Abstract
The crystal and molecular structures of dimorphic 10,10′-(1,4-phenylene-dimethylidene)-bis-9,10-H-anthracenone (1) have been determined using X-ray diffraction data. The compound crystallizes either in the monoclinic space group P21/c with a = 10.459(4), b = 8.495(3), c = 14.507(5) Å, β = 105.52(2)° (1 a) or in the triclinic space group P[unk] with a = 9.768(4), b = 12.022(5), c = 12.766(5) Å, α = 63.35(1), β = 73.37(1) and γ = 67.36(1)° (1 b). Refinement led to R = 0.084 for the monoclinic modification and R = 0.070 for the triclinic modification, respectively.
Since all non-hydrogen atoms are of pure sp2-type exact planarity would be preferred, but due to steric hindrance the molecules in both modifications deviate strongly from a planar geometry. A convenient conformation is achieved by folding of the methylidene anthrone ring and by twisting of the central phenyl ring. The molecular geometry and crystal packing effects are discussed.
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