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991.
Konstantin V. Domasevitch 《Acta Crystallographica. Section C, Structural Chemistry》2014,70(3):272-276
In catena‐poly[[dichloridocobalt(II)]‐μ‐(1,1′‐dimethyl‐4,4′‐bipyrazole‐κ2N2:N2′)], [CoCl2(C8H10N4)]n, (1), two independent bipyrazole ligands (Me2bpz) are situated across centres of inversion and in tetraaquabis(1,1′‐dimethyl‐4,4′‐bipyrazole‐κN2)cobalt(II) dichloride–1,1′‐dimethyl‐4,4′‐bipyrazole–water (1/2/2), [Co(C8H10N4)2(H2O)4]Cl2·2C8H10N4·2H2O, (2), the Co2+ cation lies on an inversion centre and two noncoordinated Me2bpz molecules are also situated across centres of inversion. The compounds are the first complexes involving N,N′‐disubstituted 4,4′‐bipyrazole tectons. They reveal a relatively poor coordination ability of the ligand, resulting in a Co–pyrazole coordination ratio of only 1:2. Compound (1) adopts a zigzag chain structure with bitopic Me2bpz links between tetrahedral CoII ions. Interchain interactions occur by means of very weak C—H...Cl hydrogen bonding. Complex (2) comprises discrete octahedral trans‐[Co(Me2bpz)2(H2O)4]2+ cations formed by monodentate Me2bpz ligands. Two equivalents of additional noncoordinated Me2bpz tectons are important as `second‐sphere ligands' connecting the cations by means of relatively strong O—H...N hydrogen bonding with generation of doubly interpenetrated pcu (α‐Po) frameworks. Noncoordinated chloride anions and solvent water molecules afford hydrogen‐bonded [(Cl−)2(H2O)2] rhombs, which establish topological links between the above frameworks, producing a rare eight‐coordinated uninodal net of {424.5.63} ( ilc ) topology. 相似文献
992.
In our attempt to synthesize a halogenated analog of green fluorescent protein (GFP) chromophore, we discovered a simple and efficient synthetic strategy to the derivatives of oxazole-4-carboxylic acid substituted at positions 2 and 5. The method allows for introduction of different aryl substituents at the position 5, aryl or alkyl substituents at position 2 of oxazole, and gives access not only to free carboxyl at position 4, but also to a range of its amide derivatives. The advantages of the synthetic strategy presented are availability of precursors, good yields, and avoiding palladium coupling and metalation procedures. The synthesized compounds fluoresce in visible region with quantum yields up to 0.82. We believe that 5-aryl-4-carboxyoxazole is a promising core for creation of new fluorescent dyes. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file. 相似文献
993.
Irina Odinets Natalya Vinogradova Pavel Petrovskii Konstantin Lyssenko Tatyana Mastryukova 《Phosphorus, sulfur, and silicon and the related elements》2013,188(6-7):1787-1791
The facile synthetic route to 5- and 6-membered 3-cyano-2-oxo-1,2-thiaphosphacyclanes and 6-cyano-2-oxa-10-oxa(thia)-phosphabicyclo [4.4.0]-decane-1-oxides was elaborated via intramolecular S-alkylation in a series of y -haloalkylsubstituted thiophosphorylacetonitriles. The compounds were used to prepare novel P(III)-containing bidentate ligands with definite stereochemistry. Diastereomeric transformations among 2-oxo-1,2-thiaphosphinanes were found and the mechanism of such transformations is suggested. 相似文献
994.
Tatyana A. Mastryukova Inga M. Aladzheva Olga V. Bykhovskaya Dmitrii I. Lobanov Alexey M. Nemeryuk Konstantin A. Lyssenko 《Phosphorus, sulfur, and silicon and the related elements》2013,188(6-7):1701-1704
A novel convenient "one-pot" synthesis of 2-oxo-1,2 u 5 -azaphosphacyclanes 1 and 1,2 u 4 -azaphosphacyclanium salts 2 via intramolecular N-alkylation of y -halogenalkyl-substituted iminophosphoryl compounds 3 has been developed. The common nature of the reaction of intramolecular cyclization of iminophosphoryl compounds having an alkoxy group at the phosphorus atom and the Arbuzov reaction has been established. 相似文献
995.
Konstantin A. Popov Alexander M. Polozov 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4)
Abstract Diazo esters (la,b) react with trialkyl phosphates (2a–c) in the presence of BF3.OEt2 to give the corresponding phosphates (3a–e) in 42–58 % yields. The competed intra/intermolecular protonation in the reaction of la with dimethyl hydrogen phosphite leads to phosphonate. 4,and phosphite 5. 相似文献
996.
Simon Weidmann Gediminas Mikutis Konstantin Barylyuk Renato Zenobi 《Journal of the American Society for Mass Spectrometry》2013,24(9):1396-1404
In high-mass matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), the accessible m/z range is limited by the detector used. Therefore, special high-mass detectors based on ion conversion dynodes (ICDs) have been developed. Recently, we have found that mass bias may exist when such ICD detectors are used [Weidmann et al., Anal. Chem. 85(6), 3425–3432 (2013)]. In this contribution, the mass-dependent response of an ICD detector was systematically studied, the response factors for proteins with molecular weights from 35.9 to 129.9 kDa were determined, and the reasons for mass bias were identified. Compared with commonly employed microchannel plate detectors, we found that the mass discrimination is less pronounced, although ions with higher masses are weakly favored when using an ICD detector. The relative response was found to depend on the laser power used for MALDI; low-mass ions are discriminated against with higher laser power. The effect of mutual ion suppression in dependence of the proteins used and their molar ratio is shown. Mixtures consisting of protein oligomers that only differ in mass show less mass discrimination than mixtures consisting of different proteins with similar masses. Furthermore, mass discrimination increases for molar ratios far from 1. Finally, we present clear guidelines that help to choose the experimental parameters such that the response measured matches the actual molar fraction as closely as possible. Figure
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997.
998.
Vladimir Frankevich Konstantin Barylyuk Konstantin Chingin Robert Nieckarz Prof. Dr. Renato Zenobi 《Chemphyschem》2013,14(5):929-935
Green fluorescent protein (GFP) was ionized by native electrospray ionization and trapped for many seconds in high vacuum, allowing fluorescence emission to be measured as a probe of its biological function, to answer the question whether GFP exists in the native form in the gas phase or not. Although a narrow charge‐state distribution, a collision cross‐section very close to that expected for correctly folded GFP, and a large stability against dissociation all support a near‐native gas‐phase structure, no fluorescence emission was observed. The loss of the native form is attributed to the absence of residual water in the gas phase, which normally stabilizes the para‐hydroxybenzylidene imidazolone chromophore of GFP. 相似文献
999.
Andrey N. Pravdivtsev Prof. Alexandra V. Yurkovskaya Prof. Hans‐Martin Vieth Dr. Konstantin L. Ivanov Prof. Robert Kaptein 《Chemphyschem》2013,14(14):3327-3331
Various hyperpolarization methods are able to enhance the sensitivity of nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI) by several orders of magnitude. Among these methods are para‐hydrogen‐induced polarization (PHIP) and signal amplification by reversible exchange (SABRE), which exploit the strong nuclear alignment of para‐hydrogen. Several SABRE experiments have been reported but, so far, it has not been possible to account for the experimentally observed sign and magnetic‐field dependence of substrate polarization. Herein, we present an analysis based on level anti‐crossings (LACs), which provides a complete understanding of the SABRE effect. The field‐dependence of both net and anti‐phase polarization is measured for several ligands, which can be reproduced by the theory. The similar SABRE field‐dependence for different ligands is also explained. In general, the LAC concept allows complex spin dynamics to be unraveled, and is crucial for optimizing the performance of novel hyperpolarization methods in NMR and MRI techniques. 相似文献
1000.
Anna S. Degtyarenko Konstantin V. Domasevitch 《Acta Crystallographica. Section C, Structural Chemistry》2013,69(3):219-224
New complexes containing the 1,4‐bis(pyridazin‐4‐yl)benzene ligand, namely diaquatetrakis[1,4‐bis(pyridazin‐4‐yl)benzene‐κN2]cadmium(II) hexaiodidodicadmate(II), [Cd(C14H10N4)4(H2O)2][Cd2I6], (I), and poly[[μ‐1,4‐bis(pyridazin‐4‐yl)benzene‐κ2N2:N2′]bis(μ‐thiocyanato‐κ2N:S)cadmium(II)], [Cd(NCS)2(C14H10N4)]n, (II), demonstrate the adaptability of the coordination geometries towards the demands of slipped π–π stacking interactions between the extended organic ligands. In (I), the discrete cationic [Cd—N = 2.408 (3) and 2.413 (3) Å] and anionic [Cd—I = 2.709 (2)–3.1201 (14) Å] entities are situated across centres of inversion. The cations associate via complementary O—H...N2′ hydrogen bonding [O...N = 2.748 (4) and 2.765 (4) Å] and extensive triple π–π stacking interactions between pairs of pyridazine and phenylene rings [centroid–centroid distances (CCD) = 3.782 (4)–4.286 (3) Å] to yield two‐dimensional square nets. The [Cd2I6]2− anions reside in channels generated by packing of successive nets. In (II), the CdII cation lies on a centre of inversion and the ligand is situated across a centre of inversion. A two‐dimensional coordination array is formed by crosslinking of linear [Cd(μ‐NCS)2]n chains [Cd—N = 2.3004 (14) Å and Cd—S = 2.7804 (5) Å] with N2:N2′‐bidentate organic bridges [Cd—N = 2.3893 (12) Å], which generate π–π stacks by double‐slipped interactions between phenylene and pyridazine rings [CCD = 3.721 (2) Å]. 相似文献