Satellite lines in the EPR spectra of nitroxide radicals: experimental data and DFT calculations

2014 ◽  
Vol 24 (5) ◽  
pp. 301-303 ◽  
Author(s):  
Natalia A. Chumakova ◽  
Vladimir I. Pergushov
Keyword(s):  
Experimental Data ◽  
Dft Calculations ◽  
Epr Spectra ◽  
Nitroxide Radicals

EPR spectra and defect states in glasses of the GexS100-x system

1982 ◽  
Vol 47 (7) ◽  
pp. 1787-1793 ◽  
Author(s):  
Miloslav Frumar ◽  
Gustáv Plesch ◽  
Eva Černošková ◽  
Václav Černý ◽  
Ladislav Tichý ◽  
...  
Keyword(s):  
Experimental Data ◽  
Epr Spectra ◽  
Defect States ◽  
Composition Region ◽  
Active Defect ◽  
Temperature Conditions ◽  
Defect Centres

Glasses of the GexS100-x system were studied in the region of 30 ⪬ x ⪬ 45. The concept of magnetically active defect centres was employed to account for the EPR spectra of pure samples as well as those doped with silver or iodine, prepared in different temperature conditions. In terms of this concept a consistent interpretation of the experimental data could be given for the composition region applied.

scholarly journals Influence of solid matrices on spectral features of metalloporphyrins

2018 ◽  
Vol 190 ◽  
pp. 03013
Author(s):  
Aleksandr Starukhin ◽  
Aleksander Gorski ◽  
Michal Kijak
Keyword(s):  
Experimental Data ◽  
Dft Calculations ◽  
Electronic State ◽  
Ground Electronic State ◽  
Spectral Features ◽  
Cryogenic Temperatures ◽  
Solid Matrices ◽  
Porphyrin Macrocycles

A way of simultaneously forming in the ground electronic state a planar, as well as two distorted forms was established for a set of metalloporphyrins in solid matrices at cryogenic temperatures. Experimental data together with results of theoretical DFT calculations are combined for analysis and assignment of possible types of distorted porphyrin macrocycles conformations.

Hyperconjugation In Trialkylboranes Shown By Indirect Nuclear Spin-Spin Coupling Constants. Experimental Data And Density Functional Theory (Dft) Calculations

2005 ◽  
Vol 60 (3) ◽  
pp. 259-264 ◽  
Author(s):  
Bernd Wrackmeyer ◽  
Oleg L. Tok
Keyword(s):  
Experimental Data ◽  
Dft Calculations ◽  
Density Functional ◽  
Calculated Data ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Functional Theory ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling ◽  
C Nmr

Trimethylborane (1), triethylborane (2), 1,3-dimethyl-1-boracyclopentane (3), 1-methyl-1- boracyclohexane (4), 9-methyl- and 9-ethyl-9-borabicyclo[3.1.1]nonane [5(Me) and 5(Et)], and 1- boraadamantane (6) were studied by 11B and 13C NMR spectroscopy with respect to coupling constants 1J(13C,11B) and 1J(13C,13C). Results of DFT calculations at the B3LYP/6-311+g(d,p) level of theory show satisfactory agreement with the experimental data. Hyperconjugation arising from C-C σ bonds adjacent to the tricoordinate boron atom is indicated, in particular for 1-boraadamantane (6), by the optimised calculated structures, and by the experimental and calculated data 1J(13C,13C). The calculated magnitude of 1J(13C,1H) for carbon atoms adjacent to boron becomes significantly smaller if the optimised structures suggest hyperconjugative effects arising from these C-H bonds

Well-defined nickel(II) tetrazole-saccharinate complex as homogeneous catalyst on the reduction of aldehydes: scope and reaction mechanism

2020 ◽  
Vol 92 (1) ◽  
pp. 151-166 ◽  
Author(s):  
Luís M. T. Frija ◽  
Bruno G. M. Rocha ◽  
Maxim L. Kuznetsov ◽  
Lília I. L. Cabral ◽  
M. Lurdes S. Cristiano ◽  
...  
Keyword(s):  
Experimental Data ◽  
Reaction Mechanism ◽  
Transition Metal ◽  
Dft Calculations ◽  
Microwave Power ◽  
Low Temperatures ◽  
Nickel Complex ◽  
Transition Metal Catalysts ◽  
Homogeneous Catalyst ◽  
First Time

AbstractA new (tetrazole-saccharin)nickel complex is shown to be a valuable catalyst for the hydrosilative reduction of aldehydes under microwave radiation at low temperatures. With typical 1 mol% content of the catalyst (microwave power range of 5–15 W) most reactions are complete within 30 min. The Ni(II)-catalyzed reduction of aldehydes, with a useful scope, was established for the first time by using this catalyst, and is competitive with the most effective transition-metal catalysts known for such transformation. The catalyst reveals tolerance to different functional groups, is air and moisture stable, and is readily prepared in straightforward synthetic steps. Supported by experimental data and DFT calculations, a plausible reaction mechanism involving the new catalytic system is outlined.

scholarly journals On the formation of gold nanoparticles from [AuIIICl4]− and a non-classical reduced polyoxomolybdate as an electron source: a quantum mechanical modelling and experimental study

2016 ◽  
Vol 40 (2) ◽  
pp. 1029-1038 ◽  
Author(s):  
Zhongling Lang ◽  
Isabel Maicas Gabas ◽  
Xavier López ◽  
Anna Clotet ◽  
Jesús M. de la Fuente ◽  
...  
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Gold Nanoparticles ◽  
Dft Calculations ◽  
Electron Source ◽  
Quantum Mechanical ◽  
Mechanical Modelling

DFT calculations and experimental data prove that the [Na{(MoV2O4)3(μ2-O)3(μ2-SO3)3(μ6-SO3)}2]15− POM is capable of completely reducing Au(iii) to Au(0).

MCD spectroscopy and TD-DFT calculations of a naphthalene-ring-bridged coplanar binuclear phthalocyanine dimer

2013 ◽  
Vol 17 (06n07) ◽  
pp. 489-500 ◽  
Author(s):  
John Mack ◽  
Xu Liang ◽  
Tatiana V. Dubinina ◽  
Larisa G. Tomilova ◽  
Tebello Nyokong ◽  
...  
Keyword(s):  
Experimental Data ◽  
Optical Properties ◽  
Electronic Structure ◽  
Dft Calculations ◽  
Singlet Oxygen ◽  
Magnetic Circular Dichroism ◽  
Basis Sets ◽  
Naphthalene Ring ◽  
B3lyp Functional ◽  
Td Dft

Magnetic circular dichroism (MCD) spectroscopy and TD-DFT calculations are used to analyze the electronic structure and optical properties of an alkyl-substituted naphthalene-ring-bridged coplanar binuclear phthalocyanine dimer. An analysis of the MCD spectrum of the naphthalene-ring-bridged dimer relative to those of benzene-bridged compounds reported previously, demonstrates that there is a significantly weaker interaction between the two phthalocyanine rings. TD-DFT results obtained using the B3LYP functional with 6–31G basis sets were found to be problematic. Closer agreement with the experimental data is obtained when the CAM-B3LYP functional is used instead. The naphthalene-ring-bridged compound is found to be unsuitable for use as a photosensitizer for the formation of singlet oxygen, because the ΦT values are negligible.

Combined analysis of chemical bonding in a CuIIdimer using QTAIM, Voronoi tessellation and Hirshfeld surface approaches

2015 ◽  
Vol 71 (5) ◽  
pp. 543-554 ◽  
Author(s):  
Anna V. Vologzhanina ◽  
Svitlana V. Kats ◽  
Larisa V. Penkova ◽  
Vadim A. Pavlenko ◽  
Nikolay N. Efimov ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Density Functional ◽  
Voronoi Tessellation ◽  
Quantitative Description ◽  
Hirshfeld Surface ◽  
Epr Spectra ◽  
Antiferromagnetic Coupling ◽  
X Ray Diffraction ◽  
Spin Distribution ◽  
X Ray

Interaction of 1-(1H-pyrazol-5-yl)ethanone oxime (H2PzOx) with copper(II) chloride in the presence of pyridine afforded a binuclear discrete [Cu2(HPzOx)2Cl2py2] complex, which was characterized by Fourier transform–IR and electron paramagnetic resonance (EPR) spectra, magnetochemistry and high-resolution X-ray diffraction experiments. Multipole refinement of X-ray diffraction data and density-functional theory (DFT) calculations of an isolated molecule allowed charge and spin distributions to be obtained for this compound. Magnetochemistry data, EPR spectra and DFT calculations of an isolated molecule show antiferromagnetic coupling between copper(II) ions. The spin distribution suggests an exchange pathwayviathe bridging pyrazole ring in the equatorial plane of the CuN4Cl coordination polyhedron, thus providing support for the classical superexchange mechanism; the calculated value of the magnetic coupling constant −2Jis equal to 220 cm−1, which compares well with the experimental value of 203 ± 2 cm−1. Chemical connectivity was derived by Bader's `quantum theory of atoms in molecules' and compared with Voronoi tessellation and Hirshfeld surface representations of crystal space. All methodologies gave a similar qualitative and semi-quantitative description of intra- and intermolecular connectivity.

Paramagnetic centers in graphite oxide according to EPR spectra and DFT calculations

2020 ◽  
Vol 754 ◽  
pp. 137722
Author(s):  
Andrey Kh Vorobiev ◽  
Dmitriy A. Astvatsaturov ◽  
Alexander V. Fionov ◽  
Natalia A. Chumakova
Keyword(s):  
Dft Calculations ◽  
Graphite Oxide ◽  
Epr Spectra ◽  
Paramagnetic Centers

scholarly journals Association of aescin with β- and γ-cyclodextrins studied by DFT calculations and spectroscopic methods

2017 ◽  
Vol 8 ◽  
pp. 348-357 ◽  
Author(s):  
Ana I Ramos ◽  
Pedro D Vaz ◽  
Susana S Braga ◽  
Artur M S Silva
Keyword(s):  
Experimental Data ◽  
Dft Calculations ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Chemical Shifts ◽  
Variation Method ◽  
Affinity Constant ◽  
Technical Solution ◽  
H Nmr ◽  
Natural Mixture

Background: Aescin, a natural mixture of saponins occurring in Aesculus hippocastanum, exhibits important flebotonic properties, being used in the treatment of chronic venous insufficiency in legs. The inclusion of aescin into cyclodextrins (CDs) is a technical solution for its incorporation into the textile of stockings, but details of the physicochemistry of these host–guest systems are lacking. This work investigates the inclusion of aescin into the cavities of two native cyclodextrins, β-CD and γ-CD. Results: The continuous variation method applied to aqueous-phase 1H nuclear magnetic resonance (1H NMR) has demonstrated that the preferred CD/aescin inclusion stoichiometries are 2:1 with β-CD and 1:1 with γ-CD. The affinity constant calculated for γ-CD·aescin was 894 M−1, while for 2β-CD·aescin it was estimated to be 715 M−1. Density functional theory (DFT) calculations on the interaction of aescin Ib with CDs show that an inclusion can indeed occur and it is further demonstrated that the wider cavity of γ-CD is more adequate to accommodate this large guest. ROESY spectroscopy is consistent with the formation of a complex in which the triterpenic moiety of aescin is included into the cavity of γ-CD. The higher stability of this geometry was confirmed by DFT. Furthermore, DFT calculations were applied to determine the chemical shifts of the protons H3 and H5 of the CDs in the optimised structures of the inclusion complexes. The calculated values are very similar to the experimental data, validating the approach made in this study by NMR. Conclusion: The combination of experimental data from aqueous-state NMR measurements and theoretical calculations has demonstrated that γ-CD is the most suitable host for aescin, although the inclusion also occurs with β-CD. The geometry of the γ-CD·aescin complex is characterised by the inclusion of the triterpene segment of aescin into the host cavity.

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