Synthesis and gas permeation properties of poly(diarylacetylene)s having substituted and twisted biphenyl moieties

Diarylacetylene monomers containing substituted biphenyl ( 1a – f ) and anthryl ( 1g ) groups were synthesized and then polymerized with TaCl₅‐n‐Bu₄Sn catalyst to produce the corresponding poly(diarylacetylene)s ( 2a – g ). Polymers 2a – f were soluble in common organic solvents such as cyclohexane, toluene, and chloroform. According to thermogravimetric analysis, the onset temperatures of weight loss of the polymers were over 400 °C in air, indicating considerably high thermal stability. Free‐standing membranes 2a and 2c – e were prepared by the solution casting method. Desilylation of Si‐containing membrane 2c was carried out with trifluoroacetic acid to afford 3c . All the polymer membranes, especially those having twisted biphenyl groups, exhibited high gas permeability; for example, their oxygen permeability (PO ₂) values ranged from 130 to 1400 barrers. Membrane 2d having two chlorine atoms in the biphenyl group showed the highest gas permeability (PO ₂ = 1400 barrers) among the present polymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 861–868, 2010     

Performance of C1-symmetric chiral ammonium betaines as catalysts for the enantioselective Mannich-type reaction of α-nitrocarboxylates

The catalytic performance of C₁-symmetric chiral ammonium betaines in the enantioselective direct Mannich-type reaction of α-nitrocarboxylates with N-Boc imines has been investigated. The most effective catalyst structure has been identified; this provides a reliable synthetic route to a variety of enantiomerically enriched α-tetrasubstituted α,β-diamino acid derivatives.     

Sequential enzymatic epoxidation involved in polyether lasalocid biosynthesis

Enantioselective epoxidation followed by regioselective epoxide opening reaction are the key processes in construction of the polyether skeleton. Recent genetic analysis of ionophore polyether biosynthetic gene clusters suggested that flavin-containing monooxygenases (FMOs) could be involved in the oxidation steps. In vivo and in vitro analyses of Lsd18, an FMO involved in the biosynthesis of polyether lasalocid, using simple olefin or truncated diene of a putative substrate as substrate mimics demonstrated that enantioselective epoxidation affords natural type mono- or bis-epoxide in a stepwise manner. These findings allow us to figure out enzymatic polyether construction in lasalocid biosynthesis.     

Prodrug study of plinabulin using a click strategy focused on the effects of a replaceable water-solubilizing moiety

Plinabulin (1) is a potent anti-microtubule agent, however, its low water solubility has to be improved for the advantage in pharmacokinetics and chemotherapy. In this report, the replaceable water-solubilizing moiety of the water-soluble prodrug of plinabulin (1) was investigated. The properties of the water-soluble prodrugs of plinabulin (1), in which the water-solubilizing part was replaced with a new functionality, were evaluated. The newly introduced water-solubilizing moiety provided interesting effects on the water solubility and half-life of the prodrugs.     

A Linear programming formulation for routing asynchronous power systems of the Digital Grid

In recent years, practical research related to distributed power generation and networked distribution grids has been increasing. This research uses a relatively abstract model for the cost reduction in the Digital Grid Power Network. In the Digital Grid, the traditional wide-area synchronous grid is divided into smaller segmented grids which are connected asynchronously. In this paper, we demonstrate how to formulate the minimized cost of power generation by using linear programming methods, while considering the cost of electric transmission and distribution and using asynchronous power interchange among separate grids.     

Bifunctional organocatalyst for activation of carbon dioxide and epoxide to produce cyclic carbonate: betaine as a new catalytic motif

Bifunctional organocatalysts bearing an ammonium betaine framework have been developed as a new catalytic motif for the activation of carbon dioxide and epoxides to produce cyclic carbonates.     

Nickel(II) and copper(II) complexes of β-unsubstituted 5,15-diazaporphyrins and pyridazine-fused diazacorrinoids: metal-template syntheses and peripheral functionalizations

The present paper reports the first comprehensive study on the synthesis, structures, optical and electrochemical properties, and peripheral functionalizations of nickel(II) and copper(II) complexes of β-unsubstituted 5,15-diazaporphyrins (M-DAP; M = Ni, Cu) and pyridazine-fused diazacorrinoids (Ni-DACX; X = N, O). These two classes of compounds were constructed starting from mesityldipyrromethane by a metal-template method. Ni-DAP and Cu-DAP were prepared in high yields by the reaction of the respective metal-bis(dibromodipyrrin) complexes with NaN(3)-CuX (X = I, Br), whereas Ni-DACN and Ni-DACO were formed as predominant products by the reaction with NaN(3). In both cases, the metal centers change their geometry from tetrahedral to square planar during the aza-annulation; X-ray crystallographic analyses of M-DAPs showed highly planar diazaporphyrin π planes. The Q band of Ni-DAP was redshifted and intensified compared with that of a nickel-porphyrin reference, due to the involvement of electronegative nitrogen atoms at the meso positions. It was found that the peripheral bromination of Ni-DAP and Ni-DACO occurred regioselectively to afford Ni-DAP-Br(4) and Ni-DACO-Br, respectively. These brominated derivatives underwent Stille reactions with tributyl(phenyl)stannane to give the corresponding phenylated derivatives, Ni-DAP-Ph(4) and Ni-DACO-Ph. On the basis of the absorption spectra and X-ray analysis, it has been concluded that the attached phenyl groups efficiently conjugate with the diazaporphyrin π system. The present results unambiguously corroborate that the β-unsubstituted DAPs and DACXs are promising platforms for the development of a new class of π-conjugated azaporphyrin-based materials.     

Characterization of AgInS2 thin films prepared by vacuum evaporation

We characterized AgInS₂ thin films prepared by vacuum evaporation. In the case of thin films annealed at 400 °C, diffraction peaks were observed only for the chalcopyrite AgInS₂ phase. The chemical composition of the thin films annealed at 400 °C was 26.5 at% Ag, 23.8 at% In, and 49.7 at% S. PL spectra of the AgInS₂ thin films at 10.7 K showed peaks at 1.70, 1.80, and 1.83 eV. The PL peak at1.80 eV was attributed to sulfur deficiency.     

Halide ion complexes of decaborane (B10H14) and their derivatives: noncovalent charge transfer effect on second-order nonlinear optical properties

Quantum molecular engineering has been performed to determine the second-order nonlinear optical (NLO) properties in different halo complexes of decaborane (B(10)H(14)) and their derivatives using the density functional theory (DFT) method. These decaborane halo complexes of X(-)@B(10)H(14) (X = F, Cl, Br, and I) are found to possess noncovalent charge transfer interactions. The static polarizability (α(0)) and first hyperpolarizability (β(0)) among these complexes increase by moving down the group from F to I, partly due to the increase in size of their anionic radii and the decrease in their electron affinities. A two-level approximation has been employed to investigate the origin of β(0) values in these halo complexes, which show very consistent results with those by the finite-field method. Furthermore, in the same line, two experimentally existing complexes, I(-)@B(10)H(14) and I(-)@2,4-I(2)B(10)H(12), are found to have considerably large β(0) values of 2859 and 3092 a.u., respectively, which are about three times larger than a prototypical second-order NLO molecule of p-nitroaniline, as reported by Soscun et al. [Int. J. Quantum Chem.2006, 106, 1130-1137]. Besides this, the special effects of solvent, counterion, and bottom substitutions have also been investigated. Interestingly, 2,4-alkali metal-substituted decaborane iodide complexes show remarkably large second-order NLO response with β(0) amplitude as large as 62436 a.u. for I(-)@2,4-K(2)B(10)H(12) complex, which are explained in terms of their transition energies, frontier molecular orbitals and electron density difference plots. Thus, the present investigation provides several new comparative insights into the second-order NLO properties of halo complexes of decaborane, which possess not only large first hyperpolarizabilities, but also high tunability to get a robustly large second-order NLO response by alkali metal substitution effects.     

Covalently Linked 5,15‐Diazaporphyrin Dimers: Promising Scaffolds for a Highly Conjugated Azaporphyrin π System

The first examples of β–β directly linked, acetylene‐bridged, and butadiyne‐bridged 5,15‐diazaporphyrin dimers have been prepared by palladium‐catalyzed coupling reactions of nickel(II) and copper(II) complexes of 3‐bromo‐10,20‐dimesityl‐5,15‐diazaporphyrin (mesityl=2,4,6‐trimethylphenyl). The effects of the linking modes and meso‐nitrogen atoms on the structural, optical, electrochemical, and magnetic properties of the distributed π systems were investigated by using X‐ray crystallography, UV/Vis absorption spectroscopy, DFT calculations, cyclic voltammetry, and ESR spectroscopy. Both the electronic and steric effects of the meso‐nitrogen atoms play an important role in the highly coplanar geometry of the directly linked dimers. The direct β–β linkage produces enhanced π conjugation and electron‐spin coupling between the two diazaporphyrin units.