Syntheses and Properties of 2,2′-Binaphtho[1,8-de]-1,3-dithiinylidene and Its Selenium Analog, 2-(1,3-Dithiol-2-ylidene)naphtho[1,8-de]-1,3-dithiin, and 2-(4H-Thiopyran-4-ylidene)naphtho[1,8-de]-1,3-dithiin

Abstract In order to discover new electron donors for conducting charge-transfer complexes, the four title compouds 1–4 composed of two heterocycles have been prepared via 1,8-dichalcogen-bridged naphthalene. The cyclic voltammetery indicates that symmetrical 1 and 2 are poor donors, but unsymmetrical 3 and 4 possess considerable donor abilities. The latter compounds are thus capable of forming some crystalline charge-transfer complexes with strong acceptors such as TCNQ, TCNQF4, and DDQ, which are, however, semi-conducting.