Received 6 June 2005
The title compound, (C3H12N2)[HAsO4]·H2O, contains a network of propane-1,3-diaminium cations, hydrogenarsenate anions [mean As-O = 1.687 (2) Å] and water molecules. The crystal packing involves anion-to-anion and water-to-anion O-HO hydrogen bonds, resulting in infinite chains containing the unusual R33(10) graph-set motif. Cation-to-anion and cation-to-water N-HO hydrogen bonds generate a three-dimensional overall structure.
The title compound, (C3H12N2)[HAsO4]·H2O, (I) (Fig. 1), was prepared as part of our ongoing structural studies of hydrogen-bonding interactions in protonated-amine (di)hydrogen arsenates (Lee & Harrison, 2003a; Wilkinson & Harrison, 2004; Todd & Harrison, 2005). In particular, (I) complements propane-1,3-diaminium bis(dihydrogenarsenate), (C3H12N2)[H2AsO4]2 (Wilkinson & Harrison, 2005), prepared under different pH conditions.
The [HAsO4]2- hydrogenarsenate group in (I) has normal tetrahedral geometry [mean As-O = 1.687 (2) Å], with the protonated As1-O4 vertex showing its usual lengthening relative to the unprotonated As-O bonds (Table 1). The propane-1,3-diaminium cation shows no unusual geometrical features.
As well as electrostatic attractions, the component species in (I) interact by means of a network of O-HO and N-HO hydrogen bonds (Table 2). The [HAsO4]2- units and water molecules are linked into polymeric chains (Fig. 2) propagating along  by way of anion-to-anion O4-H1O2i and water-to-anion O5-H14O1 and O5-H15O2ii bonds (Table 2). This arrangement results in an unusual R33(10) graph-set (Bernstein et al., 1995) motif. The As1As1i separation is 4.7991 (3) Å.
The organic species interacts with the hydrogenarsenate/water chains by way of six N-HO hydrogen bonds [mean HO = 1.89 Å, mean N-HO = 171° and mean NO = 2.793 (2) Å]. One of the acceptor O atoms is part of a water molecule, and the other five are parts of hydrogenarsenate groups. This hydrogen-bonding scheme results in a three-dimensional network (Fig. 3).
The hydrogen-bonded hydrogenarsenate/water chains in (I) are different from the motifs seen in related structures. In bis(cycloheptylaminium) hydrogenarsenate monohydrate (Todd & Harrison, 2005) and bis(benzylammonium) hydrogenarsenate monohydrate (Lee & Harrison, 2003c), hydrogen-bonded dimers of [HAsO4]2- units occur, with the dimers bridged into double chains by intervening water molecules. In the unhydrated piperidinium dihydrogenarsenate (Lee & Harrison, 2003b) and t-butylammonium dihydrogenarsenate (Wilkinson & Harrison, 2004), single chains of [H2AsO4]- anions occur with each adjacent dihydrogenarsenate pair linked by a pair of hydrogen bonds. In propane-1,3-diaminium bis(dihydrogenarsenate) (Wilkinson & Harrison, 2005), the same organic cation as found in (I) is combined with dihydrogenarsenate [H2AsO4]- groups, with the latter forming double chains.
| || Figure 1 |
A view of (I) with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. Hydrogen bonds are indicated by dashed lines.
| || Figure 2 |
Detail of a hydrogen-bonded (dashed lines) hydrogenarsenate/water chain in (I).
| || Figure 3 |
The crystal packing of (I). Dashed lines indicate hydrogen bonds.
0.5 M aqueous propane-1,3-diamine solution (10 ml) was added to 0.5 M aqueous H3AsO4 solution (10 ml) to result in a clear solution. Aqueous ammonia was added to this solution to raise the pH to about 12, which is beyond the second end-point for H3AsO4 (i.e. the predominant species is [HAsO4]2-). Platy crystals of (I) grew as the water evaporated over the course of a few days.
The O-bound H atoms were found in difference maps and refined as riding on their carrier O atoms in their as-found relative positions. H atoms bonded to C and N atoms were placed in idealized positions (C-H = 0.99 Å and N-H = 0.91 Å) and refined as riding, allowing for free rotation of the -NH3 groups. The constraint Uiso(H) = 1.2Ueq(carrier) was applied in all cases.
Data collection: COLLECT (Nonius, 1998); cell refinement: SCALEPACK (Otwinowski & Minor, 1997); data reduction: SCALEPACK, DENZO (Otwinowski & Minor, 1997) and SORTAV (Blessing, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXL97.
We thank the EPSRC National Crystallography Service (University of Southampton, England) for the data collection.
Bernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem. Int. Ed. Engl. 34, 1555-1573.
Blessing, R. H. (1995). Acta Cryst. A51, 33-37.
Bruker (1999). SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.
Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565.
Lee, C. & Harrison, W. T. A. (2003a). Acta Cryst. E59, m739-m741.
Lee, C. & Harrison, W. T. A. (2003b). Acta Cryst. E59, m959-m960.
Lee, C. & Harrison, W. T. A. (2003c). Acta Cryst. E59, m1151-m1153.
Nonius (1998). COLLECT. Nonius BV, Delft, The Netherlands.
Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307-326. New York: Academic Press.
Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.
Todd, M. J. & Harrison, W. T. A. (2005). Acta Cryst. E61, m1024-m1026.
Wilkinson, H. S. & Harrison, W. T. A. (2004). Acta Cryst. E60, m1359-m1361.
Wilkinson, H. S. & Harrison, W. T. A. (2005). Acta Cryst. E61, m1289-m1291.