Exit Seminar: Inter and Intra Molecular Interactions to Control the Optoelectronic Properties of Materials

Date:
Location:
CP 114
Speaker(s) / Presenter(s):
Alison Costello

Woman with long brown hair wearing glasses and a maroon shirt, smiling in front of a neutral gray background.

Functional materials used for optoelectronic applications are often employed in the solid-state regime. The properties of such solid-state materials are entirely dependent on the inter and intra molecular interactions that the molecules experience. Intermolecular interactions are interactions between two adjacent molecules and can be broken down into two subgroups: repulsive and attractive. Intramolecular interactions are interactions that occur within a molecule and include things like bonding, resonance, and electron distribution. These properties can be tuned through a number of techniques to afford desirable outcomes for various material applications. This dissertation will investigate how the tuning of the inter and intra molecular forces influence a material’s electronic and optical properties.

Circular graphic divided into three sections showing concepts in molecular design. Top left: hydrogen bonding semiconductors with molecular structures and charge transfer diagrams. Top right: ionic interactions and conjugation for light emission, featuring molecular ions, a photoluminescence spectrum, and chemical structures. Bottom: ligand conjugation to tune red emission, with molecules spanning a color gradient from blue to red and schematic human figures pushing or holding them.

The dissertation will cover three projects that leverage control over hydrogen bonding, ionic interactions, and electron density to influence the optoelectronic properties of various systems. The first project attempted to increase intermolecular electronic couplings by using hydrogen bonded coproducts between an organic small molecule semiconductor and benzoic acids. Hydrogen bonding is a monodirectional interaction. The second project, in contrast, focuses on ionic interactions, which are multidirectional. These ionic interactions were investigated through the addition of a conjugated organic core to the inorganic anion in an organic inorganic hybrid material (OIHM) to improve material photoluminescence quantum yield (QY) efficiency. Additionally, alkyl substituents and anion size were changed to probe the effect of spacing on QY. In the third project of this dissertation, the focus moves from intermolecular interactions to intramolecular interactions. This project focuses on using electron donating and accepting groups to tune the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels of a metal complex to achieve more efficient deep red and near infrared (NIR) emission.

KEYWORDS: Intermolecular Interactions, Intramolecular Interactions, Optoelectronics, Organic Semiconductors, Light Emitting Materials