catena-Poly[[[aquacopper(II)]-μ-(biphenyl-2,2′-dicarboxylato)-μ-[N,N′-bis(pyridin-4-yl)urea]] 1.25-hydrate]

A divalent copper two-dimensional coordination polymer, {[Cu(H2O)(diphenate)(bis(4-pyridyl)urea)]·1.25H2O} n , was structurally characterized by single-crystal X-ray diffraction.

In the title compound, {[Cu(C 14 H 8 O 4 )(C 11 H 10 N 4 O)(H 2 O)]Á1.25H 2 O} n , the Cu II cations are coordinated in a square-pyramidal fashion by trans carboxylate Oatom donors from two diphenate (dip) ligands, trans pyridyl N-atom donors from two bis(4-pyridyl)urea (bpu) ligands, and a ligated water molecule in the apical position. [Cu(H 2 O)(dip)(bpu)] n coordination polymer layer motifs are oriented parallel to (102). These layer motifs display a standard (4,4) rectangular grid topology and stack in an AAA pattern along the a-axis direction to form the full three-dimensional crystal structure of the title compound, mediated by N-HÁ Á ÁO and O-HÁ Á ÁO hydrogen bonding patterns involving the water molecules of crystallization.

Structure description
The title compound was isolated during an exploratory synthetic effort aiming to produce a copper coordination polymer containing both diphenate (dip) and bis(4-pyridyl)urea (bpu) ligands. The bpu ligand has seldom been used in coordination polymer chemistry to date (Kumar et al., 2007). Our group recently published a series of zinc diphenate coordination polymers that acted as turn-off luminescence sensors for nitroaromatic detection analyses (Martinez, Shrode, et al., 2018) The asymmetric unit of the title compound contains a Cu II ion, a bound water molecule, a fully deprotonated diphenate (dip) ligand, a bis(4-pyridyl)urea (bpu) ligand, a water molecule of crystallization best refined at full occupancy, and a water molecule of crystallization best refined at one-quarter occupancy. The Cu II ion displays a {CuN 2 O 3 } square-pyramidal coordination environment (Fig. 1), with the bound water molecule in the elongated apical position. The basal plane is defined by trans carboxylate O-atom data reports donors from two dip ligands, and trans pyridyl N-atom donors from two bpu ligands. Bond lengths and angles within the coordination environment are listed in Table 1 (Fig. 3). The CuÁ Á ÁCu internuclear distance spanned by the bpu ligands measures 14.03 (1) Å . A side view of a single layer motif is shown in Fig. 4. If the copper atoms are considered to be 4-connected nodes, and the organic ligands considered as simple linkers, the topology of the layer is that of a common (4,4) rectangular grid (Fig. 5).

Figure 2
The [Cu(H 2 O)(dip)] n chain motif in the title compound, oriented parallel to b.

Figure 1
The coordination environment of the title compound, showing the distorted square-pyramidal coordination at the Cu1 atom. Displacement ellipsoids are drawn at the 50% probability level.

Figure 5
Schematic perspective of the (4,4) rectangular grid topology in the title compound. The spheres represent the copper atoms, the red lines represent the dip ligands, and the blue lines represent the bpu ligands.
water molecules of crystallization anchors these water molecules to one coordination polymer layer. In turn, the water molecules of crystallization donate O-HÁ Á ÁO hydrogen bonds to unligated dip carboxylate O atoms in the neighboring layer. Details regarding the hydrogen bonding in the title compound are listed in Table 2.

Synthesis and crystallization
Cu(NO 3 ) 2 Á2.5 H 2 O (87 mg, 0.37 mmol), diphenic acid (90 mg, 0.37 mmol), bis(4-pyridyl)urea (79 mg, 0.37 mmol) and 0.75 ml of a 1.0 M NaOH solution were placed into 10 ml of distilled H 2 O in a Teflon-lined acid digestion bomb. The bomb was sealed and heated in an oven at 373 K for 24 h, and then cooled slowly to 273 K. Green-blue crystals of the title complex were obtained along with a flocculent green powder.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3.

Figure 6
AAA stacking of [Cu(dip)(bpu)] n coordination polymer layer motifs in the title compound.

catena-Poly[[[aquacopper(II)]-µ-(biphenyl-2,2′-dicarboxylato)-µ-[N,N′-bis(pyridin-4-yl)urea]] 1.25-hydrate]
Crystal data 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, 2015) 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.

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