Quaternary and senary sub-assemblies in cocrystals and salts of quinoline-4-carbaldoxime with aromatic carboxylic acids

Abstract

Quaternary sub-assemblies in cocrystals and salts of quinoline-4-carbaldoxime with aromatic carboxylic acids are analysed. Quinoline-4-carbaldoxime formed a 1 : 1 cocrystal with 2-methylbenzoic acid, whereas with 2-hydroxybenzoic acid, 3-nitrobenzoic acid, 4-nitrobenzoic acid, 2,3- or 2,4-dihydroxybenzoic acid, it formed 1 : 1 salts. A ternary cocrystal with 2-nitrobenzoic acid composed of a neutral 2-nitrobenzoic acid and 2-nitrobenzoate with protonated quinoline-4-carbaldoxime is observed. Accommodation of additional neutral 2-nitrobenzoic acid is due to the extension of quaternary sub-assemblies to senary sub-assemblies to achieve an appropriate packing pattern. Whereas, assemblies of hydrated salts can be considered to comprise senary sub-assemblies formed between water molecules and quaternary sub-assemblies. In such senary sub-assemblies, water molecules are held in the hydrophobic junctions formed by oximes and carboxylic acids.