Cope elimination and complexation of poly(dimethylaminoethyl methacrylate N-oxide)

Poly(dimethylaminoethyl methacrylate N-oxide) (poly(DMAEMNO)) was prepared by oxidation of poly(dimethylaminoethyl methacrylate) with hydrogen peroxide in methanol. From thermogravimetric and IR spectroscopic investigations Cope elimination of amine oxide group in poly(DMAENO) was found to occur at 120–150°C. The postpolymerization of partially pyrolyzed polymer carrying vinyl ester group as pendant was performed with azobisisobutyronitrile at 60°C in methanol to give cross-linked polymer that was found to form hydrogel. Poly(DMAEMNO) gave metal–polymer complexes with CuCl₂, ZnCl₂, and CoCl₂. Cobalt–polymer complex had a constitution of 1:2 of metal ion to amine oxide group, while copper– and zinc–polymer complexes seemed to have structures of 1:1 and 1:2 of metal ion to amine oxide group. Furthermore, polymer complexes of poly(DMAEMNO) with poly(methacrylic acid) and poly(acrylic acid) were found to be formed by mixing aqueous solutions of both polymers and also by radical polymerization of the acid monomers in the presence of poly(DMAEMNO). From elemental analysis, thermogravimetric investigation, and measurement of turbidity it was concluded that the resulting polymer–polymer complexes contained more than one acid monomer unit per one N-oxide unit.     

Tetraalkylammonium Picrates in the Dichloromethane–Water System: Ion-Pair Formation and Liquid–Liquid Distribution of Free Ions and Ion Pairs

Equilibria concerning picrates of tetraalkylammonium ions (Me₄N⁺, Et₄N⁺, Pr₄N⁺, Bu₄N⁺, Bu₃MeN⁺) in a dichloromethane−water system have been investigated at 25 ^∘C. The 1:1 ion-pair formation constants (K _IP,o ^o) in dichloromethane at infinite dilution were conductometrically determined. The distribution constants (K _D ^o) of the ion pairs and the free cations between the solvents were determined by a batch-extraction method. The K _IP,o ^o value varies in the cation sequence, Bu₄N⁺ ≈ Pr₄N⁺ ≈ Et₄N⁺ < Bu₃MeN⁺ < < Me₄N⁺; this trend is explained by the electrostatic cation−anion interaction taking into account the structures of the ion pairs determined by density functional theory calculations. For the ion pairs of the symmetric R₄N⁺ cations, there is a linear positive relationship between log₁₀ K _D ^o and the number of methylene groups in the cation (N _{CH 2}). The ion pair of asymmetric Bu₃MeN⁺ has a higher distribution constant than that expected from the above log₁₀ K _D ^o versus N _{CH 2} relationship. These cation dependencies of log₁₀ K _D ^o for the ion pairs are explained theoretically by using the Hildebrand-Scatchard equation. For all the cations, the log₁₀ K _D ^o value of the free cation increases linearly with N _{CH 2}; the variation of log₁₀ K _D ^o is discussed by decomposing the distribution constant into the Born-type electrostatic contribution and the non-Born one, and attributed to the latter that is governed by the differences in the molar volumes of the cations. The cation dependencies of the ion-pair extractability and ion pairing in water are also discussed. An erratum to this article can be found at     

Charge separation in a nonfluorescent donor-acceptor dyad derived from boron dipyrromethene dye, leading to photocurrent generation

Boron dipyrromethene (BODIPY), which is commonly used as an energy absorbing and transferring antenna molecule, has been modified to contain an electron donor moiety, 8-(2,4,5-trimethoxyphenyl)-4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene (MEOPHBDP). The photoinduced electron transfer from a 2,4,5-trimethoxyphenyl moiety to a BODIPY moiety of MEOPHBDP in acetonitrile was observed by femtosecond laser flash photolysis measurements. The lifetime of the charge-separated state of MEOPHBDP was 59 ps at 298 K. The dye-sensitized solar cells (DSSC) were prepared using MEOPHBDP with carboxylic acid (MEOPHBDP-COOH) and a reference BODIPY dye having no electron donor moiety. The photovoltaic measurements were performed using a standard two-electrode system consisting of a working electrode and a Pt sputtered electrode in methoxyacetonitrile containing 0.5 M iodide and 0.05 M I(2). The photoelectrochemical properties of DSSC with MEOPHBDP are compared with those with a reference BODIPY dye.     

An iterative type I polyketide synthase PKSN catalyzes synthesis of the decaketide alternapyrone with regio-specific octa-methylation

A biosynthetic gene cluster containing five genes, alt1-5, was cloned from Alternaria solani, a causal fungus of early blight disease to tomato and potato. Homology searching indicated that the alt1, 2, and 3 genes code for cytochrome P450s and the alt4 gene for a FAD-dependent oxygenase/oxidase. The alt5 gene encodes a polyketide synthase (PKS), named PKSN, that was found to be an iterative type I complex reduced-type PKS with a C-methyltransferase domain. To identify the PKSN function, the alt5 gene was introduced into the fungal host Aspergillus oryzae under an alpha-amylase promoter. The transformant produced a polyketide compound, named alternapyrone, whose structure is shown to be 3,5-dimethyl-4-hydroxy-6-(1,3,5,7,11,13-hexamethyl-3,5,11-pentadecatrienyl)-pyran-2-one. Labeling experiments confirmed that alternapyrone is a decaketide with octa-methylation from methionine on every C(2) unit except the third unit.     

Blue copper model complexes with distorted tetragonal geometry acting as effective electron-transfer mediators in dye-sensitized solar cells

The electron self-exchange rate constants of blue copper model complexes, [(-)-sparteine-N,N'](maleonitriledithiolato-S,S')copper ([Cu(SP)(mmt)])(0/)(-), bis(2,9-dimethy-1,10-phenanthroline)copper ([Cu(dmp)(2)](2+/+)), and bis(1,10-phenanthroline)copper ([Cu(phen)(2)](2+/+)) have been determined from the rate constants of electron transfer from a homologous series of ferrocene derivatives to the copper(II) complexes in light of the Marcus theory of electron transfer. The resulting electron self-exchange rate constant increases in the order: [Cu(phen)(2)](2+/+) < [Cu(SP)(mmt)](0/)(-) < [Cu(dmp)(2)](2+/+), in agreement with the order of the smaller structural change between the copper(II) and copper(I) complexes due to the distorted tetragonal geometry. The dye-sensitized solar cells (DSSC) were constructed using the copper complexes as redox couples to compare the photoelectrochemical responses with those using the conventional I(3)(-)/I(-) couple. The light energy conversion efficiency (eta) values under illumination of simulated solar light irradiation (100 mW/cm(2)) of DSSCs using [Cu(phen)(2)](2+/+), [Cu(dmp)(2)](2+/+), and [Cu(SP)(mmt)](0/)(-) were recorded as 0.1%, 1.4%, and 1.3%, respectively. The maximum eta value (2.2%) was obtained for a DSSC using the [Cu(dmp)(2)](2+/+) redox couple under the light irradiation of 20 mW/cm(2) intensity, where a higher open-circuit voltage of the cell was attained as compared to that of the conventional I(3)(-)/I(-) couple.     

Synthesis and nanoimprinting of high refractive index and highly transparent polythioethers based on thiol-ene click chemistry

This work demonstrates the UV nanoimprinting lithography (UV-NIL) of high refractive index and highly transparent polythioethers based on thiol-ene click chemistry. Herein, 9,9-bis(3-mercaptopropylphenylether)fluorene (BMPF) is designed as a new thiol monomer with a high refractive index, high transparency, and good processability for UV-NIL. Colorless polythioethers are synthesized from BMPF and ene monomers under mild thiol-ene click reaction conditions. Excellent transmittance (96%) of 400 nm light is observed in all the polymer films and high refractive index values of 1.5972–1.6382 are attained. UV-NIL using thiol-ene photopolymerization affords polymer nanoimprinting patterns with various features on the order of 100–500 nm without any fractures. To the best of our knowledge, this is the first report on UV-NIL of high refractive index and highly transparent polymers. Through proper monomer and polymer design, novel polythioethers with suitable glass transition temperature (T _g) values are developed with high refractive index, high transparency, and good UV-NIL processability. Furthermore, UV-NIL based on thiol-ene click chemistry is accomplished at the nanoscale. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2175–2182     

Synthesis and characterization of 9,9‐bis(4‐hydroxyphenyl and 4‐aminophenyl)dibenzofluorenes: Novel fluorene‐based monomers

Two novel 9,9‐difunctionalized fluorene‐type monomers, 9,9‐bis(4‐hydroxyphenyl‐ and 4‐aminophenyl)‐2,3:6,7‐dibenzofluorenes, are synthesized by the reaction of dibenzenzofluorenone with phenol and aniline. These monomers are used for the preparation of polyester and polyimide as the typical polymers to evaluate the property change such as thermal stability caused by the benzene rings fused to the fluorene skeleton with keeping good solubility, in comparison with the polymers derived from simple fluorenone. In fact, these two new polymers have the fairly enhanced thermal stability and refractive index value along with satisfactory solubility in organic solvents, enough to emphasize the fusion effect. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2602–2605     

Optical coupling characteristics of graded-index type photonic crystal fiber collimator depending on air hole diameter ratio to pitch

Optical Review - A graded-index type photonic crystal fiber (GI-PCF) has a graded effective index distribution that can be realized by an α-power air hole diameter distribution in radial...