Directional synthesis and assembly of bimetallic nanosnowmen with DNA

Synthesizing and assembling nanoscale building blocks to form anisotropic nanostructures with the desired composition and property are of paramount importance for the understanding and use of nanostructured materials. Here we report a salt-tuned synthetic strategy using DNA-modified Au nanoparticles (DNA-AuNPs) to form Au-Ag head-body nanosnowman structures in >95% yield. We propose a mechanism for the formation of asymmetric Au-Ag nanosnowmen from DNA-AuNPs, salts, and Ag-precursor-loaded polymers. Importantly, we show that oriented assemblies of various nanostructures are readily obtained using nanosnowmen with asymmetrically modified DNA as building blocks.     

Two-dimensional metamagnet composed of cyano-bridged CuII-WV bimetallic assembly

Two-dimensional cyanide-bridged copper(II) octacyanotungstates(V), [(Cu(3-CNpy)2(H2O))2(Cu(3-CNpy)2(H2O)2)(W(CN)8)2] (3-CNpy = 3-cyanopyridine) (1) and [(Cu(4-CNpy)2)2(Cu(4-CNpy)2(H2O)2)(W(CN)8)2] x 6H2O (4-CNpy = 4-cyanopyridine) (2), were prepared and these compounds exhibited metamagnetic behavior with Néel temperatures of 8.0 K (1) and 4.4 K (2).     

Spin densities in a ferromagnetic bimetallic chain compound: polarized neutron diffraction and DFT calculations

The spin population distribution in the ferromagnetically coupled hetero-bimetallic chain compound [MnNi(NO(2))(4)(en)(2)] (en = 1,2-ethanediamine) has been investigated by means of polarized neutron diffraction experiments, and the results compared with those from theoretical estimates obtained via calculations based on density functional theory on dinuclear molecular models of the chain. The spin distributions obtained from experiment and from theory are consistent and reflect a larger spin delocalization from the Ni atom due to the more covalent character of the Ni-N bonds compared to the Mn-O ones. Also a nearly isotropic spin distribution is observed for the more ionic d(5) Mn(2+) ion and a clearly anisotropic distribution for the d(8) Ni(2+) ion. The use of dinuclear molecular models for the calculation of the exchange coupling constant between Ni and Mn provide upper and lower limits (+17.6 and -4.2 cm(-)(1)) for the experimentally determined value (+1.3 cm(-)(1)), depending on how the missing part of the chain is simulated, but yield essentially the same spin distribution. The Mn(II)-Ni(II) weak ferromagnetic coupling in the chain is interpreted in a spin delocalization mechanism as resulting from the weakness of the overlap between the magnetic orbitals centered on nickel and those centered on manganese which are only weakly delocalized on the ligands.     

Coexistence of long-range ferromagnetic ordering and glassy behavior in one-dimensional bimetallic cyano-bridged polymers

Two new one-dimensional (1-D) 3d-5d cyano-bridged bimetallic assemblies, ([Co(3)(II)(DMF)(12)][W(V)(CN)(8)](2)])(infinity) (1) and ([Mn(3)(II)(bipy)(2)(DMF)(8)][W(V)(CN)(8)](2))(infinity) (2), have been synthesized and characterized, where bipy stands for 2,2'-bipyridine and DMF represents N,N-dimethylformamide. The X-ray analyses show that the two complexes belong to the P(-)1 space group with Z = 1 and C(52)H(84)N(28)O(12)Co(3)W(2), a = 11.690(3) A, b = 12.703(3) A, c = 13.712(3) A, alpha = 86.889(4) degrees, beta = 73.256(4) degrees, and gamma = 77.033(4) degrees for 1 and C(60)H(72)N(28)O(8)Mn(3)W(2), a = 10.672(2) A, b = 13.024(3) A, c = 16.000(3) A, alpha = 78.32(3) degrees, beta = 75.69(3) degrees, and gamma = 66.63(3) degrees for 2. The structures of the two complexes are similar and consist of 12-atom rhombic M(2)W(2)(CN)(4) (M = Co (1), Mn (2)) units, which act as a basic component to be repeatedly connected through W-C-N-M-N-C-W linkages to form a one-dimensional infinite 3,2-chain; these chains are well separated by the DMF molecules or 2,2'-bipyridines coordinated to the metal ions Co(2+) for 1 and Mn(2+) for 2. Magnetic studies, including linear and nonlinear ac susceptibility measurements, demonstrate that the long-range magnetic ordering and spin glass behavior coexist in the two 1-D compounds.     

Solvent dependent assembly and disassembly of a hydrogen bonded helical structure in a Co-Mo bimetallic complex

The effect of solvent on the assembly and disassembly of a hydrogen bonded helical structure in a bimetallic cobalt complex of a molybdenum-containing metalloligand and their spontaneous resolution has been demonstrated.     

Synthesis and characterization of bimetallic Ni-Cu particles

Bimetallic Ni-Cu particles were synthesized from either suspensions of nickel carbonate and copper carbonate, and solutions of nickel nitrate and copper nitrate in ethylene glycol which acts both as solvent and reducing agent. The nature and composition of the powders depend on both the reaction temperature and time, and the reactants. Using the carbonates, bimetallic Ni-Cu powders composed of a nickel-rich and a copper-rich solid solution were obtained after 39 h at 140°C. Increasing the reaction temperature to 190°C gives a Ni-Cu powder composed of a copper-rich solid solution and nickel. Particles obtained under these conditions, however, are polydisperse. The nitrate solution gave bimetallic Ni-Cu particles with a narrow size distribution of about 140 nm after 4 h of reaction at 196°C. These particles are made of a copper core and a nickel shell. The mechanism of bimetallic particle formation is controlled by the solubility of the reactants, the formation of intermediate metal glycolates and Cu₂O, and the required reduction temperature.     

Synthesis and cytotoxicity of a bimetallic ruthenocene dicobalt-hexacarbonyl alkyne peptide bioconjugate

Organometallic conjugates of receptor-targeting peptides are proposed as interesting candidates for novel cancer therapies since they are capable of targeting a specific kind of cell. Here, we have synthesised a dicobalt hexacarbonyl alkyne compound linked to the neurotensin peptide hormone. In order to circumvent synthetic difficulties encountered when adding a cobalt carbonyl moiety onto the hydrophilic alkyne peptide, and to enhance the cellular uptake we functionalised the alkyne neurotensin(8-13) fragment (NT) first N-terminally by ruthenocene carboxylic acid to form the metallocene-alkyne-NT conjugate 3, before adding Co?(CO)? to a propargyl glycine residue to form the Co-alkyne derivative 4. Compound 4 represents the first heterobimetallic organometallic peptide conjugate reported to date. It shows moderate cytotoxicity against HeLa, PT45 and HepG2 cell lines.     

Synthesis of a bimetallic platinum-tungsten complex with a bridging micro-diboranyl-oxycarbyne moiety

The novel bimetallic micro-diboranyl-oxycarbyne bridged platinum-tungsten complex [W{eta(1),micro-CO-B(NMe(2))-B(NMe(2))-(eta(5)-C(5)H(4))}(CO)(2){Pt(PPh(3))(2)}] (W-Pt) () has been synthesised by a two-step reaction, starting from the dilithiated half-sandwich compound Li[W(eta(5)-C(5)H(4)Li)(CO)(3)] () via the ansa-diboranyl-oxycarbyne tungsten complex [W{eta(1)-CO-B(NMe(2))B(NMe(2))(eta(5)-C(5)H(4))}(OC)(2)] () by use of stoichiometric amounts of B(2)(NMe(2))(2)Br(2) and [Pt(eta(2)-C(2)H(4))(PPh(3))(2)], respectively.     

One step assembly of a nonanuclear CrIII2NiII7 bimetallic cyanide bridged complex

The reaction of hexacyanochromate with connectivity 6 and a mononuclear Ni complex bearing a bulky tridentate macrocycle leads in one step to the formation of a nonanuclear Cr2Ni7 complex with central low spin and peripheral high spin Ni ions; fast tunnelling of the magnetization is observed at low temperature by micro-SQUID studies on a single crystal.     

Photoinduced magnetization with a high curie temperature and a large coercive field in a cyano-bridged cobalt-tungstate bimetallic assembly

A three-dimensional magnetic material [{CoII(pyrimidine)(H2O)}2{CoII(H2O)2}{WV(CN)8}2](pyrimidine)2. 2H2O is prepared. This compound exhibits a charge-transfer-induced spin transition with a large thermal hysteresis loop of 90 K. Irradiating with light causes the low-temperature phase to exhibit a spontaneous magnetization with a Curie temperature of 40 K and a magnetic hysteresis loop with a coercive field of 12 000 G, which is the highest value reported for a photomagnet. The observed photoinduced magnetization is due to the charge-transfer phase transition from the {CoIIhs(S = 3/2)}{CoIIIls(S = 0)}2-NC-{WIV(S = 0)}2 phase to the {CoIIhs(S = 3/2)}3-NC-{WV(S = 1/2)}2 phase by the irradiation.     

Synthesis and properties of films of a polyimide filled with ferromagnetic nanoparticles

Film-forming polyimide nanocomposites containing 5 to 20 wt % nanoparticles were prepared from ferromagnetic Fe/Fe₃O₄ nanoparticles and a polyimide derived from 4,4′-bis(4-aminophenoxy)diphenyl sulfone and 1,3-bis(3,4-dicarboxyphenoxy)benzene dianhydride. The mechanical properties and magnetization of the nanocomposite samples were studied in relation to the nanoparticle concentration.     

AgPd双金属纳米空心球的合成及其催化性能

以Ag纳米颗粒为牺牲模板,H₂PdCl₄为前驱体,抗坏血酸为还原剂,聚乙烯吡咯烷酮为表面活性剂,在70 ℃下采用电偶置换法结合还原法制备出AgPd双金属纳米空心球。采用紫外可见光谱、粉末X射线衍射、透射电镜结合能量色散等手段对由不同体积的0.01 mol·L^-1 H₂PdCl₄溶液制备的产物进行结构表征。结果表明,随着H₂PdCl₄溶液体积的增加,产物的空心化程度逐渐升高,晶粒的尺寸逐渐增大。当 H₂PdCl₄溶液体积为 120 μL时,合成的 AgPd双金属纳米空心球组成和结构较为均匀,其粒径约为 25 nm,壳层厚度 2~3 nm。双金属中,由于 Ag 和 Pd 电负性的差异,电子从 Ag 转移到了 Pd,使 Pd 表面出现电子富集区,显著提高了其催化效率。将所合成的AgPd双金属以及纯金属Ag和Pd作为催化剂,分别用于硼氢化钠催化还原4-硝基苯酚的反应,发现AgPd双金属的催化性能远高于纯金属Ag和Pd,其中AgPd-120纳米空心球(H₂PdCl₄溶液体积120 μL)作催化剂时的反应速率常数最高,是同等尺寸纯Ag纳米球的24.0倍,纯Pd纳米立方体的14.7倍。     

Selective dehydrogenation of isopropyl alcohol on low-percentage supported bimetallic rhenium-containing catalysts

The activity and selectivity of mono-and bimetallic sibunite-supported Re-, Cu-, Ni-, and Pd-containing catalysts in dehydrogenation of isopropyl alcohol to acetone (T=200–275 °C,v=1.1h⁻¹) were studied. The bimetallic Re, Cu-, Re, Ni-, and Re, Pd-catalysts containing 1 or 2% of the metal possess the higher activity and stability than monometallic catalysts. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2381–2383, November, 1998.     

Polymer-coated ferromagnetic colloids from well-defined macromolecular surfactants and assembly into nanoparticle chains

A novel synthetic route to polymer-coated ferromagnetic colloids of metallic cobalt has been developed. Well-defined end-functional polystyrenes were synthesized using controlled radical polymerization and used as surfactants in the thermolysis of dicobaltoctacarbonyl to afford uniform ferromagnetic nanoparticles. The presence of the polymer shell enabled prolonged colloidal stability of dispersions in a wide range of organic solvents and formed glassy encapsulating coatings around ferromagnetic cores in the solid state. These polymer-coated colloids assembled into robust, micron-sized nanoparticle chains when cast onto supporting surfaces due to dipolar associations of magnetic cores. Hierarchical assemblies were also prepared by blending polystyrene-coated cobalt colloids with larger silica beads.     

Synthesis and characterization of dendrimer templated supported bimetallic Pt-Au nanoparticles

Bimetallic dendrimer-stabilized nanoparticles (DSNs) were used to prepare supported Pt-Au catalysts within the bulk miscibility gap for this binary system. Hydroxy-terminated generation 5 PAMAM dendrimers were used to prepare Cu(0) nanoparticles (NPs). The Cu(0) NPs were subsequently used to reduce K(2)PtCl(4) and HAuCl(4), preparing stabilized bimetallic Pt-Au NPs with a 1:1 stoichiometry. The stabilized NPs were adsorbed onto a high surface area silica support and thermally activated to remove the dendrimers. Transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), and infrared spectroscopy of adsorbed CO showed that this preparation route resulted in NPs in which the two metals are intimately mixed and that the majority of the bimetallic NPs were smaller than 3 nm. Further, the bimetallic NPs were highly active for CO oxidation catalysis near room temperature and showed evidence of CO induced restructuring at ambient temperatures.     

Pt nanoparticles decorated with a discrete number of DNA molecules for programmable assembly of Au-Pt bimetallic superstructures

Discrete DNA decorations of Pt nanoparticles (PtNPs) are realized for the first time, which provide a valence control over the quasi-molecular self-assembly of Au-Pt bimetallic heteronanostructures with DNA as the guide.     

Cyano-bridged gadolinium(III)-tungstate(V) bimetallic assembly with a one-dimensional chain structure

In this paper, we report the crystal structure and magnetic properties of the cyano-bridged gadolinium-tungstate bimetallic assembly, GdIII(DMF)6[WV(CN)8](DMF =N,N-dimethylformamide). X-Ray single crystal analysis shows that this compound crystallizes in the monoclinic system of space group P2(1)/c with cell constants a= 16.40(2)A, b= 11.08(1)A, c= 21.18(2)A, beta= 91.09(8) degrees, and Z= 4. The crystal consists of one-dimensional linear chains, in which [GdIII(DMF)6]3+ and [WV(CN)8]3- ions are linked in an alternating fashion. The magnetic data show that this compound is a paramagnet with an antiferromagnetic coupling of -0.58 cm-1 between GdIII(S= 7/2) and WV(S= 1/2).