Abstract
Conjugated oligomers containing imidazole or benzimidazole units were synthesized by Suzuki coupling polymerization of 4,5-dibromoimidazole or 4,7-dibromobenzimidazole with benzene-1,4-diboronic acid bearing a protected phenolic hydroxyl group and a decyloxy chain. The hydroxyl groups in the polymers were subsequently deprotected by catalytic hydrogenation with Pd-C/H2. As the content of the deprotected hydroxyl group increased, the UV absorption maximum wavelength in a THF solution red shifted. The PL emission maximum wavelength also red shifted and the fluorescence quantum yield decreased with increasing the degree of deprotection. Oligomers containing the imidazole unit demonstrated more pronounced shifts. For the imidazole-containing conjugated oligomer having the deprotected hydroxyl group, the UV and PL spectra blue shifted by increasing the solvent polarity. The addition of NaOH to a polymer solution gave rise to a blue-shift of the fluorescence peak. The UV and PL spectra showed ignorable shifts even when measuring in a thin film. These results could suggest that the imidazole-containing conjugated oligomer forms two intramolecular hydrogen bondings and has a non-planar conformation.
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Takagi, K., Sugihara, K., Ohta, J. et al. Conjugated Oligomers Containing Imidazole in Main Chain with Intramolecular Hydrogen Bonding. Polym J 40, 614–621 (2008). https://doi.org/10.1295/polymj.PJ2008045
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DOI: https://doi.org/10.1295/polymj.PJ2008045