Recoupled separated-local-field experiments and applications to study intermediate-regime molecular motions

Autor(es)

Cobo, Marcio Fernando ^[1] ; Achilles, Anja ^[2] ; Reichert, Detlef ^[2] ; deAzevedo, Eduardo Ribeiro ^[1] ; Saalwaechter, Kay ^[2]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Fis Sao Carlos, BR-13560970 Sao Paulo - Brazil

^[2] Univ Halle Wittenberg, Inst Phys NMR, D-06120 Halle - Germany

• Tipo de documento: Artigo Científico
• Fonte: JOURNAL OF MAGNETIC RESONANCE; v. 221, p. 85-96, AUG 2012.
• Citações Web of Science: 15

Resumo

A specific separated-local-field NMR experiment, dubbed Dipolar-Chemical-Shift Correlation (DIPSHIFT) is frequently used to study molecular motions by probing reorientations through the changes in XH dipolar coupling and T-2. In systems where the coupling is weak or the reorientation angle is small, a recoupled variant of the DIPSHIFT experiment is applied, where the effective dipolar coupling is amplified by a REDOR-like pi-pulse train. However, a previously described constant-time variant of this experiment is not sensitive to the motion-induced T-2 effect, which precludes the observation of motions over a large range of rates ranging from hundreds of Hz to around a MHz. We present a DIPSHIFT implementation which amplifies the dipolar couplings and is still sensitive to T-2 effects. Spin dynamics simulations, analytical calculations and experiments demonstrate the sensitivity of the technique to molecular motions, and suggest the best experimental conditions to avoid imperfections. Furthermore, an in-depth theoretical analysis of the interplay of REDOR-like recoupling and proton decoupling based on Average-Hamiltonian Theory was performed, which allowed explaining the origin of many artifacts found in literature data. (C) 2012 Elsevier Inc. All rights reserved. (AU)

• Processo FAPESP: 08/11675-0 - Métodos de RMN para estudos de materiais com alta mobilidade molecular: aplicações a polímeros eletroluminescentes e nanocompostos de intercalação
• Beneficiário: Márcio Fernando Cobo
• Modalidade de apoio: Bolsas no Brasil - Doutorado Direto
• Processo FAPESP: 09/18354-8 - Dinâmica e estrutura de sistemas poliméricos estudados por ressonância magnética nuclear
• Beneficiário: Eduardo Ribeiro de Azevedo
• Modalidade de apoio: Auxílio à Pesquisa - Regular