Crystal structures of three N-(3-acetyl­phen­yl)quinoline-2-carboxamides

In the title compounds, N-(5-acetyl-2-methyl-phen-yl)quinoline-2-carboxamide [C19H16N2O2, (I)], N-(5-acetyl-2-bromo-phen-yl)quinoline-2-carboxamide [C18H13BrN2O2, (II)] and N-(5-acetyl-2-ethynylphen-yl)quinoline-2-carboxamide [C20H14N2O2, (III)], the quinoline ring system is essentially planar and forms a dihedral angles of 3.68 (5) (I), 5.59 (7) (II) and 1.87 (6)° (III) with the acetyl-substituted ring. The mol-ecular structures of (I) and (III) each feature an intra-molecular N-H⋯N hydrogen bond, forming an S(5) ring, while in (II) an intra-molecular bifurcated N-H⋯(N,Br) hydrogen bond forms two S(5) rings. In the crystals, weak C-H⋯O hydrogen bonds link mol-ecules of (I) into C(7) chains long [010], mol-ecules of (II) into chains of R22(8) rings along [110] and mol-ecules of (III) into C(8) chains along [010]. In (I), there are no significant π-π stacking inter-actions under 4 Å, but in both (II) and (III), π-π inter-actions link the weak hydrogen-bonded chains into layers parallel to (001) [centroid-centroid disttances of 3.748 (1) Å in (II) and 3.577 (1), 3.784 (1) and 3.780 (1) Å in (III)].