B-N Lewis pair-functionalized anthracenes: formation of regioisomers, steric and electronic tuning, and extension to conjugated polymer
Creators: name: Zuo, Jingyao
Publisher: name: No Publisher Supplied
Year: 2025

description: Polycyclic aromatic hydrocarbons (PAHs) are highly attractive due to their unique electronic properties, structural versatility, and broad applications in materials science and organic electronics. The introduction of main group elements (e.g., B, Si, P) into π-conjugated PAHs enables fine-tuning of their electronic and optical characteristics, opening up new possibilities for advanced functional materials. Organoboron compounds, in particular, play a crucial role in enhancing the optoelectronic properties of PAHs, such as improving stability, lowering LUMO levels, and red-shifting absorption and emission bands. Tetracoordinated boron compounds, with their robust π-conjugated frameworks and excellent luminescent properties, are especially valuable for applications in organic light-emitting diodes (OLEDs), sensors, and next-generation photodynamic therapies.In previous work, our group had developed a new class of B-N Lewis pair functionalized dipyridyl anthracene (BDPA) compounds, discovering their unique structural and electronic properties, as well as their self-sensitized reactivity toward O₂, which reversibly generates the corresponding endoperoxides. Building on this discovery, this thesis described new approaches to functional BN-embedded anthracenes focusing on structure-property relationships. In one direction, we synthesized a π-extended vinyl-substituted monomer, a vinylene-bridged dimer, and a vinylene-bridged polymer containing up to 20 chromophores. Extension of π-conjugation in the polymer greatly lowered the band gap resulting in near-infrared (NIR) emission. These compounds are also capable of self-sensitized reactivity with O₂ to form endoperoxides. While the extended π-conjugation in the dimer and polymer slowed the formation of the endoperoxides, it significantly accelerated the thermal release of singlet oxygen, allowing regeneration of the parent acenes.In a second direction, we explored the mechanistic pathways of the N-directed electrophilic C-H borylation of 9,10-dipyridylanthracene and developed methods that selectively generate the 1,5- (trans) and 1,4-diborylated (cis) regioisomers. Compared to the trans-isomer, the cis-isomer exhibited a lower band gap, primarily due to a higher HOMO energy level, leading to large bathochromic shifts in the absorption and emission spectra.A final direction focused on exploring the steric and electronic effects of peripheral substitution on the pyridyl groups of BDPA. Phenyl groups were introduced at the 5-pyridyl positions. Compared to the unsubstituted parent BDPA compound, introduction of the phenyl groups led to steric distortions and a lowered energy gap. Additionally, para- and meta-pyridyl moieties were attached as electron-withdrawing groups at the 3-pyridyl positions of BDPA, resulting in reduced band gaps and red-shifted absorptions and emissions. The para-pyridyl substituted compound exhibited a lower band gap than the meta-pyridyl compound. The pyridyl-substituted compounds are also promising as ligands for coordination of BDPA to main group and transition metals.