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

The title compound 4-oxo-1,2,4-triazino[4,5-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) ,β = 106.92(3) ,V = 797.5(3) 3,Z = 4,Dc = 1.551 g/cm3,λ(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) .