Ab initio molecular dynamics study of methanol adsorption on copper clusters

The preferential structures of small copper clusters Cun (n=2-9) and the adsorption of methanol molecules on these clusters are examined with first principles, molecular dynamics simulations. The results show that the copper clusters undergo systematic changes in bond length and bond order associated with altering their preferential structures from one-dimensional structures, to two-dimensional and three-dimensional structures. The results also indicate that low coordination number sites on the copper clusters are both the most favorable for methanol adsorption and have the greatest localization of electronic charge. The simulations predict that charge transfer between the neutral copper clusters and the incident methanol molecules is a key process by which adsorption is stabilized. Importantly, the changes in the dimensionality of the copper clusters do not significantly influence methanol adsorption.     

Bowl-shaped Cu(I) metallamacrocyclic ethylene and carbonyl adducts as structural analogues of organic calixarenes

Three novel Cu(I) metallacalixarenes with C(2)H(4) and CO legs, in which an anion is accommodated in the inside cavity, were self-assembled by anion templation and have been structurally characterized.     

How (77)Se NMR chemical shifts originate from pre-alpha, alpha, beta, and gamma effects: interpretation based on molecular orbital theory

Plain rules founded in a theoretical background are presented that can be used to determine the structure of selenium compounds on the basis of delta(Se) data and to predict delta(Se) data from a given structure with satisfactory accuracy. As a first step to establish such rules, the origin of delta(Se) is elucidated on the basis of MO theory. The Se(2-) ion was chosen as the standard for the analysis. The concept of the pre-alpha effect is proposed, which is defined as the downfield shift due to protonation of a lone-pair orbital of Se. The pre-alpha effect of two protons in H(2)Se is explained by the generation of double sigma(Se--H) and sigma*(Se--H) through protonation of the spherical Se(2-) ion. The orbitals, together with n(p)(Se), result in effective transitions for the pre-alpha effect. The alpha effect is the downfield shift caused by the replacement of Se--H by Se--Me. The extension of HOMO-2 [4p(y)(Se)], HOMO-1 [4p(x)(Se)], and HOMO [4p(z)(Se)] over the whole Me(2)Se molecule is mainly responsible for the alpha effect. The beta effect originates not from the occupied-to-unoccupied (psi(i)-->psi(a)) transitions but from the occupied-to-occupied (psi(i)-->psi(j)) transitions. Although psi(i)-->psi(j) transitions contribute to upfield shifts in Me(2)Se, the magnitudes become smaller as the methyl protons are substituted by Me groups one after another. The gamma effect of upfield shifts is also analyzed, although complex. The effect of p(Se)-pi(C==C) conjugation is analyzed in relation to the orientational effect. Contributions from each MO (psi(i)) and each psi(i)-->psi(a) transition are evaluated separately, by using a utility program derived from the Gaussian 03 program suite (NMRANAL-NH03G). The treatment enables us to visualize and understand the origin of (77)Se NMR chemical shifts.     

Synthesis of trifluoromethyl‐1,2,4‐triazine‐ and trifluoromethylpyrimidine‐fused uracils

A variety of trifluoromethyl‐1,2,4‐triazine‐ and trifluoromethylpyrimidine‐fused uracils ( 9 ), ( 12 ), ( 15 ) and ( 18 ) were synthesized from trifluoroacetaldehyde ethyl hemiacetal or trifluoroacetic anhydride and corresponding uracil derivatives.     

Rhodium-catalyzed substitution reaction of aryl fluorides with disulfides: p-orientation in the polyarylthiolation of polyfluorobenzenes

In the presence of a catalytic amount of RhH(PPh3)4 and 1,2-bis(diphenylphosphino)benzene, an aromatic fluoride, an organic disulfide (0.5 equiv), and triphenylphosphine (0.5 equiv) reacted in refluxing chlorobenzene to give an aryl sulfide in high yield. Since triphenylphosphine trapped fluoride atoms forming phosphine difluoride, both organothio groups of the disulfide reacted effectively, and the fluoride substituent reacted more readily than the chloride and bromide. The reaction of hexafluorobenzene and a diaryl disulfide gave 1,4-diarylthio-2,3,5,6-tetrafluorobenzene, 1,2,4,5-tetraarylthio-3,6-difluorobenzene, and hexaarylthiobenzene in a stepwise manner; pentafluorobenzene gave 1-arylthio-2,3,5,6-tetrafluorobenzene; 1,2,3,4-tetrafluorobenzene gave 1,2-diarylthio-3,6-difluorobenzene; and 1,2,4,5-tetrafluorobenzene gave 1,4-diarylthio-2-5-difluorobenzene. The polyarylthiolation reaction of polyfluorobenzenes exhibited a strong tendency to form 1,4-difluorobenzenes.     

Application and mechanism of inhalation profile improvement of DPI formulations by mechanofusion with magnesium stearate

In our previous paper, we reported the inhalation properties of dry powder inhaler (DPI) formulations containing Compound A and mechanofusion-processed lactose carriers. The mechanofusion process with magnesium stearate (Mg-St) on the lactose carrier enhanced the fine particle fraction (FPF) value of the Andersen cascade impactor (ACI) study. The increase of FPF seemed to be associated with the increase of the dispersibility of drug particles. The objectives of this study were (1) to evaluate the applicability of lactose carrier mechanofusion-processed with Mg-St and (2) to examine the mechanism of FPF alteration by the mechanofusion process applied on the lactose carrier with or without additive. The inhalation profiles of DPI formulations containing four different pharmaceutical compounds were evaluated with an ACI. The dispersibility of the formulations was observed by particle size distribution measurement in the air stream and the adhesive force was measured bydirect separation method. It was found that higher FPF was obtained with lactose mechanofusion-processed with Mg-St as compared to control lactose carriers for all four compounds. This suggested that mechanofusion process with Mg-St is widely applicable in DPI formulations. The homogenization of surface adhesiveness was attributed to the increased FPF of the DPI including lactose mechanofusion-processed with Mg-St, as suggested by the combination of several physicochemical characteristics. Combination of different characterization methods would be of help to clarify the whole mechanism which defines the inhalation properties of DPI formulations.     

Rhodium-catalyzed alkylthio exchange reaction of thioester and disulfide

The Wilkinson complex RhCl(PPh₃)₃ catalyzes equilibrating alkylthio exchange reaction of thioesters with disulfides. The treatment of a thioester and a dialkyl disulfide in refluxing diethyl ketone in the presence of RhCl(PPh₃)₃ (2.5 mol %) for 1.5 h gave an alkylthio exchanged thioester. The reaction of S-methyl ester was conducted shifting the equilibrium by removing volatile dimethyl disulfide.     

Micro- and nanopatterned copper structures using directed self-assembly on templates fabricated from phase-separated mixed Langmuir-Blodgett films

We report a versatile method to confine metal thin films in micro- and nanopatterns using directed self-assembly on the templates fabricated from phase-separated mixed Langmuir-Blodgett (LB) films. The pattern of the mixed LB films can be tuned by adjusting intermolecular interaction between the film-forming molecules in the LB films and by varying the fabrication conditions of the films such as the mixing ratio, subphase temperature, and surface pressure. We use the patterned LB films for templates to confine metal in patterned regions, taking advantage of the difference between the surface free energy of the patterned regions and that of the self-assembled monolayer of the silane coupling agent. Au nanoparticles are confined onto the patterned films as a catalyst for the succeeding Cu electroless deposition. The atomic force microscopic images, Auger electron spectra, and scanning Auger electron maps of a Cu-deposited film show that Cu is selectively deposited on the patterns of phase separation of the original mixed LB films.     

Use of reverse micelles to make either spherical or worm-like palladium nanocrystals: influence of stabilizing agent on nanocrystal shape

Depending on the water content, reverse micelles induce the formation of fcc metallic palladium worm-like nanocrystals made of spheres. After extraction from the nanoreactor, either spheres or worm-like nanocrystals are obtained, and it was found that the binding energy between the coating agent and the Pd surface is a key parameter in shape control (i.e., in the surface reconstruction).