A comparison of X-ray crystal structures including methyl 3,5-bis(hydroxymethyl)benzoate, its phenylethynyl extended derivative in polymorphous forms and the corresponding carboxylic acids

Abstract

Considering the specific supramolecular synthon design of carboxylic acid and alcoholic hydroxyl groups in the field of crystal engineering, we compared the solid state structures of particular benzoates and corresponding acids 1–4 both in the non-spacered (1, 2) and spacered (3, 4) forms. Based on the single crystal X-ray study, there is only a slight influence of the phenylacetylene spacer with regard to the layer lattice arrangement of the benzoates while referring to the benzoic acid analogues the addition of the spacer gives rise to a modification of the lattice from a layer to a tape structure. Dependent on the crystallization conditions, two crystalline polymorphs of compound 3 (3a, 3b) were obtained and discussed regarding their structural differences.