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91.
Structural Chemistry - DNA and RNA base-pairs are the most important systems containing multiple hydrogen bonds. Characterizing the energy of individual intermolecular interactions in such systems... 相似文献
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Dr. Olga A. Stasyuk Prof. Dr. Miquel Solà Prof. Dr. Marcel Swart Prof. Dr. Célia Fonseca Guerra Prof. Dr. Tadeusz Marek Krygowski Prof. Dr. Halina Szatylowicz 《Chemphyschem》2020,21(18):2112-2126
For many years, non-covalently bonded complexes of nucleobases have attracted considerable interest. However, there is a lack of information about the nature of hydrogen bonding between nucleobases when the bonding is affected by metal coordination to one of the nucleobases, and how the individual hydrogen bonds and aromaticity of nucleobases respond to the presence of the metal cation. Here we report a DFT computational study of nucleobase pairs interacting with alkali metal cations. The metal cations contribute to the stabilization of the base pairs to varying degrees depending on their position. The energy decomposition analysis revealed that the nature of bonding between nucleobases does not change much upon metal coordination. The effect of the cations on individual hydrogen bonds were described by changes in VDD charges on frontier atoms, H-bond length, bond energy from NBO analysis, and the delocalization index from QTAIM calculations. The aromaticity changes were determined by a HOMA index. 相似文献
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The 14N relaxation time of pyrrole in cyclohexane, carbon tetrachloride and pentafluororyridine solution has been determined at a number of temperatures through a line-shape analysis of the imido proton pmr signal of pyrrole (scalar relaxation of the second kind). The viscosity of pyrrole in the same solvents has also been measured. The results are discussed in terms of solvent effects on the association equilibria of pyrrole. 相似文献
96.
Thin poly(methyl methacrylate) (PMMA) films were prepared by a solution casting on different supports (glass and aluminium plates with different gloss). UV-irradiation (λ = 254 nm) was used for polymer modification. Surface properties of PMMA were studied by contact angle measurements, attenuated total reflection infrared spectroscopy and optical microscopy. It was found that support type has no influence on surface properties of virgin PMMA, however, the changes in these properties were observed during UV modification of polymer film. The most efficient photochemical reactions appeared in sample placed on the rough Al, whereas the smallest effect was observed in polymer on the glass. 相似文献
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JPC – Journal of Planar Chromatography – Modern TLC - High-performance thin-layer chromatography (HPTLC) on silica gel 60 F254 TLC plates, with ethyl acetate-methanol-acetone-acetic... 相似文献
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Marika Żyła‐Karwowska Dr. Halina Zhylitskaya Dr. Joanna Cybińska Prof. Tadeusz Lis Prof. Piotr J. Chmielewski Prof. Marcin Stępień 《Angewandte Chemie (International ed. in English)》2016,55(47):14658-14662
A hexapyrrolohexaazacoronene derivative containing 37 fused rings, the largest such system to date, was obtained from a naphthalenomonoimide–pyrrole hybrid in a concise and efficient synthesis. This large heterocycle is electron‐deficient and shows extended redox activity, spanning at least 13 oxidation levels, but is otherwise chemically stable. Radial expansion of the π system creates a chromophore characterized by strong fluorescence and solvatochromism in the neutral state, and strong near‐infrared absorption in the charged states. Additionally, the enlarged and ruffled aromatic surface supports a unique self‐assembly mode in the crystal, leading to the formation of highly solvated organic clathrates. 相似文献
100.
Complex formation between vanadium(III) and several imidazole carboxylic derivatives (urocanic acid, imidazole-4-carboxylic and imidazole-4,5-dicarboxylic acid) was studied using pH-potentiometric and spectroscopic (UV–Vis absorption and fluorescence) methods. The results show that urocanic acid is a weak ligand in aqueous solution and hydrolysis of vanadium(III) effectively competes with the complexation processes. Imidazole mono and di-carboxylate are relatively stronger donor (N,O) ligands and are able to prevent, to some degree, the hydrolysis processes. The main complex species in the vanadium(III)–imidazole-4,5-dicarboxylic acid system is the dinuclear μ-oxo bridged V2OL2 species. 相似文献