Dissertation

Synthetic, Physical and Computational Chemistry of Propeller-shaped Polycyclic Aromatic Hydrocarbons

Author: Ham, A. van der
Date: 24 February 2022
Links: Thesis in Leiden Repository

This thesis systematically studies the physicochemical properties of non-planar, propeller-shaped, polycyclic aromatic hydrocarbons. The synthesis of several so-called propellerenes is described on a gram scale, using optimized procedures aimed at using less hazardous reagents and reducing the amount of organic solvent used. The conformational behavior of several propellerenes is studied experimentally using variable temperature NMR, and findings corroborated using high-level DFT computations. The origin of the conformational preference of propellerenes is elucidated using a novel adaptation of the activation-strain model. By computationally dissecting propellerenes into its constituent parts, the preference of these parts can be analyzed. The spectroscopic properties of conformationally pure propellerenes are studied experimentally, and experimental findings explained on a molecular orbital level, using time dependent DFT computations. Lastly, the supramolecular behavior of propellerenes is studied by the production of molecularly thin films, using the Langmuir-Blodgett technique. These thin films are imaged using electron microscopy, the molecular dynamics at the air-water interface studied computationally, and the physical properties of the thin films quantified using AFM nanoindentation. These propellerene-based thin films are, for the first time, found able to be free-standing over nanometer distances. Combined, this thesis establishes propeller-shaped, polycyclic aromatic hydrocarbons as an independent field of study.