Aus der Chemie Selbstorganisation, Oberflächen und Chemische Algorithmen Professor Ed Constable Departement Chemie 1 Gibt es ein Skript? Ja Wo? http://www.chemie.unibas.ch/~constable/index.html Wahlen Sie Downloads Benutzer: student Passwort: alchemy Und im Ordner Nano!! Wenn? Morgen!!! 2 1
Chemie IST Nano Viagra 3 In the Praktikum 4 2
Why can t these molecules just build themselves? 5 Selbstorganisation oder Zusammenbau Self-organization is also relevant in chemistry, where it is taken as being synonymous with self-assembly. 6 3
Selbstorganisation oder Zusammenbau Self-assembly is a subset of self-organisation Self-organisation linked to emergent properties Supramolecular chemistry is much concerned with self-assembly 7 8 4
Spontane Bildung komplexer Strukturen/Prozesse bei bestimmten Voraussetzungen durch Zusammenbau der variablen oder identischen Untereinheiten Bakterienrasen 9 Zusammenbau in Lösung Zusammenbau bei Oberfläche 10 5
Zusammenbau in Lösung Lösungsuntersuchungen (NMR, UV-VIS, IR usw) Festkörper Röntgenstrukturen Crystal Engineering Kontroll der 3D Strukturen... Oder nicht! 11 12 6
Chemische Wechselwirkungen Molekul-Molekul Hydrophob, Hydrophil, -, Van der Waals Ionisch, Wasserstoff-Brücken, Koordinationschemie Molekul-Oberfläche Hydrophob, Hydrophil, -, Van der Waals 13 Beispiel aus der Biologie Tabakmosaikvirus (TMV) Virus mit einer Länge von 3000 Å und einem Durchmesser von 180 Å 14 7
Das Tabakmosaikvirus (TMV) 15 49 Untereinheiten 16 8
6500 nucleotide 2130 peptides (nichts 2129, nichts 2131) 17 Concepts in chemical self assembly Molecular recognition Selectivity 18 9
Molekulare Erkennung 19 Molekulare Erkennung 20 10
Elektrostatische und/oder Ion-ion-Paarung Wechselwirkungen zwischen +ve und -ve Ionen oder Dipole Hydrophobe oder hydrophile Wechselwirkungen Wasserstoff-Brücken Host-guest Wechselwirkungen -stackung zwischen Aromaten Koordinationschemie 21 Should bonds be strong or weak Strong robust structures Weak error correction, reversibility Ideal strong but labile bonds 22 11
23 Interaction - electrostatic Depends on distance r but not on spatial oriantation Strong but unselective 24 12
Ion-Ion - Kristallbau Desiraju, G.R. (Ed.) The Crystal As a Supramolecular Entity (Perspectives in Supramolecular Chemistry,) 1996, Vol 2 25 26 13
D.G. Kurth, N. Severin, J.P. Rabe Angew. Chem. Int. Ed. 41 (2002) 3681. 27 28 14
29 Assembly on surfaces Two-dimensional solutions to self-assembly algorithms are attractively simple Atomically flat surfaces interact with appropriate molecules to form two dimensionally ordered monolayers 30 15
Assembly on surfaces http://www.ehcc.kyoto-u.ac.jp/laboratory/material/images/image_2.jpg 31 Langmuir Blodgett 32 16
Biological versus chemical self-organisation Biology is very good at organising multiple components into functional machines. Biology uses interfaces membranes- to Chemists are very bad at organising multiple components into functional machines. So let s learn from biology and use interfaces From three dimensions to two Monoclinic, P21/c a = 5.3937(2), b = 21.697(1) c = 28.776(1)Å, = 91.566(3)º 34 17
Two dimensional sheets in lattice Scherer, Neuburger, Schaffner 35 Overlay of crystal and monolayer 2 nm 10 nm x 10 nm, averaged over 26 positions, U bias = 700 mv, It = 8 pa 36 18
A compound without sheets in the crystal Phenyloctane-graphite Averaged over 21 positions 10 nm 10 nm U bias = -700 mv It = 20 pa. Unit cell a = 4.5 nm b = 1.1 nm = 60.3 V = 4.2 nm 2 Merz, Neuburger, Schaffner,Tao 37 More complex packing I t = 2pA, U bias = -600 mv 40 nm x 40 nm Chem. Eur. J., 2005, 11, 2307; J. Am. Chem. Soc., 2005, 38127, 19
Edelweiss für die Schweizer! 39 Dynamic behaviour 10nm 40 20
Dynamics 2 nm 41 Metal-Directed Self-Assembly Assembly of complex structures through metal-donor atom interactions rather than carbon-carbon or carbon-heteroatom bond formation. Bond strengths 100-300 kj mol -1 Range of geometries and coordination numbers at metal centres (1 to 12 coordinate) is greater than carbon (1, 2, 3 or 4 coordinate). Bond-forming reactions vary from fast (10 9 s -1 ) giving Thermodynamic products to slow (10-8 s -1 ) giving kinetic products Products may be labile or inert 42 21
One-dimensional systems Topologically linear system Metal with coordination number 2n Ligand with two n-dentate donor sets 43 One-dimensional systems 44 22
One-dimensional systems But why is the silver two-coordinate? 45 One-dimensional systems 46 23
Two-dimensional systems sheets 47 Two-dimensional systems sheets 48 24
Two-dimensional systems sheets Cu(II) + 49 Helicates - molecular threads How can the twisting be controlled? 50 25
A simple model coplanar Electronically favoured Sterically disfavoured orthogonal Electronically disfavoured Sterically favoured Twisting 51 Qtpy with tetrahedra Metal ions coding for tetrahedral geometry will coordinate to only two of the donor atoms 52 26
Qtpy reality 53 54 27
Helical chirality Helices are inherently chiral they have a sense of direction 55 Jean-Marie Lehn: Self-Assembly 2 3 Cu(I) Molecular Self-Assembly Super-Molecule 56 28
Coordination polymers: necklace chains + FeCl 3 + 2KSCN Potential for spin-crossover materials (magnetic data storage etc) Compatible ligands Two didentate metal binding domains The two domains must bind to different metal centres The didentate domain can bind to two of the sites of a tetrahedron 58 29
Self-assembly of grids and polygons Tetrahedral centre Osborn et al. Angew. Chem., Int. Ed. Engl. 1992, 6, 733 59 60 30
Grids - beyond boxes 61 Mixing ligands - stepladders 62 31
Longer ladders 63 Mixing ligands - new grids 64 32
Mixing ligands - new grids 65 And so to cages 66 33
And so to cages 67 34