(Acetylacetonato-κ2 O,O′)bis{5-fluoro-2-[3-(4-fluorophenyl)pyrazin-2-yl]phenyl-κ2 N 1,C 1}iridium(III)

In the title complex, [Ir(C16H9F2N2)2(C5H7O2)], the IrIII atom, lying on a twofold rotation axis, is hexacoordinated in a distorted octahedral geometry by two C,N-bidentate 5-fluoro-2-[3-(4-fluorophenyl)pyrazin-2-yl]phenyl ligands and one O,O′-bidentate acetylacetonate ligand. The dihedral angles between the benzene rings and the pyrazine ring are 14.66 (8) and 49.76 (12)°.


Related literature
For background to organic light-emitting diodes based on phosphorescent complexes, see: Baldo et al. (1998Baldo et al. ( , 2000. For the synthesis of the title compound, see: Ge et al. (2009).

Guo-Ping Ge and Chun-Yan Li Comment
Much attention has been paid to the phosphorescent materials in recent years for their potential applications as highly efficient electroluminescent (EL) emitters in organic light-emitting devices (OLEDs), since the first demonstration of highly efficient phosphorescent OLEDs with a maximum EQE of 4% were reported by Baldo et al. (1998Baldo et al. ( , 2000. Among these phosphorescent complexes, iridium cyclometalates often exhibit favorable photoproperties for OLEDs including short phosphorescent lifetimes, high quantum efficiencies and good stability. Ge et al. (2009) demonstrated a high efficiency yellow OLED using [Ir(dppf) 2 (acac)] [dppf = 2,3-di(4-fluorophenyl)pyrazine, acac = acetylacetone] as the dopant. In this work, we synthesized and investigated crystal structure of Ir(dppf) 2 (acac).
The mononuclear title iridium(III) complex ( Fig. 1) has an approximately octahedral coordination geometry. The Ir III ion is hexacoordinated by two C atoms and two N atoms from two C,N-bidentate dppf ligands, which exhibit cis-C,C and  Table 1. Due to steric interactions, the phenyl groups are not coplanar with the pyrazine group. The dihedral angles are 14.66 (8)° between the N1,N2/C1-C4 and C5-C10 rings and 49.76 (12)° between the N1,N2/C1-C4 and C11-C16 rings.

Experimental
The title complex was obtained according to the procedure previously reported (Ge et al., 2009). Orange crystals of the title complex suitable for X-ray structure analysis were grown from a mixed solution of dichloromethane and ethanol (v/v, 1:3).

Refinement
H atoms were placed in calculated positions and treated using a riding model, with C-H = 0.93 (aromatic) and 0.96 (CH 3 ) Å and with U iso (H) = 1.2(1.5 for methyl)U eq (C). The highest residual electron density was found at 0.81 Å from Ir atom and the deepest hole at 1.01 Å from Ir atom.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.