EPSRC UK National Solid-state NMR Service at Durham Solid-state NMR: Basic Principles, Practice, Interpretation and Applications 2015 Interpretation and

EPSRC UK National Solid-state NMR Service at Durham

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

Interpretation and Applications


The spectrum

However, the general appearance of a spectrum can give us lots of basic information about the sample.

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.


12

CP


The spectrum


The spectrum – spinning sidebands

Spinning sidebands

“Rigid” solid


The spectrum – spinning sidebands

Identifying sidebands

Look for repeating patterns …

… separated by the spin rate

nr

nr

Confirm by changing the spin rate


The spectrum – line widthNarrow lines

Crystalline (if rigid)

Possibly soft (poor CP, no/weak sidebands)


The spectrum - purity

No small signals

Probably pure(in SSNMR terms)


The spectrum

One molecule per crystallographic asymmetric unit

23 carbon sites

19 clear resonances


The spectrum - identification

How can we tell if this is the “right” spectrum?


The spectrum – solid- vs. solution-state


The spectrum – assignment

Correlation chart

ppm from tetramethylsilane



ppm from tetramethylsilane

~








The spectrum – assignment tools

Interrupted decoupling


The spectrum - polymorphism

Observed spectrum

Known shifts for polymorph III

Omitted


The spectrum - polymorphism

Known shifts for polymorph I



Multi-component systems

Inevitably, the question of quantification will arise!


Multi-component systems – quantification of a mixture

Spectra should be recorded so that both components are at full intensity (fully relaxed). RD = 5×T1

H(longest)


Multi-component systems – quantification of a mixture

Identify one (or more) pairs of resonances to represent the components


Intensity vs. contact time

HXH( ) exp( / ) exp( / )S t S t T t T r

é ù= - - -ë û0 11


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



HXH( ) exp( / ) exp( / )S t S t T t T r

é ù= - - -ë û0 11

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.



Extrapolate the long-contact behaviour

Equal intensity


Multi-component systems - quantification

The alternative is to ignore differences between the components and plot a calibration graph based on samples with known composition.

unkn

own

Another inevitability: what are the errors?


Multi-component systems - quantification

Only by replicating measurements can you have real confidence in the errors.

unkn

own


Amorphous materials

Crystalline

Amorphous

Dn½ = 28 Hz

Dn½ = 223 Hz


Amorphous materials

polyethylene

polysaccharide


Semicrystalline polymers

2.2 T1rho filterDP 1s

15us T2 filter

T1r(H) filter 2.2 ms Rigid, o

rder

ed



Delayed contact


Semicrystalline polymers

2.2 T1rho filterDP 1s

15us T2 filter

T1r(H) filter 2.2 ms

DE 1s

T2(H) filter 15 ms

Rigid, o

rder

ed

Soft

Rigid, d

isord

ered


Dynamic systems


Dynamic systems


Dynamic systems

4

3

1

2

Broad – motion?

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)


Elements with spin


“Easy” elements



Intensities from overlapping lines - deconvolution


Silicon-29

Direct excitation

Quantitative


Silicon-29

m,m ,m

m m/I I

= =å å=4 4

4 440 0Si / Al


Deconvolution


Deconvolution

( )observed simulatednx xc å= -

22

Line widths : 220 - 250 Hzχ2 = 129,000

-97.4 -102.4 -107.8

22% 54% 24%


Deconvolution

-90.3 -93.6 -97.4 -102.4 -107.8 -111.5 -99.1

22% 54% 24%

3% 3% 23% 47% 22% 2%

Line widths : 220 - 370 Hzχ2 = 129,000χ2 = 26,000


Deconvolution

Line widths: 150 - 320 Hz, 850 Hzχ2 = 129,000χ2 = 26,000χ2 = 14,000

-90.3 -93.6 -97.4 -102.4 -107.8 -111.5 -99.1

22% 54% 24%

3% 3% 23% 47% 22% 2%

5% 34% 18% 2% (41%)


Silicon chemical shifts

SiR

O

R

O Si

O

R

R

SiXO

O

R

OX Si

OXR

OO

SiXO

O

R

O Si

O

R

O Si

R

OO

SiO

O

O

O

SiO

O

O

OH

SiO

O

OH

OH


Boron (11B spin-3/2)





Bandshape fit:Cq = 1.45 MHzη = 0iso = -23.5 ppm


Aluminium (27Al, 100%, spin-5/2)

Framework

Extra-framework



5?



MQMAS

M = 3


Heavy metals


Coupling

Residual dipolar coupling (between 13C and 14N)


Coupling

Dipolar coupling – through space – distance measurement

“Recouple” – rotor synchronised elements of a pulse sequencee.g. REDOR


1H

Natural “resolution”

H-bond


1H

Natural “resolution”

H-bond


1H

60 kHz


1H

60 kHzHRMAS


Solid-state NMR in the UK

EPSRC UK National Solid-state NMR Service at Durham.

The UK 850 MHz Solid-state Facility at Warwick.

For the NMR expertYou provide the sample we take care of the NMR


Documents

EPSRC UK National Solid-state NMR Service at Durham Solid-state NMR: Basic Principles, Practice, Interpretation and Applications 2015 Interpretation and