title: Hydrogen bonding patterns in salts of derivatives of aminopyrimidine and thiobarbituric acid.
abstract: 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.
authors.affiliation: Department of Chemistry, Periyar Maniammai University, Thanjavur 613 403, Tamil Nadu, India.
authors.forename: Sundaramoorthy
authors.initials: S
authors.lastname: Gomathi
authors.affiliation: School of Chemistry, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu, India.
authors.forename: Jeyaraman Selvaraj
authors.initials: JS
authors.lastname: Nirmalram
authors.affiliation: School of Chemistry, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu, India.
authors.forename: Packianathan Thomas
authors.initials: PT
authors.lastname: Muthiah
mesh_terms: D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D008958:Models, Molecular; D011743:Pyrimidines / Q000737:chemistry*; D012492:Salts / Q000737:chemistry*; D013858:Thiobarbiturates / Q000737:chemistry*
chemical_list: D011743:Pyrimidines; D012492:Salts; D013858:Thiobarbiturates; C012180:2-aminopyrimidine; C029684:thiobarbituric acid
keywords: base pairs in macromolecules; hydrogen bonding; supramolecular interactions