1. Molecular Machines: Delving
into the world of
Supramolecular Chemistry
Shreesha .V. Bhat
3rd Sem, Dept of Medicinal Chemistry
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2. Contents
1. Molecular Machines – Introduction
2. Supramolecular Chemistry and Mechanical Bon
3. Catenanes and rotaxanes
- Introduction
- Synthesis
- Molecular Shuttling
4. Applications
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3. Molecular machines
What is a molecular machine?
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4. 4

5. Molecular Machines
What is a molecular machine?
“An assembly of a discrete number of molecular
components designed to perform mechanical-like
movements as a consequence of appropriate
external stimuli”
Angew. Chem. Int. Ed. 2000, 39, 3348-3391.
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6. Natural Molecular Machines-
Biomotors
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7. Artificial Molecular Motors
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8. Artificial Molecular Motors
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9. Supramolecular Chemistry
Molecular Machines
Supramolecular Chemistry Macromolecules
Non-covalent Interactions
Mechanical Bond
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10. Mechanical Bond
Non-covalent interactions
Mainly observed in mechanically intertwined
molecules like catenanes and rotaxanes.
Each component is intrinsically linked to the
other resulting in a mechanical bond which
prevents dissociation without cleavage of one or
more covalent bonds.
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11. 11

12. 12

13. James Bond- Sir Fraser
Stoddart
Third most cited chemist with more than 14,000
citations
Has trained more than 300 Ph.Ds and postdoctorates 13

14. Catenanes and Rotaxanes
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15. Catenanes and Rotaxanes
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16. 16

17. Construction of Rotaxanes
and Catenanes
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18. DNA Catenanes & Rotaxanes
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19. Synthesis of Catenanes and
Rotaxanes
1) Active template Strategy
 Hydrophobic Interactions
 Hydrogen Bonding
 Metal ligand co-ordination
 π donor- π acceptor interaction
2) Click Chemistry
3) Ring Closing Metathesis
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20. First Synthesis of Catenanes and
Rotaxanes
•Solely based on statistical probability
•Molecules were allowed to self-assemble
•Less than 1 % yield
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21. How can we make complex
efficiently?
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22. Template Effects for efficient
synthesis
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23. Template Effects for efficient
synthesis
1) Hydrogen Bonding
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24. Template Effects for efficient
synthesis
2) Metal Co-ordination
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25. Template Effects for efficient
synthesis
3) Hydrophobic Interactions
Chem. Lett. 1996,503-504 25

26. Template Effects for efficient
synthesis
Cyclodextrins (CDs) are cyclic oligosaccharides consisting of six
or more α-1,4-linked D-glucopyranose rings.
 The conformation of CDs is a rigid, well-defined cavity with a
conical shape.
 They have a Hydrophilic exterior, Hydrophobic Interior
The binding interaction is based on a summation of weak effects,
namely Van der Waals interactions and hydrophobic binding.
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27. Template Effects for efficient
synthesis
4) π – donor π- acceptor Interactions
PNAS, 104, 2007, 234 27

28. 28

29. Click Chemistry As an Approach for
Catenane/ Rotaxane synthesis
1,2,3 triazole
Click Chemistry is the chemistry tailored to generate
substances quickly and reliably by joining units together.
It is a modular reaction which gives very high yields and
has high atom economy
Azide Alkyne Cycloaddition using Copper as a catalyst is
one of the widely used click reactions
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30. Click Chemistry
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31. 31

32. End Capping by Click Reactions
J. AM. CHEM. SOC. 2006, 128, 10388-10390
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33. Synthesis of macrocycle
Bis-p-phenylene-34-crown -10(BPP34C10)
Tetrahedron, 57, 2001, 3799-3808 33

34. Catenane Synthesis
BPPC34C10 dvts Bipyridinium Cyclophane Catenanes
Tetrahedron, 57, 2001, 3799-3808
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35. Functions- Molecular Switches
and Molecular Shuttles
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36. Incorporation of different
stations for switching
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37. Molecular Shuttling
External Stimuli
1)Chemical-Acid-
Base
2) Photochemical
3) Electrochemical-
Redox
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38. Principle Behind Shuttling
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39. External Stimuli for Switching
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40. Chemically Driven Stimuli
JACS 1998, 120, 11932-11942. 40

41. Photochemically Driven
Switches
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42. Photochemically Driven
Switches
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43. Applications in Drug Delivery
Macroscopic Transporters
NanoElevators
Nano Valves
Molecular Rotors
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44. Macroscopic Transport by
synthetic Molecular Machines
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45. Tetraflourosuccinamide Maleamide station
station
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48. 48

49. 49

50. Implications
Liquid transportation using photo-responsive
surfaces may prove useful for delivering
analytes in lab-on-a-chip environments,
Performing chemical reactions on a tiny
scale without reaction vessels by bringing
individual drops containing different reactants
together.
In the Future, maybe you can move solid
objects just through a Laser Pointer!!!!!
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51. Molecular Elevator
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52. Molecular Elevator
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53. MSNP- Mesoporous Silica
Nanoparticles -Targeted Drug
Delivery
Nanoscale, 2009, 1, 16–39 53

54. In Step 1, the CBPQT4+ rings encircles the TTF units, constitutes the open position of
the MSNPs and allows the cargo molecules to be loaded.
In Step 2, the nanovalves are closed by oxidizing the TTF units with Fe(ClO4)3 to the
TTF2+ dications and as a consequence of Coulombic repulsion, the tetracationic
CBPQT4+ rings move to the DNP units.
In Steps 3 and 4, the nanovalves are opened by reducing the dications back to the
neutral TTF units whereupon the CBPQT4+ rings move back to the TTF units, thus
releasing the cargo 54

55. Conclusions
The Beauty of Supramolecular Chemistry, with its
Interlocked molecules converts a Chemist into an
Artist who delves into the world of catenanes and
rotaxanes.
Synthetic Molecular Machines have really wide
applications in the field of electronics, sensors and
drug delivery.
The Molecular shuttling mechanisms of rotaxanes
have wide implications in targeted drug delivery,
and can be explored further.
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http://www.catenane.net/home/linksnew.h

57. Acknowledgements
My Sincere thanks to Mr. Mohit Tyagi (Phd Scholar)
for introducing me to this wonderful topic, and
answering my innocent questions with great
patience.
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58. Thank You
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59. QUIZ
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