Poly[hemi(hexaaquazinc) [[μ2-1,3-bis(1,2,4-triazol-1-yl)methane](μ2-5-sulfonatobenzene-1,3-dicarboxylato)zinc] sesquihydrate]

The title coordination polymer, {[Zn(H2O)6]0.5[Zn(C8H3O7S)(C5H6N6)]·1.5H2O}n, synthesized under hydrothermal conditions, possesses a one-dimensional tube-like chain structure along [100], with octahedral [Zn(H2O)6]2+ groups ( symmetry) trapped in the pores. The other Zn atom is five-coordinated in a highly distorted trigonal–biyramidal coordination that is defined by two different N atoms from two 1,3-bis(1,2,4-triazol-1-yl)methane (btrm) ligands and three carboxylate O atoms from 5-sulfonatobenzene-1,3-dicarboxylate ligands. The chains carry negative charges, whereas the free [Zn(H2O)6]2+ cations are positively charged. The [Zn(H2O)6]2+ cation is connected with the one-dimensional tubelike chain through weak classical O—H⋯O and O—H⋯N hydrogen-bonding interactions as well as through electrostatic interactions. One of the two uncoordinated water molecules exhibits half-occupancy.


Comment
Organic-inorganic hybrid materials have obtained extensive attention due to not only the structural diversity but also their attractive properties, such as catalytic activity, magnetism, photochemical activity and electrical chemistry (Ishikava et al., 2003). One of the key steps for preparation of polymeric transition metal complexes is to select the multidentate bridging ligands or mixed multidentate ligands (Biradha et al., 2006). 5-Sulfoisophthalic acid as a kind of multi-carboxylic ligand is a good bridging ligand, but it has been less explored for the synthesis. On the other hand, 1,4-bis(1,2,4-triazol-1-yl)methane The title compound possesses a dinuclear structure with the asymmetric unit containing one crystallographically unique Zn 2+ ion, one btrm ligand, one sip ligand and half of one free Zn(H 2 O) 6 2+ ion. As viewed in Fig. 1, Zn1 is five-coordinated in a highly distorted trigonal biyramid coordination sphere that is defined by two different nitrogen atoms from two btrm ligands and three carboxylic oxygen atoms. Both btrm and sip adopt two connected mode. Every sip ligand links two Zn(II) atoms to construct a one-dimensional chain, two such chains are bridged by cis-btrm ligands to produce a one-dimensional tubelike chain (Fig. 2)

Refinement
After the non-hydrogen atoms of the cation and anion had been located, a number of peaks remained in the difference electron density. We have assigned these as water of solvation, O11 and O12. As a result of the large Ueq on O12 this atom was assigned an occupation number of 0.5 which is consistent with the C, H and N elemental analyses. It was not possible to locate the hydrogen atoms around O12, but those around O11 were located from difference Fourier maps and further supplementary materials sup-2 refined by using geometrical restraints. Several small, but significant, peaks of around 1.5 e/A 3 remain in the neighborhood of the the cation.
H atoms were positioned geometrically with O-H = 0.86 Å, C-H = 0.93 and 0.97 Å for aromatic and methylene H atoms, respectivly, and constrained to ride on their parent atoms, and included in the final cycles of refinement using a riding model, with U iso (H) = 1.2Ueq(C).
Figures Fig. 1. The coordination environments of Zn1 in the title compound.

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.