Synthesis, NMR and ultraviolet spectroscopy of [10] (N6,9)-6-aminopurinophane; calculation of the chemical shifts in the [n](N6,9)-6-aminopurinophane series

1995 ◽  
Vol 73 (12) ◽  
pp. 2224-2232 ◽  
Author(s):  
Alfredo Capretta ◽  
Russell A. Bell
Keyword(s):  
Chemical Shifts ◽  
Variable Temperature ◽  
Bathochromic Shift ◽  
Ultraviolet Spectroscopy ◽  
Methylene Bridge ◽  
Nmr Study ◽  
Complete Assignment ◽  
Subsequent Cyclization ◽  
Semi Empirical ◽  
Hypochromic Effect

[10](N6,9)-6-Aminopurinophane was prepared via a Mitsunobu reaction involving 6-chloropurine and 10-azido-1-decanol. Reduction of the azido moiety to an amine allowed for subsequent cyclization to the cyclophane. N6-Nonyladenine, 9-nonyladenine, and N6,9-dinonyladenine were also prepared using the established chemistry. Heating the [10](N6,9)-6-aminopurinophane to 90 °C allowed for a complete assignment of the proton and carbon spectra, while cooling the sample to −77 °C revealed additional isomers likely due to the anti–syn isomerization about the N6—C6 bond. A variable temperature proton NMR study revealed a ΔGc≠ of 59.4 ± 5.5 kJ mol−1 associated with the interchange between the two major conformers. The ultraviolet spectra of the [n](N6,9)-6-aminopurinophane series show a bathochromic shift and a hypochromic effect in the transitions as the methylene chain length decreases (i.e., n = 10 to 9 to 8). The aminopurinophanes are used to assess the relative merits of a semi-empirical model that allows for the calculation of the chemical shifts of the methylene bridge protons. Keywords: synthesis of heterocyclophanes, variable temperature NMR, cyclophane conformational analysis, ultraviolet spectroscopy, calculation of chemical shift.

Reactions of vanadate with N,N- dimethylhydroxylamine: aqueous equilibria and the crystal structure of the uncharged oxygenbridged dimer of bis(N,N-dimethylhydroxamido)hydroxooxovanadate

1997 ◽  
Vol 75 (4) ◽  
pp. 429-440 ◽  
Author(s):  
Pradip C. Paul ◽  
Sarah J. Angus-Dunne ◽  
Raymond J. Batchelor ◽  
Frederick W.B. Einstein ◽  
Alan S. Tracey
Keyword(s):  
Crystal Structure ◽  
Chemical Exchange ◽  
Chemical Shifts ◽  
Variable Temperature ◽  
Crystalline Solid ◽  
Resonance Spectroscopy ◽  
Reaction Products ◽  
Orthorhombic Space Group ◽  
Ph Variation ◽  
Nmr Study

51V nuclear magnetic resonance spectroscopy has been utilized in the investigation of the reactions of vanadate with N,N-dimethylhydroxylamine in aqueous medium. The major components of the reaction products were mono- and bisliganded mononuclear vanadate compounds with 51V chemical shifts near −630 and −740 ppm, respectively. Variation of the concentration of the reactants enabled the determination of stoichiometry and formation constants of the products. The two major signals near −740 ppm were assigned to two stereoisomers of a bisligand product. The proton stoichiometrics and pKa values of the major products were determined from pH variation studies. A crystalline product of the type [V(O)(ONMe2)2]2O was isolated from the reaction of vanadate with dimethylhydroxylamine and its structure determined from X-ray diffraction studies. The compound possesses a dimeric oxo-bridge structure with a six-coordinate vanadium core. The arrangement about each vanadium may be described as approximately tetrahedral considering the center of the N—O bond in each dimethylhydroxamide ligand as one vertex. Hydrolysis of the crystalline solid in D2O provided two isomers that corresponded to the two bisligand products. A variable temperature 1H NMR study in D2O and 50% D2O/(CD3)2CO mixture revealed the existence of reasonably fast chemical exchange between the two predominant isomers. The nature of coordination of these and related compounds is discussed. Crystal structure of [V(O)(ONMe2)2]2O: orthorhombic, space group P22121;Z = 2;a = 7.0955(9) Å; b = 10.2313(12) Å; c = 11.5942(11) Å; V = 841.69 Å3; T = 213 K; RF = 0.021 for 1141 data (I0 ≥ 2.5σ(I0) ) and 137 variables. Keywords: bis(N,N-dimethylhydroxamido)hydroxooxovanadate, vanadate, dimethylhydroxylamine, vanadium NMR, aqueous equilibria, peroxovanadate.

scholarly journals Azapentalenes. XLIV.1H and13C-NMR study of mesoionic pyrazolo[1,2-a]pyrazoles

1997 ◽  
Vol 13 (2) ◽  
pp. 113-123 ◽  
Author(s):  
Rosa María Claramunt ◽  
Sviatoslav Trofimenko ◽  
Isabel Rozas ◽  
José Elguero
Keyword(s):  
Chemical Shifts ◽  
Additive Models ◽  
Coupling Constants ◽  
Pyrazole Derivatives ◽  
1H And13c Nmr ◽  
Nmr Study ◽  
Semi Empirical

The1H and13C chemical shifts as well as the1H–1H and1H–13C coupling constants of sixteen pyrazolo[1,2-a]pyrazole derivatives have been measured. The most relevant features are discussed using resonance forms and simple additive models. AM1 semi-empirical calculations have been carried out to provide a rationale for the NMR results.

scholarly journals DFT calculation and assignment of vibrational spectra of aryl and alkyl chlorophosphates

2014 ◽  
Vol 12 (2) ◽  
pp. 153-163
Author(s):  
Viktor Anishchenko ◽  
Vladimir Rybachenko ◽  
Konstantin Chotiy ◽  
Andrey Redko
Keyword(s):  
Vibrational Spectra ◽  
Basis Sets ◽  
Heavy Atoms ◽  
Wide Range ◽  
Complete Assignment ◽  
Key Factor ◽  
Polarization Functions ◽  
Experimental Values ◽  
Semi Empirical ◽  
Good Agreement

AbstractDFT calculations of vibrational spectra of chlorophosphates using wide range of basis sets and hybrid functionals were performed. Good agreement between calculated and experimental vibrational spectra was reached by the combination of non-empirical functional PBE0 with both middle and large basis sets. The frequencies of the stretching vibrations of the phosphate group calculated using semi-empirical functional B3LYP for all basis sets deviate significantly from the experimental values. The number of polarization functions on heavy atoms was shown to be a key factor for the calculation of vibrational frequencies of organophosphates. The importance of consideration of all the stable rotamers for a complete assignment of fundamental modes was shown.

19F High Magnetic Field NMR Study of β-ZrF4and CeF4:  From Spectra Reconstruction to Correlation between Fluorine Sites and19F Isotropic Chemical Shifts

2006 ◽  
Vol 45 (26) ◽  
pp. 10636-10641 ◽  
Author(s):  
C. Legein ◽  
F. Fayon ◽  
C. Martineau ◽  
M. Body ◽  
J.-Y. Buzaré ◽  
...  
Keyword(s):  
Magnetic Field ◽  
High Magnetic Field ◽  
Chemical Shifts ◽  
Nmr Study ◽  
Isotropic Chemical Shifts

scholarly journals NMR Behaviour of Molten 115Indium Chlorides

1984 ◽  
Vol 39 (11) ◽  
pp. 1112-1114
Author(s):  
Chiara Margheritis
Keyword(s):  
Chemical Shifts ◽  
Molten State ◽  
Nmr Study ◽  
Line Widths

An NMR study was made of the 115In nucleus in InCl. InCl2, InCl3 and in a mixture InCl3 + NaCl. Chemical shifts and line-widths as a function of temperature were recorded in the molten state for all samples except InCl3. As regards InCl2, NMR results gave little support to the generally held view that InCl2 is InI(InIIICl4) rather than (InIICl2)2.

scholarly journals Variable-Temperature Multinuclear Solid-State NMR Study of Oxide Ion Dynamics in Fluorite-Type Bismuth Vanadate and Phosphate Solid Electrolytes

2019 ◽  
Vol 31 (5) ◽  
pp. 1704-1714 ◽  
Author(s):  
Matthew T. Dunstan ◽  
David M. Halat ◽  
Matthew L. Tate ◽  
Ivana Radosavljevic Evans ◽  
Clare P. Grey
Keyword(s):  
Solid State ◽  
Solid State Nmr ◽  
Solid Electrolytes ◽  
Variable Temperature ◽  
Bismuth Vanadate ◽  
Ion Dynamics ◽  
Nmr Study ◽  
Fluorite Type ◽  
Oxide Ion
Sign in / Sign up

Export Citation Format

Share Document