New Examples of Donor–Acceptor Conjugated Systems Involving the 1,3-Dithiole Moiety

The crystal structures of 6-(4,5-dimethyl-2H-1,3-dithiol-2-ylidene)-6,7-dihydro-5H-dibenzo[a,c]cycloheptene-5,7-dione, C20H14O2S2, and 6-(4,5,6,7-tetrahydro-2H-1,3-benzodithiol-2-ylidene)-6,7-dihydro-5H- dibenzo[a,c]cycloheptene-5,7-dione, C22H16O2S2, have been determined. Strong intramolecular interactions are observed between the carbonyl groups of the seven-membered ring and the S atoms of the 1,3-dithiole ring.