Synthesis, molecular and crystal structure analysis of 1-(4-Methylbenzenesulfonyl)indole-3-carbaldehyde and DFT investigation of its rotational conformers.

Two independent molecules that differ in terms of rotation about the central S-N bond comprise the asymmetric unit of the title compound 1. The molecules have a V-shape with the dihedral angles between the fused ring system and benzene ring being 79.08(6)° and 72.83(5)°, respectively. The packing is mostly driven by p···p interactions occurring between the tolyl ring of one molecule and the C6 ring of the indole fused ring system of the other. DFT and IRC calculations for these and related 1-(arylsulfonyl)indole molecules showed that the rotational barrier about the S-N bond between conformers is within the 2.5-5.5 kcal/mol range. Crystal data for C16H13NO3S (1): Mr = 299.33, space group Pna21, a = 19.6152(4) Å, b = 11.2736(4) Å, c = 12.6334(3) Å, V = 2793.67(13) Å3, Z = 8, Z' = 2, R = 0.034.