BODIPY (boron dipyrromethenes) dyes serve as versatile platforms for optoelectronic and biomedical applications, owing to their outstanding photophysical properties and structural adaptability. Constructing BODIPY oligomers presents a powerful strategy to modulate their optical and electrochemical behavior through strong exciton coupling among chromophores. However, conventional synthetic routes, particularly for sp 3 -carbon-bridged oligomers, are often multistep and typically yield only dimers. Herein, we report a facile one-pot synthesis of β-β methylene?bridged BODIPY oligomers. Installation of methyl groups at the α and γ-positions blocks competing sites and increases the core electron density, facilitating an electrophilic substitution with protonated paraformaldehyde. The methylene bridge and steric demand of the α-methyl groups enforce a large transition dipole moment angle, resulting in pronounced absorption-band splitting with a major feature of J-type exciton coupling. This mechanism is systematically elucidated using spectroscopy, single-crystal X-ray analysis, and TD-DFT (time-dependent density functional theory) calculations. The well-defined methylene-bridged oligomers established herein provide an ideal model system for studying exciton coupling and advance the design of functional dye architectures.
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