¹³C pNMR of “crumple zone” Cu(II) isophthalate metal-organic frameworks

Dawson, Daniel M., Sansome, Charlotte E.F., McHugh, Lauren N., McPherson, Matthew J., McCormick McPherson, Laura J., Morris, Russell E. and Ashbrook, Sharon E. (2019) ¹³C pNMR of “crumple zone” Cu(II) isophthalate metal-organic frameworks. Solid State Nuclear Magnetic Resonance, 101, 44-50. (doi:10.1016/j.ssnmr.2019.05.005).

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.

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Contributors

Author: Laura J. McCormick McPherson

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