supramolecular chemistry 1 - concepts

Supramolecular Chemistry

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Supramolecular Chemistry 1 - Concepts.pdf Supramolecular Chemistry 2 - Cation binding.pdf Supramolecular Chemistry 3 - Binding of anions.pdf Supramolecular Chemistry 4 - Neutral molecules.pdf Supramolecular Chemistry 5 - Methods.pdf Supramolecular Chemistry 6 - Self-Assembly.pdf Supramolecular Chemistry 7 - Artificial enzyms.pdf Supramolecular Chemistry 8 - Molecular Devices.pdf Supramolecular Chemistry 9 - Molecular Machines.pdf Supramolecular Chemistry 10 - New.pdf

Supramolecular Chemistry

Steed, J. W.; Atwood, J. L. Supramolecular Chemistry,Wiley 2000 $ 40,-

Balzani, V.; Venturi, M.; Credi, A.Molecular Devices and MachinesWiley VCH 2003

Schneider, H.-J.; Yatsimirski, A. Principles and Methods in Supramolecular ChemistryWiley 2000 39,95

Comprehensive Supramolecular Chemistry, Vol. 1-10; Lehn, J.-M., Series editor, Pergamon/Elsevier Oxford etc, 1996 $ 425 per volume

Encyclopedia of Supramolecular Chemistryedited by Jerry L. Atwood and Jonathan W. SteedDekker, 2004 1,500 pages $489.00

What is Supramolecular Chemistry?

MULTIDISCIPLINARY FIELD

NATURE (biological systems) - inspiration

ORGANIC and INORGANIC CHEMISTRY building blocks(supramolecular synthons)

PHYSICAL CHEMISTRY methods to study and understand their properties


The ultimate supramolecular material?

Held together by many specific hydrogen bonds, - stacking, etc.

Encodes gigabytes of data Can Self-Replicate Built-in Error Correction Information Storage Is the basis of life


Tobacco Mosaic Virus (TMV)


Actin-Myosin Complex


Kinesin Crawling Along a Microtubule


MOLECULAR CHEMISTRY covalent bonds formation

SUPRAMOLECULAR CHEMISTRY non-covalent bond formation


J. M. Lehn:Supramolecular chemistry is the chemistry of the intermolecular bond, covering the structures and functions of the entities formed by the association of two or more chemical species

F. Vgtle:In contrast to molecular chemistry, which is predominantly basedupon the covalent bonding of atoms, supramolecular chemistry is based upon intermolecular interactions, i.e. on the association of two or more building blocks, which are held together by intermolecular bond


But also:

Molecular Devices Supramolecular Photochemistry Electronic Switches Dendrimers


Top-Down (current technology). Continued reduction in size of bulk semiconductor devices optical, ultra-violet, ion-beam, electron-beam lithography

Bottom-Up (molecular scale electronics). Design of molecules with specific electronic function Design of molecules for self-assembly into supramolecular structures Connecting molecules to the macroscopic world Man-made synthesis (e.g. carbon nanotubes)


1-50 nm 1-500 nm

SupramolecularAggregates

Nanoelectronicsnanobiology

Development - History

Classification of Host-Guest Compounds


Spherand

Corpora non agunt nisi fixata

Receptors and the Lock and Key Analogy

The Chelate and Macrocyclic Effects

The Chelate and Macrocyclic Effects

Less entropically favorable

Stabilization offered by the chelate effect

Preorganization and Complementarity

Nature of Supramolecular Interactions

Covalent bond energies:

C-O bond 340kJ / mol 1.43C-C bond 360kJ / mol 1.53C-H bond 430kJ / mol 1.11C=C bond 600kJ / mol 1.33C=O bond 690kJ / mol 1.21

Compared to most non-covalent interactions these are: Very high energies Very short distances Highly dependant on orientation


Driving Forces for the Formation of Supramolecular Structures

hydrophobic interaction


Ion - Ion Interactions

Can be a very strong bond - even stronger then covalent bonds in some cases.

Can be an attractive or a repulsive force.

Non-directional force

Long range (1/r)

Highly dependant on the dielectric constant of the medium


IonIonIonIon InteractionsInteractions

Energy = (k * z1 * z2 * e2) / ( r12)

k = 1 / 4o= Coulomb constant = 9*109Nm2/C2

e = elementary charge = 1.6*10-19C

= dielectric constant

r12 = meters between the objects

The energy of an ion-ion interaction only falls of at a rate proportional to 1 / r. Therefore these are very long range forces.


IonIonIonIon InteractionsInteractions

1 nm in water?

1 nm in Chloroform?

Energy = (k * z1 * z2 * e2) / ( r12)

= 9*109 * 1 * -1 * (1.6*10-19)2 / 78.5 * 1 * 10-9= -2.3 * 10 -28 / 0.8 * 10 -7= -29.4 * 10-22 J= -1.77 kJ / mole (-0.42 kcal / mole)

= 9*109 * 1 * -1 * (1.6*10-19)2 / 4.8 * 1 * 10-9= -2.3 * 10 -28 / 4.8 * 10-9= -4.79 * 10-20 J= -28.8 kJ / mole (-6.89 kcal / mole) -> 8% of a C-C bond


Energy = -(k * Q * u * cos / e * r2) If = zero= -k * Q * u / e * r2= -9*109 * 1.6*10-19 * 2.9 * 3.336 *10-30 / e * r2= -1.39 * 10-38 / 4.8 * (10-9)2= -2.9 * 10-21 J= -1.75kJ / mole

Example: Acetone pointing directly at Na ion ( = zero) at a distance of 1nm (in chloroform)

IonIon--Dipole InteractionDipole Interaction

u = q * l (dipole moment)l = length of the dipoleq = partial charge on dipoler = distance from charge to center of dipoleQ = charge on ion


IonIon--Dipole InteractionDipole Interaction

Directional forces

Can be attractive or repulsive

Medium range (1/r2)

Significantly weaker then ion-ion interactions

Nature of Supramolecular Interactions :Hydrogen Bonding


Van der Waals radius of H: 1.1, O 1.5. Therefore closest approach should be 2.6.

Actual separation is about 1 less!Distance of 1.76.

Intermediate between vdw distance and typical O-H covalent bond of 0.96.

O H OR

R H

O H OR

R H

Nature of Supramolecular Interactions :Halogen Bonding

Halogen atoms iodine, bromine, chlorine and even fluorine can function as Lewis acids and engage in electron donor-acceptor interactions with atoms with lone pairs such as nitrogen, oxygen, phosphorus and sulfur.

BIX- Halogen bonding may involve dihalogenes X2 and X-Y as well as

organic halides

The strength of the donor-acceptor interaction depends on the polarizability of the halogen atom, decreases in the order:

I > Br > Cl (> F)

Nature of Supramolecular Interactions :Halogen Bonding

DMSO to haloarene halogen bonding geometry:

head on to C-X, ~ 158(13) (Cl), 162(12)(Br), and ~165(8)(I);

side on to S=O, : 125-135.

Increase of polarity of the both C-X and S=O bond increases the strength of interaction:

Nature of Supramolecular Interactions :The Cation pipipipi Interaction

Nature of Supramolecular Interactions :pi pi pi pi pipipipi Stacking

Nature of Supramolecular Interactions :pi pi pi pi pipipipi Interactions

Chem. Rev. 2000,100, 4145-4185.

Nature of Supramolecular Interactions :Charge-Transfer Complex

Nature of Supramolecular Interactions :Van der Waals Forces

Strength of interaction is essentially a function of the surface area of contact. The larger the surface area the stronger the interaction will be.

Regardless of other interactions found within a complex there will almost always be a contribution from vdw.

This is what drives molecules to eliminate spaces or vacuums and makes it difficult to engineer porous or hollow structures and gives rise to the phrase Nature abhors a vacuum.

Nature of Supramolecular Interactions :Van der Waals Forces

Nature of Supramolecular Interactions :CLOSE PACKING IN THE SOLID STATE

Conformers allowing maximum intermolecular interactions, even very weak (which do not play a role in solution)

Empty space: crystal pores and channels -> inclusion crystals

TETRIS analogy

Nature of Supramolecular Interactions :Hydrophobic Effects

supramolecular chemistry 1 - concepts

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