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961.
962.
Two polycatenar materials composed of a four‐aromatic‐ring core with a perfluorinated moiety attached in one terminal position through either butylene‐ or pentylene spacer groups, and three tetradecyloxy chains at the other end (abbreviated as 14PC4F and 14PC5F), were investigated to study the effect of pressure on the phase transition behaviour. A polarizing optical microscope equipped with a high pressure optical hot stage, was used for the purpose. The T vs. P phase diagrams of 14PC4F and 14PC5F were constructed in the pressure region up to 100 MPa. 14PC4F showed the stable crystal (Cr1)–columnar tetragonal (Coltet)–smectic A (SmA)–columnar hexagonal (Colh)–isoropic liquid (I) phase transition sequence under all pressures. 14PC5F exhibited the phase sequence metastable crystal (Cr2)–cubic (Cub)–Coltet–SmA–I in a melt‐cooled sample on heating under pressure. But when the melt‐cooled Cr2 sample was annealed at 52–54°C for 2–3 h, the stable crystal (Cr1) was formed slowly, giving a stable Cr1–Cub–Coltet–SmA–I phase sequence. The temperature region of the stable cubic phase broadened with increasing pressure. Furthermore a new mesophase of 14PC5F was pressure‐induced between the I and SmA phases on cooling at pressures above about 16 MPa. Since the monotropic mesophase exhibited a texture very similar to that of the high temperature Colh phase of 14PC4F with planar orientation, the new phase was assigned at a high temperature columnar hexagonal phase of 14PC5F. 相似文献
963.
Several 4-(oligodimethylsiloxyl)alkoxybenzoic acids and their hydrogen-bonded complexes with 4,4-dipyridyl or 1,2-bis(4-pyridyl)ethane were prepared and their phase behaviour studied by DSC and polarized optical microscopy. The neat acids showed no liquid crystalline phases. The 4,4-dipyridyl complex of 4-(n-heptamethyltrisiloxyl)hexyloxybenzoic acid (Si3C6BA) exhibits an optically isotropic, highly viscous liquid crystalline phase below a smectic A phase. The 1,2-bis(4-pyridyl)ethane complex of Si3C6BA also shows an optically isotropic liquid crystalline phase above its smectic C phase. Its behaviour is similar to that of the well known cubic D phase found in 4-n-alkoxy-3-nitrobiphenyl-4-carboxylic acids. In the hydrogenbonded mesogens studied herein, the cubic phase appears to assemble spontaneously in order to take account of the chemical incompatibility between the siloxane moiety terminating the H-bonded complex and the stiff aromatic cores. The transition temperatures of the cubic phases in these materials is around 100oC, hence they are amenable to a variety of physical measurements. 相似文献
964.
Hajime Shigemitsu Dr. Ichiro Hisaki Eriko Kometani Daisuke Yasumiya Yuu Sakamoto Keisuke Osaka Dr. Tejender S. Thakur Dr. Akinori Saeki Prof. Dr. Shu Seki Dr. Fumiko Kimura Prof. Dr. Tsunehisa Kimura Dr. Norimitsu Tohnai Prof. Dr. Mikiji Miyata 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(45):15366-15377
Supramolecular nanofibers (SNFs) composed of low‐molecular‐weight π‐conjugated molecules exhibit attractive optical and electrical properties and are expected to be the next optoelectronic materials. In this work, five crystalline SNFs have been constructed from three dehydrobenzoannulene (DBA) derivatives. The DBAs were designed to assemble in one dimension in a strategy based on anisotropic crystal growth. The crystallinity of the SNFs allowed the molecular arrangements in the SNFs to be determined. Therefore the mechanism of construction and correlations between the molecular arrangements and optical and electrical properties could be considered. The results clearly indicate that the properties of the SNFs are affected by the chemical structures and molecular arrangements. Moreover, one of the SNFs exhibits a high charge‐carrier mobility (Σμ=0.61 cm2 V?1 s?1) because of its crystallinity and appropriate molecular arrangement. This systematic experimental study based on a proposed strategy has provided information for improving the electrical properties of SNFs. This strategy will lead to highly functional SNFs. 相似文献
965.
Kazuya Ishigai Prof. Dr. Haruhiko Fuwa Keisuke Hashizume Ryo Fukazawa Dr. Yuko Cho Prof. Dr. Mari Yotsu‐Yamashita Prof. Dr. Makoto Sasaki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(17):5276-5288
In this study, we report the first total synthesis and complete stereostructure of gambieric acid A, a potent antifungal polycyclic ether metabolite, in detail. The A/B‐ring exocyclic enol ether 32 was prepared through a Suzuki–Miyaura coupling of the B‐ring vinyl iodide 18 and the alkylborate 33 and subsequent closure of the A‐ring by using diastereoselective bromoetherification as the key transformation. Suzuki–Miyaura coupling of 32 with acetate‐derived enol phosphate 49 , followed by ring‐closing metathesis of the derived diene, produced the D‐ring. Subsequent closure of the C‐ring through a mixed thioacetalization completed the synthesis of the A/BCD‐ring fragment 8 . The A/BCD‐ and F′GHIJ‐ring fragments (i.e., 8 and 9 ) were assembled through Suzuki–Miyaura coupling. The C25 stereogenic center was elaborated by exploiting the intrinsic conformational property of the seven‐membered F′‐ring. After the oxidative cleavage of the F′‐ring, the E‐ring was formed as a cyclic mixed thioacetal (i.e., 70 ) and then stereoselectively allylated by using glycosylation chemistry. Ring‐closing metathesis of the diene 3 thus obtained closed the F‐ring and completed the polycyclic ether skeleton. Finally, the J‐ring side chain was introduced by using a Julia–Kocienski olefination in the presence of CeCl3 to complete the total synthesis of gambieric acid A ( 1 ), thereby unambiguously establishing its complete stereostructure. The present total synthesis enabled us to evaluate the antifungal and antiproliferative activities of 1 and several synthetic analogues. 相似文献
966.
Masataka Nishikawa Tsugio Mizoguchi Yukiko Dokiya Shinichi Bessho Hiroki Haraguchi 《International journal of environmental analytical chemistry》2013,93(4):591-598
Abstract The concentration of mercury in airborne particles was determined in samples collected at heights of 1m and at 175m up the Meteorological Observation Tower (213m) at the Meteorological Research Institute, Tsukuba between August 1985 and April 1986. The concentrations of particulate mercury at the two heights were compared with gaseous mercury levels at a height of 10m and with other chemical components in the particles. The concentrations of particulate mercury at both heights showed no positive correlation with those of gaseous mercury, total suspended particles, sulfate, chloride, sodium or calcium. However, there was some positive correlation between particulate mercury and nitrate concentrations especially at 175m; the concentrations of these components were found to be high when the wind direction was southwesterly. These results suggest that these components were transported from the Tokyo Metropolitan area. 相似文献
967.
Yasuharu Yoshimi Shota Hayashi Keisuke Nishikawa Yoshiki Okita Kousuke Maeda Toshio Morita Tatsuya Itou 《Research on Chemical Intermediates》2013,39(1):397-402
Decarboxylative radical addition of N-(t-butoxycarbonyl)amino acids to acrylonitrile was achieved by excitation of 1,4-dicyanonaphthalene. The photochemical decarboxylation was highly dependent on the dicyanoarenes used as electron acceptors and on addition of a base. The photoreaction proceeded smoothly to yield the decarboxylative adduct even in the presence of only a catalytic amount of 1,4-dicyanonaphthalene. 相似文献
968.
Keisuke Nogoshi Daisuke Domon Kenshu Fujiwara Natsumi Kawamura Ryo Katoono Hidetoshi Kawai Takanori Suzuki 《Tetrahedron letters》2013,54(7):676-680
The EF-ring of ciguatoxin 3C, a marine toxin from the dinoflagellate Gambierdiscus toxicus, was stereoselectively synthesized by iterative use of a cyclic ether formation process based on chirality-transferring Ireland-Claisen rearrangement and ring-closing olefin metathesis. 相似文献
969.
970.