<sup>15</sup>N NMR chemical shifts of NH‐pyrazoles in the solid state and in solution at low temperature

Aguilar‐Parrilla, Francisco; Männle, Ferdinand; Limbach, Hans−Heinrich; Elguero, José; Jagerovic, Nadine

doi:10.1002/mrc.1260321110

Cited by 41 publications

(23 citation statements)

References 12 publications

(3 reference statements)

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“…The temperature of the samples increased due to friction effect of the fast MAS, 9 which was estimated to be 333 K at 70 kHz MAS from Pb(NO 3 ) 2 temperature calibration. 10 The 1 H RF field strength for the excitation p/2 pulse (1.29 ls) was 200 kHz. The 1 H chemical shift was referenced to the peak of silicon rubber and set to 0.12 ppm from TMS.…”

Section: Methodsmentioning

confidence: 99%

Difference in the structures of alanine tri‐ and tetra‐peptides with antiparallel β‐sheet assessed by X‐ray diffraction, solid‐state NMR and chemical shift calculations by GIPAW

et al. 2013

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Alanine oligomers provide a key structure for silk fibers from spider and wild silkworms.We report on structural analysis of L-alanyl-L-alanyl-L-alanyl-L-alanine (Ala)4 with anti-parallel (AP) β-structures using X-ray and solid-state NMR. All of the Ala residues in the (Ala)4 are in equivalent positions, whereas for alanine trimer (Ala)3 there are two alternative locations in a unit cell as reported previously (Fawcett and Camerman, Acta Cryst., 1975, 31, 658-665). (Ala)4 with AP β-structure is more stable than AP-(Ala)3 due to formation of the stronger hydrogen bonds. The intermolecular structure of (Ala)4 is also different from polyalanine fiber structure, indicating that the interchain arrangement of AP β-structure changes with increasing alanine sequencelength. Furthermore the precise (1)H positions, which are usually inaccesible by X-ray diffraction method, are determined by high resolution (1)H solid state NMR combined with the chemical shift calculations by the gauge-including projector augmented wave method.

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Section: Methodsmentioning

confidence: 99%

Difference in the structures of alanine tri‐ and tetra‐peptides with antiparallel β‐sheet assessed by X‐ray diffraction, solid‐state NMR and chemical shift calculations by GIPAW

et al. 2013

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“…Nuclear magnetic resonance of 15 N as well as 'H and C, and also nuclear quadrupole resonance of 2 H and l4 N are very useful for the study of N-H -• -N hydrogen bonding, as pointed out in [2], and a number of experimental and theoretical studies were conducted on the imidazole family and related materials in solution [13,14] and in the solid state [12,[15][16][17][18][19][20][21][22][23][24][25][26][27][28].…”

Section: H Imentioning

confidence: 99%

Effect of Intermolecular Hydrogen Bonding on the Nuclear Quadrupole Interaction in Imidazole and its Derivatives as Studied by ab initio Molecular Orbital Calculations

Nakamura

Masui

Ueda

2000

Zeitschrift Für Naturforschung A

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Ab initio Hartree-Fock molecular orbital calculations were applied to the crystalline imidazole and its derivatives in order to examine systematically the effect of possible N-H---N type hydrogen bonding on the nuclear quadrupole interaction parameters in these materials. The nitrogen quadrupole coupling constant (QCC) and the asymmetry parameter (r?) of the electric field gradient (EFG) were found to depend strongly on the size of the molecular clusters, from single molecule, to dimer, trimer and to the infinite molecular chain, i.e., crystalline state, implying that the intermolecular N-H -N hydrogen bond affects significantly the electronic structure of imidazole molecule. A certain correlation between the QCC of l4 N and the N-H bond distance R was also found and interpreted on the basis of the molecular orbital theory. However, we found that the value of the calculated EFG at the hydrogen position of the N-H group, or the corresponding QCC value of 2 H, increases drastically as /C* when R is shorter than about 0.1 nm, due probably to the inapplicability of the Gaussian basis sets to the very short chemical bond as revealed in the actual imidazole derivatives. We suggested that the observed N-H distances in imidazole derivatives should be re-examined.

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“…To the best of our knowledge, this is the first report of a 15 N NMR study on a graphene-based material. The spectrum in Figure 3a shows a broad peak centred at approximately 190 p.p.m., which can be assigned to pyrazole moieties 34 . Because of 13 C mAs ssnmR spectra with a π/2-pulse excitation of 13 C-and 15 n-labelled RGo, (a) without and (b) with dipolar dephasing by 13 C-15 n REDoR during a period of 1.6 ms. (c) The difference spectrum of a and b. note that the vertical scale in c is magnified five times, compared with that of a and b.…”

mentioning

confidence: 99%

Chemical structures of hydrazine-treated graphene oxide and generation of aromatic nitrogen doping

et al. 2012

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Chemically modified graphene platelets, produced via graphene oxide, show great promise in a variety of applications due to their electrical, thermal, barrier and mechanical properties. understanding the chemical structures of chemically modified graphene platelets will aid in the understanding of their physical properties and facilitate development of chemically modified graphene platelet chemistry. Here we use 13 C and 15 n solid-state nuclear magnetic resonance spectroscopy and X-ray photoelectron spectroscopy to study the chemical structure of 15 nlabelled hydrazine-treated 13 C-labelled graphite oxide and unlabelled hydrazine-treated graphene oxide, respectively. These experiments suggest that hydrazine treatment of graphene oxide causes insertion of an aromatic n 2 moiety in a five-membered ring at the platelet edges and also restores graphitic networks on the basal planes. Furthermore, density-functional theory calculations support the formation of such n 2 structures at the edges and help to elucidate the influence of the aromatic n 2 moieties on the electronic structure of chemically modified graphene platelets.

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¹⁵N NMR chemical shifts of NH‐pyrazoles in the solid state and in solution at low temperature

Cited by 41 publications

References 12 publications

Difference in the structures of alanine tri‐ and tetra‐peptides with antiparallel β‐sheet assessed by X‐ray diffraction, solid‐state NMR and chemical shift calculations by GIPAW

Difference in the structures of alanine tri‐ and tetra‐peptides with antiparallel β‐sheet assessed by X‐ray diffraction, solid‐state NMR and chemical shift calculations by GIPAW

Effect of Intermolecular Hydrogen Bonding on the Nuclear Quadrupole Interaction in Imidazole and its Derivatives as Studied by ab initio Molecular Orbital Calculations

Chemical structures of hydrazine-treated graphene oxide and generation of aromatic nitrogen doping

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15N NMR chemical shifts of NH‐pyrazoles in the solid state and in solution at low temperature

Cited by 41 publications

References 12 publications

Difference in the structures of alanine tri‐ and tetra‐peptides with antiparallel β‐sheet assessed by X‐ray diffraction, solid‐state NMR and chemical shift calculations by GIPAW

Difference in the structures of alanine tri‐ and tetra‐peptides with antiparallel β‐sheet assessed by X‐ray diffraction, solid‐state NMR and chemical shift calculations by GIPAW

Effect of Intermolecular Hydrogen Bonding on the Nuclear Quadrupole Interaction in Imidazole and its Derivatives as Studied by ab initio Molecular Orbital Calculations

Chemical structures of hydrazine-treated graphene oxide and generation of aromatic nitrogen doping

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¹⁵N NMR chemical shifts of NH‐pyrazoles in the solid state and in solution at low temperature