Crystal structure of the co-crystalline adduct 1,3,6,8-tetraazatricyclo[4.4.1.13,8]dodecane (TATD)–4-bromophenol (1/2)

The first crystal structure determination of a 1:2 co-crystalline adduct of 1,3,6,8-tetraazatricyclo[4.4.1.13,8]dodecane is presented. In the crystal, adducts are linked by C—H⋯O and C—H⋯Br hydrogen bonds, forming a two-dimensional network.

The structure of the 1:2 co-crystalline adduct C 8 H 16 N 4 Á2C 6 H 5 BrO, (I), from the solid-state reaction of 1, 3,6,8-tetraazatricyclo[4.4.1.1 3,8 ]dodecane (TATD) and 4-bromophenol, has been determined. The asymmetric unit of the title cocrystalline adduct comprises a half molecule of aminal cage polyamine plus a 4-bromophenol molecule. A twofold rotation axis generates the other half of the adduct. The primary inter-species association in the title compound is through two intermolecular O-HÁ Á ÁN hydrogen bonds. In the crystal, the adducts are linked by weak non-conventional C-HÁ Á ÁO and C-HÁ Á ÁBr hydrogen bonds, giving a two-dimensional supramolecular structure parallel to the bc plane.

Chemical context
The main focus of the research in our laboratory is the synthesis of a variety of molecules using cyclic aminals of the adamantane type. The prototype of these reactions is a Mannich-type reaction involving 1, 3,6,8-tetraazatricyclo-[4.4.1.1 3,8 ] dodecane (TATD) (II) with phenols which, in solution, affords di-Mannich bases of type (III) (Rivera et al., 1993(Rivera et al., , 2005. These are common systems for the investigation of hydrogen bonding and proton transfer. Engaged in the development of greener synthetic pathways, we attempted a synthesis of a di-Mannich base under solvent-free conditions by simply grinding TATD and 4-bromophenol at room temperature without using any solvent in the initial step. We found that the reaction did not provide the di-Mannich base as desired. Instead, the title compound, (I), was obtained in good yield. The reaction is run in the absence of solvent, there are no by-products, and the work-up procedure is easy. Recrystallization in an appropriate solvent gave the title compound in high yield.

Figure 2
The crystal packing of the title compound, showing two of the chains that extend along the crystal c-axis direction. C-HÁ Á ÁO and C-HÁ Á ÁBr hydrogen bonds are drawn as dashed lines.

Refinement details
Crystal data, data collection and structure refinement details are summarized in Table 2. All the H atoms were located in a difference electron density map. The hydroxyl H atom was refined freely, while C-bound H atoms were fixed geometrically (C-H = 0.95 or 0.99 Å ) and refined using a riding-model approximation, with U iso (H) set to 1.2U eq of the parent atom.  SHELXL2014 (Sheldrick, 2015); molecular graphics: XP in SHELXTL-Plus (Sheldrick, 2008) and Mercury (Macrae et al., 2006); software used to prepare material for publication: SHELXL2014 (Sheldrick, 2015).

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry.  (7)