Synthesis of Oligo(thienylfuran)s with Thiophene Rings at Both Ends and Their Structural, Electronic, and Field‐Effect Properties

Abstract

Oligo(thienylfuran)s with thiophene rings at both ends (SOSOSOS, DE-SOSOS, DH-SOSOS, DE-SOSOSOS, and DH-SOSOSOS; S and O denote thiophene and furan rings, respectively, DE and DH denote diethyl- and dihexyl-substituted, respectively) were newly synthesized by repetitive Stille coupling reactions. The UV/Vis maximum absorptions of the oligomers, SO, SOSO, SOSOS, SOSOSO, and SOSOSOS, exhibited a clear bathochromic shift with increasing number of heterocycles. The value of the oxidation peak potential (E(pa)1) determined by cyclic voltammetry decreased with an increase in the number of heterocycles by 0.06-0.08 V per heterocycle. The crystal-packing structures of DE-SOSOS and DH-SOSOS determined by X-ray crystallography have a herringbone motif and are denser than the reported structures of pentacene and alpha-sexithiophene. The morphologies of thin films prepared by vacuum deposition and spin coating were investigated by atomic force microscopy and X-ray diffraction. Among these films, those of DE-SOSOS and DH-SOSOS exhibited highly ordered arrangements. The devices based on vacuum-deposited and spin-coated films of DE-SOSOS and DH-SOSOS displayed the highest FET mobilities of 10(-2)-10(-3) cm2 V(-1) s(-1) among the oligomers reported in this study.