Structural insights into supramolecular interactions in isostructural salts of 2,4,6‐triaminopyrimidinium with various heterocyclic carboxylates.

2,4,6‐Triaminopyrimidine is an interesting and challenging molecule due to the presence of multiple hydrogen‐bond donors and acceptors. Its noncovalent interactions with a variety of carboxylic acids provide several supramolecular aggregates with frequently occurring molecular synthons. The present work focuses on the supramolecular interactions of 2,4,6‐triaminopyrimidinium 3‐(indol‐3‐yl)propionate–3‐(indol‐3‐yl)propionic acid (1/1), C4H8N5+·C11H10NO2−·C11H11NO2, (I), 2,4,6‐triaminopyrimidinium 2‐(indol‐3‐yl)acetate, C4H8N5+·C10H8NO2−, (II), 2,4,6‐triaminopyrimidinium 5‐bromothiophene‐2‐carboxylate, C4H8N5+·C5H2BrO2S−, (III), and 2,4,6‐triaminopyrimidinium 5‐chlorothiophene‐2‐carboxylate, C4H8N5+·C5H2ClO2S−, (IV). All four salts exhibit robust homomeric and heteromeric R22(8) ring motifs. Salts (I) and (II) develop sextuple [in (I)] and quadruple [in (I) and (II)] hydrogen‐bonded arrays through fused‐ring motifs. Salt (II) exhibits a rosette‐like architecture. Salt (IV) is isostructural and isomorphous with salt (III), exhibiting an identical crystal structure with a different composition and an identical supramolecular architecture. In salts (III) and (IV), a linear hetero‐tetrameric motif is formed and, in addition, both salts exhibit halogen–π interactions which enhance the crystal stability. All four salts develop a supramolecular hydrogen‐bonded pattern facilitated by several N—H...O and N—H...N hydrogen bonds with multiple furcated donors and acceptors. [ABSTRACT FROM AUTHOR]