Consistent supramolecular motif of C(7) O - H⋯O hydrogen-bonded chains and different local symmetries in three isoindole-4-carboxylic acid derivatives

The syntheses and structures of (3aRS,4RS,9aSR)-3-oxo-2-(2-phenylethyl)-2,3,3a,4,9,9a-hexahydro-1H-benzo[f]isoindole-4-carboxylic acid, C21H21NO3 (I), (3aRS,4RS,9aSR)-3-oxo-2-(propan-2-yl)-2,3,3a,4,9,9a-hexahydro-1H-benzo[f]isoindole-4-carboxylic acid, C16H19NO3 (II) and (4RS)-3-oxo-2-phenyl-2,3,4,9-tetrahydro-1H-benzo[f]isoindole-4-carboxylic acid, C19H15NO3 (III), are described. Compound (I) crystallizes with two molecules in the asymmetric unit. In the extended structures of (I), (II) and (III) the molecules are linked by Oc - H⋯Oi (c = carboxylic acid, i = indole) hydrogen bonds, forming a common C(7) zigzag chain motif propagating along the [010] direction, despite the different local symmetries. These chains are connected by weak C - H⋯O and C - H⋯π interactions, forming a three-dimensional network in each case. A Hirshfeld surface analysis was undertaken to investigate and quantify the intermolecular interactions, which are dominated by H⋯H, C⋯H/H⋯C and O⋯H/H⋯O contacts in each case. © 2026 Alekseeva et al.