{1,5,9-Tris[(2S)-2-hydroxypropyl]-1,5,9-triazacyclododecane}zinc(II) dinitrate monohydrate

In the title compound, [Zn(C18H39N3O3)](NO3)2·H2O, the coordination geometry around the central ZnII atom is distorted octahedral. The hydroxyl groups in the macrocyclic ligand and water molecules are engaged in O—H⋯O hydrogen bonding, which forms two-dimensional corrugated sheets comprising 34-membered rings. Neighbouring sheets are connected by C—H⋯O interactions.

In the title compound, [Zn(C 18 H 39 N 3 O 3 )](NO 3 ) 2 ÁH 2 O, the coordination geometry around the central Zn II atom is distorted octahedral. The hydroxyl groups in the macrocyclic ligand and water molecules are engaged in O-HÁ Á ÁO hydrogen bonding, which forms two-dimensional corrugated sheets comprising 34-membered rings. Neighbouring sheets are connected by C-HÁ Á ÁO interactions.
ties with metal ions. The addition of different pendant arms can enhance the selectivity of the azamacrocycle for a metal cation, depending on the cavity size and on the nature of the substitutents (Skerlj et al., 2002). The design and synthesis of polyazamacrocycles bearing flexible pendant arms from the cyclic framework provides chemists with an opportunity to design macrocycles tailored for a specific function. This is especially the case because the pendant arms provide additional coordination sites for metal ions.
Functionalised macrocycles have been successfully employed in the synthesis of metal-chelating agents for medical applications owing to the kinetic inertness of the complexes which makes them resistant to decomplexation (Sheng et al., 2007).
In the title compound ( Fig. 1), the Zn II atom is octahedrally coordinated. Small distortions cause the N-Zn-N angles to exceed 90° while the O-Zn-O angles measure less than 90°. The dicationic complex exhibits near C 3 -symmetry with exception of the propylene groups in which the central CH 2 group adopts a different conformation in each sector.
The three hydroxyl groups are all engaged in hydrogen bonds. The O1-H1 and O3-H3 groups form hydrogen bonds (Table 1) with the two asymmetric nitrate counter anions and the O2-H2 group with the water molecule. This water molecule itself forms two hydrogen bonds with two other complexes. The hydrogen bonding results in the formation of two-dimensional corrugated sheets parallel to the ac plane. Three adjacent complex units are linked to form 34-membered rings which include ten hydrogen bonds (Fig. 2). Neighbouring sheets are loosely connected by C-H···O interactions involving one of the CH 2 groups of the triazacyclododecane.
The configuration at C11, C14 and C17 is (S), resulting from utilisation of enantiopure (S)-methyloxirane in the synthetic process which is supported by anomalous scattering.
One equivalent of Zn(NO 3 ) 2 .6H 2 O was dissolved in ethanol at 333 K with stirring. The ligand was added to the solution and it was stirred overnight. The powder which formed was filtered off and dissolved in a small quantity of N,N-dimethylformamide whereupon diethyl ether vapour was slowly diffused into the solution in a sealed container. Single crystals were obtained the next day.
supplementary materials sup-2 Refinement Alkyl H atoms were positioned geometrically (C-H = 1.00, 0.99 and 0.98 Å for CH, CH 2 and CH 3 groups, respectively) and allowed to ride on their parent atoms. Hydroxyl and water O-H distances were restrained to 0.85 (1) Å and additional restraint H4···H5 distance restraint of 1.37 (1) Å was applied to the water molecule. U iso (H) values were set at 1.2 times U eq (C,O) except for methyl groups where U iso (H) was set at 1.5 times U eq (C). Fig. 1. The asymmetric unit of the title compound. Displacement ellipsoids are drawn at the 50% probability level.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
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 Rfactors(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq