Bisamide der Quadratsäure

The structures of the title compounds2,5 and6 were determined by single crystal X-ray methods at room temperature (2) and at 140 K (5 and6). The molecules contain approximately planar C₄N₂O₂ (or C₄N₂OS) groups with considerable C-N, C-O and C-S--bonding. The C-C bond distances in the four membered rings of the 2,4-bisamides (squaraines)5 and6 vary between 143.9 (6) and 146.9 with a mean value of 145.8 pm. In the 3,4-bisamide2 the cyclobutendionestructure is more pronounced with d(C-C) ranging from 142.5 (4) to 148.8 (5) pm. The packing mode of2,5 and6 are related by group-subgroup relations.