2-[(E)-(6-Amino-1,3-dimethyl-2,4-dioxo-1,2,3,4-tetrahydropyrimidin-5-yl)iminomethyl]pyridinium bromide

The title compound, C12H14N5O2 +·Br−, is the hydrobromide salt of a Schiff base in which protonation has taken place at the pyridine N atom. This organic cation is essentially planar (r.m.s. of all fitted non-H atoms = 0.0448 Å). In the crystal, N—H⋯Br hydrogen bonds as well as C—H⋯O and C–H⋯Br interactions connect the molecules, forming a three-dimensional network.

The title compound, C 12 H 14 N 5 O 2 + ÁBr À , is the hydrobromide salt of a Schiff base in which protonation has taken place at the pyridine N atom. This organic cation is essentially planar (r.m.s. of all fitted non-H atoms = 0.0448 Å ). In the crystal, N-HÁ Á ÁBr hydrogen bonds as well as C-HÁ Á ÁO and C-HÁ Á ÁBr interactions connect the molecules, forming a threedimensional network.

Comment
Next to cardiovascular diseases, cancer has become one of the main fatal diseases in industrialized countries. Apart from classical surgery, chemo-and radiotherapeutic treatments have entered the arsenal of possible cures for certain types of cancer. All methods, however, suffer from their own set of problematic side-effects and, as a consequence, the development of radiopharmaceuticals -combining the advantages of chemotherapy as well as radiation methods while at the same time avoiding their unique respective undesired side-effects -has been a topic of research (Gerber et al., 2011). Tailoring and fine-tuning of the envisioned radiopharmaceuticals' properties such as lipophilicity and, in particular, inertness is of paramount importance with respect to possible future in vivo applications in contemporary medicine and requires sound knowledge about structural parameters of the ligands applied if a more heuristic approach in the synthesis is to triumph over pure trial-and-error as it is encountered in this specific field of coordination chemistry up to the present day. To allow for an assessment of changes in structural features upon coordination, the molecular and crystal structure of the title compound has been determined. The crystal structure of the neutral compound (Booysen et al., 2011a), and other 6-amino-1,3-dimethyl-2,4(1H,3H)-dione-derived Schiff-base ligands (Booysen et al., 2011b,c), have been described previously.
The molecular structure of the title molecule is illustrated in Fig. 1 In the crystal, N-H···Br hydrogen bonds as well as C-H···O and C-H···Br contacts are observed (Table 1). While the hydrogen bonds are formed between the nitrogen-bonded hydrogen atoms and the bromide anion exclusively, the C-H···O contacts involve the hydrogen atoms of the pyridine moiety and one of the nitrogen-bonded methyl groups as donors and both oxygen atoms as acceptors. The C-H···Br contact is supported by one of the hydrogen atoms of the second nitrogen-bonded methyl group. In terms of graph-set analysis (Etter et al., 1990;Bernstein et al., 1995), the descriptor for the classical hydrogen bonds is DDD on the unitary level, whereas the C-H···O contacts necessitate a C(5)C(8)C(11) on the same level.
In total, these contact result in the formation of a three-dimensional network (Fig. 3).
supplementary materials sup-2 Refinement Carbon-bound H atoms were placed in calculated positions (C-H 0.95 Å) and were included in the refinement in the riding model approximation, with U(H) set to 1.2U eq (C). The H atoms of the methyl groups were allowed to rotate with a fixed angle around the C-C bond to best fit the experimental electron density (HFIX 137 in the SHELX program suite (Sheldrick, 2008)), with U(H) set to 1.5U eq (C). All nitrogen-bound H atoms were located on a difference Fourier map and refined freely.