Rotaxanes are supramolecular assemblies consisting of a macrocyclic molecule threaded onto a linear molecule capped with bulky stoppers. They can be synthesized through template-directed methods like clipping, threading, and snapping. Switchable rotaxanes have applications in logic gates and memory due to their ability to shuttle between binding stations. Rotaxanes can also be used to enhance or reduce reactivity, act as molecular muscles, and self-assemble into structures that can slowly release dye.

1. Rotaxanes
Shreya Ray. Rahi Reja. Mandar Kulkarni. Surabhi Jirapuri. Prarabdha Jagdhane

2. Definition
Supramolecular assemblies consisting of macrocyclic molecules physically
threaded by, but not chemically bonded to, a linear molecule chain or a
linear subchain of a molecule capped with bulky end-groups (referred to as
“stoppers”) which prevent dethreading of cyclic molecules are known as
"rotaxanes"
Ref - Terminology and Nomenclature for Macromolecular Rotaxanes and Pseudorotaxanes, 2011 . IUPAC

3. Statistical Synthesis
6.00 % yield

4. Template-Directed Syntheses
Noncovalent forces used in templated synthesis are
1 .  acceptor - donor
2. Metal Ligand Interaction
3. Hydrogen bonding
4. Hydrophobic Interactions / cyclodextrin based template
synthesis
Clipping – Linear Guest and partial Cyclic host
complex and then end portion is “clipped” by reacting
with another molecule .

5. Template-Directed Syntheses
Threading – Formation of
pseudorotaxane first, followed by
stoppering using end bulky groups .
Snapping – linear component with
bulky terminal groups dissociates in 2
fragments and one complexes with
cyclic component , then reconstitution
of another part .
∆
Slippage – Heating of system causing
slippage of linear group with terminal
bulky groups through cyclic species .

6. Metal-Template Synthesis
Wu, C.; Lecavalier, P.R.; Shen, Y.X.; Gibson, H.W. Chem. Mater. 1991, 3, 569-572

7. Click Chemistry
C- C bond formation using
Click Chemistry
Org. Lett., Vol. 12, No. 17, 2010

8. Polyrotaxane
“Molecular Neckace”
Harada, A.; Li, J.; Kamachi, M. Nature (London, U. K.) 1992, 356,325.

9. Switchable Rotaxanes
Binding constants between wheel and each station
should be in the order: A>B>A’
The two states must be reversible
The process should be controllable by external
stimuli
Applications:
Logic Gates
NanorecordingMemory Dots
The switch may be:
Chemically Driven (Acid-Base Reaction)
Photochemically Driven (Olefin Isomerization)
Electrochemically Driven (Reduction-Oxidation
Reaction)

10. Switchable Rotaxanes

11. Bright Rotaxanes
Chem. Soc. Rev., 2010, 39, 70–80
Photoisomerisation of thread
reversibly changes fluorescent
properties of molecule.
Fluoroscence enhancement or
quenching can be used to indicate
shuttling of conformations.
High sensitivity and specificity.

12. Nanovalves
Chem. Soc. Rev., 2010, 39, 70–80
A rotaxane shuttle can serve as a molecular device to switch on a surface.
Shuttling of the macrocycle closer to and away from the pore orifices of mesoporous
silica could close and open the silica nanopores, respectively.
The lengths of the linkers determines efficiency of nanovalves.

13. Dye Delivery
Bolamphiphilic
pseudorotaxane built from
hydrophobic stoppers and
hydrophilic macrocycle.
Slow spontaneous
dissociation of reverse vesicle
can be used to slowly release
dye
Langmuir 2012, 28, 14839−14844

14. Enhanced Reactivity
Interlocked components are
forced into close proximity
 One component may sterically
protect the other from chemical
attack
Alternatively, steric strain may be
introduced, enhancing reactivity
Macrocycle contraction is
obtained by substitution: amideNH
residues form stronger H-bonds
Stopper group crowding is
achieved by shortening thread
length
Org. Lett., Vol. 12, No. 21, 2010

15. Molecular Muscle
Org. Lett., Vol. 11, No. 2, 2009
(1) Rotaxane-like Interlocked
components
(2) Fluoride-sensitive molecular
muscles: fluoride weakens N+H…O
H-bonding as compared to CH…O
H-bonding of pyridinium ions.

16. Conclusion
Rotaxanes comprise of a Macrocycle and a dumbell-shaped molecule
Rotaxanes can be prepared using template-directed synthases like clipping,
threading, snapping and slippage
Switchable Rotaxanes have many applications like logic gates, memory
dots, nanovalves
Rotaxanes can be used to reduce or enhance reactivity
Rotaxanes can be used to built molecular muscles
Rotaxanes can be used to make amphiphiles that can self-assemble and
release dye slowly