NMR Laboratory

Dr. Wissam Iali
Supervisor

Mr. Mansour Al-Zaki
Supporting Staff

KFUPM
Bldg. 4 - Room 153
Dhahran, P.O. Box 5048
+966 13 860 2274
cls@kfupm.edu.sa

Sunday - Thursday
8:00 A.M - 4:00 P.M

KFUPM Faculty, Students, and Staff can utilize the facilities via booking through KFUPM RRM.

For outside KFUPM Community, you may book your reservations by registering at this link:
https://research.kfupm.edu.sa/RRM/Login.aspx

NMR Spectrometers at NMR-CD center:

1) Bruker AVANCE IIIHD 400 MHz NMR Spectrometer

The 400 is a two-channel Bruker AVANCE-III HD Ultra-shielded spectrometer operating at 400.00 MHz (9.4 T). The spectrometer is equipped with a 5mm liquid broad band observe (BBO) cryoprobe, with actively-shielded high performance Z-gradient at all frequencies. The broadband inner coil optimized for observation of nuclei between 31P and 15N. The outer coil optimized for 1H decoupling (and observation too). The temperature range of this probe is -150oC to +150oC. The spectrometer can be equipped by 3.2mm double resonance HX solids probe capable of Magic Angle Spinning (MAS) speeds of up to 24kHz.

Data is returned via standard email, or can be retrieved from an in-lab data computer for up to 12 months. The spectrometer runs Bruker Topspin software version 3.6.2.

2) Brand new Bruker AVANCE Neo HD 500 MHz NMR Spectrometer equipped with the new generation of liquid and solid states Bruker SmartProbes

The installation of this brand new spectrometer is expected in the coming months.

NEW GENERATION BRUKER liquid iProbes with Z gradient (with 2 G/A*cm): 5mm BBFO, 10mm BBO and 5mm TBO.

The 500 MHz (11.7 T) Bruker AVANCE Neo spectrometer is equipped with Bruker SmartProbes liquid-state of 5mm BBFO designed for direct X-nuclei observation with 1H decoupling and 1H observation. This probe is capable of both routine proton, fluorine and broadband detection from 19F down to 109Ag with Z gradient with 5 G/A*cm. This spectrometer is available for variable temperature experiments in the -150 oC to +150 oC temperature range.

The spectrometer can also be equipped with either a 5mm iTBO X-nuclei-optimized triple resonance broad banded probe designed for direct BB/19F-nuclei observation with 1H/19F decoupling and 1H observation or 10mm X-nuclei-optimized double resonance broad banded probe designed for low gamma X-nuclei observation with 1H decoupling.

Any nucleus in all liquid SmartProbes can be fully automatically selected and optimally tuned and matched (ATM).

New probe Magic Angle Spinning (MAS) for solid experiments

The new spectrometer is equipped with 3.2mm double resonance (H/X) magic angle spinning probe for solid state NMR. MAS rotation frequencies are up to 24±0.005 kHz. The probe possesses an X channel that is tuneable from 31P to 15N. The high frequency side of the probe comprises 1H high power decoupling. The temperature range of solid state NMR is from -50oC to 80oC.

The new 500 MHz Noe spectrometer runs Bruker Topspin software version 4.

3) Nanalysis low field compact benchtop NMR 60 MHz (1.4 T)

This recent benchtop NMR is dedicated for teaching and learning process. It is compact, portable and easy-to-use and it does not require weekly maintenance. This low field NMR can be used to run 1H and 19 F spectra.

The open-access 400 MHz NMR Avance III HD spectrometer Liquid state is designed in such a way that they are very easy to use for routine 1H, 13C and 31P 1D and 2D spectroscopy. Samples that require more complex analysis should be submitted to the NMR service or you may be trained by the NMR staff to do this yourself. You will be shown how to run spectra when you attend a basic training session, which you must do before using these instruments.

NMR staffs mainly access the spectrometers 500 MHz AVANCE Noe liquid/solid states and 400 MHz AVANCE III solid-state.

All potential users who intend to use on a regular basis of the NMR spectrometer at the facility must undergo training, usually in a stepwise fashion, from simple operation and experiments towards more complicated ones, depending on needs.

Ø For new users only, please fill out the Request for Training form (in annex). A training session will be organized for basic instructions to run NMR spectrum.

Ø For existing users, please e-mail or meet with the facility manager with training request along with the following information:

-Period of the training you desire, or the reservation time if time is already reserved. You are advised not to reserve time ahead of time before consulting with the manager.

-Specific experiments or routines you want to be trained for.

Basic Sample Preparation

Before using any NMR spectrometers of NMR-CD center, the sample should be in acceptable condition:

• Use clean and dry sample tubes.
• Use medium to high quality sample tubes.
• Always filter the sample solution.
• Always use the same sample volume or solution height.
• Filling volume of a 5 mm tubes is 0.6 ml or 5 cm.
• Use the sample depth gauge to adjust the sample depth

Choosing a solvent for NMR

NMR samples need to be dissolved in deuterated solvents. Deuterated solvents tend to be expensive so to find out what solvent you should use. Do not put any of the protonated solvent in your NMR tube! The cheapest and most common deuterated solvent is CDCl3 but there are many others available which can be found in a chemical supplier’s catalogue.

Quantity of Material

This will vary from sample to sample.

Solid compounds: ~ 1 to 4 mg for 1H; ~ 10 to 40 mg for 13C.

Liquid compounds: ~ 0.1 to 0.2 Volume % for 1H, ~ 5 to15 % for 13C.

Overnight or longer experiments can be run on small quantities of material if you do not have a lot of your compound. If you find that the compound is not very soluble and some is not dissolved then filter off the suspended material before placing the sample in the NMR tube, as solid materials in the tube will result in a bad spectrum.

For larger molecules (eg. polymers): For larger molecules try adding more compound. 50 mg and more will probably be required. This will obviously also depend on the solubility of your sample. As NMR is not a very sensitive technique it is desirable to have a reasonable amount of material to get quick results, however having too much sample can also be a problem. Extremely viscous samples will have broad lines which is one of the reasons not to add too much sample. Try to avoid preparing very viscous samples if possible.

Presence of solid particles and paramagnetic materials in your sample

Remove all solid particles from your NMR sample by filtering it before placing it in the NMR tube. Solid particles will result in bad resolution spectra and if your entire sample does not dissolve you will not get a true representation of what you have in your vial. The instrument only detects what is dissolved, and that can be your target compound or impurities. Either way, you will not get a true representation of your sample. Solid particles result in a reduction in the transverse relaxation times (T2's) of the nuclei causing broad peaks. In addition it is impossible to homogenise the magnetic field resulting in bad peak shapes and loss of resolution. Paramagnetic materials will also result in unsatisfactory spectra as the lines become extremely broad and resolution is lost. Line width at half height is calculated as 1/T2 and paramagnetic nuclei or suspended solids result in very fast T2 relaxation times.