Dicarboxy-telechelic cooligomers with sequence structure tunable light absorption

Alternating cooligomers of 5 pyrrole (P) and thiophene (T) units with a PTPTP sequence and carboxylic telechelic groups in α,α′-position are supposed to provide a low band gap and might be incorporated into degradable polymers. In this study we explored whether such new α,α′-ester linked π-conjugated alternating electron rich PTPTP cooligomers of defined size could be created following a Stille coupling synthesis pathway. The obtained cooligomers displayed in the absorption spectra λmax between 341 and 379 nm in solution and between 346 and 410 nm in the solid state, which could be tuned by the substitution with donor type alkyl and alkoxy functions. A strong red shift of the absorption bands into the IR region of the spectrum with absorption maxima between 550 and 650 nm and further to 850 and 1000 nm could be obtained when additional charges by deprotonation or oxidation were introduced. The prepared semi conducting materials could be applied potentially as dyes for photoacoustic imaging or in sensors for oxidation monitoring.