1:1 Cross-assembly of two β-diketonate complexes through arene-perfluoroarene interactions

Article abstract of DOI:10.1002/anie.200702662

(Figure Presented) Stack 'em up: Two coordination complexes - one a perfluoroarene-functionalized β-diketonate copper complex (purple, see picture), the other an arene-functionalized metal (M = Cu, Pd, Pt) complex (green) - form alternately layered arrays through arene-perfluoroarene interactions with metal-to-metal distances close to van der Waals contacts to give 1:1 cocrystals as one-dimensional metal wires.

Full text of DOI:10.1002/anie.200702662

Angewandte
Chemie
DOI: 10.1002/anie.200702662
Metal Arrays
1:1 Cross-Assembly of Two b-Diketonate Complexes through Arene–
Perfluoroarene Interactions**
Akiko Hori,* Ayaka Shinohe, Mikio Yamasaki, Eiji Nishibori, Shinobu Aoyagi, and
Makoto Sakata
Closely arranged metal–metal systems[1,2] have been inves-
tigated in efforts to obtain new magnetic[3] and conductive[4]
materials of nanometer size to exploit innovative functions.
How to construct the systems in order to make use of the
metal–metal interactions is a crucial issue for many chemists.
The most popular strategy for this purpose is direct con-
struction of coordination compounds from metals and organic
frames through coordination bonds.[5,6] On the other hand, in
an example of an indirect method, hydrogen bonds were used
to arrange discrete metal complexes.[7] Electrostatic interac-
tions are also frequently used to control the systems as they
are weaker,[8,9] though it is difficult to control the direction-
ality of the self-assembled system in many cases. The arene–
perfluoroarene interaction[10] as an example of electrostatic
interactions is a promising approach to control the direction
and position of intermolecular interactions by quadrupole
moments.[11] For example, two different organic molecules are
regularly arranged by such interactions between arene- and
perfluoroarene-functionalized moieties.[10,12,13] This idea
prompted us to cross-assemble different metal complexes
through arene–perfluoroarene interactions. Here, we demon-
Scheme 1. Arene complexes 1a–1c, perfluoroarene complex 2, and the
strate the one-dimensional arrangement of metal complexes,
namely, the arene-functionalized CuII complex[14] 1a and the
1:1 mixed complexes 3a–3c.
perfluoroarene-functionalized
CuII
complex[15,16]
2
(Scheme 1). The metal–metal distance is close to that of the
van der Waals contact. This is the first application of the
simple and unique construction strategy through arene–
perfluoroarene interactions between different complexes to
obtain a metal–metal arrangement.[17] Furthermore, the
analogous cross-assembled architectures have also been
achieved with PdII and PtII complexes,[18] which suggests a
great utility of this method for obtaining metal cross-
assemblies.
Complexes 1a and 2, prepared independently as previ-
ously described,[14,16] were combined in an organic solvent to
promote the cross-assembly. Typically, a solution of arene
complex 1a (20.4 mg, 0.04 mmol) in CH2Cl2 (10 mL) and a
solution of perfluoroarene complex 2 (34.8 mg, 0.04 mmol) in
CH2Cl2 (2 mL) were combined at ambient temperature to
give slowly a cocrystal, 3a, as fiber-like pale green micro-
crystals (48% yield). After slow evaporation of the remaining
solvent, pure 3a was obtained as crystals in almost quantita-
tive yield. Elemental (C,H) and atomic absorption (Cu)
analyses were consistent with the formula C60H24Cu2F20O8 for
3a (calcd (%) for C60H24Cu2F20O8: C 52.22, H 1.75, Cu 9.21;
found: C 52.26, H 1.86, Cu 9.58).
[*] Dr. A. Hori, A. Shinohe
Department of Chemistry, School of Science
Kitasato University
1-15-1 Kitasato, Sagamihara-shi, Kanagawa 228-8555 (Japan)
Fax: (+81)42-778-9953
E-mail: hori@kitasato-u.ac.jp
Dr. M. Yamasaki
Rigaku Corporation
Matsubara-cho, Akishima-shi, Tokyo 196-8666 (Japan)
Prof. Dr. E. Nishibori, Dr. S. Aoyagi, Prof. Dr. M. Sakata
Department of Applied Physics, Nagoya University
Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan)
[**] This work was supported by a Grant-in-Aid for Young Scientists
Start-Up (no. 18850022) from the JSPS (A.H.) and a Grant-in-Aid for
Young Scientists A (no. 17686003) from MEXT (E.N.). A.H. and A.S.
thank Prof. Dr. Takeshi Miyamoto of Kitasato University for valuable
suggestions. Thanks are also due to Professors Makoto Fujita and
Masaki Kawano of the University of Tokyo for the opportunity to
carry out solid-state luminescence and UV/Vis measurements. The
synchrotron radiation experiments were performed at beamline
BL02B2 at SPring-8 with the approval of JASRI.
Single crystals of 3a, composed of 1a and 2, were obtained
from CH2Cl2-benzene and were suitable for X-ray crystallog-
raphy studies (Figure 1).[19] The geometries around the two
Cu centers are essentially planar. In the part corresponding to
1a, the Cu1–O1 and Cu1–O2 bond lengths are 1.9078(10) and
Supporting information for this article is available on the WWW
under http://www.angewandte.org or from the author.
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to 38.0–45.48 in the crystal of 3a, as mentioned above. Thus,
the torsion angles of the phenyl and pentafluorophenyl rings
are forced closer for close packing of the planes. Accordingly,
the arene–perfluoroarene interaction is observed in the
columnar stacking along the a axis through alternatively
aligned 1a and 2. Note that the interaction does not depend
on the aryl rings being coplanar. It is pointed out that the
direction of the stacking is along the direction of the needle
À
crystal growth. C H···F interactions are also observed as
intermolecular interactions between 1a and 2 in this align-
À
ment; the shortest C H···F distances between hydrogen and
fluorine atoms is 2.42 Š (H1(1a)···F6(2)).[16,20]
Surprisingly, the cross-assembly through arene–perfluor-
oarene interactions also proceeded easily when the central
metal was changed to Pd (1b) and Pt (1c). The 1:1 cocrystals
3b and 3c were prepared as fiber-like microcrystals. The
results of elemental (C,H) and atomic absorption (Cu)
analyses clearly showed the 1:1 cross-assemblies for 3b
(calcd (%) for C60H24CuF20O8Pd: C 50.65, H 1.70, Cu 4.47;
found: C 50.70, H 1.75, Cu 4.69) and for 3c (calcd (%) for
C60H24CuF20O8Pt: C 47.68, H 1.60, Cu 4.20; found: C 47.62, H
1.64, Cu 4.54).[21] The melting points of complexes 3 (2848C
(3a), 2908C (3b), and 3098C (3c)) were sufficiently different
from those of the starting materials (3218C (1a), 2708C dec.
(1b), 2878C dec. (1c), and 2168C (2)). The thermal stability of
the resultant complexes 3a–3c was higher than those of the
starting materials, except for 1a.
Figure 1. ORTEP drawing of the crystal structure of 3a with 50%
probability thermal ellipsoids.
1.9148(10) Š, respectively, and the O1–C7 and O2–C9 bond
lengths are 1.2817(17) and 1.2769(17) Š, respectively. In the
part corresponding to 2, the Cu2–O3 and Cu2–O4 bond
lengths are 1.9032 (10) and 1.9095(10) Š, respectively, and the
O3–C22 and O4–C24 bond lengths are 1.2724(16) and
1.2709(17) Š, respectively. The phenyl rings of 1a have
twisted conformations with respect to the coordination
plane with torsion angles C5-C6-C7-C8 and C8-C9-C10-C15
of 28.0(2) and 35.1(2)8, respectively, while the pentafluor-
ophenyl rings of 2 have more twisted conformations with
respect to the coordination plane with torsion angles C20-
C21-C22-C23 and C23-C24-C25-C30 of 38.0(2) and 45.5(2)8,
respectively.
As the crystals of 3b and 3c were very small, synchrotron
radiation (SR) X-ray powder experiments were performed to
obtain structural information.[22,23] SR powder patterns of 3a,
3b, and 3c are shown in Figure 3. The peak positions of 3a–3c
The two complexes are alternately aligned as columnar
stacks (Figure 2). The Cu1···Cu2 distance is 3.612 Š. The
average distances between phenyl and pentafluorophenyl
Figure 3. The powder X-ray analyses show very similar patterns:
a) CuCu of 3a, b) CuPd of 3b, and c) CuPt of 3c at 100 K (the full
region 0–758 (2q) is provided in the Supporting Information).
Figure 2. Crystal packing of 3a: view approximately along the c axis
showing the formation of one-dimensional columns through arene–
perfluoroarene interactions (complex 1a, green; complex 2, purple).
are very similar in this 2q range. No peak splits indicating
existence of other phases were observed in these data, which
suggests that the same manner of alignment was achieved
through arene–perfluoroarene interactions. The lattice
parameters determined by the LeBail method for 3a–3c are
listed in Table 1. The differences in the length and angle are as
low as less than 0.1 Š and 1.08, respectively. The metal–metal
distances were estimated from the lattice parameters, and at
rings are also short: 3.610 Š between C1-C2-C3-C4-C5-C6
and C16-C17-C18-C19-C20-C21, and 3.618 Š between C10-
C11-C12-C13-C14-C15 and C25-C26-C27-C28-C29-C30. The
torsion angles are quite different in 3a as compared to the
individual crystals of 1a and 2: for example, from 0.6–10.58 in
pure 1a[14] to 28.0–35.18 in 3a, and from 60.4–61.08 in pure 2[16]
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¯
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Table 1: Crystal parameters for 3a (single-crystal analysis) and 3a–3c
(powder X-ray analysis).
Parameter 3a (single crystal) 3a
3b
7.2095(1)
3c
7.1833(1)
a [ꢀ]
b [ꢀ]
c [ꢀ]
a [8]
b [8]
g [8]
7.2240(11)
13.294(3)
13.766(3)
78.841(5)
85.387(6)
80.713(7)
7.2210(6)
13.2670(2) 13.3598(3) 13.4353(3)
13.7478(2) 13.7666(3) 13.7648(3)
78.810(10) 78.417(2)
85.351(10) 84.392(2)
80.657(10) 80.722(2)
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84.320(3)
80.088(3)
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100 K they correspond to 3.611 Š for 3a (Cu···Cu), 3.605 Š
for 3b (Cu···Pd), and 3.592 Š for 3c (Cu···Pt).
The constitution of the crystals 3 was independent of the
starting ratios of 1 and 2. When a mixed solution of 1 and 2 in
different ratios was completely dried by natural evaporation,
two kinds of crystals crystallized separately, corresponding to
3 and the excess starting material 1 or 2.[24] In other words, a
1:1 assembly is exclusively obtained and any random mixture
was not observed. The solubility of complexes 3 in CH2Cl2
decreases in the order 3a @ 3b > 3c, appearing to depend on
the metals present, and it is probably due to the different
rigidities of the complexes 1a–1c. Thus, in a competitive
experiment in which a combination of 1a, 1b, and 2 (1:1:1
stoichiometry) was employed, 3b was obtained exclusively
and as a pure product. Similarly, compounds 1a, 1c, and 2
(1:1:1 stoichiometry) gave 3c, while 1b, 1c, and 2 (1:1:1
stoichiometry) gave a mixture ( ꢀ 1:2) of 3b:3c.[21] This is the
selectivity induced by the crystallization process of the
differently soluble complexes.
Furthermore, non-radiative decay was observed in the
Cu···Pt mixed complex 3c in studies of solid-state lumines-
cence and UV/Vis spectroscopy (with BaSO4), while the Pt
complex 1c showed luminescence around 540 nm (irradiation
at 440 nm). It is suggested that energy transfer occurs between
the closely arranged Pt and Cu complexes. A detailed
investigation of the metal···metal properties with the indirect
interaction is of further interest.
In conclusion, we have reported a 1:1 cross-assembly by
combining arene- and perfluoroarene-functionalized com-
plexes in an organic solvent. The two different metals in these
complexes are highly ordered to give striped one-dimensional
structures through arene–perfluoroarene interactions. This
strategy may open the door to next-generation nanometer-
sized metal-wire synthesis.
Received: June 18, 2007
Published online: August 29, 2007
Keywords: copper · crystal engineering ·
.
electrostatic interactions · fluorinated ligands · self-assembly
¯
[19] Crystal data for 3a (C60H24Cu2F20O8: Mr 1379.90): triclinic, P1,
T= 93 K, a = 7.2240(11) Š, b = 13.294(3) Š, c = 13.766(3) Š,
a = 78.841(5)8, b = 85.387(6)8, g = 80.713(7)8, V= 1278.4(4) Š3,
Z = 1, 1calcd = 1.792 gcmÀ3, F(000) = 686, l = 0.71070 Š, GOF =
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2
1.019, R1(I>2s(I)) = 0.0268, wR2(Fo ) = 0.0817. X-ray data were
collected using a Rigaku CCD detector (Saturn 724) mounted on
a Rigaku rotating anode X-ray generator (Micro Max-007HF)
and Mo Ka radiation from a corresponding confocal optics.
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CCDC-650334 contains the supplementary crystallographic data
The powder samples were loaded into a lindeman glass capillary
with 0.4 mm inner diameter. The temperature was controlled by
using a low-temperature nitrogen gas blower. The powder
patterns were measured at 100 K. The exposure time of each
sample was 75 min for 3a, 60 min for 3b, and 55 min for 3c.
[23] E. Nishibori, M. Takata, K. Kato, M. Sakata, Y. Kubota, S.
Aoyagi, Y. Kuroiwa, M. Yamakata, N. Ikeda, Nucl. Instrum.
Methods Phys. Res. Sect. A 2001, 467, 1045.
[24] The order of crystallization was determined by the relative
solubilities: for example, in the case of 3a, the starting material 1
crystallized first on the condition of 1a/2 ꢁ 2; in the case of 3b
and 3c, only mixed complex 3 was crystallized in high yields in
the condition of 1:2 = 1:5–5:1 at 2 mm. See Supporting Informa-
tion.
for this paper. These data can be obtained free of charge from
The Cambridge Crystallographic Data Centre via www.ccdc.ca
m.ac.uk/data_request/cif.
[20] V. R. Thalladi, H.-C. Weiss, D. Blaser, R. Boese, A. Nangia,
G. R. Desiraju, J. Am. Chem. Soc. 1998, 120, 8702.
[21] Detailed results of elemental (C,H) and atomic absorption (Cu)
analyses are summarized in the Supporting Information. Com-
ponents 1a–1c and 2 are expected to give the following results:
calcd (%) for 1a: C 70.65, H 4.35; 1b: C 65.17, H 4.01; 1c: C
56.16, H 3.46; 2: C 41.42, H 0.23.
[22] The synchrotron powder diffraction experiment was carried out
at BL02B2 Spring-8 with a large Debye–Scherrer type diffrac-
tometer.[23] The wavelength of the incident X-rays was 0.80 Š.
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