Crystal structures of 2-(4-nitrophenyl)-3-phenyl-2,3-dihydro-4H-1,3-benzothiazin-4-one and 2-(2-nitrophenyl)-3-phenyl-2,3-dihydro-4H-1,3-benzothiazin-4-one

The crystal structures are reported of the isomeric compounds 2-(4-nitrophenyl)-3-phenyl-2,3-dihydro-4H-1,3-benzothiazin-4-one, (I), and 2-(2-nitrophenyl)-3-phenyl-2,3-dihydro-4H-1,3-benzothiazin-4-one, (II), both C20H14N2O3S, being the para-nitro and ortho-nitro forms, respectively, the meta-form of which is known [Yennawar et al. (2013). Acta Cryst. E69, o1679]. The six-membered thiazone ring fused with a benzene ring displays a screw-boat conformation with a total puckering amplitude of 0.627 (1) angstrom in (I), and a near screw-boat conformation with a total puckering amplitude of 0.600 (1) angstrom in (II). The dihedral angles between the planes of the substituent nitrophenyl and phenyl and rings with the benzene ring of the parent benzothiazone moiety are 75.93 (5) and 82.61 (5)degrees [in (I)], and 76.79 (6) and 71.66 (6)degrees [in (II)]. Weak intermolecular C-H center dot center dot center dot O hydrogen-bonding interactions between aromatic H-atom donors and both a nitro-O atom and a thiazone O-atom acceptor in (I) and a thiazone O atom in (II) are present, forming in (I) a centrosymmetric 22-membered cyclic dimer which is extended through a similar inversion-related 14-membered cyclic hydrogen-bonding association into a zigzag chain structure extending along c. In (II), a single intermolecular C-H center dot center dot center dot O hydrogen bond gives a chain structure extending along b. In addition, weak C-H center dot center dot center dot pi interactions are present in both structures [minimum C center dot center dot center dot ring-centroid separations = 3.630 (2) and 3.581 (2) angstrom, respectively].