title: Five pseudopolymorphs of 6-amino-2-thiouracil: absence of N-H...S hydrogen bonds.
abstract: In order to study the preferred hydrogen-bonding pattern of 6-amino-2-thiouracil, C(4)H(5)N(3)OS, (I), crystallization experiments yielded five different pseudopolymorphs of (I), namely the dimethylformamide disolvate, C(4)H(5)N(3)OS·2C(3)H(7)NO, (Ia), the dimethylacetamide monosolvate, C(4)H(5)N(3)OS·C(4)H(9)NO, (Ib), the dimethylacetamide sesquisolvate, C(4)H(5)N(3)OS·1.5C(4)H(9)NO, (Ic), and two different 1-methylpyrrolidin-2-one sesquisolvates, C(4)H(5)N(3)OS·1.5C(5)H(9)NO, (Id) and (Ie). All structures contain R(2)(1)(6) N-H...O hydrogen-bond motifs. In the latter four structures, additional R(2)(2)(8) N-H...O hydrogen-bond motifs are present stabilizing homodimers of (I). No type of hydrogen bond other than N-H...O is observed. According to a search of the Cambridge Structural Database, most 2-thiouracil derivatives form homodimers stabilized by an R(2)(2)(8) hydrogen-bonding pattern, with (i) only N-H...O, (ii) only N-H...S or (iii) alternating pairs of N-H...O and N-H...S hydrogen bonds.
authors.affiliation: Institut für Organische Chemie und Chemische Biologie, Goethe-Universität Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt am Main, Germany.
authors.forename: Wilhelm Maximilian
authors.initials: WM
authors.lastname: Hützler
authors.forename: Michael
authors.initials: M
authors.lastname: Bolte
mesh_terms: D003460:Crystallization; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D015394:Molecular Structure; D013889:Thiouracil / Q000031:analogs & derivatives* / Q000737:chemistry
chemical_list: C579180:6-amino-2-thiouracil; D013889:Thiouracil