A mixed-bridging ligand nonanuclear Ru(II) dendrimer containing a tris- chelating core. Synthesis and redox properties

The first ligand-cored dendrimer based on branching Ru(II) centers and containing mixed polypyridine bridging ligands has been prepared; redox experiments suggest that the redox-active core is not reduced at the expected potential, probably as a consequence of shielding induced by the rigid dendritic array.     

Expanded Pyridiniums: Bis‐cyclization of Branched Pyridiniums into Their Fused Polycyclic and Positively Charged Derivatives—Assessing the Impact of Pericondensation on Structural,Electrochemical, Electronic,and Photophysical Features

This study evaluates the impact of the extension of the π‐conjugated system of pyridiniums on their various properties. The molecular scaffold of aryl‐substituted expanded pyridiniums (referred to as branched species) can be photochemically bis‐cyclized into the corresponding fused polycyclic derivatives (referred to as pericondensed species). The representative 1,2,4,6‐tetraphenylpyridinium ( 1^H ) and 1,2,3,5,6‐pentaphenyl‐4‐(p‐tolyl)pyridinium ( 2^Me ) tetra‐ and hexa‐branched pyridiniums are herein compared with their corresponding pericondensed derivatives, the fully fused 9‐phenylbenzo[1,2]quinolizino[3,4,5,6‐def]phenanthridinium ( 1^H f ) and the hitherto unknown hemifused 9‐methyl‐1,2,3‐triphenylbenzo[h]phenanthro[9,10,1‐def]isoquinolinium ( 2^Me f ). Combined solid‐state X‐ray crystallography and solution NMR experiments showed that stacking interactions are barely efficient when the pericondensed pyridiniums are not appropriately substituted. The electrochemical study revealed that the first reduction process of all the expanded pyridiniums occurs at around ?1 V vs. SCE, which indicates that the lowest unoccupied molecular orbital (LUMO) remains essentially localized on the pyridinium core regardless of pericondensation. In contrast, the electronic and photophysical properties are significantly affected on going from branched to pericondensed pyridiniums. Typically, the number of absorption bands increases with extended activity towards the visible region (down to ca. 450 nm in MeCN), whereas emission quantum yields are increased by three orders of magnitude (at ca. 0.25 on average). A relationship is established between the observed differential impact of the pericondensation and the importance of the localized LUMO on the properties considered: predominant for the first reduction process compared with secondary for the optical and photophysical properties.     

Two-dimensional liquid chromatography/mass spectrometry/mass spectrometry separation of water-soluble metabolites

Off-line two-dimensional liquid chromatography with tandem mass spectrometry detection (2D-LC/MS-MS) was used to separate a set of metabolomic species. Water-soluble metabolites were extracted from Escherichia coli and Saccharomyces cerevisae cultures and were immediately analyzed using strong cation exchange (SCX)-hydrophilic interaction chromatography (HILIC). Metabolite mixtures are well-suited for multidimensional chromatography as the range of components varies widely with respect to polarity and chemical makeup. Some currently used methods employ two different separations for the detection of positively and negatively ionized metabolites by mass spectrometry. Here we developed a single set of chromatographic conditions for both ionization modes and were able to detect a total of 141 extracted metabolite species, with an overall peak capacity of ca. 2500. We show that a single two-dimensional separation method is sufficient and practical when a pair or more of unidimensional separations are used in metabolomics.     

Conical parametric scattering of a single extraordinary beam in BaTiO3 crystal

In this paper, the parametric scattering of a single extraordinary polarized beam of laser in BaTiO₃ photorefractive crystal has been investigated experimentally and theoretically. The resulting pattern consists of beam fanning, isotropic ring, and anisotropic one. Among all parts of scattering pattern, isotropic ring has not been studied as much as beam fanning and anisotropic ring, and there still are some differences in reports about it. Therefore, the study has mainly focused on this part. In this experimental configuration, isotropic ring is just visible in positive angles although the other parts of parametric scattering pattern can be visible from behind and in front of the crystal. In addition to steady state pattern in forward and backward directions, its transient behavior with the rotation of crystal has been studied. The results of experiments have been analyzed carefully, and their theoretical explanations have been presented based on the standard theory of parametric scattering in photorefractive crystals. It has been shown that this configuration corresponds to the so called parametric B-process scattering.     

Dinuclear Ru(II) complexes of bis-(dipyrid-2'-yl)triazine (bis-dpt) ligands as efficient electron reservoirs

A planar bis-dipyrid-2'-yltriazine (bis-dpt) bridging ligand forms dinuclear Ru(II) complexes able to store up to eight electrons upon electrochemical reduction.     

Hole lifetime and chemical shift of the 4f levels in Yb metal

UHV photoemission studies of Yb metal are reported using synchrotron radiation in the photon energy range 25 < hv < 180 eV, whereby maximum surface sensitivity can be reached. The 4f photoemission spectrum shows a quadruplet structure owing to a superposition of two 4f spin—orbit doublets. One doublet has a very asymmetric lineshape and an extremely narrow lifetime linewidth 2γ? 0.013 eV; this is attributed to bulk emission. The other doublet exhibits almost symmetric lines with a much larger linewidth (0.43 eV FWHM); it has also a larger binding energy by 0.6 ± 0.03 eV. This is attributed as being due to chemically bound Yb atoms located at the surface. The implications of these findings on recent high-resolution photoemission studies of rare earth (RE) metals and their analysis are considered.     

Spin polarized energy-resolved photoemission from Ni(111) using synchrotron radiation

We report on the first energy-resolved (retarding field mode) spin polarized photoemission measurement from a Ni(111) single crystal using synchrotron radiation from the ACO storage ring at LURE(ORSAY) It is shown that exchange effects can be detected for electron states well below the Fermi energy and that spin polarized, constant-initial-state spectroscopy of ferromagnets using synchrotron radiation is feasible.     

Bragg reflection and isochromat spectroscopy of electrons from a magnetic single crystal surface: Novel polarization detectors?

Two effects, Bragg reflection and isochromat spectroscopy of electrons from a magnetic single crystal surface are proposed as candidates for a low energy spin polarization detector. A qualitative estimate shows that besides Fe or Ni a Gd single crystal surface might be a good choice for testing both effects.