Cyclopropylammonium 4-iodobenzoate

In the title molecular salt, C3H8N+·C7H4IO2 −, the cyclopropanaminium cation forms three hydrogen bonds to the 4-iodobenzoate anion, forming two unique repeating R 4 4(12) hydrogen-bonding rings that result in one-dimensional hydrogen-bonded columns along the crystallographic c axis.

In the title molecular salt, C 3 H 8 N + ÁC 7 H 4 IO 2 À , the cyclopropanaminium cation forms three hydrogen bonds to the 4iodobenzoate anion, forming two unique repeating R 4 4 (12) hydrogen-bonding rings that result in one-dimensional hydrogen-bonded columns along the crystallographic c axis.

Experimental
Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT-Plus (Bruker, 2004); data reduction: SAINT-Plus and XPREP (Bruker 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and DIAMOND (Brandenburg, 1999); software used to prepare material for publication: WinGX (Farrugia, 1999) and PLATON (Spek, 2009 Ammonium carboxylate salts are molecular salts formed by mixing a primary amine and a carboxylic acid containing molecule, thus resulting in proton transfer from the acid to the amine (Kinbara et al., 1996). This forms a primary ammonium cation and a carboxylate anion. The three H atoms on the cation can then form three charge-assisted hydrogen bonds to the two O atoms on the anion. In the literature, three kinds of hydrogen bonded rings are most commonly formed by these hydrogen bonds, described using graph-set notation (Bernstein et al., 1995): R 2 4 (8), R 3 4 (10) and R 4 4 (12) (Lemmerer, 2011).
In molecular salt (I), shown in Fig. 1, formed by dissolving cyclopropylamine and p-iodobenzoic acid in methanol, only a R 4 4 (12) ring is formed. However, two such rings are formed, one by using the N1-H1A···O1 and N1-H1B···O1 hydrogen bonds, and the second one by using the N1-H1B···O1 and N1-H1C···O2 hydrogen bonds. As the N1-H1B···O1 hydrogen bond is common to both rings, a repetition of the two types of rings results, forming a 1-D hydrogen bonded column along the c axis (Fig. 2).

Experimental
All chemicals were purchased from commercial sources and used as received. (I) was prepared by slowly evaporating a solution of cyclopropylamine (0.050 g, 0.88 mmol) and p-iodobenzoic acid (0.217 g, 0.886 mmol) dissolved in 5 ml methanol.

Refinement
All C-H atoms were refined using a riding model, with a distance of 0.95 Å (Ar-H), 0.99 Å, (CH 2 ) and 1.00 Å, (CH) and U iso (H) = 1.2U eq (C). N-H atoms on the ammonium group were located in the difference Fourier map and their coordinates and isotropic displacement parameters were refined freely.

Figure 2
The hydrogen bonding pattern of the title compound. H atoms not involved in hydrogen bonding are omitted for clarity.

Special details
Experimental. Numerical integration absorption corrections based on indexed crystal faces were applied using the XPREP routine (Bruker, 2004) Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.