Crystal structure of [5-n-butyl-10-(2,5-dimethoxyphenyl)-2,3,7,8,13,12,17,18-octaethylporphyrinato]nickel(II)

The title compound contains one independent molecule which exhibits an overall ruffled conformation, with an average Ni—N bond length of 1.917 (13) Å. The molecules form a closely spaced lattice structure in which neighbouring porphyrins are oriented in inversion-related dimers.

The asymmetric unit of the title nickel(II) porphyrin, [Ni(C 48 H 60 N 4 O 2 )], contains one independent molecule. The average Ni-N bond length is 1.917 (13) Å . The molecules are arranged in a closely spaced lattice structure in which neighbouring porphyrins are oriented in inversion-related dimers. The nickel(II) porphyrin is characterized by a significant degree of a ruffled (B 1u ) conformation with small contributions from saddle (B 2u ) and wave (y) [E g (y)], as determined using normal structural decomposition. Disorder in the 2,5-dimethoxyphenyl substituent was modelled over two positions with a 60% occupancy for the major moiety. One of the ethyl groups is also disordered over two positions and was modelled with the major moiety being present in 51.3% occupancy.

Chemical context
The structural chemistry of porphyrin metal complexes is one of the largest explored areas of coordination chemistry. There are many studies available on metal coordination (Scheidt, 2008), aspects of macrocycle modification (Chmielewski & Latos-Grazynski, 2005), supramolecular chemistry (Beletskaya et al., 2009) and nonplanar systems (Senge, 2006). Highly substituted porphyrins (octa-, nano-, deca-, undeca-and dodecasubstitued porphyrins) are of specific interest due to the increased nonplanarity which results in the alteration of photophysical properties due to distortions within the macrocyclic ring. Non-planar porphyrins have significantly lower fluorescence yields, larger Stokes shifts and a shorter lifetime of the lowest excited state than planar ones (Rö der et al., 2010). This has resulted in the synthesis and structure of numerous highly substituted porphyrins for biomimetic studies (Senge, 2006;Senge et al., 2015). ISSN 2056-9890

Structural commentary
The title compound contains one molecule in the asymmetric unit. The -ethyl groups are either orientated above or below the plane. Ethyl groups on pyrrole rings next to a substituted meso-position alternate, whereas ethyl residues neighbouring an unsubstituted meso-position are orientated in the same direction (Fig. 1).
A conformational analysis was performed using the NSD (normal structural decomposition) method developed by Shelnutt and co-workers (Shelnutt et al., 1998). The conformation is characterized by a significant degree of ruffled (B 1u ) with small contributions from saddle (B 2u ) and wave (y) [E g (y)] (Fig. 2). There are also minor contributions from wave (x), [E g (x)] and domed (A 2u ), which is similar to both highly substituted and other Ni(II) porphyrins (Senge et al., 1992(Senge et al., , 2000Senge & Bischoff, 2001). Contributions are also evident in the A 1g in-plane distortion with smaller contributions from the E u (x). The tilt of the pyrrole rings against the 24-atom plane are N1 [24.85 (8)  The molecular structure of the title compound (only the major parts of the disordered substituents are shown). Displacement ellipsoids are drawn at the 50% probability level. Table 1 Deviations of atoms from the least-squares plane of the porphyrin ring a .

Figure 2
Normal structural decomposition (NSD) analysis of the title compound.

Supramolecular features
The unit cell of the title compound consists of two molecules, each at a distance of 4.949 Å from the 24-atom mean plane of the other. The molecules are arranged in a closely spaced lattice structure in which ethyl groups and butyl groups point towards each other to form a cage-like inversion-related dimer (Fig. 3

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The C-bound H atoms were placed in their expected calculated positions and refined using a standard riding model: C-H = 0.95-0.98 Å , with U iso (H) = 1.5U eq (C) for methyl H atoms and 1.2U eq (C) for other H atoms. Disorder in the 2,5-dimethoxyphenyl substituent was modelled over two positions with a 60% occupancy for the major moiety. The ethyl group at C12 was modelled over two positions with the major moiety being present in 51.3% occupancy. Restraints and constraints were used to model the disorder with SHELXL2014 (Sheldrick, 2015b) associated with the 2,5-dimethoxypheny group at C10 (EADP) and the ethyl group at C12 (SADI and EADP). The EADP command was also used to constrain the n-butyl chain at C5.  Data collection: APEX2 (Bruker, 2014); cell refinement: SAINT (Bruker, 2014); data reduction: SAINT (Bruker, 2014); program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015b); molecular graphics: XP in SHELXTL (Sheldrick, 2008); software used to prepare material for publication: publCIF (Westrip, 2010). [5-Butyl-10-(2,5-dimethoxyphenyl)-2,3,