Two new polymorphs of trans-bis(hinokitiolato)copper(II)

Article abstract of DOI:10.1107/S0108270104001957

The title complex [systematic name: trans-bis(3-isopropyl-7-oxocyclohepta-1,3,5-trienolato)copper(II)], [Cu(C₁₀H₁₁O₂)₂], is a substance possessing antimicrobial activity. The compound crystallizes in a number of polymorphic forms, the structures for two of which are reported here. Stacks of square-planar molecules exhibiting weak intermolecular copper-olefin π interactions (not observed in earlier reports on this substance) are described. The molecules have crystallographically imposed inversion symmetry, with stacking and copper-olefin π distances ranging from 3.226 (2) to 3.336 (1) A.

Full text of DOI:10.1107/S0108270104001957

metal-organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
Form (Ia) crystallizes in the triclinic space group P1, while
forms (Ib) and (Ic) crystallize in the monoclinic space group
P21/c. In all three forms, the Cu atoms reside on centers of
crystallographic inversion symmetry and have square-planar
coordination geometries. The CuÐO bonds in (Ia) are
statistically non-equivalent, while those in (Ib) are equivalent.
The CuÐO bonds in (Ic) are also equal in length, albeit
signi®cantly shorter than those observed in (Ib). Comparable
equivalent and non-equivalent CuÐO bonds have been
observed in related copper±tropolonate complexes (Hase-
gawa et al., 1997; Chipper®eld et al., 1998) and in copper
complexes involving ꢂ- or ꢁ-hydroxy ketone ligands (Lim et
al., 1994; Odoko et al., 2002). The OÐCuÐO bite angles for
the chelating hinokitiolate ligands in all three polymorphs are
also statistically equivalent.
ISSN 0108-2701
Two new polymorphs of trans-
bis(hinokitiolato)copper(II)
Georgia M. Arvanitis,a* Michael E. Berardinia and
Douglas M. Hob
aThe College of New Jersey, Chemistry Department, PO Box 7718, Ewing,
NJ 08628 0718, USA, and bPrinceton University, Department of Chemistry,
Princeton, NJ 08544 1009, USA
Correspondence e-mail: arvanit@tcnj.edu
Received 17 November 2003
Accepted 26 January 2004
Online 19 February 2004
The title complex [systematic name: trans-bis(3-isopropyl-7-
oxocyclohepta-1,3,5-trienolato)copper(II)], [Cu(C10H11O2)2],
is a substance possessing antimicrobial activity. The compound
crystallizes in a number of polymorphic forms, the structures
for two of which are reported here. Stacks of square-planar
molecules exhibiting weak intermolecular copper±ole®n ꢀ
interactions (not observed in earlier reports on this substance)
are described. The molecules have crystallographically
imposed inversion symmetry, with stacking and copper±ole®n
trans-Bis(hinokitiolato)copper(II) is essentially a planar
molecule. The r.m.s. deviation of atoms from the least-squares
plane through the molecule (excluding the isopropyl atoms) is
Ê
Ê
0.017 (2) A for (Ia) and 0.071 (2) A for (Ib). The less planar
Ê
ꢀ distances ranging from 3.226 (2) to 3.336 (1) A.
Comment
Metal complexes of tropolone derivatives have engaged the
interest of researchers in such diverse areas as materials
science and medicinal chemistry. Some of that interest has
been focused on hinokitiol (ꢁ-thujaplicin), a tropolone and
natural product ®rst isolated from Chamaecyparis taiwanensis
(Nozoe, 1936). Hinokitiol and its metal complexes have since
been shown to exhibit a wide variety of biological activities,
e.g. antibacterial, antifungal and antiviral activities, among
others (Miyamoto et al., 1998; Arima et al., 2003; Morita et al.,
2003). Hinokitiol complexes of Cu, Zn and Sn have also been
reported to be effective in oral care formulations (Creeth et
al., 2000), and the structures of a copper hinokitiol monomer
and a modi®cation containing both monomers and dimers
have been published as part of those studies (Barret et al.,
2002). We have observed, however, that the title monomer, i.e.
trans-bis(hinokitiolato)copper(II), (I), actually exists in a
number of additional polymorphic forms: a triclinic form, (Ia),
and a new monoclinic form, (Ib), have been obtained from
ethanol±water solutions and are reported here. The previously
published monoclinic form, (Ic), was obtained from ethanol.
Views of the molecules of forms (Ia) and (Ib) are given in
Fig. 1, and selected distances and angles are summarized in
Table 1.
Figure 1
Polymorphs (Ia) at 298 K (top) and (Ib) at 200 K (bottom). Displacement
ellipsoids are drawn at the 50% probability level. [Symmetry codes: (i)
x, 1 y, 2 z; (ii) 1 x, y, z.]
m126 # 2004 International Union of Crystallography
DOI: 10.1107/S0108270104001957
Acta Cryst. (2004). C60, m126±m128

metal-organic compounds
nature of (Ib) is visible in Fig. 2 as a slight folding of the
molecule along the O1Á Á ÁO2 and O1iiÁ Á ÁO2ii vectors [the
interplanar angle between the CuO4 coordination plane and
each tropolone ligand plane is 172.9 (1)ꢀ; symmetry code: (ii)
CuÁ Á ÁCu distances between neighboring molecules within the
Ê
Ê
stacks are 5.1549 (3) A in (Ia) and 6.7470 (1) A in (Ib), i.e. a
unit translation in the crystallographic a and b directions,
respectively. Furthermore, as shown in Fig. 2, the molecules do
not stack directly on top of one another but instead slide over
1
x, y, z]. In contrast, the molecules of (Ia) and (Ic) are
Ê
essentially planar, with corresponding interplanar angles of
178.3 (1) and 178.9 (2)ꢀ, respectively. These conformational
differences in the trans-bis(hinokitiolato)copper(II) molecules
are attributed to packing forces.
each other by 3.930 (1) and 5.921 (2) A in (Ia) and (Ib),
respectively.
The triclinic form also differs from (Ib) in that there are
weak interstack CÐHÁ Á ÁO hydrogen-bonding interactions
present in (Ia). The C6ÐH6, H6Á Á ÁO2iii and C6Á Á ÁO2iii
The packings of the trans-bis(hinokitiolato)copper(II)
molecules in (Ia) and (Ib) share a number of similarities
(Fig. 2) but differ completely from the packing observed in
previously published form (Ic). Most notably, the molecules in
(Ia) and (Ib) pack into extended columns or stacks, while
those in (Ic) do not. Consequently, the Cu atoms in (Ia) and
(Ib) are pseudo-six-coordinate, with weak apical interactions,
while the Cu atoms in (Ic) are formally four-coordinate.
Interestingly, the apical interactions in (Ia) and (Ib) also differ.
The apical interactions in (Ia) are best described as involving
ꢀ-electron densities distributed over the C1ÐC7ÐC6ÐC5Ð
C4 portion of neighboring hinokitiolate ligands, while the
apical interactions in (Ib) involve only the C4ÐC5 edge of
Ê
distances are 0.93, 2.51 and 3.348 (4) A, respectively, and the
C6ÐH6Á Á ÁO2iii angle is 150ꢀ [symmetry code: (iii) 1 x, y,
2 z]. Whether these hydrogen-bonding interactions contri-
bute to the non-equivalence of the CuÐO bonds in (Ia) is not
known at this time.
Experimental
The title compound was isolated from the reaction of copper
gluconate and hinokitiol (Aldrich Chemical Company) in a 1:2 molar
ratio. An aqueous solution of copper gluconate was added to a
solution of hinokitiol in ethanol and the mixture was stirred for 1 h.
The resulting green precipitate was collected and recrystallized from
aqueous ethanol. An assortment of crystal morphologies was imme-
diately evident in the recrystallized product. Both (Ia) and (Ib)
crystallize as green±yellow needles, but the two forms have noticeably
different physical properties that aid in their identi®cation. Crystals
of (Ia) are soft and often distort or split into layers when attempts are
made to cut them. Crystals of (Ib) are dichroic, i.e. green±yellow
when viewed perpendicular to the 001 face and olive green when
viewed perpendicular to the 100 face. The previously published
polymorph, (Ic), crystallizes as olive-green multifaceted prisms.
Ê
neighboring molecules. The Cu atom is 3.336 (1) A from the
centroid de®ned by atoms C1, C4, C5, C6 and C7 in (Ia), and
Ê
3.226 (2) A from the centroid of the C4ÐC5 bond in (Ib).
Ê
These distances are comparable to values (3.25±3.55 A)
observed for longer-range non-covalent CuIIÁ Á Áarene contacts
(Mascal et al., 2000).
Thus, the packing and stacking of molecules in (Ia) and (Ib)
are consistent with the presence of weak apical ꢃ5 and ꢃ2 Cu±
ole®n±ꢀ interactions, respectively. The distance between the
least-squares planes through adjacent molecules, or stacking
Ê
Ê
distance, is 3.336 (1) A in (Ia) and 3.235 (2) A in (Ib), and the
Polymorph (Ia)
Crystal data
[Cu(C10H11O2)2]
Mr = 389.92
Triclinic, P1
Z = 1
Dx = 1.404 Mg m
Mo Kꢂ radiation
3
Ê
a = 5.1549 (3) A
Cell parameters from 6146
re¯ections
Ê
b = 6.9872 (4) A
c = 13.9097 (8) A
ꢂ = 77.747 (3)ꢀ
ꢁ = 84.255 (3)ꢀ
ꢄ = 70.508 (3)ꢀ
ꢅ = 1.5±27.5ꢀ
ꢆ = 1.20 mm
T = 298 (2) K
Ê
1
Needle, green±yellow
0.29 Â 0.08 Â 0.04 mm
3
Ê
V = 461.30 (5) A
Data collection
Nonius KappaCCD diffractometer
! scans
1541 re¯ections with I > 2ꢇ(I)
Rint = 0.064
Absorption correction: Gaussian
(SHELXTL; Sheldrick, 1996)
Tmin = 0.786, Tmax = 0.955
6146 measured re¯ections
2096 independent re¯ections
ꢅmax = 27.5ꢀ
h = 6 ! 6
k = 8 ! 9
l = 17 ! 18
Re®nement
Re®nement on F2
R[F2 > 2ꢇ(F2)] = 0.048
wR(F2) = 0.107
w=1/[ꢇ2(F2o) + (0.0469P)2
+ 0.197P]
where P = (F2o + 2Fc2)/3
S = 1.08
2095 re¯ections
118 parameters
H-atom parameters constrained
(Á/ꢇ)max
Áꢈmax = 0.27 e A
=
0.001
3
Ê
3
Ê
0.51 e A
Extinction correction: SHELXTL
Áꢈmin
=
Figure 2
Extinction coef®cient: 0.032 (7)
Stacking and ꢀ interactions in polymorphs (Ia) (top) and (Ib) (bottom).
ꢁ
Acta Cryst. (2004). C60, m126±m128
Georgia M. Arvanitis et al. [Cu(C10H11O2)2] m127

metal-organic compounds
default values for the speci®ed functional groups and temperatures.
The SHELXTL internal defaults for the tropolone, isopropyl
Polymorph (Ib)
Ê
methine and methyl H atoms are 0.93, 0.98 and 0.96 A, respectively,
Crystal data
Ê
for polymorph (Ia) at 298 K, and 0.95, 1.00 and 0.98 A for (Ib) at
3
[Cu(C10H11O2)2]
Mr = 389.92
Dx = 1.457 Mg m
Mo Kꢂ radiation
200 K. The Uiso(H) values were set at 1.2Ueq(C) for the tropolone and
isopropyl methine H atoms, and 1.5Ueq(C) for the methyl H atoms.
For both forms, data collection: COLLECT (Nonius, 1998); cell
re®nement: DENZO±SMN (Otwinowski & Minor, 1997); data
reduction: DENZO±SMN and SHELXTL (Sheldrick, 1996);
program(s) used to solve structure: SHELXS86 (Sheldrick, 1990) for
(Ia) and SHELXTL for (Ib); program(s) used to re®ne structure:
SHELXTL; molecular graphics: SHELXTL; software used to
prepare material for publication: SHELXTL.
Monoclinic, P21=c
Cell parameters from 23 670
re¯ections
Ê
a = 8.7410 (2) A
ꢅ = 2.4±27.5ꢀ
ꢆ = 1.25 mm
T = 200 (2) K
Ê
b = 6.7470 (1) A
1
Ê
c = 15.3448 (4) A
ꢁ = 100.800 (1)ꢀ
3
Ê
V = 888.94 (3) A
Z = 2
Needle, green±yellow
0.22 Â 0.12 Â 0.05 mm
Data collection
Nonius KappaCCD diffractometer
! scans
1591 re¯ections with I > 2ꢇ(I)
Rint = 0.076
Absorption correction: Gaussian
(SHELXTL; Sheldrick, 1996)
Tmin = 0.794, Tmax = 0.948
23 670 measured re¯ections
2040 independent re¯ections
ꢅ
max = 27.5ꢀ
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: FR1457). Services for accessing these data are
described at the back of the journal.
h = 11 ! 11
k = 8 ! 7
l = 19 ! 19
Re®nement
References
Re®nement on F2
R[F2 > 2ꢇ(F2)] = 0.048
wR(F2) = 0.112
S = 1.12
2040 re¯ections
w=1/[ꢇ2(F2o) + (0.0549P)2
+ 1.192P]
Arima, Y., Nakai, Y., Hayakawa, R. & Nishino, T. (2003). J. Antimicrob.
Chemother. 51, 113±122.
Barret, M. C., Mahon, M. F., Molloy, K. C., Wright, P. & Creeth, J. E. (2002).
Polyhedron, 21, 1761±1766.
Chipper®eld, J. R., Clark, S., Elliott, J. & Sinn, E. (1998). Chem. Commun.
pp. 195±196.
where P = (F2o + 2Fc2)/3
(Á/ꢇ)max < 0.001
3
Ê
Áꢈmax = 0.70 e A
3
Ê
0.83 e A
117 parameters
H-atom parameters constrained
Áꢈmin
=
Creeth, J., Molloy, K. C. & Wright, P. (2000). PCT Int. Appl. WO 00/16736.
Hasegawa, M., Inomaki, Y., Inayoshi, T., Hoshi, T. & Kobayashi, M. (1997).
Inorg. Chim. Acta, 257, 259±264.
Lim, Y. Y., Chen, W., Tan, L. L. & Lim, K. H. (1994). Polyhedron, 13, 2379±
2385.
Table 1
Selected geometric parameters (A, ꢀ).
Ê
(Ia)²
(Ib)²
(Ic)³
Â
Mascal, M., Kerdelhue, J.-L., Blake, A. J., Cooke, P. A., Mortimer, R. J. & Teat,
S. J. (2000). Eur. J. Inorg. Chem. pp. 485±490.
Cu1ÐO1
Cu1ÐO2
O1ÐC1
O2ÐC7
1.915 (2)
1.901 (2)
1.295 (3)
1.289 (4)
1.918 (2)
1.913 (2)
1.292 (3)
1.293 (3)
1.900 (2)
1.904 (2)
1.296 (5)
1.293 (5)
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.
O1ÐCu1ÐO2
Cu1ÐO1ÐC1
Cu1ÐO2ÐC7
83.70 (9)
113.0 (2)
113.5 (2)
83.90 (8)
112.9 (2)
112.7 (2)
83.84 (13)
113.5 (3)
113.5 (3)
Nonius (1998). COLLECT. Nonius BV, Delft, The Netherlands.
Nozoe, T. (1936). Bull. Chem. Soc. Jpn, 11, 295±298.
Odoko, M., Yamamoto, K. & Okabe, N. (2002). Acta Cryst. C58, m506±m508.
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.
² This work. ³ Barret et al. (2002).
Sheldrick, G. M. (1990). Acta Cryst. A46, 467±473.
Sheldrick, G. M. (1996). SHELXTL. Version 5.04. Siemens Analytical X-ray
Instruments Inc., Madison, Wisconsin, USA.
All H atoms were allowed to ride on their respective C atoms, with
CÐH distances constrained to the SHELXTL (Sheldrick, 1996)
ꢁ
m128 Georgia M. Arvanitis et al.
[Cu(C10H11O2)2]
Acta Cryst. (2004). C60, m126±m128