共查询到20条相似文献,搜索用时 31 毫秒
1.
Wenjian Lao Xuejun Sun Jinmao You Qingyu Ou 《Monatshefte für Chemie / Chemical Monthly》2000,16(2):803-811
A rapid one-pot synthesis of substituted carbazole-9-acetic and -propionic acids under microwave irradiation is described.
N-Alkylation and hydrolysis was carried out in DMF without catalyst. The absorption and fluorescence spectroscopic characteristics of the title compounds are discussed. 相似文献
2.
Excitonic Bands in the Spectra of Some Organic-Inorganic Hybrid Compounds Based on Metal Halide Units 总被引:1,自引:0,他引:1
George C. Papavassiliou George A. Mousdis Ioannis B. Koutselas 《Monatshefte für Chemie / Chemical Monthly》2001,132(1):113-119
Summary. The optical absorption, photoluminescence, and photoconductivity spectra of some compounds of the formulas [R(CH2)
n
NH3]
x
M
y
X
z
, [R(CH2)
n
NH(CH3)2]
x
M
y
X
z
, [R(CH2)
n
S(CH3)2]
x
M
y
X
z
, [R(CH2)
n
SC(NH2)2]
x
M
y
X
z
, and [R(CH2)
n
SeC(NH2)2]
x
M
y
X
z
(R = organic residue; M = Bi(III), Pb(II), Sn(II), Cu(I), Ag(I) etc; X = I, Br, Cl; n, x, y, z = 0, 1, 2, 3, …) are briefly reviewed, and some new results are reported. The position, intensity, and shape of the excitonic
bands depend on the dimensionality and size of the inorganic network as well as on the nature of the M, X, R, and onium moieties.
Received June 23, 2000. Accepted August 1, 2000 相似文献
3.
Hans Bettermann Lars Ulrich Gabriele Domnick Hans-Dieter Martin 《Angewandte Chemie (International ed. in English)》1999,38(17):2573-2576
Owing to the low quantum yield of phosphorescence , triplet states of carotenoids have been very difficult to identify. These states can be characterized by intracavity absorption spectroscopy, which allows the direct measurement of the spin-forbidden singlet–triplet transitions in low concentrated solutions, and by delayed fluorescence measurements. 相似文献
4.
Summary. Vanadophosphoric acid in acidic medium is proposed as a modified reagent for the spectrophotometric determination of cephalexin,
cephaprine sodium, cefazolin sodium, and cefotaxime in pure samples and in pharmaceutical preparations. The method is based
on acid hydrolysis of cephalosporins and subsequent oxidation with vanadophosphoric acid. The resulting solution exhibits
maximum absorption at about 516 nm. The effects of reaction conditions were investigated. Lambert-Beer’s law was obeyed over a concentration range of about 0.4–45 μg · cm−3. For more accurate results, Ringbom optimum concentration ranges were obtained, and the molar absorptivities and Sandell sensitivities were derived. The proposed method was applied to the determination of the drugs in pharmaceutical formulations;
the results demonstrated that the proposed method is as accurate, pecise, and reproducible as the official methods.
Received August 13, 1999. Accepted (revised) December 7, 1999 相似文献
5.
Sergey A. Filonovich Yurii P. Rakovich Mikhail I. Vasilevskiy Mikhail V. Artemyev Dmitrii V. Talapin Andrey L. Rogach Anabela G. Rolo Maria J. M. Gomes 《Monatshefte für Chemie / Chemical Monthly》2002,133(6):909-918
Summary. We present the results of a comparative analysis of the absorption and photoluminescence excitation (PLE) spectra vs. integrated photoluminescence (IPL) measured as a function of the excitation wavelength for a number of samples containing
II–VI semiconductor nanocrystals (NCs) produced by different techniques. The structure of the absorption and PL spectra due
to excitons confined in NCs and difficulties with the correct interpretation of the transmittance and PLE results are discussed.
It is shown that, compared to the conventional PLE, the IPL intensity plotted against the excitation wavelength (IPLE spectra)
reproduce better the structure of the absorption spectra. Therefore, IPLE spectroscopy can be successfully used for probing
the quantized electron-hole (e-h) transitions in semiconductor nanocrystals.
Received October 16, 2001. Accepted (revised) January 7, 2002 相似文献
6.
Vesna Kuntić Dusěan Malesěev Zorica Radović Vladana Vukojević 《Monatshefte für Chemie / Chemical Monthly》2000,131(7):769-777
Summary. In the present work, rutin (3,3′ ,4′ ,5,7-pentahydrohyflavone-3-rhamnoglucoside) was determinated via a complexing reaction with a titanyloxalate anion. K2[TiO(C2O4)2] and rutin react in 50% ethanol forming a 1:2 complex in a pH range from 4.00 to 11.50, in which the TiO(C2O4)2
2− ion is linked to rutin through the 4-carbonyl and 5-hydroxyl group. The thermodynamic stability constant log β2
0 of the complex is determined to 10.80 at pH = 6.50. The change of the standard Gibbs free energy Δ G0 amounts to −61 kJċ mol−1, indicating that the process of complex formation is spontaneous. The optimal conditions for the spectrophotometric determination
of microconcentrations of rutin are at pH=6.40 and λ= 430 nm, where the complex shows an absorption maximum with a molar absorption coefficient a
430=(60±2)ċ103 dm3ċ mol−1ċ cm−1. The method is applied rutin determination from tablets.
Received January 4, 2000. Accepted (revised) February 17, 2000 相似文献
7.
8.
Ryuhei Nakamura Dr. Kazuyuki Ishii Prof. Dr. Kazuhito Hashimoto Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(9):1606-1608
Shewanella is an electrogenic microbe that has significant content of c type cytochromes (ca. 0.5 mM ). This feature allows the optical absorption spectra of the cell‐membrane‐associated proteins to be monitored in vivo in the course of extracellular respiratory electron‐transfer reactions. The results show significant differences to those obtained in vitro with purified proteins.
9.
Summary. A new group of 6- and 7-substituted compounds of 4-amino-2-phenylquinazoline were synthesized by reaction of N-arylbenzimidoyl
chlorides with cyanamide in the presence of TiCl4. The products were identified by spectroscopic methods, their dissociation constants were determined and are discussed.
Received February 14, 2000. Accepted February 26, 2000 相似文献
10.
Maurice O. Iwunze 《Monatshefte für Chemie / Chemical Monthly》2000,131(5):429-435
Summary. Berberine hydrochloride is an alkaloid with little or no fluorescence in water. In sodium dodecylsulfate solutions, the fluorescence
intensity of this compound is enhanced several folds by ion-pairing with the anion of the surfactant. The enhanced fluorescence
intensity reaches a maximum at a surfactant concentration of 4·10−3 M and then decreases to a constant value at the critical micelle concentration and beyond. At concentrations near the maximum,
a calibration sensitivity of 3.23·106/M was obtained. In addition, a good linear dynamic range and a low limit of detection (4·10−5 and 1.5·10−7 M, respectively) were determined. This observation indicates that this surfactant medium could be effectively used in fluorometric
trace analysis of berberine hydrochloride. It was also observed in this work that solvents of low dielectric constant tend
to stabilize this compound and thereby enhance its fluorescence.
Received November 26, 1999. Accepted (revised) January 13, 2000 相似文献
11.
Yvonne Zimmermann Mohamed El-Sayed Silvio Prause Stefan Spange 《Monatshefte für Chemie / Chemical Monthly》2001,132(11):1347-1361
Summary. Kamlet-Taft’s α (hydrogen bond donor acidity) and π* (dipolarity/polarizability) values of various silica batches measured in various solvents are presented. The α and π* parameters for the various solid acids are analyzed by means of Fe(phen)2(CN)2 (cis-dicyano-bis-(1,10)-phenanthroline-iron(II), 1), Michler’s ketone (4,4′-bis-(dimethylamino)-benzophenone, 2), and two hydrophilic derivatives of 2, (4-(dimethylamino)-4′-(di-2-hydroxyethyl)-amino-benzophenone (3a) and 4,4′-bis-(di-(2-hydroxyethyl)-amino)-benzophenone (3b) as well as coumarin 153 (4) as solvatochromic surface polarity indicators. Apparent β (hydrogen bond acceptor basicity) parameters for bare silica have
been evaluated by means of an aminobenzodifuranone dye (5) as solvatochromic probe.
The chemical interpretation of the α and π* parameters and the nature of the solvent/surface interaction which they reflect are discussed. It can be shown that an increase
of the HBA (hydrogen bond accepting) capacity of the solvent significantly decreases the HBD (hydrogen bond donating) capacity
of the surface environment, whereas the dipolarity/polarizability value of the silica/solvent interface is a composite of
many effects. The classification of the polarity of silica particles in organic solvents compared to pure liquids is outlined.
Theoretical E
T(30) values of the solid/solvent interfaces are calculated by applying linear solvation energy (LSE) relationships using the
independently measured α and π* values of the solid acids according to
Received February 2, 2001. Accepted (revised) March 3, 2001 相似文献
12.
Haixiao Qiu Chengyun Wang Jinfeng Xu Guoqiao Lai Yongjia Shen 《Monatshefte für Chemie / Chemical Monthly》2008,139(11):1357-1362
Three donor–acceptor dyads 1–3 comprising of a tetrathiafulvalene (TTF) unit linked with perylene by a simple σ-bond were synthesized and characterized. Spectroscopy and cyclic voltammetry provided
an indication that intramolecular charge-transfer interactions in their ground states between TTF and perylene for dyads 1–3 are negligible. Compared with the compound perylene, dyads 1–3 exhibited large fluorescence quenching, which might be ascribed to photo-induced electron transfer interaction between TTF and perylene units in the excited state.
Correspondence: Yongjia Shen, Laboratory of Advanced Materials, Institute of Fine Chemicals, East China University of Science
and Technology, Shanghai 200237, P.R. China. 相似文献
13.
Babasaheb P. Bandgar Vaibhav S. Sadavarte Lav S. Uppalla Rahul Govande 《Monatshefte für Chemie / Chemical Monthly》2001,132(3):403-406
Summary. A simple and versatile method for the synthesis of oximes, semicarbazones, and tosylhydrazones of aldehydes in the presence
of ketones without catalyst and solvent is presented.
Received June 28, 2000. Accepted (revised) August 25, 2000 相似文献
14.
Kristina Starčević Marijana Hranjec Dejana Carić Grace Karminski-Zamola 《Monatshefte für Chemie / Chemical Monthly》2008,139(8):975-983
A series of novel substituted derivatives related to furyl-phenyl-acrylates and naphthofurans, was synthesized and characterized
by UV/Vis and fluorescence spectroscopy. Acyclic compounds can undergo photochemical dehydrocyclization by visible light irradiation
in order to obtain their cyclic derivatives. The interactions of the prepared compounds with calf thymus DNA was investigated by means of electronic absorption and fluorescence spectra. It is intriguing that addition of ct-DNA induced a fluorescence increase of acyclic derivatives, exactly the opposite of the strong fluorescence quenching observed
for cyclic derivatives 10 and 12. Compound 11 showed decreasing fluorescence intensity for lower concentrations of ct-DNA, while increasing of fluorescence is observed for high excess of added ct-DNA.
Correspondence: Grace Karminski-Zamola, Department of Organic Chemistry, Faculty of Chemical Engineering and Technology, University
of Zagreb, Marulićev trg 20, HR-10000 Zagreb, Croatia. 相似文献
15.
Klaus Burger Elisabeth Windeisen Elisabeth Heistracher Torsten Lange Abdel-Aleem H. Abdel-Aleem 《Monatshefte für Chemie / Chemical Monthly》2002,133(1):41-58
Summary. The synthesis of homochiral heterocyclic α-hydroxy acids starting from (S)- and (R)-malic acid using hexafluoroacetone as protecting and activating agent is described. The new compounds are useful building
blocks for peptide and depsipeptide modification.
Received May 21, 2001. Accepted (revised) July 6, 2001 相似文献
16.
Summary. A new synthesis of α-N-ethylamino acids starting from α-amino acids using hexafluoroacetone as protecting and activating
agent is described. The hexafluoroacetone-protected N-ethylamino acid derivatives obtained are activated lactons. Therefore,
they can be directly transformed without the need of an additional activation step with various nucleophiles into the corresponding
carboxylic acid derivatives.
Received March 24, 2000. Accepted (revised) April 20, 2000 相似文献
17.
Andrei Blasko Alana Leahy-Dios William O. Nelson Steven A. Austin Robert B. Killion Gary C. Visor Ian J. Massey 《Monatshefte für Chemie / Chemical Monthly》2001,132(7):789-798
Summary. The kinetic and thermodynamic solubilities of Roche (Ro) pharmaceutical compounds were determined by HPLC, titrimetry, and UV/Vis spectroscopy in aqueous buffers and in non-buffered
systems. For kinetic solubility, a turbidimetric method that allows the rapid determination of solubilities using small amounts
of compounds (5–50 mg) was used. Two types of precipitation were observed during the kinetic solubility determinations: i) a disperse precipitation where the solution became foggy with very small particles uniformly distributed in the solution,
and ii) discrete precipitation characterized by formation of crystals that rapidly sediment. The thermodynamic solubility was determined
by shake flask and titrimetrically using a pH-STAT. The pH-STAT titrimetric method for the pH-thermodynamic solubility profile determination eliminates the buffer species and represents a new way to approach the solubility
characterization of pharmaceutical compounds. The strengths of the turbidimetric method for determining the kinetic solubility
are its rapidity, minimal compound requirements, and suitability for high throughput screening. The limitations are that the
maximum solubility is limited to less than 100 mg · cm−3, and the precipitation of trace impurities cannot be distinguished from precipitation of the analyte. The pH-STAT titrimetric approach for the thermodynamic solubility has a lower throughput and is suitable for the characterization
of the lead candidate. It is not limited in its solubility range and provides a common basis for the comparison of the solubility
values at different pH values in contrast to traditional buffered systems.
Received August 21, 2000. Accepted (revised) February 5, 2001 相似文献
18.
Ivan Potočňák Michal Dunaj-Jurčo Dušan Mikloš Lothar Jäger 《Monatshefte für Chemie / Chemical Monthly》2001,132(3):315-327
Summary. The structure of the new compound [Cu(bpy)2N(CN)2]C(CN)3 (6) is compared with thestructures of six copper(II) coordination compounds with phenanthroline or bipyridine ligands and N-donor
pseudohalide anions: [Cu(phen)2NCS]C(CN)3 (1), [Cu(bpy)2NCS]C(CN)3 (2), [Cu(phen)2NCS]ONC(CN)2 (3), [Cu(phen)2N(CN)2]C(CN)3 (4), [Cu(bpy)2C(CN)3]C(CN)3 (5), and [Cu(bpy)2NCO]C(CN)3 (7). The Cu(II) atoms in all above compounds are five-coordinated with an N-donor atom of the pseudohalide anion located in
the equatorial plane of a deformed trigonal bipyramid. The shape of the coordination polyhedra and the degree of trigonal
bipyramidal distortion towards a tetragonal pyramid are discussed and described using one electronic and several structural
criteria which are discussed and compared.
Received July 24, 2000. Accepted October 18,2000 相似文献
19.
Summary. A hypericin derivative containing ω,ω ′-4-dimethylaminobenzal residues was shown to undergo an intramolecular [2 + 2] cycloaddition
upon irradiation leading to a cyclobutane derivative whose main absorption band is hardly shifted as compared to hypericin.
The corresponding ω-substituted derivative displayed a 34 nm bathochromic shift and a strongly reduced fluorescence quantum
yield rendering it a nice candidate for a photodynamic therapy agent. Unfortunately, however, it produced virtually no photosensitized
active oxygen species, making it thus unsuited for this purpose.
Received July 11, 2001. Accepted July 18, 2001 相似文献