Controlled radical polymerization of anthracene‐containing methacrylate copolymers for stimuli‐responsive materials

Novel reversible networks utilizing photodimerization of crosslinkable anthracene groups and thermal dissociation were investigated. Reversible addition‐fragmentation chain transfer polymerization yielded well‐defined copolymers with 9‐anthrylmethyl methacrylate (AMMA) and other alkyl methacrylates such as methyl methacrylate (MMA) and 2‐ethylhexyl methacrylate (EHMA) having different AMMA compositions. Well‐controlled block copolymerization of AMMA and alkyl methacrylates was also successfully accomplished using a trithiocarbonate‐terminated poly(alkyl methacrylate) macro‐chain transfer agent. The anthracene‐containing copolymers showed reversibility via crosslinking based on photodimerization with ultraviolet irradiation and subsequent thermal dissociation. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2302–2311     

Introducing CdS into two- and three-dimensional photonic crystals

SiO₂/air three-dimensional (3D) periodic structures were fabricated by removing Si layers partially from Si/SiO₂ 3D photonic crystals (PhCs) formed by using autocloning. CdS/SiO₂ 3D periodic structures were formed by introducing CdS into the SiO₂/air structures by the TEA method and photoluminescence (PL) was observed from the introduced CdS. TiO₂/air/CdS two-dimensional (2D) PhCs were also fabricated by introducing CdS into the voids of TiO₂/air 2D periodic structures, in which SiO₂ layers were partially etched out from TiO₂/SiO₂ 2D PhCs fabricated by using autocloning. PL radiating normal to the surface was measured and large polarization dependence was observed.     

Photoelectron spectral intensities of some first transition series elements in metal cyanides containing inequivalent atoms

Photoelectron spectral intensities of some first transition series elements were studied for metal cyanides containing inequivalent atoms. The spectra of low-spin ions coordinated via carbon to the cyanide ion, and of high-spin ions coordinated through nitrogen were separately obtained from manganese, iron, and cobalt cyanides. Metal 2p spectra obtained as sums of the appropriate spectra of low- and high-spin ions were nearly coincident with the spectra of the compounds containing inequivalent atoms. These results show that the intensity of the 2p electron for each atom must include the main peak and perhaps multiplet splitting effects, shake-up effects, and the inelastic scattering tail, and verify the non-interaction nature of the inequivalent atoms in these compounds.     

Determination of the oxidation states of bismuth and copper in superconductor Bi-Ca-Sr-Cu-O by oxidation-reduction titration

Summary The oxidation state of the superconductor Bi-Ca-Sr-Cu-O was determined by two procedures. One was ferrous-chromate titration after dissolution of the sample in manganous nitrate solution. The other was the titration after dissolution in ferrous ion solution. The former procedure gives the concentration of a state like pentavalent bismuth and the latter gives the sum of concentrations of a state like pentavalent bismuth and a state like trivalent copper or peroxide. The result of the titration shows that the superconductor oxide has the state like pentavalent bismuth but not like that of trivalent copper. This is a striking contrast to YBa₂Cu₃O_7–y having a high concentration of the latter state. Although the result was compared with X-ray photoelectron spectra, a clear relationship between them was not obtained.

---

Bestimmung der Oxidationsstufen von Bismut und Kupfer im Supraleiter Bi-Ca-Sr-Cu-O durch Redoxtitration

     

THE PHOTOCONVERSION OF CHENOPODIUM CHLOROPHYLL PROTEIN

Abstract— Changes in the UV absorption spectrum with the photoconversion of Chenopodium chlorophyll protein, CP668 ⇆ CP743, and with the pH change of the CP668 and CP743 solutions, were measured. The change in the absorption spectrum of the apoprotein caused by the pH change was reversible, whereas that caused by the photoconversion was irreversible. The apoprotein may undergo a proton dissociation or association of the phenolic group in tyrosine residues upon pH change. A photooxidation in CP668 (loss of electron) caused by irradiation of CP668 solution may induce a change in the ionization state of some amino acid residues. The isoelectric points of CP668 and CP743 were determined to be 9.3 and 7.2, respectively.     

Inter- and intramolecular differentiation of enantiotopic dioxane acetals through oxazaborolidinone-mediated enantioselective ring-cleavage reaction: kinetic resolution of racemic 1,3-alkanediols and asymmetric desymmetrization of meso-1,3-polyols

Acetals derived from racemic 1,3-alkanediols undergo kinetic resolution in chiral oxazaborolidinone-mediated ring-cleavage reaction with nucleophiles such as enol silanes and allylic silanes. Enantioselectivity of the reaction is affected by nucleophiles, the N-sulfonyl groups of oxazaborolidinones, and the substituents attached to the acetal carbon. For disubstituted acetals rac-1 and for trisubstituted acetal rac-2, derived from syn-2,4-dimethyl-1,3-pentanediol, satisfactory enantioselectivity is obtained by using methallylsilane 7b,c as a nucleophile in combination with N-mesyloxazaborolidinone 4a. On the other hand, enantioselective reaction of trisubstituted acetal rac-3b, derived from anti-2,4-dimethyl-1,3-pentanediol, is realized by using silyl ketene acetal 5e in combination with N-tosyloxazaborolidinone 4b. The reaction conditions optimized for the kinetic resolution, or enantiomer differentiating reaction, of the racemic acetals are successfully applied to asymmetric desymmetrization of meso-1,3-polyols through intramolecular differentiation of the enantiotopic acetal moieties of the bis-acetal derivatives. The utility of the ring-cleavage reaction as a method for enantioselective terminal differentiation of prochiral polyols is demonstrated in convergent asymmetric synthesis of pentol derivative 35 corresponding to the C(19)[bond]C(27) ansa-chain of rifamycin S.     

Asymmetric synthesis of macrocyclic binaphthol dimers using a Sonogashira coupling reaction

Asymmetric synthesis of 24- and 26-membered macrocyclic binaphthol dimers was achieved by assembling a 3,3′-diethynyl-1,1′-bi-2-naphthol unit and 1,2- and 1,3-phenylene units with Sonogashira coupling reaction.     

Generation of ketone dilithio α,β-dianions and their reactions with electrophiles

Ketone dilithio α,β- and α,β′-dianions can be generated by a tin-lithium exchange reaction of the lithium enolate of β-tributyltin substituted ketones. A chelation-aided approach, which employs β-dichlorobutyltin substituted ketones and n-BuLi, is also useful for the generation of ketone α,β-dianions having the Z-geometry at the alkene. The generated dianions can be transformed into substituted ketones by reaction with various carbon electrophiles.