Syntheses, physical properties and X-ray structures of benzocycloheptene-1,4,7-trione and its 6-phenylthio- and 6,8-bis(phenylthio) derivatives. Novel A, A–D and D–A–D molecular units aiming at organic conductors

Abstract

6-Phenylthio- and 6,8-bis(phenylthio)benzocycloheptene-1,4,7-triones 2 and 3 have been synthesized as prototypes for a new type of organic conductor. Their characteristic features of structures and physical properties are discussed in comparison with those of the parent trione 1 and related compounds. The single crystal X-ray analyses showed that a segregated column stacking existed in a crystal of 3 and a crystal of benzene adduct of 2, but not in 1 and pure 2. The pendant phenyl groups supported by sulfur atoms in 2 and 3 were found to be facing to the quinone carbonyl and may be responsible to the molecular arrangements in their crystals. Estimations of crystal structures by the crystal molecular packing analysis showed that the segregated column stacking was stable in 3, but unstable in 1. The derivatives of 3 seem to be potential candidates for organic conductors of D–A–D type.