abstract
Elucidating the local environment of the hydrogen atoms is an important problem in materials science. Because (1)H spectra in solid-state nuclear magnetic resonance (NMR) suffer from low resolution due to homogeneous broadening, even under magic-angle spinning (MAS), information of chemical interest may only be obtained using certain high-resolution (1)H MAS techniques. (1)H Lee-Goldburg (LG) CRAMPS (Combined Rotation And Multiple-Pulse Spectroscopy) methods are particularly well suited for studying inorganic-organic hybrid materials, rich in (1)H nuclei. However, setting up CRAMPS experiments is time-consuming and not entirely trivial, facts that have discouraged their widespread use by materials scientists. To change this status quo, here we describe and discuss some important aspects of the experimental implementation of CRAMPS techniques based on LG decoupling schemes, such as FSLG (Frequency Switched), and windowed and windowless PMLG (Phase Modulated). In particular, we discuss the influence on the quality of the (1)H NMR spectra of the different parameters at play, for example LG (Lee-Goldburg) pulses, radio-frequency (rf) phase, frequency switching, and pulse imperfections, using glycine and adamantane as model compounds. The efficiency and robustness of the different LG-decoupling schemes is then illustrated on the following materials: organo-phosphorus ligand, N-(phosphonomethyl)iminodiacetic acid [H(4)pmida] [1], and inorganic-organic hybrid materials (C(4)H(12)N(2))[Ge(2)(pmida)(2)OH(2)].4H(2)O [II] and (C(2)H(5)NH(3))[Ti(H(1.5)PO(4))(PO(4))](2) H(2)O [111]. (C) 2008 Elsevier Inc. All rights reserved.
keywords
STATE NMR-SPECTROSCOPY; NUCLEAR-MAGNETIC-RESONANCE; ANGLE-SPINNING NMR; DIPOLAR-CORRELATION SPECTROSCOPY; MULTIPLE PULSE NMR; MAS C-13 NMR; CHEMICAL-SHIFT; THROUGH-BOND; HETERONUCLEAR DIPOLAR; POLARIZATION TRANSFER
subject category
Biochemistry & Molecular Biology; Physics; Spectroscopy
authors
Coelho, C; Rocha, J; Madhu, PK; Mafra, L
our authors
João Rocha
Full Professor
Luís Mafra
Principal Researcheracknowledgements
This research was supported by CICECO and University of Aveiro. We also thank Fundacao para a Ciencia e Tecnologia (FCT) for their general financial support and for the Post-Doc Grant SFRH/BPD/34136/2006 (to C. Coelho).