Monoclinic form of 7-nitro-2-phenyl-1,2-benzisoselenazol-3(2H)-one

In the course of a study of 1,2-benzoselenazin-4-one heterocyclic homologues of ebselen, a well known anti-oxidizing agent, the crystal structure determination of the title compound, C13H8N2O3Se, was carried out and revealed a monoclinic polymorph of the previously reported triclinic form. In both polymorphs, the centroids of the heterocyclic rings are nearly superimposed in projection along their normal. In the title compound, the molecular planes pack along two directions.