Die Pyridinaddukte der Goldhalogenide. 2. Darstellung,Eigenschaften und Kristallstruktur von AuCl · NC5H5 und Aul · NC5H5

Pyridine Adducts of the Gold Halides. 2. Synthesis, Properties, and Crystal Structure of AuCl · NC₅H₅ and AuI · NC₅H₅ AuCl · py is formed by the reaction of AuCl · S(CH₂C₆H₅)₂ with pyridine in absolute Ethanol. AuI · py can be obtained from AuI and pyridine in toluene. Both compounds are sensitive to light and thermically instable. AuI · py decomposes already above ?30°C. AuCl · py crystallizes monoclinic with 16 formula units in the space group C2/c, AuI · py is orthorhombic with the space group Pnnm and 8 formula units per unit cell. The structures of the adducts are built up by linear Au(py)₂ and AuX₂ groups, which are linked together to tetranuclear, chainlike complexes AuX₂? Au(py)₂? Au(py)₂? AuX₂ by weak gold-gold bonds. (AuI · py)₄ forms a linear Au₄ chain and possesses nearly the symmetry D_2h. The shortest Au-Au distance being 299.0 pm. In the centrosymmetrical (AuCl · py)₄ an Au₄-zig-zag chain with Au? Au distances of 324.9 and 341.6 pm is observed. The gold-ligand bond lengths are: AuCl · py: Au? Cl = 228 pm, Au? N = 209 pm; AuI · py: Au? I = 254.4, Au? N = 202 pm. The IR spectra and the luminescence properties are discussed.     

The stability of gold iodides in the gas phase and the solid state

The stability of gold iodides in the oxidation state +I and +III is investigated at the ab initio and density functional level using relativistic and nonrelativistic energy-adjusted pseudopotentials for gold and iodine. The calculations reveal that relativistic effects stabilize the higher oxidation state of gold as expected, that is Au2I6 is thermodynamically stable at the relativistic level, whilst at the nonrelativistic level the complex of two iodine molecules weakly bound to both gold atoms in Au2I2 is energetically preferred. The rather low stability of AuI3 with respect to dissociation into AuI and I2 will make it difficult to isolate this species in the solid state as (possibly) Au2I6 or detect it by matrix-isolation techniques. The monomer AuI3 is Jahn-Teller distorted from the ideal trigonal planar (D3h) form, but adopts a Y-shaped structure (in contrast to AuF3 and AuCl3), and in the nonrelativistic case can be described as I2 weakly bound to AuI. Relativistic effects turn AuI3 from a static Jahn-Teller system to a dynamic one. For the yet undetected gas-phase species AuI accurate coupled-cluster calculations for the potential energy curve are used to predict vibrational-rotational constants. Solid-state density functional calculations are performed for AuI and Au2I6 in order to predict cohesive energies.     

Luminescent chains formed from neutral, triangular gold complexes sandwiching TlI and AgI. Structures of (Ag([Au(mu-C2,N3-bzim)]3)2)BF4.CH2Cl2, (Tl([Au(mu-C2,N3-bzim)]3)2)PF(6).0.5THF (bzim = 1-benzylimidazolate), and (Tl([Au(mu-C(OEt)=NC6H4CH3)]3)2)PF6.THF, with MAu6 (M = Ag+, Tl+) cluster cores

It has been found that several trinuclear complexes of AuI interact with silver and thallium salts to intercalate Ag+ and Tl+ cations, thereby forming chains. The resulting sandwich clusters center the cations between the planar trinuclear moieties producing structures in which six AuI atoms interact with each cation in a distorted trigonal prismatic coordination. The resultant (B3AB3B3AB3)infinity pattern of metal atoms also shows short (approximately 3.0 A) aurophilic interactions between BAB molecular centers. These compounds display a strong visible luminescence, under UV excitation, which is sensitive to temperature and the metal ion interacting with the gold. X-ray crystal structures are reported for Ag([Au(mu-C2,N3-bzim)]3)2BF4CH2Cl2 (P1, Z = 2, a = 14.4505(1) A; b = 15.098(2)A; c = 15.957(1)A; alpha = 106.189(3) degrees; beta = 103.551(5) degrees; gamma = 101.310(5) degrees); Tl([Au(mu-C2,N3-bzim)]3)2PF(6)05C4H8O (P1, Z = 2, a = 15.2093(1)A; b = 15.3931(4)A; c = 16.1599(4)A; alpha = 106.018(1) degrees; beta = 101.585(2) degrees; gamma = 102.068(2) degrees); and Tl([Au(mu-C(OEt)=NC6H4CH3)]3)2PF6.C4H8O (P2(1)/n, Z = 4, a = 16.4136(3)A; b = 27.6277(4)A; c = 16.7182(1)A; beta = 105.644(1) degrees). Each compound shows that the intercalated cation, Ag+ or Tl+, coordinates to a distorted trigonal prism of six AuI atoms. The counteranions reside well apart from the cations between the cluster chains.     

Synthesis, manipulation and conductivity of supramolecular polymer nanowires

The synthesis of supramolecular conducting nanowires can be achieved by using DNA and pyrrole. Oxidation of pyrrole in DNA-containing solutions yields a material that contains both the cationic polypyrrole (PPy) and the anionic DNA polymers. Intimate interaction of the two polymer chains in the self-assembled nanowires is indicated by FTIR spectroscopy. AFM imaging shows individual nanowires to be continuous, approximately 5 nm high and conformationally flexible. This feature allows them to be aligned by molecular combing in a similar manner to bare DNA and provides a convenient method for fabricating a simple electrical device by stretching DNA/PPy strands across an electrode gap. Current-voltage measurements confirm that the nanowires are conducting, with values typical for a polypyrrole-based material. In contrast to polymerisation of pyrrole on a DNA template in bulk solution, attempts to form similar wires by polymerisation at surface-immobilised DNA do not give a continuous coverage; instead, a beads-on-a-string appearance is observed suggesting that immobilisation inhibits the assembly process.     

Fabrication of surface-supported low-dimensional polyimide networks

Interest in thermal and chemical stability of surface-supported organic networks has stimulated recent attempts to covalently interlink adsorbed molecular species into extended nanostructures. We show, using low-temperature scanning tunneling microscopy, that imidization of anhydrides and amines adsorbed on Au(111) can be thermally initiated under controlled ultrahigh vacuum conditions. Using two types of amine-functionalized polyphenyl molecules together with the organic semiconductor PTCDA, monolayer thick linear polymeric strands and a porous polymeric network with nanoscale dimensions are obtained.     

Structural study of gold clusters

Density functional theory (DFT) calculations were carried out to study gold clusters of up to 55 atoms. Between the linear and zigzag monoatomic Au nanowires, the zigzag nanowires were found to be more stable. Furthermore, the linear Au nanowires of up to 2 nm are formed by slightly stretched Au dimers. These suggest that a substantial Peierls distortion exists in those structures. Planar geometries of Au clusters were found to be the global minima till the cluster size of 13. A quantitative correlation is provided between various properties of Au clusters and the structure and size. The relative stability of selected clusters was also estimated by the Sutton-Chen potential, and the result disagrees with that obtained from the DFT calculations. This suggests that a modification of the Sutton-Chen potential has to be made, such as obtaining new parameters, in order to use it to search the global minima for bigger Au clusters.     

The role of oxidative etching in the synthesis of ultrathin single-crystalline Au nanowires

The fabrication of ultrathin single-crystal Au nanowires with high aspect ratio and that are stable in air is challenging. Recently, a simple wet-chemical approach using oleylamine has been reported for the synthesis of Au nanowires with micrometer length and 2 nm in diameter. Despite efforts to understand the mechanism of the reaction, an ultimate question about the role of oxygen (O(2)) during the synthesis remained unclear. Here we report that the synthesis of ultrathin Au nanowires employing oleylamine is strongly affected by the amount of O(2) absorbed in the reaction solution. Saturating the solution with O(2) leads to both a high-yield production of nanowires and an increase in their length. Nanowires with diameters of about 2 nm and lengths of 8 μm, which corresponds to an aspect ratio of approximately 4000, were produced. The role of oxygen is attributed to the enhanced oxidation of twin defects on Au nanoparticles formed in the first stage of the reaction. Understanding the role of oxidative etching is crucial to significantly increasing the yield and the length of ultrathin Au nanowires.     

New structural motifs in the aggregation of neutral gold(I) complexes: structures and luminescence from (alkyl isocyanide)AuCN

The preparation and X-ray crystal structures of (CyNC)Au(I)CN, (n-BuNC)Au(I)CN, and (i-PrNC)Au(I)CN.0.5CH(2)Cl(2) are reported and compared with those of (MeNC)Au(I)CN and (t-BuNC)Au(I)CN, which were previously described. These linear molecules are all organized through aurophilic interactions into three structural classes: simple chains ((CyNC)Au(I)CN and (t-BuNC)Au(I)CN), side-by-side chains in which two strands make Au...Au contact with each other ((n-BuNC)Au(I)CN), and nets in which multiple aurophilic interactions produce layers of gold(I) centers ((i-PrNC)Au(I)CN and (MeNC)Au(I)CN). All of these five solids dissolve to produce colorless, nonluminescent solutions with similar UV/vis spectra. However, each of the solids displays a unique luminescence with emission maxima occurring in the range 371-430 nm.     

Bromination of (phosphine)gold(I) bromide complexes: stoichiometry and structure of products

The course of the oxidative addition of elemental bromine to complexes of the type (L)AuBr is strongly influenced by the nature of the tertiary phosphine ligand L. Standard square planar gold(III) complexes (L)AuBr3 are obtained not only with L = PMe3 but also with P((I)Pro)3 for which the oxidative addition fails in the corresponding iodine system. Excess bromine is integrated into crystals of the products with the stoichiometry [(Me3P)AuBr3].(Br2) and {[(iPro)3P]AuBr3}.(Br2). Of the series of iodine analogues, an intercalate [(Me3P)AuI3]2.(I2) has been structurally characterized. [((t)Bu)3P]AuBr undergoes ligand redistribution upon treatment with bromine to give a complex reaction mixture, from which {[(tBu)3P]2Au}+(Br3)-.(Br2) could be crystallized. It contains polymeric anions [(Br5)-]n as zig-zag chains. [(o-Tol)3P]AuBr is readily brominated to give [(o-Tol)3P]AuBr3. Contrary to the situation in the gold(I) complex with its linear PAuBr unit, the square planar structure of the PAuBr3 unit causes steric hindering of the rotation of the tolyl groups about the P-C bonds as demonstrated by solution NMR studies. (The corresponding reaction with iodine is known to give only polyiodides with the oxidation state of the gold atom unchanged.) The even more severe congestion in [(Mes)3P]AuBr prevents oxidative addition not only of iodine but also of bromine. With the latter, P-Au cleavage occurs instead affording [(Mes)3PBr]+[AuBr4]-.     

Water-dispersible ultrathin Au nanowires prepared using a lamellar template of a long-chain amidoamine derivative

Straight ultrathin Au nanowires (NWs) with diameters less than 2 nm were synthesized using the lamellar structure of C18AA in an organogel and its selective adsorption for specific gold surfaces. In addition, the potential to form a bilayer structure with interdigitated hydrocarbon chains enabled the production of water-dispersible Au NWs without morphological change.     

Kinetics of receptor directed assembly of multisegment nanowires

We demonstrate the receptor directed end-to-end assembly of multisegment Au/Ni/Au nanowires under agitation in ethanol. The gold end-segments were functionalized with biotin-terminated thiol thereby restricting aggregation to end-to-end attachment via an avidin linkage. On mixing biotin-terminated nanowires with avidin-terminated nanowires, the average chain length is shown to increase linearly with time. The rate constant was independent of the nanowire concentration. Kinetic Monte Carlo simulations were used to model the self-assembly process, and we show that the directed end-to-end assembly of nanowires is similar to the polycondensation of linear polymers.     

Strong electronic consequences of intercalation in cuprate superconductors: the case of a trigonal planar AuI(3) complex stabilized in the Bi(2)Sr(2)CaCu(2)O(y) lattice

Recently, a molecular AuI(3) complex was stabilized in the interlayer space of the Bi(2)Sr(2)CaCu(2)O(y) (Bi2212) high-T(c) superconducting phase, adopting an exceptional D(3)(h) structure (Choy, J.-H.; et al. J. Phys.Chem. B 2000, 104, 7273). If the gold were formally Au(III), a strong Jahn-Teller distortion to T- and Y-shaped structures would be expected. In this work, we try to understand the structural preferences of AuI(3) in both the gas phase and the Bi2212 lattice, as well as the influence of the AuI(3) intercalation on the superconductor lattice. What we think actually happens is that there is an effective electron transfer from the s-type Bi lone pair to the gold, increasing the formal oxidation state of Bi from +3 to +5 and decreasing that of Au from +3 to +1. A trigonal Au(I) trihalide is just fine. The DFT results confirm in the Bi-rich regions the same kind of electron transfer as encountered on the EHT level of theory, but they reveal additional complexities of the problem. The effect of the Bi to intercalating molecule electron transfer on the cuprate layer may be important, quite apart from this specific example, in tuning superconductivity in the cuprates.     

Mo(W)/Cu(Ag，Au)/S原子簇聚合物的研究进展

本文将Mo(W)/Cu(Ag，Au)/S原子簇聚合物分成了四类，简要的总结了近年来在这类原子簇聚合物的构筑方面的一些成果，以期找到这类原子簇聚合物构筑的规律，并在此基础上对这类原子簇聚合物的构筑进行了展望。另外，本文还介绍了这类原子簇聚合物的三阶非线性光学性质的研究进展，并展望了其今后进一步研究的方向。     

偶氮吡啶分子结的制备、表征及电学性质初步研究

具有特异电学性质的分子结的制备及电子输运特性研究是分子电子学领域中的主要内容,对构筑分子电子器件具有重要意义．但是,由于分子结的尺度通常在100nm以下,这使得分子结的低缺陷制备和准确有效的电学特性研究面临困难．目前,自组装方法已经成为降低分子结缺陷的主要手段,     

Au nanowire fabrication from sequenced histidine-rich peptide

A new biological approach to fabricate Au nanowires was examined by using sequenced histidine-rich peptide nanowires as templates. The sequenced histidine-rich peptide molecules were assembled as nanowires, and the biological recognition of the sequenced peptide toward Au lead to efficient Au coating on the nanowires. Monodisperse Au nanocrystals were uniformly coated on the histidine peptide nanowires with the high-density coverage, and the crystalline phases of the Au nanocrystals were observed as (111) and (220). The uniformity of the Au coating on the nanowires without contamination of precipitated Au aggregates is advantageous for the fabrication of electronics and sensor devices when the nanowires are used as the building blocks. We believe this simple metal nanowire fabrication method can be applied to various metals and semiconductors with peptides whose sequences are known to mineralize specific ions.     

Fabrication of DNA nanowires by orthogonal self-assembly and DNA intercalation on a Au patterned Si/SiO2 surface

A novel Ru complex bearing both an acridine group and anchoring phosphonate groups was immobilized on a surface in order to capture double-stranded DNAs (dsDNAs) from solution. At low surface coverage, the atomic force microscopy (AFM) image revealed the "molecular dot" morphology with the height of the Ru complex ( approximately 2.5 nm) on a mica surface, indicating that four phosphonate anchor groups keep the Ru complex in an upright orientation on the surface. Using a dynamic molecular combing method, the DNA capture efficiency of the Ru complex on a mica surface was examined in terms of the effects of the number of molecular dots and surface hydrophobicity. The immobilized surface could capture DNAs; however, the optimal number of molecular dots on the surface as well as the optimal pull-up speed exist to obtain the extended dsDNAs on the surface. Applying this optimal condition to a Au-patterned Si/SiO 2 (Au/SiO 2) surface, the Au electrode was selectively covered with the Ru complex by orthogonal self-assembly of 4-mercaptbutylphosphonic acid (MBPA), followed by the formation of a Zr (4+)-phosphonate layer and the Ru complex. At the same time, the remaining SiO 2 surface was covered with octylphosphonic acid (OPA) by self-assembly. The selective immobilization of the Ru complex only on the Au electrode was identified by time-of-flight secondary-ion mass spectrometry (TOF-SIMS) imaging on the chemically modified Au/SiO 2 surface. The construction of DNA nanowires on the Au/SiO 2 patterned surface was accomplished by the molecular combing method of the selective immobilized Ru complex on Au electrodes. These interconnected nanowires between Au electrodes were used as a scaffold for the modification of Pd nanoparticles on the DNA. Furthermore, Cu metallization was achieved by electroless plating of Cu metal on a priming of Pd nanoparticles on the Pd-covered DNA nanowires. The resulting Cu nanowires showed a metallic behavior with relatively high resistance.     

Polymer-anchored DNA gene monolayers

Monolayers of DNA chains of polymeric dimensions, considered here to be longer than approximately 100 nucleotides, are widely encountered in biomolecular diagnostics as well as present for a model system for investigating behavior of polyelectrolytes at interfaces. A major challenge in advancing such applications is assembling the DNA on the surface in a controlled way. Although covalent immobilization is expected to produce optimal stability, the multitude of potential reactive sites along the contour of long DNA molecules requires that any chemical transformations be strictly site-specific to preserve control over attachment geometry and function. A synthetic approach to fabricating monolayers of DNA genes on gold using polymeric anchor (adhesion) films is presented that (i) possesses stringent site-specificity of surface-attachment, (ii) exhibits excellent stability to elevated temperatures, allowing denaturation of duplex chains at 90 degrees C without loss of surface-linked strands, and (iii) achieves surface coverages suitable for investigating multichain polyelectrolyte behavior in regimes of strong interchain interactions.     

银/金纳米线阵列表面增强拉曼基底的制备及对孔雀石绿的高灵敏度检测

利用种子介导的软模板生长方法制备了金纳米线(Au NWs)阵列, 通过调节生长温度控制Au NWs阵列的形貌, 最后在经硼氢化钠(NaBH₄)清洗过的Au NWs阵列上化学沉积银纳米颗粒(Ag NPs), 制得银/金纳米线(Ag/Au NWs)阵列作为表面增强拉曼散射(SERS)基底. 选用罗丹明6G(R6G)作为拉曼探针分子测定了Ag/Au NWs阵列的SERS性能. 结果表明, Ag/Au NWs阵列作为SERS基底具有高灵敏度、 优异的信号均匀性和良好的稳定性. 使用Ag/Au NWs阵列对孔雀石绿(MG)检测的检出限可低至1×10^-8 mol/L, 线性范围为 1×10^-8~1×10^-4 mol/L. NaBH₄可以在不影响SERS性能的情况下去除Ag/Au NWs阵列上吸附的分子, 使得 SERS基底可以重复使用. 使用Ag/Au NWs阵列对湖水中的MG进行检测, 得到了可靠的回收率, 证明Ag/Au NWs 阵列在检测环境水体中的孔雀石绿上具有应用潜力.     

Oriented organic islands and one-dimensional chains on a Au(111) surface fabricated by electrodeposition: an STM study

Organic islands and oriented one-dimensional (1D) chains are fabricated on a Au(111) surface by electrodeposition. The cyclic voltammograms (CVs) of Au(111) in solutions containing nitrobenzene and picric acid show an electrochemical reaction in a negative potential region, which results in irreversible reductive deposition. The deposition process is monitored by in situ electrochemical scanning tunneling microscopy (ECSTM). At the double layer potential region, for example, nitrobenzene molecules form a well-defined adlayer in a (square root(3) x square root(3)) structure. With potential shifting negative to the reductive region, nitrobenzene is reduced to hydroxyaminobenzene. Organic islands were formed first and then aggregated into ordered 1D chains. The formation of these organic islands and 1D chains is completely potential-dependent. Intriguingly, the so-prepared islands and 1D chains are well-oriented along the reconstructed lines of the underlying Au(111) substrate and stable under ambient conditions even if the sample was removed from electrolyte solution. The results reported here provide a simple and effective method to fabricate oriented organic nanodots and nanowires on a solid surface by an electrochemical technique.     

A Robust Solution-Based Approach to Monodisperse Hybrid Janus Nanofibers

Monodisperse hybrid Janus nanofibers with the structure that one Au nanoparticle (AuNP) is connected to one end of a polymeric nanofiber were prepared by the self‐assembly between polymeric micelles and the tadpole‐like conjugates resulting from one‐to‐one complexation of long DNA chains with AuNPs.