Crystal structures and hydrogen bond analysis of five amino acid conjugates of terephthalic and benzene-1,2,3-tricarboxylic acids

Abstract

Four linear connecting amino acid derived ligands, 1–4, and one potentially three connecting, 5, were prepared by the reaction of the appropriate terephthaloyl dichloride or benzene-1,3,5-tricarbonyl trichloride with the methyl ester protected amino acid. Amino acids used here were alanine (1, 5), isoleucine (2), leucine (3) and valine (4). Crystalline forms of four amino acid substituted terephthalamides (2,2′-(terephthaloylbis(azanediyl))dipropanoic acid dihydrate 1; 2,2′-(terephthaloylbis(azanediyl))bis(3-methylpentanoic acid) monohydrate 2; 2,2′-(terephthaloylbis(azanediyl))bis(4-methylpentanoic acid) dihydrate 3; 2,2′-(terephthaloylbis(azanediyl))bis(3-methylbutanoic acid) dihydrate 4) and one benzene-1,3,5-tricarboxamide molecule (2,2′,2′′-((benzene-1,3,5-tricarbonyl)tris(azanediyl))tripropionic acid hemihydrate 5) were characterised and the single crystal structures were solved. All the compounds form hydrogen bonded 2D and 3D nets. Linear connecting amino acid derivatives can be categorised into three groups depending on the hydrogen bond patterns and final structures. Compounds 1 and 2 form 3D structures but the final structure is different due to the different hydrogen bond synthons. Compounds 3 and 4 are isostructural and form 2D hydrogen bonded structures while 5 forms a hydrogen bonded pcu-net. Intermolecular interactions have been analysed with Hirshfeld surfaces and graph set symbols.