deformation toward a square prism by ca. 11 degrees . Attempts to isolate complexes of the lightest members of the lanthanide series were unsuccessful, which suggests a certain degree of selectivity of L(3) toward the heaviest Ln(III) ions. This was evaluated and rationalized on the basis of theoretical calculations performed in vacuo at the HF level, by using the 3-21G basis set for the ligand atoms and a 46+4f(n) effective core potential for lanthanides. For the [Ln(L(3)()-2H)](+) systems, the calculated bond distances between the metal ion and the coordinated donor atoms decrease along the lanthanide series, as usually observed for Ln(III) complexes. However, for the related [Ln(L(1)-2H)](+) and [Ln(L(2)()-2H)](+) systems our ab initio calculations provide geometries in which some of the bond distances of the metal coordination environment increase across the lanthanide series. Thus, thanks to the variation of the ionic radii of the lanthanide ions, receptors L(1)() (N,N'-bis(2-salicylaldiminobenzyl)-4,13-diaza-18-crown-6) and L(2) (N,N'-bis(2-salicylaldiminobenzyl)-1,10-diaza-15-crown-5) are specially adapted for the complexation of the lighter lanthanide ions. On the other hand, the erbium and ytterbium complexes of L(3) have been shown to be emissive in the near-IR. Time-resolved studies of complexes confirm that solvent is excluded from the inner coordination sphere in solution. The luminescence properties of the complexes make them ideally suited for use as luminescent tags and suggest that q = 0 complexes of erbium may, after all, be useful as luminescent tags in protic media.