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21.
Dibenzo[b,f]arsepins possessing severely distorted cores compared to those of other heteropins were synthesized. These derivatives exhibited dual photoluminescence in the green‐to‐red region (500–700 nm) and the near‐ultraviolet region (<380 nm), which could be attributed to the planarization of the arsepin core in the lowest singlet excited (S1) state. The computational approach for the assessment of the aromatic indices revealed that the dibenzoarsepins studied show aromaticity (8π system) in the S1 states in line with Baird's rule. The lone pair electrons of the arsenic atoms play a crucial role in the aromaticity in the S1 states.  相似文献   
22.
23.
A new chiral probe molecule for mono-alcohols is developed by using 1,2-dihydro-1-hydroxy-2,3,1-benzodiazaborine (DAB) bearing an acridine moiety 1 . In the presence of mono-alcohols, DAB 1 forms borate 2 by boronic ester formation, followed by coordination of the acridine moiety to the boron atom. Borate 2 has a chiral center on the boron atom and works as a stereodynamic circular dichroism (CD) probe molecule for chiral mono-alcohols based on the π–π interaction between the acridine moiety and the carbon–carbon unsaturated moiety on mono-alcohols.  相似文献   
24.
Polychlorinated pyridyldiphenylmethyl radicals having substituents meta to the position bearing the carbon-centered radical (α-carbon) are synthesized. All of them are stable in ambient conditions in solutions and fluorescent in cyclohexane. The fluorescence of the radicals with bromo, phenyl, 4-chlorophenyl, or 2-pyridyl substituents are enhanced in chloroform, while the emission of the radicals with 2-thienyl or 2-furyl substituents are quenched in chloroform. DFT and TD-DFT calculations indicate that the first doublet excited states of the former are locally excited, while the first doublet excited states of the latter are charge transfer states from the π-electron-donating substituent to the accepting radical. The latter also show much higher photostability under 370-nm light irradiation compared with the first reported photostable fluorescent radical, (3,5-dichloro-4-pyridyl)bis(2,4,6-trichlorophenyl)methyl radical (PyBTM), with pronounced bathochromic shifts of the fluorescence.  相似文献   
25.
Trichlorosilyl triflate, in the presence of a chiral Lewis base catalyst, provides an effective method for the enantioselective direct-type aldol reaction of aldehydes and ketones. A chiral Lewis base induces both the production and activation of trichlorosilyl enol ether, yielding an aldol product in good yield and with high diastereo- and enantioselectivities.  相似文献   
26.
The 4f-3d exchange couplings were definitively and precisely determined in the dinuclear complexes (Ln-M) involving double μ-oxo-bridges, by means of combined high-frequency electron paramagnetic resonance and pulsed-field magnetization techniques, revealing a monotonic decrease of ferromagnetic J(Ln-Cu) in the order of the atomic number, (64)Gd to (68)Er.  相似文献   
27.
Chiral lithium binaphtholate effectively catalyzed the enantioselective alkynylation of ketones using lithium acetylide as an alkynylating agent. This is the first example of the catalytic enantioselective addition of lithium acetylide to carbonyl compounds without the aid of other metal sources.  相似文献   
28.
The first catalytic version of hypervalent aryl-λ(3)-iodane-induced Hofmann rearrangement of primary carboxamides, which probably involves in situ generation of a tetracoordinated bis(aqua)(hydroxy)phenyl-λ(3)-iodane complex as an active oxidant from a catalytic amount of iodobenzene by the reaction with m-chloroperbenzoic acid in the presence of HBF(4) in dichloromethane-water under mild conditions, was developed.  相似文献   
29.
The development of technology for on/off switching of enzyme activity is expected to expand the applications of enzyme in a wide range of research fields. We have previously developed a complementary polymer pair system (CPPS) that enables the activity of several enzymes to be controlled by a pair of oppositely charged polymers. However, it failed to control the activity of large and unstable α-amylase because the aggregation of the complex between anionic α-amylase and cationic poly(allylamine) (PAA) induced irreversible denaturation of the enzyme. To address this issue, we herein designed and synthesized a cationic copolymer with a poly(ethylene glycol) backbone, poly(N,N-diethylaminoethyl methacrylate)-block-poly(ethylene glycol) (PEAMA-b-PEG). In contrast to PAA, α-amylase and β-galactosidase were inactivated by PEAMA-b-PEG with the formation of soluble complexes. The enzyme/PEAMA-b-PEG complexes were then successfully recovered from the complex by the addition of anionic poly(acrylic acid) (PAAc). Thus, dispersion of the complex by PEG segment in PEAMA-b-PEG clearly plays a crucial role for regulating the activities of these enzymes, suggesting that PEGylated charged polymer is a new candidate for CPPS for large and unstable enzymes.  相似文献   
30.
Highlights? CPYPP binds to DOCK2 DHR-2 domain and inhibits its catalytic activity ? CPYPP inhibits DOCK2-mediated Rac activation in cells ? The structural features of CPYPP required for its inhibitory effect were revealed ? CPYPP inhibits lymphocyte migration and activation in vitro and in vivo  相似文献   
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