Crystal structure of {2-methyl-2-[(pyridin-2-ylmethyl)amino]propan-1-ol-κ3 N,N′,O}bis(nitrato-κO)copper(II) from synchrotron data

The CuII ion in the title compound shows a distorted square-pyramidal coordination geometry. In the crystal, the molecules are connected by N—H⋯O, O—H⋯O, C—H⋯O and π–π interactions, forming a three-dimensional supramolecular network.

The title compound, [Cu(NO 3 ) 2 (C 10 H 16 N 2 O)], has been synthesized and characterized by synchrotron single-crystal diffraction at 100 K. The Cu II ion has a distorted square-pyramidal coordination geometry with two N and one O atoms of the C 10 H 16 N 2 O ligand and one nitrate anion in the equatorial plane and another nitrate anion at the axial position. The equatorial Cu-N and Cu-O bond lengths are in the range 1.9608 (14)-2.0861 (15) Å , which are shorter than the axial Cu-O nitrate bond length [2.1259 (16) Å ]. In the crystal, molecules are linked via intermolecular N-HÁ Á ÁO and O-HÁ Á ÁO hydrogen bonds, forming a sheet structure parallel to the bc plane. The sheets are further linked through a face-to-faceinteraction [centroid-centroid distance = 3.994 (1) Å ]. Weak intermolecular C-HÁ Á ÁO interactions are also observed in the sheet and between adjacent sheets.

Chemical context
Transition-metal complexes containing amine or its derivative ligands have attracted considerable attention owing to their diverse coordination geometries and their various applications in catalysis (Ahn et al., 2017), as magnetic materials (Liu, Zhou et al., 2017) and fluorescent substances (Chia & Tay, 2014) as well as sensing materials (Liu, Wang et al., 2017). In addition, polyamine ligands containing hydroxyl groups can easily form multinuclear complexes (such as dinuclear or trinuclear) with various transition-metal ions and hydrogenbonded supramolecular compounds due to the deprotonation of hydroxyl groups by the transition-metal ions and anions (Shin et al., 2014). For example, N-(2-pyridylmethyl)iminodiethanol and N-(2-pyridylmethyl)iminodiisopropanol ligands containing amine, pyridine and hydroxyl groups have been used to form trinuclear metal complexes with cobalt and nickel ions, respectively, and these complexes have shown significant olefin epoxidations and magnetic interactions (Shin, Jeong et al., 2016). The nitrate anion is a good candidate for the construction of multinuclear complexes or supramolecular compounds by bridging metal ions or hydrogen bonding adjacent molecules (El-Khatib et al., 2018). Here, we report the preparation and crystal structure of a copper(II) complex, [Cu(C 10

Structural commentary
A view of the molecular structure of the title compound is shown in Fig. 1. The central Cu II ion is coordinated by two nitrogen and one oxygen atoms from the C 10 H 16 N 2 O ligand and by two oxygen atoms from nitrate anions, and adopts a distorted square-pyramidal geometry. The equatorial plane consists of the two nitrogen atoms (N1 and N2) and the oxygen atom (O1) of the hydroxyl group in the C 10 H 16 N 2 O ligand and one oxygen atom (O5) of the nitrate anion. The coordination geometry is completed by an oxygen atom (O2) from the other nitrate anion in the axial position. The equatorial bond lengths, Cu-N and Cu-O, are in the range 1.9608 (14) to 2.0861 (15) Å . The axial bond length, Cu-O nitrate , is 2.1259 (16) Å . The average length of the Cu-N and Cu-O bonds between the Cu II ion and the C 10 H 16 N 2 O ligand is 2.0081 (8) Å , which is shorter than the average bond length in the reported [Cu(C 10 H 16 N 2 O)Cl 2 ] complex possessing the same ligand and metal . The axial bond length is also shorter than that in [Cu(C 10 H 16 N 2 O)Cl 2 ], which can be attributed to the size effect of the coordinated anions. The nitrate anions are coordinated in a cis position to each other and the axial bond is longer than the equatorial bond. The bite angles N1-Cu1-N2 and N2-Cu1-O1 in the fivemembered chelate rings are 84.53 (7) and 82.92 (7) , respectively.

Figure 2
A packing diagram of the title compound viewed along the a axis, showing the N-HÁ Á ÁO (purple dashed lines) and O-HÁ Á ÁO (dark green dashed lines) hydrogen bonds.

Figure 1
View of the molecular structure of the title compound, showing the atomlabelling scheme, with displacement ellipsoids drawn at the 50% probability.

Database survey
A search of the Cambridge Structural Database (Version 5.39, update of August 2018; Groom et al., 2016) shows only one mononuclear copper(II) complex with the same C 10 H 16 N 2 O ligand, for which the synthesis and crystal structure have been reported . A similar copper(II) complex with poly(2,6-dimethyl-1,4-phenylene ether) ligands involving secondary amine, pyridine and hydroxyl groups has been prepared to study its catalytic activities (Guieu et al., 2004).

Synthesis and crystallization
The C 10 H 16 N 2 O ligand was prepared according to a slight modification of the previous reported method . To a methanol solution (10 mL

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. C-bound H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms, with C-H = 0.95-0.99 Å , and with U iso (H) = 1.5 or 1.2U eq (C). The positions of the O-and N-bound H atoms were assigned based on a difference-Fourier map, and were refined with distance restraints of O-H = 0.84 (1) Å and N-H = 1.00 (1) Å , and with U iso (H) = 1.5U eq (O) and 1.2U eq (N). One reflection with a poor agreement between the measured and calculated intensities was omitted from the final refinement cycles.    Data collection: PAL BL2D-SMDC (Shin, Eom et al., 2016); cell refinement: HKL3000sm (Otwinowski & Minor, 1997); data reduction: HKL3000sm (Otwinowski & Minor, 1997); program(s) used to solve structure: SHELXT2014 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2018 (Sheldrick, 2015b); molecular graphics: DIAMOND (Putz & Brandenburg, 2014); 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.