(5,15-Dianthracen-9-yl-10,20-dihexylporphyrinato)nickel(II): a planar nickel(II) porphyrin

The title compound, [Ni(C60H52N4)], is an example of a meso tetrasubstituted nickel(II) porphyrin with both meso aryl and alkyl residues. The molecule exhibits a planar macrocycle with an average deviation of the 24 macrocycle atoms from their least-squares plane (Δ24) of 0.01 Å and an average Ni—N bond length of 1.960 (2) Å. The NiII atom lies on a center of inversion. The structure presents a rare example for a planar nickel(II) porphyrin, as meso-substituted nickel(II) porphyrins with either only meso-aryl or with meso-alkyl residues typically exhibit a ruffled conformation.

The title compound, [Ni(C 60 H 52 N 4 )], is an example of a meso tetrasubstituted nickel(II) porphyrin with both meso aryl and alkyl residues. The molecule exhibits a planar macrocycle with an average deviation of the 24 macrocycle atoms from their least-squares plane (Á24) of 0.01 Å and an average Ni-N bond length of 1.960 (2) Å . The Ni II atom lies on a center of inversion. The structure presents a rare example for a planar nickel(II) porphyrin, as meso-substituted nickel(II) porphyrins with either only meso-aryl or with meso-alkyl residues typically exhibit a ruffled conformation.

Comment
In continuation of studies on the conformational flexibility of porphyrins (Senge, 2006) the structure of the title compound was determined as an example for a meso substituted porphyrin with both meso alkyl and meso aryl subsitutents (Senge et al., 2010) and in relation to current synthetic studies on anthracenyl porphyrins (Volz & Schäffer, 1985;Davis et al., 2008;Sooambar et al., 2009).
The structure of (I), is shown in Fig. 1. The molecule exhibits a completely planar macrocycle with an average deviation of the 24 macrocycle atoms from their least-squares-plane (Δ24) of 0.01 Å and an average Ni-N bond length of 1.960 (2) Å.
All geometrical parameters are typical for a planar nickel(II) porphyrin (Senge et al., 2000). No individual macrocycle atom was displaced more then 0.015 Å from the mean plane. Likewise, differences in bond angles and lenghts between the meso aryl and meso alkyl quadrants are minimal. The anthracenyl residues are almost orthogonal to the plane of the four nitrogen atoms (96.2°) similarly to the situation found in related zinc(II) systems with meso aryl residues (Sooambar et al., 2009). In the crystal packing there are no close contacts (not shown). The anthracene residues prevent π-stacking of the porphyrins and the hexyl side chains are oriented between neighboring anthracenyl substituents and hinder π-stacking as well.

Experimental
The compound was prepared via metallation of the respective free base porphyrin and crystallized via liquid diffusion of methanol into a solution of the porphyrin in methylene chloride. Crystals were handled as described by Hope (1994).

Refinement
Hydrogen atoms were located in difference maps and refined using a standard riding model.  Fig. 1. : View of the molecular structure of I in the crystals. Thermal ellipsoids are drawn for 50% occupancy.