Chemistry Weekly Seminar - Dr. Cory Widdifield, University of Regina

Topic:

NMR Crystallography: Structure Refinements, Verifications, and Determinations

A sufficiently large number of observables are associated with each nuclear magnetic resonance (NMR)-active nucleus in the solid state (e.g., chemical shifts, dipolar coupling constants, etc.) to yield accurate structure determinations of many systems. When experimental observables are paired with calculated outputs from quantum chemistry, atomic-level details of structure can be elucidated with a precision that compares very favourably with other techniques, such as X-ray/neutron diffraction.

Indeed, numerous studies have established the complementary nature of X-ray/neutron diffraction, NMR, and computational modelling. When these techniques are used for crystal structure refinements, determinations, etc., they are regularly classified as applications of “NMR crystallography”.

In this seminar, NMR crystallography applications are presented which attempt to highlight the utility of solid-state NMR in structure refinements, verifications, and determinations. So-called “quadrupolar nuclei” (spin quantum number > ½) are seen, through their characteristic observables, to be particularly sensitive at structure refinements for several inorganic systems. In contrast, “traditional” ¹H and ¹³C chemical shifts, when coupled with crystal structure prediction and density functional theory quantum chemistry approaches, can be used to determine and/or verify the structures of materials containing organic molecules. The full 3-dimensional structure determination of surface-supported species, including those that act as heterogeneous catalysts, is also touched upon.

Date:    Friday, March 18

Time:    1:30 pm

Zoom link available by request from chem.dept@usask.ca