Following the oxidation state of organosulfur compounds with NMR: Experimental data versus DFT calculations and database-powered NMR prediction

2020 ◽  
Vol 1202 ◽  
pp. 127346 ◽  
Author(s):  
P.W. Szafrański ◽  
M.E. Trybula ◽  
P. Kasza ◽  
M.T. Cegła
Keyword(s):  
Experimental Data ◽  
Dft Calculations ◽  
Oxidation State ◽  
Organosulfur Compounds ◽  
Nmr Prediction

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.

scholarly journals Bimetallic Cooperativity with a 2-Phosphinoimidazole-Derived Pd(II) Dimer Enables Naphthalene Synthesis via dimeric Pd(III) Catalysis

2020 ◽  
Author(s):  
Chloe C. Ence ◽  
S. Hadi Nazari ◽  
Mariur Rodriguez Moreno ◽  
Manase F. Matu ◽  
Samantha G. Kulka ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Dft Calculations ◽  
Oxidation State ◽  
Methyl Ketone ◽  
Methyl Ketones ◽  
Mechanistic Studies ◽  
High Oxidation State ◽  
Pd Catalysts ◽  
Silver Triflate ◽  
High Oxidation

We report the synthesis of bimetallic Pd(I) and Pd(II) complexes scaffolded on bidentate 2-phosphinoimidazole ligands. These complexes display unique catalytic activity and enable the expeditious formation of 1,3-disubstituted naphthalenes via an unprecedented coupling of aryl iodides and methyl ketones in the presence of silver triflate. Excellent substrate scope for naphthalene formation is also demonstrated. Mechanistic studies suggest that the transformation proceeds via Pd-catalyzed arylation of a methyl ketone, followed by cyclization with a second equivalent of ketone. Importantly, this ketone arylation processes occurs under oxidizing conditions, suggesting involvement of higher oxidation state dimeric Pd catalysts. Based on experiments and DFT calculations, we propose a mechanism involving high oxidation state Pd(III) bimetallic catalysis. These new bimetallic complexes possess reactivity that is not seen with monometallic Pd catalysts and we confirm the importance of the palladium catalyst for both arylation and cyclization for naphthalene formation.

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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