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The article presents a paper about hydrogen-bonded supramolecular motifs in 2-amino-4,6-dimethoxypyrimidinium picrate and pyrimethaminium picrate dimethyl sulfoxide solvate. It mentions the use of picric acid as an acidic ligand to form salts with polar biomolecules through specific electrostatic or hydrogen-bonding interactions. According to one study, hydrogen bonding plays an important role in molecular recognition and crystal engineering research.

In the crystal structure of the title compound, 2C6H9N3 C8H6O4, terephthalic acid has a crystallographic inversion centre and the dimethylpyrimidine molecule shows approximate non-crystallographic mirror and twofold rotation symmetry. The inversion-related pyrimidine molecules form a base pair [R2 2(8) ring motif] via a pair of NH⋯N hydrogen bonds. The carboxyl groups of terephthalic acid link the base pairs via OH⋯N and NH⋯O hydrogen bonds [R2 2(8) motif] to generate a supramolecular ribbon. [ABSTRACT FROM AUTHOR]

The title complex, {[Cd(NCS)2(H2O)2]·2C6H9N3} n, crystalizes in the triclinic space group P . The asymmetric unit contains one 2-amino-4,6-di­methyl­pyrimidine mol­ecule, a thio­cyanate ion, a water mol­ecule and a cadmium ion (site symmetry ). The cadmium ions are symmetrically doubly bridged by thio­cyanate ions, leading to a polymeric chain motif. The octahedral coordination geometry of cadmium is completed by a pair of inversion-related water mol­ecules. The 2-amino­pyrimidine mol­ecules are not coordinated to cadmium but are hydrogen-bonded to the coordinated water mol­ecules and thio­cyanate ions. There is also a pyrimidine–pyrimidine interaction via an N—H⋯N hydrogen bond. [ABSTRACT FROM AUTHOR]

In the title compound, C4H6N4O·C7H5NO4, there are two types of base-pairing motifs, one involving a pair of N—H...N hydrogen bonds and the other involving a pair of N—H...O hydrogen bonds. These paired molecules are further linked by N—H...O hydrogen bonds to generate DADA and DDAA ( D = donor and A = acceptor) arrays leading to a supramolecular sheet. [ABSTRACT FROM AUTHOR]

In the title compound, C12H14ClN4+·C6H4NO2−·H2O, the pyrimethamine molecule is protonated at one of the pyrimidine N atoms. The protonated N atom and 2-amino group of the cation interact with an adjacent nicotinate anion through a pair of N—H...O hydrogen bonds [graph set R22(8)]. The cation, anion and water molecule form a hydrogen-bonded ring motif with graph-set notation R42(8). The crystal structure is further stabilized by N—H...O and O—H...O hydrogen bonds and π–π interactions [centroid–centroid distance = 3.637 (6) Å]. [ABSTRACT FROM AUTHOR]

In 2,4-diamino-5-( p-chlorophenyl)-6-ethylpyrimidinium hydrogen adipate, C12H14ClN4+·C6H9O4−, the protonated pyrimethamine cation interacts with the carboxylate group of the adipate ion through N—H...O hydrogen bonds, forming a cyclic hydrogen-bonded R22(8) motif. The carboxyl and carboxylate groups of the adipate ions are linked through O—H...O hydrogen bonds in a head-to-tail fashion, forming a chain. Anions and cations are further connected by an extensive network of N—H...O hydrogen bonds. [ABSTRACT FROM AUTHOR]

In the crystal structure of the title compound [systematic name: 2,4-diamino-5-(4-chlorophenyl)-6-ethylpyrimidin-1-ium 3,5-dinitrobenzoate], C12H14ClN4+·C7H3N2O6−, the pyrimethamine molecule is protonated at one of the pyrimidine N atoms. The carboxylate group of the 3,5-dinitrobenzoate anion forms double hydrogen bonds of type N—H...O, resulting in a fork-like interaction with the protonated diaminopyrimidine rings [graph-set notation R22(8)]. This motif self-assembles through a DDAA array of quadruple hydrogen bonds. The crystal structure is also stabilized by C—H...O hydrogen bonds. [ABSTRACT FROM AUTHOR]

In the crystal structures of the title compounds, C6H10N3O2+·C7H5O3−·H2O, (I), C6H10N3O2+·C7H4NO4−·H2O, (II), and C6H10N3O2+·C4H5O6−·C6H9N3O2, (III), the 2-amino-4,6-di­meth­oxy­pyrimidinium cation [abbreviated as (MeO)2-Hampy+] inter­acts with the carboxyl­ate group of the corresponding anion through a pair of nearly parallel N—H⋯O hydrogen bonds to form R22(8) ring motifs. In (I), the (MeO)2-Hampy+ cation is centrosymmetrically paired through a pair of N—H⋯N hydrogen bonds involving the 2-amino group and a ring N atom forming an R22(8) motif. In (II), inversion-related R22(8) motifs (amino–pyrimidine–carboxyl­ate motifs) are further bridged by N—H⋯O hydrogen bonds on either side forming a DDAA array of quadruple hydrogen bonds. This array is extended further on either side by Owater—H⋯Ometh­oxy hydrogen bonds, resulting in an array of six hydrogen bonds ( ADDAAD). The water mol­ecule plays a pivotal role, and five hydrogen-bonded fused rings are formed around the water mol­ecule. In (III), the carb­oxy group of the tartrate anion inter­acts with the ring N atom and 2-amino group of the neutral (MeO)2-ampy mol­ecule through N—H⋯O and O—H⋯N hydrogen bonds. There is also an intra­molecular O—H⋯O hydrogen bond in the tartrate anion. In all three crystal structures, C—H⋯O hydrogen bonds are observed. [ABSTRACT FROM AUTHOR]

In the crystal structure of the title compound, C6H10N3+·C7H5O3-, the asymmetric unit contains four crystallographically independent 2-amino-4,6-dimethylpyrimidinium and salicylate ions (Z = 8). In each of these, one of the pyrimidine N atoms is protonated, and the carboxylate group of the salicylate ion interacts with the pyrimidine group through a pair of N—H…O hydrogen bonds, forming an R2²(8) motif. The pyrimidine cations also form base pairs via a pair of N—H…N hydrogen bonds (involving the amino group and the unprotonated ring N atom), forming another R2²(8) motif. Three such R2²(8) motifs, fused together, constitute a closed cyclic aggregate, and the linking of these aggregates, arranged in consecutive layers, can be analysed in terms of off-face stacking interactions. [ABSTRACT FROM AUTHOR]

In the title compounds, namely 2,4-diamino-5-[(3,4,5-trimethoxy­phenyl)methyl]­pyrimidin-1-ium pyridine-2-carboxyl­ate, C14H19N4O3+·C6H4NO2−, (I), and 2-amino-4,6-dimethyl­pyrimidin-1-ium pyridine-2-carboxyl­ate hemihydrate, C6H10N3+·C6H4NO2−·0.5H2O, (II), the trimethoprim and 2-amino-4,6-dimethyl­pyrimidin-1-ium cations are protonated at one of the pyrimidine N atoms. In (I), bifurcated hydrogen bonds are observed between a picolinate O atom, the protonated N atom and the 2-amino group; the graph-set designator is R21(6). The pyrimidine moieties of the trimethoprim cations are centrosymmetrically paired through a pair of N—H⋯N hydrogen bonds. In addition to the base pairing, one of the picolinate O atoms bridges the 2- and 4-amino groups on either side of the paired bases, resulting in a complementary DADA array. In (II), the carboxyl­ate group of the picolinate anion binds with the protonated pyrimidine N atom and the 2-amino group of the pyrimidine moiety through a pair of N—H⋯O hydrogen bonds, leading to the common ring motif R22(8). The water mol­ecule, which resides on a twofold rotation axis, bridges the carboxyl­ate group of the picolinate anion via O—H⋯O hydrogen bonds. [ABSTRACT FROM AUTHOR]

In the title compound [systematic name: 2,4-diamino-5-(3,4,5-trimethoxy­benz­yl)pyrimidinium tetrafluoroborate], C14H19N4O3+·BF4−, the trimethoprim (TMP) mol­ecule is protonated at one of the pyrimidine N atoms. The protonated N atom and 2-amine group of the TMP cation inter­act with the tetrafluoroborate anion through a pair of N—H⋯F hydrogen bonds [graph set R22(8)]. The inversion-related TMP cations are linked through a pair of N—H⋯N hydrogen bonds. The 2-amine group of one TMP cation and the 4-amine group of another cation are bridged by a meth­oxy O atom, via N—H⋯O hydrogen bonds. [ABSTRACT FROM AUTHOR]

In the title cocrystal, C6H9N3O2·C7H7NO2, the 2-amino-4,6-dimethoxy­pyrimidine mol­ecule inter­acts with the carboxyl group of the 4-amino­benzoic acid mol­ecule through N—H⋯O and O—H⋯N hydrogen bonds, forming a cyclic hydrogen-bonded motif [ R22(8)]. This motif further self-organizes through N—H⋯O hydrogen bonds to generate an array of six hydrogen bonds with the rings having the graph-set notation R23(6), R22(8), R42(8), R22(8) and R23(6). The 4-amino­benzoic acid mol­ecules self-assemble via N—H⋯O hydrogen bonds to form a supra­molecular chain along the c axis. [ABSTRACT FROM AUTHOR]