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991.
Oleksandr P. Dacenko Olga V. Manoylenko Pavel K. Mykhailiuk Dmitriy M. Volochnyuk Oleg V. Shishkin 《合成通讯》2013,43(7):981-992
An improved synthesis of Boc-monoprotected 5- and 6-amino-2-azanorbornanes is reported. The synthetic scheme consists of five steps and allows multigram quantities of the title compounds to be obtained. The regio- and stereochemistries of the products are established by two-dimensional NMR experiments.
992.
Jiri Kosina Ivan Viden Olga Pokorska Herman Van Langenhove 《International journal of environmental analytical chemistry》2013,93(6):637-649
This article describes a method for preparation of low concentration gas standard mixtures of biogenic volatile organic compounds (BVOCs) emitted primarily by plants. A set of 10 plant volatiles including α-pinene, β-pinene, 3-carene, linalool, methyl salicylate, α-cedrene, β-caryophyllene, β-farnesene, aromadendrene and α-humulene was used in the study. Gas standard mixture of these compounds was generated using a capillary diffusion system (CDS). Diffusion coefficient (D) and saturation vapour pressure (p s) data of these compounds were calculated from experimentally determined gas chromatographic retention indices (RI) and empirical relationships between D and p s versus RI. A comparison of the calculated and measured concentrations of investigated compounds has proved that designed CDS can be successfully used for the proper quantification of BVOCs. 相似文献
993.
Tyler T. Clikeman Dr. S. H. M. Deng Dr. Stanislav Avdoshenko Dr. Xue‐Bin Wang Dr. Alexey A. Popov Prof. Steven H. Strauss Dr. Olga V. Boltalina 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(45):15404-15409
Hexasubstituted fullerenes with the skew pentagonal pyramid (SPP) addition pattern are predominantly formed in many types of reactions and represent important and versatile building blocks for supramolecular chemistry, biomedical and optoelectronic applications. Regioselective synthesis and characterization of the new SPP derivative, C60(CF3)4(CN)H, in this work led to the experimental identification of the new family of “superhalogen fullerene radicals”, species with the gas‐phase electron affinity higher than that of the most electronegative halogens, F and Cl. Low‐temperature photoelectron spectroscopy and DFT studies of different C60X5 radicals reveal a profound effect of X groups on their electron affinities (EA), which vary from 2.76 eV (X=CH3) to 4.47 eV (X=CN). The measured gas‐phase EA of the newly synthesized C60(CF3)4CN equals 4.28 (1) eV, which is about 1 eV higher than the EA of Cl atom. An observed remarkable stability of C60(CF3)4CN? in solution under ambient conditions opens new venues for design of air‐stable molecular complexes and salts for supramolecular structures of electroactive functional materials. 相似文献
994.
Dr. Yao Zhao Dr. Julie A. Woods Dr. Nicola J. Farrer Kim S. Robinson Jitka Pracharova Dr. Jana Kasparkova Olga Novakova Huilin Li Dr. Luca Salassa Dr. Ana M. Pizarro Dr. Guy J. Clarkson Dr. Lijiang Song Prof. Dr. Viktor Brabec Prof. Dr. Peter J. Sadler 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(29):9578-9591
Platinum diam(m)ine complexes, such as cisplatin, are successful anticancer drugs, but suffer from problems of resistance and side‐effects. Photoactivatable PtIV prodrugs offer the potential of targeted drug release and new mechanisms of action. We report the synthesis, X‐ray crystallographic and spectroscopic properties of photoactivatable diazido complexes trans,trans,trans‐[Pt(N3)2(OH)2(MA)(Py)] ( 1 ; MA=methylamine, Py=pyridine) and trans,trans,trans‐[Pt(N3)2(OH)2(MA)(Tz)] ( 2 ; Tz=thiazole), and interpret their photophysical properties by TD‐DFT modelling. The orientation of the azido groups is highly dependent on H bonding and crystal packing, as shown by polymorphs 1 p and 1 q . Complexes 1 and 2 are stable in the dark towards hydrolysis and glutathione reduction, but undergo rapid photoreduction with UVA or blue light with minimal amine photodissociation. They are over an order of magnitude more potent towards HaCaT keratinocytes, A2780 ovarian, and OE19 oesophageal carcinoma cells than cisplatin and show particular potency towards cisplatin‐resistant human ovarian cancer cells (A2780cis). Analysis of binding to calf‐thymus (CT), plasmids, oligonucleotide DNA and individual nucleotides reveals that photoactivated 1 and 2 form both mono‐ and bifunctional DNA lesions, with preference for G and C, similar to transplatin, but with significantly larger unwinding angles and a higher percentage of interstrand cross‐links, with evidence for DNA strand cross‐linking further supported by a comet assay. DNA lesions of 1 and 2 on a 50 bp duplex were not recognised by HMGB1 protein, in contrast to cisplatin‐type lesions. The photo‐induced platination reactions of DNA by 1 and 2 show similarities with the products of the dark reactions of the PtII compounds trans‐[PtCl2(MA)(Py)] ( 5 ) and trans‐[PtCl2(MA)(Tz)] ( 6 ). Following photoactivation, complex 2 reacted most rapidly with CT DNA, followed by 1 , whereas the dark reactions of 5 and 6 with DNA were comparatively slow. Complexes 1 and 2 can therefore give rapid potent photocytotoxicity and novel DNA lesions in cancer cells, with no activity in the absence of irradiation. 相似文献
995.
996.
Yulia A. Zakharova Nataliya N. Smirnova Olga G. Zamyshlyayeva 《Journal of Thermal Analysis and Calorimetry》2013,112(3):1489-1498
The temperature dependences of heat capacity of copolymers on the basis of perfluorinated germanium hydrides have been measured using an adiabatic vacuum calorimeter over the temperature range from 6 K to the final temperature of their stability for the first time. Thus, the physical transformations were detected and their thermodynamic characteristics were estimated. The experimental results were used to calculate the standard thermodynamic functions, namely heat capacity, enthalpy, entropy and Gibbs function over the range from T → 0 to the final temperature stability of copolymers. The standard entropy of formation of the under study copolymers at T = 298.15 K was calculated. The obtained results were compared with corresponding data for hyperbranching perfluor polyphenylenegermaniums with other structures. Some conclusions about dependences of the thermodynamic polymers properties versus their structures were made. 相似文献
997.
Molecular structure of formanilide is determined by gas-phase electron diffraction (GED) augmented by quantum chemical calculations (B3LYP/cc-pVTZ and MP2/cc-pVTZ) and literature microwave (MW) data. The combined GED and MW data are well reproduced for the mixture of trans and cis isomers with the relative abundance of 59 ± 5 and 41 ± 5 %, respectively, at T = 410 K. The trans isomer (C s symmetry) is planar, while the cis isomer (C 1 symmetry) has the twisted structure with the amide group rotated by 36.7 ± 2.7° with respect to the phenyl ring. In accord with theoretical calculations, the amide bond –NH–C(O)– is planar in trans formanilide and a somewhat nonplanar in cis isomer. Accurate structural parameters were obtained by a simultaneous fit of the rotational constants reported in the literature and GED intensities obtained in this study. The N–C(O) and N–CPh bond dissociation energies in formanilide are calculated using Gaussian-4 method. It is revealed that the strength of N–C(O) bond in formanilide is 50 kJ/mol less than that in benzamide. On the contrary, the strength of adjacent bond (N–CPh) increases by 35 kJ/mol compared to aniline. It is rather unexpectedly that the bond strength weakening does not result in the bond elongating, and vice versa. 相似文献
998.
The two-dimensional potential energy scan shows that the pseudo-trans conformer of 1,5-dinitrobiuret (DNB) is the most stable form of isolated molecule, while the pseudo-cis conformer is about 7.5 kJ/mol higher in energy. Thus, the structure of gaseous DNB is different from that in crystal state, where the molecules have pseudo-cis conformation. The value of enthalpy of formation of gaseous DNB (?257 ± 5 kJ/mol) is calculated from isodesmic reactions using G4 energies. Combining this value with empirically estimated enthalpy of sublimation, the enthalpy of formation of crystal DNB is predicted to be ?415 ± 15 kJ/mol. The bond dissociation enthalpies are calculated for all bonds. The energy of the weakest N–NO2 bonds is equal to 190–200 kJ/mol. Similar calculations were carried out for biuret. The gaseous biuret exists predominantly in the pseudo-trans form. The calculated enthalpy of formation of gaseous biuret agrees well with the experimental one. The correlation of calculated bond energies with corresponding bond distances and electron density is discussed for biuret and DNB. 相似文献
999.
Olga V. Zalomaeva Nataliya V. Maksimchuk Andrey M. Chibiryaev Konstantin A. Kovalenko Vladimir P. Fedin Bair S. Balzhinimaev 《Journal of Energy Chemistry》2013,22(1):130-135
Catalytic properties of the metal-organic framework Cr-MIL-101 in solvent-free cycloaddition of CO2 to epoxides to produce cyclic carbonates using tetrabutylammonium bromide as co-catalyst have been explored under mild reaction conditions (8 bar CO2, 25 0C). Styrene and propylene carbonates were formed with high yields (95% and 82%, respectively). Catalytic performance of Cr-MIL-101 was compared with other MOFs: Fe-MIL-101, Zn-MOF-5 and HKUST-1. The catalytic properties of different quaternary ammonium bromides, Cr-MIL-101 as well as PW12/Cr-MIL-101 composite material have been assessed in oxidative carboxylation of styrene in the presence of both tert-butyl hydroperoxide and H2O2 as oxidants at 8–100 bar CO2 and 25–80 0C with selectivity to styrene carbonate up to 44% at 57% substrate conversion. 相似文献
1000.
Prof. Kevin D. Belfield Dr. Mykhailo V. Bondar Hafeez S. Haniff Dr. Ivan A. Mikhailov Dr. Gheorghe Luchita Dr. Olga V. Przhonska 《Chemphyschem》2013,14(15):3532-3542
The synthesis, linear photophysical, two‐photon absorption (2PA), femtosecond transient absorption, and superfluorescence properties of a new symmetrical squaraine derivative ( 1 ) are reported. Steady‐state linear spectral and photochemical properties, fluorescence lifetimes, and excitation anisotropy of 1 were investigated in various organic solvents. High fluorescence quantum yields (≈0.7) and very high photostability (photodecomposition quantum yields ≈10?6–10?8) were observed. An open‐aperture Z‐scan method was used to obtain 2PA spectra of 1 over a broad spectral range (maximum 2PA cross section ≈1000 GM). Excited‐state absorption (ESA) and gain was observed by femtosecond transient absorption spectroscopy, in which both reached a maximum at approximately 500 fs. Squaraine 1 exhibits efficient superfluorescence. The quantum chemical study of 1 revealed the simulated vibronic nature of the 1PA and 2PA spectra were in good agreement with experimental data; this may provide the ability to predict potential advanced photonic materials. 相似文献