Mechanochemical synthesis and X-ray structural characterization of three 3-nitrophenol cocrystals with three aminal cage azaadamantanes: the role of the stereoelectronic effect on intermolecular hydrogen-bonding patterns.

The structures of the cocrystalline adducts of 3-nitrophenol (3-NP) with 1,3,5,7-tetraazatricyclo[3.3.1.13,7]decane [HMTA, (1)] as the 2:1:1 hydrate, 2C6H5NO3·C6H12N4·H2O, (1a), with 1,3,6,8-tetraazatricyclo[4.3.1.13,8]undecane [TATU (2)] as the 2:1 cocrystal, 2C6H5NO3·C7H14N4, (2a), and with 1,3,6,8-tetraazatricyclo[4.4.1.13,8]dodecane [TATD, (3)] as the 2:1 cocrystal, 2C6H5NO3·C8H16N4, (3a), are reported. In the binary crystals (2a) and (3a), the 3-nitrophenol molecules are linked via O-H...N hydrogen bonds into aminal cage azaadamantanes. In (1a), the structure is stabilized by O-H...N and O-H...O hydrogen bonds, and generates ternary cocrystals. There are C-H...O hydrogen bonds present in all three cocrystals, and in (1a), there are also C-H...O and C-H...π interactions present. The presence of an ethylene bridge in the structures of (2) and (3) defines the formation of a hydrogen-bonded motif in the supramolecular architectures of (2a) and (3a). The differences in the C-N bond lengths of the aminal cage structures, as a result of hyperconjugative interactions and electron delocalization, were analysed. These three cocrystals were obtained by the solvent-free assisted grinding method. Crystals suitable for single-crystal X-ray diffraction were grown by slow evaporation from a mixture of hexanes.

Crystal structure of the co-crystalline adduct 1,3,6,8-tetra-aza-tri-cyclo-[4.4.1.13,8]dodecane (TATD)-4-iodo-phenol (1/2): supra-molecular assembly mediated by halogen and hydrogen bonding.

The asymmetric unit of the title co-crystalline adduct, 1,3,6,8-tetra-aza-tri-cyclo[4.4.1.13,8]dodecane (TATD)-4-iodo-phenol (1/2), C8H16N4·2C6H5IO, comprises a half mol-ecule of the aminal cage polyamine plus a 4-iodo-phenol mol-ecule. A twofold rotation axis generates the other half of the adduct. The components are linked by two inter-molecular O-H⋯N hydrogen bonds. The adducts are further linked into a three-dimensional framework structure by a combination of N⋯I halogen bonds and weak non-conventional C-H⋯O and C-H⋯I hydrogen bonds.

C-I⋯N short contacts as tools for the construction of the crystal packing in the crystal structure of 3,3'-(ethane-1,2-di-yl)bis-(6-iodo-3,4-di-hydro-2H-1,3-benzoxazine).

The asymmetric unit of the title compound, C18H18I2N2O2, consists of one half-mol-ecule, completed by the application of inversion symmetry. The mol-ecule adopts the typical structure for this class of bis-benxozazines, characterized by an anti orientation of the two benzoxazine rings around the central C-C bond. The oxazinic ring adopts a half-chair conformation. In the crystal, mol-ecules are linked by C-I⋯N short contacts [I⋯N = 3.378 (2) Å], generating layers lying parallel to the bc plane.

Crystal structure of 1,2-bis-(6-bromo-3,4-dihydro-2H-benz[e][1,3]oxazin-3-yl)ethane: a bromine-containing bis-benzoxazine.

The title benzoxazine molecule, C18H18Br2N2O2, was prepared by a Mannich-type reaction of 4-bromo-phenol with ethane-1,2-di-amine and formaldehyde. The title compound crystallizes in the monoclinic space group C2/c with a centre of inversion located at the mid-point of the C-C bond of the central CH2CH2 spacer. The oxazinic ring adopts a half-chair conformation. The structure is compared to those of other functionalized benzoxazines synthesized in our laboratory. In the crystal, weak C-H⋯Br and C-H⋯O hydrogen bonds stack the mol-ecules along the b-axis direction.

Crystal structure of the 1:2 co-crystal of 1,3,6,8-tetra-aza-tri-cyclo-[4.3.1.13,8]undecane (TATU) and 4-chloro-phenol (1/2).

In the title compound, C7H14N4·2C6H5ClO, which crystallized with two crystallographically independent 4-chloro-phenol mol-ecules and one 1,3,6,8-tetra-aza-tri-cyclo-[4.3.1.13,8]undecane (TATU) mol-ecule in the asymmetric unit, the independent components are linked by two O-H⋯N hydrogen bonds. The hydrogen-bond acceptor sites are two non-equivalent N atoms from the aminal cage structure, and the tricyclic system distorts by changing the C-N bond lengths. In the crystal, these hydrogen-bonded aggregates are linked into chains along the c axis by C-H⋯N hydrogen bonds. The crystal structure also features C-H⋯π contacts.

Mechanochemical synthesis and crystal structure of a 1:2 co-crystal of 1,3,6,8-tetra-aza-tri-cyclo[4.3.1.13,8]undecane (TATU) and 4-chloro-3,5-dimethyl-phenol.

Solvent-free treatment of 1,3,6,8-tetra-aza-tri-cyclo-[4.3.1.13,8]undecano (TATU) with 4-chloro-3,5-di-methyl-phenol led to the formation of the title co-crystal, C7H14N4·2C8H9ClO. The asymmetric unit contains one aminal cage mol-ecule and two phenol mol-ecules linked via two O-H⋯N hydrogen bonds. In the aminal cage, the N-CH2-CH2-N unit is slightly distorted from a syn periplanar geometry. Aromatic π-π stacking between the benzene rings from two different neighbouring phenol mol-ecules [centroid-centroid distance = 4.0570 (11) Å] consolidates the crystal packing.

Crystal structure and C-H⋯F hydrogen bonding in the fluorinated bis-benzoxazine: 3,3'-(ethane-1,2-di-yl)bis-(6-fluoro-3,4-di-hydro-2H-1,3-benzoxazine).

The title fluorinated bis-benzoxazine, C18H18F2N2O2, crystallizes with one half-mol-ecule in the asymmetric unit, which is completed by inversion symmetry. The fused oxazine ring adopts an approximately half-chair conformation. The two benzoxazine rings are oriented anti to one another around the central C-C bond. The dominant inter-molecular inter-action in the crystal structure is a C-H⋯F hydrogen bond between the F atoms and the axial H atoms of the OCH2N methyl-ene group in the oxazine rings of neighbouring mol-ecules. C-H⋯π contacts further stabilize the crystal packing.

Crystal structure of 1-[(2,3-dihydro-1H-naphtho-[1,2-e][1,3]oxazin-2-yl)meth-yl]naphthalen-2-ol: a possible candidate for new polynaphthoxazine materials.

In the title compound, C23H19NO2, an oxazine Mannich base derivative, the oxazine ring has a half-chair conformation. The 2-hy-droxy-naphthalen-1-yl substituent is placed in an axial position. There is an intra-molecular O-H⋯N hydrogen bond, forming an S(6) graph-set motif. In the crystal, mol-ecules are connected by a pair of C-H⋯π inter-actions into an inversion dimer, which is reinforced by another pair of weak C-H⋯π inter-actions. The dimers are linked by a π-π inter-action [centroid-centroid distance = 3.6268 (17) Å], consolidating a column along the a axis. Furthermore, the columns inter-act with each other by a weak C-H⋯π inter-action, generating a three-dimensional network.

Crystal structure of the co-crystalline adduct 1,3,6,8-tetra-aza-tri-cyclo-[4.4.1.1(3,8)]dodecane (TATD)-4-chloro-3,5-di-methyl-phenol (1/1).

In the crystal of the title co-crystalline adduct, C8H16N4·C8H9ClO, (I), prepared by solid-state reaction, the mol-ecules are linked by inter-molecular O-H⋯N hydrogen bonds, forming a D motif. The aza-adamantane structure in (I) is slightly distorted, with N-CH2-CH2-N torsion angles of 10.4 (3) and -9.0 (3)°. These values differ slightly from the corresponding torsion angles in the free aminal cage (0.0°) and in related co-crystalline adducts, which are not far from a planar geometry and consistent with a D 2d mol-ecular symmetry in the tetra-aza-tri-cyclo structure. The structures also differ in that there is a slight elongation of the N-C bond lengths about the N atom that accepts the hydrogen bond in (I) compared with the other N-C bond lengths. In the crystal, the two mol-ecules are not only linked by a classical O-H⋯N hydrogen bond but are further connected by weak C-H⋯π inter-actions, forming a two-dimensional supra-molecular network parallel to the bc plane.

Crystal structure of the co-crystalline adduct 1,3,6,8-tetra-aza-tri-cyclo-[4.4.1.1(3,8)]dodecane (TATD)-4-bromo-phenol (1/2).

The structure of the 1:2 co-crystalline adduct C8H16N4·2C6H5BrO, (I), from the solid-state reaction of 1,3,6,8-tetra-aza-tri-cyclo-[4.4.1.1(3,8)]dodecane (TATD) and 4-bromo-phenol, has been determined. The asymmetric unit of the title co-crystalline adduct comprises a half mol-ecule of aminal cage polyamine plus a 4-bromo-phenol mol-ecule. A twofold rotation axis generates the other half of the adduct. The primary inter-species association in the title compound is through two inter-molecular O-H⋯N hydrogen bonds. In the crystal, the adducts are linked by weak non-conventional C-H⋯O and C-H⋯Br hydrogen bonds, giving a two-dimensional supra-molecular structure parallel to the bc plane.

Crystal structure of 1,1'-[imidazolidine-1,3-diylbis(methyl-ene)]bis-(naphthalen-2-ol).

The crystal structure of the title compound, C25H24N2O2, at 173 K has monoclinic (C2/c) symmetry. The mol-ecule is located on a crystallographic twofold rotation axis with only half a mol-ecule in the asymmetric unit. The imidazolidine ring adopts a twist conformation, with a twist about the ring C-C bond. The crystal structure shows the anti-clinal disposition of the two (2-hy-droxy-naphthalen-1-yl)methyl substituents of the imidazolidine ring. The structure displays two intra-molecular O-H⋯N hydrogen bonds, each forming an S(6) ring motif.

4,4'-Dibromo-2,2'-{ethane-1,2-diylbis[(methyl-imino)-methyl-ene]}diphenol.

The asymmetric unit of the title compound, C(18)H(22)Br(2)N(2)O(2), contains one half-mol-ecule that is related to the other half by a center of inversion located at the mid-point of the central C-C bond. The hy-droxy (phenolic) groups are linked to the N atoms by O-H⋯N hydrogen bonds, which generate S(6) rings.

Synthesis of a new series of N,N'-dimethyltetrahydrosalen (H2[H2Me]salen) ligands by the reductive ring-opening of 3,3'-ethylene-bis(3,4-dihydro-6-substituted-2H-1,3-benzoxazines).

A new series of N,N'-bis(2'-hydroxy-5'-substituted-benzyl)-N,N -dimethylethane-1,2-diamines (N,N'-dimethyltetrahydrosalen) ligands were prepared in good yield by reduction of the respective 3,3'-ethylene-bis(3,4-dihydro-6-substituted-2H-1,3-benzoxazine) precursors with sodium borohydride . The ligands were characterized by IR, NMR, and elemental analysis, which showed the compounds to be consistent with the proposed structures. Ring-opening reactions of bis-1,3-benzoxazines in the presence of sodium borohydride to produce N,N'-dimethylated tetrahydrosalens (H(2) [H(2)Me]salen) have not been reported in the literature.

3,3'-Ethyl-enebis(3,4-dihydro-6-chloro-2H-1,3-benzoxazine).

The asymmetric unit of the title compound, C(18)H(18)Cl(2)N(2)O(2), contains one half of an independent mol-ecule, the other half being generated via a centre of inversion at the mol-ecular centroid. In the crystal structure, mol-ecular chains are formed through non-classical C-H⋯ O hydrogen bonds between an axial H atom of the oxazine ring and the O atom of a neighbouring mol-ecule.