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 generateR22(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.