supramolecular approaches to artificial molecular machines · 2006-12-19 · supramolecular...

ICMR-JNCASR Winter School Bangalore - December 2006

Dr Martin Grossel

Supramolecular Approaches to Artificial Molecular Machines

School of ChemistryUniversity of SouthamptonUK

Functional Supramolecular Materials?

Applications of SupramolecularChemistry to Materials Science


Structure of Talk

• Introduction – What is a molecular-scale machine

• Simple Supramolecular devices – Catenanes and Rotaxanes

• π-Complex-based catenane and rotaxane assemblies

• Metal ion-templated catenane and rotaxane assemblies

• Hydrogen bond-templated catenane and rotaxane assemblies

<http://www.nanorex.com/>


Supramolecular Chemistry is the Chemistry of molecular assemblies.

In one of his key early reviews exploring the concepts of SupramolecularChemistry Jean-Marie Lehn noted that one of its main goals was the creation of fumctional molecular assemblies capable of:

• Recognition

• Transport

• Modification of substrates

J.-M.Lehn, “Supramolecular Chemistry. Concepts and Perspectives”, VCH (1995), ISBN 3-527-29312-4.


Supramolecular assemblies can be:

• Dynamic (internal motions etc)• Switchable (mechanically, optically, etc.)• Can change size and shape• Can be chiral

Each of these properties has potential applications in Materials Science


Supramolecular assemblies can be:

• Dynamic (internal motions etc)• Switchable (mechanically, optically, etc.)• Can change size and shape• Can be chiral

Each of these properties has potential applications in Materials Science

In this lecture I will focus mainly on the potential uses ofCatenanes and rotaxanes.

What constitutes a machine?

A Macroscopic Machine:

“An apparatus for applying mechanical power; having several partseach with a definite function.”

From: Oxford English Dictionary





A machine is characterised by:

• the type(s) of energy required to make it work (heat, light, electrons)







• the type(s) of movements performed by its components (need large amplitude changes)








• the manner by which its operation can be monitored and controlled (electrochemistry,

Uv-visible spectroscopy, etc.)










• the possibility to repeat the operation at will and to establish a cyclic process (lifetime,

stability)











stability)

• the timescale needed to complete a cycle of operation (nuclear motions to secs)











stability)

• the timescale needed to complete a cycle of operation (nuclear motions to secs)

• the function(s) performed by the machine (problem of controlling direction of motion)

Why make molecular-scale machines?

Richard Feynman (1959)

“What would be the utility of such machines? Who knows? I cannot see exactly what would happen, but I can hardly doubt that when we have some control of the arrangements of things on a molecular scale we will get an enormously greater range of possible properties that substances can have, and of different things that we can do.”

From: “There is plenty of room at the bottom”, Eng. Sci., 1960, 23, 22-36; Saturday Rev., 1960, 43, 45-47.

What constitutes a molecular-scale machine?

Definition of a molecular scale machine

“A discrete assembly of molecular components designed to perform mechanical movements (output) as a consequence of appropriate external stimulae (input).”

See: V. Balzani, A. Credi, F. M.Raymo, and J. F. Stoddart, Angew Chem. Int. Ed., 2000, 39, 3348-3391.


Design Options:

Photons and electrons are the best energy inputs:

• good for both reading and writing

• no problems with chemical by-products

• use optical spectroscopy or electrochemistry


Design Options:

Photons and electrons are the best energy inputs:

• good for both reading and writing

• no problems with chemical by-products

• use optical spectroscopy or electrochemistry

Photons – need a chromophore

Electrons – need a change of redox/charge state (use electrochemistry)

These avoid the problem of chemical by-products and need for continual

supply of reagents.

Supramolecular assemblies are more likely to undergo larger amplitude

changes in shape etc. than intramolecular changes (conformational etc.)

Functional Supramolecular Systems


Molecular Logic Gates – an AND gate

See: A. P. de Silva, H.Q.N. Gunaratne, and C P. McCoy, J. Amer. Chem. Soc., 1997, 119, 7891-7891.

NR2

O

O O

O

O

Protonation site

R = Et, O

binding siteNa+


Molecular Logic Gates – an AND gate

See: A. P. de Silva, H.Q.N. Gunaratne, and C P. McCoy, J. Amer. Chem. Soc., 1997, 119, 7891-7891.

Design features:

• Anthracene fluorophore attached to

two PET-active groups (one binds Na+;

other H+).

• If neither or only ONE complexed,

fluorescence is quenched

• If BOTH are complexed, no PET

occurs and fluorescence is observed

NR2

O

O O

O

O

Protonation site

R = Et, O

binding siteNa+

PET = photo-induced electron transfer

Catenanes and Rotaxanes

For an introduction see for example: M. C. T. Fyfe, and J. F. Stoddart, Acc. Chem. Res., 1997, 30, 393-41.


Catenanes

A [2]-Catenane


Rotaxanes

Ring

Stopper

ThreadMovieA two-station [2]-Rotaxane


Pseudorotaxanes

A Pseudorotaxanane


Synthetic strategies

(i) Catenanes (ii) Rotaxanes

Stoddart’s Machines

J. F. Stoddart(UCLA)


Stoddart’s Machines


Stoddart’s Machines – the molecular abacus


Stoddart’s Machines – Muscle mimics


For many years catenanes (and rotaxanes) were a synthetic curiosity.

Stoddart developed efficient routes to such structures using non-covalent interactions, e.g.:

• π−π association• C-H•••π contacts• C-H•••O interactions

Stoddart’s Machines – synthetic routes

Molecular ComplexationBy Crown Ethers

See: J. F. Stoddart, Pure Appl. Chem., 1988, 60, 467-472.

Paraquat2+ complexes with Dibenzo-34-crown-10

Paraquat complex

See: J. F. Stoddart, Pure Appl. Chem., 1988, 60, 467-472.

Intermolecular Contacts in Paraquat2+ - Crown Complexes

ΔG(complexation) = 16.3 kJ mol-1

Stoddart’s Catenane Synthesis

First attempted Box Synthesis

12%

2PF6̄

NH PF4 6

H O2

Δ

then

OMe

OMe

MeCN+

++

+

4PF6̄

4PF6̄

OMe

+

++

+

OMe

Br Br

N

N

N

N+ +

Reversing the roles of the electron-rich and electron-deficient units

First attempted Catenane Synthesis

O

O

O

OO

O

O O

O

O

70%

O

O

O

OO

O

O O

O

O

2PF6̄

Ambient TemperatureMeCN 3PF6̄

threading≡

NH PF4 6

H O2

O

O

O

OO

O

O O

O

O

+

++3PF6̄

..

Br

4PF6̄

O

O

O

OO

O

O O

O

O

+

+

+

+

Br Br

+ +

N

N

N

N

+

+

..

+

Br

Dynamic Processes in 2-Catenanes

4PF6̄

+

+

+

+

O

O

O

OO

O

O O

O

O

4PF6̄

+

+

+

+

O

O

O

OO

O

O O

O

O

4PF6̄

+

+

+

+

O

O

O

OO

O

O O

O

O

4PF6̄

+

+

+

+

O

O

O

OO

O

O O

O

O

Routes to [3]-Catenanes

BrBr

N N

N N: :

++

O O O O O

OOOOO

O O O O O

OOOOO

O O O O O

N N

N N

++

++

OOOOO OOOOO

O O O O O

Expanding the Paraquat4+ Box leads to [3]-Catenanes

Crowns rotate through box at ca 8000 Hz at 298K (increased rate perhaps a reflection of hydroquinone ring repulsion)

oreither

The Molecular Train Set

O

O

O

O

O

O

OOO

O

O OO

O

O

O

O

O

O O

4+

O

O

O

O

O

O

OOO

O

O OO

O

O

O

O

O

O O

4+

O

O

O

O

O

O

OOO

O

O O

O

O

O

O

O

O

O O

4+

O

O

O

O

O

O

OOO

O

O O

O

O

O

O

O

O

O O

4+Box rolls through crown at ca 28000 times/sec at 298K and hops around from station at 300 times/sec

4PF6̄

O

O

O

OO

+

+

+

+

O

O O

O

O

O

O

O

O

OO

O

O

O

O

The Molecular Train Set

Paraquat4+ boxes chase each other around the ring, hopping at ca. 500 times/sec and always keeping one station apart.

O

O

O

O

O

O

OOO

O

O O

O

O

O

O

O

O

O O

4+4+

O

O

O

O

O

O

OOO

O

O O

O

O

O

O

O

O

O O

4+

4+

O

O

O

O

O

O

O

OO

O

O O

O

O

O

O

O

O

O O

4+

4+

O

O

O

O

O

O

OOO

O

O O

O

O

O

O

O

O

O O

4+ 4+

4PF6̄

O

O

O

OO

+

+

+

+

O

O

O

O

OO

O

O

O

O

O

O

O

OO

+

+

+

4PF6̄

Catenane-based Machines

Colour-Switching Catenanes

See: J. F. Stoddart et al, Angew. Chem. Int. Edn., 1998,37,333; C. P. Collier et al, Science, 2000, 289, 1172.

A Redox-switchable Catenane


See: C. P. Collier et al, Science, 2000, 289, 1172=1175.

A Redox-switchable Catenane

TTF/PQT4+ complex is green1,5-Dialkoxynaphthalene/PQT4+ complex is red


Tuning PQT4+ complex colours

λmax (nm)

4+

333 473 677601494 854

red greenblue

S

S

S

S

R

R

OMe

OMe

OMe

OMe

NHMe

MeNH

NHMe

MeNH

F

F

NHMe

MeNH

F F

FF

weakest complex strongest complex

See: W.-Q. Deng, A. H. Flood, J. F. Stoddart, and W. A. Goddard III, J. Amer. Chem. Soc., 2005, 127, 15994-15995.


See: W.-Q. Deng, A. H. Flood, J. F. Stoddart, and W. A. Goddard III, J. Amer. Chem. Soc., 2005, 127, 15994-15995.

Approaches to display devices – an RGB dye

Rotaxanes

Rotaxanes and PseudorotaxanesFirst Rotaxane Synthesis

14%

O

O

O

O

+

+

+

+4PF6̄

O

O

O

O

+

BrBr

+N

N N

N

++

O

O

(iPr) SiO3

O

O

OOSi(iPr)3

O

Rotaxanes and PseudorotaxanesPseudorotaxane Synthesis - a simple PQT4+ box preparation

+

O

O

HO

O

OOH

BrBr

+

4PF¯

N+

N+

N+

N+

6

O

O

OH

+

+

+

+4PF6̄

HO

O

O

NH PF¯/H O4 6 2+ 2,6-lutidine

i-PrSiOTfMeCN

Distribute betweenDCM and water

DCM

Water

O

O

O

+

+

+

+O

O

O

4PF6̄

N

N N

N

++

Self-Assembling (Pseudo)rotaxanes

N

N

+

+

N

N

+

+

4PF6̄

O

O OO

O

+

+

+

+OO O

O

O OO

O

OO

O

O

O

O O O

O

O

O

Muscle Mimics

Rotaxane-based Machines - Muscles

See: Yi Liu et al: J. Amer. Chem. Soc, 2005, 127, 9745-9759.

A Redox-switchable Rotaxane


A Redox-switchable “Palindromic” Rotaxane

TPR8+


Change in dimensions between TPR8+

and its oxidised form TPR12+


Random coating on Au-coated felixible microcantileverbeams 500 x 500 x 1 μm with a monolayer of ca 6 billion rotaxane units


Cycling of TPR8+ using sequential chemical oxidation (FeIII) and reduction (ascorbic acid)



Cycling of reference compound (no PQT4+ ring and tethered through stoppers)

Cycling of TPR8+ using sequential chemical oxidation (FeIII) and reduction (ascorbic acid)

Can be cycled more than 25 times


Using Metal-ion Templates

J.-P. Sauvage(Strasbourg)

Catenanes and RotaxanesSauvage’s strategy

N

N

≡

-

See: D. J. Cardenas, A. Livoreil, and J. – P. Sauvage, J. Amer. Chem. Soc.., 1996, 118, 11980-11981.

Catenanes and RotaxanesSauvage’s catenane synthesis

N

N

OH

OH

Cs2CO3

DMF

N

N

O

O

O

O

O

O

N

N

N

N

O

O

O

O

O

O

HO

HO

Cu+Cu+

A

A

X = Br, I

O

O

O

O

X

X

N

N

O

O

-

-

CuI binds tetrahedrallywith two BiPyunits.


O

O

O

O

O

O

N

N

O

O

O

O

N

N

O

O

KCN

(demetallation)

O

O

O

O

N

N

N

N

O

O

O

O

O

O

O

O

Cu+

O

O

O

O

X

X

Cs2CO3

DMF

N

N

N

N

O

O

O

O

O

O

HO

HO

Cu++


O

O

O

O

O

O

N

N

O

O

O

O

N

N

O

O

O

O

O

O

N

N

N

N

O

O

O

O

O

O

O

O

Cu+

Rotary Motors

A Catenane-based Motor

See: A. Livoreil, C. O. Dietrich-Buchecker, and J. –P. Sauvage, J. Amer. Chem. Soc., 1994, 116, 9399; see also D. J. Cardenas, A. Livoreil, and J. – P. Sauvage, J. Amer. Chem. Soc.., 1996, 118, 11980-11981 for a three-state system.

Metal complex-based Rotaxanes

For a review see: M.-J. Blanco, M. C. Jiminez, J.-C. Chambron, V. Heitz, M. Linke, and J. – P. Sauvage, Chem. Soc., Rev., 1999, 28, 293-305.

Metal-complex-based Rotaxanes

Redox-controlled Molecular Shuttles

See: J. –P. Collin, P. Gavana, and J. –P. Sauvage, New J. Chem., 1997, 21, 525.

Multiply-entwined Catenanes- Knotanes (Knots)

J.-P. Sauvage

Sauvage’s catenane synthesis

Multiply-interlocked catenanes are chiral

Multiply-entwined Catenanes

See: J. J. Nierengarten, C. O. Dietrich-Buchecker, and J. – P. Sauvage, J. Amer. Chem. Soc.., 1994, 116, 375-376.

R = (CH2)6N N

N N

N NR R

O

O O O O

O

OO

RR

N N

N N

HO

RR N N

OH

N N

N N

N N

O

O O O O

O

OO

= Cu+

R = (CH2)6

OHHO

N N

N N

N NR R

Multiply-entwined CatenanesSauvage’s Knots (Knotanes)

R RR R

N N

N N

N N

N N

O

N N

N N

OO O O

O O

O

O

O O O O

O

OO

OO O O

OX XO

RR

N N

N N

HO

RR N N

OH

N N

N N

N N

O

O O O O

O

OO

+

KCN=demetallation

Cs CO / DMF2 3

Yields: 2% doubly wound catenane (= knotane)1% singly wound catenane+ lots of Macrocycle


R RR R

N N

N N

N N

N N

O

N N

N N

OO O O

O O

O

O

O O O O

O

OO

OO O O

OX XO

RR

N N

N N

HO

RR N N

OH

N N

N N

N N

O

O O O O

O

OO

+

KCN=demetallation

Cs CO / DMF2 3


(Cu Complex)

Borromean Rings

J. F. Stoddart

Borromean Knots

What are Borromean Rings?

Multiply-entwined CatenanesStoddart’s Borromean Rings

See: K. S. Chichak et al., Science , 2004, 304, 1308 -1312.

The analysis:


See: A. J. Peters et al., Chem. Commun. , 2005,3394-3396.

The strategy:

O ON

N

N

N

N

N

O O

XX

N N

N N

exo-receptor

endo-receptor


See: A. J. Peters et al., Chem. Commun. , 2005,3394-3396.

Zn2+

N N

NH2H2N

O O

N

The chemistry:

Conditions: Zn(OAc)2 / iPrOH / 70°C / 24 hCondensation gives the Borromean ring in > 95% yield


See: A. J. Peters et al., Chem. Commun. , 2005,3394-3396.For chiral Borromeates see: C. D. Pentecost et al, Angew. Chem. Int. Edn., 2006, 45, 4099-4104.


See: K. S. Chichak et al., Science , 2004, 304, 1308 -1312.

**

Hydrogen-bonded Catenane Assembly

For an introductory overview see: R. Jäger and F Vögtle, Angew. Chem. Int. Edn., 1997, 36, 930-944.

H-Bonded Catenane Synthesis

C. J. Hunter(Sheffield)

Hunter’s Benzoquinone Receptor

O

ON

H

N

H

O

ON

H

N

H

O O

HH

H H

C-H--- ContactπSee: C. J. Hunter, Chem. Soc. Rev., 1994, 101.

Hunter’s First Catenane SynthesisH N 2NH2

O

O

NH

NHNH

NH

2

2

CH Cl2 2

Et N3

A B

AX

X

X

B

A

A

B

A

A+ +

+

O O

Cl Cl

X

O O

Cl Cl

A

B

B, X = CHC, X = N

DimerTetramer Catenane

See: C. J. Hunter, Chem. Soc. Rev., 1994, 101.

Rel. yields: (high dilution)10% : 51% : 34%

Hunter’s First Catenane Synthesis

From Catenanes to Knotanes

F. Vögtle(Bonn)

Vögtle’s Knotane Synthesis

H N 2NH2

O

O

NH

NHN

H

NH

2

2

OCl

OCl

O

N

O

NH

NHNH

N

H2

2

OCl

O

Cl

NO

Cl

O

Cl

O

Cl

O

Cl

N

Cyclic monomerCyclic dimerCyclic oligomers

Knotane

(ca 50%)(ca 20%)(ca 2%)

Knotane(ca 20%)

See: O. Lukin and F. Vögtle et al, Angew. Chem. Int. Edn., 2005, 44, 1456-1477.

(trimerises)

Knotanes

Vögtle’s Knots - 1

See: F. Vögtle <http://www.chemie,uni-bonn.de/oc/ak_vo/ >

Knotanes

Vögtle’s Knots - 2

Vögtle’s Knotanes

See: O. Lukin and F. Vögtle et al, Angew. Chem. Int. Edn., 2005, 44, 1456-1477.

Ammonium salt-based Rotaxanes

J. F. Stoddart

Ammonium Complexes with Crown Ethers

+ +

+ +H

H HN

NH

+

+

HN

H

+

+

+

O

O

O

O

O

O

O

ODB24C8

Dibenzo-24-crown-8

Pseudorotaxane formation

+NH2

O

O O O

O

O O

OOO

+NH2

Front Side



O

O

O

OO

O

O O

O

O

+

≡ ≡

NH2+

H2N+

NH2+


An Interwoven Supramolecular Cage

Rotaxane-based Machines

Plugs and Sockets

Plugs and Sockets

Turning on a light (Balzani)

See: E. Ishow et al, Chem. Eu. J., 1999, 5, 984-989.

O O

O O

O O

O

RN

H

Acid (R = Me)

Base

R N

H

H

+

O O

O O

O O

O

hν

h 'ν

+

energytransfer


Plugs and Sockets

N.B. Chloride ions can impede rotaxaneformation here of competitive hydrogen-bonding in the dialkylammonium hydrochloride. (see: M. Montalti and L. Prodi, Chem Comm., 1998, 1461)

Valves – 1

Rotaxane-based Machines - Valves

See: T. D. Nguyen et al, Proc. Natl. Acad. Sci., 2005, 102, 10029-10034; Org. Lett., 2006, 8, 3383-3366

(EtO)3Si N C O

HO O

N

OBut F

N

H

O

O FO OBut

N

SiO

O

O

SiO

O

ON C O

+

+

TFA (deprotect amine)

N

H

O

O F

NH H

+

SiO

O

O

Rotaxane attached to surface of MCM-41


O ON

Me

Me

Me

Base

N

H

O

O F

N

HSi

OO

O +

O ON

Me

Me

Me

N

H

O

O

NH H

+

SiO

O

OF

N

H

O

O F

NH H

+

SiO

O

O

O ON

Me

Me

Me

(1) (2)O

O


O

O

O

O

O

ODB24C8=

See: T. D. Nguyen et al, Proc. Natl. Acad. Sci., 2005, 102, 10029-10034; Org. Lett., 2006, 8, 3383-3366

HMPT

DIPEA

TEA

Most basic/least crowded

Least basic/most crowdedMost efficient release of dye occurs with the most basic and least stericallyhindered base


Valves - 2

Rotaxane-based Machines – The Valve

See: T. D. Nguyen et al, Proc. Natl. Acad. Sci., 2005, 102, 10029-10034.

The Elevator

Rotaxane-based Machines – The Elevator

O

O

O

O

+

+

H

NN

N

O

O

O

O

+ Acid + Base

O

O

O

OH H

N

N

N+

+

+

O

O

O

O

See: J. D. Badjic et al: Science, 2004, 303, 1845.


Vertical distance moved by platform is ca 0.7nm (generating a force of ca 200 pN – ca. 1 order of magnitude larger than that generated in natural linear motors like myosin or kinesin)

Catenanes and Rotaxanes made easy!

D. A. Leigh(Edinburgh)

Leigh’s Molecular-scale Machinery

Hydrogen-bonded Catenanes and Rotaxanes

Leigh’s First Catenane Synthesis

OCl

OCl H N

NH2

2

CHCl , NEt , CO3 3 2

ON

HN

H

O

ON

H

ON

H

OCO

N

H

N

H

O

OO

OO

NH HNO

HN

O

NHO

NH

NH

A.G.Johnston, D.A.Leigh, R.J.Prichard, and M.D.Deegan, Angew. Chem. Int Ed., 1995, 34, 1209-1212A.G.Johnston, D.A.Leigh, L.Nezhat, J.P.Smart, and M.D.Deegan, Angew. Chem. Int. Ed., 1995, 34, 1212-1216

Leigh’s Linear Motor

The Components

D. A. Leigh et al, Nature Materials, 2005, 4, 704

N+

N+

O O

OO

NH

NH

NH

NH

H

H

(CH2)8

F F

FF

O

N

H

N

H O

N

H

O

O

N

H

(CH2)8

F F

FF

O

N

H

N

H O OO N

H

N

H

The shuttle

The fumaramide thread

The maleamide thread


The Rotaxane


O

Cl Cl

N

ONH2

NH2

(CH2)8

F F

FF

O

N

H

N

H O

N

H

O

O

N

H

Ph

Ph

O

O

R

N

H

N

O

HN

O

H

N

H

O

NH

O

NH

+

+

65%

Et N3

CHCl3


Switching the Rotaxane


O

N

H

HN O

Ph

Ph

(CH2)8

Ph

Ph

F F

FF

O

N

H

N

H O

Ph

Ph

N

H

O

O

N

H

(CH2)8

Ph

Ph

F F

FF

O

N

H

N

H O

254 nm

5 min50%

CH Cl2 2

115°CCHCl CHCl2 224 h90%

Δhν

50:50 mixture at photoequilibrium


Switching a Rotaxane-based coating


Au

OOH

SS

OOH




On a 12° slope a drop of diiodomethanecan move up about 1.38mm.

Nanovehicles

J. M. Tour(Rice)

Nanovehicles

Nanocars

see: J. M. Tour et al, Chem..Soc. Rev., 2006, 35, 1043-1055

Rotary Motors

A Biaryl-based rotary motor

Feringa et al.

Nanovehicles

Nanocars

see: J. M. Tour et al, Chem..Soc. Rev., 2006, 35, 1043-1055

Conclusions

• Organic chemists have now produced a wide variety of promising machine-like structures

• Lateral thinking and wide-ranging collaborations are now required to develop this area.

The End

supramolecular approaches to artificial molecular machines · 2006-12-19 · supramolecular...

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