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11.
3-Acetyl-2-oxazolone readily undergoes free-radical homopolymerization as well as telomerization with polyhalomethanes, in which low telomer formation is highly stereo- and regio-selective. 相似文献
12.
Yoshihiro Itoh Masamitsu Inoue Tomoko Takahashi Akira Hachimori Satoshi Suzuki 《Journal of polymer science. Part A, Polymer chemistry》1995,33(7):1069-1074
Alternating and random copolymers of 9-phenanthrylmethyl methacrylate or 2-(9-carbazolyl)ethyl methacrylate with styrene were synthesized and their fluorescence properties were examined. There was no noticeable difference in the spectral features of the alternating and random copolymers in tetrahydrofuran (THF), demonstrating that this type of polymers have no quenching sites in the polymer chains. The fluorescence quenching studies indicated that the alternating copolymers permitted singlet-state energy migration as efficiently as the corresponding random copolymers but less efficiently than the random copolymers with higher chromophore contents. These results strongly suggest that to be chromophores close to each other is most important for facilitation of an intramolecular energy migration. © 1995 John Wiley & Sons, Inc. 相似文献
13.
Imahori H Fujimoto A Kang S Hotta H Yoshida K Umeyama T Matano Y Isoda S Isosomppi M Tkachenko NV Lemmetyinen H 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(24):7265-7275
Novel gold nanoparticles modified with a mixed self-assembled monolayer of porphyrin alkanethiol and short-chain alkanethiol were prepared (first step) to examine the size and shape effects of surface holes (host) on porphyrin-modified gold nanoparticles. The porphyrin-modified gold nanoparticles with a size of about 10 nm incorporated C60 molecules (guest) into the large, bucket-shaped holes, leading to the formation of a supramolecular complex of porphyrin-C60 composites (second step). Large composite clusters with a size of 200-400 nm were grown from the supramolecular complex of porphyrin-C60 composites in mixed solvents (third step) and deposited electrophoretically onto nanostructured SnO2 electrodes (fourth step). Differences in the porphyrin:C60 ratio were found to affect the structures and photoelectrochemical properties of the composite clusters in mixed solvents as well as on the SnO2 electrodes. The photoelectrochemical performance of a photoelectrochemical device consisting of SnO2 electrodes modified with the porphyrin-C60 composites was enhanced relative to a reference system with small, wedged-shaped surface holes on the gold nanoparticle. Time-resolved transient absorption spectroscopy with fluorescence lifetime measurements suggest the occurrence of ultrafast electron transfer from the porphyrin excited singlet states to C60 or the formation of a partial charge-transfer state in the composite clusters of supramolecular complexes formed between porphyrin and C60 leading to efficient photocurrent generation in the system. Elucidation of the relationship between host-guest interactions and photoelectrochemical function in the present system will provide valuable information on the design of molecular devices and machines including molecular photovoltaics. 相似文献
14.
Kazuaki Ito Akane Suzuki Naoto Ito Hiroyuki Teraura Yoshihiro Ohba 《Journal of heterocyclic chemistry》2003,40(3):405-410
Dithia‐tetrahomodiaza‐calix[4]arenes were synthesized by the cyclization reactions of bis(3‐(chloro‐methyl)‐2‐hydroxyphenyl)sulfide with cystine peptides in moderate yields. Conformational analysis of the macrocycles by using nmr spectroscopy reveled that the cyclophanes adopt a cone‐like form as a preferable conformation and the cystine bridge moiety is incorporated in the cavity. The calixarene analogs can extract transion metals such as Zn2+ and Cu2+ ions from an aqueous phase into chloroform. 相似文献
15.
Mieko Urano Hitoshi Kagawa Yoshihiro Harigaya Shaoshun Li Masayuki Onda 《Journal of heterocyclic chemistry》1991,28(8):1845-1847
A total synthesis of optically pure (+)-catechin pentaacetate has been established using the (-)-chalcon epoxide (100% ee) derived from 3,4,2′,4′,6′-pentakis(methoxymethoxy)chalcon as the starting material. The optical purity of the product is confirmed by 1H nmr analysis in the presence of a shift reagent. 相似文献
16.
Tris(2-aminoethyl)amine derivatives with appended urea and sulfonamide groups are shown to facilitate the translocation of fluorescent phospholipid probes and endogenous phosphatidylserine across vesicle and erythrocyte cell membranes. The synthetic translocases appear to operate by binding to the phospholipid head groups and forming lipophilic supramolecular complexes which diffuse through the non-polar interior of the bilayer membrane. 相似文献
17.
Akitomo Tachibana Yoshihiro Asai Shogo Ikeuchi Shigeru Ishikawa Tokio Yamabe 《Theoretical chemistry accounts》1990,78(1):1-9
Summary The vibronic character of this molecular device has been studied using isomorphic electron orbitals. The leading role of the softest vibrational mode for the electron transport process is stressed by the quantum mechanical treatment of the rearrangement operator. The theory was used to investigate the possible function of the soliton valve, which has been suggested as a switching tip. The electronic flexibility of the cyclopropenyl radical with respect to molecular vibrations, which is important for the function of the molecular device, is well characterized by the hardness and softness of the electron structure in terms of the orbital energy-occupation number correlation diagram. 相似文献
18.
A quantum chemical study of interchain hopping model of negatively charged solitons in polyacetylene
Akitomo Tachibana Shigeru Ishikawa Yoshihiro Asai Hideki Katagiri Tokio Yamabe 《International journal of quantum chemistry》1992,41(3):461-474
Phonon-assisted interchain hopping of negatively charged solitons in polyacetylene has been studied using a local chemical reaction model CH + CH4 → CH4 + CH. Quantum chemical characteristics of the electron transfer process have been analyzed in terms of the dynamic electron density and the mutual polarization moment. The CH stretching vibrational motion of CH4, which is a local model of the sp3 defect, has been found to play a significant role for the electron transfer. The excitation of the corresponding vibrational mode of the sp3 defect would promote the interchain hopping of the charged soliton. The electron transfer process has also been studied in terms of the “regional” density functional theory. It has been shown that the driving force of the electron transfer is represented by the regional chemical potentials. 相似文献
19.
Konda-Yamada Y Asano K Satou T Monma S Sakayanagi M Satou N Takeda K Harigaya Y 《Chemical & pharmaceutical bulletin》2005,53(5):529-536
Oxopropyl E-(pyrrolidine-2-ylidene)glycinamide (5c) and allyl E-(pyrrolidine-2-ylidene)glycinate (5d) were effectively synthesized from 2,3,5-tri-O-benzyl-4-O-tert-butyldimethylsilyl(TBDMS)-D-arabinal (7) using intramolecular 1,3-dipolar cyclic reaction of azide and olefin as a key reaction. These results proved this cyclic reaction should be applicable for the synthesis of various (pyrrolidine-2-ylidene)glycinate and glycinamide. In addition, the development of a synthetic route for the precursor of an unsaturated cyclic dehydro amino acid involved in azinomycins (carzinophilin) using relating glycinate, methyl E-(pyrrolidine-2-ylidene)glycinate (5a) was described. 相似文献
20.
A reliable and sensitive capillary gas chromatographic-mass spectrometric method was developed for the detection and determination of diazepam and its major metabolite, N-desmethyldiazepam, in human material. Medazepam served as the internal standard. Quantitative determination was achieved using mass fragmentography with selected ions of m/z 256 for diazepam and m/z 242 for N-desmethyldiazepam and medazepam. The limit of detection was 1 ng/g and the recoveries were 98.54 +/- 3.95% for diazepam and 98.66 +/- 6.48% for N-desmethyldiazepam. The calibration graph was linear over the concentration range from 1.0 ng/g to 1.0 microgram/g for diazepam and N-desmethyldiazepam. Using this method, trace amounts of diazepam and N-desmethyldiazepam were detected in the tissues of an autopsied individual. 相似文献