Weak interactions in the crystal structures of two indole derivatives

Abstract

We describe the syntheses and crystal structures of two indole derivatives, namely a second monoclinic polymorph of ethyl 5-chloro-1H-indole-2-carboxylate C11H10ClNO2, (I), and ethyl 5-chloro-3-iodo-1H-indole-2-carboxylate, C11H9ClINO2, (II). In their crystal structures, both compounds form inversion dimers linked by pairs of N-H⋯O hydrogen bonds, which generate R2 2(10) loops. The dimers are linked into double chains in (I) and sheets in (II) by a variety of weak interactions, including π-π stacking, C-I⋯π, C-Cl-π interactions and I⋯Cl halogen bonds.