Nanoscale self-hosting of molecular spin-states in the intermediate phase of a spin-crossover material

A new spin-crossover (SC) complex [Fe(II)H(2)L(2-Me)][AsF(6)](2) has been synthesized, in which H(2)L(2-Me) denotes the chirogenic hexadentate N(6) Schiff-base ligand bis{[(2-methylimidazol-4-yl)methylidene]-3-aminopropyl}ethylenediamine. This complex has revealed a rich variety of phases during its two-step thermal crossover, as well as photoinduced spin-state switching. A high-symmetry high-spin (HS, S=2) phase, a low-symmetry low-spin (LS, S=0) phase, an intermediate phase characterized by an unprecedented lozenge pattern of 12 predominantly HS molecular crystallographic sites confining 18 predominantly LS molecular crystallographic sites, and a photoinduced low-symmetry HS phase have been accurately evidenced by temperature-dependent magnetic susceptibility, M?ssbauer spectroscopy, and crystallographic studies. This variety of phases illustrates the multi-stability of this system, which results from coupling between the electronic states and structural instabilities.     

Anisotropic polymerization of a long-chain diacetylene derivative Langmuir-Blodgett film on a step-bunched SiO2/Si surface

Alternating facet/terrace nanostructures were fabricated on a SiO2 surface by step-bunching and thermal oxidation of a vicinal Si(111) substrate, and their influence upon the polymerization direction of a long-chain diacetylene derivative monolayer film was investigated by angle-dependent polarized near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. It was found that the peak intensity of the C 1s-pi transition was stronger when the electric vector plane of the incident X-ray was parallel to the direction of the periodic facet/terrace structures rather than perpendicular to them. On the contrary, a polymer film fabricated on a flat SiO2 surface showed no in-plane anisotropy of the peak intensity. These results indicate that the diacetylene groups in the diacetylene derivative monolayer are preferentially photopolymerized in the direction not across but along the periodic one-dimensional structures on the step-bunched and thermally oxidized SiO2/Si(111) surface.     

Efficient C-N bond formations catalyzed by a proton-exchanged montmorillonite as a heterogeneous Brønsted acid

Nucleophilic addition of sulfonamides and carboxamides to simple alkenes proceeded smoothly using a proton-exchanged montmorillonite catalyst. The spent catalyst was recovered easily from the reaction mixture and was reusable at least five times without any loss of activity. The unique acidity of the proton-exchanged montmorillonite (H-mont) catalyst was found to be applicable to additional reactions: substitution of hydroxyl groups of alcohols with amides and anilines.     

Nickel-catalyzed reactions of silacyclobutanes with aldehydes: ring opening and ring expansion reaction

[reaction: see text]. The nickel-catalyzed ring opening reaction of silacyclobutanes with aldehydes affords the corresponding alkoxyallylsilanes. In contrast, the ring expansion reaction of benzosilacyclobutene with aldehydes occurs under nickel catalysis to give oxasilacyclohexenes.     

MassBank: a public repository for sharing mass spectral data for life sciences

MassBank is the first public repository of mass spectra of small chemical compounds for life sciences (<3000 Da). The database contains 605 electron‐ionization mass spectrometry(EI‐MS), 137 fast atom bombardment MS and 9276 electrospray ionization (ESI)‐MSⁿ data of 2337 authentic compounds of metabolites, 11 545 EI‐MS and 834 other‐MS data of 10 286 volatile natural and synthetic compounds, and 3045 ESI‐MS² data of 679 synthetic drugs contributed by 16 research groups (January 2010). ESI‐MS² data were analyzed under nonstandardized, independent experimental conditions. MassBank is a distributed database. Each research group provides data from its own MassBank data servers distributed on the Internet. MassBank users can access either all of the MassBank data or a subset of the data by specifying one or more experimental conditions. In a spectral search to retrieve mass spectra similar to a query mass spectrum, the similarity score is calculated by a weighted cosine correlation in which weighting exponents on peak intensity and the mass‐to‐charge ratio are optimized to the ESI‐MS² data. MassBank also provides a merged spectrum for each compound prepared by merging the analyzed ESI‐MS² data on an identical compound under different collision‐induced dissociation conditions. Data merging has significantly improved the precision of the identification of a chemical compound by 21–23% at a similarity score of 0.6. Thus, MassBank is useful for the identification of chemical compounds and the publication of experimental data. Copyright © 2010 John Wiley & Sons, Ltd.     

Copper hydroperoxo species activated by hydrogen-bonding interaction with its distal oxygen

A novel copper(II)[bond]OOH complex with functional ligand that can form a hydrogen bond with the distal oxygen of hydroperoxide has been designed and prepared as a structural/functional model of dopamine beta-hydroxylases, whose spectroscopic characterization and decomposition rates have indicated that the hydroperoxide is activated through the hydrogen-bonding interaction with the distal oxygen.