Crystalline solid solution of polycyclic aromatic hydrocarbons stabilized by dispersion forces

• Applicant: Dr. Kazutaka Shoyama
• Subject Area: Organic Molecular Chemistry - Synthesis and Characterisation
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 542652295

Crystalline solid solutions (CSSs) are the solid materials, which consists of two or more components with different ratios. For the formation of CSSs the interaction energy within the same component and between different components should be the same, so that neither the pure component crystalises itself nor a co-crystal is formed. CSSs occur often for inorganic materials, because the interactions, due to covalent or ionic bonds, are generally strong, and generally in the close proximity, and with the spheric form of components, i.e. atoms, energetic requirements for the formation of CSS are fulfilled. Organic molecules, on the other hand, have asymmetric forms and construct molecular crystals that are largely stabilized by weak intermolecular interactions consisting of van der Waals forces. Such weak interactions and asymmetric shapes hamper the formation of CSSs, because the relative energetic difference between different components remain high. In this project, I will utilize diamondoids to create organic CSSs. Diamondoids, such as adamantane, have multiple C-H bonds pointing outside and thus exhibit strong interactions between them. Therefore, I plan to introduce multiple adamantane substituents to polycyclic aromatic hydrocarbons (PAHs) to create organic functional materials that can form CSSs. Such organic CSSs would show tuneable optical properties that cannot be achieved by pure individual components. Asymmetric forms of PAHs could lead to polar or chiral properties of the resulting CSSs, which could find special applications in organic semiconductors. Further development of organic CSSs might lead to a new class of organic semiconductors that could show ferroelectricity or chiral absorption or emission. I anticipate that completion of this project would be a milestone towards novel crystalline organic functional materials.

• DFG Programme: Research Grants