O–B ← N perturbed polycyclic aromatic hydrocarbons: a straightforward synthesis strategy, and their photophysical and optical waveguide properties

Abstract

Polycyclic aromatic hydrocarbons (PAHs) containing O–B ← N groups in the backbone have demonstrated excellent optical properties but two-dimensionally (2D) extended O–B ← N perturbed PAHs have been rarely reported due to synthetic challenges. Moreover, the applications of these O–B ← N perturbed PAHs have been primarily limited to electroluminescent devices, highlighting the urgent need to explore novel functions of this class of heteroaromatic molecules. This work develops a straightforward synthesis strategy toward O–B ← N perturbed PAHs through 2–3 steps, creating a series of tetra-cycle, octa-cycle, and deca-cycle fused molecules. Photophysical characterization and theoretical simulations of these O–B ← N perturbed PAHs reveal several distinct properties, e.g., high fluorescence quantum yields (70%), aggregation induced emission (AIE) effects, and anti-Kasha emission. Then, through classic solvent diffusion or volatilization methods, these O–B ← N perturbed PAHs further self-assemble into 1D microstructures, e.g., rod or sheet shaped microwires in solutions. These microwires were, for the first time, subjected to optical waveguide measurements, revealing low optical loss coefficients ranging from 10⁻² to 10⁻³ dB μm⁻¹. This work develops an efficient synthesis strategy for 2D extended O–B ← N perturbed PAHs and demonstrates their pioneering applications in optical waveguides, demonstrating the great potential of these O–B ← N perturbed PAHs for micro/nanophotonics.