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 P1 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 A˚ for I and 0.082 A˚ 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 A˚ for I and 0.038 A˚ 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 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 HH 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 (Edis), reflecting the absence of classical hydrogen bonds.