We present a strategy for predicting the unusual 1 H and 13 C shifts in NMR spectra of paramagnetic bisoximato copper(II) complexes using DFT. We demonstrate good agreement with experimental measurements, although 1 H-13 C correlation spectra show that a combined experimental and theoretical approach remains necessary for full assignment.In recent years, paramagnetic NMR (or "pNMR") has developed greatly, with systems from metalloproteins 1 (dilute, isolated spins) to metal-organic frameworks 2-4 (denser networks of potentially coupled spins) and metal oxides 5 (very dense networks of highly coupled spins) being studied. For dilute spins, the NMR conditions can be selected such that the signal from nuclei near the paramagnetic centre is "invisible" owing to rapid relaxation and only the longer-range throughspace pseudocontact shifts are observed. 1 These are generally on the order of a few ppm and occur over distances such that the unpaired electron can be treated as a point spin, resulting in a simple 1/r 3 relationship with the shift. For dense spin networks such as transition metal oxides, it may be possible to assign the NMR spectra by analysis of bonding pathways (via oxygen). 5 However, in the intermediate regime, including materials such as catalytically-active transition metal complexes and metal-organic frameworks (MOFs), both the through-bond Fermi contact and through-space pseudocontact interactions affect the observed NMR spectrum and assignment can be both nontrivial and counterintuitive. 2,6-9 For example, in the 13 C NMR spectrum of the MOF HKUST-1 (Cu3btc2, btc = benzene-1,3,5-tricarboxylate), 10 the broadest resonance, shifted most by paramagnetic interactions, is not the carboxylate C (separated from Cu 2+ by just two bonds), but rather the adjacent quaternary C (three bonds from Cu). This assignment was confirmed using the relatively costly and timeconsuming approach of specific 13 C labelling in conjunction with 1 H-13 C cross polarisation (CP) NMR, which is generally inefficient for paramagnetic materials. 2 It would, therefore, be desirable to have a more general assignment method that does not rely on the development of bespoke synthetic pathways for efficient isotopic enrichment. Owing to the rapid MAS rates (necessitating the use of small rotors with, consequently, small sample volumes) required for highresolution pNMR spectra, sensitivity is inherently low and it would, therefore, also be advantageous to be able to predict shifts prior to the experimental measurement, particularly as resonances can be several hundred ppm away from their typical diamagnetic range.Periodic density functional theory (DFT) calculations have enjoyed great success in solid-state NMR, allowing the optimisation of experimental structures to an energy minimum and the subsequent calculation of highly accurate NMR parameters [11][12][13] However, pNMR DFT calculations are still in their relative infancy, particularly for periodic solids. The field is more advanced for molecular calculations, which have successfull...
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