Ordered mesoporous silica with large cage-like pores: structural identification and pore connectivity design by controlling the synthesis temperature and time

FDU-1 silicas with large cage-like pores (diameter about 10 nm) were synthesized under acidic conditions from tetraethyl orthosilicate in the presence of a poly(ethylene oxide)-poly(butylene oxide)-poly(ethylene oxide) triblock copolymer template B50-6600 (EO(39)BO(47)EO(39)). High-resolution transmission electron microscopy and small-angle X-ray scattering provided strong evidence that FDU-1 silica synthesized under typical conditions is a face-centered cubic Fm3m structure with 3-dimensional hexagonal intergrowth and is not a body-centered cubic Im3m structure, as originally reported. Samples synthesized in a wide range of conditions (initial temperatures from 298 to 353 K; hydrothermal treatment at 333-393 K) exhibited similar XRD patterns and their nitrogen adsorption isotherms indicated a good-quality cage-like pore structure. The examination of low-pressure nitrogen adsorption isotherms for FDU-1 samples, whose pore entrance diameters were evaluated using an independent method, allowed us to conclude that low-pressure adsorption was appreciably stronger for samples with smaller pore entrance sizes. This prompted us to examine low-pressure adsorption isotherms for a wide range of samples and led us to a conclusion that the FDU-1 pore entrance size can be systematically enlarged from about 1.3 nm (perhaps even lower) to at least 2.4 nm without an appreciable loss of uniformity by increasing the temperature of the hydrothermal treatment or the initial synthesis. Further enlargement of pore entrance size was achieved for sufficiently long hydrothermal treatment times at temperatures of 373 K or higher, as seen from the shape of nitrogen desorption isotherms. This allowed us to obtain samples with uniform pore sizes, high adsorption capacity, and with pore entrances enlarged so much that their size was similar to the size of the pore itself, resulting in a highly open porous structure. However, in the latter case, there was evidence that the pore entrance size distribution was quite broad.     

Biaryl synthesis from two different aryl halides with tri(2-furyl)germane

[reaction: see text] The coupling reaction of germanium compounds with aryl halides has been developed. The Pd(0)-catalyzed reaction of aryl halides with tri(2-furyl)germane provides aryltri(2-furyl)germanes in good yield. The cross-coupling reaction of aryltri(2-furyl)germanes with aryl halides is achieved. This allows facile synthesis of unsymmetrical biaryls from two different aryl halides.     

Oxygen atom transfer reactions from dioxygen to phosphines via a bridging sulfur dioxide in a trinuclear cluster complex of rhenium, [(Ph(3)P)(2)N][Re(3)(mu(3)-S)(mu-S)(2)(mu-SO(2))Cl(6)(PMe(2)Ph)(3)

A trinuclear rhenium sulfide cluster complex, [(Ph(3)P)(2)N][Re(3)(mu(3)-S)(mu-S)(3)Cl(6)(PMe(2)Ph)(3)], synthesized from Re(3)S(7)Cl(7), dimethylphenylphosphine, and [(Ph(3)P)(2)N]Cl is readily converted to a bridging SO(2) complex, [(Ph(3)P)(2)N][Re(3)(mu(3)-S)(mu-S)(2)(mu-SO(2))Cl(6)(PMe(2)Ph)(3)], by reaction with O(2). The oxygen atoms on the SO(2) ligand react with phosphines or phosphites to form phosphine oxides or phosphates, and the original cluster complex is recovered. The reaction course has been monitored by (31)P NMR as well as by UV-vis spectroscopy. The catalytic oxygenation of PMePh(2) in the presence of the SO(2) complex shows that turnovers are 8 per hour at 23 degrees C in CDCl(3). The X-ray structures of the cluster complexes are described.     

Magnetic phase transition in a heteromolecular hydrogen-bonded complex of nitronylnitroxide radicals

An organic molecular acid-base complex has been synthesized from pyridine-substituted biradical 2 in a triplet (S = 1) ground state and a benzoic acid derivative of monoradical 3 with S = 1/2. The two constituent molecules are bound by an OH-N hydrogen bond in a crystalline solid state. The complex has been found to exhibit an antiferromagnetic phase transition at 5 K. The complex is the first example of a hydrogen-bonded heterospin, heteromolecular complex exhibiting a magnetic phase transition in purely organic molecule-based materials.     

Synthesis of Polycyclic and Cage Siloxanes by Hydrolysis and Intramolecular Condensation of Alkoxysilylated Cyclosiloxanes

The controlled synthesis of oligosiloxanes with well-defined structures is important for the bottom-up design of siloxane-based nanomaterials. This work reports the synthesis of various polycyclic and cage siloxanes by the hydrolysis and intramolecular condensation of monocyclic tetra- and hexasiloxanes functionalized with various alkoxysilyl groups. An investigation of monoalkoxysilylated cyclosiloxanes revealed that intramolecular condensation occurred preferentially between adjacent alkoxysilyl groups to form new tetrasiloxane rings. The study of dialkoxy- and trialkoxysilylated cyclotetrasiloxanes revealed multistep intramolecular condensation reactions to form cubic octasiloxanes in relatively high yields. Unlike conventional methods starting from organosilane monomers, intramolecular condensation enables the introduction of different organic substituents in controlled arrangements. So-called Janus cubes have been successfully obtained, that is, Ph₄R₄Si₈O₁₂, in which R=Me, OSiMe₃, and OSiMe₂Vi (Vi=vinyl). These findings will enable the creation of siloxane-based materials with diverse functions.     

Algorithms to retrieve optical properties of three component aerosols from two-wavelength backscatter and one-wavelength polarization lidar measurements considering nonsphericity of dust

We developed backward and forward types of algorithms for estimating the vertical profiles of extinction coefficients at 532 nm for three component aerosols (water-soluble, dust, and sea salt) using three-channel Mie-scattering lidar data of the backscatter (β) at 532 and 1064 nm and the depolarization ratio (δ) at 532 nm. While the water-soluble and sea-salt particles were reasonably assumed to be spherical, the dust particles were treated as randomly oriented spheroids to account for their nonsphericity. The introduction of spheroid models enabled us to more effectively use the three-channel data (i.e., 2β+1δ data) and to reduce the uncertainties caused by the assumption of spherical dust particles in our previously developed algorithms. We also performed an extensive sensitivity study to estimate retrieval errors, which showed that the errors in the extinction coefficient for each aerosol component were smaller than 30% (60%) for the backward (forward) algorithm when the measurement errors were ±5%. We demonstrated the ability of the algorithms to partition aerosol layers consisting of three aerosol components by applying them to shipborne lidar data. Comparisons with sky radiometer measurements revealed that the retrieved optical thickness and angstrom exponent of aerosols using the algorithms developed in this paper agreed well with the sky radiometer measurements (within 6%).     

Octapalladium Strings Trap C60 and C70 Fullerenes Affording Metal-Chain-Wired Bucky Balls

Reactions of Pd₈ strings supported by meso-Ph₂PCH₂P(Ph)CH₂P(Ph)CH₂PPh₂ (meso-dpmppm) ligands, [Pd₈(meso-dpmppm)₄(L)₂]⁴⁺ (L=CH₃CN ( 1 ), XylNC ( 2 )) with C₆₀ resulted in the exclusive formation of unprecedented metal-chain-wired C₆₀ bucky balls, [{Pd₄(meso-dpmppm)₂(L)}₂(C₆₀)]⁴⁺ (L=CH₃CN ( 11 ), XylNC ( 12 )), in which a C₆₀ fullerene is trapped in the central Pd–Pd junction, as unambiguously established by spectroscopic, X-ray crystallographic, and theoretical techniques. The similar reaction of Pd₈ strings supported by rac-dpmppm, [Pd₈(rac-dpmppm)₄(CH₃CN)₂]⁴⁺ ( 3 ) also afforded a racemic mixture of [{Pd₄((R*,R*)-dpmppm)₂(CH₃CN)}₂(C₆₀)]⁴⁺ ( 13 ) without scrambling the Pd₄ fragments with (R,R)- and (S,S)-dpmppm ligands. Consequently, those of enantiopure chiral Pd₈ strings, [Pd₈((R*,R*)-dpmppm)₄(CH₃CN)₂]⁴⁺, certainly afforded chiral bucky balls of [{Pd₄((R*,R*)-dpmppm)₂(CH₃CN)}₂(C₆₀)]⁴⁺ ( 13 _RR and 13 _SS ), that exhibit mirror-image circular dichroism spectra. The reactions of 1 and 2 were also applied for trapping a C₇₀ fullerene to give 2 : 1 adducts of [{Pd₄(meso-dpmppm)₂(L)}₂(C₇₀)]⁴⁺ (L=CH₃CN ( 21 ), XylNC ( 22 )). These results provide useful information for creating a platform to develop dimensionally and chirality controlled metal–carbon nanocomposite materials.     

Synthesis and properties of novel fluorinated subnaphthalocyanines for organic photovoltaic cells

Novel fluorinated subnaphthalocyanine derivatives were newly designed and synthesized as donor materials for low molecular organic photovoltaic cells using fullerene as an acceptor. They were designed to have the low-lying HOMO energy levels for improvement of open circuit voltage without any expense of short-circuit current density. The HOMO/LUMO energy levels of hexafluoro-, heptafluoro-, dodecafluoro-, tridecafluoro- and the parent subnaphthalocyanine estimated based on the photoelectron spectroscopy were −5.69/−3.93, −5.67/−3.90, −5.96/−4.19, −5.92/−4.11 and −5.30/−3.58 eV, respectively, showing that frontier orbital energy levels can be effectively tuned by fluorination.