design, synthesis and characterization of well-defined and fuctional alpha,alpha

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The chemistry of oligopyrroles : design, synthesis and
characterization of well-defined and fuctional alpha,alpha-
linked oligomers
Citation for published version (APA):
Groenendaal, L. (1996). The chemistry of oligopyrroles : design, synthesis and characterization of well-defined
and fuctional alpha,alpha-linked oligomers. [Phd Thesis 1 (Research TU/e / Graduation TU/e), Chemical
Engineering and Chemistry]. Technische Universiteit Eindhoven. https://doi.org/10.6100/IR468941
DOI:
10.6100/IR468941
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Published: 01/01/1996
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The Chemistry of Oligopyrroles
Design, synthesis and characterization of
well-defined and functional a,a-linked oligomers
The Chen1istry of Oligopyrroles
Design, synthesis and characterization of
well-defined and functional a,a-linked oligomers
PROEFSCHRIFT
ter verkrijging van de graad van doctor aan de
Technische Universiteit Eindhoven, op gezag van
de Rector Magnificus, prof.dr. M. Rem, voor een
commissie aangewezen door het College van
Dekanen in het openbaar te verdedigen op
dinsdag 12 november 1996 om 16.00 uur
door
Lambertus Groenendaal
geboren te Dordrecht
Dit proefschrift is goedgekeurd
door de promotoren:
prof.dr. E.W. Meijer
prof.dr. K. Müllen
Copromotor: dr. J.A.J.M. Vekemans
Groenendaal, Lambertus
The Chemistry of Oligopyrroles -Design, synthesis and characterization
of well-defined and functional a,a-linked eligomers I Lambertus Groenendaal.
Eindhoven : Eindhoven University of Technology
Thesis Technische Universiteit Eindhoven.-With ref.-
With summary in Dutch
ISBN 90-386-0268-5
Subject headings: pyrrole I oligomer I conducting polymer.
.91.an mijn ouáers.
'Voor 'Bianca.
Contents
Chapter 1 Introduetion 1
1.1 Pyrrole. .. oligopyrroles ... polypyrrole
1.2 Pyrrole: A historica! overview 2
1.3 Protecting groups at nitrogen 3
1.4 Well-defined oligopyrroles 4
1.5 Polypyrrole 9
1.6 Organometallic aryl-aryl coupling reactions 12
1.6.1 Kumada coupling 12
1.6.2 Suzuki coupling 13
1.6.3 Negishi coupling 14
1.6.4 Semmelhack!Y amamoto coupling 14
1.7 Aim of the research 15
1.8 Scope of the thesis 16
1.9 References 17
Chapter 2 Oligopyrroles by the Stille reaction: A methodological
study 23
2.1 Introduetion 23
2.2 Synthesis of Stille coupling reagents 26
2.2.1 Introduetion 26
2.2.2 Results and discussion 27
2.3 Mechanistic studies 29
2.3.1 Influence of sol vent on the Stille reaction 29
2.3.2 Influence of halide on the Stille reaction 31
2.3.3 Influence of electron-releasing/-withdrawing substituents on the
Stille reaction 32
2.3.4 Overall conclusions on the mechanistic studies 34
2.4 Well-defined oligopyrroles by the Stillereaction 34
2.4.1 Synthesis 34
2.4.2 Characterization 38
2.4.3 Discussion 39
2.5 Conclusions 41
2.6 Experimental section 42
2.7 References 52
Chapter 3 Well-defined and functional oligopyrroles: Studies toward
future applications 55
3.1 (Nonlinear) optica! properties of D-n-A substituted oligopyrroles 55
3.1.1 Introduetion 55
3.1.2 Synthesis and (nonlinear) optica! properties of a series of N-t-BOC
protected D-n-A oligopyrroles 57
3.1.2.1 Synthesis and characterization 57
3.1.2.2 (Nonlinear) optica! properties 58
3.1.3 Synthesis and (nonlinear) optica! properties of 5-{N -t-BOC-2"-
[5"( 4-methoxyphenyl)]pyrrolyl) -5'-{N-t-BOC-2"'- [5'"(4 -nitro-
phenyl)]pyrrolyl )-2,2'-bithiophene 61
3.1.3.1 Synthesis and characterization 61
3.1.3.2 (Non!inear) optica! properties 62
3.1.4 Hyperpolarizability measurements on deprotected D-n-A oligo
pyrroles 63
3.1.5 Conclusions 65
3.2 Mixed oligomers for Scanning Tunnelling Microscopy studies 66
3.2.1 Introduetion 66
3.2.2 Synthesis and characterization 68
3.2.3 STM-measurements 69
3.2.4 Conclusions 71
3.3 Studies on the redox behavior of two series of a-oligoheteroaromatic
compounds 71
3.3.1 Introduetion 71
3.3.2 Results and discussion 72
3.3.3 Conclusions 75
3.4 Overall conclusions/Outlook 76
3.5 Experimental section 76
3.6 References 85
Chapter 4 Synthesis and characterization of functionalized 3-alkyl
pyrroles: On the way to regioregular polypyrroles 91
4.1 Introduetion 91
4.2 Attempts toward regioregular polypyrroles 94
4.3 Attempts toward regioregular oligopyrroles 97
4.4 Detailed studies on the functionalization of N-protected 3-hexylpyrroles 98
4.4.1 Halogenation of N-protected 3-hexylpyrroles 98
4.4.2 Stannylation of N-protected 3-hexylpyrroles 100
4.4.3 The stannyl-bromo exchange reaction 101
4.5 Conclusions 103
4.6 Experimenta! section 104
4.7 References I 13
Chapter 5 Pyrrole -sulfur compounds: Attempts toward intrinsically
conducting polymers 115
5.1 Introduetion 115
5.2 Oligo-and poly(pyrrole-2,5-diyl sulfide)s 120
5.3 Poly(thienylthiothienylpyrrolyl) 124
5.4 Conclusions 128
5.5 Experimenta! sectien 128
5.6 References 132
Chapter 6 Well-defined oligo(pyrrole-2,5-diyl)s by the Ullmann
reaction 135
6.1 Introduetion 135
6.2 Synthesis and characterization of the monomers 137
6.3 Synthesis and characterization of oligo(N-t-BOC-pyrrole-2,5-diy1)s 139
6.4 Properties of the eligomers 144
6.5 Conclusions 145
6.6 Experimenta! section 146
6. 7 References 151
Summary 154
Samenvatting 156
Publications 158
Curriculum Vitae 160
Dankwoord 161
Chapter 1
INTRODUCTION
1.1 Pyrrole ... oligopyrroles. ..p olypyrrole
For decades scientists have been attempting to design new molecules with functional
properties in the quest for new materials. One class of compounds that created an enormous
interest during this period are tr-conjugated polymers. Due to the substantial lr-electron
delocalization along their backbones, these polymers show appealing (nonlinear) optica!
properties and become good electrooie conductors when oxidized or reduced. Hence, a
prominent and active role is foreseen for these compounds in a variety of practical applica
tions such as information storage, optical signal processing, electromagnetic interference
(EMI) shielding and solar energy conversion, as well as rechargeable batteries, light emitting
diodes (LED's), field effect transistors (FET's), printed circuit boards (PCB's) and antistatic
materials.
Despite the overwhelming effort that has been put in the development of these
polymers, only very few compounds are actively being applied in devices at this moment; the
vast majority still remaio 'materials of the future'. The main reason for this Jack of applica
tion is the fact that the perf~rmance of tr-conjugated polymers is still nol optimal. This delay
is related to the low stability under atmospheric conditions, the Jack of processability and/or
the undefined structure of the existing polymers.
Polypyrrole is one of the numerous tr-conjugated polymers that bas been studied in
this field. In contrast to most other polymers, it is extremely stabie in its oxidized form; the
latter makes it very interesting for applications as a conducting polymer. However, as a result
of the synthetic strategies applied, its structure contains many defects that reduce the effective
conjugation length and, therefore, diminish its useful properties. The preparatien of a well
defined a,a-linked polypyrrole that can be used in several of the aforementioned
applications, necessitates the development of a more controlled polymerization route.
Therefore, several organometallic aryl-aryl coupling reaelions have been investigated.
However, instead of applying these coupling reactions for the synthesis of perfectly a,a
linked polypyrrole, we decided to study the synthesis of well-defined a,a-linked
oligopyrroles first. Well-defined eligomers can be used to obtain a detailed insight into the
behavier of their corresponding polymerie analogs, while the synthetic methodology can be
applied to prepare structurally perfect and directly applicable polymers.