Crystal structure of the supramolecular system of indole-2,3-dione 1-(2-oxopropyl)-3-ethylene ketal and its thiosemicarbazone

The crystal structure of a supramolecular system consisting of indole-2,3-dione 1-(2-oxopropyl)-3-ethylene ketal (I) and indole-2,3-dione 1-(2-oxopropyl)-3-ethylene ketal thiosemicarbazone (II) molecules that are linked together by hydrogen bonds is determined using X-ray diffraction. The crystal is monoclinic, and the unit cell parameters are as follows: a = 12.8360(3) Å, b = 10.7330(3) Å, c = 19.4610(3) Å, β = 99.566(1)°, space group P2₁/c, and Z = 4 (C₂₇H₂₉N₅O₇S). In molecules I and II, the indole-2,3-dione 3-ethylene ketal fragments have a virtually identical structure. The pyrrole and dioxolane fragments are spiro-linked through the carbon atom with a dihedral angle close to 90°. The adjacent pyrrole and benzene rings are coplanar to within 4.4°. In molecule II, the oxygen atom of the dioxolane fragment and the terminal nitrogen atom of the thiosemicarbazide fragment are involved in the N-HïO intramolecular hydrogen bond 3.294(2) Å]. The key role in the formation of the crystal structure is played by intermolecular hydrogen bonds of the N-H?dO, C-H?O, C-H?N, and N-H?S types.