Solid‐State ¹⁷O NMR Spectroscopy of Paramagnetic Coordination Compounds

Abstract

We demonstrate that high-quality solid-state 17O (I = 5/2) NMR spectra can be successfully obtained for paramagnetic coordination compounds in which oxygen atoms are directly bonded to the paramagnetic metal centers. For complexes containing V(III) (S = 1), Cu(II) (S = 1/2), and Mn(III) (S = 2) metal centers, the 17O isotropic paramagnetic shifts were found to span a range of more than 10000 ppm. In several cases, high-resolution 17O NMR spectra were recorded under very fast magic-angle spinning (MAS) conditions at 21.1 T. Quantum chemical computations using density functional theory (DFT) qualitatively reproduced the experimental 17O hyperfine shift tensors.

Direct detection and characterization of bioinorganic peroxo moieties in a vanadium complex by 17O solid-state NMR and density functional theory

“…Enzymatic peroxo intermediates, detected in several Fe and Mn enzymes are paramagnetic. Kong et al have recently demonstrated that high-resolution 17 O spectra can be obtained from oxygen atoms coordinated to paramagnetic metal centers [22]. These findings, combined with the present work, which illustrates the strength of the integrated 17 O SSNMR and DFT approach, suggest that investigations of enzymatic peroxido complexes and their biomimetic counterparts can provide invaluable information regarding the nature of the metal-peroxido bond in peroxo intermediates.…”

“…DFT calculations on bioinorganic complexes can help to correlate the experimental NMR parameters with local coordination environment and geometry of the observed nuclei [40–43]. 17 O NMR spectra of oxygen atoms directly bonded to paramagnetic metal ions have been reported by Kong et al [22] This work is particularly relevant in the context of enzymatic peroxo intermediates which typically have the peroxido moiety is ligated to a paramagnetic metal cofactor. DFT calculations qualitatively predicted the paramagnetic chemical shift tensors, demonstrating the feasibility of 17 O NMR studies and quantum chemical calculations for investigation of metalloprotein active sites.…”

“…The broadening arises from the second-order quadrupolar interaction, which dominates 17 O NMR spectra, and which cannot be completely removed by magic angle spinning (MAS). Despite these challenges, 17 O solid-state NMR (SSNMR) spectra have been reported in several small organic and biological molecules,[14–18] in oxygen containing transition metal coordination complexes [19–22], as well as in protein-ligand complexes, such as hemoglobin- and myoglobin- 17 O 2 states [23], [C 17 O]myoglobin [24], egg-white avidin-[ 17 O 2 ]biotin and ovo-transferrin-Al III -[ 17 O 4 ]oxalate [25]. In several reports, it has been demonstrated that data acquisition at high magnetic fields alleviates the low-sensitivity and resolution loss from anisotropic nuclear interactions in 17 O spectra, since the magnitude of second order quadrupolar interaction diminishes with increasing applied magnetic field [18].…”

Unleashing the Potential of 17O NMR Spectroscopy Using Mechanochemistry

“…[7b, 16,17] The potential of mechanochemistry is not limited to carboxylic acids and metal hydroxides. Indeed, we found that other strategic reagents like B(OH)3 (used for the synthesis of glasses, ceramics and hybrid materials) and boronic acids (used for the synthesis of covalent-organic frameworks -COFs -and coordination polymers) can also be successfully labelled in 17 O by BM in less than 1 hour, by engaging stoichiometric quantities of H2 17 O and applying a protocol similar to the one described in Scheme 1 (see supporting information).…”

A solid-state17O NMR study of platinum-carboxylate complexes: carboplatin and oxaliplatin

“…6 The most recent advances in solid-state 17 O NMR include studies of pharmaceuticals 7,8 and paramagnetic coordination compounds. 9 Another significant recent development is the application of dynamic nuclear polarization (DNP) to drastically boost the sensitivity of solid-state 17 O NMR experiments. [10][11][12] In the present work, we use solid-state 17 O NMR to study two platinum anticancer drugs: carboplatin and oxaliplatin (Scheme 1).…”