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111.
It is found that a ratio between the oscillator strengths of the optical absorption calculated from the dipole length formalism
and those calculated from the dipole velocity formalism is almost constant for many conjugated molecules if the calculation
is made using the theoretically obtained transition energy. The value of the ratio becomes very sensitive to the molecular
geometry if the calculation is made using the experimentally obtained transition energy. The origin of the constancy of the
ratio is discussed. 相似文献
112.
Zenjiro Osawa Chiharu Moriyama Hiroko Nakano 《Journal of polymer science. Part A, Polymer chemistry》1981,19(8):1877-1884
Reaction of pol(vinyl alcohol) (PVA) with superoxide anion was carried out in a dimethyl sulfoxide solution at 40°C under nitrogen and changes in the yield of recovered polymer, molecular weight, and chemical structure were examined. Appreciable decreases in the yield of recovered polymer and molecular weight were observed during the reaction, which indicated that a main chain scission of the polymer had occurred. Residual acetyl groups identified by the absorption peaks at ca. 1720 and 1250 cm?1 in infrared (IR) spectra were removed rapidly and β-diketone groups identified by the peaks at ca. 1640 and 1560 cm?1 in IR spectra and at ca. 255 nm in ultraviolet (UV) spectra were formed during the reaction. Formation of carboxylate groups was also assumed. The reaction mechanism was discussed on the basis of the results obtained. 相似文献
113.
Course of cyclization of dienols, polyenes, and dienyne mediated by mercuric salts were controlled by stability of cationic intermediates and source of mercuric salts. Reaction of (E)-5,9-dimethyl-4,8-decadiene-1-ol with mercuric acetate gave the intramolecular oxymercuration product, whereas one with mercuric triflate produced the olefin cyclization products. 相似文献
114.
[reaction: see text] A thiolate/alkyl halide coupling reaction in aqueous media provides a one-step synthesis of fullerene glycoconjugates bearing five carbohydrate groups in good yield by using stoichiometric amounts of reactants, without recourse to hydroxy group protection. The sulfide-connection methodology is also useful for synthesis of simpler amphiphilic fullerene molecules, such as one bearing five carboxylic acid groups. 相似文献
115.
116.
Poly[2-(perfluorooctyl)ethyl acrylate-co-poly(ethylene glycol) methacrylate], P(POA-co-PEGm) was prepared as a new surfactant for scCO2. The random copolymer was obtained by the radical polymerization of 2-(perfluorooctyl)ethyl acrylate (POA) and poly(ethylene
glycol) methacrylate (PEGm) in DMF. The molar ratio of the POA and PEGm units in the copolymer was POA/PEGm = 0.972/0.028
by 1H NMR. The molecular weight and molecular weight distribution were estimated by size exclusion chromatography to be Mn = 133,000
and Mw/Mn = 8.25, respectively. It was suggested that the copolymer formed micellar aggregates with the cores of the PEGm
chains in scCO2, based on the analyses of the copolymer in hexafluorobenzene by 1H NMR and dynamic light scattering. The copolymer was soluble in scCO2 and had a cloud point at a much higher pressure than the critical pressure. It was found that the copolymer solubilized CO2-insoluble proteins such as bovine serum albumin and subtilisin Carlsberg in scCO2. The solubility of the copolymer was not influenced by the presence of the proteins; however, the solubility decreased in
the presence of a small amount of water along with the protein. The activity of the subtilisin slightly decreased when only
placed in scCO2, whereas a marked decrease in the activity was observed for the subtilisin in the presence of the copolymer in scCO2. The subtilisin activity decreased as the CO2 pressure increased. 相似文献
117.
Koichi Ohno Hiroko Satoh Takeaki Iwamoto Hiroaki Tokoyama Hideo Yamakado 《Journal of computational chemistry》2019,40(1):14-28
The existence of a new carbon allotrope family with four-membered rings as a key unit has been recently predicted with quantum chemical calculations. This family includes carbon allotropes in prism-, polymerized prism-, sheet-, tube-, and wavy-forms. An atypical bond property has been observed in this series of carbon structures, which differs from the typical sp3, sp2, and sp hybridizations. The lowest energy barrier from some of the equilibrium states of the carbon structures has been determined with the SHS-ADDF (s caled-h ypersphere-s earch combined with the a nharmonic d ownward d istortion f ollowing) method within the GRRM software program package. The height of the barriers indicates that the well is deep enough for the carbon structures to exist. This class of carbon allotropes is expected to be energy-reservoirs with extra energy of 100–350 kJ mol−1 per one carbon atom. This article presents the structures, energies and reactivity of the carbon allotropes with four-membered ring structures as well as the background of the findings in the context of the global exploration of potential energy surfaces. © 2018 Wiley Periodicals, Inc. 相似文献
118.
Dr. José I. Urgel Dr. Marco Di Giovannantonio Guido Gandus Qiang Chen Dr. Xunshan Liu Dr. Hironobu Hayashi Dr. Pascal Ruffieux Prof. Dr. Silvio Decurtins Dr. Akimitsu Narita Dr. Daniele Passerone Prof. Dr. Hiroko Yamada Shi-Xia Liu Prof. Dr. Klaus Müllen Dr. Carlo A. Pignedoli Prof. Dr. Roman Fasel 《Chemphyschem》2019,20(18):2360-2366
On-surface synthesis is a unique tool for growing low-dimensional carbon nanomaterials with precise structural control down to the atomic level. This novel approach relies on carefully designed precursor molecules, which are deposited on suitable substrates and activated to ultimately form the desired nanostructures. One of the most applied reactions to covalently interlink molecular precursors is dehalogenative aryl-aryl coupling. Despite the versatility of this approach, many unsuccessful attempts are also known, most of them associated to the poor capability of the activated precursors to couple to each other. Such failure is often related to the steric hindrance between reactants, which may arise due to their coplanarity upon adsorption on a surface. Here, we propose a copolymerization approach to overcome the limitations that prevent intermolecular homocoupling. We apply the strategy of using suitable linkers as additional reactants to the formation of fully conjugated polycyclic nanowires incorporating non-benzenoid rings. 相似文献
119.
120.