Poly(thiaheterohelicene): a stiff conjugated helical polymer comprised of fused benzothiophene rings

A novel helical aromatic polymer comprised of fused benzothiophene rings, poly(thiaheterohelicene), was synthesized via an intramolecular ring-closing reaction with a controlled helicity to one-sided bias. The synthetic helicity control involved the induction of the helical conformation and its fixation. The ladder polymer showed both an extended pi-conjugation and planarity and a very stiff helical structure. [structure: see text]     

Control of refractive index of sol-gel tungsten oxide films

Tungsten oxide films were prepared by a complexing agent-assisted sol-gel process. All the films were at 500°C were crystalline and transparent. The refractive index n and extinction coefficient k of the films were calculated from the transmittance and reflectance spectra in the visible and infrared regions. The values of n were lowered to depend on the organic ligands used in the preparation of the sols. The use of such ligands may be a mean to control the refractive index of coatings.     

Complexation of metal ion with poly(1-vinylimidazole) resin prepared by radiation-induced polymerization with template metal ion

Poly(1-vinylimidazole) (PVI) resin was prepared with Ni²⁺, Co²⁺, or Zn²⁺ as a template to study the adsorption of metal ions. The metal-1-vinylimidazole complex was copolymerized and crosslinked with 1-vinyl-2-pyrrolidone by γ-ray irradiation and the template metal ion was removed by treating the polymer complex with an acid. These PVI resins adsorbed metal ions more effectively than the PVI resin prepared without the template. The number of adsorption sites (As) and the stability constant (K) of Ni²⁺ complex were larger for the PVI resin prepared with the Ni ion template, caused by the smaller dissociation rate constant of Ni ion from the resin. The composition of the Ni²⁺ complex in the resin remained constant. This suggests that the complexation proceeded via a one-step mechanism.     

Immobilization of heme complex by radiation polymerization

Transparent films containing an iron-porphyrin complex were synthesized by ⁶⁰Co γ-ray irradiation of aqueous solutions of ironporphyrin complex and a water soluble monomer such as 2-hydroxyethylmethacrylate or 1-vinyl-2-pyrrolidone. The iron(II)porphyrin complex was immobilized in the film by covalent bonding without any denaturation, under anaerobic condition or by protection of the ironporphyrin complex with carbon monoxide. After the irradiation of iron(III)porphyrin, the central iron ion was reduced spontaneously to the ferrous state. The films containing the iron(II)porphyrin adsorbed quantitatively carbon monoxide gas.     

Cationic Rh complexes with novel spiro tetraarylpentaborate anions prepared from arylboronic acids and aryloxorhodium complexes

Ar-B(OH)2 (1a: Ar = C6H4OMe-4, 1b: Ar = C6H3Me2-2,6) react immediately with Rh(OC6H4Me-4)(PMe3)3 (2) in 5 : 1 molar ratio at room temperature to generate [Rh(PMe3)4]+[B5O6Ar4]- (3a: Ar = C6H4OMe-4, 3b: Ar = C6H3Me2-2,6). p-Cresol (92%/Rh), anisole (80%/Rh) and H2O (364%/Rh) are formed from 1a and 2. The reaction of 1a with 2 for 24 h produces [Rh(PMe3)4]+[B5O6(OH)4]- (4) as a yellow solid. This is attributed to hydrolytic dearylation of once formed 3a because the direct reaction of 3a with excess H2O forms 4. An equimolar reaction of 2 with phenylboroxine (PhBO)3 causes transfer of the 4-methylphenoxo ligand from rhodium to boron to produce [Rh(PMe3)4]+[B3O3Ph3(OC6H4Me-4)]- (5). Arylboronic acids 1a and 1b react with Rh(OC6H4Me-4)(PR3)3 (6: R = Et, 8: R = Ph) and with Rh(OC6H4Me-4)(cod)(PR3) (11: R = iPr, 12: R = Ph) to form [Rh(PR3)4]+[B5O6Ar4]- (7a: R = Et, Ar = C6H4OMe-4, 7b: R = Et, Ar = C6H3Me2-2,6, 9a: R = Ph, Ar = C6H3Me2-2,6) and [Rh(cod)(PR3)(L)]+[B5O6Ar4]- (13b: R = iPr, L = acetone, Ar = C6H3Me2-2,6, 14a: R = Ph, L = PPh3, Ar = C6H4OMe-4, 14b: R = Ph, L = PPh3, Ar = C6H3Me2-2,6), respectively. Hydrolysis of 14a yields [Rh(cod)(PPh3)2]+[B5O6(OH)4]- (15) quantitatively.     

Orientation and Surface Properties of Sol-Gel Derived Y2O3 Films

The orientation, surface and optical properties of sol-gel derived Y₂O₃ films have been investigated. Transparent Y₂O₃ films were prepared on quartz glass substrates by sol-gel processes using YCl₃·6H₂O as a starting material. The water droplet contact angles of the films reached constant values between 79° and 90° after the films were left for 8 to 10 days in air at ambient temperature, indicating that the film surface exhibited hydrophobicity. When 2-(2-methoxyethoxy)ethanol (MEE) was added to the sol, yttria in the films crystallized to a strongly oriented cubic phase at firing temperatures between 400°C and 500°C. The intensity of the XRD peaks increased as the firing temperature was increased to 900°C. However, yttria crystallized to a non-oriented cubic phase when MEE was not used. The refractive index and packing density of the Y₂O₃ films increased from 1.55 to 1.68 and from 0.67 to 0.79, respectively, as the firing temperature was raised from 400°C to 900°C, indicating that sol-gel derived Y₂O₃ films are lower in density than evaporated ones.     

A novel attractive interaction in the Diels–Alder reaction of N-protected pyrroles with allene-1,3-dicarboxylates

The endo/exo selectivities of Diels–Alder reactions of N-protected pyrroles with allene-1,3-dicarboxylates were studied under Lewis acid assisted and thermal reaction conditions. A novel attractive effect between the N-protective carbonyl group of pyrrole and the ester group of allene-1,3-dicarboxylates operates to control the selectivity in the above Diels–Alder reaction. This new attractive effect to give the exo adduct is more effective than the Alder orbital effect.     

Reversible Coordination of Molecular Nitrogen to Polymeric Benzenecarbonylchromium Complexes

Polymeric benzenetricarbonylchromium complexes were synthesized by radical copolymerization of benzyl acrylatetricarbonylchromium with styrene and by reaction of (dimethylaminobenzene)tricarbonylchromium with poly(styrene-co-acrylic acid). The polymeric chromium complexes give transparent films and on UV irradiation under nitrogen lead to dinitrogen complexes of the corresponding polymeric dicarbonylchromium. The reversible coordination of dinitrogen was confirmed by IR and visible absorption spectroscopy. A predominant feature of the polymeric dinitrogen complexes is their extraordinarily high stability in air compared with the corresponding low molecular analogs. The effect of polymer matrices on dinitrogen coordination is discussed.     

Fluorophilic cobalt phthalocyanine‐containing Nafion membrane: high oxygen permeability and proton conductivity in the membrane

A multiply‐fluorinated cobalt phthalocyanine (CoFPC) was prepared, which could reversibly interact with oxygen. CoFPC was introduced into the hydrophobic perfluoroethylene‐backbone domain of the Nafion membrane. The localization of CoFPC did not reduce the high proton conductivity (10^?2–10^?3 S cm^?1) ascribed to the hydrophilic channel of Nafion. The oxygen permeability through the CoFPC/Nafion membrane was higher than the nitrogen permeability and that of the pristine Nafion membrane, and was significantly enhanced at the lower upstream pressure. The permselectivity of oxygen versus nitrogen increased beyond 20 with the CoFPC content in the membrane. The CoFPC/Nafion membrane was coated on a glassy carbon modified with a Pt/C catalyst. The high electrochemical reduction current of oxygen suggested that the CoFPC/Nafion membrane efficiently supplied oxygen to the Pt/C catalyst. Copyright © 2009 John Wiley & Sons, Ltd.