Asymmetric oxidative coupling polymerization affording polynaphthylene with 1,1′-bi-2-naphthol units

The oxidative coupling polymerizations of racemic-, (R)-, and (S)-2,2′-dimethoxymethoxy-1,1′-binaphthalene-3,3′-diols were carried out with a copper catalyst with various ligands, such as N,N,N′,N′-tetramethylethylenediamine (TMEDA), (S)-(+)-1-(2-pyrrolidinylmethyl)pyrrolidine, (−)-sparteine, and (S)-(−)-2,2′-isopropylidenebis(4-phenyl-2-oxazoline) [(−)-Phbox], under an O₂ atmosphere. For example, a 10/1 (v/v) MeOH · H₂O-insoluble polymer with a number-average molecular weight of 3.8 × 10³, from a polymerization with CuCl–TMEDA followed by acetylation of the hydroxyl groups, was obtained in a 71% yield. Polymerization with (−)-Phbox proceeded in an S-selective manner to give a polymer with the highest negative specific rotation from the (S)-monomer. The obtained polymer was successfully converted into a polymer with the optically pure 1,1′-bi-2-naphthol unit based on the original monomer structure, which could be used as a polymeric chiral auxiliary and showed catalytic activity for the asymmetric diethylzinc addition reaction to aldehydes. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4528–4534, 2004     

Boron Diiminate with Aggregation‐Induced Emission and Crystallization‐Induced Emission‐Enhancement Characteristics

Organoboron complexes having aggregation‐ and crystalization‐induced emission properties are presented. The series of boron diiminates were synthesized and the emission behaviors of the synthesized compounds were investigated. Finally, it was found that significant enhancement of the emission depended on the crystallinity in the solid states.     

Cationic polymerization of seven‐membered cyclic monothiocarbonate 1,3‐dioxepan‐2‐thione

The cationic ring‐opening polymerization of a seven‐membered cyclic monothiocarbonate, 1,3‐dioxepan‐2‐thione, produced a soluble polymer through the selective isomerization of thiocarbonyl to a carbonyl group {? [SC(C?O)O(CH₂)₄]_n? }. The molecular weights of the polymer could be controlled by the feed ratio of the monomer to the initiators or the conversion of the monomer during the polymerization, although some termination reactions occurred after the complete consumption of the monomer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1014–1018, 2005     

Raman spectra of Si-implanted silicon on sapphire

Raman scattering from Si-implantation-amorphized and subsequently thermally recrystallized silicon on sapphire (SOS) shows that optical phonon frequencies of silicon well correlate with the recrystallization temperature rather than the epitaxial temperature. This implies that the strain in as-epitaxial SOS has been relieved and replaced by the one which depends upon the recrystallization temperature.     

Identification of isomers and subsidiary colors in commercial Fast Green FCF (FD&C Green No. 3, Food Green No. 3) by liquid chromatography-mass spectrometry and comparison between amounts of the subsidiary colors by high-performance liquid chromatography and thin-layer chromatography-spectrophotometry

The existence of five of the six expected isomers in commercial Fast Green FCF (G3: Food Green No. 3, FD&C Green No. 3, CAS No. 2353-45-9, C.I. No. 42053), the main product of which is m,m-G3 and the sub-products of which are presumed to be m,p-G3, o,m-G3, p,p-G3, o,p-G3 and o,o-G3, was confirmed using LC/MS, and the levels of the isomers, m,m-G3, m,p-G3, p,p-G3, o,m-G3 and o,p-G3, were determined by analytical HPLC. The existence of seven subsidiary colors that were decomposed from G3 was also confirmed using LC/MS. The levels of the subsidiary colors in ethanol extracts from TLC were determined by HPLC and spectrophotometry, and these results were compared. It was clear that the values determined by TLC-spectrophotometry were higher than those by HPLC. It was recommended that the levels of subsidiary colors in G3 should be determined by HPLC.     

Multistep magnetization plateaus in the Shastry-Sutherland system TbB4

We report high-field magnetization and magnetostriction measurements on the rare-earth-metal tetraboride TbB4, in which the Tb moments form a Shastry-Sutherland lattice in the tetragonal basal plane. A number of magnetization plateaus appear when the magnetic field is perpendicular to the magnetic easy plane. We propose that the magnetization plateaus arise from the combined effect of magnetic frustration and quadrupole interaction in the unique two-dimensional network.     

Hybridized nature of pseudogap in Kondo insulators CeRhSb and CeRhAs

We studied the electronic structure of Kondo insulators CeRhSb and CeRhAs using high-resolution photoemission spectroscopy. We found that the 4f-derived density of states shows a depletion (pseudogap) at E(F) in contrast to metallic Kondo materials. It was found that the size of the f pseudogap is smaller than that of conduction electrons ( c pseudogap) while both scale well with the Kondo temperature. The present results indicate that the hybridization between 4f and conduction electrons near E(F) is essential for the Kondo gap in the Ce-based compounds.