Different N—H⋯π inter­actions in two indole derivatives

We describe the syntheses and crystal structures of two indole derivatives, namely 6-isopropyl-3-(2-nitro-1-phenyl­eth­yl)-1H-indole, C(19)H(20)N(2)O(2), (I), and 2-(4-meth­oxy­phen­yl)-3-(2-nitro-1-phenyl­eth­yl)-1H-indole, C(23)H(20)N(2)O(3), (II); the latter crystallizes with two mol­ecules (A and B) with similar conformations (r.m.s. overlay fit = 0.139 Å) in the asymmetric unit. Despite the presence of O atoms as potential acceptors for classical hydrogen bonds, the dominant inter­molecular inter­action in each crystal is an N—H⋯π bond, which generates chains in (I) and A+A and B+B inversion dimers in (II). A different aromatic ring acts as the acceptor in each case. The packing is consolidated by C—H⋯π inter­actions in each case but aromatic π–π stacking inter­actions are absent.