Ethane-1,2-diaminium 2,2′-[terephthaloylbis(azanediyl)]diacetate tetrahydrate

In the title salt hydrate, C2H10N2 2+·C12H10N2O6 2−·4H2O, each of the ions is located about a centre of inversion and the asymmetric unit is completed by two water molecules in general positons. In the crystal, the cations, anions and water molecules are connected by O—H⋯O and N—H⋯O hydrogen bonding into a three-dimensional network.

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: NC2319).

Comment
Recently, the interest in constructing metal-organic coordination polymers continuously rises due to their facinating structures and properties with potential application as functional materials. For the synthesis of such compounds frequently relatively rigid ligands with several coordination centers are used. In this context the title compound was prepared, which should be used as a precursor in the synthesis of new coordination polymers.
The crystal structure of the title compound consists of 2,2′-(terephthaloylbis(azanediyl))diacetate anions that are located on centers of inversion as well as of ethylenediaminium cations and water molecules in general positions (  Table 1). Furthermore, the compound shows luminescence under excitation with ultraviolet light.

Refinement
All hydrogen atoms were located the difference Fourier map and were refined isotropically with no restraints.

Figure 2
Crystal structure of the title compound viewed along the a axis. Displacement ellipsoids are drawn at the 50% probability level and hydrogen bonding is shown as dashed lines. Hydrogen atoms not involved in hydrogen bonding have been omitted for clarity. 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.