I tried to calculate an NMR spectrum of an optimized geometry using DFT/b3lyp. I only used the keyword NMR. I did get the chemical shifts but there was no information about the intensity of each peak. Is there a way to get this information?
Thank you in advance!!!
Here are some help for you:
http://web.mit.edu/fbml/winterschool2008/talks/WedWS%20-%20Polenova_DFT_final.pdf
http://web.chem.ucsb.edu/~kalju/chem112L/public/nmr_split.html
http://www.gaussian.com/g_tech/g_ur/k_nmr.htm
All the best
Gaussian will give you only isotropic shielding constants (which you can then convert to chemical shifts) of different atoms, and no information about the real intensities. As gaussian NMR calculations are done with a (non-dynamic) single point structure, you will e.g. usually get different chemical shifts of protons of a methyl group, which are obviously averaged to single peak with relative intensity=3 in your observed spectrum. Therefore, you will need to figure out the NMR grouping of your molecule (i.e. which groups are chemically equivalent) yourself and average the DFT chemical shifts of those. Additionally, if you want to fully simulate your spectrum, you would also need to calculate the coupling constants with Gaussian and then use some spectral simulation software with the Gaussian-calculated NMR parameters as input.
For QM calculations of NMR parameters, I have found the CHESHIRE web site (http://cheshirenmr.info/) useful, they list recommendations for chemical shift and J-coupling calculations with Gaussian.
which is the magnitude of the magnetic field to calculate NMR properties ?
http://web.mit.edu/fbml/winterschool2008/talks/WedWS%20-%20Polenova_DFT_final.pdf
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