title: Hydrogen-bonding patterns in trimethoprim picolinate and 2-amino-4,6-dimethylpyrimidinium picolinate hemihydrate.
abstract: 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 R2(1)(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 R2(2)(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.
authors.affiliation: School of Chemistry, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu, India.
authors.forename: Madhukar
authors.initials: M
authors.lastname: Hemamalini
authors.forename: Packianathan Thomas
authors.initials: PT
authors.lastname: Muthiah
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Lynch
mesh_terms: D003461:Crystallography; D006860:Hydrogen Bonding; D008958:Models, Molecular; D015394:Molecular Structure; D010848:Picolinic Acids / Q000737:chemistry*; D011743:Pyrimidines / Q000737:chemistry*; D014295:Trimethoprim / Q000031:analogs & derivatives* / Q000737:chemistry
chemical_list: C464526:2-amino-4,6-dimethyl pyrimidine; D010848:Picolinic Acids; D011743:Pyrimidines; C515581:trimethoprim picolinate; D014295:Trimethoprim