Tertiary amine-mediated synthesis of microporous carbon membranes

Microporous carbon membranes were prepared on an -alumina support by a pyrolysis of cationic tertiary amine/anionic polymer composites. The precursor solutions contain a thermosetting resorcinol/formaldehyde (RF) polymer and a cationic tertiary amine. Three types of cationic tertiary amines with different chain lengths were used, such as tetramethlammonium bromide (TMAB), tetrapropylammonium bromide (TPAB) and cetyltrimethylammonium bromide (CTAB). A porous structure was produced by a decomposition of the amine and the resulting pores assisted the further gasification of the RF polymer at high temperature. The carbon/alumina membranes have thin and continuous carbon top layers with a thickness of 1 μm. Gas permeation tests were performed using single gases of CO₂, O₂, N₂, CF₄, n-C₄H₁₀ and i-C₄H₁₀, as well as binary mixtures of CH₄/n-C₄H₁₀ and N₂/CF₄ at different temperatures between 23 and 150 °C. The carbon membrane prepared using TMAB showed separation factors higher than 650 for the CH₄/n-C₄H₁₀ mixtures and higher than 8100 for the N₂/CF₄ mixture. From the permeation of pure gases with different molecular sizes, the pore sizes of the carbon membrane prepared using TMAB, TPAB and CTAB are estimated to be 4.0, 5.0 and larger than 5.5 Å, respectively, indicating that the micropore size of the carbon membranes is controllable by using different amines.     

Highly meso-Diastereoselective Pinacol Coupling of Aromatic Aldehydes Mediated by Al Powder/Copper Sulfate in Water

Pinacol-type coupling reaction products presenting a high meso-diastereoselectivity (the ratio dl/meso was 4/96 up to 1/99) were obtained in fair to good yields (24–69%) using several aromatic aldehydes as starting materials and aluminium powder/copper sulfate as catalysts, in water, under reflux conditions.     

Optimization of cation structure of imidazolium-based ionic liquids as ionic solvents for rechargeable magnesium batteries

A series of imidazolium cation-based ionic liquids (ILs) have been synthesized and examined as ionic solvents for rechargeable magnesium batteries. The electrolyte solutions consist of these ILs dissolving methylmagnesium bromide with tetrahydrofuran (MeMgBr/THF). The chemical structure of imidazolium cation much influenced the ionic conductivity and the electrochemical window of the system. A reversible process of cathodic deposition and anodic dissolution of magnesium has been successfully achieved at room temperature. The highest value of anodic peak current for magnesium dissolution was obtained in an optimized-structure IL with allyl and methoxyethyl groups as the substituents.     

Quadruple Decker [3.3][3.3][3.3]Orthocyclophane Acetal—An Orthocyclophane Ladder

Through clever bridging of orthocyclophanes (in this case by acetalization), molecules such as 1 can be formed with four benzene rings in a stacked face-to-face arrangement. UV/Vis spectroscopic and electrochemical properties of 1 are governed by π–π through-space interactions within the molecule.     

Rotational-coherence molecular laser isotope separation

We have proposed a laser isotope separation method, utilizing rotational coherence of a simple molecule. In the scheme, photoexcited molecules are isotopically separated by difference of rotational period between them. To illustrate this method, two-pulse photodissociation of mixed ⁷⁹Br₂/⁸¹Br₂ isotopes has been investigated theoretically. The photodissociation probabilities of ⁷⁹Br₂ and ⁸¹Br₂ have been calculated as functions of time delay between the photoexcitation and dissociation laser pulses. We have demonstrated that isotope enrichment factor of ⁷⁹Br relative to ⁸¹Br can be changed from 0.34 to 1.8, by simply changing the time delay only by 0.2 ns. Additionally, we have shown that this method is effective for heavy isotopes, based on mass dependence of the isotope enrichment factor.     

Spin coupling and orbital angular momentum quenching in free iron clusters

Magnetic spin and orbital moments of size-selected free iron cluster ions Fe{n}{+} (n=3-20) have been determined via x-ray magnetic circular dichroism spectroscopy. Iron atoms within the clusters exhibit ferromagnetic coupling except for Fe{13}{+}, where the central atom is coupled antiferromagnetically to the atoms in the surrounding shell. Even in very small clusters, the orbital magnetic moment is strongly quenched and reduced to 5%-25% of its atomic value while the spin magnetic moment remains at 60%-90%. This demonstrates that the formation of bonds quenches orbital angular momenta in homonuclear iron clusters already for coordination numbers much smaller than those of the bulk.     

TG-DTA study on the lanthanoid trifluoromethanesulfonate complexes

The thermal decomposition of the lanthanoid trifluoromethanesulfonate (triflate) complexes {Ln(CF₃SO₃)₃·9H₂O; Ln=La-Lu{ was studied by TG and DTA methods. From the endothermic and exothermic data of Ln(CF₃ SO₃)3·9H₂O complexes, pyrolysis behavior of the complexes is classified into three groups: 1) La-Nd salts, 2) Sm-Ho salts, 3) Er-Lu salts. It has also shown that all the final decomposition products were found to result in the formation of LnF₃. This revised version was published online in July 2006 with corrections to the Cover Date.