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Solid-state NMR Training Course

Solid-state NMR Training Course. Interpretation and applications. The properties of solid-state spectra are more sample-dependent than solution-state ones.

maisie-joseph
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Solid-state NMR Training Course

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  1. Solid-state NMR Training Course Interpretation and applications

  2. The properties of solid-state spectra are more sample-dependent than solution-state ones. Questions on what is possible to say about a sample using solid-state NMR can usually only be answered with confidence once a spectrum has been obtained. The spectrum However, the general appearance of a spectrum can give us lots of basic information about the sample.

  3. CP

  4. The spectrum

  5. Spinning sidebands “Rigid” solid The spectrum – spinning sidebands

  6. Identifying sidebands Look for repeating patterns … … separated by the spin rate The spectrum – spinning sidebands Confirm by changing the spin rate nr nr

  7. Narrow lines Crystalline (if rigid) Possibly soft (poor CP, no/weak sidebands) The spectrum – line width

  8. No small signals Probably pure (in SSNMR terms) The spectrum - purity

  9. 19 clear resonances The spectrum 23 carbon sites One molecule per crystallographic asymmetric unit

  10. The spectrum - identification How can we tell if this is the “right” spectrum?

  11. The spectrum – solid- vs. solution-state

  12. ppm from tetramethylsilane The spectrum – assignment Correlation chart

  13. ppm from tetramethylsilane The spectrum – assignment  ~   

  14. The spectrum – assignment

  15. The spectrum – assignment

  16. The spectrum – assignment

  17. Interrupted decoupling The spectrum – assignment tools

  18. Observed spectrum The spectrum - polymorphism Known shifts for polymorph III Omitted

  19. The spectrum - polymorphism Known shifts for polymorph I

  20. Multi-component systems Inevitably, the question of quantification will arise!

  21. Spectra should be recorded so that both components are at full intensity (fully relaxed). RD = 5×T1H(longest) Multi-component systems – quantification of a mixture

  22. Identify one (or more) pairs of resonances to represent the components Multi-component systems – quantification of a mixture

  23. Intensity vs. contact time

  24. “Spin-lattice relaxation in the rotating frame” Where T1 is the relaxation in the intense static field, T1r is the relaxation in the magnetic field associated with an RF pulse T1r

  25. Different components may have different properties so we need to model the behaviour of the intensity as a function of contact to extract S0. S0 = S (t = 0) is the intensity in the absence of relaxation – and is the value we need to compare intensities from different components. Intensity vs. contact time

  26. Equal intensity Intensity vs. contact time Extrapolate the long-contact behaviour

  27. The alternative is to ignore differences between the components and plot a calibration graph based on samples with known composition. Multi-component systems - quantification Another inevitability: what are the errors? unknown

  28. Only by replicating measurements can you have real confidence in the errors. Multi-component systems - quantification unknown

  29. Dn½ = 28 Hz Amorphous materials Crystalline Dn½ = 223 Hz Amorphous

  30. polyethylene Amorphous materials polysaccharide

  31. Rigid, ordered T1r(H) filter 2.2 ms Semicrystalline polymers 2.2 T1rho filter DP 1s 15us T2 filter

  32. Intensity vs. contact time Delayed contact

  33. Rigid, ordered T1r(H) filter 2.2 ms Semicrystalline polymers Soft DE 1s 2.2 T1rho filter DP 1s 15us T2 filter Rigid, disordered T2(H) filter 15 ms

  34. Dynamic systems

  35. Dynamic systems

  36. 2 3 1 Broad – motion? 4 Dynamic systems To be consistent with the NMR data, the proton must jump from N1 to N2. This is accompanied by a rotation of the tetrazole ring – interchanging N3 and N4 (and making the start and finish arrangement indistinguishable by X-ray) 

  37. Elements with spin

  38. “Easy” elements

  39. Intensities from overlapping lines - deconvolution

  40. Direct excitation Quantitative Silicon-29

  41. Silicon-29

  42. Deconvolution

  43. Deconvolution Line widths : 220 - 250 Hz χ2 = 129,000

  44. Deconvolution Line widths : 220 - 370 Hz χ2 = 129,000 χ2 = 26,000

  45. Deconvolution Line widths: 150 - 320 Hz, 850 Hz χ2 = 129,000 χ2 = 26,000 χ2 = 14,000

  46. R R Si O O R OX R Si Si R O O O R XO Si OX O R R O R XO Si O Si O Si O Si O O O O O O OH O O O Si Si OH OH O O Silicon chemical shifts

  47. Boron (11B spin-3/2)

  48. Boron (11B spin-3/2)

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