Post on 16-Apr-2017
Heat Engine
Electric Motor ATP Synthase
http://galileo.phys.virginia.edu/classes/152.mf1i.spring02/CarnotEngine.pdf Elston, T.; Wang, H.; Oster, G. Nature, 1998, 391, 510.
Motors From Man-Made Scale to Molecular Scale: Similar Designs from Nature
Macroscopic Scale Molecular Scale
Synthetic Molecular Motors: Energy-Directed Conformational (Configurational) Motion
Balzani, V.; Credi, A.; Raymo, F. M.; Stoddart, J. F. Angew. Chem. Int. Ed. 2000, 39, 3348.
Conformer A
Conformer X Conformer B
……
(1) Consumption of Energy
(3) Unidirectional and Repetitive Motion
(2) A Series of Chemical Transformation
Chemical-Driven Rotary Molecular MotorsThe chemical reaction is mechanically coupled to movement and force is directly generated to move the motor forward.
1 Triptycyl Helicene
2 Biary Lactone
First Prototype of Synthetic Motors Based on Triptycyl Helicene
Kelly, T. R.; Silva, H. D.; Silva, R. A. Nature, 1999, 401, 150.
The Idea of Design From A Molecular Brake
Bowyer, M. C.; Bhaskar, K. V. et al. Kelly, T. R. J. Am. Chem. Soc. 1994, 116, 3657.
Chemically Powered Bond RotationBond Rotation Barrier 20-25 kcal·mol-1
Kelly, T. R.; Silva, H. D.; Silva, R. A. Nature, 1999, 401, 150.
Controlled 120° Bond Rotation in Triptycyl Helicene Derivatives
Kelly, T. R.; Silva, H. D.; Silva, R. A. Nature, 1999, 401, 150.
Requirements on Structure to Achieve 360° Continuous Rotation
• Each blade of the triptycene must be attached an amino group.
• A good chemoselectivity is required for phosgene delivery to the
amine “firing position”.
• Successful 120° rotation of the triptycene should be brought by
the phosgene-fueled formation of an intramolecular urethane.
• The urethane has to be cleaved to allow subsequent repetition of
preceding rotation.
Cai, X.; Damkaci, F. et al. Kelly, T. R. J. Am. Chem. Soc. 2007, 129, 376.
DMAP Induced in Rotating Motor
Cai, X.; Damkaci, F. et al. Kelly, T. R. J. Am. Chem. Soc. 2007, 129, 376.
Proposed Process of 360° Rotation
Cai, X.; Damkaci, F. et al. Kelly, T. R. J. Am. Chem. Soc. 2007, 129, 376.
Unexpected Products from Quenching by Methanol
Cai, X.; Damkaci, F. et al. Kelly, T. R. J. Am. Chem. Soc. 2007, 129, 376.
Selective Mono-Acylation via Less Reactive Surrogate for Phosgene
Cai, X.; Damkaci, F. et al. Kelly, T. R. J. Am. Chem. Soc. 2007, 129, 376.
mono-acylated motor1,1’-carbonyldiimidazole
Failure of Staab Equilibrium in Motors
Cai, X.; Damkaci, F. et al. Kelly, T. R. J. Am. Chem. Soc. 2007, 129, 376.
Trifloroacetyl Protection to Give Monoamine
Cai, X.; Damkaci, F. et al. Kelly, T. R. J. Am. Chem. Soc. 2007, 129, 376.
Reasons for Failure to Form UrethaneBürgi-Dunitz intervention
Markey, M. D.; Kelly, T. R. Tetrahedron, 2008, 64, 8381.
Stability of Cyclic Acylpyridinium Salt
Unchanged in MeOH at 100 ℃ for 19 h
Markey, M. D.; Kelly, T. R. Tetrahedron, 2008, 64, 8381.
Possible Modification to Interfere with the Resonance of DMAP Unit
Markey, M. D.; Kelly, T. R. Tetrahedron, 2008, 64, 8381.
Comments on Triptycene-system Motors
• Successful 120° clockwise bond rota6on, but failed in 360° repeated
rota6on with the existence of DMAP unit
• Phosgene fuel was too reac6ve to give a selec6ve acyla6on of amine
proximate to “firring posi6on”
• The stable acylpyridinium salt from DMAP and isocyanate impeded
the forma6on of urethane to give con6nuous rota6on
Unidirectional Bond Rotary of Biaryl Lactone from Diastereoselective Ring-Opening
However, the rapid equilibrium of diastereomerization scrambles the direction of bond rotationDahl, B. J.; Branchaud, B. P. Tetrahedron Lett. 2004, 45, 9599.
exo face aIack�
180° Bond Rotation of Bifunctional Biaryl Lactone Derivatives
M axial
Dahl, B. J.; Branchaud, B. P. Org. Lett. 2006, 8, 5841.
360° Rotation of Achiral Biaryl Lactone
Fletcher, S. P.; Dumur, F.; Pollard, M. M.; Feringa, B. L. Science, 2005, 310, 80.
Summary of Chemical-Driven Molecular Motors
l Unidirectional rotation is controlled by chemical interaction.
l Chemoselectivity is the main challenge in multifunctionl motors.
l The chemical accumulation may contaminate the system.
Fletcher, S. P.; Dumur, F.; Pollard, M. M.; Feringa, B. L. Science, 2005, 310, 80.
Light-Driven Rotary Molecular Motors
Light-Driven Molecular Motors
Mechanism of Motor Rotation
Structure Modification
Motor-Controlled LC Reorganization
Motor-Controlled Asymmetric Catalysis
Photochemical and Thermal isomerization of Overcrowded Biphenanthrylidenes
Koumura, N.; Zijlstra, R. W. J. et al. Feringa, B. L. Nature, 1999, 401, 152.
Mechanism of Motor Rotation
Light-Driven Molecular Motors
Mechanism of Motor Rotation
Structure Modification
Motor-Controlled LC Reorganization
Motor-Controlled Asymmetric Catalysis
Energy Diagram of Rota0on Cycle
Pollard, M. M.; Klok, M.; Pijper, D.; Feringa, B. L. Adv. Funct. Mater. 2007, 17, 718.
Structure Analysis of Overcrowded Alkenes
1.341 Å
1.347 Å
111.22°
122.76°123.18°
ter Wiel, M. K. J.; van Delden, R. A.; Meetsma, A.; Feringa, B. L. J. Am. Chem. Soc. 2005, 127, 14208.
Steric Interaction in Thermal Helix Inversion
Steric interactions in the fjord region
Pollard, M. M.; Klok, M.; Pijper, D.; Feringa, B. L. Adv. Funct. Mater. 2007, 17, 718.
Ultraviolet and Circular Dichroism Spectra to Lable Motor 1
Koumura, N.; Zijlstra, R. W. J. et al. Feringa, B. L. Nature, 1999, 401, 152.
Unexpected Changes of i-Propyl-Substituted Motors in Photochemical Process
solid dotted
ter Wiel, M. K. J.; van Delden, R. A.; Meetsma, A.; Feringa, B. L. J. Am. Chem. Soc. 2005, 127, 14208.
Thermal Helix Inversion Monitored by NMR
ter Wiel, M. K. J.; van Delden, R. A.; Meetsma, A.; Feringa, B. L. J. Am. Chem. Soc. 2005, 127, 14208.
Rotary Cycle of i-Propyl-Substituted Motors
ter Wiel, M. K. J.; van Delden, R. A.; Meetsma, A.; Feringa, B. L. J. Am. Chem. Soc. 2005, 127, 14208.
Rate Acceleration by Structure Modification
Light-Driven Molecular Motors
Mechanism of Motor Rotation
Structure Modification
Motor-Controlled LC Reorganization
Motor-Controlled Asymmetric Catalysis
Possible Ways to Improve the Motors
• Accelerating the rate of rotation to control the unidirectional motion
by overcoming the “Brownian storm” from molecular collision and
vibration.
• Functionalization to allow incorporation with more complex
molecular structure, able to be involved in certain chemical process.
Pollard, M. M.; Klok, M.; Pijper, D.; Feringa, B. L. Adv. Funct. Mater. 2007, 17, 718. Pollard, M. M.; Meetsma, A.; Feringa, B. L. Org. Biomol. Chem. 2008, 6, 507.
Rotation Acceleration with Five-Membered Ring Systems
ter Wiel, M. K. J.; van Delden, R. A.; Meetsma, A.; Feringa, B. L. J. Am. Chem. Soc. 2003, 125, 15076. Pollard, M. M.; Meetsma, A.; Feringa, B. L. Org. Biomol. Chem. 2008, 6, 507.
The thermal helix conversion is the rate-determined step in bond rotation.
Rotation Cycle of Five-Membered Ring Motors
1.4 h 4.2 h
ter Wiel, M. K. J.; van Delden, R. A.; Meetsma, A.; Feringa, B. L. J. Am. Chem. Soc. 2003, 125, 15076.
Half-time of Thermal Helix Conversion
Molecular Motors
Cis-isomer helix conv.
Trans-isomer helix conv.
Overall Process
1 32 min 439 h 2 ~20 ha
2A 18 min 317 h 3 74 min 18 s 40 min4 >36 hb 1.2 sc
a. 50% conversion at 110 ℃ monitored by 1H-NMR;b. 20 min at 60 ℃;c. at -20 ℃.ter Wiel, M. K. J.; van Delden, R. A.; Meetsma, A.; Feringa, B. L. J. Am. Chem. Soc. 2005, 127, 14208. Pollard, M. M.; Meetsma, A.; Feringa, B. L. Org. Biomol. Chem. 2008, 6, 507.
Energy Barrier of Thermal Helix Conversion
Molecular Motors
Cis-isomer helix conv. ΔG(kJ·mol-1)
Trans-isomer helix conv. ΔG(kJ·mol-1)
1 91 1072 124, 131a
2A 91 1073 95 844 101 71
a. the conversion contains two steps.ter Wiel, M. K. J.; van Delden, R. A.; Meetsma, A.; Feringa, B. L. J. Am. Chem. Soc. 2005, 127, 14208. Pollard, M. M.; Meetsma, A.; Feringa, B. L. Org. Biomol. Chem. 2008, 6, 507.
Structure Analysis of Cis- and Trans-isomers with Five-membered Ring
ter Wiel, M. K. J.; van Delden, R. A.; Meetsma, A.; Feringa, B. L. J. Am. Chem. Soc. 2003, 125, 15076.
1.352 Å104.6°
1.350 Å104.1°
Design of Second Generation Light-Driven Rotary Motors
Rotor
Stator
Koumura, N.; Geertsema, E. M. et al. Feringa B. L. J. Am. Chem. Soc. 2002, 124, 5037.
Tuning the Speed of Rotary Motion of Motors with Symmetric Lower Moieties
Motor Energy Barrier (kJ·mol-1) Half-time (h) Photochemistry
Ratio
6 105.2 184 8:927 105.6 215 13:878 100.5 26.3 23:779 110.1 1283 23:77
10 106.0 233 8:9211 91.8 0.67 1:9912 94.4 2.01 1:9913 102.7 60.1 25:75
Koumura, N.; Geertsema, E. M. et al. Feringa B. L. J. Am. Chem. Soc. 2002, 124, 5037.
Second Generation Motors with Fused Five Membered Ring System
Motor Energy Barrier (kJ·mol-1) Half-time (s) Photochemistry
Ratio15A 88 587 25:75
15B 85 190 14:86
15C 84 95 11:89
15D 60 5.73x10-3 12:88
16 79 15 33:67
17 38 5.74x10-7 a NAa. 2.3 h at 115 K
Vicario, J.; Walko, M.; Meetsma, A.; Feringa B. L. J. Am. Chem. Soc. 2006, 128, 5127. Kulago, A. A.; Mes, E. M. et al. Feringa B. L. J. Org. Chem. 2010, 75, 666.
Summary: Steric Effect on Half-time of Thermal Helix Conversion
• Ground state energy of unstable isomers depends on the geometry of overcrowded alkenes
• Increasing the size of substituents makes the isomers with pseudo-equatorial substituents more sterically strained.
• Less steric interaction at fjord region gives large decrease of energy barrier. Motors with fused five membered ring have a released space in the fjord region for trans-isomer, but even more crowded for cis-isomers.
• The second generation motors are able to reduce the energy barrier significantly by changing the bridging atoms.
Vicario, J.; Walko, M.; Meetsma, A.; Feringa B. L. J. Am. Chem. Soc. 2006, 128, 5127.
Light-Driven Molecular Motors
Mechanism of Motor Rotation
Structure Modification
Motor-Controlled LC Reorganization
Motor-Controlled Asymmetric Catalysis
Rotational Reorganization of Liquid Crystalline Films Induced by Doped Molecular Motors
Rod Rotation on the Doped Cholesteric LC Film: Observed Helix Twisting Power of Motors
liquid crystal with embedded molecular motor
glass rod (28 µm)Eelkema, R.; Pollard, M. M. et al. Feringa B. L. J. Am. Chem. Soc. 2006, 128, 14397.
Possible Mechanism of Rotational Reorganization of LC Films
𝑝= [𝛽 ∙𝑐 ∙(𝑒𝑒)]↑−1 p – the pitch of cholesteric liquid crystalls; β – the HTP of the dopant; c – the concentration of the dopant;
Eelkema, R.; Pollard, M. M. et al. Feringa B. L. J. Am. Chem. Soc. 2006, 128, 14397.
AFM Images of Corrugated LC Film Surface
Eelkema, R.; Pollard, M. M. et al. Feringa B. L. J. Am. Chem. Soc. 2006, 128, 14397.
Helical Polymer Functionalized Molecular Motors: Light-Controlled Helicity in LC Phase
Pijper, D.; Jongejan, M. G. M.; Meetsma, A.; Feringa B. L. J. Am. Chem. Soc. 2008, 130, 4541
molecular chirality
macromolecular chirality
Supramolecular chirality
Full Photocontrol of Supramolecular Helicity in LC Phase
(2’S)-‐(P)-‐18-‐PHIC (2’S)-‐(M)-‐18-‐PHIC
Pijper, D.; Jongejan, M. G. M.; Meetsma, A.; Feringa B. L. J. Am. Chem. Soc. 2008, 130, 4541
Molecular Motors in Asymmetric Reac0on
Light-Driven Molecular Motors
Mechanism of Motor Rotation
Structure Modification
Motor-Controlled LC Reorganization
Motor-Controlled Asymmetric Catalysis
Previous Work on Bifunctional Organocatalyst
Okino, T.; Hoashi, Y.; Takemoto, Y. J. Am. Chem. Soc. 2003, 125, 12672. Rana, N. K.; Selvakumar, S.; Singh, V. K. J. Org. Chem. 2010, 75, 2089.
Bifunctional Motor Catalyzed Michael Addition(P,P)-trans-18 R/S = 51/49 �
(M,M)-cis-18 R/S= 25/75 �
(P,P)-cis-18 R/S = 77/23 �
Wang, J.; Feringa, B. L. Science, 2011, 331, 1429.
Comments on Motors as Asymmetric Catalysts
• The light-driven rotary molecular motors may be a useful tool in
developing new asymmetric catalysis systems.
• The bifunctional molecular motors shown significant
stereochemical interplay based on the geometry of transition state
in Michael addition.
• There is a long way to improve the stereoselectivity and more
reactions are going to be explored.