metal-organic compounds 1. Introduction
Acta Crystallographica Section C
Structural Chemistry ISSN 2053-2296
Chlorido(2,3,7,8,12,13,17,18-octaethylporphyrinato)iron(III): a new triclinic polymorph of Fe(OEP)Cl Saifon A. Kohnhorst* and Kenneth J. Haller* Schools of Chemistry and Biochemistry, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand Correspondence e-mail: [email protected], [email protected] Received 10 January 2014 Accepted 4 March 2014
The previous structure determination of the title compound, [Fe(C36H44N4)Cl], was of a monoclinic polymorph [Senge (2005). Acta Cryst. E61, m399–m400]. The crystal structure of a new triclinic polymorph has been determined based on single-crystal X-ray diffraction data collected at 100 K. The asymmetric unit contains one molecule of the high-spin square-pyramidal iron(III) porphyrinate. The structure exhibits distinct nonstatistical alternative positions for most atoms and was consequently modeled as a whole-molecule disorder. The compound is characterized by an average Fe—N bond ˚ , an Fe—Cl bond length of 2.225 (4) A ˚, length of 2.065 (2) A ˚ and the iron(III) cation displaced by 0.494 (4) A from the plane of the 24-atom porphyrinate core, essentially the same as in the previously determined polymorph. Common features of the porphyrin plane–plane stacking involve two types of synthons, each of which can be further stabilized with additional H Cl interactions to the axial chloride ligand, exhibiting concerted interactions of H atoms from the ethyl groups with the -cloud electron density of adjacent molecules; the shortest methylene H-atom contacts are in the ˚ , resulting in plane–plane separations of range 2.75–2.91 A ˚ , and the shortest methyl H-atom 3.407 (4) and 3.416 (4) A ˚ , resulting in plane–plane separations contacts are 2.56–2.95 A ˚ in the monoclinic polymorph. The of 4.900 (5) and 4.909 (5) A plane-to-plane stacking synthons in the triclinic polymorph are similar, but at greater distances; the shortest methylene H-atom ˚ , resulting in plane–plane separations contacts are 2.86–2.94 A ˚ , and the shortest methyl H-atom of 3.45 (2) and 3.45 (3) A ˚ , resulting in plane–plane separations contacts are 2.89–3.20 A ˚ , consistent with the density of the of 5.081 (13) and 5.134 (13) A triclinic polymorph being 1.5% lower, suggesting lesser packing efficiency and lower stability in the triclinic polymorph. The major molecular differences found in the polymorphs is in three different orientations of the ethyl-group side chains on the periphery of the porphyrin core. Keywords: crystal structure; heme; porphyrin; polymorph; octaethylporphyrin; supramolecular structure; Fe(OEP)Cl.
368
# 2014 International Union of Crystallography
Fe(OEP)Cl, (I), is a convenient starting material to form derivatives of the iron–2,3,7,8,12,13,17,18-octaethylporphyrin macrocycle (OEP) to be used as biomimetic models for heme function (Wyllie & Scheidt, 2002), and also for other studies of iron porphyrin complexes (Senge, 2000), including their recent use, along with other chlorido and oxido derivatives, as models for malaria pigment (Puntharod et al., 2010, 2012, 2014) or as a reference compound (Kalish et al., 2002) for an archetypal high-spin five-coordinate iron(III) porphyrin (Scheidt, 2000). Although (I) was reported in a crystalline form in 1977 (Ernst et al., 1977), the first occurance of Fe(OEP)Cl in the Cambridge Structural Database (CSD, Version 5.32, May 2011; Allen, 2002) was in combination with C60 and chloroform (CSD refcode CELYOH; Olmstead et al., 1999), followed by the report of the monoclinic polymorph (refcode TOYRUU; Senge, 2005) and another multicomponent (methylene chloride solvate) report (refcode QUXFIZ; Safo et al., 2010). We present here the structure of a new triclinic polymorph of Fe(OEP)Cl which appeared serendipitously as a by-product of the frustrated synthesis of an OEP heme complex with a 2,6-dinitrophenoxy axial ligand (see Experimental), and a comparison of the plane-to-plane packing efficiency of the two polymorphs.
2. Experimental 2.1. Synthesis and crystallization
Beautiful dark-purple block-shaped crystals were obtained from the remains of a frustrated attempt to obtain an OEP heme complex with a 2,6-dinitrophenoxy axial ligand. A solution of chlorido(octaethylporphyrinato)iron(III) (1.58 mg, 2.53 mmol; Sigma) and 2,6-dinitrophenol (1.86 mg, 10.1 mmol; Sigma) in dimethylformamide (10 ml) and chloroform (90 ml) was refluxed for 6 h, and allowed to cool and stand at room temperature for 30 d, and finally filtered. The data crystal was selected from the fine crystalline product obtained. 2.2. Refinement
Crystal data, data collection and structure refinement details are summarized in Table 1, and a perspective drawing doi:10.1107/S2053229614005002
Acta Cryst. (2014). C70, 368–374
metal-organic compounds Table 1 Experimental details. Crystal data Chemical formula Mr Crystal system, space group Temperature (K) ˚) a, b, c (A , , ( ) ˚ 3) V (A Z Dx (Mg m 3) Radiation type (mm 1) Crystal size (mm) Data collection Diffractometer Absorption correction Tmin, Tmax No. of measured, independent and observed [I > 2(I)] reflections Rint Refinement R[F 2 > 2(F 2)], wR(F 2), S No. of reflections No. of parameters No. of restraints H-atom treatment ˚ 3) max, min (e A
[Fe(C36H44N4)Cl] 624.05 Triclinic, P1 100 10.4495 (3), 10.7805 (4), 15.7360 (5) 71.949 (1), 73.034 (1), 82.440 (1) 1610.42 (9) 2 1.287 Mo K 0.58 0.47 0.35 0.22
Bruker APEXII CCD area-detector diffractometer Multi-scan (SADABS; Bruker, 2009) 0.772, 0.880 34934, 9534, 7545 0.021
0.051, 0.149, 1.05 9534 727 1185 H-atom parameters constrained 1.03, 0.46
Computer programs: APEX2 (Bruker, 2005), SAINT (Bruker, 2002), SHELXS97 (Sheldrick, 2008), ORTEPIII (Burnett & Johnson, 1996), ORTEP-3 for Windows (Farrugia, 2012), SHELXL97 (Sheldrick, 2008) and publCIF (Westrip, 2010).
of the major occupancy, 0.684 (5), molecule with the labeling scheme indicated thereon is shown in Fig. 1. Intensity data measurements were carried out on a visually well-formed single dark-purple block-shaped crystal of (I)-triclinic at 100 K. The positions for all non-H atoms were located by direct methods and H atoms were added in geometrically sensible positions using the SHELX program system (Sheldrick, 2008) through the shelXle interface tool (Hu¨bschle et al., 2011). Preliminary refinement including anisotropic atomic displacement parameters for the non-H atoms revealed discrepencies in the model. Many bond distances and angles
were not reasonable, most of the core atoms exhibited atomic displacement parameters oriented out of the porphyrinate plane, and the highest peaks in the difference electron-density Fourier map were in the region near atoms C7, C8, and C27, indicating disorder. The major peaks were at rational separations for disorder of the pyrrole C atoms and the attached ethyl groups of the pyrrole ring containing atom N2. This initial disorder was incorporated into the model with identical distance and angle geometry constraints (later relaxed to restraints) imposed on the overlapping planar parts of the porphyrinate ligand and including occupancy variables for the two parts constrained to sum to unity (atom labels of the major-occupancy atoms were used for the corresponding minor-occupancy atoms but with a letter ‘m’ appended to the label). A series of least-squares refinement/difference electron-density Fourier-map calculations indicated more disordered positions of lesser magnitude, suggesting alternative positions in all areas of the porphyrinate ligand and for the axial Cl ligand. The minor positions were modeled as a second set of atomic positions for the entire molecule, with corresponding distances and angles restrained to be similar between the overlapping planes of the two partial molecules. Positional parameters were further controlled by additional restraints introduced to keep the C —Cmethylene and Cmethylene—Cmethyl distances similar, to impose planarity at C12, and to control the coplanarity of the individual pyrrole rings. H atoms were included in geometrically idealized riding ˚ ) and methylene positions for the methine (C—H = 0.95 A ˚ (C—H = 0.99 A) positions, and as idealized rigid rotating ˚ ), each with tetrahedral angles, for groups (C3v; C—H = 0.98 A the methyl H-atom positions. This highly restrained refinement of the whole-molecule disorder had 727 parameters (compared to 459 parameters for the corresponding ordered single-molecule model) and 1185 restraints. The structure was refined against all data using SHELXL97 (Sheldrick, 2008). The methyl H atoms for both the major- and the minoroccupancy partial molecules were relocated by difference electron-density ring Fourier calculations before the final cycles of refinement, demonstrating that the appropriate maxima for both the major and the minor partial H atoms were present. Anisotropic displacement parameters for the non-H atoms as described above and isotropic displacement parameters for the H atoms, maintained at Uiso(H) = 1.5Ueq(C) for methyl H atoms or at 1.2Ueq(C) otherwise, were utilized in the final cycles of least-squares refinement.
3. Results and discussion
Figure 1 Perspective drawing of the major-occupancy molecule of (I)-triclinic, showing the atomic labeling scheme. The corresponding atoms of the minor-occupancy molecule are labeled with a small letter m appended to the respective label. Atomic displacement parameters for the non-H atoms are drawn as 50% probability ellipsoids. Acta Cryst. (2014). C70, 368–374
The structure of the new triclinic polymorph of Fe(OEP)Cl is characterized by five-coordinate iron, with an average Fe—N ˚ , an Fe—Cl bond length of bond length of 2.065 (2) A ˚ ˚ 2.225 (4) A, and the iron(III) cation displaced by 0.494 (4) A from the plane of the 24-atom porphyrinate core, essentially the same as in the previously determined structures of (I) [summarized as the key characteristics of (I); see table in Supporting information]. The relative positioning of the major- and minor-occupancy molecules within the asymmetric Kohnhorst and Haller
[Fe(C36H44N4)Cl]
369
metal-organic compounds
Figure 2 Perspective drawing showing the overlap of the major- [0.684 (5)] and minor-occupancy [0.316 (5)] molecules of the whole-molecule disorder model. The major difference between the two partial molecules is the positioning of the C27/C28 ethyl group of the major-occupancy molecule to the opposite side of the porphyrinate plane as the axial chloride ligand, while the C27m/C28m ethyl group of the minor-occupancy molecule is to the same side of the porphyrinate plane as the axial chloride ligand. The bonds of the major-occupancy molecule are represented as solid lines and the bonds of the minor-occupancy molecule are represented as open lines. The atoms of the major-occupancy molecule are represented as eighthcutout spheres and the atoms of the minor-occupancy molecule are represented as open spheres, both of arbitrary radius, for clarity.
unit can be seen in a perspective drawing of the total content of the asymmetric unit (Fig. 2). The intersection of the porphyrin cores, visible in Fig. 2, allows them to occupy the same approximate space in the lattice. The larger apparent core separation can be seen on the left side of the illustration [interplanar angle between the least-squares planes through the 24-atom cores = 3.9 (3) ], with a maximum apparent ˚. separation of the core-plane atoms at C27 C27m = 0.83 A The absolute maximum apparent separation of major–minor ˚ , where the methyl atoms occurs at C28 C28m = 1.77 A group occupies opposite sides of the porphyrin plane. The striking molecular difference between the two partial molecules in the lattice is a difference in the orientations of the ethyl side chains on the periphery of the porphyrin core. With the axial chloride ligand pointing ‘up’ as a reference, the major-occupancy molecule, denoted (I)-triclinic-major, has
four adjacent ethyl groups up and four down, while the minoroccupancy molecule, denoted (I)-triclinic-minor, has five adjacent ethyl groups up and three down, as shown in the stick diagrams for the known structurally determined forms of (I) illustrated in Fig. 3. The monoclinic (Fig. 3c) polymorph, denoted (I)-monoclinic, has three ethyl groups up and five down, while both multicomponent crystals (Figs. 3d and 3e) have all eight ethyl groups down, and a closely related complex, the analogous FeIII(OEP--cation radical)Cl cationic complex (refcode JOVRIV; Scheidt et al., 1992), forms a tight face-to-face dimer with all eight ethyl groups up (Fig. 3f). The cell parameters of the (I)-monoclinic polymorph were redetermined at 100 (2) K [a = 15.0003 (8), b = 22.1238 (12), ˚ , = 106.198 (3) , V = 3172.6 (3) A ˚ 3 and dcalc = c = 9.9552 (6) A 3 1.307 Mg m ] for comparison with the (I)-triclinic polymorph. The normalized molecular volumes of the two poly˚ 3 for the (I)-monoclinic form morphic forms at 100 K [793.2 A 3 ˚ compared to 805.2 A for the (I)-triclinic form] shows the packing of the new triclinic form to be less favorable; the volume is 1.52% greater for the same composition, implying greater stability for the (I)-monoclinic polymorph. The ˚ 3 for (I)-monoclinic normalized molecular volume of 798.5 A at the previous structure determination temperature (Senge, 2005) demonstrates a volume increase of 0.67% for the 26 K higher temperature (thus, less than 1% relative volume change for the structures discussed herein). A partial packing diagram for (I)-monoclinic showing the adjacent molecules that directly contact the porphyrin core is given in Fig. 4. The packing is dominated by four modified – stacking motifs, each exhibiting concerted weak supramolecular interactions. Previous discussion of – contacts by the authors has long involved contacts between -cloud electron density on adjacent delocalized fragments where the non-H atoms being considered are sp2-hybridized (Haller & Enemark, 1978). Senge’s report (Senge, 2005) that (I)-monoclinic has very weak – aggregates of the aromatic systems ˚ , more akin to with a mean plane separation of 4.02 (1) A methyl–methyl contacts (Pauling, 1960) than aromatic– aromatic contacts, piqued our curiosity to examine these
Figure 3 Comparison of the various Fe(OEP)Cl side-group orientations found to date: (a) (I)-monoclinic, (b) (I)-triclinic-major, (c) (I)-triclinic-minor, (d) (I)CH2Cl2, (e) (I)C60CHCl3 and (f) Fe(OEP--cation radical)Cl.
370
Kohnhorst and Haller
[Fe(C36H44N4)Cl]
Acta Cryst. (2014). C70, 368–374
metal-organic compounds
Figure 5 Figure 4 Projection drawings showing the – stackings in the (I)-monoclinic lattice: (a) viewed parallel to the porphyrin planes of (I), showing the four packing/stacking interactions to the porphyrin planes; (b) viewed perpendicular to the porphyrin plane of (I), showing adjacent parallel molecules with CH2 plane contacts; (c) viewed perpendicular to the porphyrin plane of (I), showing adjacent parallel molecules with Me plane contacts. Atoms are represented by spheres of arbitrary radii. Acta Cryst. (2014). C70, 368–374
Projection drawings showing the – stackings in the (I)-triclinic lattice: (a) viewed parallel to the porphyrin planes of (I), showing the six packing/ stacking interactions to the porphyrin planes; (b) viewed perpendicular to the porphyrin plane of (I), showing adjacent parallel molecules with CH2 plane contacts; (c) viewed perpendicular to the porphyrin plane of (I), showing adjacent parallel molecules with Me plane contacts. Atoms are represented by spheres of arbitrary radii. Only the major positions of the atoms are shown. Kohnhorst and Haller
[Fe(C36H44N4)Cl]
371
metal-organic compounds
Figure 6 Projection drawings showing the – stackings in the (I)CH2Cl2 lattice: (a) viewed parallel to the porphyrin planes of (I), showing the five packing/ stacking interactions to the porphyrin planes; (b) viewed perpendicular to the porphyrin plane of (I), showing adjacent parallel molecules with CH2 plane contacts; (c) viewed perpendicular to the porphyrin plane of (I), showing adjacent parallel molecules with Me plane contacts. Atoms are represented by spheres of arbitrary radii.
contacts more closely. We cannot find the reported porphyrin ˚ . In fact, the planar plane-to-plane contact distance of 4.02 A systems in OEP consist of the 24-atom porphyrin core plus the eight methylene C atoms of the ethyl groups. In the polymorphic structures under consideration here, methylene H atoms can be seen to be between the planes of the interacting rings [as in Fig. 4(a) for (I)-monoclinic]. This leads to – ˚ on the chloride side of the contact distances of 3.407 (4) A ˚ porphyrin core (Fig. 4a, upper-left quadrant) and 3.416 (4) A on the opposite side (Fig. 4a, lower-right quadrant) for (I)monoclinic, similar to Pauling’s aromatic – contact estimate ˚ half-thickness of an aromatic ring (Pauling, 1960; of 1.7 A Haller et al., 1979). The corresponding methylene H interactions (perpendicular distance from the H atom to the best porphyrin 24-atom least-squares plane) range between ˚ . Furthermore, the remaining plane– 2.75 (3) and 2.89 (4) A plane interactions show a second type of aliphatic H atom-toporphyrin plane interaction at similar H distances invol-
372
Kohnhorst and Haller
[Fe(C36H44N4)Cl]
ving methyl H atoms (vide infra). The lower-left quadrant of Fig. 4(c) shows an ideal stacking/packing interaction opposite the chloride ligand, across the inversion center at (12, 0, 0), involving eight ethyl groups in an interlocking arrangement between two adjacent molecules. The shortest methyl H interactions from the central four ethyl groups in contact with ˚ and the inversion-related planes are in the range 2.90–2.96 A ˚ the plane–plane distance is 4.909 (5) A. The upper-right quadrant contains a similar methyl-to-porphyrin plane stacking/packing interaction, across the inversion center at (1, 0, 12), involving only six ethyl groups (a consequence of only three ethyl groups on the chloride side of the molecule) and placing a single methyl group in contact with the face of the corresponding pyrrole ring, but also including C—H Cl ˚ and support, with shortest methyl H interactions of 2.82 A ˚ . Much of the additional a plane–plane distance of 4.900 (5) A plane–plane separation of these contacts results from the distances of the methyl C atoms to the porphyrin plane. Acta Cryst. (2014). C70, 368–374
metal-organic compounds interactions, one nearly ideal involving four concerted methyl–plane contacts and the other involving two concerted methyl–plane contacts, as discussed above. (I)-Triclinic-major does not exhibit the ideal highly concerted interaction, but instead contains four of the two concerted methyl–plane contacts (Fig. 5c), all of which occur across inversion centers and provide porphyrin plane–plane contact distances of ˚ on both the top and the bottom 5.081 (13) and 5.134 (14) A sides of the porphyrin plane, compared with the shorter ˚ in (I)-monoclinic. The contacts of 4.900 (5) and 4.910 (5) A average ruffling of the porphyrin cores is the same [ = ˚ for (I)-monoclinic (Senge, 2005) and = 0.043 A ˚ for 0.045 A (I)-triclinic]. Thus, the core conformation is unlikely to contribute to the observed density differences. The plane-to-
Figure 7 Projection drawings showing the two equivalent CH2 plane – stacking/packing contacts on the chloride side of the porphyrin plane in the C60(I)CH2Cl2 lattice: (a) viewed parallel to the porphyrin planes of (I); (b) viewed perpendicular to the porphyrin planes of (I). Atoms are represented by spheres of arbitrary radii.
The packings of the two polymorphic forms have a common edge-to-edge contact feature between adjacent parallel porphyrin cores, as illustrated by the left halfs of the perpendicular views in Figs. 4(b) and 5(b). This compact region contains the complete plane-to-plane edge contact extending from one methylene group to the fourth methylene group around the porphyrin core (nine C atoms). The second and third methylene group H atoms contact the adjacent porphyrin core plane in an efficient plane-to-plane stacking motif mediated by extensive – and H contacts, further supported by four C—H Cl contacts in two R12 (10) motifs (Etter et al., 1990), combined to make the arguably most stable supramolecular interaction represented within the lattice; the closest methylene C—H interactions range from 2.86 to ˚ , and the methylene C—H Cl interactions are at 2.85 2.94 A ˚ . The resulting perpendicular distance between the and 3.10 A ˚ in (I)-triclinic-major, and similar porphyrin cores is 3.45 (2) A ˚ where but somewhat shorter in (I)-monoclinic at 3.407 (4) A ˚. the methylene C—H Cl interactions are at 2.86 and 2.97 A A weaker methylene–plane contact extending approximately six C atoms along the opposite edge also occurs in each of the polymorphs on the bottom side of the porphyrin plane (Figs. 4b and 5b), with closest methylene C—H interactions ˚ and the perpendicular distance ranging from 2.89 to 3.20 A ˚ in (I)-triclinicbetween the porphyrin cores at 3.45 (3) A major; again, this value is similar but slightly shorter in (I)˚ . Thus, the monoclinic polymorph monoclinic at 3.416 (4) A ˚ has on average 0.036 A or 1.05% tighter methylene plane– plane contacts than the triclinic polymorph. A second common feature in the packings of the two polymorphs is similar corner-to-corner interactions involving methyl H contacts. (I)-Monoclinic contains two of these Acta Cryst. (2014). C70, 368–374
Figure 8 Projection drawings showing the – stackings in the Fe(OEP--cation radical)Cl lattice: (a) viewed parallel to the porphyrin planes, showing the four packing/stacking interactions to the porphyrin planes (the lower interaction is the tight face-to-face dimer interaction; Scheidt et al., 1992); (b) viewed perpendicular to the porphyrin plane, showing adjacent parallel molecules with Me plane contacts. Atoms are represented by spheres of arbitrary radii. Kohnhorst and Haller
[Fe(C36H44N4)Cl]
373
metal-organic compounds plane contacts are all shorter for the (I)-monoclinic polymorph, viz. 1.05% (2–3) for the methylene C—H and ˚ or 4.05% (10–20) for the methyl C—H contacts. 0.202 A The average difference in the spacings, at 2.55% in favor of the previously reported monoclinic form, is significantly greater than the 1.52% change in density, but nonetheless supports greater stability for the monoclinic polymorph. The other existing Fe(OEP)Cl structures both exhibit all eight ethyl groups on the opposite side of the porphyrin plane relative to the Fe and Cl atoms. The more highly concerted R12 (10) supramolecular motifs observed in (I)-monoclinic and (I)-triclinic also occur in these structures. The compact complete 9-C edge–edge methylene–plane synthon, including the four C—H Cl interactions, occurs once in the structure of the methyene chloride solvate (Safo et al., 2010), as shown in the projection diagram viewed perpendicular to the porphyrin core in Fig. 6(b), and twice in the methylene chloride solvated (I)C60 cocrystal structure (Olmstead et al., 1999), as shown in the projection diagram viewed perpendicular to the porphyrin core in Fig. 7(b). These are the only porphyrin plane–plane interactions in the (I)C60 cocrystal structure since the eight ethyl groups embrace the C60 molecule, completely filling the space opposite the chloride ligand and giving shortest – fullerene-to-N4 plane contacts of ˚ (Olmstead et al., 1999). 2.748 A The nearly perfect concerted four methyl–plane-type interaction found in (I)-monoclinic occurs twice in (I)CH2Cl2, completely covering the aliphatic side of the porphyrin plane, as shown in Fig. 6(c). The remainder of the porphyrin plane– plane contacts in (I)CH2Cl2 are a third type of methylene– plane contact, i.e. corner–corner-type contacts involving only one methylene group per molecule in contact with the face of pyrrole rings, as can be seen on the right-hand side of Fig. 6(b). The common nature of the supramolecular contacts in all occurrences of (I) to date is reflected in the shortest Fe Fe contact distance [see table of key characteristics of (I) in the ˚ in (I)Supporting information], which range from 7.896 A ˚ monoclinic to 8.079 A in (I)CH2Cl2. The pronounced lateral shifts place all of these occurrences of (I) in Group W (Scheidt, 2000). The closely related analogous FeIII(OEP--cation radical)Cl cationic complex (Scheidt et al., 1992) forms a tight ˚ ; lower face-to-face dimer (plane–plane distance of 3.24 A portion of Fig. 8a), with all eight ethyl groups required to be on the chloride side of the porphyrin plane. The aliphatic side
374
Kohnhorst and Haller
[Fe(C36H44N4)Cl]
of the complex exhibits two of the two concerted methyl– plane contacts found in both polymorphs (right-hand side, Fig. 8b) and a new full edge–edge contact (left-hand side, Fig. 8b) analogous to the methylene – contact. This investigation was supported by the Thai Commission on Higher Education with a PhD study grant (No. CHE-PHDTH-2550) to SAK. Supporting information for this paper is available from the IUCr electronic archives (Reference: SF3221).
References Allen, F. H. (2002). Acta Cryst. B58, 380–388. Bruker (2002). SAINT. Bruker AXS Inc., Madison, Wisconsin, USA. Bruker (2005). APEX2. Bruker AXS Inc., Madison, Wisconsin, USA. Bruker (2009). SADABS. Bruker AXS Inc., Madison, Wisconsin, USA. Burnett, M. N. & Johnson, C. K. (1996). ORTEPIII. Report ORNL-6895. Oak Ridge National Laboratory, Tennessee, USA. Ernst, J., Subramanian, J. & Fuhrhop, J.-H. (1977). Z. Naturforsch. Teil A Phys. Sci. 32, 1129–1136. Etter, M. C., MacDonald, J. C. & Bernstein, J. (1990). Acta Cryst. B46, 256– 262. Farrugia, L. J. (2012). J. Appl. Cryst. 45, 849–854. Haller, K. J. & Enemark, J. H. (1978). Acta Cryst. B34, 102–109. Haller, K. J., Johnson, P. L., Feltham, R. D., Enemark, J. H., Ferraro, J. R. & Basile, L. J. (1979). Inorg. Chim. Acta, 33, 119–130. Hu¨bschle, C. B., Sheldrick, G. M. & Dittrich, B. (2011). J. Appl. Cryst. 44, 1281– 1284. Kalish, H., Camp, J. E., Stepien, M., Latos-Grazynski, L., Olmstead, M. M. & Balch, A. L. (2002). Inorg. Chem. 41, 989–997. Olmstead, M. M., Costa, D. A., Maitra, K., Noll, B. C., Phillips, S. L., Van Calcar, P. M. & Balch, A. L. (1999). J. Am. Chem. Soc. 121, 7090–7097. Pauling, L. (1960). The Nature of the Chemical Bond, 3rd ed., p. 260. Ithaca: Cornell University Press. Puntharod, R., Haller, K. J., Robertson, E. & Wood, B. R. (2014). J. Raman Spectrosc. In preparation. Puntharod, R., Webster, G. T., Asghari-Khiavi, M., Bambery, K. R., Safinejad, F., Rivadehi, S., Langford, S. J., Haller, K. J. & Wood, B. R. (2010). J. Phys. Chem. B, 114, 12104–12115. Puntharod, R., Wood, B. R. & Haller, K. J. (2012). Adv. Mater. Res. 506, 222– 225. Safo, M. K., Buentello, K. E., Oliver, A. G. & Scheidt, W. R. (2010). Acta Cryst. E66, m733. Scheidt, W. R. (2000). The Porphyrin Handbook, Vol. 6, edited by K. M. Kadish, R. Guilard & K. M. Smith, pp. 49–112. San Diego: Academic Press. Scheidt, W. R., Song, H., Haller, K. J., Safo, M. K., Orosz, R. D., Reed, C. A., Debrunner, P. G. & Schulz, C. E. (1992). Inorg. Chem. 31, 941–944. Senge, M. O. (2000). The Porphyrin Handbook, Vol. 10, edited by K. M. Kadish, R. Guilard & K. M. Smith, pp. 1–218. San Diego: Academic Press. Senge, M. O. (2005). Acta Cryst. E61, m399–m400. Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Westrip, S. P. (2010). J. Appl. Cryst. 43, 920–925. Wyllie, G. R. A. & Scheidt, W. R. (2002). Chem. Rev. 102, 1067–1089.
Acta Cryst. (2014). C70, 368–374
supplementary materials
supplementary materials Acta Cryst. (2014). C70, 368-374
[doi:10.1107/S2053229614005002]
Chlorido(2,3,7,8,12,13,17,18-octaethylporphyrinato)iron(III): a new triclinic polymorph of Fe(OEP)Cl Saifon A. Kohnhorst and Kenneth J. Haller Computing details Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT (Bruker, 2002); data reduction: SAINT (Bruker, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEPIII (Burnett & Johnson, 1996) and ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008) and publCIF (Westrip, 2010). Chlorido(2,3,7,8,12,13,17,18-octaethylporphyrinato)iron(III) Crystal data [Fe(C36H44N4)Cl] Mr = 624.05 Triclinic, P1 Hall symbol: -P 1 a = 10.4495 (3) Å b = 10.7805 (4) Å c = 15.7360 (5) Å α = 71.949 (1)° β = 73.034 (1)° γ = 82.440 (1)° V = 1610.42 (9) Å3
Z=2 F(000) = 662 Dx = 1.287 Mg m−3 Mo Kα radiation, λ = 0.71073 Å Cell parameters from 9866 reflections θ = 2.8–30.6° µ = 0.58 mm−1 T = 100 K Block, dark purple 0.47 × 0.35 × 0.22 mm
Data collection Bruker APEXII CCD area-detector diffractometer Radiation source: fine-focus sealed tube Graphite monochromator φ and ω scans Absorption correction: multi-scan (SADABS; Bruker, 2009) Tmin = 0.772, Tmax = 0.880
34934 measured reflections 9534 independent reflections 7545 reflections with I > 2σ(I) Rint = 0.021 θmax = 30.6°, θmin = 2.0° h = −14→14 k = −15→15 l = −22→22
Refinement Refinement on F2 Least-squares matrix: full R[F2 > 2σ(F2)] = 0.051 wR(F2) = 0.148 S = 1.05 9534 reflections 727 parameters
Acta Cryst. (2014). C70, 368-374
1185 restraints Primary atom site location: structure-invariant direct methods Hydrogen site location: difference Fourier map H-atom parameters constrained w = 1/[σ2(Fo2) + (0.0746P)2 + 0.9291P] where P = (Fo2 + 2Fc2)/3
sup-1
supplementary materials Δρmin = −0.46 e Å−3
(Δ/σ)max = 0.072 Δρmax = 1.03 e Å−3 Special details
Experimental. 1 reflection (0 0 1) was omitted from the data set due to beamstop interference. The default recommendation for scan sets was used. The _diffrn_measured_fraction_theta_full = 96.0% is relatively constant over the entire angular range suggesting the recommendation was not optimal. Probable reasons for the missing data thus include: beamstop interference, nonoptimal data collection strategy, and data truncation losses at resolutions higher than 0.70 Å. The data yield near the limiting 2θ value of 61.26 ° is about 54%. The data/variable ratio is 13.6 and the observed data/variable ratio is 10.7 for 2θmax = 61.26 °. Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two least squares planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving least squares planes. Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2)
Fe1 Cl1 N1 N2 N3 N4 C1 C2 C21 H21A H21B C3 C23 H23A H23B C4 C5 H5 C6 C7 C25 H25A H25B C8 C27 H27A H27B C9 C10 H10 C11 C12
x
y
z
Uiso*/Ueq
Occ. (
Acta Crystallographica Section C
Structural Chemistry ISSN 2053-2296
Chlorido(2,3,7,8,12,13,17,18-octaethylporphyrinato)iron(III): a new triclinic polymorph of Fe(OEP)Cl Saifon A. Kohnhorst* and Kenneth J. Haller* Schools of Chemistry and Biochemistry, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand Correspondence e-mail: [email protected], [email protected] Received 10 January 2014 Accepted 4 March 2014
The previous structure determination of the title compound, [Fe(C36H44N4)Cl], was of a monoclinic polymorph [Senge (2005). Acta Cryst. E61, m399–m400]. The crystal structure of a new triclinic polymorph has been determined based on single-crystal X-ray diffraction data collected at 100 K. The asymmetric unit contains one molecule of the high-spin square-pyramidal iron(III) porphyrinate. The structure exhibits distinct nonstatistical alternative positions for most atoms and was consequently modeled as a whole-molecule disorder. The compound is characterized by an average Fe—N bond ˚ , an Fe—Cl bond length of 2.225 (4) A ˚, length of 2.065 (2) A ˚ and the iron(III) cation displaced by 0.494 (4) A from the plane of the 24-atom porphyrinate core, essentially the same as in the previously determined polymorph. Common features of the porphyrin plane–plane stacking involve two types of synthons, each of which can be further stabilized with additional H Cl interactions to the axial chloride ligand, exhibiting concerted interactions of H atoms from the ethyl groups with the -cloud electron density of adjacent molecules; the shortest methylene H-atom contacts are in the ˚ , resulting in plane–plane separations of range 2.75–2.91 A ˚ , and the shortest methyl H-atom 3.407 (4) and 3.416 (4) A ˚ , resulting in plane–plane separations contacts are 2.56–2.95 A ˚ in the monoclinic polymorph. The of 4.900 (5) and 4.909 (5) A plane-to-plane stacking synthons in the triclinic polymorph are similar, but at greater distances; the shortest methylene H-atom ˚ , resulting in plane–plane separations contacts are 2.86–2.94 A ˚ , and the shortest methyl H-atom of 3.45 (2) and 3.45 (3) A ˚ , resulting in plane–plane separations contacts are 2.89–3.20 A ˚ , consistent with the density of the of 5.081 (13) and 5.134 (13) A triclinic polymorph being 1.5% lower, suggesting lesser packing efficiency and lower stability in the triclinic polymorph. The major molecular differences found in the polymorphs is in three different orientations of the ethyl-group side chains on the periphery of the porphyrin core. Keywords: crystal structure; heme; porphyrin; polymorph; octaethylporphyrin; supramolecular structure; Fe(OEP)Cl.
368
# 2014 International Union of Crystallography
Fe(OEP)Cl, (I), is a convenient starting material to form derivatives of the iron–2,3,7,8,12,13,17,18-octaethylporphyrin macrocycle (OEP) to be used as biomimetic models for heme function (Wyllie & Scheidt, 2002), and also for other studies of iron porphyrin complexes (Senge, 2000), including their recent use, along with other chlorido and oxido derivatives, as models for malaria pigment (Puntharod et al., 2010, 2012, 2014) or as a reference compound (Kalish et al., 2002) for an archetypal high-spin five-coordinate iron(III) porphyrin (Scheidt, 2000). Although (I) was reported in a crystalline form in 1977 (Ernst et al., 1977), the first occurance of Fe(OEP)Cl in the Cambridge Structural Database (CSD, Version 5.32, May 2011; Allen, 2002) was in combination with C60 and chloroform (CSD refcode CELYOH; Olmstead et al., 1999), followed by the report of the monoclinic polymorph (refcode TOYRUU; Senge, 2005) and another multicomponent (methylene chloride solvate) report (refcode QUXFIZ; Safo et al., 2010). We present here the structure of a new triclinic polymorph of Fe(OEP)Cl which appeared serendipitously as a by-product of the frustrated synthesis of an OEP heme complex with a 2,6-dinitrophenoxy axial ligand (see Experimental), and a comparison of the plane-to-plane packing efficiency of the two polymorphs.
2. Experimental 2.1. Synthesis and crystallization
Beautiful dark-purple block-shaped crystals were obtained from the remains of a frustrated attempt to obtain an OEP heme complex with a 2,6-dinitrophenoxy axial ligand. A solution of chlorido(octaethylporphyrinato)iron(III) (1.58 mg, 2.53 mmol; Sigma) and 2,6-dinitrophenol (1.86 mg, 10.1 mmol; Sigma) in dimethylformamide (10 ml) and chloroform (90 ml) was refluxed for 6 h, and allowed to cool and stand at room temperature for 30 d, and finally filtered. The data crystal was selected from the fine crystalline product obtained. 2.2. Refinement
Crystal data, data collection and structure refinement details are summarized in Table 1, and a perspective drawing doi:10.1107/S2053229614005002
Acta Cryst. (2014). C70, 368–374
metal-organic compounds Table 1 Experimental details. Crystal data Chemical formula Mr Crystal system, space group Temperature (K) ˚) a, b, c (A , , ( ) ˚ 3) V (A Z Dx (Mg m 3) Radiation type (mm 1) Crystal size (mm) Data collection Diffractometer Absorption correction Tmin, Tmax No. of measured, independent and observed [I > 2(I)] reflections Rint Refinement R[F 2 > 2(F 2)], wR(F 2), S No. of reflections No. of parameters No. of restraints H-atom treatment ˚ 3) max, min (e A
[Fe(C36H44N4)Cl] 624.05 Triclinic, P1 100 10.4495 (3), 10.7805 (4), 15.7360 (5) 71.949 (1), 73.034 (1), 82.440 (1) 1610.42 (9) 2 1.287 Mo K 0.58 0.47 0.35 0.22
Bruker APEXII CCD area-detector diffractometer Multi-scan (SADABS; Bruker, 2009) 0.772, 0.880 34934, 9534, 7545 0.021
0.051, 0.149, 1.05 9534 727 1185 H-atom parameters constrained 1.03, 0.46
Computer programs: APEX2 (Bruker, 2005), SAINT (Bruker, 2002), SHELXS97 (Sheldrick, 2008), ORTEPIII (Burnett & Johnson, 1996), ORTEP-3 for Windows (Farrugia, 2012), SHELXL97 (Sheldrick, 2008) and publCIF (Westrip, 2010).
of the major occupancy, 0.684 (5), molecule with the labeling scheme indicated thereon is shown in Fig. 1. Intensity data measurements were carried out on a visually well-formed single dark-purple block-shaped crystal of (I)-triclinic at 100 K. The positions for all non-H atoms were located by direct methods and H atoms were added in geometrically sensible positions using the SHELX program system (Sheldrick, 2008) through the shelXle interface tool (Hu¨bschle et al., 2011). Preliminary refinement including anisotropic atomic displacement parameters for the non-H atoms revealed discrepencies in the model. Many bond distances and angles
were not reasonable, most of the core atoms exhibited atomic displacement parameters oriented out of the porphyrinate plane, and the highest peaks in the difference electron-density Fourier map were in the region near atoms C7, C8, and C27, indicating disorder. The major peaks were at rational separations for disorder of the pyrrole C atoms and the attached ethyl groups of the pyrrole ring containing atom N2. This initial disorder was incorporated into the model with identical distance and angle geometry constraints (later relaxed to restraints) imposed on the overlapping planar parts of the porphyrinate ligand and including occupancy variables for the two parts constrained to sum to unity (atom labels of the major-occupancy atoms were used for the corresponding minor-occupancy atoms but with a letter ‘m’ appended to the label). A series of least-squares refinement/difference electron-density Fourier-map calculations indicated more disordered positions of lesser magnitude, suggesting alternative positions in all areas of the porphyrinate ligand and for the axial Cl ligand. The minor positions were modeled as a second set of atomic positions for the entire molecule, with corresponding distances and angles restrained to be similar between the overlapping planes of the two partial molecules. Positional parameters were further controlled by additional restraints introduced to keep the C —Cmethylene and Cmethylene—Cmethyl distances similar, to impose planarity at C12, and to control the coplanarity of the individual pyrrole rings. H atoms were included in geometrically idealized riding ˚ ) and methylene positions for the methine (C—H = 0.95 A ˚ (C—H = 0.99 A) positions, and as idealized rigid rotating ˚ ), each with tetrahedral angles, for groups (C3v; C—H = 0.98 A the methyl H-atom positions. This highly restrained refinement of the whole-molecule disorder had 727 parameters (compared to 459 parameters for the corresponding ordered single-molecule model) and 1185 restraints. The structure was refined against all data using SHELXL97 (Sheldrick, 2008). The methyl H atoms for both the major- and the minoroccupancy partial molecules were relocated by difference electron-density ring Fourier calculations before the final cycles of refinement, demonstrating that the appropriate maxima for both the major and the minor partial H atoms were present. Anisotropic displacement parameters for the non-H atoms as described above and isotropic displacement parameters for the H atoms, maintained at Uiso(H) = 1.5Ueq(C) for methyl H atoms or at 1.2Ueq(C) otherwise, were utilized in the final cycles of least-squares refinement.
3. Results and discussion
Figure 1 Perspective drawing of the major-occupancy molecule of (I)-triclinic, showing the atomic labeling scheme. The corresponding atoms of the minor-occupancy molecule are labeled with a small letter m appended to the respective label. Atomic displacement parameters for the non-H atoms are drawn as 50% probability ellipsoids. Acta Cryst. (2014). C70, 368–374
The structure of the new triclinic polymorph of Fe(OEP)Cl is characterized by five-coordinate iron, with an average Fe—N ˚ , an Fe—Cl bond length of bond length of 2.065 (2) A ˚ ˚ 2.225 (4) A, and the iron(III) cation displaced by 0.494 (4) A from the plane of the 24-atom porphyrinate core, essentially the same as in the previously determined structures of (I) [summarized as the key characteristics of (I); see table in Supporting information]. The relative positioning of the major- and minor-occupancy molecules within the asymmetric Kohnhorst and Haller
[Fe(C36H44N4)Cl]
369
metal-organic compounds
Figure 2 Perspective drawing showing the overlap of the major- [0.684 (5)] and minor-occupancy [0.316 (5)] molecules of the whole-molecule disorder model. The major difference between the two partial molecules is the positioning of the C27/C28 ethyl group of the major-occupancy molecule to the opposite side of the porphyrinate plane as the axial chloride ligand, while the C27m/C28m ethyl group of the minor-occupancy molecule is to the same side of the porphyrinate plane as the axial chloride ligand. The bonds of the major-occupancy molecule are represented as solid lines and the bonds of the minor-occupancy molecule are represented as open lines. The atoms of the major-occupancy molecule are represented as eighthcutout spheres and the atoms of the minor-occupancy molecule are represented as open spheres, both of arbitrary radius, for clarity.
unit can be seen in a perspective drawing of the total content of the asymmetric unit (Fig. 2). The intersection of the porphyrin cores, visible in Fig. 2, allows them to occupy the same approximate space in the lattice. The larger apparent core separation can be seen on the left side of the illustration [interplanar angle between the least-squares planes through the 24-atom cores = 3.9 (3) ], with a maximum apparent ˚. separation of the core-plane atoms at C27 C27m = 0.83 A The absolute maximum apparent separation of major–minor ˚ , where the methyl atoms occurs at C28 C28m = 1.77 A group occupies opposite sides of the porphyrin plane. The striking molecular difference between the two partial molecules in the lattice is a difference in the orientations of the ethyl side chains on the periphery of the porphyrin core. With the axial chloride ligand pointing ‘up’ as a reference, the major-occupancy molecule, denoted (I)-triclinic-major, has
four adjacent ethyl groups up and four down, while the minoroccupancy molecule, denoted (I)-triclinic-minor, has five adjacent ethyl groups up and three down, as shown in the stick diagrams for the known structurally determined forms of (I) illustrated in Fig. 3. The monoclinic (Fig. 3c) polymorph, denoted (I)-monoclinic, has three ethyl groups up and five down, while both multicomponent crystals (Figs. 3d and 3e) have all eight ethyl groups down, and a closely related complex, the analogous FeIII(OEP--cation radical)Cl cationic complex (refcode JOVRIV; Scheidt et al., 1992), forms a tight face-to-face dimer with all eight ethyl groups up (Fig. 3f). The cell parameters of the (I)-monoclinic polymorph were redetermined at 100 (2) K [a = 15.0003 (8), b = 22.1238 (12), ˚ , = 106.198 (3) , V = 3172.6 (3) A ˚ 3 and dcalc = c = 9.9552 (6) A 3 1.307 Mg m ] for comparison with the (I)-triclinic polymorph. The normalized molecular volumes of the two poly˚ 3 for the (I)-monoclinic form morphic forms at 100 K [793.2 A 3 ˚ compared to 805.2 A for the (I)-triclinic form] shows the packing of the new triclinic form to be less favorable; the volume is 1.52% greater for the same composition, implying greater stability for the (I)-monoclinic polymorph. The ˚ 3 for (I)-monoclinic normalized molecular volume of 798.5 A at the previous structure determination temperature (Senge, 2005) demonstrates a volume increase of 0.67% for the 26 K higher temperature (thus, less than 1% relative volume change for the structures discussed herein). A partial packing diagram for (I)-monoclinic showing the adjacent molecules that directly contact the porphyrin core is given in Fig. 4. The packing is dominated by four modified – stacking motifs, each exhibiting concerted weak supramolecular interactions. Previous discussion of – contacts by the authors has long involved contacts between -cloud electron density on adjacent delocalized fragments where the non-H atoms being considered are sp2-hybridized (Haller & Enemark, 1978). Senge’s report (Senge, 2005) that (I)-monoclinic has very weak – aggregates of the aromatic systems ˚ , more akin to with a mean plane separation of 4.02 (1) A methyl–methyl contacts (Pauling, 1960) than aromatic– aromatic contacts, piqued our curiosity to examine these
Figure 3 Comparison of the various Fe(OEP)Cl side-group orientations found to date: (a) (I)-monoclinic, (b) (I)-triclinic-major, (c) (I)-triclinic-minor, (d) (I)CH2Cl2, (e) (I)C60CHCl3 and (f) Fe(OEP--cation radical)Cl.
370
Kohnhorst and Haller
[Fe(C36H44N4)Cl]
Acta Cryst. (2014). C70, 368–374
metal-organic compounds
Figure 5 Figure 4 Projection drawings showing the – stackings in the (I)-monoclinic lattice: (a) viewed parallel to the porphyrin planes of (I), showing the four packing/stacking interactions to the porphyrin planes; (b) viewed perpendicular to the porphyrin plane of (I), showing adjacent parallel molecules with CH2 plane contacts; (c) viewed perpendicular to the porphyrin plane of (I), showing adjacent parallel molecules with Me plane contacts. Atoms are represented by spheres of arbitrary radii. Acta Cryst. (2014). C70, 368–374
Projection drawings showing the – stackings in the (I)-triclinic lattice: (a) viewed parallel to the porphyrin planes of (I), showing the six packing/ stacking interactions to the porphyrin planes; (b) viewed perpendicular to the porphyrin plane of (I), showing adjacent parallel molecules with CH2 plane contacts; (c) viewed perpendicular to the porphyrin plane of (I), showing adjacent parallel molecules with Me plane contacts. Atoms are represented by spheres of arbitrary radii. Only the major positions of the atoms are shown. Kohnhorst and Haller
[Fe(C36H44N4)Cl]
371
metal-organic compounds
Figure 6 Projection drawings showing the – stackings in the (I)CH2Cl2 lattice: (a) viewed parallel to the porphyrin planes of (I), showing the five packing/ stacking interactions to the porphyrin planes; (b) viewed perpendicular to the porphyrin plane of (I), showing adjacent parallel molecules with CH2 plane contacts; (c) viewed perpendicular to the porphyrin plane of (I), showing adjacent parallel molecules with Me plane contacts. Atoms are represented by spheres of arbitrary radii.
contacts more closely. We cannot find the reported porphyrin ˚ . In fact, the planar plane-to-plane contact distance of 4.02 A systems in OEP consist of the 24-atom porphyrin core plus the eight methylene C atoms of the ethyl groups. In the polymorphic structures under consideration here, methylene H atoms can be seen to be between the planes of the interacting rings [as in Fig. 4(a) for (I)-monoclinic]. This leads to – ˚ on the chloride side of the contact distances of 3.407 (4) A ˚ porphyrin core (Fig. 4a, upper-left quadrant) and 3.416 (4) A on the opposite side (Fig. 4a, lower-right quadrant) for (I)monoclinic, similar to Pauling’s aromatic – contact estimate ˚ half-thickness of an aromatic ring (Pauling, 1960; of 1.7 A Haller et al., 1979). The corresponding methylene H interactions (perpendicular distance from the H atom to the best porphyrin 24-atom least-squares plane) range between ˚ . Furthermore, the remaining plane– 2.75 (3) and 2.89 (4) A plane interactions show a second type of aliphatic H atom-toporphyrin plane interaction at similar H distances invol-
372
Kohnhorst and Haller
[Fe(C36H44N4)Cl]
ving methyl H atoms (vide infra). The lower-left quadrant of Fig. 4(c) shows an ideal stacking/packing interaction opposite the chloride ligand, across the inversion center at (12, 0, 0), involving eight ethyl groups in an interlocking arrangement between two adjacent molecules. The shortest methyl H interactions from the central four ethyl groups in contact with ˚ and the inversion-related planes are in the range 2.90–2.96 A ˚ the plane–plane distance is 4.909 (5) A. The upper-right quadrant contains a similar methyl-to-porphyrin plane stacking/packing interaction, across the inversion center at (1, 0, 12), involving only six ethyl groups (a consequence of only three ethyl groups on the chloride side of the molecule) and placing a single methyl group in contact with the face of the corresponding pyrrole ring, but also including C—H Cl ˚ and support, with shortest methyl H interactions of 2.82 A ˚ . Much of the additional a plane–plane distance of 4.900 (5) A plane–plane separation of these contacts results from the distances of the methyl C atoms to the porphyrin plane. Acta Cryst. (2014). C70, 368–374
metal-organic compounds interactions, one nearly ideal involving four concerted methyl–plane contacts and the other involving two concerted methyl–plane contacts, as discussed above. (I)-Triclinic-major does not exhibit the ideal highly concerted interaction, but instead contains four of the two concerted methyl–plane contacts (Fig. 5c), all of which occur across inversion centers and provide porphyrin plane–plane contact distances of ˚ on both the top and the bottom 5.081 (13) and 5.134 (14) A sides of the porphyrin plane, compared with the shorter ˚ in (I)-monoclinic. The contacts of 4.900 (5) and 4.910 (5) A average ruffling of the porphyrin cores is the same [ = ˚ for (I)-monoclinic (Senge, 2005) and = 0.043 A ˚ for 0.045 A (I)-triclinic]. Thus, the core conformation is unlikely to contribute to the observed density differences. The plane-to-
Figure 7 Projection drawings showing the two equivalent CH2 plane – stacking/packing contacts on the chloride side of the porphyrin plane in the C60(I)CH2Cl2 lattice: (a) viewed parallel to the porphyrin planes of (I); (b) viewed perpendicular to the porphyrin planes of (I). Atoms are represented by spheres of arbitrary radii.
The packings of the two polymorphic forms have a common edge-to-edge contact feature between adjacent parallel porphyrin cores, as illustrated by the left halfs of the perpendicular views in Figs. 4(b) and 5(b). This compact region contains the complete plane-to-plane edge contact extending from one methylene group to the fourth methylene group around the porphyrin core (nine C atoms). The second and third methylene group H atoms contact the adjacent porphyrin core plane in an efficient plane-to-plane stacking motif mediated by extensive – and H contacts, further supported by four C—H Cl contacts in two R12 (10) motifs (Etter et al., 1990), combined to make the arguably most stable supramolecular interaction represented within the lattice; the closest methylene C—H interactions range from 2.86 to ˚ , and the methylene C—H Cl interactions are at 2.85 2.94 A ˚ . The resulting perpendicular distance between the and 3.10 A ˚ in (I)-triclinic-major, and similar porphyrin cores is 3.45 (2) A ˚ where but somewhat shorter in (I)-monoclinic at 3.407 (4) A ˚. the methylene C—H Cl interactions are at 2.86 and 2.97 A A weaker methylene–plane contact extending approximately six C atoms along the opposite edge also occurs in each of the polymorphs on the bottom side of the porphyrin plane (Figs. 4b and 5b), with closest methylene C—H interactions ˚ and the perpendicular distance ranging from 2.89 to 3.20 A ˚ in (I)-triclinicbetween the porphyrin cores at 3.45 (3) A major; again, this value is similar but slightly shorter in (I)˚ . Thus, the monoclinic polymorph monoclinic at 3.416 (4) A ˚ has on average 0.036 A or 1.05% tighter methylene plane– plane contacts than the triclinic polymorph. A second common feature in the packings of the two polymorphs is similar corner-to-corner interactions involving methyl H contacts. (I)-Monoclinic contains two of these Acta Cryst. (2014). C70, 368–374
Figure 8 Projection drawings showing the – stackings in the Fe(OEP--cation radical)Cl lattice: (a) viewed parallel to the porphyrin planes, showing the four packing/stacking interactions to the porphyrin planes (the lower interaction is the tight face-to-face dimer interaction; Scheidt et al., 1992); (b) viewed perpendicular to the porphyrin plane, showing adjacent parallel molecules with Me plane contacts. Atoms are represented by spheres of arbitrary radii. Kohnhorst and Haller
[Fe(C36H44N4)Cl]
373
metal-organic compounds plane contacts are all shorter for the (I)-monoclinic polymorph, viz. 1.05% (2–3) for the methylene C—H and ˚ or 4.05% (10–20) for the methyl C—H contacts. 0.202 A The average difference in the spacings, at 2.55% in favor of the previously reported monoclinic form, is significantly greater than the 1.52% change in density, but nonetheless supports greater stability for the monoclinic polymorph. The other existing Fe(OEP)Cl structures both exhibit all eight ethyl groups on the opposite side of the porphyrin plane relative to the Fe and Cl atoms. The more highly concerted R12 (10) supramolecular motifs observed in (I)-monoclinic and (I)-triclinic also occur in these structures. The compact complete 9-C edge–edge methylene–plane synthon, including the four C—H Cl interactions, occurs once in the structure of the methyene chloride solvate (Safo et al., 2010), as shown in the projection diagram viewed perpendicular to the porphyrin core in Fig. 6(b), and twice in the methylene chloride solvated (I)C60 cocrystal structure (Olmstead et al., 1999), as shown in the projection diagram viewed perpendicular to the porphyrin core in Fig. 7(b). These are the only porphyrin plane–plane interactions in the (I)C60 cocrystal structure since the eight ethyl groups embrace the C60 molecule, completely filling the space opposite the chloride ligand and giving shortest – fullerene-to-N4 plane contacts of ˚ (Olmstead et al., 1999). 2.748 A The nearly perfect concerted four methyl–plane-type interaction found in (I)-monoclinic occurs twice in (I)CH2Cl2, completely covering the aliphatic side of the porphyrin plane, as shown in Fig. 6(c). The remainder of the porphyrin plane– plane contacts in (I)CH2Cl2 are a third type of methylene– plane contact, i.e. corner–corner-type contacts involving only one methylene group per molecule in contact with the face of pyrrole rings, as can be seen on the right-hand side of Fig. 6(b). The common nature of the supramolecular contacts in all occurrences of (I) to date is reflected in the shortest Fe Fe contact distance [see table of key characteristics of (I) in the ˚ in (I)Supporting information], which range from 7.896 A ˚ monoclinic to 8.079 A in (I)CH2Cl2. The pronounced lateral shifts place all of these occurrences of (I) in Group W (Scheidt, 2000). The closely related analogous FeIII(OEP--cation radical)Cl cationic complex (Scheidt et al., 1992) forms a tight ˚ ; lower face-to-face dimer (plane–plane distance of 3.24 A portion of Fig. 8a), with all eight ethyl groups required to be on the chloride side of the porphyrin plane. The aliphatic side
374
Kohnhorst and Haller
[Fe(C36H44N4)Cl]
of the complex exhibits two of the two concerted methyl– plane contacts found in both polymorphs (right-hand side, Fig. 8b) and a new full edge–edge contact (left-hand side, Fig. 8b) analogous to the methylene – contact. This investigation was supported by the Thai Commission on Higher Education with a PhD study grant (No. CHE-PHDTH-2550) to SAK. Supporting information for this paper is available from the IUCr electronic archives (Reference: SF3221).
References Allen, F. H. (2002). Acta Cryst. B58, 380–388. Bruker (2002). SAINT. Bruker AXS Inc., Madison, Wisconsin, USA. Bruker (2005). APEX2. Bruker AXS Inc., Madison, Wisconsin, USA. Bruker (2009). SADABS. Bruker AXS Inc., Madison, Wisconsin, USA. Burnett, M. N. & Johnson, C. K. (1996). ORTEPIII. Report ORNL-6895. Oak Ridge National Laboratory, Tennessee, USA. Ernst, J., Subramanian, J. & Fuhrhop, J.-H. (1977). Z. Naturforsch. Teil A Phys. Sci. 32, 1129–1136. Etter, M. C., MacDonald, J. C. & Bernstein, J. (1990). Acta Cryst. B46, 256– 262. Farrugia, L. J. (2012). J. Appl. Cryst. 45, 849–854. Haller, K. J. & Enemark, J. H. (1978). Acta Cryst. B34, 102–109. Haller, K. J., Johnson, P. L., Feltham, R. D., Enemark, J. H., Ferraro, J. R. & Basile, L. J. (1979). Inorg. Chim. Acta, 33, 119–130. Hu¨bschle, C. B., Sheldrick, G. M. & Dittrich, B. (2011). J. Appl. Cryst. 44, 1281– 1284. Kalish, H., Camp, J. E., Stepien, M., Latos-Grazynski, L., Olmstead, M. M. & Balch, A. L. (2002). Inorg. Chem. 41, 989–997. Olmstead, M. M., Costa, D. A., Maitra, K., Noll, B. C., Phillips, S. L., Van Calcar, P. M. & Balch, A. L. (1999). J. Am. Chem. Soc. 121, 7090–7097. Pauling, L. (1960). The Nature of the Chemical Bond, 3rd ed., p. 260. Ithaca: Cornell University Press. Puntharod, R., Haller, K. J., Robertson, E. & Wood, B. R. (2014). J. Raman Spectrosc. In preparation. Puntharod, R., Webster, G. T., Asghari-Khiavi, M., Bambery, K. R., Safinejad, F., Rivadehi, S., Langford, S. J., Haller, K. J. & Wood, B. R. (2010). J. Phys. Chem. B, 114, 12104–12115. Puntharod, R., Wood, B. R. & Haller, K. J. (2012). Adv. Mater. Res. 506, 222– 225. Safo, M. K., Buentello, K. E., Oliver, A. G. & Scheidt, W. R. (2010). Acta Cryst. E66, m733. Scheidt, W. R. (2000). The Porphyrin Handbook, Vol. 6, edited by K. M. Kadish, R. Guilard & K. M. Smith, pp. 49–112. San Diego: Academic Press. Scheidt, W. R., Song, H., Haller, K. J., Safo, M. K., Orosz, R. D., Reed, C. A., Debrunner, P. G. & Schulz, C. E. (1992). Inorg. Chem. 31, 941–944. Senge, M. O. (2000). The Porphyrin Handbook, Vol. 10, edited by K. M. Kadish, R. Guilard & K. M. Smith, pp. 1–218. San Diego: Academic Press. Senge, M. O. (2005). Acta Cryst. E61, m399–m400. Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Westrip, S. P. (2010). J. Appl. Cryst. 43, 920–925. Wyllie, G. R. A. & Scheidt, W. R. (2002). Chem. Rev. 102, 1067–1089.
Acta Cryst. (2014). C70, 368–374
supplementary materials
supplementary materials Acta Cryst. (2014). C70, 368-374
[doi:10.1107/S2053229614005002]
Chlorido(2,3,7,8,12,13,17,18-octaethylporphyrinato)iron(III): a new triclinic polymorph of Fe(OEP)Cl Saifon A. Kohnhorst and Kenneth J. Haller Computing details Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT (Bruker, 2002); data reduction: SAINT (Bruker, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEPIII (Burnett & Johnson, 1996) and ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008) and publCIF (Westrip, 2010). Chlorido(2,3,7,8,12,13,17,18-octaethylporphyrinato)iron(III) Crystal data [Fe(C36H44N4)Cl] Mr = 624.05 Triclinic, P1 Hall symbol: -P 1 a = 10.4495 (3) Å b = 10.7805 (4) Å c = 15.7360 (5) Å α = 71.949 (1)° β = 73.034 (1)° γ = 82.440 (1)° V = 1610.42 (9) Å3
Z=2 F(000) = 662 Dx = 1.287 Mg m−3 Mo Kα radiation, λ = 0.71073 Å Cell parameters from 9866 reflections θ = 2.8–30.6° µ = 0.58 mm−1 T = 100 K Block, dark purple 0.47 × 0.35 × 0.22 mm
Data collection Bruker APEXII CCD area-detector diffractometer Radiation source: fine-focus sealed tube Graphite monochromator φ and ω scans Absorption correction: multi-scan (SADABS; Bruker, 2009) Tmin = 0.772, Tmax = 0.880
34934 measured reflections 9534 independent reflections 7545 reflections with I > 2σ(I) Rint = 0.021 θmax = 30.6°, θmin = 2.0° h = −14→14 k = −15→15 l = −22→22
Refinement Refinement on F2 Least-squares matrix: full R[F2 > 2σ(F2)] = 0.051 wR(F2) = 0.148 S = 1.05 9534 reflections 727 parameters
Acta Cryst. (2014). C70, 368-374
1185 restraints Primary atom site location: structure-invariant direct methods Hydrogen site location: difference Fourier map H-atom parameters constrained w = 1/[σ2(Fo2) + (0.0746P)2 + 0.9291P] where P = (Fo2 + 2Fc2)/3
sup-1
supplementary materials Δρmin = −0.46 e Å−3
(Δ/σ)max = 0.072 Δρmax = 1.03 e Å−3 Special details
Experimental. 1 reflection (0 0 1) was omitted from the data set due to beamstop interference. The default recommendation for scan sets was used. The _diffrn_measured_fraction_theta_full = 96.0% is relatively constant over the entire angular range suggesting the recommendation was not optimal. Probable reasons for the missing data thus include: beamstop interference, nonoptimal data collection strategy, and data truncation losses at resolutions higher than 0.70 Å. The data yield near the limiting 2θ value of 61.26 ° is about 54%. The data/variable ratio is 13.6 and the observed data/variable ratio is 10.7 for 2θmax = 61.26 °. Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two least squares planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving least squares planes. Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2)
Fe1 Cl1 N1 N2 N3 N4 C1 C2 C21 H21A H21B C3 C23 H23A H23B C4 C5 H5 C6 C7 C25 H25A H25B C8 C27 H27A H27B C9 C10 H10 C11 C12
x
y
z
Uiso*/Ueq
Occ. (
