1. Solid-state NMR: Basic Principles, Practice, Interpretation and Applications 2015

2. The spectrum
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.
However, the general appearance of a spectrum can give us lots of basic information about the sample.
Examples mostly carbon – but applies elsewhere too.

3. CP
Reiterate. Could apply to quadrupoles – particularly for spin ½.

4. The spectrum

5. The spectrum – spinning sidebands
“Rigid” solid

6. The spectrum – spinning sidebands
Identifying sidebands
Look for repeating patterns …
… separated by the spin rate
Usually lower intensity than centreband – but not always (CN) Depends on spin rate. Second order.
Confirm by changing the spin rate nr nr

7. The spectrum – line width
Narrow lines
Crystalline (if rigid)
Possibly soft (poor CP, no/weak sidebands)
<100 Hz

8. The spectrum - purity No small signals Probably pure (in SSNMR terms)
That are not sidebands

9. The spectrum 19 clear resonances 23 carbon sites
Roughly 1:1
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
Some abiguity but most assignments can be made.

12. The spectrum – assignment
ppm from tetramethylsilane
Correlation chart

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

14. The spectrum – assignment

15. The spectrum – assignment

16. The spectrum – assignment
COOH C= CH= COH 88.6

17. The spectrum – assignment tools
Interrupted decoupling
Dipolar dephasing NQS. Also for 15N. Double signals. One of the pulse sequences with extra X pulse.

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

19. The spectrum - polymorphism
Known shifts for polymorph I

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

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

23. Multi-component systems – quantification of a mixture
Identify one (or more) pairs of resonances to represent the components
Separated – directly integrate intensity. Could use height but line widths might be different (and might vary from sample to sample)

24. Intensity vs. contact time

25. T1r “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 T1
T1r
Frequency of motion causing relaxation
MHz
kHz
Timescale of relaxation
seconds
milliseconds

26. Intensity vs. contact time
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.
50:50 mixture. At no contact time do we see the full intensity.

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

28. Multi-component systems - quantification
The alternative is to ignore differences between the components and plot a calibration graph based on samples with known composition.
Another inevitability: what are the errors?
Error sources: instrument (noise), processing (deconvolution, integration-baseline shape), sampling
unknown

29. Multi-component systems - quantification
Only by replicating measurements can you have real confidence in the errors.
Error sources: instrument (noise), processing (deconvolution, integration-baseline shape), sampling
unknown

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

31. Amorphous materials polyethylene polysaccharide
Quantification – same issues (more extreme)

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

33. Intensity vs. contact time
Delayed contact

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

35. Dynamic systems

36. Dynamic systems

37.  Dynamic systems 3 2 1 Broad – motion? 4
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) 

38. Elements with spin

39. “Easy” elements

41. Intensities from overlapping lines - deconvolution

42. Silicon-29 Direct excitation Quantitative
Abundant enough. Zeolite X. Si:Al

43. Silicon-29
Abundant enough. Zeolite X. Si:Al (1.9).

44. Deconvolution

45. Deconvolution Line widths : 220 - 250 Hz χ2 = 129,000 -97.4 -102.4
-107.8
22%
54%
24%
Line widths : Hz
χ2 = 129,000

46. Deconvolution Line widths : 220 - 370 Hz χ2 = 129,000 χ2 = 26,000
-90.3
-93.6
-97.4
-102.4
-107.8
-111.5
-99.1
22%
54%
24% 3%
23%
47% 2%
Line widths : Hz
χ2 = 129,000
χ2 = 26,000

47. Deconvolution Line widths: 150 - 320 Hz, 850 Hz χ2 = 129,000
-90.3
-93.6
-97.4
-102.4
-107.8
-111.5
-99.1
22%
54%
24% 3%
23%
47% 2% 5%
34%
18%
(41%)
Line widths: Hz, 850 Hz
χ2 = 129,000
χ2 = 26,000
χ2 = 14,000
Crystalline and amorphous components.

48. Silicon chemical shiftsOH Si XO O R OX Si R O

49. Boron (11B spin-3/2)
High sensitivity (11).

50. Boron (11B spin-3/2)
Field dependence.

51. Boron (11B spin-3/2) Bandshape fit: Cq = 1.45 MHz η = 0
iso = ppm
Cq = 1.45 MHz, eta=0 (axial symmetry), diso=-23.5 ppm

52. Aluminium (27Al, 100%, spin-5/2)
Framework
Extra-framework

53. Aluminium (27Al, 100%, spin-5/2)5?
Shape - distribution

54. Aluminium (27Al, 100%, spin-5/2)
MQMAS
M = 3
Shape.

55. Heavy metals
Range. Locating signal. Centreband. Dilution. Intensity distribution.

56. Coupling Residual dipolar coupling (between 13C and 14N)
Less obvious at higher field. Might be just a broadening. J too small relative to linewidth. Still present under MAS.
Residual dipolar coupling (between 13C and 14N)

57.  Coupling Dipolar coupling – through space – distance measurement
“Recouple” – rotor synchronised elements of a pulse sequence
e.g. REDOR
Labelling. Specific pairs. PAIRS – otherwise many couplings. Triple resonance.

58. 1H
Natural “resolution”
H-bond
Soft solids.

59. 1H
Natural “resolution”
H-bond

60. 1H
60 kHz

61. 1H
60 kHz
HRMAS
Physical properties of sample through relaxation.

62. Solid-state NMR in the UK
EPSRC UK National Solid-state NMR Service at Durham.
The UK 850 MHz Solid-state Facility at Warwick.
You provide the sample we take care of the NMR
For the NMR expert