Soluble Adamantyl-Substituted Oligothiophenes with Short Fluorescence Decay: An Approach for Ultrafast Optical Signal Processing

THF-soluble, adamantyl-substituted oligothiophenes (n=1-3) were prepared via Negishi cross-coupling reactions. Thus, the synthesis of 2-(1-adamantyl)quaterthiophene was realized by cross-coupling of 5-bromo-2-(1-adamantyl)terthiophene with 2-thienylzinc chloride. Treatment of these oligothiophenes with FeCl₃ affords the corresponding dimeric compounds, which have pigment properties. In contrast, the mono-substituted (1-adamantyl)oligothiophenes (n=1-4) are readily soluble in organic solvents. Particularly the quarter-oligomer displays remarkable optical properties such as an increased Stokes' shift in combination with a very fast fluorescence decay of 0.39ns and a high fluorescence quantum yield. The compound was incorporated in a solid poly(methyl methacrylate) matrix and its optical properties were nearly unaltered. This may allow applications in high-throughput optical signal processing exceeding the GBit scale.