Novel Donor–(pi)–Acceptor Compounds Containing 1,3-Dithiol-2-ylidene and Tetracyanobutadiene Units

The title donor–(pi)–acceptor compounds were prepared by the reaction of acetylenes containing a 1,3-dithiol-2-ylidene unit with tetracyanoethylene (TCNE). They showed amphoteric properties and intramolecular charge-transfer absorptions in the visible region. The molecular and crystal structures were revealed by X-ray analysis.