Exceptionally strong Bragg diffraction from a mesoporous silica film pretreated with chlorotrimethylsilane toward application in X-ray optics

Exceptionally strong Bragg diffraction from a mesoporous silica film is achieved by exposing the as-deposited film to vapor of chlorotrimethylsilane (Me(3)SiCl) before extracting the surfactant. The intensity of the X-ray diffraction peak increased 7 times after the surfactant removal and it approached 30% reflectivity. This large increase of diffraction intensity cannot be explained simply by the improved contrast of the electron density, and rearrangement of the pore wall during the Me(3)SiCl vapor treatment is suggested. It is shown by infrared spectroscopy that Me(3)SiCl with a high grafting reactivity effectively caps the silanol groups and prevents the following condensation, which causes the structural degradation. The substitution of the hydrogen atom of hydroxyl groups with trimethylsilyl groups should help the improvement of the structural regularity by reducing the hydrogen bonds in the pore wall. The achieved strong diffraction opens the gate for the application of these regular mesoporous films prepared by a self-assembly process to optical elements in the X-ray region.     

Optical resolution of aromatic alcohols using silica nanoparticles grafted with helicene

Optically active silica nanoparticles, with a 70-nm diameter, grafted with (P)-1,12-dimethyl-8-methoxycarbonylbenzo[c]phenanthrene-5-carboxyamide were synthesized, and their use in the kinetic resolution of aromatic alcohols was examined. Up to 61% ee for (S)-2,2-dimethyl-1-phenyl-1-propanol was obtained by a preferential precipitation of aggregates formed with (P)-nanoparticles.     

Synthesis, Stability, and Photoluminescence Properties of PdAu10(PPh3)8Cl2 Clusters

We report on the synthesis, stability, and photoluminescence (PL) properties of triphenylphosphine (PPh₃)-stabilized PdAu₁₀(PPh₃)₈Cl₂ cluster, which is a mono-Pd-doped cluster of the well-studied Au₁₁(PPh₃)₈Cl₂ cluster. The PdAu₁₀(PPh₃)₈Cl₂ cluster was synthesized by simultaneously reducing two different metal complexes; AuCl(PPh₃) and Pd(PPh₃)₄. Experimental evaluation of the stability showed that PdAu₁₀(PPh₃)₈Cl₂ is more stable against degradation in solution than the monometal Au₁₁(PPh₃)₈Cl₂ cluster. PL measurements revealed that PdAu₁₀(PPh₃)₈Cl₂ exhibits PL at 950?nm with a quantum yield of 1.5?×?10^?3, which has not been observed for the monometal Au₁₁(PPh₃)₈Cl₂ cluster. The results indicate that Pd doping is a powerful method to produce clusters with higher stability and different physical properties than the monometal Au:PPh₃ clusters.     

Palladium doping of magic gold cluster Au38(SC2H4Ph)24: formation of Pd2Au36(SC2H4Ph)24 with higher stability than Au38(SC2H4Ph)24

A phenylethanethiolate-protected Pd(2)Au(36)(SC(2)H(4)Ph)(24) cluster, which is a two-Pd atom-doped cluster of the well studied magic gold cluster Au(38)(SC(2)H(4)Ph)(24), was synthesized in high purity and its stability was investigated. The results demonstrate that Pd(2)Au(36)(SC(2)H(4)Ph)(24) is more stable than Au(38)(SC(2)H(4)Ph)(24) against degradation in solution and core etching by thiols.     

Non-centrosymmetric coordination polymer with a highly hindered octahedral copper center bridged by mandelate

A novel chiral coordination polymer, [Cu(C(6)H(5)CH(OH)COO)(μ-C(6)H(5)CH(OH)COO)] (1-L and 1-D), was synthesized through a reaction of copper acetate with L-mandelic acid at room temperature. Although previously reported copper mandelate prepared by hydrothermal reaction was a centrosymmetric coordination polymer because of the racemization of mandelic acid, the current coordination polymer shows noncentrosymmetry and a completely different structure from that previously reported. The X-ray crystallography for 1-L revealed that the copper center of the compound showed a highly distorted octahedral structure bridged by a chiral mandelate ligand in the unusual coordination mode to construct a one-dimensional (1D) zigzag chain structure. These 1D chains interdigitated each other to give a layered structure as a result of the formation of multiple aromatic interactions and hydrogen bonds between hydroxyl and carboxylate moieties at mandelate ligands. The coordination polymer 1-L belongs to the noncentrosymmetric space group of C2 to show piezoelectric properties and second harmonic generation (SHG) activity.     

A dendron of subphthalocyanine trefoil

The synthesis of a dendron composed of tetrameric subphthalocyanine (SubPc) is accomplished by substituting the chlorine groups with phenoxy groups at the axial positions of SubPc with SubPc-triol. The present molecular design of the SubPc-triol introduces three phenol groups at the peripheral positions of the SubPc macrocycle as a tritopic template to construct SubPc dendrons. The self-polycondensation of SubPc-triol as a ‘divergent’ synthesis only gave a trace amount of the hyperbranched arrays due to poor solubility of the SubPc-triol. In contrast, a ‘convergent’ synthesis with the terminal SubPc improved the solubility throughout the reaction and a tetrameric SubPc dendron was obtained in moderate isolated yield.     

Rate of interfacial electron transfer through the 1,2,3-triazole linkage

The rate of electron transfer is measured to two ferrocene and one iron tetraphenylporphyrin redox species coupled through terminal acetylenes to azide-terminated thiol monolayers by the Cu(I)-catalyzed azide-alkyne cycloaddition (a Sharpless "click" reaction) to form the 1,2,3-triazole linkage. The high yield, chemoselectivity, convenience, and broad applicability of this triazole formation reaction make such a modular assembly strategy very attractive. Electron-transfer rate constants from greater than 60,000 to 1 s(-1) are obtained by varying the length and conjugation of the electron-transfer bridge and by varying the surrounding diluent thiols in the monolayer. Triazole and the triazole carbonyl linkages provide similar electronic coupling for electron transfer as esters. The ability to vary the rate of electron transfer to many different redox species over many orders of magnitude by using modular coupling chemistry provides a convenient way to study and control the delivery of electrons to multielectron redox catalysts and similar interfacial systems that require controlled delivery of electrons.     

Coordination bond formation at charge-transfer phase transition in (BDTA)2[Co(mnt)2

The crystal structure of a charge-transfer salt, (BDTA)2[Co(mnt)2], where BDTA is 1,3,2-benzodithiazolyl and mnt is maleonitriledithiolate, consisted of an alternating stacking column of a head-to-head BDTA+ dimer and a planar [Co(mnt)2]2- dianion at 253 K. Magnetic measurements and structural analyses revealed a phase transition at 190 K, where a partial electron transfer occurred from [Co(mnt)2]2- to one of the BDTA+ cations, forming a coordination bond between the two.     

Synthesis of Orthorhombic Mo‐V‐Sb Oxide Species by Assembly of Pentagonal Mo6O21 Polyoxometalate Building Blocks

Mix and match : The pentagonal [Mo₆O₂₁]^n? polyoxomolybdate building block assembles with other sources of Mo, V, and Sb ions to form an orthorhombic Mo‐V‐Sb oxide. The first single‐crystal X‐ray analysis of an orthorhombic Mo–V‐based oxide, a promising catalyst for light alkane selective oxidation known as the “M1 phase”, revealed the structure of the compound.