1

Part One Noncovalent Assemblies: Design and Synthesis

From Non-Covalent Assemblies to Molecular Machines. Edited by Jean-Pierre Sauvage and Pierre Gaspard© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimISBN: 978-3-527-32277-0

3

Introduction and Defi nition of Noncovalent Assemblies Julius Rebek Jr

It is my very pleasant duty as Session Chairman to open this Solvay Conference on Chemistry and welcome you, the participants, to “ Noncovalent Assemblies. ” It is not a very pleasant a duty to defi ne this fi eld – after all, every crystal is a self - assembly, every monolayer, membrane, vesicle and micelle is a self - assembly, and every metal – ligand interaction is also a self - assembly. In fact, at some level, every synthesis is a self - assembly. But, unfortunately, as we cannot include them all, some must be excluded. As there is no graceful way to do this, I will defi ne our work this morning arbitrarily as “ fi nite systems that persist in solution. ” Yet, even that term is unsatisfactory – although crystalline urea - based inclusion compounds and cholic acid complexes have been known for decades, they must persist at some level in solution, even though we are not yet able to analyze them on the timescales and instrumentation available today. Likewise, in this morning ’ s pres-entations we can exclude zeolites and the newer Metal Organic Frameworks, even though they demonstrate enviable functions in the solid state. I mention this in an attempt to focus and stimulate discussion on those noncovalent assemblies that do show function. The early solution assemblies which used metal – ligand interac-tions or hydrogen bonds had no apparent function – they merely fi lled space (Figure 1.1 ).

But, we shall see that function arises from the proper fi lling of space: we all know that Nature abhors a vacuum, and a price must be paid to create one. None-theless, there are rewards waiting for those can who manipulate molecules into fi xed spaces. Today, I have invited those who have taken these enormous steps, and many strides beyond the Werner coordination complexes, such that a century later we are aiming at different targets (see Figure 1.2 ). Parallel developments with hydrogen - bonded systems also moved the focus from space fi lling to function;

1

From Non-Covalent Assemblies to Molecular Machines. Edited by Jean-Pierre Sauvage and Pierre Gaspard© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimISBN: 978-3-527-32277-0

4 1 Introduction and Defi nition of Noncovalent Assemblies

Figure 1.1 Upper section. Left: A catenane self - assembled by Sauvage and coworkers [1] , using Cu as a template; Right: A schematic cartoon of a helicate with two Zn metals, as

devised by Fuhrhop and colleagues [2] in 1976. Lower section. The self - sorting series of helicates as created by Lehn and Rigault [3] , in 1988.

XX X

O

N'Zn'

Zn

N'

NN

N

N

N

N

O

O

O

O

OO

O

O

O

OO

N

N

N

N

Cu+

NN NN

X X

NN

NN

X

X

OO

= Cu+n = 0, 1, 2, 3; X = H

OO

n

X

NN

X X

NN

X X

Figure 1.2 Left: Raymond et al . ’ s [4] capsule represented schematically. A phosphine/acetone adduct was stabilized inside and isolated from the bulk solvent. More recently, iminimum ion - reactive intermediates have

been stabilized in the same capsule. Right: A cartoon of Fujita and colleagues ’ [5] “ ship - in - a - bottle ” - type synthesis of a silanol inside a capsule. Neither encapsulated product is stable outside the capsule.

Raymond (2000) Fujita (2000)

Stabilization of Reactive Species

1 Introduction and Defi nition of Noncovalent Assemblies 5

and also for rosettes (Figure 1.4 ):

Figure 1.3 The melamine/cyanuric acid hydrogen - bonding recognition pattern as adopted by Seto and Whitesides [6] , which creates a 3 : 1 assembly.

H

H

R''

R''

Br

R'' = CH2C6H4C(CH3)3

R' = CH2CH2C(CH3)3

R'

R'

R'

R'

R'

R'

Br

H

H

HHH

HH

HH

HH

H HHH H

HH

N

N

NN

NN

NNN

NN N

N

NN

N

N

N

N

N

NNN

NN

NNN

NN

N

O

O

OO

O

O

OO

O

O

O

O

O

Figure 1.4 The melamine/cyanuric acid pattern presented on calixarene platforms as a rosette discovered by Reinhoudt and coworkers [7] , that has encapsulation properties.

O

NH2 NH2

N

N N

NHN

HN

N N

NH

OO

+

2

O

O

O

O

O

O

O

O

O

O

O

O

O

O

NN

N

NN

N

N

N

N

NN

NN

NN

N

NN

N

N

N

N

N

N

N

NH

HH

H

H

HH

H

HH

H

H

H

H

H

H

H

H

H

H

H

H

O

O

O

O

O

N

N

NN

NN

N H

N

N

N

N

N

N

N

H

H

HH

H

H

H H

H

HHH

O

O

O

OO

OO

O O

NHN

O

O O

HH

N

indeed, the melamine/cyanuric acid pattern was tailored for fi nite assemblies (see Figure 1.3 ):

6 1 Introduction and Defi nition of Noncovalent Assemblies

The good news is that I have invited some of the research workers featured above – including Ken Raymond, Kimoon Kim and David Reinhoudt – to highlight their investigations and to stimulate the discussion that will be held during the second half of this session, on noncovalent assemblies.

For now, among those who have been invited, the fi rst to report their fi ndings will be Makoto Fujita. So, without any further introduction, let me turn things over to Makoto – if you don ’ t know who he is, then you have wandered into the wrong hotel room! So, fasten your seatbelts and turn off your cellphones!

Figure 1.5 Two guests encapsulated in a cucurbit[10]uril by Isaacs et al . [8] (left), and an inverted version by Kim, Isaacs and colleagues [9] (right).

while recent activity in the cucurbiturils also warrants discussion (Figure 1.5 ):

References

1 Dietrich - Buchecker , C.O. , Sauvage , J. - P. , and Kern , J. - M. ( 1984 ) J. Am. Chem. Soc. , 106 , 3043 – 3045 .

2 Struckmeier , G. , Thewalt , U. , and Fuhrhop , J.H. ( 1976 ) J. Am. Chem. Soc. , 98 , 278 .

3 Lehn , J. - M. and Rigault , A. ( 1988 ) Angew. Chem. , 100 , 1121 .

4 Dong , V.M. , Fiedler , D. , Carl , B. , Bergman , R.G. , and Raymond , K.N. ( 2006 ) J. Am. Chem. Soc. , 128 , 14464 .

5 Yoshizawa , M. , Kuskawa , T. , Fujita , M. , and Yamaguchi , K. ( 2000 ) J. Am. Chem. Soc. , 122 , 6311 – 6312 .

6 (a) Seto , C.T. and Whitesides , G.M. ( 1990 ) J. Am. Chem. Soc. , 112 , 6409 .

(b) J.P. Mathias , E.E. Simanek , C.T. Seto , G.M. Whitesides , Angew. Chem. , 1993 , 105 , 1848 – 1850 .

7 Kerckhoffs , J.M.C.A. , ten Cate , M.G.J. , Mateos - Timoneda , M.A. , van Leeuwen , F.W.B. , Snellink - Ru ë l , B. , Spek , A.L. , Kooijman , H. , Crego - Calama , M. , and Reinhoudt , D.N. ( 2005 ) J. Am. Chem. Soc. , 127 , 12697 – 12708 .

8 Huang , W. - H. , Liu , S. , Zavalij , P.Y. , and Isaacs , L. ( 2005 ) J. Am. Chem. Soc. , 127 , 16798 – 16799 .

9 Isaacs , L. , Park , S. - K. , Liu , S. , Ko , Y.H. , Selvapalam , N. , Kim , Y. , Kim , H. , Zavalij , P.Y. , Kim , G. - H. , Lee , H. - S. , and Kim , K. ( 2005 ) J. Am. Chem. Soc. , 127 , 18000 – 18001 .