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Marek Pruski
U.S. DOE Ames Laboratory, Ames, Iowa 50011, U.S.A
Department of Chemistry, Iowa State University, Ames, Iowa 50011, U.S.A.
Emerging trends in NMR of materials
UHF Workshop, Bethesda, November 12, 2015
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Research needs in materials science
Understanding the structure-‐property rela:ons in novel materials is an unanswered scien:fic challenge, which prevents ra:onal design. A few examples: ! heterogeneous catalysts: supports, cataly8c sites, reac8on
mechanisms ! energy related materials: ba
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Solid-‐state NMR
Challenges: ! intrinsically low sensi8vity of NMR ! low resolu8on; homogeneous and inhomogeneous line
broadening in solids
SS-‐NMR spectroscopy has an unparalleled ability to provide atomic-‐level characteriza:on of materials: ! most elements have NMR-‐ac8ve isotopes ! nuclear spins are excellent, site-‐dependent “reporters” of local
structure and dynamic processes
Transforma:onal role of ultrahigh field in SS-‐NMR: ! ultrafast MAS; indirect detec8on ! low-‐gamma nuclei ! half-‐integer quadrupolar nuclei ! high-‐field DNP
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Characteriza:on by SS-‐NMR
1D MAS spectra of catalytic surface; 14.1 T, MAS at 40 kHz
-150 -100 -50
1H
H1
10.0 7.5 5.0 0.0 2.5
H2
H3 C3
0 20 40 60 80 100 120 140 160
C2 C1
CTAB MeO
13C 29Si OH/H2O
T3 Q2
Q3
Q4 T2
-60 -80 -100 -120 0
2 4
6 8
-1 0 1 2 3 4 5 6 7 8
-1 0 1 2 3 4 5 6 7 8
2D correlation spectra of the same system
1H-13C 1H-1H 1H-29Si
T3 Q3
Q4
T2
H1
H3
H2
H1
H3
H2
C3
0
1
2
3
4
5
6
7
dH ppm
0 20 40 60 80 100 120 140 160 dC ppm
C2 C1
H1
H3
H2
CTAB MeO
AL-MSN 1 3
2
Si
J. Trebosc, et al., J. Am. Chem. Soc., 2005, 127, 3057-3068; J. Am. Chem. Soc., 2005, 127, 7587-7593.
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Emerging technique: ultrafast MAS
Transforma:onal role of ultrafast MAS in SS-‐NMR:
New probes (e.g. ultrafast MAS): new pulse sequences/theory; improved resolution & sensitivity
! MAS rate: 100+ kHz ! volume: ~0.3 μl ! introduced: ~2012
! MAS rate: 45 kHz ! volume: ~9 μl ! introduced: ~2005
! improved 1H resolu8on (Δν~(νMAS)-1)
! indirect detec8on ! sideband-‐free spectra
! be
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1H resolu:on under ultrafast MAS
L-histidine HCl H2O
10.0 010.0 010.0 010.0 010.0 010.0 0
Y. Nishiyama, JEOL Resonance.
1H MAS at 14.1 T
80 kHz100 kHz
60 kHz
40 kHz
20 kHz
110 kHz
! 1H resolu8on and SNR are greatly enhanced by fast MAS ! CRAMPS-‐like resolu8on approached at 100 kHz
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1H resolu:on under ultrafast MAS
L-histidine HCl H2O
Y. Nishiyama, JEOL Resonance.
1H INADEQUATE at 14.1 T
100 kHz
110 kHz
90 kHz
80 kHz
60 kHz
120 kHz
! 1H resolu8on and SNR are greatly enhanced by fast MAS
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1H-‐1H correla:ons under MAS at 100 kHz
100 kHz
80 kHz
60 kHz
40 kHz
-25
25
20
-20
-15
-10
-5
0
5
10
15
δ H(D
Q, p
pm)
10 5 0 -5 -10δH (SQ, ppm)
10
-10
-5
0
5
δ H(ppm)
10 5 0 -5 -10δH (ppm)
10
-10
-5
0
5
δ H(ppm)
10 5 0 -5 -10δH (ppm)
1D MAS
1H-1H DQMAS 100 kHz
slice
A
B B
A
A-B
B
A 1H-1H spin diffusion 60 kHz
T. Kobayashi, et al., Angew. Chem. Int. Ed., 2013, 52, 14108. S.P. Brown, Macromol. Rapid. Commun. 2009, 30, 688-‐716
Ultrafast MAS at 100 kHz: improved resolu:on in 2D 1H-‐1H NMR ! Host-‐guest interac8on in corrole/toluene system
Polymers, supramolecular systems, catalysts, …
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Indirect detec:on of low-‐γ nuclei
1H
Low-γ
S/N gain: ( )( )
2/32/1
//
⎟⎟⎠
⎞⎜⎜⎝
⎛⎟⎟⎠
⎞⎜⎜⎝
⎛≈
X
H
H
X
DD
ID
NSNS
γγ
δνδνα
Tradi:onal SSNMR approach: direct detec:on of low-‐γ nuclei (e.g. 13C, 15N)
1H
Low-γ
Indirect detec:on of low-γ nuclei
! 1H homonuclear RF decoupling ! low sensitivity
! 1H decoupling by fast MAS ! high sensitivity
For 15N:
�
γ HγN
⎛
⎝ ⎜
⎞
⎠ ⎟ 3 / 2
= 31 time performance improves by ~103!
t2 : 1H
t1 : 1H
t2 : X
t1 : X
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1H-‐13C HETCOR under fast MAS: cataly:c surface
8 6 4 2 0
0 50
10
0 15
0
150 125 100 75 50 25 0
0 2.
5 5
7.5
H1 H3 H2
C2
C1
C3
CTAB
CTAB
(b) C2 C3 C1
H1
H3
H2
CTAB
CTAB (a)
Si≡ 1
2
3
F1
F2
F1
F2
Direct 15 h
Indirect 15 min
AL-MSN 1 3
2
Si
13C, 15N
CP or INEPT
t1
Y Y,Y
t2 SPINAL-64
1H
X
Y
Decoupling
2τRR
ϕ, ϕ+π
τCP τCP
X Y
Recoupling
X
! 1H-1H homonuclear RF decoupling INEPT
Through space correlations: Ishii, Y.; Tycko, R. JMR, 2000, 142, 199; Wiench, J.W. et al. JACS 2007, 129, 12077; Zhou D.G. et al., JACS 2007, 129, 11791
Through-bond correlations: Elena, B. et al. JACS, 2005, 127, 17296; Mao, K.; Pruski, M. JMR, 2009, 201, 165;
40 kHz MAS
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1H-‐13C HETCOR under MAS at 100 kHz
! Excellent sensi8vity and resolu8on; all resonances detected
! 1H-‐1H interac8ons are suppressed during CP; one-‐bond selec8vity (dipolar trunca8on)
! HMQC possible when T2’ > 10 ms
5 4 3 2 1
40
30
20
10
13C
Che
mic
al S
hift
/ ppm
1H Chemical Shift / ppm
10 8 6 4 2 0 -2 -4
140
120
100
80
60
40
20
0
13C
Che
mic
al S
hift
/ ppm
1H Chemical Shift / ppm
MP
a
b
c
a
b c
7 h
MP-‐MSN
T. Kobayashi, et al., Angew. Chem. Int. Ed., 2013, 52, 14108.
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! Sensi8vity/scan at 100 kHz close to that of 1.6-‐mm probe (>50% in terms of SNR), in spite of 20x smaller volume
! Resolu8on in (A) similar to PMLG (C)
HSQC of f-‐MLF-‐OH under natural abundance at 14.1 T
Y. Nishiyama, T. Kobayashi, et al., SSNMR, 66-‐67, 56-‐61 (2015)
(A) 100 kHz MAS (0.75-‐mm); 1H detec:on; 5 h
(B) 41.667 kHz MAS (1.6-‐mm); 1H detec:on; 10 h
(C) 41.667 kHz MAS (1.6-‐mm); 13C detec:on; PMLG during t1, 10 h
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13C CPMAS NMR of Argonne Premium Coals at low and high magne:c field
8 mg 8 h 42 kHz 1 +
Sample weight: Acquisition time: MAS rate: Sensitivity (per scan): Resolution:
150 mg 8 h 8 kHz 1.5-2.0 - 15N or 33S??
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Studies of low-‐γ nuclei: 15N under natural abundance
Similar techniques can be used/developed for other low-γ nuclei in many classes of materials
15N-‐1H HETCOR of amino acids through space through bond
Need higher magnetic field!!!
Althaus et al., SSNMR, 57-‐58, 17-‐21 (2014); collabora8on with R. Schurko, University of Windsor
15N-‐1H HETCOR of pharmaceu8cals through space
�
γ HγN
⎛
⎝ ⎜
⎞
⎠ ⎟ 3 / 2
= 31
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Half-‐integer quadrupolar nuclei Most NMR-active nuclei are half-integer quadrupolar: 77 out of ~110, including 7Li, 11B, 17O, 23Na, 25Mg, 27Al, 33S, 35Cl, 39K, 43Ca, 55Mn, 87Rb, … The challenge: SSNMR spectra are dominated by quadrupolar broadening
ΔE(2)
ΔE(1)
ωcentral
ΔE(1)
m
+3/2
+1/2
-‐1/2
-‐3/2
Zeeman I-st order II-nd order
3ω0
ω0
ω0
ω0
ω0
)1cos9)(cos31}(4/3)1({16
22
0
2
0 −−−+−= ββωω
ωω IIQcentral
Typical values for 27Al: = 1 MHz, = 10 kHz 27Al chemical shift range at 9.4 T: 10 kHz
)1(mEΔ )2(mEΔ
ω0
I-‐st ordrer single crystal
II-‐nd order (CT)
Sta8c spectra
I-‐st ordrer powder
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Advances in NMR of quadrupolar nuclei: complete line-‐narrowing
isotropic
anisotropic
ω−m↔m(2) =
ωQ2
ω 0A0 (I , p)B0
Q (ηQ )+
ωQ2
ω 0A2 (I , p)B2
Q (ηQ ,αQ ,βQ )P2 (cosθ )+
ωQ2
ω 0A4 (I , p)B4
Q (ηQ ,αQ ,βQ )P4 (cosθ )
csmmmmmm m ↔−↔−↔− ++= ωωωω
)2(02
)](cos),,([2 220 θβαηδωω PBm cscscscscs
mm +Δ=↔−
where: p = 2m; αQ, βQ – angles between QPAS and rot. axis; θ -‐ angle between rota8on axis and B0; P2,4(cosθ) – 2nd and 4th order Legéndre pol.; At(I,p), i = 0,2,4 -‐ coefficients The resonance frequency also includes chemical shit
P2(cosθ) and P4(cosθ) do not have a common root; MAS narrows second order broadening only by a factor of ~3; DOR, DAS and MQMAS yield isotropic spectra
with
A. Pines et al., Mol. Phys. 65, 1013 (1988); JMR, 86, 470 (1990); L. Frydman et al., JACS, 117, 5367 (1995)
}Symmetric transi8on under fast rota8on of the sample
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Example: mechanisms of dehydrogena:on in metal hydrides
Mechanochemistry
DFT Modeling Solid-‐state NMR 7Li, 11B, 23Na, 27Al
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Example: mechanisms of dehydrogena:on in metal hydrides
Need higher magnetic field!!!
Our approach: ! measure 1D and 2D NMR spectra of 1H,
7Li, 11B, 23Na, 27Al and other nuclei in hydrides processed under various condi8ons and in reference compounds
! obtain chemical shits and quadrupolar parameters (for spins > 1/2) to iden8fy the coordina8on geometries and chemical structures
! carry the out addi8onal SSNMR experiments to probe interatomic correla8ons, molecular mo8ons, etc.
! refine the structures using molecular modeling and DFT calcula8ons
11B MQMAS
11B MAS
DFT (δCS, PQ)
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Spectra of quadrupolar nuclei at ultrahigh fields
Transforma8onal role of ultrahigh field: at 40 T, second order quadrupolar broadening and shit are diminished; the line width is mainly due to field drit
27Al MAS spectra of aluminoborate 9Al2O3+2B2O3
Simulated MAS spectra of 23Na in NaC2O4/NaSO4 mixture at 14.1 T and 36 T
40 T (NHMFL, hybrid)
25 T (NHMFL, resis:ve)
19.6 T
Z. Gan et al., JACS, 124, 5634 (2002)
ΔEm(2),ω−m↔m
(2) ∝ B0−1
14.1 T
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2D 27Al-‐31P HETCOR spectra of AlPO4-‐14:
! Resolu8on of MAS-‐based spectra at 18.8 T in (c) and (d) rivals that of MQ-‐HETCOR taken at 9.4 T! (not shown here) Assuming 20% efficiency of MQMAS, 8me performance at 36 T could improve by an incredible factor of (36/9.4)5 8mes 52 ≅ 2x104
2D HETCOR spectra of quadrupolar nuclei at high fields
!
M. Pruski et al., JMR, 184, 1 (2007)
9.4T
18.8T 18.8T
18.8T 18.8T
9.4T
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Conclusion and acknowledgments
Funding (Ames) U.S. Department of Energy, BES (DE-AC02-07CH11358)
Coworkers/collaborators Ames:
T. Kobayashi I.I. Slowing J.W. Wiench V.K. Pecharsky V. Lin D. Johnson S.M. Althaus S. Gupta
Tokyo: Y. Nishiyama (JEOL)
Lille/Caen: J.-‐P. Amoureux
C. Fernandez J. Trebosc
Thank you DOE, NSF and NIH for suppor:ng our science!
The role of ultrahigh field in SS-‐NMR and materials research will be transforma:onal:
! drama8cally expanded capabili8es: resolu8on, detec8on limits, range of nuclei
! drama8cally expanded range of applica8ons to new materials
ExxonMobil: K. Mao G. J. Kennedy