Synthesis and Crystal Structure of 3,6-Dimethyl- 9-（4-b rom o p h enyl）- 1,8-oxo-2,7,10-trioxanth ene

The crystal structure of the title compound (C19H13BrO5) has been determined by single-crystal X-ray diffraction. The crystal is of monoclinic,space group P21/c,with a=10.508(4),b=11.354(4),c=14.522(5),β=106.255(4)°,V=1663.4(10)3,Mr=401.20,Z=4,Dc=1.602 g/cm3,λ=0.71073,F(000)=808,μ= 2.498 mm-1,R=0.0337 and wR=0.0837 for 2200 observed reflections (I>2σ(I)). X-ray analysis reveals that the dihedral angles between planes 1 and 2,1 and 3,1 and 4,2 and 3,2 and 4,and 3 and 4 are 78.6,82.5,87.4,5.6,9.5 and 4.9°,respectively. There exists a conjugated system in the molecular structure.