Novel donor-π-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.