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571.
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573.
Periodic solutions in a simple model, whose solution shows successive period-doubling bifurcations leading to chaotic motion, are calculated by using the harmonic balance method. The result is in good agreement with that of computer simulation. 相似文献
574.
575.
Synthesis,Structure, and Optical Studies of Donor–Acceptor‐Type Near‐Infrared (NIR) Aza–Boron‐Dipyrromethene (BODIPY) Dyes
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Naresh Balsukuri Mohsin Y. Lone Dr. Prakash C. Jha Dr. Shigeki Mori Dr. Iti Gupta 《化学:亚洲杂志》2016,11(10):1572-1587
Six donor–acceptor‐type near‐infrared (NIR) aza–boron‐dipyrromethene (BODIPY) dyes and their corresponding aza–dipyrrins were designed and synthesized. The donor moieties at the 1,7‐positions of the aza–BODIPY core were varied from naphthyl to N‐phenylcarbazole to N‐butylcarbazole. The 3,5‐positions were also substituted with phenyl or thienyl groups in the aza–BODIPYs. Photophysical, electrochemical, and computational studies were carried out. The absorption and emission spectra of aza–BODIPYs were significantly redshifted (≈100 nm) relative to the parent tetraphenylaza–BODIPY. Fluorescence studies suggested effective energy transfer (up to 93 %) from donor groups to the aza–BODIPY core in all of the compounds under study. Time‐dependent (TD)‐DFT studies indicated effective electronic interactions between energy donor groups and aza–dipyrrin unit in all the aza–BODIPYs studied. The HOMO–LUMO gap (ΔE) calculated from cyclic voltammetry data was found to be lower for six aza–BODIPYs relative to their corresponding aza–dipyrrins. 相似文献
576.
Au(III) metalation of hexakis(pentafluorophenyl) [26]hexaphyrin led to formation of aromatic mono-Au(III) hexaphyrin and bis-Au(III) hexaphyrin, in which the inner pyrrolic beta-protons are activated to form gold-carbon bonds, hence accommodating Au(III) ion with a NNCC core in a square planar manner. Two-electron reductions of these complexes with NaBH4 provided the corresponding [28]hexaphyrin complexes which exhibit distinct paratropic ring currents. 相似文献
577.
A method for the determination of seven alkylphenols and bisphenol A by stir bar sorptive extraction (SBSE) with in situ derivatization-thermal desorption (TD)-gas chromatography (GC)-mass spectrometry (MS) is described. SBSE was performed with in situ acetylation and without derivatization for comparison. For 4-tert-butylphenol and bisphenol A, in situ acetylation improved the responses in SBSE-TD-GC-MS. The method detection limits ranged from 0.1 to 3.2 ng/l. The recoveries of the analytes from a river water sample spiked with standards at 10 and 100 ng/l were 85.3-105.9% (R.S.D., 3.0-11.0%) and 88.3-105.8% (R.S.D., 1.6-8.3%), respectively. 相似文献
578.
Kizashi Yamaguchi Satoshi Yabushita Takayuki Fueno Shigeki Kato Keiji Morokuma 《Chemical physics letters》1980,70(1):27-30
Geometry optimizations of several low-lying diradical states of the ring-opened oxirane (·CH2CH2O·) were performed by using the energy gradients of the UHF MINDO/3, STO-3G and 4-31G solutions. Both the STO-3G and 4-3 IG methods predict that the most stable form is the triplet state of the non-twisted σπ conformation in which the unpaired spins localized on the terminal carbon and oxygen atoms are oriented perpendicularly to each other. The singlet σσ diradical state in which both the radical-site p orbitals are coplanar with the molecular framework is only 2.3 (STO-3G) and 1.2 (4-31G) kcal/mol less stable than the triplet σπ diradical state. It is found that the geometry of the singlet σσ diradical is unique in that the C-C-O angle is noticeably small as compared with various other diradical states. Implications of these results to the mechanism of the oxirane-forming O(3P) + C2H4 reaction are discussed. 相似文献
579.
Tokuyasu T Kunikawa S McCullough KJ Masuyama A Nojima M 《The Journal of organic chemistry》2005,70(1):251-260
In the competitive peroxidation of mixtures of two alkenes with Co(II)/O(2)/Et(3)SiH, it was found that the relative reactivities of the alkene substrates are influenced by three major factors:. (1) relative stability of the intermediate carbon-centered radical formed by the reaction of the alkene with HCo(III) complex, (2) steric effects around the C=C double bond, and (3) electronic factors associated with the C=C double bond. Consistent with results from simple alkenes, the chemo- and regioselective peroxidation of dienes was also realized. Depending on the diene structure, the product included not only the expected acyclic unsaturated triethylsilyl peroxides but also 1,2-dioxolane and 1,2-dioxane derivatives via intramolecular cyclization of the unsaturated peroxy radical intermediates. 相似文献
580.
Matsunaga S Kumagai N Harada S Shibasaki M 《Journal of the American Chemical Society》2003,125(16):4712-4713
An anti-selective direct catalytic asymmetric Mannich-type reaction is described. The Et(2)Zn/(S,S)-linked-BINOL 1 = 4/1 complex promoted a Mannich-type reaction of 2-hydroxy-2'-methoxyacetophenone (2) and N-diphenylphosphinoyl imines 3. Using as little as 0.25-1 mol % of the catalyst, we obtained Mannich adducts 4 in excellent yield (up to 99%), diastereoselectivity (anti/syn = up to >98/2), and enantiomeric excess (up to >99.5%). The anti-selectivity in the present system is complementary to that observed using previously reported methods, providing a novel efficient method to synthesize anti-beta-amino alcohols in a highly enantioselective manner. Facile deprotection of the N-diphenylphosphinoyl group and commercial availability of both Et(2)Zn solution and (S,S)-linked-BINOL 1 also make the present catalysis practical. 相似文献