Influence of the substitution pattern on the optoelectronic properties of oligofuran and oligothiophene–phosphole chains

2-α-Terthienyl- and terfuryl-1,3,4-trimethylphospholes were prepared by [1,5] shift of the terthienyl or terfuryl substituents from P to the α-carbon of the ring in the appropriate 1-terthienyl- or terfurylphospholes under heating in basic medium, followed by quenching the resulting phospholides by methyl iodide. The corresponding sulfide, borane and gold iodide complexes were prepared in the terthienyl case. Comparing the spectra of the highly fluorescent borane complexes of the 2-terfuryl and 2-terthienyl-phospholes showed that the UV–Vis absorption wavelength is not significantly modified upon replacement of S by O but that the fluorescence quantum yield is multiplied by 1.82.

Graphical abstractThe replacement of S by O in a conjugated 2-terthienylphosphole derivative leads to a much higher quantum yield for the fluorescence.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► It is possible to replace thiophene by furan in phosphole-polythiophene chains. ► The P–BH3 complexes display the best fluorescence properties. ► The replacement of thiophene by furan enhances the fluorescence quantum yield.