Directed synthesis of noncentrosymmetric molybdates using composition space analysis

A systematic investigation of the factors governing the reaction product composition, hydrogen bonding, and symmetry was conducted in the MoO3/3-aminoquinuclidine/H2O system. Composition space analysis was performed through 36 individual reactions under mild hydrothermal conditions using racemic 3-aminoquinuclidine. Single crystals of three new compounds, [C7H16N2][Mo3O10] x H2O, [C7H16N2]2[Mo8O26] x H2O, and [C7H16N2]2[Mo8O26] x 4 H2O, were grown. The relative phase stabilities for these products are dependent upon the reactant mole fractions in the initial reaction gel. This phase stability information was used to direct the synthesis of two new noncentrosymmetric compounds, using either (S)-(-)-3-aminoquinuclidine dihydrochloride or (R)-(+)-3-aminoquinuclidine dihydrochloride. [(R)-C7H16N2]2[Mo8O26] and [(S)-C7H16N2]2[Mo8O26] both crystallize in the noncentrosymmetric space group P2(1) (No. 4), which has the polar crystal class 2 (C2). The second-harmonic generation activities were measured on sieved powders. The structure-directing properties of the molybdate components in each compound were determined using bond valence sums. The structures of all five compounds were determined using single-crystal X-ray diffraction.     

Porphyrins bearing stable meso-alkylidenyl double bonds. A new family of nonplanar porphyrinoids

[Structure: see text] Unique core-modified porphyrinoids, such as oxabenziporphyrins, oxapyriporphyrins, and thiapyriporphyrins, bearing exocyclic C-C double bonds at meso-positions, have been synthesized and characterized. The synthesis was accomplished by utilizing typical "3+1"-type condensation. Two different stable tautomeric forms were isolated, and the two tautomeric forms can be interconvertible upon treatment with base. In contrast, only the structure bearing an exocyclic double bond was isolated in the case of oxapyriporphyrin and oxabenziporphyrin.     

Dielectric force and relative motion between two spherical particles in electrophoresis

When two particles close to each other are in electrophoretic motion, each particle is under the influence of the nonuniform electric field generated by the other particle. Two particles may attract or repel each other due to the dielectric force, depending on their positions in the nonuniform electric field. In this work, the dielectric interaction and the subsequent relative motion of the two arbitrarily oriented spherical particles are analyzed. The dielectric force is obtained by integrating the Maxwell stress. The result is valid for arbitrary orientations of the particles under the thin electrical-double-layer assumption. The magnitude of the dielectric force is compared to the so-called inertia-induced force, which shows that the dielectric force is normally much greater than the inertia-induced force. The relative velocity of particles is determined by the force balance between the dielectric force and the Stokes drag. The regions of attraction and repulsion are defined. It is shown that a pair of particles eventually aligns parallel to the externally applied electric field, except in the case where the two particles are initially oriented perpendicular to the electric field. A closed-form analytical solution is obtained for the particle trajectory by using the approximate expression for the dielectric force valid for not-too-closely located particles.     

Novel Water‐Soluble Shape‐Regulatable Luminescent Nanoparticles by Non‐Covalently Bonded Self‐Assembly

Summary: Novel non‐covalently connected water‐soluble nanoparticles that contain poly(fluorene‐co‐phenylene) with hydroxy‐capped alkoxy side chains (PF3BOH) and poly(acrylic acid) (PAA) have been obtained and characterized. With different proportions of PF3BOH and PAA, the shape and size of the nanoparticles can be regulated. The nanoparticles are quite stable in water with no precipitate being observed after weeks. Transmission electron microscopy and dynamic laser light scattering are used to confirm the morphology of the PF3BOH/PAA nanoparticles. Their optical properties have been investigated and show similar optoelectronic properties to a PF3BOH solid film although they do not undergo aggregation.

TEM images of the nanoparticles obtained upon varying the PAA/PF3BOH content.     

Hollow-Fiber Ultrafiltration then Centrifugation for LC Analysis of Water-Soluble Sucrose in a Water-Soluble High-Molecular-Mass Gel Matrix

A novel, simple, and economic method, hollow-fiber ultrafiltration followed by centrifugation, has been developed for separation of viscid substances with similar properties except for different molecular weight. The experimental assembly needed only a U-shaped hollow fiber containing the sample solution with both ends of the fiber connected to two syringe needles. Ultrafiltration was performed by the action of centrifugal force. Concentration polarization was overcome and no phase transition occurred. Satisfactory recovery was achieved.     

Tunneling in the loss of hydrogen chloride from isopropyl chloride cation

The unimolecular dissociation of isopropyl chloride cation has been investigated using mass-analyzed ion kinetic energy spectrometry. The C3H6*+ ion was the only product ion in the metastable dissociation. The kinetic energy release distribution for the HCl loss was determined. Ab initio molecular orbital calculations were performed at the MP2/6-311++G(d,p) level together with single point energy calculations at the QCSID(T)/6-311++G(2d,2p) level. The calculations show that the molecular ion rearranges to an ion-dipole complex prior to loss of HCl via a transition state containing a four-membered ring. The rearrangement involves H atom transfer. On the basis of the potential energy surface obtained for the loss of HCl and Cl*, the rate constants were calculated by transition-state statistical theories with considering tunneling effect. From the calculated result, it is proposed that the observed HCl loss would occur via tunneling through the barrier for isomerization to the ion-dipole complex, CH3CHCH2*+...HCl.     

Host–guest‐like thi­amine–anion complexation in thia­minium bis­(tetra­fluoro­borate)

In the title compound, 3‐[(4‐amino‐2‐methyl‐5‐pyrimidin‐1‐io)methyl]‐5‐(2‐hydroxy­ethyl)‐4‐methyl­thia­zolium(2+) bis(tetra­fluoro­borate), C₁₂H₁₈N₄OS²⁺·2BF₄^?, the divalent thia­mine cation (in the F conformation) is associated with BF₄^? anions via two characteristic bridging interactions between the thia­zolium and pyrimidinium rings, i.e. C—H?BF₄^??pyrimidinium and N—H?BF₄^??thia­zolium interactions. Thi­amine mol­ecules are linked by N—H?O hydrogen bonds to form a helical chain structure.