Department of Chemistry & Biomolecular Sciences, University of Ottawa
We report on recent advances from our laboratory in the framework of the following two broad research themes: (i) non-covalent electrophilic interactions studied via solid-state NMR spectroscopy and (ii) dynamics and equivalence from J splittings associated with pairs of quadrupolar nuclei in solids.
The hydrogen bond is widely recognized as a ubiquitous non-covalent interaction. More recently, a number of related interactions, named after the electrophilic site, have taken on increased prominence in chemistry, biochemistry, materials science, and crystal engineering. For example, the halogen bond results from the donation of electrons from a Lewis base (Y) towards the electron-deficient s-hole found on the halogen atom opposite a covalent bond, i.e., R-X…Y. We report on multinuclear powder and single-crystal solid-state magnetic resonance studies of a range of cocrystals and materials featuring halogen bonds, chalcogen bonds, and tetrel bonds . In addition to establishing relationships between the various NMR parameters and the nature of these electrophilic interactions, we also describe a case study focussing on real-time in-situ kinetic monitoring via 31P CP/MAS NMR of mechanochemical halogen bond formation in the NMR rotor . Our most recent work on the catalysis of dynamical processes via halogen bonding, as studied by deuterium NMR will also be discussed.
In the second part of the talk, we describe two-dimensional double-quantum filtered J-resolved solid-state NMR experiments as applied to homonuclear pairs of quadrupolar nuclei. Such experiments provide valuable information on crystallographic symmetry, bond order, electronic structure, and molecular dynamics. Results for 11B-11B and 71Ga-71Ga spin pairs in singly, doubly, and triply-bonded systems will be presented [3,4]. The crucial role of dynamics in the interpretation of the experimental data will be highlighted for a series of synthetically important electron-precise dianionic diboranes featuring two-centre two-electron bonds .
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