Syntheses, Structures, and Properties of 2,3,6,7-Tetrathiabenzodipentalene and Its Methyl, Ethyl, Methylthio, and Ethylthio Derivatives: Novel Fused Polynuclear Heteroarenes

Article abstract of DOI:10.1246/bcsj.66.2033

The title heteroarene (TBD) isoelectronic with perylene was synthesized by way of a dimerization of thieno<2,3-b>thiophene.In addition, 1,4,5,8-tetramethyl, tetraethyl, tetrakis (methylthio), and tetrakis (ethylthio) derivatives were readily obtained from TBD.An X-ray crystallographic analysis of TBD demonstrated that the molecular structure is quite planar and symmetrical, but strained in the bond angles.The crystal structure comprises herringbone-type column stacking with intercolumnar heteroatomic interactions.TBD showed the same oxidation potential as did perylene , and like perylene, formed an iodine complex with a relatively high electrical conductivity of 0.11 S cm^-1.On the other hand, all of the TBD derivatives gave poorly conductive iodine complexes.In addition, TBD and the derivatives formed charge-transfer complexes with strong electron acceptors, such as 7,7,8,8-tetracyanoquinodimethane (TCNQ), 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (TCNQF4), 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), and 1,1,2,3,4,4-hexacyano-1,3-butadiene (HCBD).These ?-complexes, however, were mostly of low conductivity.The electrolyses of TBP gave powdery conductive polymers, whereas those of tetrakis (methylthio) TBD gave crystalline radical cation salts with conductivities of the order of 10^-3 S cm^-1.