The crystal structures, Hirshfeld surface analyses and energy frameworks of 8-{1-[3-(cyclopent-1-en-1-yl)benzyl]piperidin-4-yl}-2-methoxyquinoline and 8-{4-[3-(cyclopent-1-en-1-yl)benzyl]piperazin-1-yl}-2-methoxyquinoline

The title compounds, 8-{1-[3-(cyclopent-1-en-1-yl)benzyl]piperidin-4-yl}-2-methoxyquinoline, C27H30N2O (I), and 8-{4-[3-(cyclopent-1-en-1-yl)benzyl]piperazin-1-yl}-2-methoxyquinoline, C26H29N3O (II), differ only in the nature of the central six-membered ring: piperidine in I and piperazine in II. They are isoelectronic (CH cf. N) and isotypic; they both crystallize in the triclinic space group P with very similar unit-cell parameters. Both molecules have a curved shape and very similar conformations. In the biaryl group, the phenyl ring is inclined to the cyclopentene mean plane (r.m.s. deviations = 0.089 Å for I and 0.082 Å for II) by 15.83 (9) and 13.82 (6)° in I and II, respectively, and by 67.68 (6) and 69.47 (10)°, respectively, to the mean plane of the quinoline moiety (r.m.s. deviations = 0.034 Å for I and 0.038 Å for II). The piperazine ring in I and the piperidine ring in II have chair conformations. In the crystals of both compounds, molecules are linked by C-H⋯π interactions, forming chains in I and ribbons in II, both propagating along the b-Axis direction. The principal contributions to the overall Hirshfeld surfaces involve H⋯H contacts at 67.5 and 65.9% for I and II, respectively. The major contribution to the intermolecular interactions in the crystals is from dispersion forces (E dis), reflecting the absence of classical hydrogen bonds.