Efficient Synthesis of π-Conjugated Organic Molecules Utilizing Cross-Coupling Reactions and Application to Electronic Devices

The development of efficient synthetic methods of pi-conjugated compounds by means of cross-coupling reactions are reported. Tetraarylethenes with four different substituents are synthetic targets. The Pt-catalyzed addition of diboron to alkynylsilanes to yield 1-aryl-1-silyl-2,2-diborylethenes with perfect stereoselectivity. Step by step chemoselective Suzuki-Miyaura couplings with aryl halides were performed to give a triarylsilylethene with perfect chemoselectivity. The silyl group was transformed to the aryl group with desilybromination, followed by Suzuki-Miyaura coupling, leading to the successful synthesis of the desired tetraarylated olefin. On the other hand, novel and versatile methods for the synthesis of various phenacene and thienophenacene derivatives by cross-coupling reactions were elucidated for application to organic field-effect transistors (OFETs) and organic photovoltaics (OPVs). As one of representative phenacenes, picene is a polycyclic aromatic hydrocarbon consisting of five fused benzene rings with a W-shape structure, which exhibits high hole mobility. We successfully found the synthetic route of various substituted picenes. In addition, the synthesis of phenanthro [1,2-b: 8,7-b'] dithiophene (PDT) was achieved by replacing two terminal phenyl rings in picene with thiophene rings. The fabricated OFET devices based on C-12-PDT-2 displayed a quite high mobility of up to 5.6 cm(2) V-1 s(-1). In regard to OPV devices, PDT-fluorinated benzothiadiazole (BT) polymers possessing alkyl side chains showed the highest power conversion efficiencies (PCE) of 9.0%.