Sulfur‐containing derivatives of 1,4‐naphthoquinone,part 2: Sulfenyl derivative synthesis

Sulfenylchlorides, sulfenates, and sulfenamides of 1,4‐naphthoquinone were synthesized, and different methods of their syntheses were investigated. Synthesized sulfenates and sulfenamides are stable due to the large electron‐withdrawing potential of the conjugated quinonic system. Obtained mono‐ and bi‐functional sulfenderivatives are very important in organic synthesis of different new heterocyclic compounds. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:587–598, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20157     

Copolymerization of Metal Nanoparticles: A Route to Colloidal Plasmonic Copolymers

The resemblance between colloidal and molecular polymerization reactions is very useful in fundamental studies of polymerization reactions, as well as in the development of new nanoscale systems with desired properties. Future applications of colloidal polymers will require nanoparticle ensembles with a high degree of complexity that can be realized by hetero‐assembly of NPs with different dimensions, shapes, and compositions. A method has been developed to apply strategies from molecular copolymerization to the co‐assembly of gold nanorods with different dimensions into random and block copolymer structures (plasmonic copolymers). The approach was extended to the co‐assembly of random copolymers of gold and palladium nanorods. A kinetic model validated and further expanded the kinetic theories developed for molecular copolymerization reactions.     

Metal ion complexation in acetonitrile by di-ionized calix[4]arenes bearing two dansyl fluorophores

The influence of metal cations (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Ag⁺, Cd²⁺, Co²⁺, Fe²⁺, Hg²⁺, Mn²⁺, Pb²⁺, Zn²⁺ and Fe³⁺) on the spectroscopic properties of two dansyl (1-dimethylaminonaphthalene-5-sulfonyl) groups linked to the lower rims of a series of three, structurally related, di-ionized calix[4]arenes was investigated by means of absorption and emission spectrophotometry. Di(tetramethylammonium) salts of the di-ionized ligands, (TMA)₂L1, (TMA)₂L2 and (TMA)₂L3, which differ in having zero, two and four tert-butyl groups, respectively, on the upper rim of the calix[4]arene scaffold were utilized for the spectrofluorimetric titration experiments in acetonitrile. On complexation by alkaline earth metal cations, both the absorption and emission spectra undergo marked red shifts and quenching of the dansyl fluorescence. These effects are weaker with alkali metal cations. Transition metal cations interact strongly with the ligands. In particular, Fe³⁺, Hg²⁺ and Pb²⁺ cause greater than 97% quenching of the dansyl fluorescence in the di-ionized ligands.     

Novel Solid‐Contact Ion‐Selective Microelectrodes for Localized Potentiometric Measurements

The design and properties of novel type of solid‐contact ionophore‐based ion‐selective microelectrodes are reported. The microelectrode is based on an insulated needle‐shaped metallic wire with an exposed apex. The ion‐to‐electron transducer is made of poly(3‐octylthiophene‐2,5‐diyl) and placed between an ion‐selective membrane and the metallic tip. The ion‐selective polyvinyl chloride‐based membrane is deposited atop the layer of conductive polymer. The length of the ion‐sensitive part of the electrode is less than 10 μm. pH and Mg²⁺‐selective microelectrodes were constructed and tested showing stable potential and fast response that are essential properties for the practical application of microelectrodes for localized scanning measurements.     

Nanocrystal superlattices with thermally degradable hybrid inorganic-organic capping ligands

Colloidal metallic and semiconductor nanocrystals (NCs) functionalized with metal chalcogenide complexes (MCCs) have shown a promise for designing materials that combine high carrier mobility with the electronic structure of strongly quantum-confined solids. Here we report a simple and general methodology for switching the repulsive forces responsible for colloidal stabilization of MCC-capped NCs from long-range electrostatic to short-range steric through the formation of tight ionic pairs with cationic surfactants. This noncovalent surface modification remarkably improved the ability of MCC-capped NCs to self-assemble into long-range ordered superlattices. These NCs are highly soluble in nonpolar solvents and compatible with various technologically relevant organic molecules and polymers. The hybrid inorganic-organic coating can be thermally decomposed at significantly lower temperatures compared to those required for removal of conventional organic ligands.     

A metal-organic framework functionalized with free carboxylic acid sites and its selective binding of a Cl(H2O)4(-) cluster

A metal-organic framework with one-dimensional channels decorated with -COOH binding sites was synthesized under aqueous acidic conditions, which inhibited the participation of these groups to metal coordination or self-association by hydrogen bonding. This material selectively includes Cl(H2O)4- clusters in its channels, as revealed by single-crystal X-ray diffraction analysis, which represents the first structural characterization of such a water-chloride cluster.     

Structural defects in periodic and quasicrystalline binary nanocrystal superlattices

Binary nanocrystal superlattices (BNSLs) emerge as an important class of man-made materials where components and functionalities can be added, tuned, or combined in a predictable manner. These amazingly complex structures spontaneously self-assemble from colloidal solutions containing binary mixtures of functional (semiconducting, magnetic, plasmonic, etc.) nanocrystals. Further developments of the BNSL-based materials require a deep understanding and control over BNSL formation and structural perfection. Like any solid, BNSL can contain different kinds of structural defects. It is well-known that defects can have a tremendous effect on the material's behavior. Defect engineering is used to modify and improve many of the mechanical, electrical, magnetic, and optical properties of conventional solids. In this work, we provide the first systematic analysis of structural defects in various BNSL structures. We used BNSLs as a platform for studying structural defects in both periodic (crystalline) and aperiodic (quasicrystalline) lattices, as well as for direct imaging of the interfaces between crystalline and quasicrystalline domains. Such direct observation of local imperfections in complex multicomponent lattices provides a unique insight into the fundamental aspects of crystal formation.