Poly[(μ6-benzene-1,3,5-tricarboxylato-κ6 O 1:O 1′:O 3:O 3′:O 5:O 5′)tris(N,N-dimethylformamide-κO)tris(μ3-formato-κ3 O:O:O′)trizinc(II)]

The asymmetric unit of the title compound, [Zn3(HCO2)3(C9H3O6)(C3H7NO)3]n, contains one Zn ion, one formate ligand, one N,N-dimethylformamide (DMF) ligand and one-third of a benzene-1,3,5-tricarboxylate (btc) ligand situated on a crystallographic 3 axis. Each ZnII atom is coordinated by one O atom from a DMF ligand, two O atoms from two btc ligands and three O atoms from three formate ligands in a distorted octahedral geometry. The ZnII atoms are connected by the formate and btc ligands, forming hexanuclear cores, which are linked by btc ligands, constructing a two-dimensional layered network along the ab plane.


Related literature
For general background to compounds with metal-organic frameworks, see: Eddaoudi et al. (2000)ÁThe crystal structures of isotypic compounds with Ni II and Mg II were reported by Maniam & Stock (2011) and Yeh et al. (2010), respectively.

Comment
Solvothermal reactions between Zn II ion and simple organic ligands such as benzene-1,4-dicarboxylic acid (H 2 BDC) and benzene-1,3,5-tricarboxylic acid (H 3 BTC) produce prototype metal-organic frameworks known as MOF-2, MOF-3, MOF-4, and MOF-5 (Eddaoudi et al., 2000). Among them, MOF-4 formulated as [Zn 2 (BTC)(NO 3 )](C 2 H 5 OH) 5 (H 2 O) has dinuclear zinc clusters that are held by three carboxylate groups from three distinct BTC ligands. In our trials to make a metal-organic framework composed of Zn II paddle-wheel clusters and BTC, the title compound was obtained as single crystals. During a solvothermal reaction, decomposition of N,N-dimethylformamide produced formate which became a component of the title compound.

Experimental
The title compound was obtained by a solvothermal reaction between zinc(II) nitrate tetrahydrate (0.157 g, 0.60 mmol) and benzene-1,3,5-tricarboxylic acid (0.084 g, 0.40 mmol) in N,N-dimethylformamide (2.0 ml). When a sealed glass tube containing the reaction mixture was heated at 130 °C and for 24 h, the title compound was produced as colorless hexagonal columnar crystals.

Computing details
Data collection: SMART (Bruker, 1997); cell refinement: SAINT (Bruker, 1997); data reduction: SAINT (Bruker, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: CrystalMaker (CrystalMaker, 2013); software used to prepare material for publication: publCIF (Westrip, 2010    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 > 2sigma(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.

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