Crystal structure of bis{1-phenyl-3-methyl-4-[(quinolin-3-yl)iminomethyl-κN]-1H-pyrazol-5-olato-κO}zinc methanol 2.5-solvate from synchrotron X-ray diffraction

A synthetic approach to the new zinc complex based on aminomethylene derivative of 1-phenyl-3-methyl-4-[(quinolyl-3-yl)iminomethyl]-1H-pyrazol-5(4H)-one and its structural characterization by synchrotron single-crystal X-ray diffraction are reported.

The title compound, [Zn(C 20 H 15 N 4 O) 2 ]Á2.5CH 3 OH, I, was synthesized via the reaction of zinc acetate with the respective ligand and isolated as a methanol solvate, i.e., as IÁ2.5CH 3 OH. The crystal structure is triclinic (space group P1), with two complex molecules (A and B) and five methanol solvent molecules in the asymmetric unit. One of the five methanol solvent molecules is disordered over two sets of sites, with an occupancy ratio of 0.75:0.25. Molecules A and B are conformers and distinguished by the conformations of the bidentate 1-phenyl-3-methyl-4-[(quinolin-3-yl)iminomethyl]-1H-pyrazol-5-olate ligands. In both molecules, the zinc cations have distorted tetrahedral coordination spheres, binding the monoanionic ligands through the pyrazololate O and imine N atoms. The two ligands adopt slightly different conformations in terms of the orientation of the terminal phenyl and quinoline substituents with respect to the central pyrazololate moiety. The molecular geometries of A and B are supported by intramolecular C-HÁ Á ÁO and C-HÁ Á ÁN hydrogen bonds. In the crystal of I, molecules form dimers both by secondary intermolecular ZnÁ Á ÁO [3.140 (2)-3.553 (3) Å ] andstacking interactions. The dimers are linked by intermolecular hydrogen bonds through the solvent methanol molecules into a three-dimensional network.

Chemical context
Zinc complexes of azomethine ligands with heterocyclic derivatives are the subject of significant interest owing to their photo-(PL) and electro-luminescent (EL) properties (Burlov, Chesnokov et al., 2014;Burlov, Koshchienko et al., 2014;ISSN 2056-9890 Burlov et al., 2015, 2016Nikolaevskii et al., 2014). The thermal stability, high vitrification temperatures, easy sublimation during deposition of thin amorphous films, variability of structures, relative synthetic affordability and electrontransfer characteristics of such zinc complexes make them good candidates for application as active layers for organic light-emitting diode (OLED) devices.
The zinc cations of A and B in I are four-coordinated by two monoanionic O,N-chelating ligands, which bind to the cation through pyrazololate O and imine N atoms. The coordination sphere around each zinc cation can be described as distorted tetrahedral [the bond-angle ranges are 94.83 (8)-121.00 (8) and 95.73 (8)-118.36 (10) for molecules A and B, respectively], with dihedral angles between the planar six-membered chelating rings (r.m.s. deviations are 0.031/0.021 and 0.017/ 0.033 Å for molecules A and B, respectively) of 82.97 (7) and 84.52 (7) for molecules A and B, respectively.
The four pyrazololate ligands in molecules A and B of I adopt different conformations. The main difference pertains to the twist angles of the terminal phenyl and quinoline The structures of the molecular entities in IÁ2.5CH 3 OH. Molecules A and B are shown. Displacement ellipsoids are depicted at the 50% probability level. H atoms are presented as small spheres of arbitrary radius. Dashed lines indicate intermolecular O-HÁ Á ÁN hydrogen bonds.

Figure 2
The molecular structure of conformer A.

Figure 4
The crystal packing of the dimers present in I. Dashed lines indicate intermolecular secondary ZnÁ Á ÁO interactions.

Figure 5
Synthesis scheme to obtain zinc complex I.

Synthesis and crystallization
4.1. 1-Phenyl-3-methyl-4-[(quinolin-3-imino)methyl]-1Hpyrazol-5(4H)-one A solution containing 1.44 g (0.01 mol) of 3-aminoquinoline in 10 ml of toluene was added to a solution of 2.02 g (0.01 mol) of 1-phenyl-3-methyl-4-formylpyrazol-5-one in 20 ml of toluene. The mixture was refluxed for 3 h with a Dean-Stark trap until water stripping was completed. Subsequently, twothirds of the total volume was distilled off on a rotary evaporator. The precipitate which formed was filtered off and recrystallized from ethanol to give light-yellow crystals (m.p. 473-474 K; yield 84%). FT-IR in KBr ( max , cm À1 ): 1664 A hot solution of 0.22 g of zinc acetate dihydrate (1 mmol) in 20 ml of methanol was added to hot solutions of I (0.66 g, 2 mmol) in 20 ml of the same solvent (Fig. 5). The reaction mixture was refluxed for 2 h. The precipitates of complexes were filtered off, washed three times with 10 ml of hot methanol and dried in vacuo. All products were crystallized from a chloroform-methanol (1:2 v/v) mixture and dried at 423 K, resulting in a yellow crystalline powder (m.p. 483-484 K, yield 45%). FT-IR ( max , cm À1 ): 1608 (C N

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2.
The X-ray diffraction study was carried out on the 'Belok' beamline of the National Research Center 'Kurchatov Institute' (Moscow, Russian Federation) using a Rayonix SX165 CCD detector. A total of 360 images were collected using an oscillation range of 1.0 (' scan mode, two different crystal orientations) and corrected for absorption using the Scala program (Evans, 2006). The data were indexed, integrated and scaled using the utility iMOSFLM in the CCP4 program (Battye et al., 2011).
The data completeness of 97.8% is caused by the low (triclinic) crystal symmetry. It is very difficult to get a high data completeness for this symmetry using the ' scan mode only ('Belok' beamline limitation), even though we have run two different crystal orientations.
A rather large number of reflections have been omitted from refinement due to the following reasons. (i) In order to achieve better I/ statistics for high-angle reflections, we selected an exposure time so as to admit a minor fraction of intensity overloads in the low-angle part of the detector. These low-angle reflections have imprecisely measured intensities and thus were excluded from the final steps of refinement. (ii) In the present set-up of the synchrotron diffractometer, the low-temperature device eclipses a small region of the 2D detector near the high-angle limit. This small shadowed region has not been masked during integration of the diffraction frames, which erroneously resulted in zero intensity of some reflections. (iii) The quality of the single crystal chosen for the diffraction experiment was not perfect. Some systematic differences between the calculated and observed intensities are probably caused by extinction and defects present in the crystal specimen.
The H atoms of the hydroxy groups were localized from difference Fourier maps and included in a riding mode, with fixed displacement parameters [U iso (H) = 1.5U eq (O)]. All other H atoms were placed in calculated positions, with C-H = 0.95-0.98 Å , and refined in a riding mode, with fixed isotropic displacement parameters [U iso (H) = 1.5U eq (C) for the CH 3 groups and 1.2U eq (C) for the other groups]. Disorder over two sets of sites was observed for one methanol solvent molecule (atoms O7-C83). In the last cycles of refinement, the occupancy ratio was fixed at 0.75:0.25 and each of the non-H atoms was modelled with a common displacement ellipsoid.

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.