Crystal structure of catena-poly[[bis(acetato-κO)copper(II)]-bis[μ-4-(1H-imidazol-1-yl)phenol]-κ2 N 3:O;κ2 O:N 3]

The title compound exhibits a polymeric structure caused by long Cu⋯O interactions, which lead to the formation of chains parallel to [100]. In the crystal, the chains are arranged in a distorted hexagonal rod packing.


Chemical context
Coordination polymers have been investigated as materials with interesting properties such as magnetism (Zhu et al., 2010), luminescence (Cui et al., 2012), catalysis (Wang et al., 2011) or absorption (Zhang et al., 2017). Some coordination polymers are also known to show photocatalytic activity with respect to the decomposition of organic dyes (Yang et al., 2010;Yin et al., 2015).
In the past few years, metal complexes with ligands derived from imidazole have attracted much attention, not only for their fascinating crystal structures, but also for their interesting applications related to antifungal (Rezaei et al., 2011), pesticidal (Stenersen et al., 2004) and plant-growth regulatory properties (Choi et al., 2010), or drugs in general (Lednicer et al., 1998;Adams et al., 2001). Most of these compounds exhibit typical molecular structures whereas the number of imidazolebased coordination polymers (Martins et al., 2010;Masciocchi et al., 2001;Stamatatos et al., 2009) is much lower, probably due to the difficulty of growing single crystals. ISSN 2056-9890 In this communication we report on the synthesis and crystal structure of a copper(II) coordination polymer, [Cu(CH 3 COO) 2 (C 9 H 8 N 2 O) 2 ] n , comprising 4-(1H-imidazol-1yl)-phenol and acetate ligands.

Structural commentary
The asymmetric unit of the title compound comprises of one Cu II atom, one 4-(1H-imidazol-1-yl)-phenol ligand and one acetate group, with the Cu II atom situated on a crystallographic inversion centre. The distorted octahedral coordination environment of the Cu II atom is defined by two symmetry-related pairs of imidazole N atoms and phenol O atoms from the heterocyclic ligands and by two O atoms of a symmetry-related pair of monodentate acetate ligands (Fig. 1) (Ding et al., 2005;Song et al., 2008;Yun et al., 2008;Yu & Deng, 2011). The equatorial bond angles are in the range 86.94 (7)-93.06 (7) in the Cu1N 2 O 4 polyhedron (Table 1). The bond involving the phenolic O3 atom is very weak, with a distance of CuÁ Á ÁO = 2.739 (2) Å , completing the tetragonally distorted octahedron. The N,Obridging character of the 4-(1H-imidazol-1-yl)-phenol ligand leads to the formation of chains extending parallel to [100], whereby the ligands are oriented in an antiparallel fashion within a chain. The dihedral angle between the imidazole group (N1,N2,C1-C3) and the phenyl ring (C4-C9) is 24.07 (2) . An intrachain hydrogen bond between the phenol OH group (O3) and the non-coordinating carboxylate O atom (O1) of the acetate ligand is present (Table 2, Fig. 2).

Supramolecular features
In the crystal, the chains are aligned in a distorted hexagonal rod packing perpendicular to the chain direction. Chains are linked through intermolecular C-HÁ Á ÁO interactions between a phenyl CH group and the non-coordinating carboxylate O atom (O1) that consequently acts as a double acceptor atom (Fig. 2, Table 2). Additionalstacking interactions involving centrosymmetrically related pairs of imidazole and phenol rings, with the shortest distance between an N atom and a C atom being 3.372 (2) Å , are also present. The interplanar angle between the two rings is 24.1 (1) .

Synthesis and crystallization
4-(1H-Imidazol-1-yl)phenol (0.0480 g, 0.3 mmol) was dissolved in 5 ml ethanol, a water solution (5 ml) of Na 2 CO 3 (0.0318 g, 0.3 mmol) was slowly added, and an ethanol solution (5 ml) of Cu(NO 3 ) 2 Á2.5H 2 O (0.0349 g, 0.15 mmol) was added slowly with stirring for 30 min. To the formed cloudy suspension, an aqueous solution of acetic acid (0.3 mmol) was added. The resulting solution turned to a transparent blue colour. After stirring for three h, the solution was allowed to evaporate at room temperature. A number of blue single crystals were obtained after a few days.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. C-bound H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms with distances in the range 0.93-0.96Å and with U iso (H) = 1.2U eq (C) or 1.5U eq (C) for methyl atoms. The H atom of the phenol OH group was located in a difference map and was constrained at a distance of O-H = 0.84 Å and with U iso (H) =1.5U eq (O).

Computing details
Data collection: APEX2 (Bruker, 2013); cell refinement: SAINT (Bruker, 2013); data reduction: SAINT (Bruker, 2013); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: Mercury (Macrae et al., 2008); software used to prepare material for publication: publCIF (Westrip, 2010). 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.