Shortcut to highly π-extended optoelectronic systems based on the dibenzothiophene core

Abstract

The Scholl reaction stands as a versatile tool to synthetize multiple π-extended systems via intramolecular C–C oxidative couplings. A prime example is the expansion of dibenzothiophene to polycyclic butterfly-shaped heterocycles, which claim key characteristics in diverse optoelectronic applications. Herein we describe a protocol from commercial tetrabromothiophene based on sequential one-pot Suzuki–Miyaura reactions followed by the Scholl reaction. This strategy permits rapid access to complex constructions fusing up to 11 rings in just two steps and improved yields. The proposed π-extensions successfully reduced the HOMO energy levels in the solid state to align with the gold work function (5.1 eV), while offering tunable photophysical properties. Remarkably, phenanthrene as scaffold endowed the core with a hole mobility value of 7 × 10⁻⁵ cm² V⁻¹ s⁻¹ in OTFTs and excellent air-stability, with a shelf lifetime exceeding one year. Moreover, the inclusion of sulfurated units unlocked room temperature phosphorescence under oxygen-free conditions, a highly sought-after characteristic in metal- and halogen-free constructions. Their RTP quantum yields when introduced into a Zeonex matrix are as high as 14%, with oxygen-sensitive photoluminiscence that goes from deep-blue to yellow-orange. Altogether, this strategy holds great potential and versatility in developing adaptable materials for multiple functionalities.