Crystal structure of {4-[10,15,20-tris(4-methoxyphenyl)porphyrin-5-yl]benzyl 2-diazoacetato}zinc(II)

The structure of a zinc porphyrin bearing a diazo ester group at the periphery of the porphyrin ring leads to a coordination polymer featuring ZnN4O square pyramids.

In the title compound, [Zn(C 50 H 36 N 6 O 5 )], the Zn II cation is chelated by four pyrrole N atoms of the porphyrinate anion and coordinated by a symmetrygenerated keto O atom of the diazoester group in a distorted square-pyramidal geometry. The mean Zn-N(pyrrole) bond length is 2.058 Å and the Zn-O(diazoester) bond length is 2.179 (4) Å . The zinc cation is displaced by 0.2202 (13) Å from the N 4 C 20 mean plane of the porphyrinate anion toward the O atom; the involvement of this atom leads to a [100] polymeric chain in the crystal.

Chemical context
Among various functional groups, diazo derivatives are particularly attractive because of their high reactivities (Ye & McKervey, 1994). Since porphyrin macrocycles are important fluorescent probes, their functionalization by a diazo group may have many chemical and biological applications (Mix et al., 2016). However, the present study of the title compound seems to be the only reported X-ray structure of a porphyrin bearing a diazo ester group at the periphery of a porphyrin ring. In contrast, many structures of five-coordinate zinc porphyrins of the type [Zn(Porph)(L)] (Porph = is a porphinato ligand and L is a neutral ligand) are known in the literature (Nasri et al., 2016). During the course of our previous studies on diazo compounds (Ferrand et al., 2005;Galardon et al., 2000), we reported the use of metalloporphyrins for catalytic cyclopropanation and the insertion of diazoketone compounds in N-H bonds. (Nicolas et al., 2008, Nicolas et al., 2009. In this work, we describe the crystal structure of the zinc porphyrin title complex, (I), to obtain more insight into the ISSN 2056-9890 structural relationship of zinc and a diazoester group (Carrie et al., 2016;Fleischer & Shachter, 1991)

Structural commentary
The asymmetric unit of (I) is shown in Fig. 1. In the crystal, the structure is a one-dimensional polymer, wherein the Zn 2+ ion bonds to four pyrrole nitrogen atoms and to the diazo ester oxygen atom of an adjacent molecule [O60 i : symmetry code: (i) x À 1, y, z], thereby defining the propagation of the chain, Figs. 2 and 3. The bond lengths from the zinc ion to the pyrrole nitrogen atoms span the range 2.046 (4)-2.073 (4) Å , which is comparable with those reported in the literature (Nasri et al., 2016). The Zn-O(diazoester) bond length is 2.179 (4) Å , which is slightly shorter than that of ZnTCPP(acetone) (TCPP = meso-tetra(4-carboxyphenyl)porphyrin) [2.222 (2) Å ; Chen et al., 2014]. The bond lengths of the diazo group have been previously estimated from X-ray data and ab initio calculations for a series of diazocompounds (average parameters: N-N 1.1189 and N-C = 1.3263 Å ). Remarkably little variance in these bond lengths occurs, even with varied functionality around the diazo moiety (Goodman et al., 1994). For the title compound, the N-N and C-N bond lengths are 1.112 (10) and 1.285 (10) Å , respectively, which are close to those observed for an aromatic diazoketone [N-N =1.117 (8); C-N = 1.316 (9) Å ; Yanez et al., 2003]. Fig. 2 shows the polymeric nature of (I) consisting of infinite [100] chains of Zn porphyrin units with the diazoester of one unit coordinated to the zinc atom of another: the molecules are linked together in such a way as to make two different columns of porphyrin planes (Fig. 3). There are no other significant intermolecular contacts present.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table   Fragment of the polymeric structure of (I): atoms Zn1_1 and O60_1 are generated by the symmetry operations x + 1, y, z and x À 1, y, z, respectively.

Figure 3
The packing of (I) showing side-by-side polymeric chains propagating in the [100] direction.

Figure 1
The molecular structure of (I) showing 50% displacement ellipsoids.

{4-[10,15,20-Tris(4-methoxyphenyl)porphyrin-5-yl]benzyl 2-diazoacetato}zinc(II)
Crystal data   (15) Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.