2,4,5-Tris(pyridin-4-yl)-4,5-dihydro-1,3-oxazole

In the title compound, C18H14N4O, the molecules are disordered about a crystallographic twofold axis, leading to 50:50 disorder of the O- and N-atom sites within the oxazole ring. As a consequence, symmetry-related oxazole C—N and C—O bonds are averaged. The oxazole ring makes a dihedral angle of 6.920 (1)° with the pyridyl ring in the 2-position and 60.960 (2)° with the pyridyl rings in the 4- and 5-positions.

In the title compound, C 18 H 14 N 4 O, the molecules are disordered about a crystallographic twofold axis, leading to 50:50 disorder of the O-and N-atom sites within the oxazole ring. As a consequence, symmetry-related oxazole C-N and C-O bonds are averaged. The oxazole ring makes a dihedral angle of 6.920 (1) with the pyridyl ring in the 2-position and 60.960 (2) with the pyridyl rings in the 4-and 5-positions.
In the course of our studies on transition metal complexes with tripyridyl ligands (Campos-Gaxiola et al., 2008, 2010, we have synthesized the title compound (I) and report its crystal structure here ( Fig. 1).
As part of our ongoing research on the design and synthesis of new metal complexes with fluorescent properties, we are interested in using the title compound as a ligand for the synthesis of transition and rare earth metal complexes.

Refinement
All H atoms on C atoms were positioned geometrically and refined as riding atoms, with (C-H = 0.93 Å) and U iso (H) = 1.2 U eq (C). The molecules are disordered over crystallographic 2-fold axes, therefore, the C1-N1/C1-O1 and C2-N1/C2-O1 distances are average values. The EXYZ and EADP constraint instructions in SHELXL-97 were used for atoms N1 and O1 in order to model the disorder properly during the refinement.

Computing details
Data collection: SMART (Bruker, 2000); cell refinement: SAINT-Plus (Bruker, 2001); data reduction: SAINT-Plus (Bruker, 2001); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).  The molecular structure of (I) showing displacement ellipsoids at the 50% probability level. The molecule sits on a crystallographic 2-fold axis (symmetry operation: -x + 1,y,-z + 1/2]), which forces the oxazole ring to be disordered, so that the atoms labelled O1 and N1 occupy sites that are 50% oxygen and 50% nitrogen. These are labelled separately in the diagram to emphasize the chemical nature of the molecules. 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.