Abstract
The crystal structures of four hydrogen-bonded co-crystals of 4-alk-oxy-benzoic 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-alk-oxy-benzoic acid mol-ecule and one half-mol-ecule 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-eth-oxy-benzoic acid mol-ecules and one 1,2-di(pyridin-4-yl)ethene mol-ecule. Compound (III) crystallizes in a non-centrosymmetric space group (Pc) and the asymmetric unit comprises four 4-n-propoxybenzoic acid mol-ecules and two (E)-1,2-di(pyridin-4-yl)ethane mol-ecules. 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), inter-molecular C-H⋯O inter-actions 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 inter-actions are observed, but π-π and C-H⋯π inter-actions link the units into a column structure.
Highlights
(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 halfmolecule of (E)-1,2-di(pyridin-4-yl)ethene, which lies on an inversion centre
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
Summary
Co-crystals of 4-alkoxybenzoic acid–4,40 -bipyridyl (2/1) and 4alkoxybenzoic acid–(E)-1,2-di(pyridin-4-yl)ethene [common name: trans-1,2-bis(4-pyridyl)ethylene] (2/1), in which the two acids and the base are held together by hydrogen bonds, exhibit thermotropic liquid crystallinity (Kato et al, 1990, 1993; Grunert et al, 1997). Similar co-crystals of 4-alkoxybenzoic acid–1,2-bis(pyridin-4-yl)ethane (2/1) show thermotropic liquid crystallinity, namely, nematic phases at. A phase at 413 K and a nematic phase at 419 K for the compound of 4-n-butoxybenzoic acid (Tabuchi et al, 2015a). 4-methoxybenzoic acid (Mukherjee & Desiraju, 2014; Ramon et al, 2014), the three compounds of 4,40 -bipyridyl with. E72, 1666–1671 research communications et al, 2015b), the compound of 1,2-bis(pyridin-4-yl)ethane with 4-methoxybenzoic acid (Mukherjee & Desiraju, 2014). The three compounds of 1,2-bis(pyridin-4-yl)ethane with with 4-ethoxy-, 4-n-propoxy- and 4-n-butoxybenzoic acid (Tabuchi et al, 2015a) have been reported. As an expansion of our work on the structural characterization of hydrogenbonded co-crystals which exhibit liquid phases, we have prepared four compounds of 4-alkoxybenzoic acid–(E)-1,2di(pyridin-4-yl)ethene (2/1) and analyzed the crystal structures
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