Synthesis and Properties of Novel Thiophene Polycyclic Aromatic Hydrocarbons Based on Pyrene and Their Radical Cations

Two new thiophene-modified pyrene derivatives, 4,5,9,10-tetra- (2-(5-methyl)thienyl)-2,7-di-tert-butylpyrene (1) and 4,5,9,10-tetra- (2-(5-methoxy)thienyl)-2,7-di-tert-butylpyrene (2), were designed and synthesized via Friedel–Crafts alkylation and Stille coupling reactions of pyrene. The stable monoradical cations 1•+ and 2•+ based on the thiophene-modified pyrene derivatives were generated by the one-electron oxidation of the pyrene-based thiophene polycyclic aromatic groups with Ag[Al(ORF)4] (ORF = OC(CF3)3). Their structures and properties were investigated using 1H nuclear magnetic resonance spectroscopy, ultraviolet–visible spectrophotometry, X-ray diffraction, density functional theory calculations, and electron paramagnetic resonance spectroscopy. The electron spin density was mainly concentrated on the pyrene ring, with a minor spillover to the peripheral thienyl moieties. Compound 1•+, which is the first reported monoradical cation of thiophene-modified pyrene, is expected to have broad application prospects in the fields of semiconductors and optoelectronic materials.