The NMR-WEBLAB: An internet approach to NMR lineshape analysis

Abstract

The nuclear magnetic resonance (NMR) WEBLAB is described, providing an interactive tool for analyzing NMR spectra of solids and anisotropic liquids to elucidate their molecular dynamics. It is a collection of programs freely available over the Internet at http://www.mpip-mainz.mpg.de/weblab4O/ that permit the interpretation of one-dimensional NMR spectra in the case of motions occurring on a cone and of two-dimensional exchange NMR data for discrete jumps. The programs are described in detail and analytical formulae for the averaged interaction tensor components that govern the spectra in the fast motional limit are derived in an appendix. To facilitate the validation of the results obtained from the WEBLAB, we present examples for two-and three-site jumps and demonstrate how WEBLAB can be utilized for analyzing more complex motions around more than one axis as met, e.g., in poly(diethysiloxane), where experimental data are available.

Cooperative Molecular Motion within a Self‐Assembled Liquid‐Crystalline Molecular Wire: The Case of a TEG‐Substituted Perylenediimide Disc

“…We modeled this case by considering rapid angular fluctuations that are described by a Gaussian distribution of rotational angles with variance s. The corresponding motionally averaged CSA lineshapes and DDC sideband spectra are readily calculated. [22] With s < AE 408, the asymmetry of the 13 C CSA tensor h CS = (d xx Àd yy )/(d zz Àd iso ) is only slightly reduced, whereas the magnitude for the CSA is maintained (d CS = d zz Àd iso ). On the other hand, the dipolar coupling tensor changes from an axially symmetric tensor (h D = 0) in the static case to a non-axial tensor (h D = 0.46) accompanied by a reduction of the absolute magnitude for the dipolar coupling by a factor of 1.47 (see the Supporting Information, Figure S2 for details).…”

Two‐Dimensional Double‐Quantum 2H NMR Spectroscopy in the Solid State under OMAS Conditions: Correlating 2H Chemical Shifts with Quasistatic Line Shapes

“…These static line shapes can be reintroduced into MAS experiments by slightly misadjusting the magic angle and observing the time signal in a rotor-synchronised fashion, that is, by sampling the data points in intervals of Dt 2 = t R . It can be seen by considering Equation (4) that, by means of rotor-synchronised data acquisition, the effect of the quadrupole coupling on the NMR signal can be restricted to Equation (9).…”

“…The success of 2 H NMR spectroscopy is based on the detailed information on molecular orientation, reorientation, and/or motional processes provided by characteristic 2 H line shapes. [9] As 2 H is a spin-1 nucleus, the 2 H resonance is governed by the quadrupolar interaction with typical couplings d Q of d Q /2p % 130 kHz in organic solids. [1,10] Due to its low natural abundance, 2 H virtually always needs to be isotopically enriched in the samples (i.e., the samples need to be deuterated).…”

Kooperative Molekülbewegungen innerhalb eines selbstorganisierten flüssigkristallinen molekularen Drahtes am Beispiel eines TEG‐ substituierten Perylendiimids

“…Die zugehörigen bewegungsgemittelten CSA-Linienformen und DDC-Seitenbandenspektren können leicht berechnet werden. [22] Mit s < AE 408 ist die Asymmetrie des 13 C-CSA-Tensors [h CS = (d xx Àd yy )/(d zz Àd iso )] nur wenig reduziert, während die Anisotropie der chemischen Verschiebung gleich bleibt (d CS = d zz Àd iso ). Auf der anderen Seite ändert sich der dipolare Kopplungstensor von einem axial symmetrischen Tensor (h D = 0) zu einem nicht axialen Tensor (h D = 0.46), was mit einer Reduktion der Stärke der dipolaren Kopplung um einem Faktor von 1.47 einhergeht (siehe Abbildung 2 in den Hintergrundinformationen).…”