4-[Bis(4-fluorophenyl)methyl]piperazin-1-ium picrate

The title compound {systematic name: 4-[bis(4-fluorophenyl)methyl]piperazin-1-ium 2,4,6-trinitrophenolate}, C17H19F2N2 +·C6H2N3O7 −, is the picrate salt of a piperazine-supported amine bearing a benzhydryl substituent on one of its N atoms. During co-crystallisation, protonation took place on the N atom of the secondary amine functionality. The non-aromatic six-membered heterocycle adopts a chair conformation. In the crystal, N—H⋯O hydrogen bonds as well as C—H⋯O contacts connect the components into a three-dimensional network.

The title compound {systematic name: 4-[bis(4-fluorophenyl)methyl]piperazin-1-ium 2,4,6-trinitrophenolate}, C 17 H 19 F 2 N 2 + Á-C 6 H 2 N 3 O 7 À , is the picrate salt of a piperazine-supported amine bearing a benzhydryl substituent on one of its N atoms. During co-crystallisation, protonation took place on the N atom of the secondary amine functionality. The non-aromatic six-membered heterocycle adopts a chair conformation. In the crystal, N-HÁ Á ÁO hydrogen bonds as well as C-HÁ Á ÁO contacts connect the components into a three-dimensional network.
Protonation occurred at the nitrogen atom that is part of the secondary amine functionality. The non-aromatic heterocycle adopts a chair conformation ( 1 C 4 , N1 C N2 ) according to a conformation analysis (Cremer & Pople, 1975). The least-squares planes defined by the carbon atoms of the two fluorophenyl moieties intersect at an angle of 73.71 (4) °. The planes defined by the atoms of the nitro groups on the picrate anion enclose angles of 7.62 (14) °, 33.52 (18) ° and 37.08 (17) °, respectively with the aromatic system they are bonded to (Fig. 1).
In the crystal, hydrogen bonds of the N-H···O type as well as C-H···O contacts are present. Both classical hydrogen bonds show bifurcation between the phenolic O atom as well as one of the nitro group's O atoms. The C-H···O contacts are supported by one of the hydrogen atoms of the non-aromatic heterocycle as well as one of the hydrogen atoms in ortho position to F atom in each of the fluorophenyl moieties. Apart from one O atom of a nitro group that forms a N-O···C g contact with a neighbouring picrate anion, all O atoms act as acceptors for hydrogen atoms. In terms of graph-set analysis (Etter et al., 1990;Bernstein et al., 1995), the descriptor for the classical hydrogen bonds is DDDD on the unitary level while the C-H···O contacts require a DD descriptor on the same level. In total, the entities of the title compound are connected to a three-dimensional network in the crystal. The shortest intercentroid distance between two centers of gravity was found at 4.0808 (7) Å and is apparent between one of the fluorophenyl moieties and the picrate anion (Fig. 2).
The packing of the title compound in the crystal structure is shown in Figure 3.
Experimental 4,4'-Difluorobenzhydryl piperazine was obtained from R. L. Fine Chem., Bengaluru, India. 4,4'-Difluorobenzhydryl piperazine (2.88 g, 0.01 mol) was dissolved in 10 ml of methanol and picric acid (2.29 g, 0.01 mol) was also dissolved in 10 ml of methanol. Both the solutions were mixed and stirred in a beaker at 333 K for 30 minutes. The mixture was kept aside for a day at room temperature. The salt formed was filtered & dried in vaccum desiccator over phosphorous pentoxide. The compound was recrystallized from a mixture of (1:1) acetone and acetonitrile by slow evaporation (m.p: 513-516 K).
supplementary materials sup-2 Refinement Carbon-bound H atoms were placed in calculated positions (C-H 0.95 Å for aromatic carbon atoms, C-H 0.99 Å for methylene groups) and were included in the refinement in the riding model approximation, with U(H) set to 1.2U eq (C).
Both nitrogen-bound H atoms were located on a difference Fourier map and refined freely. Fig. 1. The molecular structure of the title compound, with atom labels and anisotropic displacement ellipsoids (drawn at 50% probability level).