catena-Poly[[[aqua(pyrazino[2,3-f][1,10]phenanthroline-κ2 N 8,N 9)zinc(II)]-μ-pentanedioato] monohydrate]

In the title compound, {[Zn(C5H6O4)(C14H8N4)(H2O)]·H2O}n, the Zn2+ ion is coordinated by an N,N′-bidentate pyrazino[2,3-f][1,10]phenanthroline (pyphen) ligand, a water molecule and a monodentate glutarate (glu) dianion. A symmetry-generated O:O′-bidentate glu dianion completes a distorted cis-ZnN2O4 octahedral coordination geometry for the metal ion. The bridging glu species generates [110] polymeric chains in the crystal. O—H⋯O hydrogen bonds involving both the coordinated and uncoordinated water molecules help to consolidate the structure and neighbouring pyphen units interact through numerous aromatic π–π interactions [minimum centroid–centroid separation = 3.654 (3) Å], resulting in a two-dimensional network.

The author thanks Baicheng Normal University for supporting this work.  [[aqua(pyrazino[2,3-f] [1,10] polymer, which is reported here. In compound (I), the Zn II atom of unit is surrounded by two N atoms derived from the bidentate PyPhen ligand, three O atoms from two glutaric acid dianions (one monodentate, one bidentate) and one water molecule ( Figure 1, Table 1) a distorted octahedral cis-ZnN 2 O 4 arrangement is formed. Neighboring Zn II atoms are bridged by the centrosymmetric glutaric acid ligands forming a one-dimensional chain structure (Fig.2). In the crystal structure, adjacent chains are connected through π-π interactions between PyPhen and PyPhen ligands with a minimum centroidcentroid stacking distance of 3.372 Å. O-H···O hydrogen bonds involving the water molecules and carboxylate O atom acceptors (Table 2) complete the structure.

Experimental
The pyphen ligand was synthesized according to the literature method of Dickeson & Summers (1970). A mixture of ZnCl 2 (0.3 mmol), pyphen (0.1 mmol) and glutaric acid (0.3 mmol) in distilled water (30 ml) was stirred thoroughly for 1 h at ambient temperature. The pH was adjusted to 7.5 with aqueous NaOH solution. The suspension was then sealed in a Teflon-lined stainless steel reaction vessel (40 ml). The reaction was performed under autogeneous pressure and static conditions in an oven at 443 K for 4.5 d. The vessel was then cooled slowly inside the oven to 298 K at a rate of 5 K h -1 before opening: amaranth (red) blocks of (I) were collected.

Refinement
All H atoms on C atoms were generated geometrically and refined as riding atoms with C-H= 0.93Å and U iso (H)= 1.2 times U eq (C).
supplementary materials sup-2 Figures Fig. 1. view of the local coordination of Zn(II) with displacement ellipsoids drawn at the 30% probability level.

Fig. 2.
A view of the two-dimensional supramolecular structure of (I) generated by π-π interactions and hydrogen-bonding.