2‐Ethyl­phenyl acridine‐9‐carboxyl­ate and 2,5‐dimethyl­phenyl acridine‐9‐carboxyl­ate

The title compounds, 2‐ethyl­phenyl acridine‐9‐carboxyl­ate, C₂₂H₁₇NO₂, (I), and 2,5‐dimethyl­phenyl acridine‐9‐carboxyl­ate, C₂₂H₁₇NO₂, (II), form triclinic and monoclinic crystals, respectively. Related by a centre of symmetry, adjacent molecules of (I) are linked in the lattice via a network of C—H·π and non‐specific dispersive interactions. As a result, acridine moieties and independent phenyl moieties of (I) are parallel in the lattice. The molecules of (II), arranged in a `head‐to‐tail' manner and related by a centre of symmetry, form pairs stabilized via C—H·π interactions. These are linked in the crystal via dispersive interactions. Acridine and independent phenyl moieties lie parallel within the pairs, while adjacent pairs are perpendicular, forming a herring‐bone pattern.