4H-Cyclopenta[def]phenanthren-4-one

In the title compound, C15H8O, the asymmetric unit contains four independent molecules and crystallizes with aromatic π–π stacking interactions[centroid–centroid distances = 3.5326 (18) Å].

In the title compound, C 15 H 8 O, the asymmetric unit contains four independent molecules and crystallizes with aromatic stacking interactions[centroid-centroid distances = 3.5326 (18) Å ].

Related literature
The title compound (Muzart, 1987) can be readily obtained by oxidation of the corresponding hydrocarbon, 4H-cyclopenta[def]-phenanthrene, see: Yang & Harvey (1992). We recently obtained it in our low pressure premixed benzeneoxygen combustion system, see: Sun et al. (2008). For our work on the use of a variety of non-organic methods to generate and trap a family of chlorinated fullerene fragments and clusters, see: Huang et al.

Comment
The title compound (I) (Muzart,1987) can be readily obtained by oxidation of the corresponding hydrocarbon, 4Hcyclopenta[def]-phenanthrene (Yang & Harvey 1992), but its crystal structure determination has not been carried out yet.
During the past decade, our group has used various non-organic methods, such as high-voltage electric discharge in liquid (Huang et al., 1997), vaporized (Xie et al., 2001, 2004 chloroform and CCl 4 and solvothermal reaction (Peng et al., 2001) to generate and trap a family of chlorinated fullerene fragments and clusters (Tan et al., 2008). Recently in our low pressure premixed benzene-oxygen combustion system (Sun et al., 2008), we obtained the title compound, C 15 H 8 O. The skeleton of title compound is similar to that of previously reported, C 15 Cl 8 O, (Peng et al.,2004). We report here the synthesis and crystal structure of the title compound, (I) (Figure 1), which was separated from the products of combustion process. Due to the aromatic nature of the molecule, the crystal packing of (I) is dominated by arene-arene supramolecular contacts and characterized by molecular stacks which are stabilized by offset face-to-face interactions.

Experimental
The title compound, C 15 H 8 O, was prepared in low pressure premixed benzene-oxygen flames. The premixed flames conditions for the soot production as the following range: atom C/O ratio:1-2; combustion chamber pressure: 350 torr. The soot collected from the water-cooled coping was extracted with toluene using an ultrasonic bath under room temperature, the resulting nigger-brown solution separated and purified by multi-stage HPLC, finally we obtained one of fractions contained pure C 15 H 8 O. The red single crystals suitable for X-ray diffraction crystallized from toluene at room temperature only in one day. The product was analyzed by mass spectrometry. The molecular peak appeared at a mass/charge ratio of 204.

Refinement
All H atoms were placed geometrically with C-H distances of 0.95 Å, N-H distances of 0.88Å and refined using a riding atom model with their isotropic displacement factors, J iso fixed at 1.2 time the U eq of the parent N and phenyl C atom, at 1.5 of methyl C atom.  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 Rfactors(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.