Selenium-containing π-conjugated compounds for electronic molecular materials

Novel selenium-containing π-conjugated compounds have been studied for the development of organic metals, superconductors, and field-effect- transistors. Methylenedithiotetraselenafulvalene (MDT-TSF) and its related electron donors are effectively synthesized by the recently developed synthetic method consisting of the one-pot formation of 1,3-diselenole-2-selones, the deprotection/realkylation procedure of the protected tetrachalcogenafulvalene- thiolate and -selenolate, and the ring closing reaction via trans-alkylation on sulfur or selenium atom. These new compounds serve as good electron donors for developing not only highly conducting charge-transfer salts (>10³ S cm^-1) but also superconducting salts. Among six selenium-containing methylenedichalcogeno-tetrachalcogenafulvalenes, we found that four of them can produce superconducting salts, indicating that the present compounds are superior class of electron donors. For the development of high-performance organic semiconductors for organic field effect transistor (OFET) devices, we focused our attention to selenophene-containing acene-type compounds, namely benzo[1,2-b:4,5-b′]diselenophene (BDS) derivatives hitherto unknown. A new synthetic method for BDS derivatives consisting of double heterocycle-formation on the central benzene ring has been established and has made it possible to synthesize a range of BDS derivatives. Among them, 2,6-diphenyl derivative (DPh-BDS) shows very high hole mobility of 0.17 cm² / Vs, which is classified into the highest class of field-effect mobility of organic thin films.