Structural study of sulfamic acid at 4.2 K by ENDOR-detected NMR

Reuveni, Amikam; Marcellus, Daniel H.; Kwiram, Alvin L.

doi:10.1063/1.440860

Cited by 22 publications

(10 citation statements)

References 33 publications

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“…Since A contains the influence of the charges of the second hydrogen bond partner one should expect a proportionality of the form A K Z and therefore a ratio of A(Cl)/A(O) = 17/8 = 2.1. The agreement with the ratio of the A values found experimentally is a support for the assumptions mentioned in context with (13) thus demonstrating the applicability of (14) to the case of 0 -D ... C1 hydrogen bonds.…”

Section: Efg Tensors and Structure Of The Cl-ho Unit In The Nphase Osupporting

confidence: 80%

“…Comparing the value A = 571.8 kHz for 0 -D ... 0 bonds given in [13] with the value 1142 kHz appearing in (14) one finds a ratio of about 2.0. Since A contains the influence of the charges of the second hydrogen bond partner one should expect a proportionality of the form A K Z and therefore a ratio of A(Cl)/A(O) = 17/8 = 2.1.…”

Section: Efg Tensors and Structure Of The Cl-ho Unit In The Nphase Omentioning

confidence: 90%

See 1 more Smart Citation

Static and Dynamic Behaviour of the Crystal Water Molecules in the Normal Phase of Deuterated Betaine Calciumchloride Dihydrate

Hacker

Holzer

Michel

et al. 1994

Physica Status Solidi (b)

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The static and dynamic behaviour of the deuterated crystal water molecules in the normal (N) phase of betaine calciumchloride dihydrate (BCCD) single crystals is investigated by means of quadrupolar perturbed 'H NMR. The temperature dependence both of the 'H NMR spectra and of the *H spinlattice relaxation time TI can be interpreted consistently by a thermally activated exchange process of the deuterons within the D,O molecule. At 170 K, under the condition of slow exchange, the electric field gradient (EFG) tensors of both deuterium sites are determined. From their principal axes and the quadrupole coupling constants information is derived about the structure of the CI-D,O unit in BCCD in comparison with previous X-ray studies Das statische und dynamische Verhalten der deuterierten Kristallwassermolekule in der Normal-(N-) Phase von Betaincalciumchlorid-Dihydrat (BCCD) wird mit Hilfe der quadrupolar gestorten 'H-NMR an Einkristallen untersucht. Die Temperaturabhangigkeit sowohl der 'H-NMR-Spektren wie auch der 'H-Spin-Gitter-Relaxationszeit TI laBt sich konsistent durch einen thermisch aktivierten AustauschprozeB der Deuteronen innerhalb des Kristallwassermolekuls beschreiben. Die elektrischen Feldgradiententensoren (EFG) an beiden Deuteriumplatzen werden bei 170 K unter der Bedingung eines langsamen Austausches bestimmt. Aus den Richtungen ihrer Hauptachsen und den Quadrupolkopplungskonstanten werden Aussagen iiber die Struktur der C1-D,O-Einheit in BCCD abgeleitet und mit den Ergebnissen friiherer Rontgenstrukturuntersuchungen verglichen.

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Section: Efg Tensors and Structure Of The Cl-ho Unit In The Nphase Osupporting

confidence: 80%

Section: Efg Tensors and Structure Of The Cl-ho Unit In The Nphase Omentioning

confidence: 90%

Static and Dynamic Behaviour of the Crystal Water Molecules in the Normal Phase of Deuterated Betaine Calciumchloride Dihydrate

Hacker

Holzer

Michel

et al. 1994

Physica Status Solidi (b)

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“…In Figure 3, original amino H a orientations are designated by the dashed bonds and the solid bonds are the proposed H a (or 2 D) orientations. Previous nuclear quadrupole resonance studies have established a correlation between the direction of maximum quadrupole coupling in N- 2 D and the bond direction35. Quadrupole coupling tensors from the 2 D ENDOR study of copper-triglycine sulfate were therefore used to locate the amino group 2 D atoms.…”

Section: Resultsmentioning

confidence: 99%

Aspects of Structure and Bonding in Copper−Amino Acid Complexes Revealed by Single-Crystal EPR/ENDOR Spectroscopy and Density Functional Calculations

2009

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This work deduces from a series of well defined copper-doped amino acid crystals, relationships between structural features of the copper complexes and ligand-bound proton hyperfine parameters. These were established by combining results from electron paramagnetic resonance (EPR)/electron-nuclear double resonance (ENDOR) studies, crystallography and were further assessed by quantum mechanical (QM) calculations. A detailed evaluation of previous studies on Cu2+-doped into α-glycine, triglycine sulfate, α-glycylglycine and l-alanine crystals reveal correlations between geometric features of the copper sites and proton hyperfine couplings from amino bound and carbon bound hydrogens. Experimental variations in proton isotropic hyperfine coupling values (aiso) could be fit to cosine-square dependences on dihedral angles, namely, for Cα-bound hydrogens, aiso = −1.09 + 8.21cos2θ MHz, and for amino hydrogens, aiso = −6.16 + 4.15cos2φ MHz. For the Cα hydrogens, this dependency suggests a hyperconjugative-like mechanism for transfer of spin density into the hydrogen 1s-orbital. In the course of this work, it was also necessary to reanalyze the ENDOR measurements from Cu2+-doped α-glycine since the initial study determined the 14N coupling parameters without holding its nuclear quadrupole tensor traceless. This new treatment of the data was needed to correctly align the 14N hyperfine tensor principal directions in the molecular complex. In order to provide a theoretical basis for the coupling variations, QM calculations performed at the Density Functional Theory (DFT) level were used to compute the proton hyperfine tensors in the four crystal complexes as well as in a geometry-optimized Cu2+(glycine)2 model. These theoretical calculations confirmed systematic changes in couplings with dihedral angles, but greatly overestimated the experimental geometric sensitivity to the amino hydrogen isotropic coupling.

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“…Upon warming to 300 K, radical II decays and radical III is detected where loss of the -proton from the 3-position is detected. Studies of deuterium [30], nitrogen [27] 23 Na [31], and chlorine-35 [32] hyperfine coupling constants, as well as their?coupling constants have been reported. It was also found [28] that radical I was stable at 300 K; demonstrating that upon decay of radical I, radical III is an end-product of the decay of radical II.…”

Section: Organic Radicals In Organic Host Crystalsmentioning

confidence: 99%

“…Two nonequivalent crystal sites are detected for radical III and the -couplings for all sites have been determined. For example the relationship between deuterium quadrupole constants and the N-D and D…O bond lengths in a perdeuterates sulphamic acid (ND 3 SO 3 ) single crystal were reported [30]. Secondary radical products stable at room temperature have been studied to examine whether the free radical position in the crystal is the same as that of the undamaged molecules.…”

Section: Organic Radicals In Organic Host Crystalsmentioning

confidence: 99%

Endor Spectroscopy

Kispert

Piekara-Sady

Handbook of Applied Solid State Spectroscopy

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To understand what electron nuclear double resonance (ENDOR) transitions are, let us consider the energy levels of a system containing one unpaired electron (S = ½) and one nuclear spin (I = ½), as in a hydrogen atom. Since the electron spin and nuclear spin can each be oriented with or against the external magnetic field, there are four possible energy levels as shown in Figure 4.1. The two electron spin eigenfunctions are denoted by e and e , whereas the two nuclear spin wavefunctions are denoted n and n . In the presence of a large external applied field, the selection rule in electron paramagnetic resonance (EPR) is that the electron flips (changes directions) but the nuclear spin does not flip in an EPR transition. Thus, in Figure 4.1, an EPR transition will occur between energy levels 1 and 4 and a second EPR transitions will occur between energy levels 2 and 3. The intensity of the transition between energy levels 1 and 4 will depend on the population differences of these two energy levels. If one then applies a nuclear frequency to the system, which corresponds to either the energy difference between levels 4 and 3 or the difference between lines 2 and 1, one will induce nuclear spin flip that will change the populations in energy levels 4 and 1, respectively. This changes the intensity of the observed EPR signal. This change in intensity is referred to as the ENDOR response. Figure 4.1 Energy diagram for S = 1/2 and I = 1/2.

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Structural study of sulfamic acid at 4.2 K by ENDOR-detected NMR

Cited by 22 publications

References 33 publications

Static and Dynamic Behaviour of the Crystal Water Molecules in the Normal Phase of Deuterated Betaine Calciumchloride Dihydrate

Static and Dynamic Behaviour of the Crystal Water Molecules in the Normal Phase of Deuterated Betaine Calciumchloride Dihydrate

Aspects of Structure and Bonding in Copper−Amino Acid Complexes Revealed by Single-Crystal EPR/ENDOR Spectroscopy and Density Functional Calculations

Endor Spectroscopy

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