Synthesis of Highly Soluble and Oxidatively Stable Tetraceno[2,3-<i>b</i>]thiophenes and Pentacenes

A comparative study of suitably functionalized, highly soluble tetraceno[2,3-<i>b</i>]thiophenes (<b>1</b>−<b>3</b>) and pentacenes (<b>4</b>−<b>6</b>) that show higher photoxidative stability than that of unfunctionalized corresponding acenes is reported. The absorption and emission of <b>1</b>−<b>3</b> (<i>A</i><sub>max</sub> = 624−656 nm, λ<sub>max</sub> = 634−672 nm, Φ<sub>F</sub> ≈ 10%) and <b>4</b>−<b>6</b> (<i>A</i><sub>max</sub> = 672−704 nm, λ<sub>max</sub> = 682−718 nm, Φ<sub>F</sub> ≈ 10%) were found to be systematically red-shifted by the substitution in the order of the <i>tert</i>-butylethynyl < triisopropylsilylethynyl < phenylethynyl groups. The oxidation potentials of these compounds were similar (<i>E</i><sub>1/2</sub> ≈ 0.70 V), except for <b>4</b>, which showed lower oxidation potential (<i>E</i><sub>1/2</sub> ≈ 0.63 V).