O-B←N Perturbed Polycyclic Aromatic Hydrocarbons: A Straightforward Synthesis Strategy, Photophysical, and Optical Waveguide Properties

Polycyclic aromatic hydrocarbons (PAHs) containing O-B←N groups in the backbone have been demonstrated excellent optical properties but two-dimensionally (2D) extended O-B←N perturbed PAHs have been rarely disclosed due to the synthetic difficulties. Moreover, the applications of these O-B←N perturbed PAHs are primarily limited to electroluminescent devices and opening up novel functions of this class of heteroaromatic molecules is urgent. 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 characterizations and theoretical simulations to 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 are further self-assembled to 1D microstructures, e.g., rod or sheet shaped microwires in solutions. These microwires are unprecedentedly subjected to optical waveguide measurements and low optical loss coefficients of 10^-2~10^-3 dB/μm are found. This work develops an efficient synthesis strategy toward 2D extended O-B←N perturbed PAHs and performs pioneering applications to optical waveguide, demonstrating the great potential of these O-B←N perturbed PAHs for micro/nanophotonics.