Crystal structures of four co-crystals of (E)-1,2-di(pyridin-4-yl)ethene with 4-alkoxybenzoic acids: 4-methoxybenzoic acid-(E)-1,2-di(pyridin-4-yl)ethene (2/1), 4-ethoxybenzoic acid-(E)-1,2-di(pyridin-4-yl)ethene (2/1), 4-n-propoxybenzoic acid-(E)-1,2-di(pyridin-4-yl)ethene (2/1) and 4-n-butoxybenzoic acid-(E)-1,2-di(pyridin-4-yl)ethene (2/1)

Abstract

The crystal structures of four hydrogen-bonded co-crystals of 4-alkoxybenzoic acid-(E)-1,2-di(pyridin-4-yl)ethene (2/1), namely, 2C8H8O3·C12H10N2, (I), 2C9H10O3·C12H10N2, (II), 2C10H12O3·C12H10N2, (III) and 2C11H14O3·C12H10N2, (IV), have been determined at 93 K. In compounds (I) and (IV), the asymmetric units are each composed of one 4-alkoxybenzoic acid molecule and one half-molecule of (E)-1,2-di(pyridin-4-yl)ethene, which lies on an inversion centre. The asymmetric unit of (II) consists of two crystallographically independent 4-ethoxybenzoic acid molecules and one 1,2-di(pyridin-4-yl)ethene molecule. Compound (III) crystallizes in a non-centrosymmetric space group (Pc) and the asymmetric unit comprises four 4-n-propoxybenzoic acid molecules and two (E)-1,2-di(pyridin-4-yl)ethane molecules. In each crystal, the acid and base components are linked by O - H⋯N hydrogen bonds, forming a linear hydrogen-bonded 2:1 unit of the acid and the base. In (I), (II) and (III), intermolecular C - H⋯O interactions are observed. The 2:1 units of (I) and (II) are linked via C - H⋯O hydrogen bonds, forming tape structures. In (III), the C - H⋯O hydrogen bonds, except for those formed in the units, link the two crystallographically independent 2:1 units. In (IV), no C - H⋯O interactions are observed, but π-π and C - H⋯π interactions link the units into a column structure.