Synthesis and analysis of reduced aromatic species

Polycyclic aromatic hydrocarbons (PAHs) are fundamental model systems in organic and materials chemistry due to their extended π-conjugation and tuneable electronic properties. Their reduced species, generated by electron transfer from alkali metals, play a crucial role in synthetic methodology, charge transport, and the development of redox-active organic materials. However, their inherent instability and high reactivity complicate both synthesis and characterization. Continuous flow chemistry offers a promising platform to address these challenges by providing safe handling, reproducibility, and real-time monitoring. In this thesis, a flow-based methodology for the generation, analysis and quantification of reduced PAHs was established using sodium-loaded packed bed reactors. Naphthalene, anthracene, and phenanthrene were investigated as representative substrates under both batch and flow conditions. Infrared (IR) spectroscopy proved to be the most reliable quantitative method for in-line monitoring, while ultraviolet-visible (UV-Vis) spectroscopy enabled qualitative detection of radical anions. Complementary electron paramagnetic resonance (EPR) experiments confirmed the open-shell character of the intermediates, though limitations in sample handling prevented full hyperfine resolution. Systematic studies revealed the impact of solvent quality, concentration, flow rate, and temperature on the stability, reactivity and production rate of the reduced species. While naphthalene could be reproducibly reduced and monitored, anthracene required careful control of residence time to prevent side-reactions, and phenanthrene reductions highlighted the importance of substrate purification for reproducibility and characterisation. By integrating controlled flow operation with spectroscopic analytics, this work establishes a versatile platform for studying reduced PAHs under defined and scalable conditions. The results provide deeper insights into their structure-property relationships and offer a methodological basis for future investigations on larger PAHs, heteroaromatic systems and organic electrode materials in energy storage applications.

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