CdSe and CdSe/CdS nanorod solids

We demonstrate the self-organization of CdSe nanorods into nematic, smectic, and crystalline solids. Layered colloidal crystals of CdSe nanorods grow by slow destabilization of a nanocrystal solution upon allowing the diffusion of a nonsolvent into the colloidal solution of nanocrystals. The colloidal crystals of nanorods show characteristic birefringence, which we assign to specific spherulite-like texture of each nanorod assembly. To demonstrate the general character of nanorod self-assembly technique, CdSe/CdS heterostructure nanorods were organized into highly luminescent superlattices.     

Synthesis of a model system for the preparation of phloroglucinol containing natural products

A model system for the synthesis of phloroglucinol containing natural products was synthesized. Key steps include a manganic acetate-mediated cyclization and the facile conversion of an alkene into a β-bromoenone.     

Potential of zero total charge of platinum single crystals: A local approach to stepped surfaces vicinal to Pt(111)

The electrochemical behavior of platinum single-crystal electrodes is revisited, with special emphasis on the determination of the potential of zero charge. We show that the measure of the charge displaced during CO adsorption allows the determination of the potential of zero total charge (PZTC). The estimation of the potential of zero free charge (PZFC) is discussed, with different degrees of approximation. The application of this methodology to the study of the PZTC of platinum stepped surfaces vicinal to Pt(111) reveals a marked decrease of the PZTC due to the introduction of surface steps. This effect is interpreted as the result of the existence of markedly smaller surface potentials localized on step sites. The importance of considering local aspects of the interface is emphasized with the use of N₂O reduction as a sensitive probe to the local structure of the surface. It is proposed that the different local maxima observed in the absolute value of the reduction current correspond to the local values of PZTC. It is shown that there is, in general, good agreement between the overall PZTC, obtained from the CO displacement, and that calculated from the local values inferred from the N₂O reduction. Further insight is obtained with the application of the laser-induced temperature jump method. This technique is useful to calculate the potential of maximum entropy of the double-layer formation. The resulting value of this potential for Pt(111) is discussed in the light of the PZFC value obtained from different approaches. For stepped surfaces vicinal to Pt(111), two local maxima in the entropy of the double layer are observed that are close to the local PZTC values estimated from the N₂O reduction. This result suggests the existence of cooperative effects in the organization of the water dipoles close to the electrode surface. Published in Russian in Elektrokhimiya, 2006, Vol. 42, No. 11, pp. 1275–1292. Based on the report delivered at the 8th International Frumkin Symposium “Kinetics of the Electrode Processes,” October 18–22, 2005, Moscow. The text was submitted by the authors in English.     

Solid-phase synthesis of a tyrphostin ether library

The solid-phase synthesis of a 4500-member (30 x 15 x 10) tyrphostin library is demonstrated utilizing the Irori-directed sorting system. Fmoc-protected PL-Rink resin was used as the solid support. After Fmoc-deprotection, aryl aldehydes were attached to the resin through reductive amination. Acylation of the resulting secondary amines with cyanoacetic acid was followed by a Knoevenagel condensation with phenolic aldehydes. Mitsunobu coupling of primary alcohols to the resin-bound phenols yielded the final library of compounds 1.     

Di­chloro­bis(1‐propyl­imidazolidine‐2‐thione‐κS)­cobalt(II)

The crystal structure of the title compound, [CoCl₂(C₆H₁₂N₂S)₂], consists of monomer units of a Co^II atom coordinated to two 1‐propyl­imidazolidine‐2‐thione ligands and to two chloride ions. The heterocyclic thione ligand is monodentate and coordinated to the metal through the thione S atom. The environment around the Co^II atom is a slightly distorted tetrahedron. The Co—S bond lengths are 2.341 (2) and 2.330 (2) Å, and the Co—Cl bond lengths are 2.234 (2) and 2.238 (2) Å. The most important point of distortion is the S—Co—S bond angle of only 97.83 (8)°. Intramolecular classical hydrogen bonds are found between the chloride ions and the N—H groups. Additionally, intra‐ and intermolecular non‐classical hydrogen bonds are found.     

Room-temperature liquid phosphorimetry of the aluminium-ferron chelate in micellar media : Determination of aluminium

Aluminium reacts with 7-iodo-8-quinolinol-5-sulphonic acid (Ferron) in cetyltrimethylammonium bromide (CTAB) micelles to form a highly phosphorescent complex at room temperature. Suitable experimental conditions and the phosphorescent characteristics of the complex are described. Comparison with the results obtained for the phosphorescent niobium-Ferron complex in CTAB micelles helps to elucidate the mechanism of this type of phosphorescence. For aluminium the detection limit is 5.4 ng ml^?1; the relative standard deviation is 4.5% for 20 μg Al. The method is applied to aluminium determination in waters and dialysis fluids.     

Ag(I) complexes with alkylidene-bis(2-aminopyrimidines) as building units for discrete metallomacrocyclic frames. A structural and solution study

Alkylidene-bis(2-aminopyrimidines) (pyr2Cx, x = 2-5) are useful ligands to interact with Ag(I) yielding discrete metallocycles. Crystal structures of the [(pyr2C2)Ag(NO3)]2 and [(H-pyr2C4)Ag(NO3)2]2 have been isolated where each macrocyclic moiety interacts with their surroundings through weak interactions, yielding 3D discrete structures, On the other hand, the solution study shows that the equilibrium constants for the formation of Ag(pyr2Cx)+ complexes are higher than the literature values for Ag(I) complexes with single pyrimidines, although the differences could be explained by invoking the solid-state structures of the Ag(I)-pyr2Cx complexes.     

Synthesis,Spectroscopic and EPR Results and Crystal Structure of Copper(II) Formato Derivatives with Pyrazine and Dimethylpyrazines

The complexes of copper formato with pyrazine and dimethylpyrazines: Cu(HCOO)₂(pyrz) ( 1 ), Cu₂(HCOO)₄(pyrz) ( 2 ), Cu₂(HCOO)₄(2,3‐Me₂pyrz) ( 3 ), Cu₂(HCOO)₄(2,5‐Me₂pyrz) ( 4 ), and Cu₂(HCOO)₄(2,6‐Me₂pyrz)₂ ( 5 ) have been synthesized and characterized by chemical analysis and IR and electronic spectro scopies. The three‐dimensional structure of compound 1 consists of –Cu–pyrz–Cu–pyrz– chains joined by bridging formate groups coordinated, in configuration syn‐anti, to two copper atoms. The coordination around the copper atom is orthorhombic with two Cu–O distances of 2.374(1) Å, two Cu–O of 1.952 Å and two Cu–N of 2.080 Å. Compound 5 is formed by molecular dimers with the [Cu₂(μ‐HCOO)₄] unit, two copper atoms and four syn‐syn fomate groups, and two ligands coordinated to the copper atoms in the axial positions. In compounds 2 and 3 chains of [Cu₂(μ‐HCOO)₄] dimers with pyrz or 2,3‐Me₂pyrz as bridging ligands are formed. The EPR signal of 1 is orthorhombic (g = 2.23, 2.20 and 2.06). In the EPR spectra of 2 – 5 compounds the triplet (S = 1) signals are observed. The g_?, g_∥ and D values are been calculated.     

Quantitative characterization of the global electrophilicity pattern of some reagents involved in 1,3-dipolar cycloaddition reactions

The global electrophilicity power, ω, of a series of dipoles and dipolarophiles commonly used in 1,3-dipolar cycloadditions may be conveniently classified within a unique relative scale. The effects of chemical substitution on the electrophilicity of molecules have been evaluated using a representative set of electron-withdrawing and electron-releasing groups for a series of dipoles including nitrone, nitrile oxide and azide derivatives. The absolute scale of electrophilicity is used to rationalize the chemical reactivity of these species as compared to the static reactivity pattern of the reagents involved in the Diels-Alder reactions.     

Secondary metabolites isolated from Colletotrichum species

Structural and biosynthetic studies of the metabolites isolated from various Colletotrichum species are reviewed. These fungi are destructive post-harvest pathogens on a wide range of plants including cereals, legumes and fruits. The review includes a detailed study of the biological activity of these metabolites and their role in the development of plant diseases. The literature in this field to the present is reviewed and 60 references are cited.