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Sign-sensitive determination of heteronuclear dipolar coupling to spin-1 by selective decoupling
KTH, School of Chemical Science and Engineering (CHE), Chemistry.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.ORCID iD: 0000-0002-6524-1441
2012 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 137, no 23, 234902- p.Article in journal (Refereed) Published
Abstract [en]

This paper presents a theoretical and experimental study of nuclear magnetic resonance technique for sign-sensitive determination of the dipolar couplings of rare spins-1/2 to spin-1 with a strong quadrupolar interaction. The technique is based on low-power transition-selective single-quantum decoupling of spin-1 in the presence of high-power decoupling of abundant (proton) spins. Single-transition operator formalism is employed to calculate the time evolution of the density matrix in the presence of low-power irradiation of spin-1. Generally, the sign of dipolar coupling is unavailable from intrinsically symmetric shapes of dipolar-coupled spectra. Asymmetric dipolar multiplets, resulted from selective decoupling, reveal both the signs and magnitudes of the heteronuclear dipolar couplings. The approach is used to develop the experimental strategy for sign-sensitive measurements of short- and long-range heteronuclear dipolar couplings in highly ordered anisotropic samples. The technique is demonstrated for 13C-2H and 13C-14N spin pairs and for 13C- 2H2 three-spin system in liquid crystals.

Place, publisher, year, edition, pages
2012. Vol. 137, no 23, 234902- p.
Keyword [en]
liquid crystals, long-range order, nuclear magnetic resonance, quadrupole coupling, short-range order, spin systems
National Category
Chemical Sciences Physical Sciences
URN: urn:nbn:se:kth:diva-116657DOI: 10.1063/1.4771697ISI: 000312780300038ScopusID: 2-s2.0-84871956006OAI: diva2:600023
Swedish Research Council

QC 20130123

Available from: 2013-01-23 Created: 2013-01-22 Last updated: 2015-02-25Bibliographically approved
In thesis
1. Molecular Order and Dynamics in Nanostructured Materials by Solid-State NMR
Open this publication in new window or tab >>Molecular Order and Dynamics in Nanostructured Materials by Solid-State NMR
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Organic-inorganic nanostructured composites are nowadays integrated in the field of material science and technology. They are used as advanced materials directly or as precursors to novel composites with potential applications in optics, mechanics, energy, catalysis and medicine. Many properties of these complex materials depend on conformational rearrangements in their inherently dynamic organic parts. The focus of this thesis is on the study of the molecular mobility in ordered nanostructured composites and lyotropic mesophases and also on the development of relevant solid-state NMR methodologies.

In this work, a number of new experimental approaches were proposed for dipolar NMR spectroscopy for characterizing molecular dynamics with atomic-level resolution in complex solids and liquids. A new acquisition scheme for two-dimensional dipolar spectroscopy has been developed in order to expand the spectral window in the indirect dimension while using limited radio-frequency power. Selective decoupling of spin-1 nuclei for sign-sensitive determination of the heteronuclear dipolar coupling has been described. A new dipolar recoupling technique for rotating samples has been developed to achieve high dipolar resolution in a wide range of dipolar coupling strength. The experimental techniques developed herein are capable of delivering detailed model-independent information on molecular motional parameters that can be directly compared in different composites and their bulk analogs.

Solid-state NMR has been applied to study the local molecular dynamics of surfactant molecules in nanostructured organic-inorganic composites of different morphologies. On the basis of the experimental profiles of local order parameters, physical motional models for the confined surfactant molecules were put forward. In layered materials, a number of motional modes of surfactant molecules were observed depending on sample composition. These modes ranged from essentially immobilized rigid states to highly flexible and anisotropically tumbling states. In ordered hexagonal silica, highly dynamic conformationally disordered chains with restricted motion of the segments close to the head group have been found.

The results presented in this thesis provide a step towards the comprehensive characterization of the molecular states and understanding the great variability of the molecular assemblies in advanced nanostructured organic−inorganic composite materials.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. 54 p.
TRITA-CHE-Report, ISSN 1654-1081 ; 2015:7
mesoporous materials, organic-inorganic nanocomposites, surfactants, liquid crystals, MCM-41, clays, conformational dynamics, solid-state NMR, local field spectroscopy, dipolar coupling, dipolar recoupling, spin decoupling.
National Category
Physical Chemistry
Research subject
urn:nbn:se:kth:diva-160636 (URN)978-91-7595-424-0 (ISBN)
Public defence
2015-03-20, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)

QC 20150225

Available from: 2015-02-25 Created: 2015-02-25 Last updated: 2015-02-25Bibliographically approved

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Kharkov, Boris B.Dvinskikh, Sergey V.
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