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Gregory Carroll
Stratingh Institute for Chemistry
University of Groningen
March 23, 2009
ACS National Meeting Salt Lake City
Light-driven Molecular Motors at
Interfaces
3
Rotary Motors in Biology
ATP Synthase Bacterial Flagellar Motor
Rotor: 6000- 17 000 RPM
Alberts et al. Molecular Biology of the Cell
~100 r.p.s.
4
Designing a Molecular Rotor
( P , P ) - t r a n s
M e a x
M e a x
DEFINITION:
A rotary motor is a device that is able to convert
energy input into controlled,
directional, rotary motion in
a continuous fashion
REQUIREMENTS
• Controlled Motion
• Consumption of Energy
• Directional Movement
• Continuous Process
Structural Features
• Photo-isomerizable double-bond
• Two helical halves
• Two stereogenic centers on each half
cis
trans
5
Rotary Cycle
( P , P ) - t r a n s
M e a x
M e a x
( M , M ) - c i s
M e e q M e e q
> 2 8 0 n m
M e e q
M e e q
( M , M ) - t r a n s
> 2 8 0 n m
N. Koumura, R.W.J. Zijlstra, R.A. van Delden, N. Harada, B.L. Feringa, Nature 1999, 401, 152
D 6 0 o C
T1/2 (4th Step) = 233 h at 20° C
M e a x M e a x
( P , P ) - c i s
2 0 o C
T1/2 (2nd Step) = 32 min. at 20° C
7
2nd Generation Motors
• 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
KEY FEATURES:
X
Y
Me
H
Desired Properties
• Ability to control speed
• Functionality for attachment to surface
8
Unidirectional Rotation
-150
-100
-50
0
+50
+100
+150
250 300 350 400 450
D
/nm
(2’R)-(M)-trans-1
(2’R)-(P)-cis-2
(2’R)-(M)-cis-2
(2’R)-(P)-trans-1
S
S
M e a x
M e O
H g - l a m p , 3 6 5 n m
5 ~ 1 0 ° C
S
S
M e O
6 0 ° C
S
S
M e O
S
S
M e O
M e e q
M e a x M e e q
6 0 ° C
H g - l a m p , 3 6 5 n m
5 ~ 1 0 ° C
( 2 ' R ) - ( M ) - t r a n s - 1 ( 2 ' R ) - ( P ) - c i s - 2
( 2 ' R ) - ( P ) - t r a n s - 1 ( 2 ' R ) - ( M ) - c i s - 2
r a t i o 1 4 : 8 6
r a t i o 8 9 : 1 1
T1/2 = 233 h at 20° C
9
Increasing the Speed
hn hn
D
Ene
rgy
Rotation step
stable trans stable trans stable 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° C T1/2 = 3.2 min. at 20° C T1/2 = 233 h at 20° C
S
S
M e a x
M e O
( 2 ' R ) - ( M ) - t r a n s - 1
Michael M. Pollard, Martin Klok, Dirk Pijper and Ben L. Feringa Advanced Functional Materials 2007,17, 718-729.
10
Utilizing Motor to Perform Work
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
11
Surface-bound Motors
Azimuthal orientation Altitudinal orientation
G.S. Kottas, L.I. Clarke, D. Horinek, J. Michl , Chemical Reviews 2005, 105, 1281-1376
Need two-legged attachment to prevent
rotation around single bond.
12
Unidirectional rotation on Au nanoparticles
-38
-37.8
-37.6
-37.4
-37.2
-37
-36.8
-36.6
-36.4
0.0028 0.00285 0.0029 0.00295 0.003 0.00305 0.0031
1/T (K-1)
ln (
(k h
) /
(k B
T))
nanoparticles
parent motor
t1/2 = 198 h
t1/2 = 93 h
0 2 4 6 8 -20
-10
0
10
20
30
CD
(md
eg
)
hn>280 nm hn365 nm hn365 nm hn365 nm D D D D
CD signal at 280 nm
through 2 rotary cycles
14
quartz
Thin gold surfaces
Au Vapour deposition
200 400 600 800 10000.0
0.2
0.4
0.6
ab
so
rba
nce
(a
.u.)
wavelength (nm)
5 nm gold
5 nm gold
quartz
quartz
OH OH OH OH OH OHO O
Si
NH2
O OSi
NH2
O OSi
NH2
O OSi
NH2
O OSi
NH2
O OSi
NH2
1) H2SO4 / H2O2
2)
O OSi
NH2
Transparent Gold Surface
15
Self-assembled monolayer of molecular motors
Dense SAM
Dilute SAM
No change upon irradiation
quartz quartz
5 nm gold 5 nm gold
10:1
Decanethiol:motor
SO
O
O
O
SS
S
OOO
O
SS
S
OO
OO
S S
S
O
O
OO
SS
SO
O
O
O
SS
S
O
O
OO
SS
S
OO
OO
SS
S
O OO
O
SS
Au Nanoparticles
16
Increasing the length of the legs
• Motors function with longer tethers to gold
surface, but suffer from some quenching by
the gold.
• Results in longer irradiation times
9 9 9 9
9 9 9 9
17
Grafting Motor to Quartz
M. M. Pollard, M. Lubonska, P. Rudolf, B.L. Feringa, Angewandte Chemie Int. Ed. 2007, 46, 1278-1280
19
Altitudinal Motor on Surface
XX
• Store for extended periods without degradation or polymerization
• Motor should be stable for complete characterization prior to surface modification
• Reliable and reproducible surface modification
• Monolayer
New Strategy for Functionalization of Quartz, SiO2/Si and mica
• Difficulty introducing acid chloride into legs of some motors
• Acid chloride moisture sensitive and therefore characterization prior to surface
modification is limited
• amino silane surfaces not easy to control
Limitations of Previous Method
20
Interfacial 1,3 Dipolar Cycloaddition
H R2
Cu-cat. N NNR1
R2H
NR1 N N
T. Lummerstorfer, H. Hoffmann
Journal of Physical Chemistry B 2004, 108, 3963-3966
R R'
Hartmuth C. Kolb, M. G. Finn, and K. Barry Sharpless
Angewandte Chemie International Edition 2001, 40, 2004-2021
Mixed monolayers on Au Monolayers on SiO2/Si wafer
Magnetic Nanoparticles
J. P. Collman, N. K. Devaraj,
C. E. D. Chidsey Langmuir 2004, 20, 1051-1053
M. A. White, J. A. Johnson, J. T. Koberstein, N. J. Turro
Journal of the American Chemical Society 2006, 128, 11356-11357
21
Solution-phase
365 nm
OR
OR
OR
OR
DO
O
O
O
stable unstable stable
t1/2 = 1.5 min (20oC)
D‡G° = 83.5 kJ/mol
R = (CH2)2OCH2CCH
300 400 500
0,0
0,1
0,2
0,3
0,4
0,5
Ab
so
rba
nc
e (
a.u
.)
Wavelenght (nm)
Stable, MeOH, -20C
60 min irrad, 365nm
300 400 500
-50
0
50
100
D
Wavelenght (nm)
Stable, MeOH, -20C
90 min irrad, 365 nm
UV-Vis Absorbance
CD
3:1 ratio at
photostationary state
G. London, G. T. Carroll, T. Fernández Landaluce, M. M. Pollard,
P. Rudolf and B. L. Feringa, Chemical Communications, 2009, 1712
22
Azide-SAM Formation
SiO O Si O Si O
N3 N3 N3SiO O Si O Si O
OH OH OH
SiO
OO
11CH2
Br
SiO
OO
11CH2
N3
NaN3
Cyclohexane/THF
H2O/H+
H2O Contact Angle: 73±3
Ellipsometric Thickness: 0.7 ±0.1 nm
Method 2 (Self-assembly in toluene) Method 1 (Hydrolysis in THF,
Self-assembly in cyclohexane)
H2O Contact Angle: 82±1
Ellipsometric Thickness: 1.8 ±0.1 nm
CH2
ATR IR
cm-1
1.5
1.0
0.5
x1
0-3
3000 2900 2800 2700 2600
1.5
1.0
0.5
x1
0-3
2200 2150 2100 2050 2000
Ab
s
390392394396398400402404406408410 In
ten
sit
y (
Arb
. U
nit
s)
Binding Energy (eV)
N1s
X-ray Photo-electron Spectroscopy (XPS)
Azide 2095 cm-1
No photochemical degradation after 24 hrs irradiation
90%
23
Motor-monolayer formation
800
600
400
200
x1
0-6
2120 2100 2080 2060
Azide, 2095 cm-1 FT-IR
H2O Contact Angle decreases: 67±2º
Ellipsometric thickness increases: 2.9 ±0.1 nm
390392394396398400402404406408410
Motor monolayer
Azide monolayerXPS
In
ten
sit
y (
Arb
. U
nit
s)
Binding Energy (eV)
XPS
Azide
Triazole
No Cu or Na found in XPS survey
nm
8
6
4
2
0
x10
-3
460440420400380360340320300
Unmodified Quartz
Without Copper
Ab
so
rba
nce
Motor
SiO O Si O Si O
OO
OO
N3 N3 N3
SiO O Si O
O
O
O
O
N
N
N
N
NN
CuSO4*5H2O (2 %)Na-ascorbate (10%)
DMF, rt, 12h
2% Cu(SO4)
10% NaAsc DMF
24
Rotary Motion on Surface
SiO O Si O
O
O
O
O
N
N
N
N
NN
SiO O Si O
O
O
O
O
N
N
N
N
NN
D
365 nm
300 400 500
0,000
0,005
0,010
Ab
s
nm
Stable, -20C
30 min irr, 365nm
Therm Conv
1.6x10-3
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Ab
so
rba
nce
at 43
9 n
m
40003000200010000
Time (s)
28 C 40 C
28⁰C
40⁰C
Thermal step affected by confinement in monolayer
Two processes occurring?
T1/2 1st step: 3 minutes
T1/2 2nd step: 21 minutes
Decay at 439 nm
25
SEM
OO
O O
O
N
SiO
O
N
SiO
O
NN
NN
O
1111
H2O, H+
THF
OO
O O
N
Si
N
SiOH
NN
NN
1111
HO3
3
Silane-modified Motor
cyclohexane
Insoluble precipitate begins to form after
approximately 10 min.
Ellipsometric Thickness: 77±8 nm H2O Contact Angle: 79 ±3
Robust Faint Yellow Film
0.14
0.13
0.12
0.11
0.10
0.09
Ab
so
rba
nce
at
43
9 n
m
25x103
20151050
Time (s)
0.4
0.3
0.2
0.1
Ab
s
550500450400350
nm
60 min. 1 min. Pre-irradiation 28 h
Very slow thermal recovery
clearly demonstrates effect of
crowding on speed
26
250 300 350 400 450 500 550
0.0
0.2
0.4
0.6
0.8
1.0
Ab
so
rba
nc
e (
au
)
Wavelength (nm)
Stable, -20C, MeOH
PSS, 365nm
t1/2 (20oC)= 50 s (in MeOH)
The reverse reaction analogue
OHO
O
HOON3
O
N31. Mesyl-ClCHCl2, 2h, rt
2. NaN3 DMF
5h, 55oC.
63 %
SiO O Si O Si O
OO
NH NH NH
O
O
O
O
O
O
N3N3
SiO O Si O Si O
NH NH NH
O
O
O
O
O
O
NN
N
NN
N
OO
CuSO4*5H2O (2 %)Na-ascorbate (10%)
DMF, rt, 12h
8
6
4
2
0
x1
0-3
550500450400350
Ellipsometric Thickness: 0.8 ±0.1 nm H2O Contact Angle: 74 ± 10°
Ellipsometric Thickness: 1.9 ±0.1 nm H2O Contact Angle: 57 ±1°
Alkyne Surface
27
Two-legged Attachment
390392394396398400402404406408410
Motor monolayer
Azide monolayerXPS
In
ten
sit
y (
Arb
. U
nit
s)
Binding Energy (eV)
XPS
Azide
Triazole
S i O O S i O S i O
N H N H N H
O
O
O
O
O
O
N N
N
N N
N
O O
SiO O Si O Si O
NH NH NH
O
O
O
O
O
O
N3 NN
N
OO
410 405 400 395 390
Inte
ns
ity
(A
rb.
Un
its
)
Binding Energy (eV)
N1s
XPS after
reaction
1.4
1.2
1.0
0.8
0.6
0.4
0.2
x1
0-3
3000 2900 2800 2700 2600 2500 2400
1.4
1.2
1.0
0.8
0.6
0.4
0.2
x1
0-3
2300 2250 2200 2150 2100 2050 2000
ATR IR
No Azide
28 H. Noji, R. Yasuda, M. Yoshida, K. Kinosita Jr. Nature, 1997, 386, 299-302
Visualization of Rotary Motion
Group Fluorescent
Group
29
Fast Motor on Surface
Choice of motor:
Me
Br
MeO2C CO2Me
Coupling to the arm
Coupling to the surface
› Fast Motor against Brownian storm
(t1/2 nanoseconds)
0.8
0.6
0.4
0.2
0.0
DA
800700600500400
Wavelength (nm)
Increment: 1 nsFrames: 98Accumulations: 50t0: 233203 nsT: 22.3 deg C
Prof. Fred Brouwer (Universiteit Van Amsterdam)
Rotation too fast to be measured using classical
techniques (CD, UV or NMR experiments)
O S i
O O S i
O O
N N
9 9
N N
N N
M e
O
O
O
O
Quartz
10
8
6
4
2
0
x10
-3
440420400380360340320300280
nm
Cu, Azide SAM Lower Coverage Cu, Unmodified Quartz Azide SAM, No Cu Cu, Azide SAM Higher Covarage
H2O Contact Angle: 65±2 Ellipsometric Thickness: 1.8 ±0.1 nm
30
Me
OPr
OPr
MeO2C CO2Me
N
O OEt2N
O
OPr
OPr
OPr
OPr
OPr
OPr
OPr
OPr
OPr
OPr
OPr
OPr
OPr
OPr
Target Molecule
Dr. Jerome Vachon
Considered to be relatively rigid structure
solubility
Converted to alkynes
31
Length of Arm
Dye for visualization with wide-field
fluorescence imaging
Two alkyne moieties for attachment of
the motor ‘stator’ to the surface
32
O
Si
OO
Si
OO
N3 N3
9 9
Quartz
Attachment to Surface
Cu2SO4 (1 mol%)Sodium Ascorbate (5 mol%)DMF
c ~ 10-8 M
O
O
O
O
O
O
N
OPr
OPr
OEt2N
8
NN
N NN
N
O
SiO
Si
OO O
10 10
33
O
O
O
O
O
O
N
OPr
OPr
OEt2N
8
NN
N NN
N
O
SiO
Si
OO O
10 10
Wide-field Microscopy
Filippo Lusitani University of Groningen
Fluorescence on Surface
34
A Cholesteric (Chiral) LC
Chiral Dopant:
R. Eelkema, B. L. Feringa et al., Nature 2006, 440, 163.
ee.concHTP
1p
pitch (p)
35
Rotating Micro-scale Objects
Rienk Eelkema, et. al. Nature 2006, 440, 163
Texture Rotation Rotation of Micro-rod
36
Motor-functionalized Polymers
O
N
N
O O
OO
C6H13H13C6
6H17C8C8H17H17C8
* *
x y z
X : Y : Z = 10 : 11 : 1
No changes upon irradiation
hn hn
37
Motor-terminated Polymer
Control over Helical
twist of single poly
(hexyl isocyanate)
macromolecule
D. Pijper et al, Angew. Chem. Int. Ed.,2007, 46, 3693.
Stiff helical conformations
Racemic P / M helicity (fast
dynamic equilibrium)
Subtle chiral influence can induce large preference for one helical sense: