abstract
The presence of two independent methylamine species in microporous aluminophosphate IST-1 (vertical bar(CH3NH2)(4)(CH3NH3+)(4) (OH-)(4)vertical bar[Al12P12O48]) has been shown previously by synchrotron powder X-ray diffraction, One of these species, [N(1)-C(1)], links to a six-coordinated framework Al-atom [Al(1)], while the other methylamine [N(2)-C(2)] is protonated and hydrogen-bonded to three O-atoms [O(1), O(2) and O(12)]. We revisit the structure of IST-1 and report the complete assignment of the H-1 NMR spectra by combining X-ray data and high-resolution heteronuclear/homonuclear solid-state NMR techniques based on frequency-switched Lee-Goldburg homonuclear decoupling and P-31-P-31 homonuclear recoupling. Careful analysis of the 2D H-1-X homonuclear correlation (X = H-1) and 2D heteronuclear correlation (X = C-13, P-31 and Al-27) spectra allowed the distinction of both methylamine species and the assignment of all P-31 and C-13 resonances. For the first time at a relatively high (9.4 T) magnetic field, symmetric doublet patterns have been observed in the C-13 spectra, caused by the influence of the N-14 second-order quadrupolar interaction. (c) 2006 Elsevier Inc. All rights reserved.
keywords
NUCLEAR-MAGNETIC-RESONANCE; SOLID-STATE NMR; HIGH-RESOLUTION NMR; MULTIPLE PULSE NMR; ANGLE-SPINNING NMR; INTEGER QUADRUPOLAR NUCLEI; PROTON CHEMICAL-SHIFTS; MAS NMR; LAYERED ALUMINOPHOSPHATE; STRUCTURAL INFORMATION
subject category
Biochemistry & Molecular Biology; Physics; Spectroscopy
authors
Mafra, L; Rocha, J; Fernandez, C; Paz, FAA
our authors
Filipe Alexandre Almeida Paz
Principal Researcher
João Rocha
Full Professor