Synthesis, physical properties, and OFET characteristics of a propeller-shaped molecule with a dithiarubicene blade

Abstract

In order to control the orientation of the π-conjugated system on the substrate, we focused on the molecular shape and synthesized a quasi-3D molecule (Tris-DDB) having a propeller structure as well as two reference molecules. While the optical properties of the three molecules were similar to each other, significant differences were observed in thermal properties affected by the intermolecular interaction, which were investigated by differential scanning calorimetry (DSC) measurement. The phase transition behavior and isotropic temperature depended on the molecular shape and Tris-DDB showed the highest thermal stability. After the thermal annealing, an OFET device based on Tris-DDB exhibited the highest charge carrier mobilities (μ_h = 1.7 × 10⁻⁴ cm² V⁻¹ s⁻¹ and μ_e = 1.2 × 10⁻⁴ cm² V⁻¹ s⁻¹) among the three molecules. X-ray diffraction (XRD) measurements revealed that Tris-DDB selectively adopts an edge-on orientation on the substrate, demonstrating that the propeller structure is effective in controlling the molecular orientation of the π-conjugated system.