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31.
Dobrochna Matkowska Maciej Gola Marcin ?nie?ek Piotr Cmoch Krzysztof Staliński 《Journal of organometallic chemistry》2007,692(10):2036-2045
A series of triorganotin hydrides and diorganotin dihydrides containing the optically active 2-(4-isopropyl-2-oxazolinyl)-5-phenyl ligand have been characterized by means of the multinuclear low-temperature NMR investigations, the results of which are discussed. In the corresponding organotin hydrides values of the 1J(1H-117/119Sn) couplings appeared to be temperature dependent, supporting an axial/equatorial position of the hydrogen attached to the tin. 相似文献
32.
Marek Szymo
ski Jacek Ko
odziej Zbigniew Postawa Pawel Czuba Piotr. Piatkowski 《Progress in Surface Science》1995,48(1-4):83-96
Inelastic interactions of electrons with surfaces of ionic crystals result in emission of various particles such as ions, atoms and molecules. We will review such electron-stimulated desorption processes for the particular class of ionic crystals, namely for alkali halides. In this case, a dominant fraction of the emission is in the form of halogen and alkali atoms characterized by a thermal (Maxwellian) spectrum of translational energies. For several alkali halides (potassium and rubidium chlorides, bromides, and iodides), however, a significant part of the halogen atoms is ejected with nonthermal energies, i.e. energies of the order of 0.1 eV. The results of recent systematic studies of angular-resolved kinetic energy distributions of the emitted particles will be reported and current views on the electronic mechanisms of desorption will be described. In particular, it will be shown that the ESD mechanism can be understood in terms of the model involving a surface localisation of the so called “hot-holes” created by electron bombardment of alkali halides. A role of hot holes in ESD processes will further be discussed in relation to very recent experimental results obtained for the KBr crystals doped with In impurities which act as efficient hole traps. 相似文献
33.
Summary Single reverse water-gas shift (RWGS) and dehydrogenation of propane with CO2(DH-CO2) reactions in the presence and absence of the CrOx/SiO2 catalyst have been studied between 673 and 873 K. It was found that the CrOx/SiO2 catalyst is active both in the dehydrogenation of propane and in the RWGS reactions. The obtained results suggest that the
dehydrogenation of propane to propene in the presence of CO2on CrOx/SiO2can be facilitated by the RWGS reaction.</o:p> 相似文献
34.
Acidolytic cleavage of unsymmetrically substituted dithioacetal monoxides, ArCH(SR)S(O)Me has been used to prepare linear unsymmetrical disulfides RSSMe. Disproportionation was suppressed by the addition of a small amount of benzyl mercaptan. The required starting materials were conveniently obtained from appropriately substituted sulfines ArC(=SO)SR and methyl lithium. The following disulfides were prepared: R =n-C4H9 (73.5%), n-C7H15 (78%), Ph (77.3%), AcO(CH2)10 (81.5%).The unsymmetrical dithioacetal PhCH(SEt)SC7H15-n gave upon oxidation with one equivalent of peracid a mixture of two dithioacetal monoxides which on treatment with HClO4 led to three disulfides. This result is discussed in term of the mechanism of acidolysis. 相似文献
35.
Kabatc J Jedrzejewska B Orliński P Paczkowski J 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,62(1-3):115-125
The photophysical and photochemical properties of p-substitued 2-styryl-ethylbenzothiazolium iodides, possessing different electron-withdrawing or electron-donating groups are described. The dyes were prepared by the condensation of 3-ethyl-2-methylbenzothiazole salts with p-substituted benzaldehydes. The synthesis of suitable substrates is presented as well. We describe here the absorption, emission spectra and the luminescence quantum yield of hemicyanine dyes (SH) measured in 11 different organic solvents of varying polarity. Molecular structure of the synthesized dyes was established by (1)H NMR, electronic absorption and fluorescence spectrometry. The spectral data confirmed that all the compounds exist in E-configuration of their styryl residues. The planar molecular conformation is typical for the compounds with five-membered side aromatic moieties (for example benzothiazole). The compounds possessing N-alkyl substituent in phenyl ring, in contrast to the compounds with other substituents, exhibit low fluorescence quantum yield in THF solution. This indicates that for N-alkyl derivatives the non-radiative processes are much more effective than the radiative ones. The electronic absorption and fluorescence emission spectra of tested dyes demonstrate high sensitivity to the nature of substituent introduced into the aromatic ring. 相似文献
36.
The synthesis of well-defined luminescent organoboron polymers via a novel three-step procedure starting from silylated polystyrene is reported. Highly selective borylation of poly(4-trimethylsilylstyrene) (PS-Si), followed by replacement of the bromine substituents in poly(4-dibromoborylstyrene) (PS-BBr) with substituted thienyl groups (R = H, 3-hexyl, 5-hexyl), and final introduction of the 8-hydroxyquinolato moiety yields a series of new organoboron quinolate polymers in 67-83% isolated yield. The hexyl-substituted polymers are highly soluble and solution-processable yielding thin films that efficiently emit light at 513-514 nm upon excitation at 395 nm. 相似文献
37.
Kujawa P Moraille P Sanchez J Badia A Winnik FM 《Journal of the American Chemical Society》2005,127(25):9224-9234
The layer-by-layer growth of multilayer assemblies of two polysaccharides, the polyanion hyaluronan (HA) and the polycation chitosan (CH), was investigated using atomic force microscopy (AFM) and surface plasmon resonance (SPR) spectroscopy, with primary emphasis on the effect of the polysaccharide molecular weights on the film thickness and surface morphology. The HA/CH multilayers exhibit an exponential increase of the optical film thickness with the number of deposited bilayers. We show that the multilayer thickness at a given stage depends on the size of both CH, the diffusing polyelectrolyte, and HA, the non-diffusing species. Assemblies (12 bilayers) of high molecular weight polysaccharides (HA, 360,000; CH, 160,000) were twice as thick (approximately 900 nm vs approximately 450 nm) as those obtained with low molecular weight polymers (HA, 30,000; CH, 31,000), as assessed by AFM scratch tests. The exponential growth rate is the same for the high and low molecular weight pairs; the larger film thicknesses observed by SPR and by AFM arising from an earlier onset of the steep exponential growth phase in the case of the high molecular weight pair. In all cases, isolated islets form during the deposition of the first CH layer onto the underlying HA. Upon further film growth, individual islets coalesce into larger vermiculate features. The transition from distinct islands to vermiculate structures depends on the molecular weights of the polysaccharides and the lower molecular weight construct presents larger worm-like surface domains than the high molecular weight pair. 相似文献
38.
In this article we study the effect of energetic heterogeneity of a crystalline surface on the adsorption of hydrogen ions (protons) from the liquid phase. In particular, we examine the influence of the shape of the adsorption energy distribution on the equilibrium isotherms of hydrogen ions. To that purpose, a few popular distribution functions, including rectangular, exponential, and asymmetric Gaussian are considered. Additionally, multimodal distribution functions, which may correspond to the adsorption on different crystal planes of the oxide, are also used. Lateral interactions between adsorbed charges are modeled using the potential function proposed by Borkovec et al., which accounts also for polarization of the liquid medium. The results presented here are obtained using both Monte Carlo (MC) simulations and theoretical calculations involving Mean Field Approximation (MFA). They indicate that increased energetic heterogeneity of the adsorbing surface may, in general, considerably change the behavior of the adsorption isotherms, regardless of the assumed distribution function. It is also shown that the predictions of the proposed theory are consistent with the data obtained from the MC simulations. 相似文献
39.
Piotr Ziba Agnieszka Skara Emilia Berna Agata Krakowska Katarzyna Sukowska-Ziaja Edward Kunicki Magorzata Suchanek Boena Muszyska 《Molecules (Basel, Switzerland)》2021,26(11)
The use of substrates supplemented with minerals is a promising strategy for increasing the nutraceutical value of Pleurotus spp. The current research was performed to analyze the effect of substrate supplementation with magnesium (Mg) salts on the Mg content, biomass, and chemical composition of pink oyster mushroom (Pleurotus djamor) fruiting bodies. Before inoculation, substrate was supplemented with MgCl2 × 6 H2O and MgSO4, both salts were applied at three concentrations: 210, 420, and 4200 mg of Mg per 2 kg of substrate. The harvest period included three flushes. Substrate supplementation with 4200 mg of Mg caused the most significant decrease in mushroom productivity, of about 28% for both Mg salts. The dry matter content in fruiting bodies was significantly lower in the treatment in which 210 mg of Mg was applied as MgSO4 in comparison to the control. Supplementation effectively increased the Mg content in fruiting bodies of P. djamor by 19–85% depending on the treatment, and significantly affected the level of remaining bioelements and anions. One hundred grams of pink oyster fruiting bodies, supplemented with Mg salts, provides more than 20% of the Mg dietary value recommended by the Food and Drug Administration (FDA); thus, supplementation can be an effective technique for producing mushrooms that are rich in dietary Mg. Although P. djamor grown in supplemented substrate showed lower productivity, this was evident only in the fresh weight because the differences in dry weight were negligible. Mg supplementation increased the antioxidant activity of the fruiting bodies, phenolic compounds, and some amino acids, including L-tryptophan, and vitamins (thiamine and l-ascorbic acid). 相似文献
40.
Dorota Gryko DanielT. Gryko Hanna Sierzputowska‐Gracz Piotr Piatek Janusz Jurczak 《Helvetica chimica acta》2004,87(1):156-166
The efficient synthesis of eight new macrocyclic amides (lactams) via reaction of diesters with diamines under normal dilution conditions is described. The role of intermolecular H‐bond formation and steric hindrance is discussed based on 1H‐ and 15N‐NMR studies of appropriate model compounds. Principles for the optimal choice of esters that can be efficiently transformed into diamides have been developed. 相似文献