Abstract
Accurate studies on the effect of substituents on the crystal packing are essential for understanding the inter-molecular inter-actions and thus paving the way to crystal structure prediction. The crystal structures of diethyl 1-(4-chloro-benz-yl)-4-(4-chloro-phen-yl)-2,2-dioxo-3,4,6,7,8,8a-hexa-hydro-1H-pyrrolo-[2,1-c][1,4]thiazine-1,3-di-carboxyl-ate, C26H29Cl2NO6S, (I), and its isomorphous pair diethyl 1-(4-methyl-benz-yl)-4-(4-methyl-phen-yl)-2,2-dioxo-3,4,6,7,8,8a-hexa-hydro-1H-pyrrolo-[2,1-c][1,4]thia-zine-1,3-di-carboxyl-ate, C28H35NO6S, (II), are described. The mol-ecular aggregation patterns appear to be strikingly similar despite changes in the substituents, with a Cl atom in (I) being replaced by a methyl group in (II). Inspite of the chemical modifications, the structures of (I) and (I) are isomorphous, isostructural and found to obey the chlorine-methyl exchange rule. Both the structures feature C-H⋯O hydrogen bonding. However, a distinguishing feature between (I) and (II) is observed in the conformation of the pyrrole rings where the twist occurs on different C-N bonds. Hirshfeld analysis of both structures is presented and discussed.
Highlights
Accurate studies on the effect of substituents on the crystal packing are essential for understanding the intermolecular interactions and paving the way to crystal structure prediction
The present work reports the detailed description of the crystal structures of (I) and (II) along with Hirshfeld surface analysis of their respective intermolecular interactions
The C—HÁ Á ÁO interactions, which are similar in strength and geometry, involve only one of the two dioxo oxygen atoms, viz. O1
Summary
Crystal structure determinations of small molecules have often revealed interesting features that have direct relationships to their predicted structures In this context, the display of chlorine–methyl and benzene–thiophene exchange rules in the close-packing model of organic molecules (Kitaigorodskii, 1973) may be regarded as crucial to crystal engineering studies. In some of our earlier structure determinations to ascertain the validity of exchange rules, two obeying the chloro–phenyl exchange (Rajni Swamy et al, 2013; Rajni Swamy, 2016) and another obeying the benzene–thiophene exchange (Rajni Swamy, 2016) have been observed Both (I) and (II) are thiazine derivatives that may potentially exhibit pharmacological activities in view of the presence of nitrogen and sulfur atoms as constituents of the fused pyrrolothiazine ring (Moriyama et al, 2004; Koketsu et al, 2002; Rai et al, 2013). The present work reports the detailed description of the crystal structures of (I) and (II) along with Hirshfeld surface analysis of their respective intermolecular interactions
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