Reflection spectra of various kinds of oxide glasses and fluoride glasses in the vacuum ultraviolet region

Reflection spectra of silicate, borate, phosphate, fluorophosphate and fluoride glasses are studied in the spectral region of 2–13 eV in order to understand their dispersion behaviors in the visible region from the point of view of atomic structures.The absorption bands due to bridging oxygen ions or fluorine ions are found at 11.6 eV and 10.4–9.5 eV in silicate glasses, at 10.2 and 8.8 eV in borate glasses, at 9.5 eV in phosphate glasses, at 11.2 eV in fluorophosphate glasses and at 11 eV in fluorozirconate glasses.In silicate glasses, the bands due to nonbridging oxygen ions are found in the region 8.8-4.9 eV. They shift to lower energies with increasing ionic radius, in the order of Ca²⁺, Sr²⁺ and Ba²⁺, for the glasses containing low valency cations, while they shift to higher energies with increasing ionic radius, in the order of Ti⁴⁺, Zr⁴⁺ and Th⁴⁺ or in the order of Nb⁵⁺ and Ta⁵⁺, for the glasses containing high valency cations.In glasses containing large amounts of PbO, strong bands due to PB²⁺ ions appear in the lower energy regions of 6.3–5.6 eV and 5.2–4.7 eV.     

Fourier transform microwave spectrum of CO-dimethyl ether

Two sets of 32 rotational transitions were observed for the carbon monoxide-dimethyl ether (CO-DME) complex and two sets of 30 transitions for both (13)CO-DME and C(18)O-DME, in the frequency region from 3.5 to 25.2 GHz, with J ranging from 1<--0 up to 7<--6, by using a Fourier transform microwave spectrometer. The splittings between the two sets of the same transition varied from 2 to 15 MHz, and the two components were assigned to the two lowest states of the internal rotation of CO with respect to DME governed by a twofold potential. A preliminary analysis carried out separately for the two sets of the observed transition frequencies by using an ordinary asymmetric-rotor Hamiltonian indicated that the heavy-atom skeleton of the complex was essentially planar, as evidenced by the "pseudoinertial defects," i.e., the inertial defects, which involve the contributions of the out-of-plane hydrogens of the two methyl groups, I(cc)-I(aa)-I(bb) of -5.764(23) and -5.753(16) uA(2) for the symmetric and antisymmetric states, respectively. All of the observed transition frequencies were subsequently analyzed simultaneously, by using a phenomenological Hamiltonian which was described in a previous paper on Ar-DME and Ne-DME [Morita et al., J. Chem. Phys. 124, 094301 (2006)]. The rotational constants thus derived were analyzed to give the distance between the centers of gravity of the two component molecules, DME and CO, to be 3.682 A and the angle between the CO and the a-inertial axes to be 75.7 degrees ; the C end of the CO being closer to the DME. Most a-type transitions were observed as closely spaced triplets, which were ascribed to the internal rotation of the two methyl tops of DME. The V(3) potential barrier was obtained to be 772(2) cm(-1) from the first-order Coriolis coupling term between the internal rotation and overall rotation, which is about 82% of V(3) for the DME monomer, whereas the second-order contribution of the coupling to the B rotational constant led to V(3) of 705(3) cm(-1). By assuming a Lennard-Jones-type potential, the dissociation energy was estimated to be E(B)=1.6 kJ mol(-1), to be compared with 1.0 and 2.5 kJ mol(-1) for Ne-DME and Ar-DME, respectively.     

Polycyclic N‐heterocyclic compounds. Part 66: Synthesis of N‐[2‐([1,2,4]oxadiazol‐5‐yl)cyclopenten‐1‐yl]formamide oximes and their evaluation as inhibitors of platelet aggregation

N‐[2‐([1,2,4]Oxadiazol‐5‐yl)cyclopenten‐1‐yl]formamide oximes were synthesized by fusion of (6,7‐dihydro‐5H‐cyclopenta[1,2‐d]pyrimidin‐4‐yl)amidines and/or their amide oximes with hydroxylamine hydrochloride through a subsequent rearrangement reaction. Assay of the products for anti‐platelet aggregation activity revealed that certain of them showed promising inhibitory effect on arachidonic acid‐induced platelet aggregation. J. Heterocyclic Chem., (2011).     

Supramolecular organization of light-harvesting porphyrin macrorings

Porphyrin‐based supramolecular nanostructures have been produced by the self‐assembly of porphyrin macrorings with three benzoic acid groups (Acid‐R) on each side of the rings through cooperative carboxyl–carboxyl hydrogen bonds. Structures of the organized Acid‐R were analyzed by AFM, and two clear distribution peaks were observed at 3 and 27 nm in the height‐distribution histogram. From the overall assessment, the higher objects are considered to be one‐dimensional structures standing vertically on the mica substrate. The height corresponds to an 11‐mer of a unit Acid‐R. Light‐harvesting functions were examined by using fluorescence titration, whereby an energy‐acceptor molecule (Tripod 2 ) was employed that strongly interacted with Acid‐R units (association constant: 2.0×10⁸ M ^?1), specifically from the inner pore. The titration results showed that the apparent stoichiometry [Tripod 2 ]/[Acid‐R] was <0.5, and that the value was concentration dependent. Titration results reasonably account for the scheme in which Tripod 2 only interacts with each terminal in the organized Acid‐R. The number of organization was fitted to a 10‐mer of Acid‐R in a 6.8×10^?7 M solution, and was consistent with that estimated from the AFM results. In the composites of organized Acid‐R/Tripod 2 , a singlet excitation energy transfer occurred among the Acid‐R units, and to Tripod 2 . The energy‐transfer rate constants were estimated by using the decamer model, which employed kinetic parameters obtained from steady‐state and time‐resolved fluorescence experiments.     

Photoelectrochemical Reduction of Highly Concentrated CO2 Using a p-InP Electrode

Carbon dioxide was photoelectrochemically reduced at a p-type InP photocathode in highly concentrated CO₂ solution in methanol at elevated pressure (40 atm). Relatively high current densities were achieved (200 mA/cm²) with high current efficiencies for CO production (~90%). These current densities are approximately an order of magnitude higher than those reported previously in the literature for photoelectrochemical reduction due to the very high CO₂ concentration (~8 mol/L). Other products were hydrogen and methyl formate (produced via reaction between formic acid and the methanol solvent), Hydrocarbons were produced in only trace amounts.