What is Supramolecular Chemistry

"Supramolecular chemistry is the chemistry of the intermolecular bond,covering the structures and functions of the entities formed by theassociation of two or more chemical species"

J.-M- Lehn

"In contrast to molecular chemistry, which is predominantly based uponthe covalent bonding of atoms, supramolecular chemistry is based uponintermolecular interactions, i.e. on the association of two or morebuilding blocks, which are held together by intermolecular bonds"

F. Vögtle

"Supramolecular chemistry is defined as chemistry "beyond themolecule", as chemistry of tailor-shaped inter-molecular interaction. In'supramolecules' information is stored in the form of structuralpeculiarities. Moreover, not only the combined action of molecules iscalled supramolecular, but also the combined action of characteristicparts of one and the same molecule.

F. Vögtle

Literature

Supramolecular Chemistry. Concepts and perspectives.

J.-M Lehn.

VCH, Weinheim, 1995

Supramolecular Chemistry. An introduction.

F. Vögtle

Wiley, Chichester, 1993.

Comprehensive Supramolecular Chemistry, 12 Volumes

Ed. J.-M. Lehn

Pergamon, Oxford, 1996.

Lecture Notes and Overheads

Chemistry Intranet

You can collect copies of the overheads as .pdf files that canbe read in Acrobat Reader from my Public folder.

Backbone E

Computer

Folder "Public" This folder has guest access.

Subfolder VTB Then choose the appropriate lecture

Supra- versus SupermolecularChemistry

One point to address concerns the use of the words supramolecular andsuper-molecule. The concept of supramolecular chemistry has become aunifying attractor, in which areas that have developed independentlyhave spontaneously found their place. The word "supramolecular" hasbeen used in particular for large multi-protein architectures andorganized molecular assemblies. On the other hand, in theoreticalchemistry, the computational procedure that treats molecularassociations such as the water dimer as a single entity is termed the"supermolecule" approach. Taking into account the existence and theindependent uses of these two words, one may then propose that"supramolecular chemistry" be the broader term, concerning thechemistry of all types of supramolecular entities from the well-definedsupermolecules to extended, more or less organized, polymolecularassociations. The term "supermolecular chemistry" would be restrictedto the specific chemistry of the supermolecules themselves.

Supramolecular chemistry may then be divided into two broad, partiallyoverlapping areas concerning: (1) supermolecules, well-defined, discreteoligomolecular species that result from the intermolecular assocation ofa few components (a receptor and its substrate(s)) following a built-in"Aufbau" scheme based on the principles of molecular recognition; (2)supramolecular assemblies, polymolecular entities that result from thespontaneous association of a large undefined number of components intoa specific phase having more or less well-defined microscopicorganization and macroscopic characteristics depending on its nature(such as films, layers, membranes, vesicles, micelles, mesomorphicphases, solid state structures, etc.).

J.-M- Lehn

What does non-covalent mean?

Two electron, two centre bonds?

C-H, C-C, C=C etc.Covalent

Delacalised bonding?

Benzene, boranes, carboranes etc.Covalent

Hydrogen bonding?

O—H...H, N—H...O, H—F...H etc.?

Donor-acceptor (coordination) bonding?

F3B.NMe3, [Fe(H2O)6]2+ etc

?

Just large molecules?

Acetyltransferase

Vitamin B12

Just large molecules?

Taxol

C70 C60

Supramolecules

K

K-18-Crown-6

(5'-(*CGCGAATTCGCG)-3') duplex complex with 4'-6-diamidine-2-phenyl indole

Electrostatic interactions

+ –

+ +

– –

+ +

– –

+

–

Unselective ion pairing of singly charged species

Relatively unselective interaction between a polycation and monoanions

Selective interactions between a complementary polycation and a polyanion

Highly selective interaction between two ions with another complementary intermolecular interaction

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Ionic interactions in practice

• Growth of ionic crystals

• Protein-protein interactions

N

S

N

S

N

S

N

S

N

S

•

S S S S S

•

O O

Ionic interactions in combination

With metal-ligand interactions

O O

With metal-ligand and hydrophobicinteractions

Au

–O O

Au

– –

Al2O3

In the absence of other interactions thelong range structure is only twodimensional

The energies involved may be quite small

Functionalisation may be difficult becauseother interactions associated with the siteof functionality may be favoured

Hydrophobic interactions

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Host-guest interactions —or making a hole and filling it

Hydrogen-bonding

Interaction is of intermediate strength,but weaker than a covalent bond.

Interaction is directional

Three dimensional structures may readily be assembled by hydrogen bonding

As the interaction is weaker than covalentbonding it may be reversed (Error correction)

Assembly is often fast and specific

Advantages

Chemists think they understand H-bonding

Disadvantages

They probably don't

NN

HN

OR

O

NN

NH

H

H N

N

R

H

NN

HO

OR

N

NN

H N

N

G

R

Hydrogen-bonding

T A

H

C

Literature - dendrimers

Dendritic Molecules. Concepts. Syntheses. Perspectives.

G.R. Newkome, C.N. Moorefield, F. Vögtle.

VCH, Weinheim, 1996

Dendrimers.

Ed. F. Vögtle

Topics Curr. Chem., 1998, 197

Dendrimers

Also known as

Arborols

Cascadols

Cauliflower polymers

Crowned arborols

Dendrimers

Molecular fractals

Polycules

Silvanols

Starburst™ dendrimers

A Dendrimer

Concepts of generations and cores

Flory

Synthesis

X

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Y XY

Y

X X X

Y

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XX X

Y

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Y Y

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YX

X

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XX

YXY

Y

XXX

Y

X XX

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XX

Y

X

YY

Convergent synthesis

X

X

X

XY

Y

Y

Y

Divergent Synthesis

X

X

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XXX

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Y

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Cascade synthesis - the beginning

F. Vögtle et al. Synthesis, 1978, 155

Extension to diamine cores

F. Vögtle et al. Synthesis, 1978, 155

And out to the fifth generation

Recl. Trav. Chim. Pays-Bas, 1994, 113, 573

The first patented dendrimer

Denkewalter et al., 1981 U.S. Pat., 4,289,872

• Chiral• Amino acid based• Protection methodology

The first of Tomalia's starburst™dendrimers

D.A. Tomalia et al., Angew. Chem. Int. Ed. Engl., 1990, 29 ,138

Surface decoration

Vögtle-type 5th generation nitrile reduced to fifth generationamine.

64 surface amino groups

Decorated with an amino acid

Meijer et al., Science, 1994, 266, 1226

Tomalia's PAMAM dendrimers

P o ly am ido am ine = PAMAMD.A. Tomalia et al., Polym. J., 1985, 17, 117;Macromolecules, 1986, 19, 2466

Aldrich Catalogue 1999

Connectivity [2], ester based

D.M. Haddleton et al., J. Chem. Soc., Chem. Commun., 1994,2445

A dendritic inhibitor of InfluenzaVirus A haemaglutinin

R. Roy et al., J. Chem. Soc., Chem. Commun., 1993, 1869

A series without heteroatoms

J. Veciana et al., J. Am. Chem. Soc., 1993, 115, 57

Polyradicals

A nonaradical

Silicon-based systems

D. Seyferth et al., Organometall ics, 1994, 13, 2682

Phosphorus analogues of aminosystems

D.L. DuBois et al., Inorg. Chem., 1994, 33, 5482

The Majoral System

J.-P- Majoral et al., Angew. Chem. Int. Ed. Engl., 1994, 33,1589