Crystal structure of bis[(phenylmethanamine-κN)(phthalocyaninato-κ4 N)zinc] phenylmethanamine trisolvate

A pentacoordinated Zn2+ ion is found in each independent complex molecule of the title compound; the asymmetric unit is completed by three conformationally flexible non-coordinating benzylamine molecules. Supramolecular layers sustained by N—H⋯N and N—H⋯π interactions are found in the crystal packing; these are connected by π–π contacts.

The asymmetric unit of the title compound, 2[Zn(C 32 H 16 N 8 )(C 7 H 9 N)]Á3C 7 H 9 N, comprises two independent complex molecules and three benzylamine solvent molecules. Each complex molecule features a pentacoordinated Zn 2+ ion within a square-pyramidal geometry, whereby the N 5 donor set is defined by four atoms of the phthalocyaninate dianion (PC) and an N-bound benzylamine molecule; it is the relative orientations of the latter that differentiate between the independent complex molecules. The uncoordinated benzylamine molecules display different conformations in the structure, with syn-C ar -C ar -C m -N (ar = aromatic, m = methylene) torsion angles spanning the range À28.7 (10) to 35.1 (14) . In the crystal, N-HÁ Á ÁN and N-HÁ Á Á interactions lead to supramolecular layers in the ab plane. The layers have a zigzag topology, have the coordinating and non-coordinating benzylamine molecules directed to the inside, and present the essentially flat PC resides to the outside. This arrangement enables adjacent layers to associate viainteractions [intercentroid distance between pyrrolyl and fused-benzene rings = 3.593 (2) Å ] so that a three-dimensional architecture is formed.

Chemical context
Phthalocyanines of most main group metals and semi-metals, transition metals, lanthanides and actinides are known. Recent interest has centered on their electronic, photoelectronic and catalytic properties for a diverse array of applications including photodynamic therapy (Bonnett, 1995), as semiconducting materials (Yang et al., 2015), as homogeneous and heterogeneous catalysts (Sorokin, 2013), as dyes for dyesensitive solar cells (DSSC) (Ince et al., 2014), in chemical sensors (Zhang et al., 2015) and for optical data storage (de la Torre et al., 2007). The first metal phthalocyanine identified was Fe phthalocyanine (FePC), prepared in 1928 as a byproduct during the industrial production of phthalimide from the reaction of ammonia with molten phthalic anhydride in an Fe vessel (Linstead, 1934). The intense blue colour of this thermally stable material was subsequently exploited in paints and textile dyes. Another defining characteristic is the insolubility of FePC in water, common organic solvents, dilute acids and alkali. It was, however, soluble 'in hot aniline and its homologues to give intensely green solutions which contained complex additive compounds' (Linstead, 1934). Robertson and Woodward achieved the first complete X-ray crystallographic elucidation of a family member, NiPC, confirming the planar, tetra-isoindole macrocyclic structure with tetracoordinated metal (Robertson & Woodward, 1937). ISSN 2056-9890 Zinc phthalocyanine (ZnPC) is one of the more soluble members of the transition metal phthalocyanines, although a saturated solution in NMP (N-methyl-2-pyrrolidone) is still less than 7 mM (Ghani et al., 2012). This limits its wet processibility. ZnPC is known to form a weak complex with one pyridine ligand (Taube, 1974). We have an on-going interested in doped TiO 2 for use as DSSC photoanodes (Ako et al., 2015) and investigated the use of solutions of ZnPC in benzylamine for coating TiO 2 nanoparticles. This high-boiling primary amine proved to be a reasonable solvent for this dye. It was during the course of these studies that crystals of the title compound, (I), were isolated. The crystallographic characterization of (I) is described herein along with its comparison to related ZnPC adducts with N-donors. A discussion of the conformational variability of uncoordinated benzylamine is also included.

Structural commentary
The asymmetric unit of (I) comprises two independent complex molecules and three solvent benzylamine molecules. Fig. 1 shows the two complex molecules in which each Zn atom is coordinated by four N atoms derived from the phthalocyaninato (PC) dianion, as well as the amino-N atom from the benzylamine molecule. The coordination of the PC dianion leads to the formation of four linked ZnNCNCN chelate rings, each of which may be described as having an envelope conformation with the Zn atom being the flap atom. An inspection of the Zn-N(PC) bond lengths collated in Table 1 shows that these span a narrow range, i.e. 2.025 (3) Å [Zn1-N6] to 2.045 (3) [Zn1-N4] Å , suggesting extensive delocalization of -electron density over the PC chromophore. Further, the Zn-N(PC) bond lengths are systematically shorter than the Zn-N(amino) bonds. The N 5 donor set defines an approximately square-pyramidal geometry with the benzylamino-N atoms occupying the axial position. In this description, Zn1 lies 0.4670 (16) Å above the least-squares plane defined by the four PC-N atoms (r.m.s. deviation = 0.0104 Å ) in the direction of the benzylamino-N atom [2.570 (4) Å above the plane]; the comparable values for the Zn2-containing molecule are 0.4365 (16), 0.0076 and 2.549 (4) Å , respectively. That the N 5 donor set defines a square pyramid is quantified by the value of = 0.02 for each of the Zn1-and Zn2-containing molecules, which compares to the values of 0.0 and 1.0 for ideal square-pyramidal and trigonal-bipyramidal geometries, respectively (Addison et al., 1984). Further, consistent with this description is the observation that the benzylamino-N atoms are almost plumb to their respective N 4 basal planes, as seen in the values of the amino-N-Zn-N(PC) angles collated in Table 1.
As seen from the overlay diagram in Fig. 2, the ZnPC cores are virtually identical in the independent molecules. The obvious difference relates to the relative orientation of the benzylamine ligand with respect to the rest of the molecule. While the Zn-N(amino)-C(methylene)-C(phenyl) torsion angles of À178.  The molecular structures of the two independent complex molecules in (I), showing the atom-labelling scheme and displacement ellipsoids at the 50% probability level. molecules, the N(amino)-C(methylene)-C(phenyl)-C(phenyl) torsion angles of À153.6 (4) and 26.7 (7) [Zn1containing molecule] and À178.8 (4) and 1.9 (7) [Zn2] differ.
A discussion of the uncoordinated benzylamine molecules is found below in the Database survey.

Supramolecular features
Based on the standard criteria incorporated within PLATON (Spek, 2009), the most notable directional interactions in the crystal packing of (I) are N-HÁ Á ÁN hydrogen bonds, N-HÁ Á Á interactions and face-to-faceinteractions. These contacts involve six of the 10 available N-H atoms. The nature of the interactions involving amino-H atoms is high-lighted in Fig. 3, and geometric parameters characterizing the intermolecular interactions are given in Table 2. From the upper view of Fig. 3, it evident that the Zn1-bound benzylamine molecule forms two N-H donor interactions, one being a conventional N-HÁ Á ÁN hydrogen bond to the N19 atom of an uncoordinated benzylamine molecule which is orientated to place one amine-H proximate to a fivemembered NC 4 ring, leading to a N-HÁ Á Á(pyrrolyl) interaction. The second amine-H atom of the coordinating benzylamine molecule forms an N-HÁ Á Á(phenyl) inter- An overlay diagram of the two independent complex molecules in (I). The Zn1-and Zn2-containing molecules are shown as red and blue images, respectively. The molecules have been overlapped so that the N 4 square planes are coincident.

Figure 3
Detail of the N-HÁ Á ÁN and N-HÁ Á Á interactions, shown as orange and purple dashed lines, respectively, in the crystal packing of (I).
For the Zn2-containing molecule, the coordinating N18benzylamine forms a donor N-HÁ Á ÁN hydrogen bond to a non-coordinating N20-benzylamine molecule which is folded to enable a donor N-HÁ Á ÁN hydrogen bond to an exocyclic-N atom of the PC dianion. As seen from the lower view of Fig. 3, the second H atom of the N20-benzylamine molecule does not form an interaction within the standard distance criteria (Spek, 2009). The N21-benzylamine molecule forms a donor N-HÁ Á ÁN hydrogen bond to an exocyclic-N of the PC dianion. This molecule functions as the bridge between the two complex molecules and leads to the formation of supramolecular layers in the ab plane. These have a zigzag topology and present the flat PC residues to the outside with the benzylamine molecules, both coordinating and non-coordinating, in the inter-layer region. The layers stack along the c axis being connected byinteractions between pyrrolyl and fused-phenyl rings [inter-centroid (N6,C17, C18,C23,C24)Á Á Á(C57-C62) distance = 3.593 (2) Å with an angle of inclination = 6.1 (2) ]. A view of the unit cell contents is shown in Fig. 4.

Database survey
A search of the Cambridge Structural Database (Groom & Allen, 2014) revealed five nondisordered literature precedents for ZnPC complexes being additionally coordinated by simple N-donors. In no examples were coordination numbers greater than five observed. There were two examples of simple 1:1 adducts, i.e. with 4-methylpridine (Kubiak et al., 2007) and 1,8diazabicyclo(4.5.0)undec-7-ene (Janczak et al., 2011). In the 1:1 3-methylpyridin-2-amine adduct, there was an extra, noncoordinating 3-methylpyridin-2-amine molecule in the structure . A similar situation pertains in the 1:1 adduct with 4-aminopyridine but the non-coordinating solvent was tetrahydrofuran in a ratio of 1:2 (Yang et al., 2008). A particularly intriguing example was seen in the structure of ZnPC co-crystallized with pyrazine. The asymmetric unit comprises a binuclear molecule arising from a 2 -pyrazine bridge, a mononuclear species where pyrazine is in the monodentate mode and non-coordinating pyrazine in a ratio 1:2:3 ). The basic structural motif for the aforementioned literature precedents matches that reported herein for (I). In terms of geometric parameters, as seen from Table 3, generally the Zn-N(PC) bond lengths span a narrow range, and are shorter that the Zn-N(donor) bond lengths with the notable exception being the adduct with 1,8-diazabicyclo(4.5.0)undec-7-ene (Janczak et al., 2011). In this structure, the Zn-N(PC) bond lengths are systematically longer than in the other structures and the Zn-N(donor) bond shorter, consistent with a stronger coordinating ability of the 1,8-diazabicyclo(4.5.0)undec-7-ene ligand. Two related Zn complexes are known with coordinated benzylamine (L), i.e. Zn(C 6 F 5 ) 2 L 2 (Mountford et al., 2006) and in a tetrahedral Zn complex featuring a tri-pyrazolyl ligand (Coquiè re et al., 2008). In these, the Zn-N(benzylamine) bond lengths are 2.106 (4) and 2.106 (4) Å for the former, and 2.020 (4) Å in the latter, thereby being comparable and shorter, respectively, than the equivalent bonds in (I), Table 1.
Finally, a few comments on the benzylamine molecule which has now been characterized in its uncoordinated form in five crystal structures. From the syn and anti-C(phenyl)-

Figure 4
The unit-cell contents of (I), shown in projection down the a axis. Intermolecular N-HÁ Á ÁN, N-HÁ Á Á andinteractions are shown as orange, purple and blue dashed lines, respectively. One supramolecular layer sustained by N-HÁ Á ÁN and N-HÁ Á Á interactions has been highlighted in space-filling mode.
C(phenyl)-C(benzyl)-N(amine) torsion-angle data collated in Table 4 and the overlay diagram in Fig. 5, significant conformational flexibility is evident with respect to the relative orientation of the terminal amine group and the benzyl substituent. In a clathrate structure (Xiao et al., 2010), where the molecule is encapsulated within another large molecule, an almost linear arrangement is seen. However, in the remaining examples twists up to 60 in the torsion angles are observed.