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Studies towards Reductive Aromatizations of Polyaromatic Hydrocarbons and Synthesis of Precursors for on-Surface Synthesis of Nanographenes
Polyaromatic hydrocarbons (PAHs) are of great research interest as they are candidates for many technical applications. PAHs find already application in organic solar cells (OSCs), organic field-effect transistors (OFETs) and organic light-emitting diodes (OLEDs). Especially in case of the miniat...
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| Format: | Doctoral Thesis |
| Language: | English |
| Published: |
Philipps-Universität Marburg
2021
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| Subjects: | |
| Online Access: | PDF Full Text |
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| Summary: | Polyaromatic hydrocarbons (PAHs) are of great research interest as they are candidates for many
technical applications. PAHs find already application in organic solar cells (OSCs), organic
field-effect transistors (OFETs) and organic light-emitting diodes (OLEDs). Especially in case
of the miniaturization of electronic components, they are becoming increasingly important in
large-scale applications. For an optimal application, tailor-made properties such as a precisely
defined (optical) HOMO-LUMO gap or the highest possible fluorescence quantum yields with
the narrowest possible emission are crucial. The most effective tool to precisely tune these
properties is chemical functionalization.
The first part of this cumulative doctoral thesis deals with the reductive functionalization of
polyaromatic hydrocarbons. This novel approach, previously described in only few examples
in literature, utilizes a one-step functionalization of oxidatively generated precursor molecules
using the cheapest and easiest-to-handle reducing agents possible, such as zinc. This strategy
results in fourfold functionalized electron-rich ethers, silyl ethers, pivaloates or even triflates. As
electron-rich counterparts to the rylenediimide dyes described many times in literature and in
addition to the pyrene dyes, which have also been studied photochemically in great detail, the
syntheses and properties of fourfold functionalized diazapyrenes, peropyrenes and their higher
homologous terropyrenes and quarterropyrenes as well as violanthrenes are described in a total
of five accepted publications. Furthermore, a materials chemistry application perspective for the
synthesis of (N-doped) Carbon Nanoparticles is presented. Via UV-Vis and photoluminescence
spectrometry as well as cyclic voltammetry, the (opto-)electronic properties are discussed in the
context of the influence of the different functionalizations. Quantum chemical DFT calculations
are discussed and are used for a deeper understanding of the electronic influences of the different
substitutions.
In the second part of this work, collaborative projects with surface chemists from the Gottfried
group and others are presented in four publications. In recent years, the surface-assisted
synthesis of nanographenes and graphene nanoribbons has become increasingly important for
the synthesis and characterize of these unfunctionalized graphene derivatives, which are often
difficult to investigate due to poor solubility. For this purpose, porous nanographenes such
as Kekulen or a C108 nanographene as well as porous graphene nanoribbons are prepared on
single-crystalline noble metal surfaces via surface-supported Ullmann reaction and subsequent
cyclodehydrogenations. For this, suitable halogenated precursors were designed and synthesized
within the scope of this work. The influence of the nature of the surface on the resulting products
as well as the individual electronic properties of the porous nanographene structures is
investigated by means surface analytic methods such as Scanning tuneling spectroscopy (STS)
or angle resolved photoelectron spectroscopy (ARPES). |
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| Physical Description: | 379 Pages |
| DOI: | 10.17192/z2022.0050 |