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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Bibliographic Details
Main Author: Werner, Simon
Contributors: Sundermeyer, Jörg (Prof. Dr.) (Thesis advisor)
Format: Doctoral Thesis
Language:English
Published: Philipps-Universität Marburg 2021
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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).
Physical Description:379 Pages
DOI:https://doi.org/10.17192/z2022.0050