Boron-doped heteroaromatic molecules have gained significant interest in recent years due to their unique electronic properties that are drastically different from the entirely carbon-based analogs. Due to the trivalent nature of boron, it has an empty <i>p<sub>z</sub></i>-orbital that can accept electrons and participate in π-conjugation. This intrinsic electronic property renders boron-doped aromatic systems as stronger electronic acceptors, and is desirable for materials applications including organic light emitting diodes and photovoltaics. However, because of this electrophilic nature of boron, reduced boryl species are quite rare and exceedingly challenging to isolate. Although with the appropriate ligand scaffolding, these molecules can be stabilized and their nucleophilicity harnessed for numerous chemical transformations to yield novel boron-based materials with new or improved photophysical properties. Recently, we isolated six carbene-stabilized borafluorene monoanions via two electron chemical reduction. In efforts to explore the nucleophilicity of these boron-based monoanions, we have reacted them with various metal chlorides, diketones, elemental selenium, and selenium containing reagents. This led to the first examples of boryl-substituted selenides and diselenides. These reactivity studies demonstrate the versatility of the carbene-stabilized borafluorene monoanions as a useful chemical synthon. In addition, we previously prepared a new class of benzene- and pyrene-fused N-heterocyclic boranes which exhibit tunable luminescent properties across the entire visible light spectrum. In this presentation, the synthesis, reactivity, structure, and optical properties of our recent developments in novel boron-doped heterocycles will be highlighted.

Boron-doped conjugated heterocycles towards functional main-group materials

ACS Spring 2022

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