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1.
Marek Mac Tomasz Uchacz Tomasz Wróbel Andrzej Danel Ewa Kulig 《Journal of fluorescence》2010,20(2):525-532
Novel fluorescing dyes 1,3,4-triphenyl-6-(1,4,7,10-tetraoxa-13-aza-cyclopentadec-13-ylmethyl)-1H-pyrazolo[3,4-b]quinoline (K1) and 2-[(2-hydroxyethyl)-(1,3,4-triphenyl-1H-pyrazolo[3,4-b]quinolin-6-ylmethyl)-amino]ethanol (L1) have been synthesized and investigated by the means of steady state and time-resolved fluorescence techniques. These compounds
act as sensors for the fluorescence detection of small inorganic cations (lithium, sodium, barium, magnesium and calcium)
in solvents of different polarities (THF and acetonitrile). The mechanism, which allows application of these compounds as
sensors, is an electron transfer from the electro-donative part of molecule to the acceptor part (fluorophore), which is retarded
upon complexation of the electro-donative part by inorganic cations. We found that crown ether-containing compound is very
sensitive to the addition of any investigated ions but amino alcohol-containing one exhibits better selectivity to the addition
of two-valued cations. Two kinds of the complexes (LM+ and L2M+) were found in the investigated systems. In addition, the dyes may be used as fluorescence indicators in solvents of lower
polarity like tetrahydrofuran. 相似文献
2.
Reaction of amidrazones 1a–1i with (1,5-dihydro-3-methyl-5-oxo-1-phenyl-4H-pyrazol-4-ylidene)propanedinitrile (2) in ethyl acetate solution in one-step reaction led to the formation of unprecedented pyrazolo[4,3-c][1,2,4]triazino[4,5-a]quinolin-4(5H)-ones 3a–3g along with pyrazolo[4,3-c][1,2,4]triazino[4,5-a]quinolin-12b-oles 3h–3m in moderate to excellent yields. These novel heterocycles were formed via a Michael addition reaction followed by intramolecular cyclization via a dearomatization process. 相似文献
3.
Karen Aknin Stéphanie Desbène-Finck Philippe Helissey Sylviane Giorgi-Renault 《Molecular diversity》2010,14(1):123-130
Functionalized pyrimido[4,5-b]quinoline-2,4 (1H,3H)-diones were synthesized by a three-component one-pot reaction involving barbituric acid, aldehydes, and anilines. The use
of commercially available anilines allowed the facile syntheses of pyrimido[4,5-b]quinolinediones substituted in all the positions on the benzene ring with electron donor or electron withdrawing groups.
This straightforward method circumvents the preparation of unstable substituted 2-aminobenzaldehydes that limits the scope
of previously described syntheses. Furthermore, access to the 5-substituted derivatives is now also possible starting from
aliphatic or aromatic aldehydes. Our strategy and methodology offer significant and practical improvements over other methodologies. 相似文献
4.
Alkali metal dodecahydro-closo-dodecaborates M2[B12H12] (M = K, Rb, Cs, NH4, N(CH3)4) and the perhalogenated cesium salts Cs2[B12X12] (X = Cl, Br, I) are studied by solid-state 11B nuclear magnetic resonance (NMR) spectroscopy as well as X-ray diffraction (XRD) and differential scanning calorimetry.
The present work addresses the molecular dynamics of the anionic [B12X12]2− icosahedra which is examined by variable-temperature 11B NMR line shape studies between 120 and 370 K. Characteristic line shape effects are observed which strongly depend on the
actual substituent X and the counterion M+. All alkali metal dodecahydro-closo-dodecaborates M2 [B12H12] exhibit at elevated temperatures 11B NMR spectra with a single isotropic line which proves the presence of an efficient molecular process, resulting in dynamic
(rotational) disorder along with vanishing dipolar and quadrupolar interactions. The positional order of the boron clusters,
however, remains unaffected, as shown by the XRD data. At lower temperatures, the underlying motions are frozen on the NMR
timescale resulting in characteristic 11B NMR spectra with a dominant homonuclear 11B–11B dipolar splitting. The per-halogenated cesium salts Cs2[B12X12] behave differently. Hence, from the experimental 11B NMR spectra at room temperature a substantial mobility is only seen for the [B12Cl12]2− anion. Obviously, the degree of anion mobility depends on the size of the substituent X in the [B12X12]2− clusters (X = H, Cl, Br, I). A quantitative analysis of the experimental 11B NMR spectra of the alkali metal dodecahydro-closo-dodecaborates M2 [B12H12] is achieved by line shape simulations, considering [B12H12]2− ions undergoing reorientational jumps between icosahedral sites. From the motional correlation times the activation energies
are derived. It is found that a correlation exists between the activation energies, the motional correlation times and the
lattice constant. Hence, the activation energies and correlation times strongly increase with decreasing size of the cation
M+, which reflects an increasing sterical hindrance due to a decreasing crystallo-graphic lattice constant in the same direction.
Authors' address: Klaus Müller, Institut für Physikalische Chemie, Universit?t Stuttgart, Pfaffen-waldring 55, Stuttgart 70569,
Germany 相似文献
5.
A practical strategy was developed for the preparation of highly substituted 2,3-dihydropyrimido[4,5-d]pyrimidin-4(1H)-ones from 4,6-dichloro-5-formylpyrimidine, primary amines, and aldehydes. The key step for this synthesis entails a cyclization
reaction involving an intramolecular amide addition to an iminium intermediate formed in situ from 4-amino-pyrimidine-5-carboxamide
2 and aldehydes to form the pyrimido[4,5-d]pyrimidine core with a strategically placed 5-Cl group for further derivatization. The utility of this methodology was demonstrated
through the preparation of a 27-membered library of representative 2,3-dihydropyrimido[4,5-d]pyrimidin-4(1H)-ones in moderate to good yields. 相似文献
6.
Martínez-Palou R Zepeda LG Höpfl H Montoya A Guzmán-Lucero DJ Guzmán J 《Molecular diversity》2005,9(4):361-369
Summary A versatile route to 40-membered library of 2-long alkyl chain substituted benzoazoles (1 and 2) and azole[4,5-b]pyridines (3 and 4) via microwave-assisted combinatorial synthesis was developed. The reactions were carried out in both monomode and multimode microwave
oven. With the latter, all reactions were performed in high-throughput experimental settings consisting of an 8×5 combinatorial
library designed to synthesize 40 compounds. Each step, from the addition of reagents to the recovery of final products, was
automated. The microwave-assisted N-long chain alkylation reactions of 2-alkyl-1H-benzimidazole (1) and 2-alkyl-1H-benzimidazole[4,5-b] pyridines (3) were also studied. 相似文献
7.
Abstract
An efficient microwave-assisted one-pot two-step protocol was developed for the construction of disubstituted 2-amino-1H-imidazoles. This process involves the sequential formation of 2,3-dihydro-2-hydroxyimidazo[1,2-a]pyrimidinium salts from readily available 2-aminopyrimidines and α-bromoketones, followed by cleavage of the pyrimidine ring with hydrazine. 相似文献8.
H.-Y. Cheng 《The European Physical Journal C - Particles and Fields》2003,26(4):551-565
Based on SU(3) flavor symmetry, many of the quark-graph amplitudes in two-body non-leptonic decays of charmed mesons can
be extracted from experiment, which enable us to see the relevance and importance of weak annihilation topologies and to determine
the complex parameters a1 and a2 to test the factorization approach. It is found that a
2
/a
1
in and can be different by a factor of 2, indicating that non-factorizable corrections to the latter are far more important than
the former. The relative phase between a1 and a2 is about 150°. Weak annihilation topologies induced by nearby resonances via final-state rescattering can be described in
a model-independent manner. Although the W-exchange contribution in decays is dominated by resonant final-state interactions (FSIs), its amplitude in VP decays (V: vector meson, P: pseudoscalar meson) receives little contributions from FSIs in the quark-antiquark resonance formation. As a consequence,
the sign flip of the W-exchange amplitude in and decays, which is needed to explain the relatively real decay amplitudes of , remains unexplained. SU(3) symmetry is badly broken in some Cabibbo-suppressed modes and this can be accounted for by the
accumulation of some modest SU(3) violation in individual quark-graph amplitudes.
Received: 19 July 2002 / Published online: 20 November 2002 相似文献
9.
We show that for every set of discrete polynomials y
n
(x(s)) on the lattice x(s), defined on a finite interval (a, b), it is possible to construct two sets of dual polynomials z
k
(ξ(t)) of degrees k = s-a and k = b-s-1. Here we do this for the classical and alternative Hahn and Racah polynomials as well as for their q-analogs. Also we establish the connection between classical and alternative families. This allows us to obtain new expressions
for the Clerbsch-Gordan and Racah coefficients of the quantum algebra U
q
(su(2)) in terms of various Hahn and Racah q-polynomials.
Dedicated to the memory of our teacher and friend Arnold F. Nikiforov (18.11.1930–27.12.2005). 相似文献
10.
Ahmad Shaabani Fatemeh Hajishaabanha Hamid Mofakham Ali Maleki 《Molecular diversity》2010,14(1):179-182
In this study, a three-component one-pot synthesis of new 2,4-diamino-5H-chromeno[2,3-b]pyridine-3-carbonitriles derived from 2-amino-1,1,3-tricyanopropene, salicylic aldehydes and secondary cyclic amines is reported.
The reaction is conducted in ethanol at ambient temperature in good-to-excellent yields. 相似文献
11.
New and high regioselective method of the synthesis of 2,7-diaryl-4,7-dihydropyrazolo[1,5-a]pyrimidine-5-carboxylic acids by reaction of 3-aryl-5-aminopyrazoles with arylidenpyruvic acid at room temperature under ultrasonication was developed and discussed. 相似文献
12.
Xinying Zhang Dongfang Li Xuesen Fan Xia Wang Xiaoyan Li Guirong Qu Jianji Wang 《Molecular diversity》2010,14(1):159-167
The utilization of an ionic liquid, [bmim][BF4] as both reaction medium and promoter for a multi-component reaction of aldehyde (1) and 5-amino-3-methyl-1-phenylpyrazole (2) with Meldrum acid (3) or dimedone (5) is studied. From this reaction, pyrazolo[3,4-b]pyridinone (4) and pyrazolo[3,4-b]quinolinone (6) derivatives were prepared in high yields. This novel procedure showed such advantages as environmentally benign nature,
enhanced efficiency, simple operation process, and mild reaction conditions. As an application, the procedure was successfully
used in the preparation of a set of pyrimidine nucleoside–pyrazolo[3,4-b]pyridine and pyrazolo[3,4-b]quinolinone hybrids with potential biological activities. 相似文献
13.
A. C. dos Reis 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):474-478
The issue of Kπ and ππ
S-wave amplitude is addressed using decays of D-mesons. Model-independent measurements of the phases of the π
+
π
+ and K
-
π
+
S-wave amplitude from D
+→π
-
π
+
π
+ and D
+→K
-
π
+
π
+ decays are discussed. The result indicates a deviation from the phase of the K
-
π
+
S-wave amplitude obtained by scattering experiments. This could be interpreted as an indication of the presence of 3-body final-state
interaction, or in other words, that the phases from production and scattering process cannot be directly compared. 相似文献
14.
Low edge safety factor discharges including very low q
a
(1<q
a
<2) and ultra low q
a
(0<q
a
<1) have been obtained in the SINP tokamak. It has been observed that accessibility of these discharges depends crucially
on the fast rate of plasma current rise. Several interesting results in terms of different time scales like T
q
a
· τ
R
etc have been obtained using a set of softwares developed at SINP. From fluctuation analysis of the external magnetic probe
data it has been found that MHD instabilities m=1, n=1 and m=2, n=1 etc. play major role in the evolution of these discharges. To investigate the internal details of these discharges, an
internal magnetic probe system has been developed using which current density j
φ
and other related parameters have been estimated. By carrying out a resistive stability analysis, evidence of the above-mentioned
MHD instabilities have again been found. The physical processes lying behind the accessibility and evolution of the low q
a
discharges have been thoroughly investigated. 相似文献
15.
Ghasem Marandi Malek T. Maghsoodlou Nourallah Hazeri Sayyed M. Habibi-Khorassani Niloufar Akbarzadeh Torbati Faramarz Rostami-Charati Brian W. Skelton Mohamed Makha 《Molecular diversity》2011,15(1):197-201
Abstract
In a new multicomponent reaction phenanthridine reacts with isocyanides and malonitrile in the presence of benzaldehyde derivatives to produce 2-aryl-3-(alkyl- or arylimino)-2,3-dihydropyrrolo[1,2-f]phenanthridine-1,1(12b H)-dicarbonitrile in a simple, mild, and efficient protocol in excellent yields. 相似文献16.
The Pictet–Spengler reaction is known as a useful tool for the synthesis of constrained analogs of tryptophan. Herein, we
present the further cyclization of 1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid methyl esters with 1-(1′-aminoalkyl) side chain. These transformations lead to heterocyclic structures
which can find useful applications in medicinal chemistry as peptide mimetics. 相似文献
17.
An efficient, fast and facile pyrazolo[1,5-a]pyrimidine synthetic protocol has been established by the condensation of aminopyrazoles with 1,3-dicarbonyl components in
AcOH/H2SO4 system. The pyrazolo[1,5-a]pyrimidine sulfides were selectively oxidized to the sulfones via a temperature-controlled stepwise oxidative fashion. The
correlation between the substitution patterns of these pyrazolo[1,5-a]pyrimidines and their fluorescent spectroscopic properties were further examined, which provided the fundamentals for their
potential applications in the development of new fluorescent probes. Red-shifts were easily achieved by the incorporation
of unsaturated groups at the 5- and 7-positions, which suggested an approach for synthesizing long wavelength pyrazolo[1,5-a]pyrimidine dyes. The fluorescent spectroscopic properties were found to be sensitive to the hydroxy-containing and carbonyl-containing
media such as alcohol and acetone, which helps to confirm the promising perspectives of further investigations in this area. 相似文献
18.
A γ-rigid version (with γ = 0) of the X(5) critical point symmetry is constructed. The model, to be called X(3) since it is proved to contain three degrees of freedom, utilizes an infinite well potential, is based on exact separation
of variables, and leads to parameter-free (up to overall scale factors) predictions for spectra and B(E2) transition rates which are in good agreement with existing experimental data for 172Os and 186Pt. An unexpected similarity of the β
1 bands of the X(5) nuclei 150Nd, 152Sm, 154Gd, and 156Dy to the X(3) predictions is observed.
The text was submitted by the authors in English. 相似文献
19.
A. Yu. Loginov 《Physics of Atomic Nuclei》2011,74(5):740-754
The (1 + 1)-dimensional nonlinear O(3) σ model involving an explicitly broken symmetry is considered. Sphalerons are known to exist in this model. These sphalerons
are of a topological origin and are embedded kinks of the sine-Gordon model. In the case of a compact spatial manifold S
1, sine-Gordon multikinks exist in the model. It is shown that the model admits a nonstatic generalization of the sine-Gordon
kink/multikink, Q kink/multikink. Explicit expressions are obtained for the dependence of the Q kink energy and charge on the phase frequency of rotation. The Q kink is studied for stability, and expressions are obtained for the eigenfunctions and eigenfrequencies of the operator of
quadratic fluctuations. It is shown that the Q kink is unstable over the entire admissible frequency range ω ∈ [−1, 1]. The one-loop quantum correction to the static-kink mass is calculated, and the Q-kink zero mode is quantized. It is shown that, in a general static case, the field equations of the model are integrable
in quadratures. 相似文献
20.
Marjan Matvejchuk 《International Journal of Theoretical Physics》2011,50(12):3852-3856
Let B(H)
Id
be the set of all bounded idempotents on a Hilbert space H. Fix p∈B(H)
Id
. The aim of the paper is to show a set of symmetries J on H for which p is a J-projection. 相似文献