Crystal structures and Hirshfeld analysis of 4,6-di-bromo-indole-nine and its quaternized salt.

4,6-Di-bromo-2,3,3-trimethyl-3H-indole, C11H11Br2N, exists as a neutral mol-ecule in the asymmetric unit. The asymmetric unit of 4,6-di-bromo-2,3,3-trimethyl-3H-indol-1-ium iodide, C12H14Br2N+·I-, contains one organic cation and one iodine anion. The positive charge is localized on the quaternized nitro-gen atom. In the crystal, mol-ecules of 4,6-di-bromo-indole-nine are linked by C-Br⋯π halogen bonds, forming zigzag chains propagating in the [001] direction. The mol-ecules of the salt form layers parallel to the (010) plane where they are linked by C-H⋯Br hydrogen bonds, C-Br⋯Br and C-Br⋯I halogen bonds. The Hirshfeld surface analysis and two dimensional fingerprint plots were used to analyse the inter-molecular contacts present in both crystals.