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51.
Yoshizawa M Nagao M Umemoto K Biradha K Fujita M Sakamoto S Yamaguchi K 《Chemical communications (Cambridge, England)》2003,(15):1808-1809
Despite their structural similarity, triangular tetradentate ligands 2b and 2c experience different assembly pathways on complexation with (en)Pd(NO3)2 to give M8L4 tetrahedral (3) and open cone (4) structures, respectively, due to steric restriction by side chains at the corner or on the edge of the ligands. 相似文献
52.
Makoto Wakeshima Nobuyuki Taira Aya Tobo Yasuo Yamaguchi 《Journal of solid state chemistry》2003,174(1):159-164
Magnetic and electrical properties are investigated for quaternary neodymium sulfides BaNd2TS5 (T=Co, Zn) through the specific heat, neutron diffraction, and electrical conductivity measurements. Their electrical conductivities show semiconductive behavior, which follows the Arrhenius temperature dependence with the activation energy of Ea=1.46 eV for BaNd2ZnS5 and Ea=1.19 eV for BaNd2CoS5. The specific heat of BaNd2ZnS5 has a λ-type anomaly at 2.8 K due to the antiferromagnetic ordering of the Nd3+ moments and a Schottky-type anomaly at around 60 K, which results from the crystal field splitting of the 4I9/2 ground state of the Nd3+ ion. The specific heat of BaNd2CoS5 shows two λ-type anomalies at 5.7 K due to the antiferromagnetic ordering of Nd3+ and at 58 K due to the antiferromagnetic ordering of Co2+. The latter overlaps with the Schottky-type anomaly due to the crystal field splitting of the Nd3+ ion. Neutron diffraction measurements for BaNd2CoS5 show that a magnetic arrangement of the Co2+ moments has a collinear antiferromagnetic structure, while that of the Nd3+ moments has a noncollinear one. 相似文献
53.
Makoto OzawaTakaaki Taguchi Takayuki ItohYutaka Ebizuka Kevin I Booker-MilburnG.Richard Stephenson Koji Ichinose 《Tetrahedron》2003,59(44):8793-8798
A novel shunt product was isolated from a disruptant of the actVI-ORFA gene involved in the biosynthesis of actinorhodin (ACT) in Streptomyces coelicolor A3(2). Its structure was elucidated as 1,4-naphthoquinone-8-hydroxy-3-[3(S)-acetoxy-butyric acid], (S)-NHAB, based on NMR, MS, and CD spectroscopic data as well as a single crystal X-ray crystallographic analysis. The formation of (S)-NHAB involves a retro-Claisen type C-C bond cleavage of an ACT biosynthetic intermediate. Feeding experiments with [1-13C] and [2-13C] acetates indicated its biosynthetic origin as a single octaketide chain. The relevant gene product, Act-ORFA, which is a functionally unknown protein, is proposed to play a regulatory role related to the multi-enzymatic steps to ACT production, based on the metabolic profile of its disruptant and the wide distribution of actVI-ORFA homologues in the gene clusters for Streptomyces aromatic polyketides. 相似文献
54.
Star-shaped poly(1,2-phenylenevinylene)s 4-substituted with multiple pendant phenoxyls (2 and 3) were synthesized by polymerizing 2-bromo-4-(acetoxyphenyl)styrene in the presence of 1,3,5-triiodobenzene or 1,3,5-tris(3',5'-diiodophenyl)benzene as the core via a simple one-pot Heck reaction and subsequent hydrolysis, phenolate formation, and heterogeneous oxidation. ESR spectra indicated a delocalized spin distribution into the core parts of the star-shaped molecules. The polyradicals, 2 and 3, were in a high-spin state at low temperature, and the ferromagnetic behavior was enhanced for the polyradical with a higher molecular weight. Although an average S of 3 remained at 3/2 to 4/2, the polyradical 2 even with a spin concentration of 0.8 spin/unit revealed an average S of 7/2 to 8/2. The 1,3,5-benzene core acted as an effective magnetic coupler to align the spins of the pendant phenoxyls through the star-shaped pi-conjugated backbone. 相似文献
55.
Mizukami Fujio Maeda Kazuyuki Toba Makoto Sano Tsuneji Niwa Shu-ich Miyazaki Mitsuharu Kojima Kunihiko 《Journal of Sol-Gel Science and Technology》1997,8(1-3):101-106
The preparation of mullite by the sol-gel method using organic polydentate ligands and the effect of the raw materials and
organic polydentate ligands on the formation of mullite were investigated. Two series of samples were prepared using tetraethoxyorthosilicate
(TEOS) and aluminum nitrate nonahydrate, or dibutoxyethylacetoacetatoaluminum (Al(OBu)2(AcAcEt)) as the silica and alumina sources, respectively, and using ethylene glycol (EG), 1,3-propanediol (PD), 1,3-butanediol
(BD), 2-methyl-2, 4-pentanediol (MPD), diethlene glycol monoethyl ether (DEME) and ethoxyethanol as the ligands. When the
alumina source was aluminum nitrate nonahydrate, mullite was apt to appear in the order of EG>PD>MPD. When Al(OBu)2(AcAcEt) was the alumina source, the tendency toward the appearance of mullite crystalline phase was EG>BD>DEME>MPD. Between
the two alumina sources, aluminum nitrate nonahydrate gave mullite much easier than Al(OBu)2(AcAcEt). These relationships were discussed from the viewpoints of the coordination ability of the ligands and the miscibility
between the silica and alumina. 相似文献
56.
Stereoselective synthesis of (3S,4S)- and (3R,4R)-series of 3,4-dihydroxyglutamic acids was investigated. The key reaction in this synthesis is asymmetric reduction of meso-imide derived from meso-tartaric acid. Lewis acid-promoted cyanation of the obtained optically active lactam via the acyliminium intermediate followed by standard deprotection procedure afforded the desired 3,4-dihydroxyglutamic acids. 相似文献
57.
Diversity-oriented organic synthesis (DOS) is a key concept for construction of skeletally diverse small molecule libraries to discover drug-like small molecules. Here, we describe a DOS class to transform a complex 7-oxanorbornene skeleton, which is readily accessible by a tandem Ugi/Diels-Alder reaction, into two heterotricycle skeletons selectively by using tandem ROM/CM/RCM reaction. In the present study, the mode of cyclization is pre-encoded by building blocks used in the complexity-generating tandem Ugi/Diels-Alder reaction. Since variable alkenes can be used in the CM reaction, our approach can be extended to construct both skeleton- and appendage-diverse small molecule libraries. 相似文献
58.
2,2′-Dipyridyl-2-furancarbothiohydrazone (DPFTH) was used for the spectrophotometric determination of trace amount of iron(II) after the extraction process. Iron(II) can be quantitatively extracted with DPFTH in benzene from aqueous solution buffered to 3.0–8.0. The extracted species has absorption maxima at 440, 477, and 738 nm and obeyed Beer's law over the range 0–40 μg of iron in 10 ml at 738 nm. The molar absorptivity at this wave length is 1.17 × 104 liters mole?1 cm?1. The proposed method is relatively selective for iron(II) and is satisfactorily applied to the determination of the total iron in natural waters. The proton dissociation constants of the ligand determined spectrophotometrically were pKa1 = 2.88 and pKa1 = 6.70 at 25 °C and μ = 0.1. 相似文献
59.
Kentaro Ageishi Takeshi Endo Makoto Okawara 《Journal of polymer science. Part A, Polymer chemistry》1981,19(5):1085-1090
The behavior of viologen polymer (P-V2+) as an electron transfer catalyst in the reaction of hydrogen generation was studied. In the photoirradiation system, which contains triethanolamine (TEA), Ru(bpy)3+3, and P-V2+, the amount of hydrogen evolution was less than methyl viologen (MV2+); P-V2+, however, was more effective in sodium dithionite as the electron donor and showed higher initial rates than MV2+. 相似文献
60.
Hiroshi Takeuchi Makoto Nakagawa Takayuki Saito Toru Egawa Kiyoshi Tanaka Shigehiro Konaka Toshiyuki Mitsuhashi 《International journal of quantum chemistry》1994,52(6):1339-1348
The energy spectra of free water molecules were measured at scattering angles 2θ ranging from 10.5° to 75.7°, using an angle-dispersive-type diffractometer and synchrotron radiation as an X-ray source. A silicon (111) monochrometer was used to obtain incident X-rays with the wavelengths of (1.543/n) Å (n = 1,3,4,5). Observed inelastic scattering peaks are clearly separated from eleastic ones at s values [s = (4π/λ) sin Å] larger than 8 Å?1. The increase of the separation with an increasing s value was consistent with the classical theory of the Compton shift. The total (elastic plus inelastic) intensities were obtained over a range of s = 0.74–5.0 Å?1. Experimental difference intensities Δσee and Δσne were obtained separately by combining the X-ray and high-energy electron scattering data. The experimental results are in reasonable agreement with the theoretical intensities calculated from SCF and CI molecular wave functions with a basis set of double-zeta plus polarization functions. © 1994 John Wiley & Sons, Inc. 相似文献