Structure of Glancing Incidence Deposited TiO2 Thin Films as Revealed by Grazing Incidence Small‐Angle X‐ray Scattering

For the first time, grazing incidence small‐angle X‐ray scattering (GISAXS) analysis is used to characterize the morphology of TiO₂ thin films grown by glancing angle physical vapor deposition (GLAD). According to cross‐section scanning electron microscopy (SEM) images, the films consist of near isotilted TiO₂ columns of different length and width depending on film thickness. The obtained GISAXS patterns show a characteristic asymmetry with respect to the incidence plane, which is associated with the tilted geometry of the TiO₂ columns. The patterns also show the existence of two populations of columns in these GLAD‐TiO₂ films. The population of the thinnest columns appears related to the first grown layer and is common for all the films investigated, while the second population of columns grows with the thickness of the films and has been related to wider columns formed by shadowing at the expense of the initially formed columns.     

On the nature of the transition metal-main group metal bond: synthesis and theoretical calculations on iridium gallyl complexes

The iridum-gallyl complex MeIr(PCy(3))(2)(GaMe(2))(Cl*GaMe(3)) exhibits a short Ir-Ga bond length of 2.381(1)-2.389(2) ?. Theoretical calculations (ZORA BP86/TZ2P) support the presence of a Ir-Ga single bond but highlight a π orbital contribution.     

High‐Oxidation‐State Palladium Catalysis: New Reactivity for Organic Synthesis

Recent years have seen the rapid development of a new field of palladium catalysis in organic synthesis. This chemistry takes place outside the usually encountered Pd⁰/Pd^II cycles. It is characterized by the presence of strong oxidants, which prevent further palladium(II)‐promoted reactions at a given point of the catalytic cycle by selective metal oxidation. The resulting higher‐oxidation‐state palladium complexes have been used to develop a series of new synthetic transformations that cannnot be realized within conventional palladium catalysis. This type of catalysis by palladium in a higher oxidation state is of significant synthetic potential.     

Gold(I)-catalyzed cyclizations of 1,6-enynes: alkoxycyclizations and exo/endo skeletal rearrangements

Gold(I) complexes are the most active catalysts for alkoxy- or hydroxycyclization and for skeletal rearrangement reactions of 1,6-enynes. Intramolecular alkoxycyclizations also proceed efficiently in the presence of gold(I) catalysts. The first examples of the skeletal rearrangement of enynes by the endocyclic cyclization pathway are also documented. Iron(III) is also able to catalyze exo and endo skeletal rearrangements of 1,6-enynes, although the scope of this transformation is more limited. The gold(I)-catalyzed endocyclic cyclization proceeds by a mechanism different from those followed in the presence of PdII, HgII, or RhI catalysts.     

Acidic solution properties of beta-casein-graft-dextran copolymer prepared through Maillard reaction

The copolymer of beta-casein-graft-dextran was prepared using the Maillard reaction and the acidic solution properties of the copolymer were studied with dynamic light scattering. At pH range 4-5 where is close to the isoelectric point of beta-casein, the copolymer forms micelles which are spherical verified by atomic force microscopy imaging. The size and existent time of the micelles depend on the graft degree and the length of dextran side chains of the copolymers. During storage at pH 4.6, the micelles formed by the copolymers with short side chains and low graft degree tend to precipitate, while the micelles formed by the copolymers with long side chains and high graft degree tend to dissociate. The micellization of the copolymers can be suppressed by adding NaCl. Optical microscopy and turbidity studies show that the copolymers dissolved in molecular state and with higher hydrophilicity have better emulsifying ability.     

Creating polymer structures of tunable electric functionality by nanoscale discharge-assisted cross-linking and oxygenation

We report the creation of polymeric micro/nanostructures which exhibit distinct chemical and physical characteristics from the matrix poly(N-vinyl carbazole) (PVK). The structure formation is based on atomic force microscopy (AFM) facilitated cross-linking and oxygenation. The reaction of PVK with AFM lithographically induced nanoscale discharge produces raised structures in which bridge oxygen links neighboring carbazole groups. The cross-linking by bridge oxygen converts the initially insulating PVK matrix to chemically modified conducting patterns through the formation of extended pi-conjugations. A comprehensive AFM, PES (photoelectron spectroscopy), FTIR (Fourier transform infrared spectroscopy), and DFT (density functional theory) analysis is presented to address the chemophysical identity of the patterned structures. Our results demonstrate new capabilities of AFM nanolithography in generating heterogeneous functional structures in a polymer matrix.     

The hydration of Cu2+: Can the Jahn-Teller effect be detected in liquid solution?

The long elusive structure of Cu(II) hydrate in aqueous solutions, classically described as a Jahn-Teller distorted octahedron and recently proposed to be a fivefold coordination structure [Pasquarello et al., Science 291, 856 (2001)], has been probed with x-ray-absorption spectroscopy by performing a combined theoretical and experimental analysis. Two absorption channels were needed to obtain a proper reproduction of the x-ray-absorption near-edge structure (XANES) region spectrum, as already observed in other Cu(II) complexes [Chaboy et al., Phys. Rev. B 71, 134208 (2005)]. The extended x-ray-absorption fine-structure (EXAFS) spectrum was analyzed as well within this approach. Quite good reproductions of both XANES and EXAFS spectra were attained for several distorted and undistorted structures previously proposed. Nevertheless, there is not a clearly preferred structure among those including four-, five-, and sixfold coordinated Cu(II) ions. Taking into account our results, as well as many more from several other authors using different techniques, the picture of a distorted octahedron for the Cu(II) hexahydrate in aqueous solution, paradigm of the Jahn-Teller effect, is no longer supported. In solution a dynamical view where the different structures exchange among themselves is the picture that better suits the results presented here.