trans-(1,8-Dibenzyl-1,3,6,8,10,13-hexaazacyclotetradecane)diisonicotinatonickel(II)

In the centrosymmetric title compound, [Ni(C6H4NO2)2(C22H34N6)], the NiII ion is bonded to the four secondary N atoms of the macrocyclic ligand in a square-planar fashion and two carboxylate O atoms of the isonicotinate ions in axial positions, resulting in a tetragonally distorted octahedron. An offset face-to-face π–π stacking interaction [centroid–centroid distance = 3.674(4) Å] and N—H⋯N and N—H⋯O hydrogen-bonding interactions give rise to a one-dimensional supramolecular structure in the solid state.

In the centrosymmetric title compound, [Ni(C 6 H 4 NO 2 ) 2 -(C 22 H 34 N 6 )], the Ni II ion is bonded to the four secondary N atoms of the macrocyclic ligand in a square-planar fashion and two carboxylate O atoms of the isonicotinate ions in axial positions, resulting in a tetragonally distorted octahedron. An offset face-to-facestacking interaction [centroid-centroid distance = 3.674(4) Å ] and N-HÁ Á ÁN and N-HÁ Á ÁO hydrogen-bonding interactions give rise to a one-dimensional supramolecular structure in the solid state.

Comment
The coordination chemistry of tetraaza macrocyclic ligands has been extensively studied in the context of metalloenzymes and the construction of extended supramolecular networks (Tsuge et al., 2004;Larionova et al., 2003). In particular, Ni II macrocyclic complexes with vacant axial positions are good candidates for assembling novel multi-dimensional materials in which they can possess interesting properties (Lee & Suh, 2004). Here, we report the synthesis and structure of the title compound.
As shown in Fig. 1, the Ni II ion is coordinated by the four secondary amine N atoms of the macrocyclic ligand in a square-planar fashion and two oxygen atoms from isonicotinate ions at the axial positions, resulting in a tetragonally distorted octahedron. The average Ni-N and Ni-O bond distances are 2.062 (1) and 2.159 (1) Å, respectively. The axial Ni-O bond distance is longer than the equatorial Fe-N bond lengths, which can be attributed to the Jahn-Teller distortion of the Ni II ion and/or the ring contraction of the macrocyclic ligand. Two CO bond distances of the carboxylate group are not significantly different although one is coordinated (1.246 (4) Å) and the other is uncoordinated (1.266 (3) Å) to the Ni II ion.
The complex has an inversion center at the Ni atom and the azamacrocyclic ligand adopts thermodynamically the most stable R, R,S,S configuration (Hancock, 1990). The geometry of the tertiary nitrogen atom N3 is normal; C-N distances average 1.458 (2) Å and C-N-C angles are in the range 111.8 (2)-115.7 (2)°, which is indicative of significant contribution of sp 2 hybridization for the nitrogen atom. The shortest Ni···Ni intrachain separation within the one-dimensional chain is 10.960 (1) Å and is 31% greater than the shortest interchain Ni···Ni distance of 8.342 (1) Å.
All pyridine groups of the isonicotinates coordinating Ni II ions axially are involved in offset face-to-face π-π stacking interactions (centroid···centroid 3.674 (4) Å), which leads to a supramolecular one-dimensional polymer propagating along the c axis (Fig. 2). The pyridine rings are positioned completely parallel to each other (dihedral angle of 0.0°). The interplanar separation and the offset angle between the ring planes of isonicotinate ions are 3.545 (4) Å and 9.71 (9)°, respectively (Shetty et al., 1996).
Within a one-dimensional chain, the non-coordinated carbonyl oxygen atom of the carboxylate ion forms an intramolecular hydrogen bond with the secondary amine (N1) of the macrocycle. In addition, the nitrogen atom of isonicotinate ion forms an intermolecular hydrogen bond with the secondary amine (N2) of the macrocycle which joins the molecules into a robust one-dimensional polymer (Table 1).
The color of the solution turned from yellow to pale pink. The mixture solution was stirred for 1 h during which time a supplementary materials sup-2 pink precipitate of formed which was collected by filtration, washed with MeCN, and dried in air. Single crystals of the title compound suitable for X-ray crystallography were obtained by layering of the MeCN solution of isonicotinate on the DMF/H 2 O solution of [Ni(C 22 H 34 N 6 )Cl 2 ] for several days. Yield 0.21 g (77%).   trans- (1,3,6,8,10,