Synthesis and crystal structure of (1,8-naphthyridine-κ2 N,N′)[2-(1H-pyrazol-1-yl)phenyl-κ2 N 2,C 1]iridium(III) hexafluoridophosphate dichloromethane monosolvate

The coordination environment of the IrIII atom in the complex cation is pseudo-octahedral, with an N4C2 coordination set.


Chemical context
Over the past two decades, transition-metal complexes have attracted considerable attention in both academia and industry (Dixon et al., 2000). For example, d 6 iridium complexes with pseudo-octahedral coordination environments have been widely used in electroluminescent devices (sensors and light-emitting instruments) or photocatalysis because of their long excited-state lifetime, high quantum efficiency, luminescent colour adjustment and thermal stability (Lee et al., 2013;Fan et al., 2013). Among various iridium complexes, cyclometalated iridium(III) complexes are particularly attractive for the wide-range tunability of electronic structures via the rational molecular design of different components (Zhu et al., 2016). According to the set-up of cyclometalated iridium(III) cations with general formula [(N^N)Ir(C^N) 2 ] + in which N^N refers to a diimine ligand and C^N refers to a cyclometalated ligand, the combination and variation of N^N and C^N ligands provides the opportunity to modulate the properties of the target complexes (Goswami et al., 2014;Radwan et al., 2015).
In our laboratory, a key motivation for studies in this area arises from our interest in cyclometalated iridium(III) complexes, which exhibit a strong conjugated system with a high degree of delocalized -electrons. Thus, one can enhance the non-linear optical properties of a system through the interaction between the d orbitals of Ir III and the -orbitals of an organic conjugated system (Liu et al., 2018). Here we report the crystal structure of a solvated cyclometalated iridium(III) complex, [Ir(C 9 H 7 N 2 ) 2 (C 8 H 6 N 2 )](PF 6 )ÁCH 2 Cl 2 , obtained from the reaction between an orthometalated iridium precursor ({(ppz) 2 Ir(-Cl)} 2 ) (ppz = 1-phenylpyrazole) and 1,8-naphthyridine (NAP) as an auxiliary ligand.

Structural commentary
The asymmetric unit of the title cyclometalated iridium(III) complex is composed of one [Ir(ppz) 2 (NAP)] + cation, one PF 6 À counter-ion and one CH 2 Cl 2 solvent molecule. As shown in Fig. 1, the Ir III atom is coordinated by four N and two C atoms in the form of a pseudo-octahedral [IrN 4 C 2 ] polyhedron. The axial positions are occupied by two N atoms from two ppz ligands, while the equatorial plane is defined by two N atoms from the NAP ligand and two C atoms from the ppz ligands.
The bond lengths and angles related to the ppz ligand are normal and agree with the values in other cyclometalated iridium(III) compounds based on this ligand (see Database survey for details).

Figure 2
A packing diagram of the title compound in a view along the a axis, showing the three-dimensional supramolecular network structure. C-HÁ Á ÁF hydrogen bonds are shown as dashed lines.

Figure 1
The structures of the molecular entities in the title compound, with atom labelling. Displacement ellipsoids are drawn at the 30% probability level. H atoms are represented by spheres of arbitrary radius.
The cyclometalated iridium(III) title complex (I) was synthesized from the reaction of [(ppz) 2 Ir(-Cl)] 2 with 1,8naphthyridine in a mixed solution of dichloromethane (CH 2 Cl 2 ) and methanol (MeOH) (v/v = 2/1) at 358 K with KPF 6 as counter-ion through metathesis. The reaction process was monitored by thin layer chromatography. After the reaction was complete, the mixture was dried under vacuum and separated by column chromatography on silica gel with CH 2 Cl 2 /petroleum ether (v/v = 4/1) as eluent. The pure product of the cyclometalated iridium(III) complex was obtained as a dark-yellow solid. Single crystals were grown by inter-diffusion between n-hexane and a dichloromethane solution of the pure solid with CH 2 Cl 2 /hexane (v/v = 1/1) as buffer solution at room temperature. Compared to the direct benign/inert solvents reaction system, here the inter-diffusion method was applied as a mild way for the crystallization of the title complex. The use of the buffer solution ensures stable conditions for the crystallization of co-responsive constituents (Nie et al., 2019). Therefore, well-shaped crystals of complex(I) can be obtained from the buffer area.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. Carbon-bound H-atoms were placed in calculated positions (C-H = 0.93 Å for [Ir(ppz) 2 (NAP)] + cation, C-H = 0.97 Å for CH 2 Cl 2 solvent molecule) and were included in the refinement in the ridingmodel approximation, with U iso (H) set to 1.2U eq (C).   publCIF (Westrip, 2010).

Crystal data
[Ir(C 9 H 7 N 2 ) 2 (C 8 H 6 N 2 )]PF 6 ·CH 2 Cl 2 M r = 838.57 Monoclinic, P2 1 /c a = 12.1222 ( 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.