Die Kristallstrukturen des Benzo[1.2-c:3.4-cʹ]bis[1.2.5]thiadiazols und des semihomologen [1.2.5]Selenadiazolo[3.4-e]-2.1.3-benzothiadiazols [1]/The Crystal Structures of the Benzo [1,2-c : 3,4-cʹ]bis[1,2,5]thiadiazole and of the Semihomologous [1,2,5]Selenadiazolo[3,4-e]-2,1,3-benzothiadiazole [1]