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Cluster Assembly by Hydrogen Bonds Channel Structure of Cu4L4 Cubanes.

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[12] For recent reviews on TADDOL-mediated reactions, see: a) M.Braun,
Angew. Chem. 1996,108,565-568; Angew. Chem. In?. Ed. Engl. 1%. 35,
519-522; b) R. Dahinden, A. K. Beck, D. Seebach in Encyclopedia of
Reagents for Organic Synthesis, Vol. 3 (Ed.: L. Paquette). Wiley, Chichester,
1995, pp. 2167-2170: c) R. 0. Duthaler, A. Hafner, P. A. Alsters, P. RotheStreit. G. Rihs, Pure Appl. Chem. 1992,64,1897 - 1910; d) K. Narasaka, ibid.
1992.64, 1889- 1896.
[13] Crystallographic data (excluding structure factors) for the structure
reported in this paper have been deposited with the Cambridge Crystallogrphic Data Centre as supplementary pubIication no. CCDC-100453.
Copies of the data can be obtained free of charge on application to The
Director, CCDC. 12 Union Road, Cambridge CB21EZ. UK (fax: Int.
code + (1223)336-033; e-mail: deposit@chemcrys.cam.ac.uk).
Cluster Assembly by Hydrogen Bonds:
Channel Structure of Cu4L, Cubanes
Hiroki Oshio," Yuki Saito, and Tasuku Ito
Supramolecular chemistry of coordination compounds and
organic solids is the subject of intense research.[*]It has been
known for several years that self-assembly through hydrogen
bonds leads to well-organized organic and inorganic supramolecular structures, and that channel structures, which are
formed by self-assembly, can be applied in areas such as
selective enclathration, microporosity, and catalysis.[*]On the
other hand, transition metal complexes with a cubane
structure, in which four metal ions are linked by hydroxo,
alkoxo, azido, sulfido, or iminato bridges,f3I are a very
important class of compounds (M4L4).I4] Among them,
alkoxo-bridged copper(I1) cubanes, many of which exhibit a
quintet ground state because of weak intracluster ferromagnetic interactions, have been extensively studied from magneto-structural viewpoints.L51We report here that introduction
of a hydroxy group into the bridging ligand of a cubane core
leads to the formation of a hydrogen-bond network with a
channel structure.
The reaction of copper(I1) acetate monohydrate with
H,hase (2-(4-hydroxysalicylidenearnino)ethanol)in methanol
followed by the recrystallization in acetonitrile gave dark blue
crystals of 1,. which crystallize in the monoclinic space group
Figure 1. Crystal structure of 1 (ORTEP diagram; ellipsoids at the 50%
probability level). Selected distances [A] and angles with standard deviation in
parentheses: C u l - 0 1 1.894(3), C u l - 0 2 1.959(3), Cu1-02'2.467(3), C u l - 0 5 '
1.956(3), C u l - N l 1.925(4), Cu2-02 1.930(3), C u 2 - 0 4 1.939(3), Cu2-05'
2.562(3), CuZ-NZ 1.914(4), Cu2-05 Z.OOO(3); Cul-02-Cul' 101.5(1), Cul-02Cu2 106.1(1), Cu1'-02-Cu2 90.1(1), Cul-O5'-Cu2 85.8(1), Cul-O5'-Cu2'
104.8(1),Cu2-05-Cu2',104.2(1); key to symmetry operation for primed atoms:
1 - X , y, 312 - Z.
The cubane core of 1 is based on an approximately cubic
array of alternating copper and oxygen atoms. The intracluster metal-metal separations are 3.108(1) (Cul ... C U ~ ) ,
3.443(1) (Cul ... Cul'), 3.134(1) (Cul ... C U ~ ' ) , and
3.6154(9) A (Cu2...Cu2') . Each copper atom resides in a
square pyramidal coordination environment with one nitrogen and two oxygen atoms from the ligand and two oxygen
atoms from neighboring units of the cubane. According to the
four short and one long bond lengths (see Figure 1) between
the copper and coordinating atoms, basal planes for Cul and
Cu2 are 01-N1-02-05' and 04-N2-05-02, in which the
copper ions are displaced by 0.053(1) and 0.041(1) above
the plane, respectively. The magnetic orbitals (dX2-yZ)
of the
Cul and Cu2 ions, which are perpendicular to each other, are
parallel to the basal planes (Figure 2 a).
A
/
HO
C ~ / C . The
[ ~ I structure of 1 contains a tetranuclear cubane core
(Figure l), which sits on a crystallographic twofold axis that
passes through the middle of the Cul ..-Cul' and Cu2... Cu2'
vectors. The asymmetric unit, thus, consists of half of the
tetramer.
["I Prof. H. Oshio, Y. Saito. Prof. T. Ito
Department of Chemistry
Graduate School of Science, Tohoku University
Aoba-ku. Sendai 980-77 (Japan)
Fax: Int. code+(22)217-6548
e-mail : oshio@agnus.chem.tohoku.ac.jp
Angew. Chrm. In[. Ed. Engl. 1997,36. No. 23
LJ
Figure 2. a) Arrangement of magnetic orbitals of l, b) magnetlc interactions in 1.
Short bonds are represented by thick lines
In 1, water molecules ( 0 7 ) and hydroxyl groups ( 0 3 and
0 6 ) play an important role in constructing a network
structure of hydrogen bonds; simple translations lead to the
formation of a layer structure in the ac planejn which the
hydrogen bonds are O(7)-H ... 0(1) 2.693(5) A, O(3)-H -..
O(4) 2.710, and 0(6)-H-..O(7) 2.692 A. The additional
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hydrogen bond between the water molecule(07) and the
hydroxyl group (06) requires an offset between successive
layers that is generated by a twofold screw axis. Consequently,
the hydrogen network forms a channel structure along the b
axis (Figure 3 ) .
magnitudes of the magnetic interactions within the
Cul... Cu2 and Cul... C u 2 pairs are considered to be
comparable, because the bridging angles and spacings for
Cul-02-012 and Cul-OS-Cu2 are similar. The two exchange
parameters J 1 and J 2 were, therefore, introduced for the
analysis of the magnetic data and a schematic drawing of the
magnetic pathways is depicted in Figure2b. The experimental magnetic data were analyzed with the Hamiltonian operator 2 [ E q . (l)] and the intercluster interaction was
included as a mean field correction 8. The least squares
calculation yielded the best fit parameters of g = 2.02(1), J, =
- 17.6(1)cm-I, J2 =+36.0(9) cm-I, and $=- 1.0(1) K. The
propagation of intracluster magnetic interactions occurs
according to the known dependence of J versus bridging
angles.['] The magnetic orbital overlap through oxygen porbitals becomes nearly zero for the bridging angles Cul-02Cu2 and Cul-05'-Cu2' of 106.1(1) and 104.8(1)", respectively.[*] Furthermore, the perpendicular arrangement of the
magnetic metal orbitals (Figure 2a) results in zero orbital
overlap leading to ferromagnetic interactions ( J J , while the
parallel orientation results in antiferromagnetic interactions
(Jd.
Figure 3. Channel structure of 1.
The temperature dependence of the magnetic susceptibility
of 1 was measured in the temperature range between 2.0 and
300 K (Figure 4). At room temperature the value of x,T is
Experimental Section
H,hsae (0.138 g, 1 mmol), prepared by condensation of 2,4-dihydroxybenzaldehyde with 2-aminoethanol, was added to a solution of copper(t1) acetate
monohydrate (0. 199 g, 1 mmol) in methanol (80 mL). The resulting dark green
pprecipitate was filtered, and recrystallization in acetonitrile gave dark blue
tabletlike crystals, one of which was subjected to the X-ray structural analysis.
Elemental analysis: found (calcd) C 45.25 (45.13), H 4.62 (4.48), N 9.40 (9.57).
2.4-
1
The present compound is an example of how the introduction of hydroxyl groups can be useful for assembling clusters.
Furthermore, the compound is soluble not only in acetonitrile
but also in water, which indicates that the compound has
potential to clathrate organic molecules while still maintaining its hydrogen-bonding network.
-
2.2
Received: May 26,1997 [Z10473IE]
German version: Angew. Chem. 1997,109,2789-2791
2.0-
Keywords: copper
zmT i emu rnol-'K
- cubanes - self-assembly
1.8-
'71
1.44,
0
,
I
50
100
,
I
I
,
-
150 200 250 300
TIK
Figure 4. Plot of X,Tas a function of T for 1. The solid line was calculated with
the parameters given in the text.
1.8 emuKmol-' per molecule, as expected for four noncorrelated spins. Upon cooling the sample, x,T increases to a
maximum value of 2.44 emu K mol-' at 14 K, then decreases.
This is indicative of an intracluster ferromagnetic interaction,
since the intercluster metal-metal distances are over 7.0 A
these would only give rise to very weak magnetic interactions.
The axial bonds Cul - 02' and Cu2 - 0 5 ' are elongated due to
a pseudo Jahn - Teller effect, which leads to weaker magnetic
interactions within the Cu2 ... CUTand Cul... Cul' pairs. The
2674
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[l] J:M. Lehn, Angew. Chem. 1988,100.91; Angew. Chem. Int. Ed. Engl. 1988,
2789; V. Balzani, Tetrahedron 1992,48, 10443; E. C. Constable, Tetrahedron
1992, 48, 10013; M. J. Zaworotko, Chem. Rev. 1994, 23, 283; Y . L. Chang,
M. A. West, F. W. Fowler, J. W. Lauher, 3. Am. Chem. SOC. 1993, 115, 5991;
J. D. Wright, Molecular Crystals, 2nd ed., Cambridge University Press,
Cambridge, 1994; G. R. Desiraju, Crystal Engineering. The Design of Organic
Solids, Elsevier, Amsterdam, 1989; G. M. Frankenbach, M. C. Etter, Chem.
Muter. 1992,4,272.
[2] K. Endo, T. Sawaki, M. Koyanagi, K. Kobayashi, H. Masuda, Y. Aoyama, J.
Am. Chem. SOC.1995,117,8341;M. Simard, D. Su, J. D. Wuest, ibid. 1991,113,
4696; X. Wang, M. Simard, J. D. Wuest, ibid. 1994,116,12119; B. F. Abraham,
B. F. Hoskins, J. Liu, R. Robson, h i d . 199L 113,3045.
[3] M. A. Halcrow, J. C. Huffman, G. Christou, Angew. Chem. 1995, 107, 971;
Angew. Chem. Int. Ed. Engl. 1995, 34, 889; H. -J. Mai, R. M. Kocker, S.
Wocadlo. W. Massa, K. Dehnicke, ibid. 1995,107, 1349 and 1995, 34, 1235;
M. A. Halcrow, J.4. Sun, J. C. Huffman, G. Christou, Inorg. Chem. 1995,34,
4167.
[4] J. M. Berg, R. H. Holm in Iron-Sulfur Proteins, Vol. 4 (Ed.: T. G. Spioro),
Wiley-Interscience, New York, 1982, Chapter. 1; R. H. Holm, S. Ciurli, J. A.
Weigel, Prog. Inorg. Chem. 1990,38,1.
[5] L. Mertz, W. Haase. J. Chem. SOC.Dalton Trans. 1978,1594; L. Schawabe, W.
Haase, ibid. 1985, 1909; J. W. Hall, W. E. D. Estes, R. P. Scaringe, W. E.
Williams, Inorg. Chem. 1977, 16, 1572; J. Sleten, A. Sorensen, M. Julve, Y .
Journaux. ibid. 1990.29,5054.
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Angew. Chem. lnt. Ed. Engl. 1997,36, No. 23
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~
[6] Crystal data of 1 (C,H,2Cu,N,0,,):
dark blue tablet (0.2 x 0.2x0.3 m d ) ,
M,=1171.13, monoclinic C2lc with a=25.355(4), b=9.211(4), c =
21.460(3) p\, @ = 98.23(1)", V = 4960(2) A3 (by least-square refinement of 20
reflections (25" < 28 < 30")). Z = 4, pdd = 1.568 g ~ m - ~F(oo0)
,
= 2399,
p(MoKo)= 17.73 cm-'. Data collection: Rigaku AFC5S diffractometer, w-28
made, scan width 1.45 + 0.40tan0, scan speed 4"min-', M%, (d =0.71073 A)
radiation; T= - 120°C; 4325 reflections measured(3" < 28 < 55"), 4325
unique reflections, of which 3519 (Io > 3.001,) were used for the calculation.
Data were corrected for Lorentz and polarization and an empirical
absorption correction (*-scan) was applied, which resulted in transmission
factors ranging from 0.575 to 0.760. The structure was solved by a conventional heavy-atom method and refined by full-matrix least-squares by using
Xtal 3.2 (XTAL 3.2 Useis Manual, The University of Western Australia and
Maryland). All non-hydrogen atoms were readily located and refined with
anisotropic thermal parameters, and hydrogen atoms were located from
difference Fourier maps and refined with isotropic thermal parameters. Final
R = 0.040, R, = 0.032 for 316 parameters The final Fourier difference
synthesis showed minimum and maximum peaks of - 0.77 and + 0.67 e A3.
[7] W. E. Hatfield in Magneto-Stnrctural Correlations in Exchange Coupled
systems (NATOASI Ser. Ser. C 1985,140), p. 555.
[8] P.J. Hay, J. C. Thibeault, R. Hoffman, 1. Am. Chem. SOC. 1975, 97, 4884.
Synthesis of a Small-Pore Microporous
Material Using a Computationally Designed
Template**
Dewi W. Lewis,* Gopinathan Sankar, Joanna K. Wyles,
John Meurig Thomas,* C. Richard A. Catlow,* and
David J. Willock
The ability to design and synthesize materials, with
predetermined physical and catalytic properties is an oftaspired goal of the chemist. Recent progress has demonstrated how this may well be viable in the field of microporous
solids, particularly in the case of syntheses mediated by the
Here we demonstrate
use of structure-directing template~.I'-~I
how we are able to design, using computational methods, an
organic template suitable to form a targeted microporous
material, which results not only in the formation of that
crystalline structure, but also manifests a number of other
predefined physical properties.
Microporous materials, both aluminosilicate and aluminophosphate based, with the Chabazite structure (IZA code
CHA) act as catalysts for a number of important reactions.
For example SAPO-34 is an effective catalyst for the
conversion of methanol to light ole fin^.[^] However, there
[*] Dr. D. W. Lewis
Department of Materials Science and Metallurgy
University of Cambridge
Pembroke St, Cambridge CB2 3QZ (UK)
Fax: Int. code + (1223)334567
e-mail: D. W.Lewis@msm.cam.ac.uk
Prof. C. R. A. Catlow, Dr. G. Sankar, 3. K. Wyles, Prof. Sir J. M. Thomas
Davy Faraday Research Laboratory, The Royal Institution of Great Britain
21 Albemarle Street, London W1X 4BS (UK)
Dr. D. J. Willock
Department of Chemistry, University of Wales
Cardiff CFllXL, UK
[**I The EPSRC is thanked for general support of this work, especially a rolling
grant to J.M.T., funding for C.R.A.C. and a CASE studentship to J. K. W.
The Oppenheimer Trust of the University of Cambridge is acknowledged
for a fellowship to D.W.L.
Angew. Chem. Int. Ed. Engl. 1997.36. No. 23
are a number of problems in the synthesis of such materials,
which we believe arise from the choice of the organic species
used as the structure-directing agent. These molecules facilitate the formation of the structure, being encapsulated in the
resulting porous framework ; the framework structure is a
reflection, to varying degrees, of the size and shape of the
organic species. Typically, small amines are used to form the
chabazitic materials (for example, triethylamine, cyclohexylamine, and N,N-diethyl-2-aminoethanol)
.I5] Both experimenand computationallyl6] it is generally noted that two
such molecules can fit inside the CHA
although full
occupancy of all template sites is not a prerequisite of crystal
formation. Such a templating regime requires first relatively
high concentrations of aliovalent metal substituents (either
M2+on AI3+sites or Si4+on P5+sites) as a result of the need to
compensate for the 2 + charge of the protonated templates,
per cage, and second the ordering of the templates in a closepacked configuration which requires relatively slow kinetics.
The latter requirement results in the competitive formation of
other microporous phases where template ordering is not as
effect particularly significant in aluminophoscrucial-an
phate preparations where phases with the A1PO4-5 (AFI)
structure are readily f ~ r m e d . I ~Although
.~]
the presence of
aliovalent metal in the framework gives rise to catalytic
centers, high concentrations can have a deleterious effect on
the stability and performance of the material.
Our aim was therefore to synthesize an aluminophosphatebased material with the CHA structure which, by the use of a
new template, would circumvent the above problems. Such a
template would be designed computationally with our recently developed de novo design
We determined that the following properties would be crucial in our
synthesis strategy: a) The selected template would form a
CHA material quickly and in a phase pure form, with little or
no extraneous microporous phases. b) The template would be
present at a concentration of one molecule per unit cell and
must fully occupy the CHA cage. c) The charge on the
template would be able to be vaned to accommodate a range
of metal concentrations in the framework and thus allow a
degree of control over the catalytic behavior arising from the
presence of these substituents.
Once we had identified a suitable candidate template, a
program of synthesis was undertaken, and the resulting
products were characterized by a combination of XRD and
EXAFS studies.
We applied de novo molecular design methods, as embodied in our ZEBEDDE code,(3]to computationally design a
template to meet the above criteria. The method allows
molecular entities to be grown from a so-called seed molecule,
to which new molecular fragments are added from a library. A
number of actions are possible, which under the control of a
cost function based on van der Waals overlap, minimize the
nonbonded contacts between the framework and the template.[3*'0]Resulting species are subsequently ranked according to their binding energy (a measure of effective fit inside
the pore), which can provide a guide to the likely efficacy of
that molecule as a successful template for the structure in
question.I"]
We performed a number of simulations, described in more
detail elsewhere,[lO]using seeds from C, (methane) to C4
(n-butane). In each case the concentration of the resultant
organic molecule was restricted to one per unit cell (or cage).
Typical templates included branched hydrocarbons and
amines (for example, 3,3,6-trimethyloctylamine and 6-ethyloctylamine) which are similar in structure and geometry to
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