Versatile anion-π interactions between halides and a conformationally rigid bis(tetraoxacalix[2]arene[2]triazine) cage and their directing effect on molecular assembly

Article abstract of DOI:10.1002/chem.201002307

Interactive halides: Bis(tetraoxacalix[2]arene[2]triazine), a conformationally rigid cage molecule of three V-shaped electron-deficient clefts, forms 1:1 complexes with fluoride (361 M^-1), chloride (146 M^-1) and bromide (95 M^-1<

Full text of DOI:10.1002/chem.201002307

COMMUNICATION
DOI: 10.1002/chem.201002307
Versatile Anion–p Interactions between Halides and a Conformationally
Rigid Bis(tetraoxacalix[2]arene[2]triazine) Cage and Their Directing Effect
on Molecular Assembly
De-Xian Wang,*[a] Qi-Qiang Wang,[a] Yuchun Han,[b] Yilin Wang,*[b]
Zhi-Tang Huang,[a] and Mei-Xiang Wang*[a, c]
Recent years have witnessed an increasing interest in
anion–p interactions, that is, the interaction between an
anion and an electron-deficient p-arene species.[1] A number
of theoretical studies,[1,2] for example, have suggested nonco-
valent interactions of anions with aromatic compounds, such
as perfluoro-, nitro- and cyano-substituted benzene, pyri-
dine, pyrazine, and triazine derivatives. As proposed by Hay
and his co-workers,[3] interaction of an anion with a aromatic
p system leads to either a noncovalent anion–p complex A,
a weak s-complex B, or the Meisenheimer intermediate C.
A number of experimental studies[4] have demonstrated in-
teractions between anions and p systems; however, experi-
mental evidence to support “pure” anion–p interactions
with charge-neutral arenes is very rare.[3,5] Indeed, a recent
report indicated that the noncovalent anion–p interaction
contributes less significantly to the formation of chloride–p-
C6FnH6Àn complex.[6]
Heteroatom-bridged calixaromatics are an emerging type
of novel macrocyclic molecules and they exhibit unique and
versatile structural and molecular recognition properties.[7]
Very recently, we have discovered that tetraoxacalix[2]-
AHCTUNGTERGaNNUN rene[2]triazine, a conformationally flexible macrocyclic
host molecule with two electron-deficient triazine rings, self-
regulates its cavity structure to form ternary complexes with
halides and water.[5b] Typical noncovalent anion–p interac-
tions (type A) between chloride, bromide and triazine, and
lone-pair-electrons–p (lpe–p) interactions between the in-
cluded water molecule and triazine are observed in the solid
state.
[a] Dr. D.-X. Wang, Q.-Q. Wang, Prof. Z.-T. Huang,
Prof. Dr. M.-X. Wang
To obtain other types of halide–p interactions[3] and to ex-
plore the effect of anion–p interactions on the molecular as-
sembly, we devised a conformationally rigid cage molecule
that contains three electron-deficient V-shaped clefts. We
envisioned that the electron-deficient triazine ring incorpo-
rated into a conformational rigid host might form various
anion–p complexes. To our delight, different types of
halide–p interactions with electron-deficient triazine rings
were observed. Multiple anion–p interactions along with
other noncovalent bond interactions, such as hydrogen
bonding, halogen bonding, and lpe–p interactions, directed
the formation of different molecular assemblies in the solid
state. An isothermal titration calorimetry (ITC)[8] study re-
vealed that, in acetonitrile, the cage molecule formed 1:1
complexes with fluoride, chloride, and bromide, with associ-
ation constant being 361, 146, and 95mÀ1, respectively.
Scheme 1 illustrates the synthesis of cage molecule,
bis(tetraoxacalix[2]arene[2]triazine) (4). The reaction of
Beijing National Laboratory for Molecular Sciences
CAS Key Laboratory of Molecular Recognition and Function
Institute of Chemistry, Chinese Academy of Sciences
Beijing 100190 (P. R. China)
Fax : (+86)10-62564723, (+86)10-62565610
E-mail: wangmx@mail.tsinghua.edu.cn
dxwang@iccas.ac.cn
[b] Dr. Y. Han, Prof. Dr. Y. Wang
Beijing National Laboratory for Molecular Sciences
CAS Key Laboratory of Colloid and Interface Science
Institute of Chemistry, Chinese Academy of Sciences
Beijing 100190 (P. R. China)
Fax : (+86)10-82615802
E-mail: yilinwang@iccas.ac.cn
[c] Prof. Dr. M.-X. Wang
The Key Laboratory of Bioorganic Phosphorus Chemistry &
Chemical Biology (Ministry of Education)
Department of Chemistry, Tsinghua University
Beijing 100084 (P. R. China)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201002307.
Chem. Eur. J. 2010, 16, 13053 – 13057
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
13053

and [4ꢀ
(Et4NBr)2ꢀH2O][11] showed intriguing interactions
N
between host and guest species.
As illustrated in Figure 2, the host of the complex [4ꢀ
(Et4NCl)3ꢀ
ACHTUGNERTN(NUGN H2O)3] remained almost the same symmetric
cage conformation with two face-to-face paralleled benzene
Scheme 1. Synthesis of cage molecule 4.
phloroglucinol 1 with an excess amount of cyanuric chloride
2 in the presence of diisopropylethylamine (DIPEA) at 08C
gave intermediate 3 in 75% yield. Further treatment of 3
with phloroglucinol 1 in acetone at room temperature af-
forded the desired product 4 in a moderate yield. As indicat-
ed by the NMR spectroscopic data and X-ray crystallogra-
phy[9] (Figure 1), cage molecule 4 adopts a D3h symmetric,
all 1,3-alternate conformation with two benzene rings being
eclipsed. Three highly electron-deficient triazine rings form
three identical V-shaped clefts.
Single crystals of the complexes were cultivated by slow
evaporation of the solvent from the solution of host 4 and
tetraethylammonium halides in a mixture of dichlorometh-
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
Figure 2. X-ray structure of complex of 4 with tetraethylammonium chlo-
ride and water (50% probability). Selected distances (in ꢁ): C1···C1
9.152, C3···Cl2 3.342, C5···Cl2 3.541, Cl2···O3 3.163, C7···O3 3.065; select-
À
ed hydrogen bond angles (in 8): C5 H5···Cl2 150.5, O3-H3B-Cl2 175.5.
Cations and hydrogen atoms are omitted for clarity.
rings being very slightly twisted. Each V-shaped cleft accom-
modates one chloride anion and one H2O molecule. Inter-
estingly, all three chloride anions in different clefts are locat-
ed in one plane, while the water molecules are in another.
Being completely different from the previously reported
type A anion–p interaction between tetraoxacalix[2]-
AHCTUNGTRENNUNG
arene[2]triazine and chloride,[5b] in 4 each triazine ring inter-
acts with one chloride ion forming a weak s complex
(type B anion–p interaction); the chloride ion is situated
just above the carbon atom of triazine ring with a chloride–
carbon distance (dCl2 C2) of 3.342 ꢁ. In addition, the chloride
À
À
ion also forms a hydrogen bond with the arene C H of one
benzene moiety, giving a Cl ···H C distance of 3.541 ꢁ.
Moreover, the chloride ion also forms another hydrogen
À
À
Figure 1. X-ray structure of cage molecule 4. Selected distance: C1···C1
9.138 ꢁ. Solvent is omitted for clarity.
bond with the included water molecule (dCl2 O3 =3.163 ꢁ);
À
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Chem. Eur. J. 2010, 16, 13053 – 13057

Host–Guest Chemistry
COMMUNICATION
À
in turn the water molecule interacts with an arene C H of
the other benzene ring through hydrogen bonding (dO3
noncovalent interaction though host molecules A and B
were face-to-face orientated (Figure 3, bottom).
=
À
C7
3.065 ꢁ) (Figure 2, top). Finally, it is worth noting that
through the formation of a hydrogen-bond network, the
chloride ion and water molecule in each V-shaped cleft in-
teract with other pairs of chloride ions and water molecules
included in other hosts, yielding an infinite two-dimensional
honeycomb-like assembly (Figure 2, bottom and Figure S1
in the Supporting Information). Layers of tetraethylammo-
The multiple and various noncovalent binding modes
among hosts and guests in the largest cleft are of note. First
of all, the bromide ion and water molecule, which are hydro-
gen bonded to each other (dBr1 O4 =3.392 ꢁ), formed bro-
À
mide–p and lpe–p interactions,[12] respectively, with two tria-
zine rings. Both the bromide ion and the water molecule
were located above the triazine planes, and the Br1–tria-
zine-plane distance was 3.516 ꢁ, while the distance between
O4 and the plane of the other triazine was 2.892 ꢁ
(Figure 3, top). In addition, the bromide ion and water mol-
ecule interacted through a hydrogen-bond network with an-
other bromide and water pair, accommodated by the
neighboring host molecule D (Figure 3, bottom). Moreover,
the bromide ions in the cavity formed halogen bonds[13] with
the chloro substituents of host molecules C and E. This was
evidenced by the short distance between the bromide and
À
nium cations alternate with the layers of [{4ꢀ
ACHTUGNRTNE(NUNG Cl H2O)3}n]
(Figure S2 in the Supporting Information).
In the case of complex [4ꢀ(Et4NBr)2ꢀH2O] (Figure 3), al-
G
though the cage host still remained a trigonal conformation,
the angles between triazine planes varied, producing three
chlorine atom (dBr1 Cl1 =3.492 ꢁ) and the linear orientation
À
À
of bromide along the axis of Cl C bond (Figure 3, bottom).
Finally, there was also a short contact between a chlorine
atom and triazine carbon (dCl3 C7 =3.301 ꢁ), indicating a
À
weak lpe–p interaction[11] between hosts A and C and be-
tween hosts A and E.
In the last cleft, apart from the weak lpe–p interaction be-
tween a chlorine atom of host A and the triazine of host F,
there was a pair of strong lpe–p interactions between host A
and host G. The distances between the chlorine atom and
the centroid and the plane of triazine are 3.284 and 3.323 ꢁ,
respectively, and the chloro–centroid–plane angle is 80.928
(Figure 3, bottom).
The anion–p interaction between bromide and triazine
and the lpe–p interaction between the oxygen of water and
triazine are worth further addressing. Different from the ter-
nary complex of tetraoxacalix[2]arene[2]triazine with bro-
mide and water,[5b] in which bromide and water oxygen
atom are just above the centroids of two triazine rings, the
bromide and water moved toward the narrow rim of the
cleft in the current case. For example, the doffset values for
Br1 and O4 are 0.915 and 0.341 ꢁ, respectively. The p-com-
plexed Br2 anion in the smallest cleft, however, shifted
toward the wide-rim of the cleft with doffset parameter of
0.594 ꢁ (Figure 3, top). The offset positioning of bromide
and oxygen atom might suggest h3 anion–p and lpe–p com-
plexing modes. It was very interesting to note that the elec-
tron-deficient triazine ring formed a complex with two elec-
tron-rich guests, bromide from one side and a lone pair elec-
trons of oxygen from the other side (Figure 3, top). To the
best of our knowledge, no such type of interaction has been
previously reported. Multiple noncovalent interactions in-
cluding bromide–p interactions between hosts and guests
gave rise to a unique layered assembly (Figure 3, bottom
and Figures S3 and S4 in the Supporting Information).
Host molecule 4 is capable of forming complexes with
halide species in solution. The interaction pattern is, howev-
er, different from those observed in the solid state. Since
cage molecule 4 gave no fluorescence emission under ir-
Figure 3. X-ray structure of complex of 4 with tetraethylammonium bro-
mide and water (50% probability). Selected distances (in ꢁ): O4···tria-
À
zine plane 2.892, O4···Br1 3.392, Br1···triazine plane 3.516, Br2 triazine
plane 3.429, O4···Br1 3.421, Br1···Cl1 3.492, Cl2···triazine plane 3.284,
Cl3···C7 3.301, C12···C7 9.474, C7···C10 9.077, C10···C12 8.853. Cations
and hydrogen atoms are omitted for clarity.
V-shaped clefts of different sizes (dCl1 Cl2 =11.955, dCl1
=
À
À
Cl3
12.710, dCl2 Cl3 =11.673 ꢁ). In the smallest cleft, Br2 ion was
À
in close contact with one of the triazine rings. The distance
of Br2 to the plane and to the centroid of triazine ring is
3.429 ꢁ (Figure 3, bottom) and 3.480 ꢁ, respectively, indi-
cating a strong p-bromide interaction. There was no other
Chem. Eur. J. 2010, 16, 13053 – 13057
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
13055

D.-X. Wang, Y. Wang, M.-X. Wang et al.
A
order of fluoride (361mÀ1), chloride (146mÀ1) and bromide
(95mÀ1). Moreover, the values of enthalpy changes of the
complexion were all exothermic. Especially for the complex-
ion of cage molecule 4 with fluoride, the enthalpy change
was significantly exothermic, while the entropy change had
a large negative value, indicating the complexion of cage
molecule 4 with fluoride is an enthalpy-driven process.
changes upon titration of tetrabutylammonium chloride or
bromide; the interaction of host molecule 4 with halides in
solution was then studied by means of isothermal titration
calorimetry (ITC).[8] Pleasingly, ITC provided a very power-
ful method for detecting the anion–p interaction in solution.
As illustrated in Figure 4 (and Figures S5–S8 in the Support-
Although water molecules were found to participate in
the formation of anion–p complexes in the solid state (supra
vide), the presence of water in solution did not enhance the
association of the host molecule with the halide guest. In
comparison with the result listed in Table 1, for example,
ITC study gave a slightly decreased association constant
(Ka =101mÀ1) between 4 and tetrabutylammonium chloride
when water was added (see Figure S7 in the Supporting In-
formation). It indicated the different mechanisms of forming
complexes in solution and in the solid state. Indeed, our fur-
1
ther study, by means of diffusion H NMR spectroscopy, re-
vealed that the host cage molecule 4 and tetrabutylammoni-
um chloride formed a complex in solution, while water was
not involved at all (see Figure S9 in the Supporting Informa-
tion). The variation of the association constant in the ab-
sence and in the presence of added water was probably due
to the solvating effect of water on the tetrabutylammonium
chloride guest.
It should be noted that the interaction between cage mol-
ecule 4 and various halide ions in solution does not originate
from the hydrogen-bonding effect. We carefully measured
the H and 13C NMR spectra of the host molecule upon ti-
tration of halides, but no shifts of proton and carbon signals
were observed at all (see Supporting Information). The
1
Figure 4. Microcalorimetric titration curve of host 4 with tetrabutylam-
monium fluoride in acetonitrile at 258C. Raw data for sequential injec-
tions of fluoride solution (6 mL, 96.7 mm) into host solution (5 mm; upper
panel). Net heat effect of host 4 interacting with tetrabutylammonium
fluoride obtained by subtracting the heat of dilution (dotted line) and the
fitted heat effect (red line; lower panel).
NMR titration studies showed convincingly that there is no
À
À
Ar H···X hydrogen-bonding interaction between host and
halide ions in solution. The interaction of host molecule 4
with chloride and bromide in solution was also evidenced by
the observation of [4ꢀCl]À and [4ꢀBr]À ion peaks in ESI
mass spectra (see Figure S17 and S18 Supporting Informa-
tion) when 4 was treated with tetrabutylammonium chloride
and bromide, respectively. Additionally, ion peaks corre-
sponding to [4ꢀBu4NXꢀX]À and [4ꢀ2X]À (X=Cl and Br)
were also observed, indicating the formation of multiple
component complexes between host and guest under mass
spectrometry conditions.
ing Information), the heat of interaction of cage molecule 4
with halides was observed after each injection. With the ad-
dition of the guest, the observed heat decreases gradually
and finally tends to zero. The net heat effect of cage mole-
cule 4 binding with halides was obtained by subtraction of
the heat of the guest dilution, and the thermodynamic pa-
rameters (Table 1) were calculated on the basis of fitting the
ITC curves. The thermodynamic results indicated that the
cage molecule 4 formed approximately 1:1 complex with tet-
rabutylammonium halides. The binding constant was in the
In summary, we have shown that bis(tetraoxacalix[2]-
AHCTUNGTREGaNNUN rene[2]triazine) 4, a conformationally rigid cage molecule
with three V-shaped electron-deficient clefts, was able to in-
teract with halides. On the basis of ITC study, it formed 1:1
complex with fluoride, chloride, and bromide in acetonitrile,
giving binding constants of 361, 146, and 95mÀ1, respectively.
In the solid state, the triazine ring formed a weak s complex
with chloride, an h3 complex with bromide, and p–lpe inter-
actions with a water guest molecule. Different anion–p in-
teractions along with hydrogen bonding, halogen bonding,
and lpe–p interactions directed the formation of different
molecular assemblies. The design of the host molecules for
selective anion binding based on unique anion–p interac-
tions are under further investigation in our laboratory.
Table 1. Binding constants (Ka) and standard Gibbs energy (DG8) en-
thalpy change (DH8) and entropy changes (DS8) for the complex between
4 and halides in acetonitrile.
Guest[a]
n[b]
Ka
[mÀ1
DG8
[kJmolÀ1
DH8
[kJmolÀ1
DS8
[c]
G
]
G
]
G
]
[JmolÀ1 KÀ1
]
1
2
3
FÀ
1.3
1.2
1.2
361
146
95
À14.6
À12.3
À11.3
À207.2
À11.0
À6.6
À646.0
4.4
15.8
ClÀ
BrÀ
[a] All as tetra-n-butylammonium salts. [b] Stoichiometry given by a fit-
ting program. [c] T=298.15 K.
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Host–Guest Chemistry
COMMUNICATION
2006, 128, 14788; c) B. L. Schottel, H. T. Chifotides, M. Shatruk, A.
Chouai, L. M. Pꢃrez, J. Bacsa, K. R. Dunbar, J. Am. Chem. Soc.
2006, 128, 5895; d) G. Gil-Ramꢄrez, E. C. Escudero-Adꢅn, J. Benet-
Buchholz, P. Ballester, Angew. Chem. 2008, 120, 4182; Angew.
Chem. Int. Ed. 2008, 47, 4114; e) O. B. Berryman, A. C. Sather, B. P.
Hay, J. S. Meisner, D. W. Johnson, J. Am. Chem. Soc. 2008, 130,
10895; f) M. Albrecht, C. Wessel, M. De Groot, K. Rissanen, A.
Lꢆchow, J. Am. Chem. Soc. 2008, 130, 4600.
Experimental Section
Preparation of 3: A mixture of phloroglucinol 1 (0.63 g, 5 mmol) and
DIPEA (2.42 g, 18.8 mmol) in THF (30 mL) was added dropwise over a
period of 20 min to an ice-cooled and well-stirred solution of cyanuric
chloride 2 (4.15 g, 22.5 mmol) in THF (50 mL). The resulting mixture,
which contained the precipitates formed from the reaction, was kept
ACHTUNGTRENNUNGstirring for another 3 h at 08C. After filtration and concentration, the res-
[5] a) Y. S. Rosokha, S. V. Lindeman, S. V. Rosokha, J. K. Kochi,
Angew. Chem. 2004, 116, 4750; Angew. Chem. Int. Ed. 2004, 43,
4650; b) D.-X. Wang, Q.-Y. Zheng, Q.-Q. Wang, M.-X. Wang,
Angew. Chem. 2008, 120, 7595; Angew. Chem. Int. Ed. 2008, 47,
7485.
idue was subjected to chromatography on a silica gel (100–200 mesh)
column eluting with a mixture of petroleum ether and acetone. Pure
product 3 was obtained as a white solid (yield: 75%). M.p. 240–1428C;
1H NMR (CDCl3, 300 MHz): d=7.17 ppm (s, 3H); 13C NMR (CDCl3,
75 MHz): d=173.5, 170.4, 151.7, 113.8 ppm; IR (KBr) n˜ =1613,
1530 cmÀ1; MS (EI): m/z (%): 573 (4), 571 (8), 569 (10), 567 (5) [M]+,
538 (17), 537 (10), 536 (57), 535 (12), 534 (100), 533 (10), 532 (57); ele-
mental analysis calcd (%) for C15H3N9O3Cl6: C 31.63, H 0.53, N 22.12;
found: C 31.74, H 0.84, N 22.22.
[6] H. Schneider, K. M. Vogelhuber, F. Schinle, J. M. Weber, J. Am.
Chem. Soc. 2007, 129, 13022.
[7] For recent reviews, see: a) M.-X. Wang, Chem. Commun. 2008,
4541; b) W. Maes, W. Dehaen, Chem. Soc. Rev. 2008, 37, 2393; c) H.
Tsue, K. Ishibashi, R. Tamura, Top. Heterocycl. Chem. 2008, 17, 73.
[8] F. P. Schmidtchen, Isothermal Titration Calorimetry in Supramolec-
ular Chemistry in Analytical Methods in Supramolecular Chemistry
(Ed.: C. Schalley), Wiley-VCH Weinheim, 2007, pp. 55–78.
[9] Crystallographic data for 4 (C21H6Cl3N9O8): Mr =618.70, trigonal,
Preparation of cage molecule 4: Solutions of 1 (0.126 g, 1 mmol) in ace-
tone (50 mL) and 3 (0.57 g, 1 mmol) in acetone (50 mL) were added
dropwise at the some rate to a solution of DIPEA (0.464 g, 3.6 mmol) in
acetone (100 mL) over a period of 4 h at room temperature. After addi-
tion, the resulting mixture was kept stirring at room temperature for an-
other 2.5 days. The solvent was removed and the residue was subjected
to chromatography on a silica gel (100–200 mesh) column eluting with a
mixture of petroleum ether and acetone. Pure cage molecule 4 was ob-
tained as a white solid (yield: 35%). M.p. >3008C; 1H NMR (CDCl3,
300 MHz): d=6.69 ppm (s, 6H); 13C NMR (CDCl3, 75 MHz): d=175.1,
172.7, 153.1 ppm; IR (KBr) n˜ =1614, 1550 cmÀ1; MS (EI): m/z (%): 591
(4), 590 (28), 589 (28), 588 (19), 587 (96), 586 (22), 585 (100) [M]+; HR-
MS: m/z calcd for C21H6N9O6Cl3: 584.9507; found: 584.0513.
¯
space group R3c, a=11.3135(16), b=11.3135(16), c=36.700(7) ꢁ,
a=90.00, b=90.00, g=120.008, V=4068.1(11) ꢁ3, T=293(2) K,
full-matrix least-squares refinement on F2 converged to RF =0.0630
[I>2s(I)], 0.0750 (all data) and Rw(F2)=0.1864 [I>2s(I)], 0.1962
(all data), goodness of fit 1.086. CCDC-734866 contains the supple-
mentary crystallographic data for this paper. These data can be ob-
tained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
[10] Crystallographic
data
for
complex
[4ꢀ
(Et4NCl)3ꢀ
ACHTUNGTRENNUNG(H2O)3]
¯
(C45H72Cl6N12O9): Mr =1137.85, trigonal, space group R3, a=
20.5900(3), b=20.5900(3), c=24.9772(5) ꢁ, a=90.00, b=90.00, g=
120.008, V=9170.4(3) ꢁ3, T=173(2) K, full-matrix least-squares re-
finement on F2 converged to RF =0.0659 [I>2s(I)], 0.0712 (all data)
and Rw(F2)=0.1367 [I>2s(I)], 0.1392 (all data), goodness of fit
1.312. The diffuse electron density due to the disordered and un-
identified moieties was treated with SQUEEZE routine within the
PLATON software package (P. van der Sluis, A. L. Spek, Acta Crys-
tallogr. Sect. A 1990, 46, 194). CCDC-734868 contains the supple-
mentary crystallographic data for this paper. These data can be ob-
tained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
Acknowledgements
We thank the National Natural Science Foundation of China (20875094,
20672115, 20532030), Ministry of Science and Technology
(2007CB808005), Chinese Academy of Sciences for financial support. We
also thank Dr. X. Hao and T.-L. Liang for X-ray structure determination
and Dr. J.-F. Xiang for NMR measurements and discussions.
[11] Crystallographic
data
for
complex
[4ꢀ(Et4NBr)2ꢀH2O]
G
Keywords: anions
· calixarenes · halides · host–guest
(C37H48Br2Cl3N11O7): Mr =1025.03, monoclinic, space group C2m,
a=23.483(5), b=16.693(3), c=13.011(3) ꢁ, a=90.00, b=117.10(3),
g=90.008, V=4540.4(20) ꢁ3, T=173(2) K, full-matrix least-squares
refinement on F2 converged to RF =0.0546 [I>2s(I)], 0.0984 (all
data) and Rw(F2)=0.0853 [I>2s(I)], 0.0936 (all data), goodness of
fit 1.081. The diffuse electron density due to the disordered and un-
identified moieties was treated with SQUEEZE routine within the
PLATON software package (see reference in [10]). CCDC-734867
contains the supplementary crystallographic data for this paper.
These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/
cif.
systems · molecular assembly · pi interactions
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Received: August 12, 2010
Published online: October 22, 2010
Chem. Eur. J. 2010, 16, 13053 – 13057
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
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