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]

Abstract

The X-ray structure analyses of the title compounds 1 and 2 were performed. 1: monoclinic, C 2/c, a = 9.532(2), b = 11.469(2), c = 7.030(3) Å, β = 110.58(2)°, Z = 4; 2: monoclinic, P21/a, a = 7.650(2), b = 7.729(2), c = 12.948(3) Å, β = 74.26(2)°, Z = 4. The structure of 1 was solved by direct methods, that of 2 by Patterson- and successive Fourier-synthesis techniques. The least squares refinement converged for 894 independent reflections with I > 2δI to an R-value of 0.032 (Rw = 0.035) in the case of 1 and for 1440 independent reflections to an R-value of 0.045 (Rw = 0.045) in the case of 2. The bond lengths in the [1,2,5]thiadiazole rings in 1 and 2 and also in the Se-homologous ring in 2 indicate to a quasi-aromatic π-system, whereas the aromatic character of the central benzene ring in 1 and 2 is strongly disturbed. The substitution of one S by the homologous Se in 2 induces significant changes of comparable bond lengths in 1 and 2. In the crystal structures of both compounds molecular layers and columnar stacks are formed. Quasipolymers in form of ribbon like structures are established in 1 by short S···N contacts and in 2 by short Se···N contacts. In 2 (SeN2)x-chains are formed.