Crystal structures of three zinc(II) halide coordination complexes with quinoline N-oxide

The reaction of one equivalent of zinc(II) halide with two equivalents of quinoline N-oxide (QNO) in methanol yields compounds as ZnX (2)(QNO)(2), where X = Cl (I), Br (II) and I (III), namely, di­chlorido­bis­(quinoline N-oxide-κO)zinc(II), [ZnCl(2)(C(9)H(7)NO)(2)], di­bromido­bis­(quinoline N-oxide-κO)zinc(II), [ZnBr(2)(C(9)H(7)NO)(2)], and di­iodido­bis­(quinoline N-oxide-κO)zinc(II) [ZnI(2)(C(9)H(7)NO)(2)]. In all three complexes, Zn cations are coordinated by two QNO ligands bound through the oxygen atoms and two halide atoms, with X—Zn—X bond angles ca 20° wider than the O—Zn—O, giving rise to a distorted tetra­hedral geometry. Crystals of (II) and (III) are isostructural and both show pairwise π-stacking of QNO ligands and weak C—H⋯X hydrogen bonds, while (I) packs differently, with a shorter C—H⋯Cl bond and without π-stacking.