1. Synthetic Molecular Motors
Gregory T. Carroll
University of Groningen
g.t.carroll@rug.nl
January 20, 2010
Dresden, Germany

2. 2
Pertinent Questions Regarding
Nanomachines
1) What can be made that looks like a machine?
2) What can the thing we made do?
3) What would be a useful function and what do we need to make
to achieve it?
7) Do nanomachines need to be based on macroscopic machines?
5) How can we overcome Brownian motion?
9) What kind of physics will govern these machines?
4) How small can it be and still function?
6) What kind of energy should be used?
8) What kind of forces will result in locomotion?

3. 3
From Macroscopic to Nanoscale Rotors
10 m 1 m 10 cm 1 cm
Chem. Comm. 2009, 1712-1714.
Alberts et al. Molecular Biology of the Cell
Bacterial Flagellar Motor
Synthetic Rotary Motor
100 nm 10 nm 1 nm

4. 4
Components and Orientation of
Rotors
Chem. Rev. 2005, 105, 1281
Azimuthal orientation Altitudinal orientation
Rotor
Stator
Axle

5. Atomic Configuration
5
J. Org. Chem. 2003, 68, 8750–8766.

6. 6
Synthetic Molecular Motors
• Molecular Rotors
• Rotary Motors
• Light-driven Rotary Motors
• Linear Motors

7. 7
Molecular Rotary Motion
Free Motion Forced Motion
Triptycenes rotate in correlated fashion

8. 8
Molecular Turnstile
J. Am Chem. Soc. 1995, 117, 10662
Rotation within a framework

9. 9
Rotary Motion in Crystals
Crystalline molecular machines – possibility to gain high packing
density of multicomponent arrays of molecules that can act in
concert, transferring forces, motion and energy from one molecule
to another along the array
1) Rotary components
2) Free volume
3) Volume-conserving motions
4) Correlated Motions
5) Self-assembly
Acc. Chem. Res. 2006, 39, 413
J. Am. Chem. Soc. 2002, 124, 2398

10. Gyroscope and Compass-inspired
Molecules
10
Framework shields rotor from
intermolecular contacts within
crystal lattice and provides
free-volume needed for
unhindered rotation within
framework
Acc. Chem. Res. 2006, 39, 413

11. 11
Attempted Molecular Ratchet
Journal of Organic Chemistry 1998, 63, 3655
2nd Law of Thermodynamics: It
is impossible for any device that
operates on a cycle to receive
heat from a single reservoir and
produce a net amount of work.ACS Nano 2009, 3, 1042
Feynman, Richard P. (1963). The Feynman Lectures on Physics, Vol. 1. Massachusetts, USA: Addison-Wesley. Chapter 46

12. 12
Rolling Motions on Surfaces

13. 13
Surface-attached Systems
Major Hurdle: Brownian Motion
Limit random motion – Confine motor at interface
Stable attachment to surface
Adsorption on surface
Long-term Goal: Show that movement of rotor
can affect motility of motor or molecule/material
in presence of motor
Interfacial Stir Bar
hn
Crowd Surfing
Molecules

14. 14
Surface attached rotors based on
thioethers
A. E. Baber, H. L. Tierney, E. C. H. Sykes ACS Nano,2008,2, 2385–2391

15. 15
Donor-acceptor Surface-bound Rotor
J. Org. Chem. 2003, 68, 5091
Movement restricted by attachment to surface through a tripod
Can external electric stimuli induce rotation of the dipolar unit?

16. 16
Surface-bound Altitudinal Rotor
X. Zheng, M. E. Mulcahy, D. Horinek, F. Galeotti, T. F. Magnera, J. Michl J. Am.Chem.Soc.,2004,126,4540

17. 17
Controlled Rotary Motion – Rotary
Molecular Motors
DEFINITION:
A rotary motor is a device
that is able to convert
energy input into controlled,
directional, rotary motion in
a continuous fashion
Energy
• Photons
• oxidation/reduction
• Chemicals
REQUIREMENTS
• Controlled Motion
• Directional Movement
• Continuous Process
• Consumption of Energy

18. Electrical or Photocontrol of the Rotary
Motion of a Metallacarborane
18
M. Frederick Hawthorne, et al. Science 303, 1849 (2004)

19. 19
Chemical Motor - 120º Rotation
Kelly, T. R. et al. Nature, 1999, 401, 150-152
O
HO
NCO
O
N
O
OOO
HO
NH2 N
O
O
O
O
HO
NH2
O
HO
NCO
COCl2
NaBH(OEt)3

20. 20
Chemical Rotor - 360º Rotation
Science, 2005, 80, 310

21. 21
Catenanes
Leigh, D.A., Wong, J.K.Y., Dehez, F., Zerbetto F. Nature, 2003, 424, 174

22. 22
Three Rings
Leigh, D.A., Wong, J.K.Y., Dehez, F., Zerbetto F. Nature, 2003, 424, 174

23. 23
Catenane Motor
Leigh, D.A., Wong, J.K.Y., Dehez, F., Zerbetto F. Nature, 2003, 424, 174

24. 24
Chemically Propelled Rotation
2 um long
500 nm long
H2O2 O2 + H2O
Si Wafer
S. Fournier-Bidoz, A.C. Arsenault, I. Manners, G.A. Ozin Chem. Commun. 2005, 441

25. 25
Molecular Rotary Motors Based on
Photo-active Overcrowded Alkenes
( P , P ) - t r a n s
M e a x
M e a x
Structural Features
• Photo-isomerizable double-bond
• Two helical halves
• Two stereogenic centers on each half
cis
trans

26. 26
Rotary Cycle
(P,P)-trans
Meax
Meax
(M,M)-cis
MeeqMeeq
> 280 nm
Meeq
Meeq
(M,M)-trans
> 280 nm
N. Koumura, R.W.J.Zijlstra, R.A. van Delden,N. Harada, B.L. Feringa, Nature 1999,401,152
D 60o
C
T1/2 (4th Step) = 233 h at 20° C
Meax Meax
(P,P)-cis
20o
C
T1/2 (2nd Step) = 32 min. at 20° C

27. 27
Ideal Unidirectional Rotation

28. 28
2nd Generation
KEY FEATURES:
X
Y
Me
H
Desired Properties
• Ability to control speed
• Functionality for attachment to surface
• Symmetric tri-cyclic lower half
• Unidirectional rotation controlled by a single stereogenic center
• The energy barriers for the thermal steps can be adjusted (X,Y)
• Distinct chemical functionalities can be introduced into the upper and lower
halves, allowing for attachment to surface and modification of properties

29. 29
Rotary Cycle
S
S
Mea x
MeO
Hg-lamp, 365 nm
5 ~ 10°C
S
S
MeO
60°C
S
S
MeO
S
S
MeO
Meeq
MeaxMeeq
60°C
Hg-lamp, 365 nm
5 ~ 10°C
(2'R)-(M)-trans-1 (2'R)-(P)-cis-2
(2'R)-(P)-trans-1 (2'R)-(M)-cis-2
ratio 14:86
ratio 89:11
T1/2 = 233 h at 20° C
(2’R)-(M)-trans-1
(2’R)-(P)-cis-2
(2’R)-(M)-cis-2
(2’R)-(P)-trans-1
-150
-100
-50
0
+50
+100
+150
250 300 350 400 450
De
l /nm

30. 30
Increasing the Speed of Rotation
hn hn
D
Energy
Rotation step
stable trans stable transstable cis
unstable
trans
D
unstable cis
Size of bridging rings
Size of substituent
at stereocenter
T1/2 = 5.74 x 10-3 s at 20° CT1/2 = 3.2 min. at 20° CT1/2 = 233 h at 20° C
Michael M. Pollard, Martin Klok, Dirk Pijper and Ben L. Feringa
Advanced FunctionalMaterials 2007,17,718-729.
Mea x
MeO
(2 'R )-(M )-tra n s-1
S
S

31. 31
A Cholesteric (Chiral) LC
Chiral Dopant:
R. Eelkema, B. L. Feringa et al., Nature 2006, 440, 163.
ee.concHTP
1
p


pitch (p)

32. 3232
(P,P)-trans (M,M)-cis
MeeqMeeq
Meax
Meax
Meax Meax
Meeq
Meeq
> 280 nm
> 380 nm
> 280 nm
> 380 nm
D 60o
C 20o
C
t0
t180 sec
R.A. van Delden, N. Koumura, N. Harada, B.L. Feringa, Proc. Nat. Acad. Sci. 2002, 99, 4945.
6.16 weight % in E7
HTPE7
69.4 mm-1
-5.0 mm-1
12.5 mm-1
Color Tuning
By Molecular Rotation in an LC

33. 33
Macroscopic Visualisation of
Rotation
hn
(P,P)-trans
(P,P)-cis
(M,M)-trans
E7

34. 34
Rotating Microscale Objects
Rienk Eelkema, et. al. Nature 2006,440,163
Texture rotation Rotation of Micro-rod

35. 35
Surface attachment - Azimuthal
D
hn
D
hn
S
OO
OO
SS
S
OO
OO
SS
S
OO
OO
SS
S
OO
OO
SS
quartzquartz
Gold
quartzquartz
Gold
quartzquartz
Gold
quartzquartz
Gold
hn
hn
D
D
( )9 ( )9 ( )9 ( )9
( )9( )9( )9( )9
CD(mdeg)
l (nm)
-3
-2
-1
0
1
2
320280240200

36. 36
Surface Attachment - Azimuthal
SiO O Si O
O
O
O
O
N
N
N
N
N
N
SiO O Si O
O
O
O
O
N
N
N
N
N
N
D
365 nm
300 400 500
0,000
0,005
0,010
Abs
nm
Stable, -20C
30 min irr, 365nm
Therm Conv
hn
hn
D
D
1.6x10
-3
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Absorbanceat439nm
40003000200010000
Time (s)
28 C
40 C

37. 37
Visualization of Rotary Motion
H. Noji, R. Yasuda, M. Yoshida, K. Kinosita Jr. Nature,1997,386,299-302
Group
Fluorescent
Group

38. 38
Molecular Motor with Extended Arm
Me
OPr
OPr
MeO2C CO2Me
N
O OEt2N
O
OPr
OPr
OPr
OPr
OPr
OPr
OPr
OPr
OPr
OPr
OPr
OPr
OPr
OPr

39. 39
39
Length of Arm
Dye for visualization with wide-field
fluorescence imaging
Two alkyne moieties for attachment of
the motor ‘stator’ to the surface

40. 40
Fluorescence on Surface
O
O
O
O
O
O
N
OPr
OPr
OEt2N
8
N
N
N N
N
N
O
Si
O
Si
O
O O
10 10
Fluorescence Wide-field Microscopy

41. 41
Towards a Nanocar?
Organic Letters 2006, 8, 1713-1716

42. 42
Linear Motors
Rotaxanes and Catenanes
Molecular components that move along pre-defined tracks
A.M. Brouwer, C. Frochot, F.G. Gatti, D.A. Leigh, L. Mottier, F. Paolucci, S. Roffia, G.W.H. Wurpel
Science 2001, 291, 2124.

43. 43
Molecular Shuttle
A.M. Brouwer, C. Frochot, F.G. Gatti, D.A. Leigh, L. Mottier, F. Paolucci, S. Roffia, G.W.H. Wurpel Science 2001, 291,
2124.

44. 44
Molecular Elevator
J.D. Badjic, V. Balzani, A. Credi, S. Silvi, J.F. Stoddart Science 2004, 303, 1845.

45. 45
Molecular Muscle
Angew. Chem. Int. Ed. 2000, 39, 3284

46. 46
Contraction

47. A nanomechanical device based on
linear molecular motors
47
Huang et al., Appl. Phys. Lett., Vol. 85, No. 22, 29 November 2004

48. 48
Combining Rotary and Linear Motion
Angew. Chem. Int. Ed. In Press