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11.
Dithienylethenes with a novel photochromic performance 总被引:2,自引:0,他引:2
Dithienylethenes with low decoloration quantum yields and thermal reversibility at high temperature above 100 degrees C were prepared. Introduction of bulky alkoxy substituents at 2- and 2'-positions of the thiophene rings strongly suppressed the cycloreversion quantum yields. The quantum yields were lower than 10(-3), and the photogenerated color remained stable enough under room light. On the other hand, the bulky alkoxy substituent decreased the thermal stability of the colored closed-ring isomers at high temperature. The color of the dithienylethene with cyclohexyloxy substituents faded out in less than 1 min at 160 degrees C. 相似文献
12.
The concept, the present status, key issues and future prospects of a novel hexagonal binary decision diagram (BDD) quantum circuit approach for III–V quantum large-scale integrated circuits (QLSIs) are presented and discussed. In this approach, the BDD logic circuits are implemented on III–V semiconductor-based hexagonal nanowire networks controlled by nanoscale Schottky gates. The hexagonal BDD QLSIs can operate at delay-power products near the quantum limit in the quantum regime as well as in the many-electron classical regime. To demonstrate the feasibility of the present approach, GaAs Schottky wrap gate (WPG)-based single-electron BDD node devices and their integrated circuits were fabricated and their proper operations were confirmed. Selectively grown InGaAs sub-10 nm quantum wires and their hexagonal networks have been investigated to form high-density hexagonal BDD QLSIs operating in the quantum regime at room temperature. 相似文献
13.
Photochromic performance of diarylethene single crystals was controlled by crystal engineering using non-covalent aromatic-aromatic interactions as the directional intermolecular force. A diarylethene derivative with two pentafluorophenyl groups, 1,2-bis(2-methyl-5-pentafluorophenyl-3-thienyl)perfluorocyclopentene (1a), formed stoichiometric co-crystals with benzene (Bz) and naphthalene (Np) by aryl-perfluoroaryl interactions. Face-to-face pi-stacking interactions between the pentafluorophenyl groups of 1a and the aromatic molecules are responsible for 2:1 and 1:1 stoichiometric compositions in 1a/Bz and 1a/Np co-crystals, respectively. The diarylethene underwent thermally stable and photoreversible photochromic reactions in a homo-crystal of 1a and co-crystals 1a/Bz and 1a/Np. The absorption spectra of the photogenerated closed-ring isomers varied depending on the conformation of the diarylethene molecules packed in the crystals. The diarylethene 1a also formed 1:1 stoichiometric co-crystals with different kinds of diarylethenes, 1,2-bis(2-ethyl-5-phenyl-3-thienyl)perfluorocyclopentene (2a) and 1,2-bis[2-methyl-5-(1-naphthyl)-3-thienyl]perfluorocyclopentene (3a). Both co-crystals 1a/2a and 1a/3a showed photochromism. Although 1a, 2a, and 3a underwent efficient photocyclization reactions in their homo-crystals, highly selective photocyclization reactions of 2a or 3a were observed in the co-crystals. The selective reactions were confirmed by HPLC and X-ray crystallography. Excited energy transfers from 1a to 2a and from 1a to 3a are considered to occur and cause the selective reactions. 相似文献
14.
Chiral Carboxylic Acid Enabled Achiral Rhodium(III)‐Catalyzed Enantioselective C−H Functionalization 下载免费PDF全文
Dr. Luqing Lin Seiya Fukagawa Daichi Sekine Eiki Tomita Dr. Tatsuhiko Yoshino Prof. Dr. Shigeki Matsunaga 《Angewandte Chemie (International ed. in English)》2018,57(37):12048-12052
Reported is an achiral CpxRhIII/chiral carboxylic acid catalyzed asymmetric C?H alkylation of diarylmethanamines with a diazomalonate, followed by cyclization and decarboxylation to afford 1,4‐dihydroisoquinolin‐3(2H)‐one. Secondary alkylamines as well as nonprotected primary alkylamines underwent the transformation with high enantioselectivities (up to 98.5:1.5 e.r.) by using a newly developed chiral carboxylic acid as the sole source of chirality to achieve enantioselective C?H cleavage by a concerted metalation‐deprotonation mechanism. 相似文献
15.
A neutron calibration field using 241Am–Li sources and a moderator was designed to simulate the neutron fields found outside a reactor. The moderating assembly selected for the design calculation consists of a cube of graphite blocks with dimensions of 50 cm by 50 cm by 50 cm, in which the 241Am–Li sources are placed. Monte Carlo calculations revealed the optimal depth of the source to be 15 cm. This moderated neutron source can be used to provide a test field that has a large number of intermediate energy neutrons with a small portion of MeV component. 相似文献
16.
Kosuke Makiguchi Seiya Kikuchi Toshifumi Satoh Toyoji Kakuchi 《Journal of polymer science. Part A, Polymer chemistry》2013,51(11):2455-2463
The ring‐opening polymerization (ROP) of cyclic esters, such as ε‐caprolactone, 1,5‐dioxepan‐2‐one, and racemic lactide using the combination of 3‐phenyl‐1‐propanol as the initiator and triflimide (HNTf2) as the catalyst at room temperature with the [monomer]0/[initiator]0 ratio of 50/1 was investigated. The polymerizations homogeneously proceeded to afford poly(ε‐caprolactone) (PCL), poly(1,5‐dioxepan‐2‐one) (PDXO), and polylactide (PLA) with controlled molecular weights and narrow polydispersity indices. The molecular weight determined from an 1H NMR analysis (PCL, Mn,NMR = 5380; PDXO, Mn,NMR = 5820; PLA, Mn,NMR = 6490) showed good agreement with the calculated values. The 1H NMR and matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry analyses strongly indicated that the obtained compounds were the desired polyesters. The kinetic measurements confirmed the controlled/living nature for the HNTf2‐catalyzed ROP of cyclic esters. A series of functional alcohols, such as propargyl alcohol, 6‐azido‐1‐hexanol, N‐(2‐hydroxyethyl)maleimide, 5‐hexen‐1‐ol, and 2‐hydroxyethyl methacrylate, successfully produced end‐functionalized polyesters. In addition, poly(ethylene glycol)‐block‐polyester, poly(δ‐valerolactone)‐block‐poly(ε‐caprolactone), and poly(ε‐caprolactone)‐block‐polylactide were synthesized using the HNTf2‐catalyzed ROP. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2455–2463 相似文献
17.
It has been demonstrated that a glass-like silicone ladder-type polymer permits one to homogeneously incorporate high amounts of ionophores into the covalently-bonded double chain structure. Furthermore, by making use of this feature, we have successfully fabricated an iodide ion-sensitive field-effect transistor based on two kinds of ionophores and silicone ladder polymer matrix. As ionophores, 5,10,15,20-tetraphenyl-21H,23H-porphyrin and dimethyloctadecyl-3-trimethoxylsilylpropylammonium chloride were homogeneously incorporated into the matrix. The ion-sensitive field-effect transistor showed a linear potential response ranging in the I- concentration between 1.0 x 10(-5) and 1.0 x 10(-1) M. The selectivity coefficients for I- towards interferences of ClO4- and NO3- were estimated to be Kpot(I-,ClO4-) approximately 6.2 x 10(-4) and Kpot(I-,No3-) approximately 4.9 x 10(-4). The matrix has proved to be so stable that the selectivity coefficients have not been altered over six months. 相似文献
18.
H. Nagai N. Oyama H. Yoshie A. Tsujimura 《Journal of magnetism and magnetic materials》1987,70(1-3):171-172
The educed Gd atoms in the X-structure (Th6Mn23-type) of Gd(Fe1−xMnx)2 were magnetically investigated by comparing with Gd6(Fe1−yMny)23 whose structure is Th6Mn23-type. The magnetic properties of Gd(Fe1−xMnx)2 (0.4≤x≤0.7) were observed to be quite similar to those of Gd6(Fe1−yMny)23 (0.4≤y≤0.7). 相似文献
19.
A triangulation of a closed surface is said to be d-covered if all of its edges are covered by vertices of degree d. We shall give constructive characterizations of 5- and 6-covered triangulations. Received: July 17, 1998?Final version received: January 12, 2000 相似文献
20.
Tatsumoto Nakahama Takayoshi Mukaiyama Daichi Kitagawa Seiya Kobatake 《Research on Chemical Intermediates》2017,43(10):5321-5336
Efficient fluorescence on/off switching of a dyad consisting of a photochromic diarylethene and a fluorescence dye based on excited state intramolecular proton transfer (ESIPT) was designed and demonstrated. Diarylethenes linked to (2-(2-methoxy-5-methylphenyl)benzothiazol-6-yl)- and (2-(2-hydroxy-5-methylphenyl)benzothiazol-6-yl)-9,9-dioctylfluorene moieties (1a and 2a, respectively) exhibited fluorescence on/off switching upon alternating irradiation with ultraviolet and visible light in various solvents. The fluorescence on/off contrast of 2a was found to be higher than that of 1a in n-hexane because the overlap integral between the absorption spectrum of the diarylethene closed-ring form and the fluorescence spectrum of 2a is larger than that of 1a. Diarylethene 2a exhibited green fluorescence with large Stokes shift in n-hexane, which is ascribed to the ESIPT process from the enol form to the keto form. In contrast, the fluorescence of 2a in N,N-dimethylsulfoxide (DMSO) was mainly observed as blue fluorescence from enol form, while diarylethene 1a exhibited blue fluorescence in n-hexane and DMSO. The fluorescence on/off contrast of 2a in n-hexane was higher than that in DMSO because of the difference in the spectral overlaps in n-hexane and DMSO. 相似文献