Synthesis and Crystal Structure of 4-Oxo-1,2,4-triazino[4,5-a]benzimidazole

The title compound 4-oxo-1,2,4-triazino4,5-a]benzimidazole(C9H6N4O,Mr=186.18)has been synthesized and structurally characterized by IR,NMR and single-crystal X-ray diffraction.The crystal belongs to monoclinic,space group P21/c,with a=9.1530(18),b=7.2260(14),c=12.604(3)A,β=106.92(3),V=797.5(3)(A)3,Z=4,Dc=1.551 g/cm3,2(MoKa)=0.71073,F(000)=384,μ(MoKa)=0.109 mm-1,the final R=0.0632 and wR=0.1095.A total of 1444 unique reflections were collected,of which 767 with I ＞ 2σ(I)were observed.The structure of the title compound is planar.In packing,the molecules are intersected to each other to form chains along three dimensions,together by intermolecular N-H…O and C-H…N hydrogen bonds.The whole structure is further stabilized by π…π interaction between two adjacent tricyclic ring systems, with the centroid-to-centroid distance of 3.369(4)A.