Received 31 March 2010
Bis(hinokitiolato)copper(II): modification (III)
Bis(hinokitiolato)copper(II), Cu(hino)2, exhibits both antibacterial and antiviral properties, and has been previously shown to exist in two modifications. A third modification has now been confirmed, namely tetrakis(2-3-isopropyl-7-oxocyclohepta-1,3,5-trien-1-olato)bis(3-isopropyl-7-oxocyclohepta-1,3,5-trien-1-olato)tricopper(II)-bis(2-3-isopropyl-7-oxocyclohepta-1,3,5-trien-1-olato)bis[(3-isopropyl-7-oxocyclohepta-1,3,5-trien-1-olato)copper(II)] (1/1), [Cu(C10H11O2)2]3·[Cu(C10H11O2)2]2, where 3-isopropyl-7-oxocyclohepta-1,3,5-trien-1-olate is the systematic name for the hinokitiolate anion. This new modification is composed of discrete [cis-Cu(hino)2]2[trans-Cu(hino)2] trimers and [cis-Cu(hino)2]2 dimers. The Cu atoms are bridged by 2-O atoms from the hinokitiolate ligands to give distorted square-pyramidal and distorted octahedral CuII coordination environments. Hence, the CuII environments are CuO5/CuO6/CuO5 for the trimer and CuO5/CuO5 for the dimer. Each trimer and dimer has crystallographically imposed inversion symmetry. The trimer has never been observed before, the dimer has been seen only once before, and the combination of the two together in the same lattice is unprecedented. The CuO5 cores exhibit four strong basal Cu-O bonds [1.915 (2)-1.931 (2) Å] and one weak apical Cu-O bond [2.652 (2)-2.658 (2) Å]. The CuO6 core exhibits four strong equatorial Cu-O bonds [1.922 (2)-1.929 (2) Å] and two very weak axial Cu-O bonds [2.911 (3) Å]. The bite angles for the chelating hinokitiolate ligands range from 83.13 (11) to 83.90 (10)°.
Hinokitiol (-thujaplicin) and metal complexes of the hinokitiolate anion have been known for 74 years (Nozoe, 1936). The former is a natural product and of interest for its broad range of biological activities, e.g. antitumor, antibacterial, antifungal and insecticidal properties (Inamori et al., 1993, 2000; Arima et al., 2003; Morita et al., 2003), while the latter metal complexes exhibit antiviral and antimicrobial properties (Miyamoto et al., 1998; Nomiya et al., 2009). Among these compounds, the Cu complex reported by Nozoe in 1936 is arguably the most structurally intriguing. In 2002, initial insights into the `unusual structural chemistry of CuII hinokitiol' [also referred to as bis(hinokitiolato)copper(II) or Cu(hino)2] were provided by Molloy and co-workers, who found that Cu(hino)2 could be crystallized in two modifications (Barret et al., 2002). Modification (I) turned out to be monomeric trans-Cu(hino)2, while modification (II) is composed of monomers and dimers, i.e. [cis-Cu(hino)2]2·[trans-Cu(hino)2]2·trans-Cu(hino)2. Subsequent studies have further revealed that (I) is polymorphic (Barret et al., 2002; Nomiya et al., 2004; Arvanitis et al., 2004; Ho et al., 2009). A third modification, (III), has now been discovered and is reported here. This new modification is composed of dimers and trimers, i.e. [cis-Cu(hino)2]2[trans-Cu(hino)2]·[cis-Cu(hino)2]2. Views of the trimer and dimer are given in Figs. 1 and 2, respectively, and selected bond distances and bond valences are summarized in Table 1.
Trimeric CuII hinokitiol has never been observed before and therefore constitutes the most notable feature of this study. As shown in Fig. 1, the trimer consists of a single planar trans-Cu(hino)2 moiety sandwiched between two visibly twisted cis-Cu(hino)2 moieties. Atom Cu1 is situated at Wyckoff position 1h [space group P (No. 2)], requiring that the trimer possess crystallographic inversion symmetry. Atoms Cu1, O1, O2, O1i and O2i are also required by symmetry to be exactly coplanar [symmetry code: (i) -x + 1, -y + 1, -z + 1]. In contrast, atoms Cu2/O3-O6 in the nonplanar cis moieties exhibit displacements of -0.109 (1), 0.168 (1), -0.111 (1), -0.114 (1) and 0.166 (1) Å, respectively, from the least-squares plane defined by those atoms. The end-to-end distances for the Cu(hino)2 moieties (excluding the isopropyl groups) are 11.358 (7) and 11.274 (6) Å for C4C4i and C14C24, respectively. The shortening of the C14C24 distance is consistent with the cis moieties being slightly bowed in addition to being twisted. Four of the six hinokitiolate ligands participate in asymmetric 2-O bridges to yield the final trimeric structure, with atom Cu1 having a distorted octahedral CuO6 coordination geometry and atom Cu2 having a distorted CuO5 square-pyramidal coordination environment. The twisting and bowing of the cis moieties help to facilitate the bridge bonding, and to alleviate steric repulsions between the C21-C27 and C21i-C27i cycloheptatriene rings and atoms H8 and H8i of the central trans moiety, respectively.
The dimeric CuII hinokitiol component in (III), while less novel than the cis,trans,cis trimer, is nevertheless also unusual, having been observed only once before, i.e. in modification (II). The cis,cis dimers in (II) and (III) are quite synonymous, but the Cu atoms in both dimers are probably better described as five-coordinate with square-pyramidal environments, rather than `four-coordinate and in a square-planar environment' (Barret et al., 2002). In both (II) and (III), the cis,cis dimers possess crystallographically imposed inversion symmetry. For (III), the dimer is centered on Wyckoff position 1a, i.e. the mid-point between atoms Cu3 and Cu3ii in Fig. 2 [symmetry code: (ii) -x, -y, -z + 2]. Atom Cu3 is 0.105 (1) Å above the least-squares plane defined by atoms O7-O10 and displaced towards atom O9ii. The C34C44 end-to-end distance is 11.166 (6) Å, indicating that the cis moieties in the dimer are even more bowed than those in the trimer. In contrast, atom Cu1 in (II) is coplanar with atoms O1-O4. The displacements from the least-squares plane defined by these five atoms are -0.103 (1), -0.088 (2), 0.145 (2), 0.141 (2) and -0.095 (2) Å, respectively. The cis moieties in (II) are, however, also bowed, with the C5C15 end-to-end distance being 11.176 (5) Å. These observations are more consistent with CuO5 cores and covalent bonding, rather than CuO4 cores and a fifth axial intermolecular interaction.
A bond-valence analysis (Brown, 2002, 2009) of the CuOx bonding in the cis,trans,cis trimer and cis,cis dimer is given in Table 1. The CuO6 values in (III) are compared with those for bis(tropolonato)copper(II), Cu(trop)2, which is most often viewed as a square-planar CuO4 monomer (Robertson, 1951; Macintyre et al., 1966; Berg et al., 1978). The latter view has, however, been challenged by a subsequent claim that Cu(trop)2 `exists as a sandwich-type dimer' (Hasegawa et al., 1997); a claim reiterated in a recent review article (Vigato et al., 2009). Suffice to say that it is crystallographically impossible for discrete dimers to exist in that 1997 determination. Cu(trop)2 is either a solid-state monomer or, as entertained below, possibly a solid-state polymer with CuO6 bonding. Finally, the CuO5 values for (III) are compared with those for (II). For completeness, the trans,trans dimer values for (II) are also provided.
The CuO6 equatorial bonds in the trans moiety of the trimer are in the range 1.922 (2)-1.929 (2) Å and are noticably longer than the range of 1.900 (2)-1.918 (2) Å observed in the trans-Cu(hino)2 monomer, (I). This lengthening of the Cu-O bonds is consistent with oligomerization; the Cu-O bonds in the trans,trans dimer in (II) also experience a similar lengthening [1.915 (2)-1.939 (2) Å]. The CuO6 axial bonds in (III) are long at 2.911 (3) Å, while those in Cu(trop)2 are even longer at 3.144 (2) Å. The comparable literature values for CuO6 equatorial and axial bonds are 1.908 (2)-1.948 (6) and 2.797 (2)-2.948 (2) Å, respectively (Table 2). The CuO6 average bond valence, bond-valence sum, s/s' and distortion index R are 0.355, 2.128, 0.101-1.462 and 0.191, respectively, for (III), and 0.358, 2.150, 0.053-1.475 and 0.266, respectively, for Cu(trop)2, while the literature s/s' and R values are 0.07-1.50 and 0.048-0.146, respectively, for Jahn-Teller-distorted CuO6 octahedra (Brown, 2006). All of the numerical values for (III) are in excellent agreement with the presence of a Jahn-Teller-elongated CuO6 octahedron. Cu(trop)2, on the other hand, is at or beyond the limits of such a description. While axial bonds beyond 3 Å do potentially exist (see Table 2), Cu(trop)2 is probably better described as a square-planar CuO4 monomer.
The CuO5 basal bonds in the cis moieties in both the trimer and dimer in (III) are in the range 1.915 (3)-1.931 (3) Å and are comparable with the range of 1.919 (2)-1.933 (2) Å observed in the cis,cis dimer in (II). The CuO5 apical bonds in (III) are 2.658 (3) and 2.652 (3) Å for the trimer and dimer, respectively, but only 2.476 (2) Å in the cis,cis dimer in (II). The comparable literature values for CuO5 basal and apical bonds are 1.898 (3)-1.962 (3) and 2.392 (3)-2.878 (3) Å, respectively (Table 2). The CuO5 average bond valence, bond-valence sum, s/s' and distortion index R are 0.429, 2.157, 0.167-1.226 and 0.077, respectively, for (III), and 0.431, 2.154, 0.267-1.205 and 0.048, respectively, for (II). All of these values are in excellent agreement with the cis moieties in (III) having distorted CuO5 square-pyramidal coordination geometries.
The trimers form hydrogen-bonded ribbons in the solid state via the two interactions C5-H5O5iii [C5-H5 = 0.95 Å, H5O5iii = 2.40 Å, C5O5iii = 3.328 (4) Å and C5-H5O5iii = 165°; symmetry code: (iii) -x, -y + 1, -z + 1] and C6-H6O3iii [C6-H6 = 0.95 Å, H6O3iii = 2.43 Å, C6O3iii = 3.302 (4) Å and C6-H6O3iii = 153°]. Chains of dimers are present, but there are no dimer-dimer hydrogen-bonding, - stacking or Cu interactions involved. The closest dimer-dimer contact is Cu3C34iv = 3.399 (4) Å [symmetry code: (iv) -x + 1, -y, -z + 2]. Finally, the ribbons of trimers and chains of dimers are linked via the two interactions C24-H24O8v [C24-H24 = 0.95 Å, H24O8v = 2.52 Å, C24O8v = 3.446 (5) Å and C24-H24O8v = 164°; symmetry code: (v) x, y + 1, z] and C45-H45O3 [C45-H45 = 0.95 Å, H45O3 = 2.58 Å, C45O3 = 3.397 (5) Å, and C45-H45O3 = 145°].
In summary, structural details have been presented for a third modification of the bioactive substance CuII hinokitiol. This new modification, (III), is [cis-Cu(hino)2]2[trans-Cu(hino)2]·[cis-Cu(hino)2]2, containing a previously undocumented cis,trans,cis trimer. The results from a bond-valence analysis are consistent with the central CuII atom having a Jahn-Teller-distorted octahedral environment. The `unusual structural chemistry of CuII hinokitiol' now encompasses six crystalline forms, i.e. modification (I) with four forms, (II) with one form and (III) with one form. The trans:cis ratios are 1:0, 3:2 and 1:4 for modifications (I)-(III), respectively, making (III) the most cis-enriched modification so far uncovered.
| || Figure 1 |
The cis,trans,cis trimer in modification (III). Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii. [Symmetry code: (i) -x + 1, -y + 1, -z + 1.]
| || Figure 2 |
The cis,cis dimer in modification (III). Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii. [Symmetry code: (ii) -x, -y, -z + 2.]
+The published value of 2.242 (3) Å is a literature error.
All H atoms were allowed to ride on their respective C atoms, with C-H = 0.95, 1.00 and 0.98 Å for the cycloheptatriene, methine and methyl H atoms, respectively, and with Uiso(H) = 1.2Ueq(C) for the cycloheptatriene and methine H atoms or 1.5Ueq(C) for the methyl H atoms. Bond-valence parameters for Cu and O were taken from bvparm2009.cif and the calculations made with the bond-valence calculator Valence 2.0 distributed by Brown (http://www.ccp14.ac.uk/ccp/web-mirrors/i_d_brown ).
Data collection: COLLECT (Nonius, 1998); cell refinement: DENZO and SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO and SCALEPACK; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: ORTEP-3 (Version 2.02; Farrugia, 1997); software used to prepare material for publication: SHELXTL.
Supplementary data for this paper are available from the IUCr electronic archives (Reference: EG3045 ). Services for accessing these data are described at the back of the journal.
The author extends sincere thanks to Dr Susan K. Byram (Bruker AXS) for software support and Dr Judith C. Gallucci (The Ohio State University) for helpful discussions.
Ambrosi, G., Formica, M., Fusi, V., Giorgi, L., Guerri, A., Lucarini, S., Micheloni, M., Paoli, P., Rossi, P. & Zappia, G. (2005). Inorg. Chem. 44, 3249-3260.
Arima, Y., Nakai, Y., Hayakawa, R. & Nishino, T. (2003). J. Antimicrob. Chemother. 51, 113-122.
Arvanitis, G. M., Berardini, M. E. & Ho, D. M. (2004). Acta Cryst. C60, m126-m128.
Barret, M. C., Mahon, M. F., Molloy, K. C., Wright, P. & Creeth, J. E. (2002). Polyhedron, 21, 1761-1766.
Bencini, A., Dei, A., Sangregorio, C., Totti, F. & Vaz, M. G. F. (2003). Inorg. Chem. 42, 8065-8071.
Berg, J.-E., Pilotti, A.-M., Söderholm, A.-C. & Karlsson, B. (1978). Acta Cryst. B34, 3071-3072.
Brown, I. D. (2002). In The Chemical Bond in Inorganic Chemistry: The Bond Valence Model. Oxford University Press.
Brown, I. D. (2006). Acta Cryst. B62, 692-694.
Brown, I. D. (2009). Chem. Rev. 109, 6858-6919.
Burrows, A. D., Cassar, K., Mahon, M. F. & Warren, J. E. (2007). Dalton Trans. pp. 2499-2509.
Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565.
Hasegawa, M., Inomaki, Y., Inayoshi, T., Hoshi, T. & Kobayashi, M. (1997). Inorg. Chim. Acta, 257, 259-264.
Ho, D. M., Berardini, M. E. & Arvanitis, G. M. (2009). Acta Cryst. C65, m391-m394.
Inamori, Y., Sakagami, Y., Morita, Y., Shibata, M., Sugiura, M., Kumeda, Y., Okabe, T., Tsujibo, H. & Ishida, N. (2000). Biol. Pharm. Bull. 23, 995-997.
Inamori, Y., Tsujibo, H., Ohishi, H., Ishii, F., Mizugaki, M., Aso, H. & Ishida, N. (1993). Biol. Pharm. Bull. 16, 521-523.
Kadir, K., Mohammad Ahmed, T., Noreús, D. & Eriksson, L. (2006). Acta Cryst. E62, m1139-m1141.
Li, W., Jia, H.-P., Ju, Z.-F. & Zhang, J. (2008). Inorg. Chem. Commun. 11, 591-594.
Lin, H., Su, H. & Feng, Y.-L. (2006). Z. Kristallogr. New Cryst. Struct. 221, 173-175.
Macintyre, W. M., Robertson, J. M. & Zahrobsky, R. F. (1966). Proc. R. Soc. London Ser. A, 289, 161-170.
Miyamoto, D., Kusagaya, Y., Endo, N., Sometani, A., Takeo, S., Suzuki, T., Arima, Y., Nakajima, K. & Suzuki, Y. (1998). Antiviral Res. 39, 89-100.
Morita, Y., Matsumura, E., Okabe, T., Shibata, M., Sugiura, M., Ohe, T., Tsujibo, H., Ishida, N. & Inamori, Y. (2003). Biol. Pharm. Bull. 26, 1487-1490.
Nomiya, K., Onodera, K., Tsukagoshi, K., Shimada, K., Yoshizawa, A., Itoyanagi, T., Sugie, A., Tsuruta, S., Sato, R. & Kasuga, N. C. (2009). Inorg. Chim. Acta, 362, 43-55.
Nomiya, K., Yoshizawa, A., Kasuga, N. C., Yokoyama, H. & Hirakawa, S. (2004). Inorg. Chim. Acta, 357, 1168-1176.
Nonius (1998). COLLECT. Nonius BV, Delft, The Netherlands.
Nozoe, T. (1936). Bull. Chem. Soc. Jpn, 11, 295-298.
Olejnik, Z., Jezowska-Trzebiatowska, B. & Lis, T. (1986). J. Chem. Soc. Dalton Trans. pp. 97-101.
Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307-326. New York: Academic Press.
Robertson, J. M. (1951). J. Chem. Soc. pp. 1222-1229.
Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.
Thompson, J. S. & Calabrese, J. C. (1986). J. Am. Chem. Soc. 108, 1903-1907.
Vigato, P. A., Peruzzo, V. & Tamburini, S. (2009). Coord. Chem. Rev. 253, 1099-1201.
Watson, W. H. & Holley, W. W. (1984). Croat. Chem. Acta, 57, 467-476.