Supramolecular Chemistry 6 - Self-assemblyhomepage.univie.ac.at/jeanluc.mieusset/Supramolecular...
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1 Self-Assembly • TERMINOLOGY • SELF-ASSEMBLING COORDINATION COMPOUNDS • HYDROGEN BOND SELF-ASSEMBLIES • INTERLOCKED MOLECULES • APPLICATIONS J.W. Steed, Structure & Bonding, 2004, 108, 97-168. Molecular Containers: Design Approaches and Applications
Transcript of Supramolecular Chemistry 6 - Self-assemblyhomepage.univie.ac.at/jeanluc.mieusset/Supramolecular...
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Self-Assembly
• TERMINOLOGY
• SELF-ASSEMBLING COORDINATION COMPOUNDS
• HYDROGEN BOND SELF-ASSEMBLIES
• INTERLOCKED MOLECULES
• APPLICATIONSJ.W. Steed, Structure & Bonding, 2004, 108, 97-168. Molecular
Containers: Design Approaches and Applications
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Self-Assembly
Templating :Aid to the synthesis through the involvement of temporary or permanent “helper“ species.
Templating a dynamic combinatorial library
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Self-Assembly
Supramolecular self-assembly:Recognition-directed, reversible spontaneous ass ociation of a limited number of molecular components (tecton s) under intermolecular control of noncovalent interacti ons. Reversibility: crucial to form thermodynamicall y most favorable structure, self-repair and correction s of defects.
Recognition-directed self-assemblies
• Strict self-assembly (Tobacco-virus)• Self-assembly with covalent modifications (Insulin)
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Self-Assembly with Covalent Modifications
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Self-Assembly
Self-organization – interactions between constitu ents parts of self-assembled entities and the integration of those interac tions leading to collective behavior such as phase changes.
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Thermodynamics of Strict Self-Assembly
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Thermodynamics
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Template effect in Synthesis
• Metal ions as kinetictemplates OCN
SiNCO
NCOOCN+ 2
HO
O
ONN Si N
N
O
O
O
O
O
O
H
H H
H
O
ONN Si N
N
O
O
O
O
O
O O
O
HO
O
O
HN
O
HN
O
O
NH
O
NH
O
O
O
O
H2O
C(=O)Im2
(7.2)
(7.3)(7.4)
Covalent template synthesis of an 18-membered macrocycle
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Template Effect in Synthesis
• A catenane or rotaxane precursor:
• Interpenetration of an electron-rich guest with an electron-poor macrocycle
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A Thermodynamic Model of Self-Assembly
Zinc Porphyrine Complexes:Zn-pyridyl bond is labile in organic solvents
Also dimer and trimer due to theflexibility of the bridge
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A Thermodynamic Model of Self-Assembly
i.e. 10-5 0.6 (mol/l)
Isac :lower self-assembly concentration
EM :effective molarity(concentration at what open oligomer formation starts to compete formation of cyclic oligomers)
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Self-Assembling Coordination Compounds
+
+
Capsule
Capsule
Convergent
Divergent
DivergentPolymer
Naked Metal(divergent)
Protected metal(convergent)
Naked metal(divergent)
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Self-Assembling Coordination Compounds
“Molecular Library” of polygons from ditopic uni ts
Chem. Rev. 2000, 100, 853.
L
ML L
L
ML
L L
L
L
L
L ML
L
L
L
ML
L L
L
tetrahedral 109.5°
square planar 90°
trigonal bipyramidae 90°, ee 120°, aa 180°
hexagonal 90°, 180°
Pd(0)Cu(I)Zn(II)
Pd(II)Pt(II)Cu(II)
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Self-Assembling Coordination Compounds
A. POLYGONS: Trinuclear Structures
One of the units with 60°
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Self-Assembling Coordination Compounds
Inorg. Chem.2004, 43, 5335.
KPF6H2O-Me2CO
60°C
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Self-Assembling Coordination Compounds
Chem. Rev. 2000, 100, 853.
A. POLYGONS: Tri- and Tetranuclear Structures
Less strained – major
Smaller entropy(smaller number of components)
– increasing fraction at lower concentrations
Equilibrium monitored by 1H NMRSignals assigned in combination with Electron Spray MSMolecular square (X=nothing) binds naphtalene
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Self-Assembling Coordination Compounds
Chem. Rev. 2000, 100, 853.
Macrocycle prevailsat concentrations < 2 mM
Binds organic guests
Catenane prevailsat concentrations > 50 mM
Pd: labile; Pt: inert
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Self-Assembling Coordination Compounds
For Pt equilibrium is reachedupon heating
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Self-Assembling Coordination Compounds
A. POLYGONS: Tri- and Tetranuclear Structures
With more sterically demanding ligands squares are exclusively formed
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Self-Assembling Coordination Compounds• Cryptand synthesizable only through induced fit of a guest because the linkers are
flexible
• Templated with phenylpropionic acid or adamantanecarboxylic acid, not with cations or xylene
• Stable even after synthesis and removal of the guest, not necessarily a thermodynamic product
• (adamantanecarboxylic acid)4@[Pd(en)]12(7.16)8]12+, allosteric effect, 4.6 nm
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Self-Assembling Coordination Compounds
CAGES (POLYHEDRONS)
Chem. Rev. 2000, 100, 853.
“Molecular Library”for the formation of 3D-assemblies from ditopic and tritopic subunits.
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Self-Assembling Coordination Compounds
Acc. Chem. Res. 2002, 35, 972.
Edge-Directed Self-Assembly
Truncated Cube
CubeFace-Directed Self-Assembly
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Self-Assembling Coordination Compounds
Cube
Chem. Rev. 2000, 100, 853.
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Self-Assembling Coordination Compounds
• Dodecahedra
Acc. Chem. Res. 2002, 35, 972.
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Self-Assembling Coordination Compounds
• Trigonal bipyramids
Acc. Chem. Res. 2002, 35, 972.
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Self-Assembling Coordination Compounds
• Truncated tetraheders
Acc. Chem. Res. 2002, 35, 972.
90° Ditopic corners
Planar tritopic linkers
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Self-Assembling Coordination Compounds
• Molecular paneling
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Self-Assembling Coordination Compounds
• Molecular paneling
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Self-Assembling Coordination Compounds
• Nanoreactor
Nanoreactor
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Self-Assembling Coordination Compounds
• Molecular paneling, face directed
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Self-Assembling Coordination Compounds
Molecular Paneling, face directed, nanotubes
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Self-Assembling Coordination Compounds
Other Arrays:
• Helicates• Grids
• Racks
• Ladders• Cylinders
• ……
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Self-Assembly by Hydrogen Bonding
Tennis Ball :
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Self-Assembly by Hydrogen Bonding
Tennis Ball, observed by :
• NMR Spectroscopy in CDCl3: Shift of the NH protons
• Mass Spectrometry
• Vapour pressure osmometry
• X-Ray Crystallography
• Encapsulation of methane and ethane (K = 300 mol/l) in CDCl3
• Bad host for dichloromethane (K = 4)
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Self-Assembly by Hydrogen Bonding
Soft Ball :
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Self-Assembly by Hydrogen Bonding
Soft Ball :
• « Catalysis » of Diels-Alder Reaction
• Self-inhibition : the product is a better guest than the
reactants (Entropy-driven complexation)
• 55 % of the cavity should be occupied by the guest to
obtain the highest affinities in the absence of strong
interactions (0.16 nm³ for the 0.34 nm³ cavity of soft ball)
• Similar value for liquids
O
O
+
O
O
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RosettesMelamine
Cyanuric Acid
Rosette
Crinkled Tape
Linear Tape
Enthalpy vs. Entropy:
Enthalpically favourable:-18 H-bonds formed
(∆∆∆∆H –100KJ/mol)
Entropically very unfavourable. (6 molecules bounded)
� Stability: HB/(N-1)
HB = Number of hydrogen bondsN = Number of molecules
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Preorganisation by linkingthree units together
Peripheral crowding to inhibittape and sheet formation
Rosettes
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Rosettes
Angew. Chem. Int. Ed. 2003, 42, 5717.
Doublerosette
Calix[4]arenebismelamines
Barbituric orcyanuric acid
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Rosettes
Complex with 3 molecules
alizarin
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RosettesAlizarine
Release of the guest with cyanuric acidAlternatively, with protic solvent or a pH change (breaking of the capsule)
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Interlocked Molecules
A. ROTAXANES
B. CATENANES
C. MOLECULAR KNOTS
[2]Rotaxane [2]Pseudorotaxane
[2]Catenane Trefoil knot
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Rotaxanes : Synthesis
Coord. Chem. Rev. 2000, 200-202, 5.
Threading
Snapping Clipping
Slipping
Statistical approach ineffective: < 2 % y.
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Rotaxanes
Synthesis: Clipping Approach
Si O O O
O O O O Si
O
+
N+
N+
Si O O O
O O O O Si
O
N+
N+
N
N+ N+
N
+
BrBr
MeCN, AgPF6, RT, 7dNH4PF6, H2O
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Rotaxanes
Synthesis: Slipping Approach
J.F. Stoddart
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Rotaxanes
Synthesis: Threading Approach
Coord. Chem. Rev. 2000, 200-202, 5.
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Rotaxanes
Synthesis: Threading/Snapping Approach
Coord. Chem. Rev. 2000, 200-202, 5.
84%
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Catenanes
Synthesis via the clipping approach
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Catenanes
1. Formation of the tricationic intermediate2. Formation of a charge transfer complex3. Self-organization to promote the catenation4. The catenane is formed (in 70% yield)
Synthesis, Charge-Transfer Aided
O O
O O
OOO
O O O
+
N+
N
N+
N
BrBr+
OOOOO
OO O O
N+
N+
N+
N+
O
MeCN, AgPF6, RT, 2dNH4PF6, H2O
Yield 70%
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Catenanes
Process I:Circumrotation of the crown ether through the bipyridinium macrocycleProcess II:Circumrotation of the bipyridinium macrocycle through the crown ether(values from the coalescence temperature of a VT NMR experiment.)
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Catenanes
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Catenanes
Synthesis:Auxilliary linkage approach
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Catenanes
Synthesis:Auxilliary linkage approach(covalently)
CHO
CHOMeO
MeO O
O
(H2C)10
(H2C)10
Cl
Cl
(CH2)23
O
O N
(CH2)11
(CH2)11
NH2
(CH2)23
HO
HO N
MeOCO
(CH2)23CO
(CH2)11
(CH2)11
NCOMe
MeOCO
(CH2)23
(CH2)11
(CH2)11
CO
OCOMe
(7.61)
(7.62)(7.63)
(7.64)
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CatenanesCoordination aided synthesis
Yield:27 % in one step,42 % in two steps
• Removal of Cu with CN-
• CV: Reversible reduction (in contrast to the open chaincomplex)
HO
+
OH
HO OH
+
OH
OHHO
HO
I
O
O O
O
I
O O
O
O O
O
OO
O
OO
O
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Helicates
Cu3(7.87e)2
CO2Et substituents ommited isobestic points � only two species present
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Helicates
r = average number of occupied sites
Strong positive cooperativity
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Molecular Knots
XnX – number of crossesn – order of the knot
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Molecular Knots
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Molecular KnotsSynthesis of a 84 membered macrocycle
Bis(1,10-phenantroline)
Yield:a,b,c: less than 8%d: 29%
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Molecular Knots
Doubly interlocked [2]catenane
Pentafoil knot
Triply interlocked [2]catenane
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CatalyticSystems
Inhibited by the product
N NHN
O
Br
O
HN N N
NH2+
NNO NH
HH
ON
HH
H
+
NNO NH
HH
ON
HH
H
O
N N
NH2
N NHN
O
BrHN
NNO NH
HH
ON
HH
H
O
N N N NHN
O
HN
NH
O
N N N NHN
O
HN
NH
Reactants
Catalyst
Catalytic ternary complex
Product complex
Product removed as HBr salt
Self-assembling catalysis via a ternary complex involving a bisubstrate reaction template (after Kelly et.at.1989)
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Self-Replicating Systems
Really autocatalytic since the ternary complex
is more stable than the binary complex
OCHO
O O
HHN N
HH
R1
N
O
R2
R2
OO
HNN
R1
H2N
HH
-
-
+
+
R1=Me,t-Bu
R2=H,NO2
H
(7.103)(7.102)
(7.104)
