Small Molecule Characterisation
NMR is a crucial tool as part of the characterisation of small molecules, often paired with mass spectrometry to determine the exact structure of synthetic products. With the Bruker 400 MHz NMR spectrometer in the Chemistry Research Facility, it is possible to characterise small to medium sized molecules and some more complex molecules with manual experiments. As part of the NMR spectrometer configuration, we have installed a Sample Express automated sample handler.
Diffusion Ordered Spectroscopy
Diffusion Ordered Spectroscopy or, DOSY, is a technique that detects the motion of molecules in solution. One main use for this technique is the measurement of hydrodynamic radius. This property corresponds to the radius of the molecule if it was modelled as a sphere in solution. When synthesising complexes, such as ligated organometallic compounds, knowing the hydrodynamic radius can confirm the structure.
Whether performing a routine synthesis, optimising a new synthesis, or monitoring the activity of an enzyme, NMR can be used to track the progress of a reaction over time. This can be done either with the reaction happening within the spectrometer (in-situ) or, by taking samples from a reaction as it progresses (ex-situ).
Variable Temperature NMR
With the spectrometer available in the Chemistry Research Facility, it is possible to cover temperature ranges of 298 K to 373 K. This temperature range can be used to measure thermodynamic and kinetic parameters of your system within the spectrometer. Variable temperature experiments are particularly useful for molecules that show conformational exchange in room-temperature NMR which clutter the spectra and make assignment difficult. With an increase in temperature, it can be possible to increase the rate of exchange and resolve such tricky spectra. Variable temperature can also be included as part of reaction monitoring and reaction optimisation.
Detection of Non-Standard Nuclei
Many NMR experiments focus on the study of the ‘standard’ NMR-active nuclei, including 1H, 13C, 15N, 19F and 31P. However, some projects can demand detection of other nuclei. Such experiments can be performed in the Chemistry Research Facility as the current configuration uses a broadband probe. If you are interested in detection of ‘non-standard’ nuclei, please get in touch to discuss your needs with our NMR instrument technician.