Understanding the role that functionalization plays regarding the electronic properties of organic molecules and their corresponding solids has been a coveted goal of the organic materials community for several decades. Here density functional theory (DFT) is used to calculate the electronic genome of all possible homo-halogeno oligoacene molecules (from benzene to anthracene) in order to establish quantitative structure-property relations (QSPRs). DFT, Hirshfeld surfaces, and Hirshfeld derived energy frameworks are then used to investigate how the molecular properties are perturbed by intermolecular interactions upon crystallization in these halogen bonded materials. Clear correlations between the molecular electronic properties (e.g., HOMO-LUMO gap, polarizability, etc), structural descriptors (e.g., aromaticity), and halogen properties (e.g., ionization potential, atomic radii, etc) are obtained using parsimonious models developed from ordinary least squares linear regression (OLS) as well as machine learning algorithms such as artificial neuronal networks (ANNs) and random forests (RFs). QSPRs are then developed for all homo-halogeno oligoacene molecular crystals present in the Cambridge Structural Database (CSD), where a focus is placed on the band gap, band dispersion, semiconductor polarity (n- vs p-type), and intermolecular orbital overlap (caclculated via the overlap integral, Hab). Molecular symmetry and halogen species are two of the most influential structural descriptors controlling the electronic properties of both the crystal matrix and molecular components, while molecular polarizability and the reduced population of the halogen atomic orbitals in the frontier molecular orbitals also play a critical role.

Unlocking the electronic genome of functionalized polycyclic aromatic hydrocarbon molecules and crystals

2019 Fall National Meeting

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