Crystal structure determination of 2′-nitro-10-phenylphenothiazine

The structure of the titled compound, 4, has been solved by x-ray analysis. One of the important structural features of 4 is that the 2′-nitrophenyl group is in the plane bisecting the phenothiazine ring which is in contrast to that of 10-(2′-pyrazyl)phenothiazine of 4′-nitro-10-phenylphenothiazine in which the 10-aryl group is perpendicular to the plane bisecting the phenothiazine ring. The structure of 4 is in agreement with its 1H and 13C nmr data which indicate that resonance interactions between the 2′-nitrophenyl group and the lone pair of electrons on N10 are hindered sterically by the 2′-nitro group.