X-ray diffraction investigation of anthraquinonediazoles

Molecular Organization of 2,1,3-Benzothiadiazoles in the Solid State

“…Representative crystallographic studies have confirmed that the atoms of C, N, and S in the 2,1,3-benzothiadiazole core are essentially coplanar and that intramolecular bonding is well represented by quinoidal structure 1 . ,,− This preference is consistent with dipole moments measured for the increasingly polarized series of analogues naphthalene, quinoxaline ( 2 ), 2,1,3-benzothiadiazole ( 1 ), and 1,2-benzoquinone ( 3 ), which are 0, 0.51, , 1.8, and 4.2 D, − respectively. Previously published structural studies show that 2,1,3-benzothiadiazoles can engage in various intermolecular interactions, including π-stacking, dipole–dipole interactions, C–H···π interactions, C–H···N interactions, and S···N interactions. ,,− S···N interactions involving benzothiadiazoles can be considered to arise from various effects, including the electrostatic attraction of opposing partial charges and the interaction of S–N σ* orbitals with nonbonding orbitals centered on N. − The strength of S···N interactions appears to be similar to that of typical hydrogen bonds and has been calculated by dispersion-corrected DFT methods to be approximately 4 kcal/mol . However, the relative importance of various interactions characteristic of 2,1,3-benzothiadiazoles remains unclear, and there are no reports of extensive efforts to use these interactions to direct the crystallization of complex 2,1,3-benzothiadiazoles in predetermined ways.…”

“…Molecules of compound 4 are virtually planar and are linked to form undulating flat tapes by pairs of short coplanar S···N contacts (3.08 Å), as shown in Figure a. The S···N contacts are significantly shorter than the sum of the van der Waals radii (3.35 Å) and are characteristic features of the structures of many other 2,1,3-benzothiadiazoles. ,,− Short contacts do not necessarily correspond to bonding interactions, but the results of calculations and the widespread observation of short S···N contacts in the structures of other 2,1,3-benzothiadiazoles and related compounds provide strong evidence of an important directional bonding effect. The tapes observed in the structure of compound 4 are further linked by C–H···N interactions (2.61 Å) to create sheets (Figure a), which form π-stacks with a distance of 3.40 Å between the mean planes (Figure b).…”

The Nature of the Supramolecular Association of 1,2,5-Chalcogenadiazoles

“…The arrangement of these heterocycles is especially attractive as it leaves room for pendant functional groups. A survey of the Cambridge Structural Database (CSD) , was performed to identify those crystals where these features are observed. ,,− This provided the average SBI distances that are compared in Table to the sum of the corresponding van der Waals radii. The two sets of data follow opposite trends, suggesting that the tellurium SBIs are the strongest.…”