Crystal structures and Hirshfeld surface analyses of seven 7-aryl-4,7-dioxoheptanoic acids: differing carboxylic acid interactions leading to dimers, chains and three-dimensional arrays

Abstract

Abstract Crystal structures and Hirshfeld surface analysis are reported of seven aryl-CO–CH2CH2COCH2CH2CO2H derivatives, namely aryl=4-ClC6H4, 1: 2-HOC6H4, 2: (2,4-(MeO)2C6H3, 3: 3,5-Me2-4-MeOC6H2, 4: 4-MeC6H4, 5: C6H5, 6: 2,4-(HO)2C6H3, 7. There are significant differences in their molecular conformations and their crystal packing. Within the group of compounds, three different types of carboxylic acid intermolecular interactions are exhibited, all involving O–H···O hydrogen bonds. These three types are (i) symmetric R2 2(8) dimers formed from pairs of O–H···O hydrogen bonds in compounds 1–5, (ii) infinite 1D homo-assemblies of carboxylic groups (homo-AA,A catemers), and (iii), a 3-D array, in which there are no direct carboxylic acid–carboxylic acid interactions, generated from O–H···O interactions of each carboxylic acid group with the hydroxyl and carbonyl groups of other molecules in 7. Each of the carboxylic acid groups in the catemer exhibit anti arrangements with all the carboxylic acid oxygen atoms lying in a plane. Disorder is exhibited in the carboxylic acid groups in 2 and 6. With the variety of oxygen substituents present in 1–7, a large number of O–H···O and C–H···O hydrogen bonds are exhibited, resulting in all cases in three dimension assemblies. In 1–5, interlayer contacts between the carboxylic acid R2 2(8) dimers in rows, with differing sets of weaker C–H···O and/or C–H···π interactions, result in the formation of two-molecular wide columns and/or infinite sheets. While column and sheet sub structures can also be designated in compound 6, on linking the carboxylic acid groups with other substituents via C–H···O, C–H···π and C=O···π interactions, these differ from those in 1–5 due to the different arrangements of the CO2H groups.