Probing the Structure and Dynamicsof Hydrogen Bonds and

Aromatic Pi-Pi Interactionsby Solid-State NMR

Steven P. Brown

Department of PhysicsUniversity of Warwick

Solution-State NMR

10 5 015 ppm

Chemical ShiftDifferentiation of Chemicallyor CrystallographicallyDistinct Sites

J CouplingIdentification of Through-BondConnectivities

Solid-State NMR: Anisotropic Interactions

The resonance frequency of a given nucleus within a particular crystallitedepends on the orientation of the crystallite

For a powdered sample, anisotropic broadening is observed

Solid-State NMR: Anisotropic Interactions

Chemical Shift AnisotropyDipolar

CouplingQuadrupolar

Coupling

Electronic Structureand Bonding

Internuclear Proximitiesand Distances

MotionalProcesses

Relative Magnitudes of Solid-State NMR Interactions

Dipolar Couplings

13C-1H = 23 kHz (directly bonded CH pair)

1H-1H = 20 kHz (CH2 group)

13C-13C = 3 kHz (directly bonded CC pair)

Chemical Shift Anisotropy

13C = 9 kHz (carbonyl group, at 500 MHz)

J Couplings

15N-1H = 90 Hz (directly bonded NH pair)

13C-13C = 35 Hz (directly bonded aliphatic CC pair)

Isotropic Chemical Shift Range

1H = 20 ppm = 10 kHz (at 500 MHz)

13C = 200 ppm = 25 kHz (at 500 MHz)

250 200 150 100 050 −50

60 30 0 −30

14 12 10 8 02 −4−26 4

14 12 10 8 02 −4−26 4ppm

High-Resolution Solid-State NMR

L-alanine

13C MAS5 kHz

1H MAS5 kHz

1H MAS30 kHz

1H CRAMPS

�B0

νr

54.7°

Magic-AngleSpinning

Double-Quantum Coherence

An isolatedspin I = 1/2

nucleus

A single resonanceat the Larmor

frequency

Single-Quantumcoherence

m = + 1/2

m = − 1/2

∆m = ±1

ω0

ω0

Double-Quantum (DQ) (∆m = ±2) coherences cannotbe directly observed in an NMR experiment, but they

can be indirectly probed by a 2D experiment

A through-spacedipolar-coupled pair of

spin I = 1/2 nuclei

The observable(SQ) spectrum

(Also applies to a

through-bond

J-coupledspin pair)

ωD

M = + 1

M = − 1

M = 0

ω0 − ωD/2

ω0 + ωD/2

, DQ

SQ

SQ

Excitationof DQC

Evolutionof DQC (t1)

Acquisitionof FID (t2)

Conversionto SQC

A Two-Dimensional Double-Quantum Spectrum

To a first approximation,the signal intensity is

proportional to thedipolar coupling squared

(double-quantumcoherences must be bothexcited and reconverted),

i.e., the signal intensityis inversely proportional

to the internucleardistance to the

sixth power.

Therefore, a DQ peak isonly observed if there isa close proximity of the

involved protons. single-quantum dimension

doub

le-q

uant

um d

imen

sion

A

A A

A B

B B

B

ωA

ωA

ωA

ωB

+ω

Aω

B+

ωB

ωB

+

Recovering the 13C-13C J Coupling

L-alanine

13C

1H

1H1H

1H 13C13C

13C−1HJ coupling

1H−1Hdipolar coupling

13C CSA

13C−1Hdipolar coupling

13C−13Cdipolar coupling

13C−13CJ coupling

13C Chemical Shift / ppm

MAS (30 kHz)1H decoupling

(TPPM)

13C−13CJ coupling

is observed

181920212223 ppm

176177178179180 ppm

CH3

CO

through-bond connectivitesare traced out

α COβ

γ

δ'ε'

ζε

δ

The Solid-State INADEQUATE Experiment

Lesage et al, JACS 119, 7867 (1997)

Fyfe et al, JACS 112, 3264 (1990)

Only homonuclear J couplingsare active during 2τ

Double-Quantum Coherence iscreated for J-coupled nuclei

CP

1H:TPPM

CP

X, e.g.13C15N

t1τ τ

p = 0+1

−1−2

+2

t2

Cα CβCγCδ'

Cδ Cε Cε'Cζ

CO

406080100120140160180

100

140

180

220

260

single quantum frequency (ppm)

doub

le q

uant

um fr

eque

ncy

(ppm

)

Hydrogen-Bond Mediated J-Couplings: Solution-State NMR of Biomacromolecules

Dingley & Grzesiek JACS 120, 8293 (1998)

Watson-Crick Base Pairs

2hJNN = 7-10 Hz 1hJHN = 2-4 Hz

15N H

13C'

residue i residue j

O

13C� H�

13C'O

13C�

15N H

The Secondary Structureof Proteins

3hJNC' = 0-1 Hz

Cordier and Grzesiek,JACS 121, 1601 (1999)

Cornilescu et al,JACS 121, 2949 (1999)

The hydrogen-bond mediated J couplings depend on the hydrogen-bonding distances

and geometries, and are also correlated with the 1H chemical shifts.

Is it Possible to Observe Hydrogen-Bond Mediated J-Couplings in the Solid State?

-60 -100 -140 -180 -220 ppm

15N Chemical Shift / ppm (relative to nitromethane)

N1

N9

N1'N3' N4'

N

N

C6H5

N

H

N

N

1

4'

3'

1'

9

solution (CDCl3)(Claramunt et al

Angew. Chem. 40, 420):

1JNN = 11.8 Hz

2hJNN = 8.6 Hz

The homonuclear

J couplings are

not resolved in the15N CP-MAS spectrum

N3' N4'

N9

N1'

N1

The Spin-Echo Experiment and Refocused Linewidths

The spin-echo experiment

CP τ τ

p = 0

+1

−1

All terms that appear as offsets(due to e.g. a chemical shift

distribution or imperfect decoupling)are refocused (i.e., removed) Refocused linewidths as small

as a few Hz are observed.

Lesage, Bardet, & Emsley,JACS 121, 10987 (1999)

Earl & VanderHartJACS 102, 3251 (1980)

Cowans & GrutznerJMR A105, 10 (1993)

N

N

C6H5

N

H

N

N

1

4'

3'

1'

9

15N INADEQUATE Spectra

15N Single-Quantum Frequency

15N Chemical Shift− 50 ppm200−150−100−

N3'N4' N9 N1'

N1CPMAS

1D INADEQUATE

ppm −100 −150 −200 −250

−260

−300

−380

−340

15N

Dou

ble-

Qua

ntum

Fre

quen

cy

N9

N1'

N1

N9

−100 −200

2D INADEQUATE

Direct Detectionof a Solid-StateHydrogen Bond

Brown et al,JACS 124, 1152

Homonuclear J Spectroscopy

The spin-echo experiment

CP τ τ

p = 0

+1

−1

For a series of rotor-synchronised τ values, measure the integrated

intensity (after Fourier transformation)for a given resonance

S(τ) = A exp(−2τ / T2) cos(2π J τ)

Zero crossings at: 2π J τ = (2n-1) (π/2)

0.0

0.5

1.0

τ

inte

nsity

/ a.

u.

τ

0.0

0.5

−0.5

1.0

inte

nsity

/ a.

u.

S(τ) = A exp(−2τ / T2)

(1/4J) (3/4J) (5/4J)

Kubo & McDowellJCP 92, 7156 (1990)

Wu & WasylichenOrganometallics 11, 3242 (1992)

Homonuclear J Spectroscopy: Measuring Homonuclear J Couplings

one J-coupled neighbour

fit to A exp(−2τ / T2) cos(2π J τ) A exp(−2τ / T2) cos(2π J1τ) cos(2π J2τ)

0 10 20 30 40 50

−0.8

−0.4

0.0

0.4

0.8

τ / ms

inte

nsity

/ a.

u.

N

N

C6H5

N

H

N

N

1

4'

3'

1'

9

T2 = 248 ± 15 msFWHMH = 1.3 Hz

1J(N9,N1') = 11.9 ± 0.1 Hz

0 10 20 30 40 50−0.2

0.0

0.2

0.4

0.6

0.8

1.0

τ / ms

inte

nsity

/ a.

u.

N

N

C6H5

N

H

N

N

1

4'

3'

1'

9

T2 = 194 ± 15 msFWHMH = 1.6 Hz

1J(N9,N1') = 12.0 ± 0.1 Hz

2hJ(N1...H...N9) = 7.2 ± 0.1 Hz

two J-coupled neighbours: fit to

The Determination of 15N-15N J Couplings

Pyrrole derivative in solution (CDCl3): J = 10.3 Hz J = 9.0 Hz

Triazole derivative in solution (CDCl3): J = 11.8 Hz J = 8.6 Hz

0 10 20 30 40 50

−0.8

−0.4

0.0

0.4

0.8

τ / ms

inte

nsity

/ a.

u.

N

N

C6H5

N

H

N

N

1

4'

3'

1'

9

J =11.9 ± 0.1 Hz

J =10.3 ± 0.1 Hz

0 10 20 30 40 50

−0.8

−0.4

0.0

0.4

0.8

τ / ms

inte

nsity

/ a.

u.

N

N

C6H5

N

H

1

1'

9

0 10 20 30 40 50

0.6

0.8

−0.4

−0.2

0.0

0.2

0.4

1.0

τ / ms

inte

nsity

/ a.

u. N

N

C6H5

N

H

1

1'

9

J =8.1 ± 0.2 Hz

0 10 20 30 40 50

0.0

0.2

0.4

0.6

0.8

1.0

τ / ms

inte

nsity

/ a.

u. N

N

C6H5

N

H

1

1'

9

J = 8.0± 0.3 Hz

J = 10.2± 0.4 Hz

0 10 20 30 40 50−0.2

0.0

0.2

0.4

0.6

0.8

1.0

τ / ms

inte

nsity

/ a.

u.

N

N

C6H5

N

H

N

N

1

4'

3'

1'

9

J = 7.2± 0.1 Hz

J = 12.0± 0.1 Hz

0.0

0.5

1.0

0 10 20 30 40 50τ / ms

inte

nsity

/ a.

u.

−0.5

N

N

C6H5

N

H

N

N

1

4'

3'

1'

9

J =7.4 ± 0.1 Hz

1H MAS NMR of an Alkyl-Substituted Hexabenzocoronene Derivative

Hexabenzocoronene(HBC) derivativespossess very high1D charge carriermobilities because

of the overlap of theπ orbitals due to thepolyaromatic cores

A B CC12D2H23

C12D2H23

C12D2H23

C12D2H23

H23D2C12

H23D2C12

HH

HH

HH

HH

HH

HH

MAS at35 kHz

500 MHz(11.8 Tesla)

-4-210121416 8 6 4 2 0 ppm

solid phase(T = 60 °C)

liquid-crystalline

phase(T = 110 °C)

In solution (CDCl3), there is a single aromatic1H resonance with a concentration-dependent

chemical shift between 8.0 and 8.9 ppm

1H DQ MAS NMR of an Alkyl-Substituted Hexabenzocoronene Derivative

�

�

�

�

� � �

C12D2H23

C12D2H23

C12D2H23

C12D2H23

H23D2C12

H23D2C12 �

A B C

single-quantum dimension

doub

le-q

uant

um d

imen

sion

12 10 8 6 4 2 0 -2 ppm

-5

0

5

10

15

20

�C �C

�A �B

MAS at 35 kHz500 MHz (11.8 Tesla)

solid phase (T = 60 °C)

�C �C�A �B

two types of pairs:

and

in a ratio 2:1

The Packing of the Aromatic Cores in Hexabenzocoronene

� �� �

� � � � �

��

�

� �

��

�

��

�

�

� �

AA

A A

CC

C C

BB

B B

Herring-bonearrangement

optimisespi-pi packing

deshielded(high ppm)

shielded(low ppm)

The staggeredarrangement of

the aromatic coresleads to three

different chemicalshifts, becauseof the different

ring currenteffects

DQ MAS Spinning-Sideband Patterns

doub

le-q

uant

um

doub

le-q

uant

um

ppm

8

12

16

20

single-quantum

single-quantum

10 8 6 4ppm

5 0 -5 -10 -15

ω/ωR

1015

D.τexc

2.8

2.4

2.0

1.6

1.2

0.4

0.8

DQ MAS Spinning-Sideband Patterns

ppm

1H DQ MAS spinning-sidebandpatterns are very sensitive to

the dipolar coupling

1 -1 -3 -5 ω/ωR35

fast rotation about columnar axis:reduction of dipolar coupling by 0.5

best-fit simulations:Solid phase: D = 15.0 ± 0.9 kHzLC phase: D = 6.0 ± 0.5 kHz

LC order parameter S = 0.80 ± 0.08

solid phaseMAS at 35 kHzτexc = 57 µs

LC phaseMAS at 10 kHzτexc = 200 µs

1H (700 MHz) NMR of a Molecular Tweezer

ppm

�

��

��

ppm

-3-2-111 10 9 8 7 6 5 4 3 2 1 0 ppm

-6

-4

-2

22

20

18

16

14

12

10

8

6

4

2

0

H1 H2

H1H2

MAS at30 kHz

DQ MAS spectrum

CN

CN

HHHH

-3-2-111 10 9 8 7 6 5 4 3 2 1 0 ppm

single-quantum dimension

doub

le-q

uant

um d

imen

sion

1H-13C (700 MHz) Correlation Spectrum of a Molecular Tweezer

ppm

�

��

��

MAS at30 kHz

CN

CN

HHHH

13C chemical shift1H chemical shift

20406080100120140160180 ppm

-1

10

9

8

7

6

5

4

3

2

1

0

-4-214 12 10 8 6 4 2 0 ppm

1 H c

hem

ical

shi

ft

One-bond (C-H) correlations

Ring Current Effects on the Guest

ppm

�

��

��

CN

CN

HHHH

ViewA

ViewA

ViewB

ViewC

ViewC

ViewB

b

a

b

a

b

a

Ab initio 1H chemical shift calculationsGIAO-HF/TZP//HF/6-31G*

vac- View View View vacuum fulluum A B C −sum calc.

Ha 8.0 −0.9 −0.9 −1.0 5.2 5.3

Hb 7.9 −1.2 −3.6 −1.7 1.4 1.7

(Ochsenfeld et al, Solid State NMR 22, 128, 2002)

Probing the Guest Dynamics

Upon heating, thetwo 1H guest aromaticresonances coalesce

because ofguest dynamics

ppm

-3-2-111 10 9 8 7 6 5 4 3 2 1 0 ppm

-6

-4

-2

22

20

18

16

14

12

10

8

6

4

2

0

H1 H2

H1H2

Temperature-dependent

changes in slicesfrom 1H DQ MAS

spectra

T/K

410

396

381

367

353

-210 8 6 4 2 0 ppm

�

��

��

CN

CN

HHHH

� �� �

�

�

� �

� �

� �� �

�

� �

� �

�

�

� �� �

�

�

�

��

�

� � � �N N N

N

Ha Ha

Ha

Ha

Ha Ha

Hb

Hb

Hb

Hb

Hb

Hb

N N

1H (700 MHz) NMR of Bilirubin

responsible for jaundice in new-born babiesinsoluble in aqueous solution, because ofstrong intramolecular hydrogen bonding

�

�

O

O

H

H HH H

H

C

C

CH2

N N

N N

O

O

O

O

-6-4-220 18 16 14 12 10 8 6 4 2 0 ppm

MASat 30 kHz

DQ MASspectrum

OH NH1

ppm

891011121314151617 ppm

8

10

12

14

16

18

20

22

24

26

28

30

NH2

OH NH1

NH2NH1

1H (700 MHz) DQ MAS Spinning-Sideband Patterns for Bilirubin

�

�

O

O

H

H HH H

H

C

C

CH2

N N

N N

O

O

O

O

MASat 30 kHz

Fitting to the experimentalDQ MAS spinning-sidebandpatterns allows the accurate

determination of

�

� � � � � � � � � � � � ���

� �

1 -1 -3 -5 -7 -9 ω/ωR3579

186 ± 2 pmH H

τexc67 µs

τexc100 µs

τexc133 µs

Acknowledgements

Alexander von Humboldt-Stiftung (January 1998 - December 1999)

Marie Curie Fellowship (HPMFCT-2000-00525) (January 2001 - September 2002)

EPSRC Advanced Research Fellowship (October 2002-)

Hans W. Spiess,

Max-Planck-Institute for Polymer Research, Mainz, Germany (1998-2000)

Lyndon Emsley,

Ecole Normale Superieure de Lyon, France (2001-2002)

Hydrogen-Bond Mediated J couplings:

Rosa Claramunt, Marta Perez-Torralba, Dionisia Sanz (UNED, Madrid, Spain)

Hexabenzocoronenes:

Klaus Muellen, Johann Diedrich Brand, Ingo Schnell (MPI-P, Mainz, Germany)

Molecular Tweezers:

Frank-Gerrit Klaerner, Torsten Schaller, Uta P. Seelbach (Essen, Germany)

Christian Ochsenfeld, Felix Koziol (Tuebingen, Germany)

Bilirubin:

Xiao Xia Zhu (Montreal, Canada)

Papers

Hydrogen-Bond Mediated J couplings:

Brown et al, J. Am. Chem. Soc. 124, 1152 (2002)

Brown et al, Chem. Comm. 1852 (2002)

Hexabenzocoronenes:

Brown et al, J. Am. Chem. Soc. 121, 6712 (1999)

Molecular Tweezers:

Brown et al, Angew. Chem. Int. Ed. 40, 717 (2001)

Ochsenfeld et al, Solid State NMR 22, 128 (2002)

Bilirubin:

Brown et al, J. Am. Chem. Soc. 123, 4275 (2001)

Review:

Brown et al, Chem. Rev. 101, 4125 (2001)