Crystal structures of four indole derivatives with a phenyl substituent at the 2-position and a carbonyl group at the 3-position: the C(6) N—H...O chain remains the same, but the weak reinforcing interactions are different

Abstract

We describe the crystal structures of four indole derivatives with a phenyl ring at the 2-position and different carbonyl-linked substituents at the 3-position, namely 1-(2-phenyl-1H-indol-3-yl)ethanone, C16H13NO, (I), 2-cyclohexyl-1-(2-phenyl-1H-indol-3-yl)ethanone, C22H23NO, (II), 3,3-dimethyl-1-(2-phenyl-1H-indol-3-yl)butan-1-one, C20H21NO, (III), and 3-benzoyl-2-phenyl-1H-indole, C21H15NO, (IV). In each case, the carbonyl-group O atom lies close to the indole-ring plane and points towards the benzene ring. The dihedral angles between the indole ring system and 2-phenyl ring for these structures are clustered in a narrow range around 65°. The dominant intermolecular interaction in each case is an N—H...O hydrogen bond, which generates a C(6) chain, although each structure possesses a different crystal symmetry. The C(6) chains are consolidated by different (C—H...O, C—H...π and π–π stacking) weak interactions, with little consistency between the structures.

Keywords

• crystal structure
• indole
• N—H...O hydrogen bond
• C(6) chain
• weak interactions