-TETRAAZACYCLOPENT[CD]AZULENE-1[2H],4[3H]-DISELONE

The title compound, C19H18N4SSe2, crystallizes in the P (1) over bar s pace group with two molecules in the asymmetric unit. In both molecule s, the chemically equivalent halves are identical within experimental error, except for conformational differences which arise from intermol ecular interactions between the flexible seven-membered rings and surr ounding Se atoms. The central triheterapentalene system is almost plan ar, with individual ring conformations consistent with three regions o f conjugation separated by single bonds. The N-S bond lengths, stretch ed beyond the standard for a single bond, imply a three-centre interac tion.