Poly[[μ-1,4-bis(pyridin-4-ylmethyl)piperazine]bis[μ3-4-(2-carboxylatoethyl)benzoato]dicopper(II)]

The title compound is a diperiodic slab copper(II) coordination polymer held together via longer-range C—H⋯O attractive interactions.

The asymmetric unit of the title compound consists of a Cu II atom, a ceb ligand, and half of a bpmp ligand whose central piperazine ring is situated on a crystallographic inversion center.The Cu II atom is coordinated in a {NO 4 } square-pyramidal arrangement (Fig. 1) with 'longer' arm ceb carboxylate O-atom donors in trans positions in the basal plane.A carboxylate group from the 'shorter' arm ceb terminus bridges a basal position and the Jahn-Teller elongated apical position.The remaining coordination site in the basal plane is taken up by a pyridyl N-atom donor from a bpmp ligand.A modest deviation from idealized square-pyramidal coordination is indicated by the trigonality factor � of 0.11 (Addison et al., 1984).Bond lengths and angles within the coordination sphere are listed in Table 1.
The carboxylate groups of the longer arms of the ceb ligands bridge two Cu II atoms in a syn-syn fashion to construct [Cu 2 (OCO) 2 ] dimeric groups with a Cu� � �Cu distance of 2.8992 (8) A ˚.These are connected by chelating carboxylate groups belonging to the shorter ceb termini, to form [Cu 2 (ceb) 2 ] monoperiodic coordination polymer ribbons oriented along the c axis (Fig. 2).These [Cu 2 (ceb) 2 ] ribbon motifs are pillared by dipodal bpmp ligands to form [Cu 2 (ceb) 2 (bpmp)] n coordination polymer slabs that are oriented parallel to (110) (Fig. 3).Longer-range C-H� � �O attractive forces between parallel adjacent slab motifs construct the full three-dimensional crystal structure of the title compound (Fig. 4).The slabs stack in an AAA repeating pattern along the a crystal direction.

Figure 1
The copper coordination environment in the title compound with full ceb and bpmp ligands.Displacement ellipsoids are drawn at the 50% probability level.Color code: Cu dark blue, O red, N light blue, C black, and H pink.The symmetry codes are as listed in Table 1.

Figure 2
The [Cu 2 (ceb) 2 ] n coordination polymer chain in the title compound.

Figure 4
The AAA stacking of the [Cu 2 (ceb) 2 (bpmp)] n coordination polymer slabs in the title compound.

Special details
Experimental.Data was collected using a BRUKER CCD (charge coupled device) based diffractometer equipped with an Oxford low-temperature apparatus operating at 173 K.A suitable crystal was chosen and mounted on a nylon loop using Paratone oil.Data were measured using omega scans of 0.5° per frame for 30 s.The total number of images were based on results from the program COSMO where redundancy was expected to be 4 and completeness to 0.83Å to 100%.Cell parameters were retrieved using APEX II software and refined using SAINT on all observed reflections.Data reduction was performed using the SAINT software which corrects for Lp.Scaling and absorption corrections were applied using SADABS6 multi-scan technique, supplied by George Sheldrick.The structure was solved by the direct method using the SHELXT program and refined by least squares method on F2, SHELXL, incorporated in OLEX2.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.Refinement.The structure was refined by Least Squares using version 2018/3 of XL (Sheldrick, 2015b) incorporated in Olex2 (Dolomanov et al., 2009).All non-hydrogen atoms were refined anisotropically.Hydrogen atom positions were calculated geometrically and refined using the riding model, except for the Hydrogen atom on the nitrogen atom which was found by difference Fourier methods and refined isotropically.There is an unresolvable absorption artifact located as a difference peak of 1.53 e -Å -3 situated 1.45 Å from the Cu1 atom.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å
)] n , the Cu II atoms in {NO 4 } square-pyramidal coordination environments are conjoined into diperiodic coordination polymer slabs by the full span of the bridging 1,4-bis-(pyridin-4-ylmethyl)piperazine (bpmp) and 4-(carboxylethyl)benzoate (ceb) ligands.The slab motifs are expanded into the full crystal structure by means of longer-range C-H� � �O attractive interactions.

Table 2
Experimental details.