5,7,7,12,14,14-Hexamethyl-4,8-diaza-1,11-diazoniocyclotetradeca-4,11-diene diiodide dihydrate

The asymmetric unit of the title compound, C16H34N4 2+·2I−·2H2O, contains one half-cation, one iodide anion and one water molecule. The cation has crystallographically imposed centrosymmetric symmetry. Despite some differences in the unit-cell dimensions, packing analysis on a cluster of 15 cations and a comparison of the hydrogen bonding suggests that this compound is isostructural with its bromide analogue. Intermolecular hydrogen bonding forms eight-membered [H—O—H⋯I]2 and [H—N—H⋯I]2 rings and creates a sheet structure.

The asymmetric unit of the title compound, C 16 H 34 N 4 2+ Á-2I À Á2H 2 O, contains one half-cation, one iodide anion and one water molecule. The cation has crystallographically imposed centrosymmetric symmetry. Despite some differences in the unit-cell dimensions, packing analysis on a cluster of 15 cations and a comparison of the hydrogen bonding suggests that this compound is isostructural with its bromide analogue. Intermolecular hydrogen bonding forms eight-membered [H-O-HÁ Á ÁI] 2 and [H-N-HÁ Á ÁI] 2 rings and creates a sheet structure.
The macrocyclic dication has crystallographically imposed centrosymetric symmetry, Z' = 1/2, with protonation at the amine N-atoms rather than at the imine groups (Fig. 1). The unit-cell parameters are somewhat similar to those of the bromide analogue (Rohovec et al., 1999) measured at room temperature. However, there is a difference in that the most acute angle subtends the longest and shortest cell axes in I, but subtends the shortest and middle length cell axes in the iodide salt. To check if this was a structurally significant variation the "crystal packing similarity" module of Mercury CSD 2.3 was used (Macrae et al., 2008). This analysis of the largest molecular component in the array (here the macrocyclic cation) showed that a molecular cluster of fifteen cations from each salt matched to within distance and torsion angle variations of 20%. Thus the two structures are isostructural, see overlay in Fig. 2.
Classical intramolecular N-H···N hydrogen-bonding joins the amine and imine N-atoms across the macrocycle. There are also four independent intermolecular hydrogen-bonds. All involve iodide as the acceptor with both water H-atoms acting as donors and atom H2N acting as a donor in two seperate interactions, see and [H-N-H···I] 2 rings support a two dimensional sheet structure propagated largely through N-H···I interactions. This is again similar to the bromide structure and so their isostructural nature is confirmed.

Experimental
A 0.2 mol (13.2 mL) sample of ethylenediamine (ED) was put into 10 ml absolute ethanol and cooled in an ice bath for about 10 minutes. A 0.2 mol (36.2 ml of 55%) sample of hydroiodic acid was slowly added to the cool ED solution. Care was taken not to let the solution to boil over. After the addition of HI, 30 mL of acetone was added (an excess of 0.4 mL was required) and the solution allowed to cool in an ice bath overnight. The colourless crystalline material was filtered from solution. It was washed in absolute EtOH and dried in air for 30 minutes (yield 6.221 g).

Refinement
The position of the nitrogen-bound H atoms were refined freely, but the positions of the water H atoms were restrained such that O-H and H···H distances approximated 0.88Å and 1.33Å respectively with U iso (H) set to 1.5 U eq (O). All other supplementary materials sup-2 H atoms were placed in calculated positions and refined in riding modes with C-H = 0.98Å or 0.99Å for the CH 3 and CH 2 groups respectively. The U iso (H) values were set to 1.5 or 1.2 times U eq of their parent C atoms for the CH 3 and CH 2 groups respectively. Fig. 1. The molecular structure of the macrocyclic dication with atom numbering scheme. Displacement ellipsoids are drawn at 50% probability level H atoms are presented as a small sphertes of arbitrary radius. Symmetry code: (i) 1-x, 1-y, -z.

Special details
Experimental. Southampton NCS collection 2010src0073 Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The 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 > σ(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.