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

A comparative study of suitably functionalized, highly soluble tetraceno[2,3-b]thiophenes (1−3) and pentacenes (4−6) that show higher photoxidative stability than that of unfunctionalized corresponding acenes is reported. The absorption and emission of 1−3 (A_max = 624−656 nm, λ_max = 634−672 nm, Φ_F ≈ 10%) and 4−6 (A_max = 672−704 nm, λ_max = 682−718 nm, Φ_F ≈ 10%) were found to be systematically red-shifted by the substitution in the order of the tert-butylethynyl < triisopropylsilylethynyl < phenylethynyl groups. The oxidation potentials of these compounds were similar (E_1/2 ≈ 0.70 V), except for 4, which showed lower oxidation potential (E_1/2 ≈ 0.63 V).