Photochemical Synthesis of 2,6‐Linked Anthracene Oligomers without Introducing Extra Substituents

Abstract

Photoconvertible precursors of 2,6‐linked anthracene oligomers (trimer, tetramer, and pentamer) were synthesized through repeated Suzuki‐Miyaura cross‐coupling reactions. Upon exposure of these precursors to light at 450 nm, which correspond to the n–π* transition of diketone moieties, yellow precipitates were formed, suggesting the conversion to the corresponding anthracene oligomers from the precursors. The disappearance of 1H NMR peaks after photoirradiation indicated the formation of anthracene oligomers with less solubility. High‐resolution mass spectrometry evidently indicated the oligomer formations, and infrared spectral analysis for thin films showed the disappearance of peaks originating from the carbonyl groups, also supporting the conversion. The absorption spectra after photoirradiation indicated a red‐shift in the absorption peaks accompanying oligomer formations, suggesting an extension of the π‐conjugated system. The low solubility of the resulting anthracene oligomers in organic solvents highlights the effectiveness of this synthetic strategy using the photoconvertible precursor. This study provides a practical method to synthesize acene oligomers without the introduction of extra substituents.