Synthesis and Properties of Soluble and Stable Silyl End-capped Bis-thienylanthracene Oligomers

Abstract

A series of new organic semiconductors dimethyl-n-octylsilyl end-capped thiophene-anthracene oligomers containing 9,10-anthracene moiety in the center have been synthesized using palladium-catalyzed Stille coupling reactions. The synthesized bis-silylated thiophene-anthracene oligomers were characterized by 1 H-NMR, 13 C-NMR and high-resolution mass spectroscopy, and are observed to have remarkably high solubility in common organic solvents. Their optical, thermal and electrochemical properties were measured. UV-vis absorption and emission spectral data on bis-silylated-, di-hexylated- and unsubstituted-thiophene-anthracene oligomers indicate that their absorption maxima are independent upon the presence of the kind of substitution in dilute solution while end-capped long-alkyl chain containing silyl groups enhance conjugation of arene backbone of the oligomers in solid film states. Absorption maxima of bis-quarterthienylanthracene in solution is closer to those obtained α,ω-dihexylsexithiophene (DH-6T). For oligomer bis-bithienylanthracene, bis-terthienylanthracene and bis-quarterthienylanthracene the main endothermic peaks are detected at 84 °C, 120 °C and 194 °C, respectively which indicate that the end-capped silyl groups lead to decrease about 100 °C comparing to the corresponding end-capped hexyl groups. Electrochemical measurements indicate that bis-silylated thiophene-anthracene oligomers have better oxidation stability than the corresponding oligothiophenes without anthracene core. Bis-quarterthienylanthracene 3 still has low HOMO level in spite that it contains totally nine arene rings in the oligomeric molecules.