Poly[[aqua[μ2-1,3-bis(pyridin-4-yl)urea-κ2 N 4:N 4′]bis(μ3-5-tert-butylisophthalato-κ3 O 1:O 1′:O 3)dizinc(II)] trihydrate], a double-strand coordination polymer

A divalent zinc one-dimensional double-strand coordination polymer, [Zn2(tbuip)2(dpu)] n , was structurally characterized by single-crystal X-ray diffraction.

In the title compound, {[Zn 2 (C 12 H 12 O 4 ) 2 (C 11 H 10 N 4 O)(H 2 O)]Á3H 2 O} n , monoperiodic coordination polymer double strands are held into the triperiodic crystal structure by means of N-HÁ Á ÁO hydrogen-bonding patterns between the amide groups of the 1,3-di(pyridin-4-yl)urea ligands and unligated O atoms belonging to 5-tert-butylisophthalate ligands.One of the Zn atoms displays a tetrahedral coordination environment, while the other Zn atom adopts a fivecoordinate geometry intermediate between square pyramidal and trigonal bipyramidal.Additionally, O-HÁ Á ÁO hydrogen-bonding patterns involving the water molecules of crystallization serve as a structure-stabilizing element by aggregating the double-strand motifs.
The asymmetric unit of the title compound contains two divalent Zn atoms, two crystallographically distinct fully deprotonated tBuip ligands, one water molecule bound to Zn2, one complete dpu ligand, and three water molecules of crystallization.The Zn1 atoms display an [NO 3 ] pseudo-tetrahedral coordination environment, with a pyridyl-N donor atom from a dpu ligand, and three O atom donors belonging to three different data reports tBuip ligands.One of the tBuip ligands has a carboxylate group disordered equally in two sets of positions.In one disordered conformation, O7 binds to Zn1.In the other disordered conformation, O8A binds to Zn1.In contrast, the Zn2 atoms display an [NO 4 ] five-coordinate environment, with a trigonality factor of 0.443 (Addison & Rao, 1984) indicating an intermediate geometry between idealized squarepyramidal and trigonal-bipyramidal forms.At Zn2, the coordination environment comprises one pyridyl-N donor atom from a bpu ligand, three O atom donors belonging to three different tBuip ligands, and a ligated water molecule.Bond lengths and angles within the distinct Zn coordination environments in the title compound are listed in Table 1.Complete coordination environments and ligand sets of the asymmetric unit are shown in Fig. 1.
The carboxylate groups of the tBuip ligands bind to Zn1 and Zn2 atoms in a syn-anti fashion, giving rise to bridged {Zn 2 (OCO) 2 } dimeric clusters with a ZnÁ Á ÁZn distance of 3.969 (1) A ˚.The full span of the tBuip ligands connect the dimeric clusters into [Zn 2 (tbuip) 2 ] n coordination polymer strands oriented along the a axis (Fig. 2).In turn, parallel pairs of [Zn 2 (tbuip) 2 ] n strand motifs are connected into [Zn 2 (tbuip) 2 (dpu)] n coordination polymer double strands by tethering dpu ligands that span a ZnÁ Á ÁZn distance of 14.394 (3) A ˚(Fig. 3).The double strands motifs are oriented parallel to the a axis.

Figure 1
Distinct coordination environments in the title compound with full ligand set and complete {Zn 2 (OCO) 2 } dimeric cluster.triperiodic crystal structure of the title compound is stabilized by these supramolecular hydrogen-bonding interactions (Fig. 4).Details regarding the hydrogen-bonding patterns in the title compound are listed in Table 2.

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

Special details
Experimental.Data were 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.All H atoms were placed in calculated positions with C-H = 0.98 Å for CH 3 groups and 0.95 Å for phenyl and pyridyl groups, N-H = 0.88 Å, 0.88 Å for the coordinated water ligand and 0.87 Å for solvent water molecules.Hydrogen atoms were constrained to ride on their parent atoms, with U iso (H) = 1.2 U eq (C,N) for aromatic hydrogen atoms and N-H groups and with U iso (H) = 1.2 U eq (C,O) for methyl groups and all oxygen atoms.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å
are located between neighboring coordination polymer double strand units.These engage in O-HÁ Á ÁO hydrogen-bonding patterns involving other water molecules of crystallization, the water molecule bound to Zn2, and unligated carboxylate O atoms of the tBuip ligands.Additionally, amide groups of the dpu ligands engage in N-HÁ Á ÁO hydrogen-bonding donation to unligated carboxylate O atoms of the tBuip ligands.The full

Figure 4
Figure 4 Stacking of [Zn 2 (tbuip) 2 (dpu)] n coordination polymer double strands in the title compound, viewed down the a axis.The O atoms of the water molecules of crystallization located between adjacent ribbons are drawn as orange spheres.

Table 3
Experimental details.