The title compound, C6H2N3O7 −·C10H13Cl2N2 +, crystallizes with one 1-(2,3-dichloro-phenyl)piperazine (DP) cation and one picrate (PA) anion in the asymmetric unit. In the crystal structure, the DP cation and PA anion are interconnected via several N—H...O and C—H...O hydrogen bonds. The DP cation and PA anion are further connected through C—Cl...π [3.8201 (4), 3.7785 (4) Å] and N—O...π [3.7814 (4) Å] interactions. The DP cations are further interconnected via a weak intermolecular Cl...Cl [3.2613 (4) Å] halogen–halogen interaction. The combination of these supramolecular interactions leads to a herringbone like supramolecular architecture.

The asymmetric unit of the title coordination polymer [Zn(C9H6NO2)2(C10H8N4)] n , consists of one ZnII cation, one bidentate 1H-indole-5-carboxylate (I5C) anion and half of a 4,4′-azobipyridine (Abpy) neutral ligand. In the coordination polyhedron, the ZnII ion adopts a distorted octahedral geometry. The coordination polymer is stabilized by a combination of N—H...O and C—H...π interactions, which leads to the formation of wave-like two-dimensional coordination polymeric layers.

Two salts of 1,9-dihydropurin-6-one (hypoxanthine), namely, 6-oxo-1,9-dihydropurin-7-ium 5-sulfosalicylate dihydrate, C5H5N4O+·C7H5O6S−·2H2O, (I), and 6-oxo-1,9-dihydropurin-7-ium perchlorate monohydrate, C5H5N4O+·ClO4 −·H2O, (II), have been synthesized and characterized using single-crystal X-ray diffraction and Hirshfeld analysis. In both salts, the hypoxanthine molecule is protonated at the N7 position of the purine ring. In salt (I), the cation and anion are connected through N—H...O interactions. The protonated hypoxanthine cations of salt (I) form base pairs with another symmetry-related hypoxanthine cation through N—H...O hydrogen bonds with an R 2 2(8) ring motif, while in salt (II), the hypoxanthine cations are paired through a water molecule via N—H...O and O—H...N hydrogen bonds with an R 3 3(11) ring motif. The packings within the crystal structures are stabilized by π–π stacking interactions in salt (I) and C—O...π interactions in salt (II). The combination of several interactions leads to the formation of supramolecular sheets extending parallel to (010) in salts (I) and (II). Hirshfeld surface analysis and fingerprint plots reveal that O...H/H...O contacts play the major role in the crystal packing of each of the salts, with a 54.1% contribution in salt (I) and 62.3% in salt (II).

Creatinine, a biologically important compound, is used to analyze kidney function and kidney diseases in the human body. The salt form of creatinine is used in the formation of drug materials like anti-HIV, antifungal, antiprotozoal, antiviral and antitumour compounds. Here we report the solid-state structures of three new crystalline salts, namely, creatininium (2-amino-1-methyl-4-oxo-4,5-dihydro-1H-imidazol-3-ium) bromide, C4H8N3O+·Br−, (I), creatininium 3-aminobenzoate, C4H8N3O+·C7H6NO2 −, (II), and creatininium 3,5-dinitrobenzoate, C4H8N3O+·C7H3N2O6 −, (III). These salts have been synthesized and characterized by single-crystal X-ray diffraction and Hirshfeld surface analysis. The structural chemistry of salts (I)–(III) and their crystal packing are discussed in detail. The primary interaction between the creatinine cation and the acid anion in the three salts is N—H...Br/O hydrogen bonds. In salt (I), the creatinine cation and bromide anion are connected through a pair of N—H...Br hydrogen bonds forming R 4 2(8) and R 4 2(12) ring motifs. In salts (II) and (III), the creatinine cation interacts with the corresponding anion via a pair of N—H...O hydrogen bonds. The crystal structure is further stabilized by C—H...O and O—H...O hydrogen bonds with the ring motifs R 2 2(8), R 2 1(7) and R 2 1(6). Furthermore, the crystal structures are stabilized by π–π, C—H...π, C—O...π and N—O...π stacking interactions. The contributions made by each hydrogen bond in maintaining the crystal structure stability has been quantified by Hirshfeld surface analysis.

Two new crystalline salts, namely, hypoxanthinium bromide monohydrate, C5H5N4O+·Br−·H2O (I) and xanthinium bromide monohydrate, C5H5N4O2 +·Br−·H2O (II), were synthesized and characterized by single-crystal X-ray diffraction technique and Hirshfeld surface analysis. The hypoxanthinium and xanthinium cations in salts I and II are both in the oxo-N(9)–H tautomeric form. The crystal packing of the two salts is governed predominantly by N–H...O, N–H...Br, C–H...Br and O–H...Br interactions described by R 2 3(9) and R 2 2(8) synthons. The crystal packing is also consolidated by carbonyl...π interactions between symmetry-related hypoxanthinium (HX+ ) cations in salt I and xanthinium cations (XA+ ) in salt II. The combination of all these interactions leads to the formation of wave- and staircase-like architectures in salts I and II, respectively. The largest contributions to the overall Hirshfeld surface are from Br...H/H...Br contacts (22.3% in I and 25.4% in II) .