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101.
Exploration of novel organic luminophores that exhibit thermally activated delayed fluorescence (TADF) in the aggregated state is very crucial for advance of delayed luminescence-based applications such as time-gated bio-sensing and temperature sensing. We report herein that synthesis, photophysical properties, molecular and crystal structures, and theoretical calculations of 2,6-bis (diarylamino)benzophenones. Absorption spectra in solution and calculations using density functional theory (DFT) method revealed that the optical excitation took place through intramolecular charge-transfer from one diarylamino moiety to an aroyl group. While the benzophenones did not luminesce in solution, the solids of the benzophenones emitted green light with moderate-to-good quantum yields. Thus, the benzophenones exhibit aggregation-induced emission. Based on the lifetime measurement, the green emission of the solids was found to include TADF. The emergence of the TADF is supported by the small energy gap between the excited singlet and triplet states, which was estimated by time-dependent DFT calculations. Thin films of poly(methyl methacrylate) doped by the benzophenones also showed green prompt and delayed fluorescence whose lifetimes were in the order of microseconds. Linear correlation between logarithm value of TADF lifetime and temperature was observed with the benzophenone in powder, suggesting that the benzophenones can serve as molecular thermometers workable under aqueous conditions. 相似文献
102.
A Quintuple [6]Helicene with a Corannulene Core as a C5‐Symmetric Propeller‐Shaped π‐System 下载免费PDF全文
Kenta Kato Prof. Dr. Yasutomo Segawa Prof. Dr. Lawrence T. Scott Prof. Dr. Kenichiro Itami 《Angewandte Chemie (International ed. in English)》2018,57(5):1337-1341
The synthesis and structural analysis of a quintuple [6]helicene with a corannulene core is reported. The compound was synthesized from corannulene in three steps including a five‐fold intramolecular direct arylation. X‐ray crystallographic analysis revealed a C5‐symmetric propeller‐shaped structure and one‐dimensional alignment in the solid state. The enantiomers of the quintuple [6]helicene were successfully separated by HPLC, and the chirality of the two fractions was identified by CD spectroscopy. A kinetic study yielded a racemization barrier of 34.2 kcal mol?1, which is slightly lower than that of pristine [6]helicene. DFT calculations indicate a rapid bowl‐to‐bowl inversion of the corannulene moiety and a step‐by‐step chiral inversion pathway for the five [6]helicene moieties. 相似文献
103.
Oligomeric Alkoxysilanes with Cagelike Hybrids as Cores: Designed Precursors of Nanohybrid Materials
Hideki Kuge Yoshiaki Hagiwara Atsushi Shimojima Dr. Kazuyuki Kuroda Prof. 《化学:亚洲杂志》2008,3(3):600-606
Well‐defined alkoxysilane oligomers containing a cagelike carbosiloxane core were synthesized and used as novel building blocks for the formation of siloxane‐based hybrid networks. These oligomers were synthesized from the cagelike trimer derived from bis(triethoxysilyl)methane by silylation with mono‐, di‐, and triethoxychlorosilanes ((EtO)nMe3?nSiCl, n=1, 2, and 3). Hybrid xerogels were prepared by hydrolysis and polycondensation of these oligomers under acidic conditions. The structures of the products varied depending on the number of alkoxy groups (n). When n=2 and 3, microporous xerogels (BET surface areas of 820 and 510 m2 g?1, respectively) were obtained, whereas a nonporous xerogel was obtained when n=1. 29Si NMR spectroscopic analysis suggested that partial rearrangement of the siloxane networks, which accompanied the cleavage of the Si–O–Si linkages, occurred during the polycondensation processes. By using an amphiphilic triblock copolymer surfactant as a structure‐directing agent, hybrid thin films with a 2D hexagonal mesostructure were obtained when n=2 and 3. These results provide important insight into the rational synthesis of molecularly designed hybrid materials by sol–gel chemistry. 相似文献
104.
Fujii K Soejima Y Kyoshoin Y Fukuda S Kanzaki R Umebayashi Y Yamaguchi T Ishiguro S Takamuku T 《The journal of physical chemistry. B》2008,112(14):4329-4336
The liquid structure of 1-ethyl-3-methylimidazolium bis-(trifluoromethanesulfonyl) imide (EMI(+)TFSI(-)) has been studied by means of large-angle X-ray scattering (LAXS), (1)H, (13)C, and (19)F NMR, and molecular dynamics (MD) simulations. LAXS measurements show that the ionic liquid is highly structured with intermolecular interactions at around 6, 9, and 15 A. The intermolecular interactions at around 6, 9, and 15 A are ascribed, on the basis of the MD simulation, to the nearest neighbor EMI(+)...TFSI(-) interaction, the EMI(+)...EMI(+) and TFSI(-)...TFSI(-) interactions, and the second neighbor EMI+...TFSI(-) interaction, respectively. The ionic liquid involves two conformers, C(1) (cis) and C(2) (trans), for TFSI(-), and two conformers, planar cis and nonplanar staggered, for EMI(+), and thus the system involves four types of the EMI(+)...TFSI(-) interactions in the liquid state by taking into account the conformers. However, the EMI(+)...TFSI(-) interaction is not largely different for all combinations of the conformers. The same applies alsoto the EMI(+)...EMI(+) and TFSI(-)...TFSI(-) interactions. It is suggested from the 13C NMR that the imidazolium C(2) proton of EMI(+) strongly interacts with the O atom of the -SO(2)(CF(3)) group of TFSI(-). The interaction is not ascribed to hydrogen-bonding, according to the MD simulation. It is shown that the liquid structure is significantly different from the layered crystal structure that involves only the nonplanar staggered EMI(+) and C(1) TFSI(-) conformers. 相似文献
105.
The concise enantioselective total synthesis of C(2)-asymmetrical (-)-deoxocuscohygrine and (-)-dihydrocuscohygrine are described. Double-diastereoselective additions of normal Grignard reagent to bis(1,3-oxazolidine) have been deployed to construct chiral diamine fragments as a key step. 相似文献
106.
Takechi H Adachi K Monjushiro H Watarai H 《Langmuir : the ACS journal of surfaces and colloids》2008,24(9):4722-4728
The apparent circular dichroism (CD) and the linear dichroism (LD) spectra of the aggregates of achiral zinc(II)-5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine (ZnTPyP), formed at the toluene/water interface in a centrifugal liquid membrane (CLM) cell, were investigated by comparison with the microscopic CD and LD spectra of a single interfacial aggregate of ZnTPyP about 100 mum in length, measured by a microscope-spectropolarimeter. The interfacial ZnTPyP aggregate showed two types of flat trapezoidal shapes, one had a seedlike core at an edge (type I) and another a needlelike core at an edge (type II). The microscopic CD and LD spectra were observed by varying the angle between the parallel axis of the trapezoidal aggregate and the perpendicular axis of a polarized light for LD. The plot of the CD intensity against the LD intensity for a single aggregate, observed at a given wavelength, showed a rotated elliptical shape with a long axis through the origin, when the orientation angle was changed. From these results, it was concluded that the apparent CD spectra observed by the CLM-CD method were mainly due to the large linear dichroism of the aggregate. Both type I and type II structures showed two transition dipole moments, parallel and perpendicular to the long axis of the structure, but suggesting a more developed J-aggregate in type II structure. AFM measurements showed that the interfacial ZnTPyP aggregate had a multilayer structure, in which the unit monolayer thickness was 1.58 +/- 0.23 nm. Finally, the orientation angle of the interfacial aggregate in the CLM cell was estimated as 41 degrees -44 degrees to the rotating axis of the cell. 相似文献
107.
Preparation and mechanical properties of bacterial cellulose nanocomposites loaded with silica nanoparticles 总被引:3,自引:0,他引:3
Shoichiro Yano Hideaki Maeda Megumi Nakajima Toshiki Hagiwara Takashi Sawaguchi 《Cellulose (London, England)》2008,15(1):111-120
Bacterial cellulose (BC), which is produced by Gluconacetobacter xylinus (Ga. xylinus) in culture, is made up of a three-dimensional network of ribbon-shaped bundles of cellulose microfibrils. In the current
studies, we used two processes to prepare nanocomposites of BC filled with silica particles. In Process I, Ga. xylinus was incubated in medium containing silica sol Snowtex 0 (ST 0, pH 2–4) or Snowtex 20 (ST 20, pH 9.5–10.0). The elastic modulus
at 20 °C was improved by keeping the amount of silica in the nanocomposites below 4% when ST 20 was used and below 8.7% when
ST 0 was used. This process allowed incorporation of 50% silica in BC. Inclusion of higher amounts of silica reduced the modulus
at 20 °C and the strength of the nanocomposites below that of BC. X-ray diffraction measurements revealed that the silica
particles disturb the formation of ribbon-shaped fibrils and affect the preferential orientation of the (
) plane. We also produced BC-silica nanocomposites by Process II, wherein the BC hydrogel was immersed in different concentrations
of silica sols, allowing silica particles to diffuse into the BC hydrogel and lodge in the spaces between the ribbon-shaped
fibrils. This method increased the modulus at 20°C and the strength compared to the BC matrix, but it was difficult to load
the BC with more than 10% silica in this way. 相似文献
108.
Kohara S Takata M Matsumoto K Hagiwara R Suzuya K Morita H Siewenie JE Benmore CJ 《The Journal of chemical physics》2008,129(1):014512
The structure of liquid Cs(FH)(2.3)F was revealed using a combination of high-energy x-ray and neutron diffraction measurements. We found that the strongest intermolecular H-F hydrogen bonds at an average distance of 1.36 A are accompanied by the formation of a high degree of bending of the oligomer chain in the melt, with [angle]FHF=150 degrees . A reverse Monte Carlo simulation showed that the average number of atoms per chain is 4.4. A detailed chain analysis of the atomic configuration revealed that (FH)(2)F(-) oligomer chains are the major entities in the liquid, and asymmetrical FHF(-) are formed owing to the strong H-F hydrogen bonds. The results suggest that an average of one or two HF molecules bond to each of the 11 fluorine atoms surrounding a cesium ion. 相似文献
109.
Shoma Mizutani Kenta Komori Tohru Taniguchi Kenji Monde Kouji Kuramochi Kazunori Tsubaki 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2016,128(33):9705-9708
A biomimetic synthesis of naturally occurring lactams rubrobramide, flavipucine, and isoflavipucine is described. The key step is a regioselective Darzens reaction between isobutyl glyoxal and an α‐bromo‐β‐ketoamide. The construction of the core tricyclic ring system of rubrobramide was achieved by a cascade reaction in a single step from an α,β‐epoxy‐γ‐lactam. Furthermore, the absolute configuration of naturally occurring (+)‐rubrobramide was determined by vibrational circular dichroism. (±)‐Flavipucine and (±)‐isoflavipucine were synthesized from an epoxyimide, which was prepared by reaction of isobutyl glyoxal with a protected α‐bromo‐β‐ketoamide. Deprotection of the epoxyimide and formation of the pyridone ring gave (±)‐flavipucine, which was converted into (±)‐isoflavipucine by thermal isomerization. 相似文献
110.
The trityl group is an important and useful protecting group for primary hydroxy groups on carbohydrates. However, during deprotection, neighboring acetyl groups can easily migrate to the deprotected hydroxy groups. Hence, deprotection of trityl groups was optimized using a microreactor with regard to flow rate, reagent concentration, reaction time, and substrate concentration. The optimized microflow reaction conditions inhibited migration and could be applied to large-scale reactions and other substrates. 相似文献