Monothioindigo, determined by microcrystal structure analysis.

Indigo and thioindigo pigments are used for a wide range of applications. The crystal structure of the mixed compound monothioindigo [systematic name: (E)-2-(3-oxo-2,3-dihydro-1-benzothiophen-2-ylidene)-2,3-dihydro-1H-indol-3-one], C(16)H(9)NO(2)S, has been determined by microcrystal structure analysis from a crystal with a size of just 1 x 2 x 10 microm. The crystal structure of monothioindigo resembles those of indigo and thioindigo. The molecules show orientational disorder, with site-occupation factors of 0.962 (2) and 0.038 (2) for the major and minor disorder components, respectively. The indigo fragment donates an intermolecular hydrogen bond, leading to a criss-cross arrangement of molecules similar to that in indigo, whereas the thioindigo fragment exhibits only van der Waals interactions and molecular stacking, similar to that in thioindigo.