Crystal structures of 2-benzylamino-4-(4-bromophenyl)-6,7,8,9-tetrahydro-5H-cyclohepta[b]pyridine-3-carbonitrile and 2-benzylamino-4-(4-chlorophenyl)-6,7,8,9-tetrahydro-5H-cyclohepta[b]pyridine-3-carbonitrile

In two cyclohepta[b]pyridine-3-carbonitrile derivatives, the cycloheptane ring adopts a half-chair conformation. In the crystals of both compounds, pairs of N—H⋯Nnitrile hydrogen bonds link the molecules, forming inversion dimers with (12) ring motifs.


Chemical context
The heterocyclic skeleton containing a nitrogen atom is the basis of many essential pharmaceuticals and of many physiologically active natural products. Molecules containing heterocyclic substructures continue to be attractive targets for synthesis since they often exhibit diverse and important biological properties. Pyridine is used in the pharmaceutical industry as a raw material for various drugs, vitamins and fungicides, and as a solvent (Shinkai et al., 2000;Jansen et al., 2001;Amr et al., 2006). Pyridines are also omnipresent in medicaments and in agrochemicals (Tomlin, 1994). Pyridine derivatives have occupied a unique position in medicinal chemistry. Among them, 2-amino-3-cyanopyridines have been identified as IKK-inhibitors (Murata et al., 2003). Many fused cyanopyridines have also been shown to have a wide spectrum of biological activity (Boschelli et al., 2004). Our interest in the preparation of pharmacologically active 3-cyanopyridine compounds led us to synthesize the title compounds and we report herein on their crystal structures. ISSN 2056-9890

Structural commentary
The molecular structures of the title compounds, (I) and (II), are shown in Figs. 1 and 2, respectively. The bromo derivative (I), crystallizes in the monoclinic space group P2 1 /n while the chloro derivative (II), crystallizes in the triclinic space group P1.

Supramolecular features
In the crystal of (I), molecules are linked by pairs of N-HÁ Á ÁN nitrile hydrogen bonds, forming inversion dimers with R 2 2 (12) ring motifs (Table 1 and Fig. 3). The resulting dimers are connected through C-HÁ Á ÁBr hydrogen bonds, forming sheets lying parallel to (101). The sheets are connected by weakstacking interactions involving adjacent inversionrelated pyridine rings with a centroid-to-centroid distance of 3.7710 (7) Å , as shown in Fig. 3. These interactions lead to the formation of a three-dimensional network.
In the crystal of (II), molecules are also linked by pairs of N-HÁ Á ÁN nitrile hydrogen bonds, forming inversion dimers with R 2 2 (12) ring motifs (Table 2 and Fig. 4). The dimers are connected through weakinteractions involving inversionrelated pyridine rings with a centroid-to-centroid distance of The molecular structure of compound (I), showing 50% probability displacement ellipsoids and the atom labelling.

Figure 3
Crystal packing diagram of compound (I), viewed along the b axis.