A study of the crystal structures, supra-molecular patterns and Hirshfeld surfaces of bromide salts of hypoxanthine and xanthine.

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 inter-actions described by R 2 3(9) and R 2 2(8) synthons. The crystal packing is also consolidated by carbon-yl⋯π inter-actions between symmetry-related hypoxanthinium (HX+ ) cations in salt I and xanthinium cations (XA+ ) in salt II. The combination of all these inter-actions 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) .

Crystal structures and Hirshfeld surface analyses of hypoxanthine salts involving 5-sulfosalicylate and perchlorate anions.

Two salts of 1,9-di-hydro-purin-6-one (hypoxanthine), namely, 6-oxo-1,9-di-hydro-purin-7-ium 5-sulfosalicylate dihydrate, C5H5N4O+·C7H5O6S-·2H2O, (I), and 6-oxo-1,9-di-hydro-purin-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 mol-ecule is protonated at the N7 position of the purine ring. In salt (I), the cation and anion are connected through N-H⋯O inter-actions. 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 mol-ecule 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 inter-actions in salt (I) and C-O⋯π inter-actions in salt (II). The combination of several inter-actions leads to the formation of supra-molecular 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).

Crystal structure of 4-[(5-methyl-isoxazol-3-yl)amino-sulfon-yl]anilinium 3,5-di-nitro-salicylate.

The title mol-ecular salt, C10H12N3O3S(+)·C7H3N2O7 (-), protonation occurs at the amino N atom attached to the benzene ring of sulfamethoxazole. In the anion, there is an intra-molecular O-H⋯O hydrogen bond and the cation is linked to the anion by an N-H⋯O hydrogen bond. In the extended structure, the cations and anions are linked via N-H⋯O, N-H⋯N and C-H⋯O hydrogen bonds, forming a three-dimensional framework.

Hydrogen bonding patterns in salts of derivatives of aminopyrimidine and thiobarbituric acid.

Three salts, namely 2-amino-4,6-dimethylpyrimidin-1-ium thiobarbiturate trihydrate (I), 2-amino-4,6-dimethoxypyrimidin-1-ium thiobarbiturate dihydrate (II) and 2,4-diamino-5-(3',4',5'-trimethoxybenzyl)pyrimidin-1-ium thiobarbiturate (III), were synthesized and characterized by IR and X-ray diffraction techniques. The primary interaction between the acid and base happens via N-H...O hydrogen bonds in (II) and (III), and via water-mediated N-H...OW and OW-HW...S in (I). The water molecules present in compound (I) form a (H2O)12 water cluster via water-water interactions. In all three compounds (I)-(III), thiobarbiturate anions form self-complementary pairs with a robust R2(2)(8) motif via a pair of N-H...O/N-H...S hydrogen bonds. They mimic the nucleobase base pairs by utilizing the same groups (thymine/uracil uses N3-H and C4=O8 groups during the formation of Watson-Crick and Hoogsteen base pairs with adenine). Compound (I) forms a water-mediated base pair through N-H...OW hydrogen bonds and forms an R4(2)(12) motif. The formation of N-H...S hydrogen bonds, water-mediated base pairs and water-water interactions in these crystal systems offers scope for these systems to be considered as a model in the study of hydration of nucleobases and water-mediated nucleobase base pairs in macromolecules.

Hydrogen-bonding patterns in pyrimethaminium pyridine-3-sulfonate.

IN THE ASYMMETRIC UNIT OF THE TITLE SALT [SYSTEMATIC NAME: 2,4-diamino-5-(4-chloro-phen-yl)-6-ethyl-pyrimidin-1-ium pyri-dine-3-sulfonate], C(12)H(14)N(4)Cl(+)·C(5)H(4)NSO(3) (-), there are two independent pyrimethaminium cations and two 3-pyridine sulfonate anions. Each sulfonate group inter-acts with the corresponding protonated pyrimidine ring through two N-H⋯O hydrogen bonds, forming a cyclic hydrogen-bonded bimolecular R(2) (2)(8) motif. Even though the primary mode of association is the same, the next higher level of supra-molecular architectures are different due to different hydrogen-bonded networks. In one of the independent molecules in the asymmetric unit, the pyrimethamine cation is paired centrosymmetrically through N-H⋯N hydrogen bonds, generating an R(2) (2)(8) ring motif. In the other molecule, the pyrimethamine cation does not form any base pairs; instead it forms hydrogen bonds with the 3-pyridine sulfonate anion. The structure is further stabilized by C-H⋯O, C-H⋯N and π-π stacking [centroid-centroid distance = 3.9465 (13) Å] inter-actions.