共查询到20条相似文献,搜索用时 15 毫秒
1.
A. Staško V. Brezová P. Rapta S. Biskupič K. -P. Dinse A. Gügel 《Research on Chemical Intermediates》1997,23(5):453-478
Photochemically induced electron transfer in homogeneous systems (using triethylamine donor) and heterogeneous systems (using
photoexcited TiO2 suspension) was applied in in situ reduction of [60]fullerene. The anion radicals generated were characterized by means of EPR and VIS/near-IR spectroscopy.
Narrow EPR lines were found. Radical A with gA=2.0000 and peak-to-peak width, ppA=0.09mT was observed as the primary product; followed by its consecutive product B with gB=2.0006, ppB=0.04mT, and in some cases product C with gC=2.0009 and ppc<0.1 mT. Radical A was assigned to [60]fullerene mono-anion, also characterized by a near-IR band at 1077 nm. B is presumably di-anion or a dimeric form of mono-anion. Identical results were also obtained using cathodic in situ reduction. Applying these generation techniques to [60]fullerene derivatives produced narrow EPR lines analogous to those
described for pristine [60]fullerene. This was the case not only in organic solvents, but also in aqueous solutions. The results
obtained present a contrast with the original ex situ EPR investigations describing [60]fullerene mono-anion with wide lines. According to the results presented here, the narrow
and wide EPR lines do not represent contradictory phenomena, but are an integral part of the relatively complicated manifestations
of various fullerene states and both will have to be seriously considered in the future. 相似文献
2.
V. K. Koltover Ya. I. Estrin V. P. Bubnov E. E. Laukhina 《Russian Chemical Bulletin》2000,49(10):1745-1748
The EPR spectra of endohedral metallofullerenes (EMF), La-EMF and Y-EMF, which were free of admixtures of C60 and of other empty fullerenes, were examined. Endohedral metallofullerenes were prepared by extraction of fullerene-containing
soots with DMF. New signals withg factors close to those of fullerene radical anions were observed in the EPR spectra of solutions of EMF in DMF and DMSO.
At −20 °C, these signals are observed as a doublet (ΔH
pp
≈0.04 mT) and singlet (ΔH
pp
≈0.01 mT) in solutions of La-EMF and Y-EMF, respectively. These EPR signals belong to solvated La@C82 and Y@C82 molecules and are characterized by small hyperfine interaction constantsa
M due to a substantial decrease in the spin density of the unpaired electron at the metal atom.
Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1765–1769, October, 2000. 相似文献
3.
Ladislav Kosa Iveta Macková Ivo Proks Ondrej Pritula Ľubomír Smrčok Miroslav Boča Håkan Rundlőf 《Central European Journal of Chemistry》2008,6(1):27-32
Three thermal effects on heating/cooling of K2TaF7 in the temperature interval of 680–800°C were investigated by the DSC method. The values determined for the enthalpy change
of the individual processes are: ΔtransIIHm(K2TaF7; 703°C) = 1.7(2) kJ mol−1, ΔtransIHm(K2TaF7; 746°C) = 19(1) kJ mol−1 and ΔtransIIIHm(K2TaF7; 771°C) = 13(1) kJ mol−1. The first thermal effect was attributed to a solid-solid phase transition; the second to the incongruent melting of K2TaF7 and the third to mixing of two liquids. These findings are supported by in situ neutron powder diffraction experiments performed in the temperature interval of 654–794°C.
相似文献
4.
J. Svorec M. Valko J. Moncol M. Mazúr M. Melník J. Telser 《Transition Metal Chemistry》2009,34(2):129-134
An EPR method involving measurement of half-field transitions was applied to determine the intermolecular Cu–Cu distances
in copper(II)-carboxylate complexes with biologically important ligands. The experimental powder EPR spectra are composed
of allowed (ΔM
S
= ±1) transitions centered at ~3,200 Gauss and of weak intensity, nominally forbidden, half-field (ΔM
S
= ±2) peaks observable at ~1,600 Gauss. Values of the average interspin distance for each complex were determined from the
ratios of integrated allowed and forbidden peak areas using each of several methods. The calculated interspin distances were
correlated with the copper–copper distances experimentally obtained by X-ray crystallography. The distances determined from
the EPR spectra agree well with the X-ray determined values when the crystallographic value for one member of a series is
used to calibrate the series. Less satisfactory agreement is found when methods based on Cu-spin-label systems are used. 相似文献
5.
Oztekin Algul Asiye Meric Serpil Polat N. Didem Yuksek Mehmet S. Serin 《Central European Journal of Chemistry》2009,7(3):337-342
Comparative studies were performed on a series of 2,4-di and 2,3,4-trisubstituted benzimidazo[1,2-a]pyrimidines, which were
synthesized with conventional and microwave heating methods. In microwave irradiation method, approximately, 95–97.5% of the
reaction time was increased and 1–45% yield increase was obtained. All compounds were able to inhibit the growth of the screened
microorganisms in vitro with MIC values between 3.9–250 μg mL−1. The highest activity was expressed by compound IIId (2,4-diphenyl-benzo[4,5]imidazo[1,2-a] pyrimidine), which has the MIC
value of 3.9 μg mL−1 and 31.2 μg mL-1 for Penicillium natatum ATCC 24791 and E. faecalis ATCC 29212, respectively.
相似文献
6.
Natarajan Thilagavathi Chinnasamy Jayabalakrishnan 《Central European Journal of Chemistry》2010,8(4):842-851
Ru(III) complexes of the type [RuXB(L)2] have been prepared by the reaction of 3,4-dihydropyrimidin-2(1H)-ones/thiones (HL1–HL4) with the precursors of the type [RuX3B3] where X=Cl or Br; B=PPh3 or AsPh3 and L is the deprotonated ligand. The synthesized complexes were characterized by physico-chemical methods, electrochemical
and magnetic moment data. The catalytic efficiency of the complexes were examined in the oxidation of alcohols and antimicrobial
studies were also carried out.
相似文献
7.
Nermin Kasapoglu Bahar Birsöz Abdülhadi Baykal Yüksel Köseoglu Muhammet S. Toprak 《Central European Journal of Chemistry》2007,5(2):570-580
A series of Ni doped cobalt ferrite compounds with the formula Ni
χ
Co1−χ
Fe2O4 where x=0, 0.2, 0.4, 0.6, 0.8, and 1.0 were prepared using a hydrothermal method and subsequently sintered/annealed at 600
°C for 3 h. The influence of the Ni content on the lattice parameter, a, stretching vibration and the magnetization of specimens were subsequently studied. XRD and FTIR were used to investigate
structure and composition variations. All samples were found to have a cubic spinel structure. SEM was used to study morphological
variations. The results indicate that the average particle sizes are between 30–35 nm with a narrow size distribution along
with nanocrystals forming of regular octahedrons. A decrease in the peak to peak line width and increase in resonance field
with increasing Ni content were observed from ESR measurements. Based on ESR results, a core-shell type of formation was proposed
where the core is made up of undoped CoFe2O4 and the shell is Ni2+ doped CoFe2O4.
相似文献
8.
An organic-inorganic composite, poly-o-anisidine Sn(IV) phosphate, was chemically synthesized by mixing ortho-anisidine into
gels of Sn(IV) phosphate with different mixing volume ratios. Studies on the effect of eluant concentration, elution behavior
and separation of metal ions were carried out to understand the ion-exchange capabilities. Due to Cd(II) selective nature
of composite, revealed by distribution studies, Cd(II) ion selective membrane electrode was fabricated. The analytical utility
of the electrode was established by employing it as an indicator electrode in electrometric titrations having fast response
time, 3–5s, and long life span of six months. Some physical parameters like self-diffusion coefficient (D0), activation energy (Ea) and entropy of activation (ΔS0) have been evaluated under conditions favoring a particle diffusion-controlled mechanism by studying ion-exchange kinetics.
相似文献
9.
Simona Strazdaite Ruta Bariseviciute Justinas Ceponkus Valdas Sablinskas 《Central European Journal of Chemistry》2012,10(5):1647-1656
Theoretical calculations of structures, stability and vibrational spectra of 1-butene secondary ozonide (SOZ) conformers were performed using DFT method B3LYP with a 6-311++G(3df, 3pd) basis set. The calculations predict six staggered structures of 1-butene SOZ. The FTIR spectra of 1-butene SOZ isolated in Ar, N2 and Xe matrices were recorded. It was found that nitrogen is the best suited for the matrix isolation of 1-butene SOZ. The bandwidth of the spectral bands of the ozonide isolated in nitrogen was as narrow as 2 cm−1. For the first time the existence of five conformers of 1-butene SOZ were confirmed experimentally by means of matrix isolation infrared absorption spectroscopy. The equatorial gauche (∠OCCC=−66.1°) conformer was proved theoretically and experimentally to be the most stable. It was found that due to high potential barriers of the conformational transitions annealing of the matrix is useless for the assignment of spectral bands to various conformers of 1-butene SOZ. Using the hot nozzle technique the van’t Hoff experimental plots were made for three additional conformers of 1-butene SOZ and experimental ΔH values for these additional conformers were established. The crystallization problems of 1-butene SOZ are discussed which accounts for the rich conformational diversity of the ozonide as well as high conformational barriers for axial-equatorial transitions. 相似文献
10.
Valentina T. Getova Ivayla N. Pantcheva Darvin S. Ivanov Dimitar R. Mehandjiev Vassil Skumryev Panayot R. Bontchev 《Central European Journal of Chemistry》2007,5(1):118-131
The complexation of the non-selective β-blocker nadolol, HL, 1 with copper(II) leads to formation of mono-and dinuclear complexes depending mainly on the metal-to-ligand molar ratio. The
mononuclear violet complex CuL2·2Solv, 2, was obtained in a soluble form at metal-to-ligand molar ratio Cu(II): HL ≤ 1: 10 in methanolic or slightly alkaline aqueous
solutions. The dinuclear green complex Cu2L2Cl2·H2O, 3 was synthesized at Cu(II): HL ≥ 1: 2 molar ratio in methanolic solutions. The complexes were studied using spectral (UV-Vis,
FT-IR, EPR), magnetochemical, thermogravimetric methods and elemental analysis. In the complexes nadolol acts as a monoanionic
bidentate ligand coordinated to copper(II) through the NH-and the deprotonated OH-groups of its aminoalcohol fragment.
相似文献
11.
Krzysztof Tadyszak Agnieszka Boś‐Liedke Jan Jurga Mikołaj Baranowski Radosław Mrówczyński Wojciech Chlewicki Stefan Jurga Tomasz Czechowski 《Magnetic resonance in chemistry : MRC》2016,54(2):136-142
A study concerning the image quality in electron paramagnetic resonance imaging in two‐dimensional spatial experiments is presented. The aim of the measurements was to improve the signal‐to‐noise ratio (SNR) of the projections and the reconstructed image by applying modulation amplitude higher than the radical electron paramagnetic resonance linewidth. Data were gathered by applying four constant modulation amplitudes, where one was below 1/3 (Amod = 0.04 mT) of the radical linewidth (ΔBpp = 0.14 mT). Three other modulation amplitude values were used in this experiment, leading to undermodulated (Amod < 1/3 ΔBpp), partially overmodulated (Amod ~ 1/3 ΔBpp) and fully overmodulated (Amod > > 1/3 ΔBpp) projections. The advantages of an applied overmodulation condition were demonstrated in the study performed on a phantom containing four shapes of 1.25 mM water solution of 2, 2, 6, 6‐tetramethyl‐1‐piperidinyloxyl. It was shown that even when the overmodulated reference spectrum was used in the deconvolution procedure, as well as the projection itself, the phantom shapes reconstructed as images directly correspond to those obtained in undermodulation conditions. It was shown that the best SNR of the reconstructed images is expected for the modulation amplitude close to 1/3 of the projection linewidth, which is defined as the distance from the first maximum to the last minimum of the gradient‐broadened spectrum. For higher modulation amplitude, the SNR of the reconstructed image is decreased, even if the SNR of the measured projection is increased. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
12.
Lyudmila A. Belyakova Oleksandra M. Shvets Diana Yu. Lyashenko 《Central European Journal of Chemistry》2008,6(4):581-591
The present work investigates the adsorptive interactions of Hg(II) ions in aqueous medium with hydroxylated silica, aminopropylsilica
and silica chemically modified by β-cyclodextrin. Batch adsorption studies were carried out with various agitation times and
mercury(II) concentrations. The maximum adsorption was observed within 15–30 min of agitation. The kinetics of the interactions,
tested with the model of Lagergren for pseudo-first and pseudo-second order equations, showed better agreement with first
order kinetics (k1 = 3.4 ± 0.2 to 5.9 ± 0.3 min−1). The adsorption data gave good fits with Langmuir isotherms. The results have shown that β-cyclodextrin-containing adsorbent
has the largest adsorption specificity to Hg(II): K
L
= 4125 ± 205 mmol−1. “β-cyclodextrin-NO3-” inclusion complexes with ratio 1: 1 and super molecules with composition C42H70O35 ⊎ 3 Hg(NO3)2 are formed on the surface of β-cyclodextrin-containing silica.
相似文献
13.
Helena Dodziuk Anna Bielejewska Wojciech Schilf Haruhisa Ueda 《Central European Journal of Chemistry》2011,9(6):1056-1061
The NMR spectra of [2.2]paracyclophane with β- or γ-cyclodextrin in DMF-d7 at room temperature do not show significant complexation, while HPLC of the complexes in mixed H2O:alcohol solvents demonstrate complexation with different stoichiometries. At 243 K in DMF solution the H3 and H5 NMR signals
of γ-cyclodextrin (but not β) exhibit complexation-induced chemical shifts denoting complex formation. According to HPLC,
at room temperature the [2.2]paracyclophane complex with β-cyclodextrin in 20% H2O:EtOH exhibits 1:2 stoichiometry with K
1 = 1×102 ± 2, K
2 = 9.0×104 ± 2×103 (K = 9×106) while that with γ-cyclodextrin in 50% H2O:MeOH exhibits 1:1 stoichiometry with K
1 = 4×103 ± 150 M−1. Thermodynamic parameters for both complexes have been estimated from the retention time temperature dependence. For the
β-cyclodextrin complexation at 25°C ΔG
0
CD is −39.7 kJ mol−1 while ΔH
0
CD and ΔS
0
CD are −88.2 kJ mol−1 and −0.16 kJ mol−1 K−1. For γ-cyclodextrin, the corresponding values are ΔG
0
CD = −20.5 kJ mol−1, ΔH
0
CD = −33.5 kJ mol−1 and ΔS
0
CD = −0.04 kJ mol−1 K−1.
相似文献
14.
Martin Adam Petr Dobiáš Petra Pavlíková Karel Ventura 《Central European Journal of Chemistry》2009,7(3):303-311
The analytical microextraction methods of gas chromatography coupled with flame ionisation detector (GC-FID) for determination
of selected essential oils in herbs were proposed. Two microextraction methods for the isolation of essential oils from plants
such as Lavandula spica L., Melissa officinalis L., Mentha piperita L. and Salvia officinalis L. were used. The methods of solid-phase and single-drop microextractions, were optimised and compared. The obtained LOD
values for all studied essential oils were found to be within 2.5–20.5 μg for SDME and 57.0–139.8 μg for SPME method per 100
g of dried sample leaves. The appropriate LOQ values were then 8.4–68.4 μg for SDME and 189.8–466.1 μg for SPME of target
analytes per 100 g of dried sample leaves.
相似文献
15.
Helena Absolínová Luděk Jančář Irena Jančářová Jaroslav Vičar Vlastimil Kubáň 《Central European Journal of Chemistry》2010,8(3):626-632
Time stability, acid-base and UV-VIS spectral properties of dihydrochelerythrine (DHCHE) were studied spectrophotometrically
in water:methanol and water:ethanol media. DHCHE is stable in strongly acid milieu (pH < 3) and at the higher amounts (60%
v/v) alcohol. Acid-base characteristics and UV-VIS spectral properties of chelerythrine (CHE) were studied in aqueous solutions
in the presence of different concentrations of HCl, HNO3, H2SO4, H3PO4 and their mixtures. Remarkable shifts of formation parts of absorbance-pH (A-pH) curves to the alkaline medium were observed depending on the type and concentration of inert electrolyte (most remarkable
for HNO3 and HCl). The corresponding equilibrium constants pKR+ of the transition reaction between charged iminium Q+ and uncharged QOH (pseudo-base, 6-hydroxy-dihydro derivative) forms of chelerythine were calculated using a numerical interpretation
of A-pH curves by a SQUAD-G computer program which ranged from 8.51–9.31. The highest changes of ΔpK
R+ (0.75 and 0.53) were observed for H3PO4 and H2SO4, respectively. The priority effect of ionic species and ionic strength was confirmed in the presence of additions of NaCl
and KCl. The strength of interaction of CHE with biomacromolecular compounds (i.e., peptides, proteins, nucleic acids etc.) may be affected because of the observed influence of both cation and anion of the inert electrolyte on acid-base behavior.
相似文献
16.
Nikolay Kaloyanov Mihail Neykov Diana W. Wesselinova Georgi D. Dimitrov 《Central European Journal of Chemistry》2012,10(4):1034-1041
Novel heavy metal complexes: Sr(5-NH2-phen)4(NO3)(OH)(H2O)2 (1) (synthesized via a static self-assembly process) and Sn(phen)(NO3)(OH)(H2O) (2), Sn(5-NH2-phen)(OH)(Cl)(H2O) (3), Pb(5-NH2-phen)(NO3)2(H2O) (4) (obtained via metal competitive reactions under mild conditions) were reported. The coordination compounds were characterized by elemental
analysis, FTIR-spectroscopy and FAB-mass spectrometry. Their cytotoxicity was measured by MTS-test towards human tumour (MDA-MB-231,
HT-29, HeLa, HepG2) and non-tumour diploid (Lep-3) cell lines. The most pronounced cytotoxic effect on all cancer lines showed
1 and 4 at their high concentrations as well as 1 at its lower ones (≤ 4×10−2 mg). Therefore, strontium complex of 5-amino-o-phenanthroline (1) exhibited the widest antitumour spectrum activity, having no toxicity to non-tumour cells at quantities ≤ 4×10−2 mg. The computed EC50 values of 1–4 against MDA-MB-231, HT-29, HeLa, HepG2 varied from 1.40×10−3 to 6.31×10−6 M. Towards Lep-3 substances 2–4 showed IC50 7.52×10−4 − 0.44 M. Substance 1 possess EC50=1.26×10−7 M to the non-tumour cells.
相似文献
17.
Abdulhadi Baykal Hüseyin Kavas Zehra Durmu? Mine Demir Sinan Kazan Ramazan Topkaya Muhammet S. Toprak 《Central European Journal of Chemistry》2010,8(3):633-638
We report on the synthesis of Mn3O4 nanoparticles (NPs) using a novel sonochemical method without requiring any pH adjustment. Synthesized material was identified
as tetragonal hausmannite crystal structure model of Mn3O4 from XRD analysis. Crystallite size was estimated from x-ray line profile fitting to be 17±5 nm. FTIR analysis revealed stretching
vibrations of metal ions in tetrahedral and octahedral coordination confirming the crystal structure. TEM analysis revealed
a dominantly cubic morphology of NPs with an average size of ∼20 nm. Magnetic evaluation revealed a blocking temperature,
T
B of 40 K above which the material behaves paramagnetic. Asymmetric coercive field is attributed to the interaction between
ferromagnetic Mn3O4 and antiferromagnetic Mn oxide at the surface of nanoparticles.
相似文献
18.
Optimum conditions for synthesizing monoclinic and triclinic Mg2B2O5 compounds by high-temperature solid-state reactions were investigated. Mixtures composed of boric acid and magnesium oxide
at MgO:B2O3 mole ratios of 1:0.25, 1:0.5 and 1:1.5 were heated for 1 hour at temperatures between 600–1050°C and the formed phases were
identified by XRD analysis. Monoclinic Mg2B2O5 was formed by heating at 850°C for 4 hours together with minimum amounts of triclinic Mg2B2O5, while triclinic Mg2B2O5 was formed as a single phase at 1050°C for the same reaction time. The products obtained at optimum conditions were subjected
to a series of tests to determine their chemical compositions, particle size distributions, surface area values, IR spectra
and TG/DTA patterns.
相似文献
19.
Eliza Blicharska Łukasz Komsta Ryszard Kocjan Anna Gumieniczek Artur Robak 《Central European Journal of Chemistry》2010,8(2):264-268
An increasing interest in determination of various macro- and microelements in medicinal plants has been observed. The majority
of studies are carried out using one mineralization method without any optimization. The present study demonstrates that changes
in mineralization parameters can significantly affect the recovery of the elements determined. In the study, the dried plant
material was mineralized in 12 ways and iron (Fe), copper (Cu), zinc (Zn), nickel (Ni) and manganese (Mn) levels were determined.
The samples were mineralized in the dry or open microwave mode as well as 10 closed microwave modes. The influence of acid
amounts, irradiation power and time, addition of hydrogen peroxide and perfluoric acid was examined. All parameters were shown
to be critical — good efficiency was observed with larger amounts of acid. The determined content varied significantly in
the same sample and were in the ranges (ug g−1): 46–136 (Fe), 1.4–11.8 (Cu), 4.0–11.3 (Ni), 15.4–53.8 (Zn) and 9.5–67.6 (Mn). Increased irradiation resulted in the loss
of copper and zinc and better recovery of nickel. The results demonstrate that such determinations should include the mineralization
optimization step.
相似文献
20.
Radostina I. Alexandrova Tanya Zhivkova Marin Alexandrov Georgi Miloshev Milena Georgieva Ivayla N. Pantcheva Mariana Io. Mitewa 《Central European Journal of Chemistry》2012,10(5):1464-1474
The anticancer activity of monensic acid (MonH) and its biometal(II) complexes [M(Mon)2(H2O)2](M = Mg, Ca, Mn, Co, Ni, Zn) was evaluated against cultured human permanent cell lines established from glioblastoma multiforme (8MGBA) and cancers of the lung (A549), breast (MCF-7), uterine cervix (HeLa) and liver (HepG2). The viability and proliferation of the non-tumor human embryonic cell line Lep3 was also tested. The investigations were carried out using a thiazolyl blue tetrazolium bromide test, neutral red uptake cytotoxicity assay, crystal violet staining, colony forming method and double staining with acridin orange and propidium iodide. The results obtained reveal that the compounds applied at concentrations of 0.5–25 μg mL−1 for 24–72 h decrease the viability and proliferation of the treated cells in a time- and concentration-dependent manner. The metal(II) complexes studied (especially those of Co(II), Ni(II) and Zn(II)) have been found to express stronger cytotoxic and cytostatic activities than the non-coordinated monensic acid. The non-tumor human cell line showed strong chemosensitivity towards compounds tested comparable to that of cultured human tumor cell lines. 相似文献