Synthesis and properties of new PDT- and TPDT-TTP analogues

2-(1,3-Diselenol-2-ylidene)-5-(pyran-4-ylidene)-1,3,4,6-tetrathiapentalene (PDS-TTP), its thiopyran analogue (TPDS-TTP), and their bis(methylthio) derivatives have been prepared. Their first and second oxidation potentials are comparable to those of the corresponding sulfur analogues. The PF6 and AsF6 salt of PDS-TTP displayed metallic conductivity down to 4.2 K, and TCNQ complex was semiconductor with a low activation energy (0.006 eV).