Original synthesis and spectroscopic study of thiophene triazine derivatives with enhanced luminescence properties

A straightforward access to π-conjugated oligothiophenes bearing amino-rich groups was developed. Palladium-catalyzed C-H arylation applied in the main step of the synthesis allowed to couple 2-thiophenecarbonitriles and aryl bromides with moderate to excellent yields (35-93%). Then, to improve their basic fluorescence properties, these compounds were transformed into their 2,4-diamino-1,3,5-triazine derivatives, also with good to excellent yields (74-98%). UV-Visible absorption and fluorescence studies identified a strongly emissive molecule (fluorescence quantum yield: Φ_F = 0.78 ± 0.05), which could find use in sensors for applications in biology and in material chemistry. We observed an antagonistic effect in the spectroscopic properties of oligothiophenes bearing 2,4-diamino-1,3,5-triazine, resulting in improved absorptive and emissive properties for more constrained structures having shorter oligothiophenes chains.