Synthesis and characterization of new Discotic Polycyclic Aromatic Hydrocarbons and related ...

225 Pages·2006·10.63 MB·English

Synthesis and characterization of new Discotic
Polycyclic Aromatic Hydrocarbons
and related pyrolytic nanostructures

Dissertation

zur Erlangung des Grades
“Doktor der Naturwissenschaften”

am Fachbereich Chemie, Pharmazie und Geowissenchaften der
Johannes Gutenberg-Universität Mainz
vorgelegt von

Bassem El Hamaoui
geboren in Tripoli, Libanon

Mainz, 2007

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Decan:
1. Berichterstatter:
2. Berichterstatter:
Tag der mündlichen Prüfung:

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Die vorliegende Arbeit wurde in der Zeit von januar 2003 bis januar 2007 im Max-Planck-
Institut für Polymerforschung in Mainz unter Anleitung von Herrn Prof. Dr. Klaus Müllen
ausgeführt.

Ich danke Herrn Prof. Dr. K. Müllen für seine wissenschaftliche und persönliche Unterstützung
sowie für seine ständige Diskussionsbereitschaft.
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Dedicated to my mother, my sister
and to the memory of my father

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Table of contents

1. Introduction......................................................................................................................... 1
1.1 Polycyclic Aromatic Hydrocarbons (PAHs)...................................................................... 1
1.2 Carbon Nanotubes (CNTs): general overview on synthesis, properties and applications.. 5
1.2.1 Definition of CNTs………………………………………………………………… 5
1.2.2 Synthesis and properties…………………………………………………………… 6
1.2.2.1 Electric Arc discharge…………………………………………………………. 6
1.2.2.2 Laser Ablation………………………………………………………………… 7
1.2.2.3 Chemical Vapor Deposition………………………………………………… 9
1.2.3 Potential applications of CNTs…………………………………………………….. 9
1.2.4 From graphitic CNTs to graphenic Discotic Liquid Crystals(LCs)………………... 10
1.3 Liquid Crystals: definition, bulk properties and applications……………………………. 10
1.3.1 Synthesis and phase behavior of discotic LCs……………………………………... 13
1.3.2 Amphiphile discotic LCs…………………………………………………………... 17
1.3.3 Charge carrier mobility and related electronic properties of graphite discs……….. 18
1.3.4 FETs………………………………………………………………………………... 20
1.3.5 Photovoltaic cells…………………………………………………………………... 21
1.4 Motivation and objectives………………………………………………………………... 22

2. Time-resolved spectroscopic study of phosphorescent platinated and alkylated
hexa-peri-hexabenzocoronenes……………………..……………………………………… 30
2.1 Introduction………………………………………………………………………………. 30
2.2 Synthesis…………………………………………………………………………………. 32
2.3 Photophysical properties…………………………………………………………………. 36
2.4 Photoluminescence study of HBC-Ph-C (25)………………………………………….. 43
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2.5 In-Solution HBC supramolecular chemistry…………………………………………….. 45
2.6 Summary…………………………………………………………………………………. 50

3. Self-assembly of amphiphilic hexa-peri-hexabenzocoronenes into supramolecular
nanostructures………………………………………………………………………………. 52
3.1 Introduction………………………………………………………………………………. 52
3.2 Synthesis and structural characterization………………………………………………… 54
3.3 Results and discussion…………………………………………………………………… 58
3.3.1 UV-Vis and fluorescence spectra……………………………………………….. 58
3.3.2 Solid-state self-assembly investigated by X-ray scattering..........………………. 61
3.3.3 Infrared spectroscopy…………………………………………………………..... 67
3.3.4 Self-assembled nanostructures studied by electron microscopy………………... 69
3.3.5 Discussion……………………………………….................................................. 71
3.4 Conclusion……………………………………………………………………………….. 77

4. Control of the homeotropic order of discotic hexa-peri-hexabenzocoronenes……….. 81
4.1 Processability and alignment on surfaces ….……………………………………………. 81
4.2 Synthesis…………………………………………………………………………………. 84
4.3 Thermal properties of compounds 45a and 45b…………………………………………. 87
4.4 Structure investigation by X-ray scattering of compounds 45a and 45b……………....... 88
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4.5 Homeotropic arrangement of compounds 45a and 45b…………………………………. 93
4.6 Synchrotron radiation Microfocus diffractometry of the dendritic morphology………… 99
4.7 Discussion………………………………………………………………………………... 102
4.8 Conclusion……………………………………………………………………………….. 106

5. Solid-state synthesis of carbon nanotubes and other carbon nanostructures by
thermolysis of 2D and 3D cobalt complexes………………………………………………. 110
5.1 Introduction………………………………………………………………………………. 111
5.2 Preparation and solid-state pyrolysis of complex 50 as a model compound…………….. 112
5.2.1 Synthesis and characterization of complex 50……………………………………... 112
5.2.2 Results and discussion……………………………………………………………... 115
5.3 Cobalt complexes with various structures and geometries………………………………. 121
5.3.1 Synthesis and characterization……………………………………………………... 123
5.3.2 Results and discussion……………………………………………………………... 130
5.3.3 Conclusion…………………………………………………………………………. 141

6. Uniform carbon and carbon-cobalt nanostructures by solid-state thermolysis of
polyphenylene dendrimer-cobalt complexes…………………………………………… 144
6.1 Introduction………………………………………………………………………………. 144
6.2 Synthesis and characterization…………………………………………………………… 146
6.3 Solid-state thermolysis of cobalt complex 71……………………………………………. 149
6.3.1 Results and discussion……………………………………………………………... 149
6.3.2 Acidic treatment and magnetic properties of cobalt nanoparticles of 71 prepared
at 800 °C…………………………………………………………………………………. 153
6.4 Thermolysis of the higher generation dendrimer cobalt complexes 72 and 73………….. 159
6.5 Summary…………………………………………………………………………………. 161

7. Summary and Outlook…………………………………………………………………... 164

8. Experimental Section…………………………………………………………………….. 172
8.1 General methods…………………………………………………………………………. 172
8.2 Materials…………………………………………………………………………………. 174
8.3 Synthesis…………………………………………………………………………………. 175

9. Appendix………………………………………………………………………………….. 208
List of Publications…………………………………………………………………………. 212

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