Syntheses and properties of π-conjugated oligomers containing furan-fused and thiophene-fused aromatic units

π-conjugated oligomers 1a–b and 2a–b, containing furan-fused and thiophene-fused aromatic units, were systematically designed and successfully synthesized. Their physicochemical properties were thoroughly investigated. Experimental results showed that different furan/thiophene ratios and fused-aromatic skeletons strongly affected the HOMO energy levels, fluorescent quantum yields and aggregation behaviors of the oligomers. Single crystal structures revealed compound 1b adopted typical herringbone structure with strong C–H⋯π, S⋯π and S⋯S interactions in the crystals. 2a formed slipped π-π stacking in the crystals, and strong π⋯π and O⋯O interactions were observed.

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