13C pNMR of "crumple zone" Cu(II) isophthalate metal-organic frameworks.

Abstract

NMR spectroscopy of paramagnetic materials (pNMR) has the potential to provide great structural insight, but many challenges remain in interpreting the spectra in detail. This work presents a study of a series of structurally analogous metal-organic frameworks (MOFs) based on 5-substituted isophthalate linkers and Cu(II) paddlewheel dimers, of interest owing to their "crumple zone" structural rearrangement on dehydration/rehydration. 13C MAS NMR spectra reveal a wide variation in the observed resonance position for chemically similar C species in the different MOFs but, despite this, resonances are overlapped in several cases. However, by considering a combination of the integration of quantitative spectra, the resonance position as a function of temperature and T1 relaxation measurements, the spectra can be fully assigned. It is also demonstrated that the prototypical MOF in this series, STAM-1, displays a crumple zone rearrangement on dehydration, similar to the well-characterised 5-ethoxyisophthalate MOF (STAM-17-OEt) although, while the materials have similar local C environments, dehydrated STAM-1 exhibits less long-range order.

• Authors: Daniel M Dawson, Charlotte E F Sansome, Lauren N McHugh, Matthew J McPherson, Laura J McCormick McPherson, Russell E Morris, Sharon E Ashbrook
• Journal: Solid state nuclear magnetic resonance (Solid State Nucl Magn Reson) Vol. 101 Pg. 44-50 (Sep 2019) ISSN: 1527-3326 [Electronic] Netherlands
• PMID: 31112890 (Publication Type: Journal Article)
• Copyright: Copyright © 2019 Elsevier Inc. All rights reserved.