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51.
Jacek Wójcik Krystyna Kamienska-Trela Magdalena Pecul Elzbieta Bartoszak-Adamska Siergiej I Vdovienko Igor I Gerus 《Chemphyschem》2004,5(2):209-215
Concentration- and temperature-dependent IR, NMR and dipole-moment studies on 4-N,N-dimethylamino-1,1,1-trifluoro-3-buten-2-one and two of its higher homologues showed that these compounds undergo reversible dimerization in nonpolar solvents. Antiparallel "closed" dimers are formed with a network of improper intermolecular C-H...O hydrogen bonds. Quantitative analysis of the 1H NMR data yielded delta H0 = -17.6 kJ mol-1 and delta S0 = -46.9 J deg-1 mol-1. The interactions observed are the strongest among those involving a C-H group reported so far. The complex described here is the first example of a cyclic complex stabilized by two improper C-H...O hydrogen bonds. The conclusions drawn from the solution and solid-state data were confirmed by ab initio calculations. 相似文献
52.
Potrzebowski MJ Tadeusiak E Misiura K Ciesielski W Bujacz G Tekely P 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(21):5007-5011
It is shown that enantiomers and racemates that have identical isotropic NMR chemical shift as well as anisotropic chemical-shift tensor parameters can be easily distinguished by means of the ODESSA (One Dimensional Exchange Spectroscopy by Sideband Alternation) technique. The method is based on the fact that the molecular symmetries and packing of enantiomers and racemates are usually significantly different. The power of the proposed approach is demonstrated by employing as model compounds P-chiral oxazaphosphorine derivatives, which are widely used in clinical oncology. Correlation of the amplitude of the ODESSA decay (AOD) with enantiomeric excess is also presented. 相似文献
53.
The photochemical addition of nitrenes to isonitriles leads to carbodiimides or/and ureas. The application of this reaction to 1-isocyano sugars offers an approach to the synthesis of glycosylbarbiturates. 相似文献
54.
The crystal structure of chromone hydrazonium salt (±)-1-hydroxy-1-oxo-3-phenyl-1,3-dihydro-1λ5-2,1-oxaphospholo[4,5-b]-4H-1-benzopyran-4-one (2) and its acid (±)-1-hydroxy-1-oxo-3-phenyl-1,3-dihydro-1λ5-2,1-oxaphospholo[4,5-b]-4H-1-benzopyran-4-one (3) have been solved. Condensed rings are almost planar, the P atom adopts nearly tetragonal geometry. The molecular packing is influenced by inter- and intramolecular contacts, which can be recognized as hydrogen bonds. 相似文献
55.
Magdalena Maecka Werner Massa Elbieta Budzisz 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(10):o762-o764
The title compound, C18H14O4, forms a supramolecular structure viaπ–π stacking and weak C—H⋯O and C—H⋯π interactions. The benzopyran moiety is almost planar. The benzene ring of the phenylmethyl acetate substituent is nearly perpendicular to the fused benzene and pyran rings and also to the methyl acetate group. 相似文献
56.
Slawomir Jarosz Elzbieta Kozlowska Jerzy Sitkowski Lech Stefaniak 《Journal of carbohydrate chemistry》2013,32(6):911-916
Abstract The 119Sn NMR spectra of several sugar-tin derivatives were recorded. The geometric and steric isomers of all of the organotin derivatives studied were easily differentiated by 119Sn NMR. The appropriate 119Sn resonances are: ca - 50 ppm for trans and ?60 ppm for cis vinyltin derivatives (1-3), ca 16 ppm for allyltins 4-6, and ca ?32 ppm for tin-carbinols 9 and 11. When the hydroxyl group in carbinol 9 was converted to an O-acetyl group, the chemical shift of 119Sn was shifted to ?22 ppm. 相似文献
57.
Vibe B. Jakobsen Elzbieta Trzop Laurence C. Gavin Emiel Dobbelaar Shalinee Chikara Xiaxin Ding Kane Esien Helge Müller‐Bunz Solveig Felton Vivien S. Zapf Eric Collet Michael A. Carpenter Grace G. Morgan 《Angewandte Chemie (International ed. in English)》2020,59(32):13305-13312
Domain wall motion is detected for the first time during the transition to a ferroelastic and spin state ordered phase of a spin crossover complex. Single‐crystal X‐ray diffraction and resonant ultrasound spectroscopy (RUS) revealed two distinct symmetry‐breaking phase transitions in the mononuclear Mn3+ compound [Mn(3,5‐diBr‐sal2(323))]BPh4, 1. The first at 250 K, involves the space group change Cc→Pc and is thermodynamically continuous, while the second, Pc→P1 at 85 K, is discontinuous and related to spin crossover and spin state ordering. Stress‐induced domain wall mobility was interpreted on the basis of a steep increase in acoustic loss immediately below the the Pc‐P1 transition 相似文献
58.
Danuta Kruk Evrim Umut Elzbieta Masiewicz Petr Hermann Hermann Scharfetter 《Molecular physics》2019,117(7-8):927-934
ABSTRACT1H spin–lattice relaxation studies of water solutions of Bismuth-ethylenediamine-tetraacetic acid (Bi-EDTA), Bismuth-ethylenediamine-tetrakis(methylenephosphonic) acid (Bi-EDTP), Bismuth-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (Bi-DOTA), Bismuth-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrakis(methylenephosphonic acid) (Bi-DOTP) and Bismuth-1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (Bi-DO3A) have been performed in order to compare Quadrupole Relaxation Enhancement (QRE) effects with Paramagnetic Relaxation Enhancement (PRE) from the perspective of exploiting the first one as a novel contrast mechanism for Magnetic Resonance Imaging (MRI). The selected compounds can be considered as 209Bi counterparts of Gd3+ complexes. The relaxation experiments have been performed in a broad frequency range of 5?kHz–30?MHz. The relaxation contribution associated with QRE has been extracted from the data and compared with PRE. Similarities and differences between the two effects have been discussed. 相似文献
59.
Marianna Gniadek Elzbieta Bak Zbigniew Stojek Mikolaj Donten 《Journal of Solid State Electrochemistry》2010,14(7):1303-1310
In this work, silver and gold–polyaniline composite materials were chemically synthesized at the nitrobenzene/water interface.
Aniline (monomer) was dissolved in nitrobenzene and the oxidizing agent (either silver (I) or gold (III)) was dissolved in
water. Metals, which were formed during the reaction were in nano- and microcrystalline forms and were partially embedded
in the polymer. The forms of gold and silver crystallites found in the synthesized composites differed significantly. The
rate of growth of the PANI-Ag and -Au composites and their morphologies depended on concentration of the reagents in both
phases. The average size of the gold crystals was smaller compared to silver and was in the range of 20–25 nm. The obtained
composite materials were characterized by cyclic voltammetry, scanning electron microscopy, and Raman spectroscopy. The pernigraniline
species of polyaniline dominated in the entire volume of the PANI-Au composite and in parts of the PANI-Ag material located
at the aqueous solution side, while partially oxidized emeraldine was the main component of PANI-Ag at the organic phase side. 相似文献
60.
Marta Z. Pacia Lukasz Mateuszuk Elzbieta Buczek Stefan Chlopicki Agnieszka Blazejczyk Joanna Wietrzyk Malgorzata Baranska Agnieszka Kaczor 《Journal of Raman spectroscopy : JRS》2016,47(11):1310-1317
Raman spectroscopy is a label free, versatile, simple and fast method that is increasingly used to detect pathological changes in the cells and tissues that could be useful in medical diagnostics. In this work, we tested the hypothesis that Raman spectroscopy may serve to detect endothelial dysfunction in murine models of lifestyle diseases associated with endothelial dysfunction. For that purpose, we analysed spectra from ex vivo vessels taken from mice with diabetes, hypertension and cancer metastasis. We extracted 50–70 random, single spectra, recorded in 0.2 s, from endothelium of mice with diseases and respective control animals and subjected them to hierarchical cluster analysis. Independently on the sample preparation protocol, very good discrimination was obtained for three‐tested murine models, i.e. diabetes, hypertension and cancer metastasis. Obtained sensitivity and specificity parameters were between 93% and 96% (with the exception of sensitivity in the diabetes model equalled to 88%). Our results show that single, random spectra of endothelium, recorded in less than a second, contains enough information on biochemical content of the endothelium to detect endothelial dysfunction. Furthermore, we demonstrated that biochemical profile of the endothelial dysfunction in diabetes, hypertension or cancer metastasis differs with a very high specificity and sensitivity. This conclusion can be a good starting point for the development of in vivo fast diagnostic methodology of endothelium in the future. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献