scholarly journals Dipolar addition to cyclic vinyl sulfones leading to dual conformation tricycles

2013 ◽  
Vol 9 ◽  
pp. 1419-1425 ◽  
Author(s):  
Steven S Y Wong ◽  
Michael G Brant ◽  
Christopher Barr ◽  
Allen G Oliver ◽  
Jeremy E Wulff
Keyword(s):  
Dft Calculations ◽  
Nmr Spectra ◽  
Room Temperature ◽  
Synthetic Methodology ◽  
Nitrogen Center ◽  
Azomethine Imines ◽  
Nmr Methods

Dipolar addition of cyclic azomethine imines with cyclic vinyl sulfones gave rise to functionalized tricycles that exhibited fluxional behavior in solution at room temperature. The scope of the synthetic methodology was explored, and the origin of the fluxional behavior was probed by NMR methods together with DFT calculations. This behavior was ultimately attributed to stereochemical inversion at one of two nitrogen centers embedded in the tricyclic framework. Two tetracycles were also synthesized, and the degree of signal-broadening in the NMR spectra was found to depend on the presence of substitution next to the inverting nitrogen center.

Atomistic prediction on the configuration- and temperature-dependent dielectric constant of Be0.25Mg0.75O superlattice as a high-κ dielectric layer

2021 ◽  
Author(s):  
Gyuseung Han ◽  
In Won Yeu ◽  
Kun Hee Ye ◽  
Seung-Cheol Lee ◽  
Cheol Seong Hwang ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Dft Calculations ◽  
Bond Length ◽  
Dielectric Layer ◽  
Room Temperature ◽  
High Dielectric Constant ◽  
Temperature Dependent ◽  
High Dielectric

Through DFT calculations, a Be0.25Mg0.75O superlattice having long apical Be–O bond length is proposed to have a high bandgap (>7.3 eV) and high dielectric constant (∼18) at room temperature and above.

Predicting13C NMR Spectra by DFT Calculations

2003 ◽  
Vol 107 (46) ◽  
pp. 9964-9973 ◽  
Author(s):  
Alessandro Bagno ◽  
Federico Rastrelli ◽  
Giacomo Saielli
Keyword(s):  
Dft Calculations ◽  
Nmr Spectra

scholarly journals Elucidating Tricin-Lignin Structures: Assigning Correlations in HSQC Spectra of Monocot Lignins

Polymers ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 916 ◽  
Author(s):  
Wu Lan ◽  
Fengxia Yue ◽  
Jorge Rencoret ◽  
José del Río ◽  
Wout Boerjan ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Nmr Spectra ◽  
Model Compounds ◽  
Heteronuclear Correlation ◽  
Nmr Methods ◽  
Nuclear Magnetic ◽  
Lignin Structure

Tricin [5,7-dihydroxy-2-(4-hydroxy-3,5-dimethoxyphenyl)-4H-chromen-4-one] is a flavone that has been found to be incorporated in grass lignin polymers via 4′–O–β coupling. Herein, we investigated the tricin-lignin structure using nuclear magnetic resonance (NMR) methods by comparing the 1H–13C heteronuclear correlation (HSQC) NMR spectra of the isolated lignin with a series of dimeric and trimeric tricin-4′–O–β-ether model compounds. Results showed that the tricin moiety significantly affects the chemical shift of the Cβ/Hβ of 4′–O–β unit, producing peaks at around δC/δH 82.5–83.5/4.15–4.45, that differ from the Cβ/Hβ correlations from normal 4–O–β units formed solely by monolignols, and that have to date been unassigned.

A 19F nuclear magnetic resonance study of the conjugate Brönsted-Lewis superacid HSO3F-SbF5. Part 1

1999 ◽  
Vol 77 (11) ◽  
pp. 1869-1886 ◽  
Author(s):  
Dingliang Zhang ◽  
Markus Heubes ◽  
Gerhard Hägele ◽  
Friedhelm Aubke
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Nmr Spectra ◽  
Nuclear Magnetic Resonance Study ◽  
Magnetic Resonance Study ◽  
Formation Reaction ◽  
H Nmr ◽  
Acid Conjugate ◽  
Nmr Methods ◽  
Cis And Trans

The Brönsted-Lewis superacid HSO3F-SbF5 or "magic acid" is re-investigated by modern 19F NMR methods over a wide concentration range. The system is found to be considerably more complex than had been assumed previously. A total of 13 different anions are identified of which only five have previously been identified in magic acid. With increasing SbF5 contents the concentration of monomeric anions like [SbF6]-, [SbF5(SO3F)]-, cis- and trans-[SbF4(SO3F)2]-, and mer-[SbF3(SO3F)3]- gradually decreases. Except for [Sb2F11]-, which is present in very small concentrations only, the formation of oligomers involves exclusively μ-fluorosulfato bridges. In addition to donor (SO3F)- and acceptor (SbF5) complex formation to give [SbF5(SO3F)]- and possibly ligand redistribution, the solvolysis of SbF5 or SbF4(SO3F) in HSO3F appears to be the principal formation reaction for polyfluorosulfatofluoroantimonate(V) anions. In glass (NMR tubes) the solvolysis product HF is converted to the oxonium ion [H3O]+, which has previously been identified by 1H NMR and structurally characterized as [H3O][Sb2F11] by us.Key words: magic acid, conjugate superacid, fluorosulfuric acid, 19F NMR spectra.

scholarly journals Combining solid-state NMR spectroscopy with first-principles calculations – a guide to NMR crystallography

2016 ◽  
Vol 52 (45) ◽  
pp. 7186-7204 ◽  
Author(s):  
Sharon E. Ashbrook ◽  
David McKay
Keyword(s):  
Solid State ◽  
Nmr Spectroscopy ◽  
Dft Calculations ◽  
First Principles ◽  
Solid State Nmr ◽  
Nmr Spectra ◽  
First Principles Calculations ◽  
Recent Developments ◽  
Future Potential ◽  
Nmr Crystallography

DFT calculations are an important tool in assigning and interpreting NMR spectra of solids: we discuss recent developments and their future potential in the context of NMR crystallography.

scholarly journals Influence of molecular structure on helicoidal structure and NMR spectra of chiral liquid crystalline esters

2017 ◽  
Vol 66 (2) ◽  
pp. 25-35
Author(s):  
Anna Drzewicz ◽  
Marzena Tykarska ◽  
Mateusz Szala ◽  
Magdalena Żurowska
Keyword(s):  
Molecular Structure ◽  
Nmr Spectra ◽  
Liquid Crystalline ◽  
Room Temperature ◽  
Alkyl Chain ◽  
Light Reflection ◽  
13C Nmr Spectra ◽  
1H And 13C Nmr ◽  
Antiferroelectric Phase ◽  
Helicoidal Structure

Three-ring chiral liquid crystalline compounds, forming antiferroelectric phase, differing in the structure of alkyl chain and in the substitution of benzene ring by fluorine atoms were studied. The measurements of helical pitch, based on the selective light reflection phenomenon, were performed as well as 1H and 13C NMR spectra at room temperature were registered. The influence of molecular structure as well as the type of helicoidal structure on the chemical shift of signals coming from chiral center was observed. Keywords: liquid crystals, helicoidal structure, nuclear magnetic resonance, antiferroelectric phase

Assignment of the1H- and13C-NMR spectra of congested helicenes using two-dimensional NMR methods: Phenanthro[3′,4′:3,4]phenanthro[2,1-b]thiophene

1986 ◽  
Vol 23 (5) ◽  
pp. 1587-1593 ◽  
Author(s):  
Andrew S. Zektzer ◽  
John G. Stuart ◽  
Gary E. Martin ◽  
Raymond N. Castle
Keyword(s):  
Nmr Spectra ◽  
Two Dimensional ◽  
Nmr Methods

Predicting the NMR spectra of nucleotides by DFT calculations: cyclic uridine monophosphate

2008 ◽  
Vol 46 (6) ◽  
pp. 518-524 ◽  
Author(s):  
Alessandro Bagno ◽  
Federico Rastrelli ◽  
Giacomo Saielli
Keyword(s):  
Dft Calculations ◽  
Nmr Spectra ◽  
Uridine Monophosphate

31P and 195Pt solid-state NMR and DFT studies on platinum(i) and platinum(ii) complexes

2018 ◽  
Vol 47 (27) ◽  
pp. 8884-8891 ◽  
Author(s):  
Stefano Todisco ◽  
Giacomo Saielli ◽  
Vito Gallo ◽  
Mario Latronico ◽  
Antonino Rizzuti ◽  
...  
Keyword(s):  
Solid State ◽  
Dft Calculations ◽  
Solid State Nmr ◽  
Nmr Spectra ◽  
Pulse Sequence ◽  
Spin Orbit ◽  
Dft Studies ◽  
Relativistic Dft

31P and 195Pt solid state NMR spectra on anti-[(PHCy)ClPt(μ-PCy2)2Pt(PHCy)Cl] (3) and [(PHCy2)Pt(μ-PCy2)(κ2P,O-μ-POCy2)Pt(PHCy2)] (Pt–Pt) (4) were recorded under CP/MAS conditions (31P) or with the CP/CPMG pulse sequence (195Pt) and compared to data obtained by relativistic DFT calculations of 31P and 195Pt CS tensors and isotropic shielding at the ZORA Spin Orbit level.

scholarly journals Atran-analoge Verbindungen des Typs / Atrane Analogous Compounds of the Type

1984 ◽  
Vol 39 (3) ◽  
pp. 341-351 ◽  
Author(s):  
Joseph Grobe ◽  
Gerald Henkel ◽  
Bernt Krebs ◽  
Nikolaos Voulgarakis
Keyword(s):  
Structure Analysis ◽  
Nmr Spectra ◽  
Room Temperature ◽  
Trigonal Bipyramid ◽  
Angular Distortion ◽  
Type I ◽  
Tetrahedral Coordination ◽  
Cage Compounds ◽  
X Ray ◽  
H Nmr

Heterocyclic cage compounds of type I (compounds 8-10) have been prepared by condensation reactions of 1,2,2-trifunctional disilanes Me(R)XSiSiMeX2 (R = Me, Ph, OEt; X = NMe2, OEt) with triethanolamine using the “Dilution Principle”. The starting compounds are obtained by Si-Me cleavage of Si2Me6 with acetylchloride/AlCl3 followed by either aminolysis with HNMe2 or alcoholysis with EtOH. 1H NMR spectra indicate N→Si(1) intraction with the more acidic Si atom in 8 and 9. This result is proved by the X-ray structure analysis of 8 (monoclinic, P21/c; a = 7,088(2), b = 15,070(4), c = 12,701(4) Å, β = 104,96(2) at -130 °C, Z = 4); the Si(1)···N distance is found to be 2,768 Å , connected with a significant angular distortion of the tetrahedral coordination around Si(1) towards a trigonal bipyramid. In compound 10, too, N→Si(1) coordination is observed at room temperature in spite of almost equal acidity for both Si atoms. This can be explained by the preference of 5- over 6-membered chelating ring systems. At higher temperatures the 1H NMR spectra show a fluctuation of the N-donor between the two Si centres.

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