Crystal structures of two isomeric 2-aryl-3-phenyl-1,3-thiazepan-4-ones

The crystal of 6-(4-nitrophenyl)-7-phenyl-5-thia-7-azaspiro[2.6]nonan-8-one (1), has monoclinic (P21/n) symmetry while that of its isomer 6-(3-nitrophenyl)-7-phenyl-5-thia-7-azaspiro[2.6]nonan-8-one (2), has orthorhombic (Pca21) symmetry: compound 1 has two molecules, A and B, in the asymmetric unit while 2 has one. In all three molecules, the seven-membered thiazepan ring exhibits a chair conformation. Except for the nitro groups, the three molecules have similar conformations when overlayed in pairs.


Figure 2
The molecular structure of 2 with displacement ellipsoids drawn at the 50% probability level.

Figure 1
The molecular structure of 1 with displacement ellipsoids drawn at the 50% probability level. C-HÁ Á ÁO interactions are shown as dashed lines. Table 1 Hydrogen-bond geometry (Å , ) for 1. molecules are arranged into layers propagating in the ab plane, with C-HÁ Á ÁO hydrogen bonds in both the a-and baxis directions, but not in the c-axis direction (Fig. 4). In 2, the molecules link up via C-HÁ Á ÁO 'head-to-tail' hydrogen bonds in the c-axis direction (Fig. 5) and hydrophobic interactions between adjacent chains consolidate the packing in the a-and b-axis directions.

Database survey
A 1,3-thiazepan-4-one with a 5,6-fused benzene and a 2,3fused triazole has been reported, but only an ORTEP representation was given, without any other data (Bakavoli et al., 2002). The structures of omapatrilat bound to proteins have been published recently (Cozier, et al. 2018

Figure 5
Packing diagram for 2 viewed down the b-axis direction.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. The hydrogen atoms were placed geometrically (C-H = 0.93-0.98 Å ) and refined as riding on their parent atoms with U iso (H) = 1.2U eq (C).

Special details
Experimental. The data collection nominally covered a full sphere of reciprocal space by a combination of 4 sets of ω scans each set at different φ and/or 2θ angles and each scan (10 s exposure) covering -0.300° degrees in ω. The crystal to detector distance was 5.86 cm. Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

Special details
Experimental. The data collection nominally covered a full sphere of reciprocal space by a combination of 4 sets of ω scans each set at different φ and/or 2θ angles and each scan (20 s exposure) covering -0.300° degrees in ω. The crystal to detector distance was 5.82 cm. Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.