4,7-Phenanthrolinium perchlorate–5-methyl-1,2,4-triazolo[1,5-a]pyrimidin-7(4H)-one–water (1/1/2)

The asymmetric unit of the title compound, C12H9N2 +·ClO4 −·C6H6N4O·2H2O, contains a monoprotonated 4,7-phenanthrolinium (47phen) cation, a perchlorate anion balancing its charge, a neutral molecule of 5-methyl-1,2,4-triazolo[1,5-a]pyrimidin-7(4H)-one (HmtpO) and two interstitial water molecules. In the crystal structure, the acidic H atoms of 47phenH+ and HmtpO form strong hydrogen bonds with the water molecules, which in turn act as hydrogen-bond donors, forming links between them and towards the carbonyl O atom of HmtpO, the non-protonated N atom of 47phen+ and one of the O atoms of the anion.

The asymmetric unit of the title compound, C 12 H 9 N 2 + ÁClO 4 À Á-C 6 H 6 N 4 OÁ2H 2 O, contains a monoprotonated 4,7-phenanthrolinium (47phen) cation, a perchlorate anion balancing its charge, a neutral molecule of 5-methyl-1,2,4-triazolo[1,5-a]pyrimidin-7(4H)-one (HmtpO) and two interstitial water molecules. In the crystal structure, the acidic H atoms of 47phenH + and HmtpO form strong hydrogen bonds with the water molecules, which in turn act as hydrogen-bond donors, forming links between them and towards the carbonyl O atom of HmtpO, the non-protonated N atom of 47phen + and one of the O atoms of the anion.

Comment
The title compound was obtained as a by-product when trying to synthesize a copper complex containing both heterocycles, as indicated in the preparation section. The formula of the compound is (47phenH)(HmtpO)(ClO 4 ).2H 2 O (47phen = 4,7phenanthroline and HmtpO = 5-methyl-1,2,4-triazolo[1,5-a]pyrimidine-7(4H)-one), which also correspond to the contents of the asymmetric unit which is shown in Figure 1. The geometrical parameters of both heterocycles do not significantly differ from other compounds with protonated 47phen (Shang et al., 2006, Gillard et al., 1998 or neutral HmtpO (Navarro et al., 1997, Salas et al. 1996. The species are linked in the crystal mainly by hydrogen bonds, water molecules being the main actors of the H-bond network. One of the independent water molecules (O1W) accepts an H-bond from the extra proton of 47phen (N4P-H) and donates towards the carbonyl O-atom (O7) of the triazolopyrimidine moiety and towards the other water molecule (O2W). The later also accepts an H-bond from the acidic H-atom of HmtpO (N4-H) acting as donor for the perchlorate anion and for the non-protonated N atom of 47phen (N7P). This builds a two-dimensional hydrogen bond network, which includes, among other motifs, centrosymmetric (HmtpO) 2 (H 2 O) 4 boxes, with both HmtpO molecules stacked with a separation of 3.4 Å and linked by two chains with two water molecules each, starting at N4P of one of the heterocycles and ending at O7 of the other: N4P-H···O1W-H···O2W-H···O7.

Experimental
The compound was fortuitously obtained as a by-product when trying to synthesize a ternary complex of Cu(II) with 5methyl-1,2,4-triazolo[1,5-a]pyrimidine-7(4H)-one (HmtpO) and 4,7-phenanthroline (47phen). An aqueous solution (10 ml.) of Cu(ClO 4 ) 2 .6H 2 O (0,75 g, 2 mmol), another aqueous solution (20 ml.) of HmtpO (0,61 g, 4 mmol) and a ethanolic solution (10 ml.) of 47phen (0,73 g, 4 mmol) were mixed and the mixture was refluxed for 2 h, a green precipitate (a Cu-Hmtpo complex) appearing which was filtered off. The mother liquor was left to stand at room temperature for two weeks, when a mixture of green and pale yellow crystals was obtained, which was filtered off. It was possible to separate both types of crystals under a lens, the green crystals turning out to be a Cu-phen complex whereas the pale yellow ones are the title compound, the structure of which is presented in this article. Elemental analysis data for C 18 H 19 ClN 6 O 7 . % Found (Calc.): C 46.17 (46.31), H 4.52 (4.10), N 17.79 (18.00).

Refinement
Hydrogen atoms of the organic moieties were idealized with distances to their parent atoms of 0.93 (C) or 0.86 (N) Å, the location of acidic (N-H) H atoms being obvious from previous ΔF maps. Free rotation was allowed for the methyl group. Water hydrogen atoms were easily located in ΔF maps and refined with restrained O-H distances (0.82 (1) Å).
Displacement parameters of all H atoms were fixed at 1.2 times the U eq of their parent atoms.