Indole-3-thiouronium iodide

In the title compound, C9H10N3S+·I−, the indole ring system and the thiouronium group are essentially perpendicular, with a dihedral angle of 89.87 (8)°. By intermolecular hydrogen bonding, a three-dimensional network is formed, which is additionally supported by intermolecular C—H⋯π interactions.

In the title compound, C 9 H 10 N 3 S + ÁI À , the indole ring system and the thiouronium group are essentially perpendicular, with a dihedral angle of 89.87 (8) . By intermolecular hydrogen bonding, a three-dimensional network is formed, which is additionally supported by intermolecular C-HÁ Á Á interactions.

Structure Reports Online
As in the nitrate salt, the cation consists of two planar subunits, i.e. the indole and the thiouronium moieties, which are perpendicular to each other with an angle of 89.87 (8)° between the corresponding least squares planes. The weighted R value of a thermal motion analysis using the program THMA11 (Schomaker & Trueblood, 1998) results in a low weighted R value of 0.106, which is slightly higher than in the nitrate salt (0.084).
The iodide anion is surrounded by five N-H groups which act as hydrogen bond donors (Fig. 2). This results in a three dimensional hydrogen bonded network. The H···I distances of 2.76 (3) to 2.97 (2) Å are in the same range as found for other N-H···I hydrogen bonds in the Cambridge Structural Database (update August 2007; Allen, 2002), where we calculate an average H···I distance of 2.80 Å. In general, N-H···I hydrogen bonds are relatively weak; the average hydrogen bonded intermolecular N···I distance is 3.65 Å in the Cambridge Structural Database, which is not shorter than the sum of van der Waals radii of 1.55 (nitrogen) plus 1.98 Å (iodine).
In addition to the N-H···I hydrogen bonds there are weak intermolecular C-H···π interactions between H1 and the six-membered ring of the indole moiety (Fig. 3). The distance of H1 to the least squares plane of the six-membered ring is 2.83 (2) Å and the distance to the center of gravity of this ring is 2.91 (2) Å (Table 2). According to the classification of Malone et al. (1997) this is a "Type I" C-H···π interaction.

Experimental
Indole-3-thiouronium iodide was prepared as described in literature (Harris, 1969;van der Geer et al., 2007) and crystallized by diethyl ether vapor diffusion into an acetone solution.

Refinement
All H atoms were freely refined.
supplementary materials sup-2 Figures   Fig. 1. : The molecular structure of (I). Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii.  Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.