Bis(9-allyl-6-carboxy-9H-carbazole-3-carboxylato-κ2 O 3,O 3′)diaquazinc

In the title compound, [Zn(C17H12NO4)2(H2O)2], the ZnII atom is located on a twofold rotation axis and is six-coordinated by four carboxylate O atoms from two chelating 9-allyl-6-carboxy-9H-carbazole-3-carboxylate ligands and two O atoms from two water molecules. In the crystal, O—H⋯O hydrogen bonds link the molecules into a layer structure parallel to (-101).

In the title compound, [Zn(C 17 H 12 NO 4 ) 2 (H 2 O) 2 ], the Zn II atom is located on a twofold rotation axis and is sixcoordinated by four carboxylate O atoms from two chelating 9-allyl-6-carboxy-9H-carbazole-3-carboxylate ligands and two O atoms from two water molecules. In the crystal, O-HÁ Á ÁO hydrogen bonds link the molecules into a layer structure parallel to (101).

Related literature
For the design and properties of complexes with supramolecular metal-organic framework structures, see: Li et al.
The asymmetric unit of the title complex ( Fig. 1) contains a Zn II atom, one 9-allyl-9H-carbazole-6-carboxy-3-carboxylate ligand and one coordinated water molecule. The Zn II atom, lying on a twofold rotation axis, is six-coordinated by four O atoms from two carboxylate ligands and two water molecules in an irregular geometry. The bond distances (Table 1) and angles are normal (Wang et al., 2010). In the crystal structure, O-H···O hydrogen bonds (Table 2) link the complex molecules into a layer structure parellel to (-1 0 1) (Fig. 2).

Experimental
The synthesis was performed under hydrothermal conditions. A mixture of 9-allyl-9H-carbazole-3,6-dicarboxylic acid (0.2 mmol, 0.062 g), Zn(NO 3 ) 2 .6H 2 O (0.1 mmol, 0.030 g) and H 2 O (15 ml) in a 25 ml stainless steel reactor with a Teflon liner was heated from 293 to 433 K in 2 h and maintained at 433 K for 72 h. Hereafter the mixture was cooled to 298 K, and colorless crystals of the title compound were obtained (yield: 59%).

Refinement
All H atoms on C atoms were positioned geometrically and refined as riding atoms, with C-H = 0.95 and 0.99 Å and with U iso (H) = 1.2U eq (C). H atoms bonded to O atoms were located in a difference Fourier map and refined as riding, with U iso (H) = 1.5U eq (O). Reflection (2 0 0) was affected by the beamstop shadow and excluded from the refinement by an OMIT instruction.      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.