Tris[2-(2H-indazol-2-yl)ethyl]amine

The title tertiary amine, C27H27N7, a potential tripodal ligand for coordination chemistry, crystallizes with the central N atom located on a threefold axis of a trigonal cell. The gauche conformation of the N(amime)—CH2—CH2—N(indazole) chain [torsion angle = −64.2 (2)°] places the pendant 2H-indazole heterocycles surrounding the symmetry axis, affording a claw-like shaped molecule. Two symmetry-related indazole planes in the molecule make an acute angle of 60.39 (4)°. The lone pair of the tertiary N atom is located inside the cavity, and should thus be inactive (as a ligand). In the crystal, neither significant π–π nor C—H⋯π interactions between molecules are found.

The title tertiary amine, C 27 H 27 N 7 , a potential tripodal ligand for coordination chemistry, crystallizes with the central N atom located on a threefold axis of a trigonal cell. The gauche conformation of the N(amime)-CH 2 -CH 2 -N(indazole) chain [torsion angle = À64.2 (2) ] places the pendant 2Hindazole heterocycles surrounding the symmetry axis, affording a claw-like shaped molecule. Two symmetry-related indazole planes in the molecule make an acute angle of 60.39 (4) . The lone pair of the tertiary N atom is located inside the cavity, and should thus be inactive (as a ligand). In the crystal, neither significantnor C-HÁ Á Á interactions between molecules are found.

Flores-Alamo Comment
The interest in obtaining the title molecule, a new 2H-indazole derivative, is due to the potential applications for this class of compounds. Regarding pharmacological activity, these include anti-inflammatory, antitumor and antidepressants drugs (Cerecetto et al., 2005). These molecules have also been used in agriculture as selective herbicides (Ryu et al., 2001) and as precursors of other compounds to increase their biological activity and specificity (Teixeira et al., 2009). The chemistry of 2H-indazole remains less studied compared to its tautomer 1H-indazole, in part because the latter is thermodynamically more stable for the majority of derivatives (Teixeira et al., 2006). However the opposite situation also occurs in some cases (Alkorta & Elguero, 2005).
The title molecule is a tris-(2H-indazole) compound derived from a tertiary amine (Fig. 1). The molecule is placed on a threefold axis in space group R3 (Z′ = 1/3). Each arm contains a gauche N amime -CH 2 -CH 2 -N indazole chain [torsion angle: -64.2 (2)°], forming a claw-like geometry (Fig. 2). The geometry for the tertiary N atom (N3) is consistent with the presence of the lone pair inside the molecular cavity. The three symmetry-related indazole heterocycles in the molecule are arranged in such a way that no strong interactions are present. The C1-H1A group interacts weakly with the pyrazole ring of the following arm: the separation H1A···Cg i is 2.85 Å and the angle C1-H1A···Cg i is 128° (Cg is the centroid of ring N1/N2/C1/C7/C6 and i stands for symmetry code: 1 -y, 1 + x-y, z). The angle between two indazole planes in the molecule is 60.39 (4)°. Other geometric parameters compare well with those previously reported for bis-(2H-indazole) compounds (Rodríguez de Barbarín et al., 2006;Ovalle et al., 2011).

Experimental
The title molecule was obtained by a three steps reaction (Fig. 1). Condensation between tris(2-aminoethyl)amine and 2nitrobenzaldehyde produced the corresponding tris-imine (McKee et al., 2006). Selective reduction of imine bonds with sodium borohydride in methanol gave the corresponding amine, which was isolated. Then, 0.046 g of Pd/C was added to a solution of this intermediate (0.005 mol) in ethanol. The mixture was refluxed for 4 h, with addition of hydrazine monohydrate (0.110 mol) during the first 3 h. The resulting mixture was filtered, distilled, and the organic phase was extracted. The product was purified by column chromatography with silica gel and methanol as eluent.

Refinement
All H atoms were placed in idealized positions and refined as riding to their parent C atoms, with bond lengths fixed to 0.97 (methylene CH 2 ) or 0.93 Å (aromatic CH). Isotropic displacement parameters for H atoms were calculated as U iso (H) = 1.2 U eq (carrier atom).   ORTEP-like view of the title molecule, with displacement ellipsoids at the 30% probability level for non-H atoms.

Computing details
Unlabeled atoms are generated by symmetry codes: -x + y, 1 -x, z and 1 -y, 1 + x-y, z. The figure on the right is a space filling representation in the same orientation, showing the full shape of the molecule.