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Hydrogen Bonds as a Crystal Design Element for Organic Molecular Solids with Intermolecular Ferromagnetic Interactions.

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Co" complex is higher, there is also a vibrational entropy
gain. Efforts are ongoing to prepare several more complexes
that exhibit the valence-tautomeric transformation in the
solid state.
Hydrogen Bonds as a Crystal Design Element
for Organic Molecular Solids with Intermolecular
Ferromagnetic Interactions**
By Esteve Hernandez, Montse Mas, Elies Molins,
Concepcid Rovira, and Jaume Veciana*
E.xperimenta1 Procedure
The synthesis of [Co(phen)(3,5-dtbsq),1 is given as a general scheme for preparation ofcobalt complexes containing benzosemiquinone anions as Iigands. All
reactions were carried out under an inert atmosphere of Ar in Schlenkware with
degassed reagent-grade solvents (Aldrich). The starting tetramer [Co4(3,S-dtbsq)J was prepared by a published procedure 1111. and a portion (0.646 g) suspended in 100niL of methylcyclohexane. This reactant and the ligand phen
(0.220 g i n 100 mL of methylcyclohexane) were dissolved in their separate solutions by heating to 100 32.The phen solution was then added dropwise over
30min to the tetramer solution. After half the solution had been added, a
purple microcrystalline precipitate was visible. After the addition was complete,
the solution was stirred for an additional 30 min at 100 "C. Upon cooling.
0.700 g of a purple microcrystalline solid was filtered off. This solid was recrysrallized by dissolving 0.200 gin 100 mL of toluene, filtering hot, and then slowly
evaporating the solution under a steady flow of N,gas. All cobalt complexes
gave good chemical analyses for C, H, N, and Co.
Received: January 25,1993 [Z 5826 IE]
German version: Angew. Cheni. 1993. 105.954
[ l ] D. N. Hendrickson in Mixed Vulenrj Sjxrernst Applicarrons in Chemisrrj,
Ph.ysics and Biology (Ed.: K. Prassides), Kluwer, Dordrecht. 1991,
Chap. 5, pp. 67-90; H. G . Jang, R. J. Wittebort, Y. Kaneko. M. Nakano,
M. Sorai. D. N. Hendrickson, Inorg. Chem. 1992. 31, 2265; M.S.
Mashuta, R. J. Webb, J. K. McCusker, E. A. Schmitt, K. J. Oberhdusen,
J. F. Richardson, R. M. Buchanan, D. N. Hendrickson, J Am. Chem. Soc.
1992, 114, 3815; R. J. Webb, T.-Y. Dong, R. K. Chadha, C. G . Pierpont,
D. N. Hendrickson, ibid. 1991, 113, 4806.
[2] P. Giitlich. Strucrure Bonding IBerlJn) 1981,44,83:P. Giitlich in Chemicul
Mossbuuer Spectroscopy (Ed.: R. H. Herber), Plenum. New York, 1984;
C. N. R &do, Int. Rev. P/ij.rr.s.Chem. 1985, 4, 19; P. Giitlich, A. Hauser.
Coord. Chem. Rev. 1990. 97. 1 ; E. Konig, Prog. Inorg. Chem. 1987. 35,
[3] C. G . Pierpont. S . K. Larson, S . R. Boone, Pure Appl. Chem. 1988, 60.
1331; C. G . Pierpont, R. M. Buchanan. Coord. Chem. Rev. 1981, 38,
[4] 0. Kahn. J. Krobert, C. Jay, Adv. Mafer. 1992, 4, 718; 0.Kahn. J.-P.
Launay, Chemrronics 1988, 3, 140; J.-P. Launay in Molecular Elecrronk
Devices I1 (Ed.: F. L. Carter), Dekker, New York. 1987.
[5] S . Decurtins, P. Giitlich, C. P. Kohler, H. Spiering. A. Hauser Chern. Phjs.
L e t f . 1984, 105. 1 ; P. Giitlich. A. Hauser. Pure Appl Chem. 1989. 61,
[6] R. M. Buchanan, C. G . Pierpont, J Am. Chem. Sue. 1980, 102. 4951.
[7] Crystaldata for 1 . C,H,CH,. C,,H,,CoN,O,
. C,H,, monoclinic, PZ,/c,
u = 10.425(3), h = 32.226(8). I = 13.454(4) A,
= 11l.39(2)",
4208.6(18)A, Z = 4 . ~ , , , , ~ = 1 . 2 1 8 g c m - ~p(MoK,)=4.48cm-',
238 K. Of 4787 data collected (Siemens P4. 4 " 5 28 s 42'). 4552 were
independent, and 2879 were observed (5uFo) The Co atom was located by
direct methods. All atoms were refined as in ref. [8]. R(F) = 0.0489,
R(wF) = 0.0629 1121.
[8] Crystal data for 2: C,,H,,CoN,O,.
orthorhombic, Ccc2. u = 16.233(6),
h = 26.894(10), c = 8.472(2)A, V = 3698.6(13) A'.
Z = 4. eCalcd
1.181 g ~ r n - p(MoKJ
= 5.00cm-'. T = 296 K. Of 1852 data collected
(Siemens P4, 4' 5 28 < 45 ), 1759 were independent. and 1307 were observed (3uFcJ. The noncentrosymmetric space group was chosen (instead
of Cccm) as required by the placement of a chiral trischelate complex on
a special position. The structure was solved intuitively by placing the Co
atom in an arbitrary position on the twofold axis. The correctness of the
reported hand was determined by the refinement of a multiplicative term
(1.11(8)) for AF'. All non-hydrogen atoms were refined with anisotropic
thermal parameters, and hydrogen atoms were treated as idealized contributions. R(F) = 0.0461, R(ivF) = 0.0504 [12]. SHELXTL-PC software
(G. Sheldrick. Siemens. Madison, WI. USA).
191 Y. Kawaiiishi. N. Kitamura. S. Tazuke, Inor<?.Chem. 1989.28.296s- 2975.
[lo] M. W. Lynch, R. M. Buchanan. C. G . Pierpont, D. N. Hendrickson, Inorg.
Chem. 1981, 20. 1038; A. Dei, D Gatteschi, Inorg. Chim. A c f u 1992,
198-200, 813
[ t i ] R. M. Buchanan, B. J. Fitzgerald, C. G. Pierpont, Inorg. Chem. 1979, 18,
[12] Further details of the crystal structures investigations are available from
the Director of the Cambridge Crystallographic Data Centre, 12 Union
Road, GB-Cambridge CB2 1EZ (UK), on quoting the complete journal
f> VCH Verlagsgesellrchafl mhH, W-6940 Weinheim. 1993
Ferromagnetism in purely organic molecular solids has
attracted considerable interest in the last few years."] U p to
now, only three open-shell organic molecules-free radicals
or radical ions-exhibiting such a magnetic property in the
solid state are known.['] In order to obtain this cooperative
property it is necessary not only to choose suitable openshell molecules but also to orient them properly relative to
each other in a three-dimensional network, because ferromagnetism is a three-dimensional p h e n ~ m e n o n . ' In
~ ] these
supramolecular organizations, the correct electronic mechanisms that give rise to the parallel, or ferromagnetic (FM),
spin alignment between neighboring molecules along three
(or two) directions of space must be e ~ t a b l i s h e d .Appropri~~]
ate structural modifications and chemical functionalizations
of stable open-shell molecules represent a promising approach to supramolecular organizations"] in which the natural predilection for antiparallel, o r antiferromagnetic (AF),
spin alignment is avoided.['.41 In fact, the use of crystal design elements provides one of the most direct ways to control
the relative orientations of molecules[61 and, therefore, of
their electronic interactions in crystalline and noncrystalline
solids.[7i Hence, basic studies devoted to the control of crystal packings and, through them, the magnetic properties of
organic molecular solids are in great demand.['I
We report here an example of the nitronyl nitroxide free
radical 1,['I in which hydrogen bonds have been used for the
first time as a crystal design element to obtain a crystalline
supramolecular organization showing intermolecular ferromagnetic interactions.
The study of the radical 1 seemed promising, because this
compound combined a priori most of the structural and
electronic prerequisites to show at least a short-range FM
ordering of hydrogen-bonded molecules: 1) semiempirical
molecular orbital (MO) calculations revealed strong electronic polarizations of NO and OH bonds (N+0.09-0-0.34
and 0-0.27-H +0.24),[91
indicating that the NO groups could
act as acceptors and the O H group as a donor in hydrogen
bonds; 2) the noncollinear relative orientation of NO and
OH groups, together with the strong directionality usually
observed for hydrogen bonds,I71 could favor the formation
in the solid state of a hydrogen-bonded network with a high
dimensionality, and 3) MO calculations based on the UHF
approximation['] showed that 1 fulfilled most of the electronic requirements that were considered relevant for the
[*] Dr. J. Veciana, E. Hernandez, M. Mas, Dr E. Molins, Dr. C. Rovira
Institut de Ciencia de Materials de Barcelona
Campus de la U.A.B., E-08193 Bellaterra (Spain)
[**I This work was supported by the Programa Nacional de Nuevos Materiales
(C.I.C. y T., Grant No. MAT 91/0553). We thank Dr. B. Martinez (Laboratori de Propietats Electriques i Magnetiques. ICMAB) for magnetic
0570-0833:93/0606-1882 S 10.00i .25/0
Angen. Chem. In/. Ed. Engl. 1993, 32, No. 6
of F M couplings in molecular solids, either
through the so-called McConnell I mechanism or the charge
transfer mechanism involving frontier orbitals.[4* ' 21
Radical 1 was prepared by the reported method and was
crystallized from toluene.[131An X-ray structure determination revealed that it crystallizes with two crystallographically
independent molecules A and B in the asymmetric unit,
which are almost identical in structure (Fig.
Fig. 1 Molecular structure of the conformer A of 1 showing the atomic numbering scheme. Selected interatomic distances [A] and angles ["I (standard deviations in parentheses) [and for conformer B, in square brackets]: H1-01 1.04(4)
[1.08(4)]. 01-C2 1.36014) [ 1.368(4)], C5-CS 1.452(4) [1.445(4)], C8-N9 1.362(4)
[1.330(4)]. N9-010 1.274(3) [1.289(3)], C8-Nl3 1.340(4) [1.360(4)], N13-014
1.283(3) [1.275(3)], 010-N9-C8 125.0(2) [126.1(2)], N9-CS-Nl3 107.3(2)
[107.0(2)], C8-N13-014 127.0(2) [126.5(2)], H1-01-C2 116.(2) [107.(2)].
Fig. 2. Packing of radical I in the unit cell. a) 2-D hydrogen-bonded network
of molecules with A conformation viewed along the c axis. b) Packing along the
c axis. The 2-D networks labeled 1 comprise molecules with A conformation
and those labeled 2 with B conformation. The 2-D network 1' (and 2') is related
to network 1 (and 2) by the twofold screw axis parallel to the c axis. Selected
hydrogen bond distances [A] and angles ["I (standard deviations in parenthesis)
of 0 - H ..' 0 and C-H ... 0 types (unprimed and primed figures refer to molecular conformations A and B, respectively); symmetry code. (i) s,.;.:;(ii)
-O.S+x-y,z;(iii) - 0 S + x , l -).,z;(iv)0.5+x,l -y,z:(v)0.5+~,-?..;;
all distances and angles fulfill the geometrical requirements of hydrogen bonds
[7]): H1"' . . . 014"" 1.65(4), H(1')''' . . O(l0')'"'' 1.61(4), H( 113)"). . 0(
H(122)"'... O(10)'"'
H(116)"'... O( 14')'''
H( 121')"' . ' O(14)"' 2.45(3), 011)-€I(
1)"' .. . O( 14)"" 165.( 1) ; O( 1')-H( 1')"'O(10)""'
C(111)-H( 113)('i. ' . O(10)'"'
168 (3),
C( 121)H( 122)"' ... O( 10)"" 167.(2), C( 112')-H(116)"' .. . O( 14')"' 159.(3), C( 121')H(121')('' .. .0(14')"' 163(3).
phenyl rings in both molecules are almost coplanar with the
showed an exchange-narrowed single line with a pure
OH groups, but form angles of 32.7(1) and 33.6(2)' with the
Lorentzian line shape whatever the orientation of the crystal.
plane of the sc-nitronyl nitroxide 0-N-C-N-0 grouping. The
This behavior is characteristic of exchange coupling in 3-D
crystal packing of radical 1 is shown in Figure 2. Unexpectspin systems.['7] Static magnetic susceptibility data were coledly only one of the two NO groups forms strong hydrogen
lected o n a SQUID magnetometer in the 1.8 2 T <_ 250 K
bonds with the OH groups of neighboring m o l e c ~ l e s . ~ ' ~ ~ temperature range at an applied magnetic field of 10 kOe for
Such hydrogen bonds exist between molecules with identical
a 20 mg sample consisting of several crystals of 1. Paramagconformations and give rise to zigzag chains along the a axis
netic SusceptibiIities are shown in Figure 3. Above 5 K, the
(see Fig. 2a). Each one of these chains meshes with the transdata obey the Curie-Weiss law, xp = C/(T - O), where
lationally related chains along the b axis. The meshing occurs
C = 0.379 emuKmol-' and 8 = +0.8 K. The high temperthrough interactions between the 0 atoms of the free NO
ature value of xJ(O.37 emuKmol-') is close to that expectgroups of one chain and the H atoms belonging to vicinal
ed (0.376) for noninteracting S = 1/2 units, with g = 2.006.
CH, groups of neighboring chains. Such C-H ' ' ' 0interacBelow 50 K, x,Tincreases continuously with decreasing temtions have the crystallographic requirements to be conperature, reaching 0.48 emu K mol- ' a t 1.8 K. Such a large
sidered as weak hydrogen bonds.[71Moreover, spectroscopic
value is a clear indication of the existence of intermolecular
F M interactions in 1. Below 5 K, paramagnetic susceptibility
evidence supports this description." Thus, two-dimensiondata gradually deviate downwards from the Curie-Weiss
al hydrogen bonded networks, parallel to the ab plane, are
present in the crystal structure of 1 (see Fig. 2a). Such 2-D
curve (Fig. 3a) extrapolated from the data at high temperanetworks are, in addition, closely packed along the c axis
tures. A much better fit of the experimental data is obtained
with intermolecular contacts ranging from 3.5 to 4.0 fi (see
over the whole temperature range of 1.8-250 K with the
Fig. 2 b). The most relevant feature observed from all the
theoretical curve (Fig. 3 a) calculated from the ferromagnetic
short contacts of this densely packed structure is the absence
I - D Heisenberg model['81 with an intrachain coupling of
of significant intermolecular overlaps between SOMOs,
J / k = +0.49 K and S = lj2. Therefore, this result suggests
which are usually considered responsible for A F interactions
that the F M coupling within a chain is dominant. Unfortuin molecular solid^.[^^ In fact, both within and between the
nately, the rest of the magnetic interactions in this spin sys2-D molecular sheets only short contacts that are generally
tem are too weak to be observable at temperatures higher
claimed as the origin of intermolecular F M interactions are
than 1.8 K with this static technique.
observed." 61 Therefore, these local structural features sugThe field dependence of the magnetization of 1 is also
gest the possibility of F M interactions with distinct intensishown in Figure 3 at several temperatures, together with the
ties along the three spatial axes.
theoretical curve for an ideal paramagnet with S = 1/2 and
The presence of three-dimensional magnetic interactions
g = 2.006. It is clear that radical 1 magnetizes more rapidly
in 1 was supported by single-crystal electron spin resonance
than an ideal paramagnet and also that the magnetization
(ESR) experiments at room temperature. These experiments
curve is steeper when the temperature is lowered. This is
Angew. C h m . lnr. Ed. Engl. 1993. 32, No. 6
VCH ~~rlugsgesells~lzuft
mhH, W-6940 Weinheim, 1993
OS70-0833i93jO606-0883$ 10.00+ ,2510
- -
G .G
HIT [kOelK]
Fig. 3. a) Left: Temperature dependence of the paramagnetic susceptibility x,,
[emu mol-'1 of 1. Thedashed linerepresents the fit oftheexperimentaldata (see
the text) to the Curie-Weiss law and the solid line the tit to the ferromagnetic
1-D Heisenberg model. Right: The plot of the product ,y,T[emu kmol-'1 versus
T. b) Field dependence of the magnetization M [wB per molecule] of 1 at 2 ( o ) ,
3 (A). and 8 ( 0 ) K, measured in the applied magnetic field range 0.1 s H 5
58 kOe.
further evidence of the presence of intermolecular FM interactions in this spin system, which is in full agreement with the
susceptibility results. The magnetic behavior described
above is very similar to that recently reported for the phase
of an analogous nitronyl nitroxide bearing NO, substituents
instead of the OH groups, which undergoes a transition to a
bulk ferromagnetic ordered state below 0.65 K.['"*I ' ' It is
therefore important to extend the magnetic measurements
with 1 at low temperatures to the mK region in order to
determine the nature of all the operative intermolecular magnetic interactions and to check whether a long-range ferromagnetic ordering occurs. Such experiments are in progress.
We have shown above that the establishment of hydrogen
bonds between open-shell molecules is a suitable strategy for
preparing molecular solids with a high dimensional organization. Our work culminated in a case where ferromagnetic
intermolecular interactions have been achieved.
Received: December 10, 1992 [Z8748 IE]
German version: A n g w . Chem. 1993, 105. 919
[I] Recent overviews: a) M u / . C r w Liq. CrJrt. 1989. 176, 1-562; b) Muter
Rrs. Soc. Symp. Proc. 1990. 173, 3-92: c) Molecular Mugnetic Muleriul.7
(Eds.: D. Gatteschi. 0.
Kahn, J. S. Miller, F. Palacio), Kluwer. Dordrecht.
[2] a ) H. Tamura, Y. Nakazawa. D. Shiomi, K. Nozdwa. Y. Hosokoshi, M.
Ishikawa, M. Takahashi. M. Kinosbita, Cheni. Pliys. Lett. 1991, 186,401;
b)P.-M. Allemand, K. C. Khemani, A. Koch, F. Wudl, K. Holczer, S .
Donovan, G . Gruner. J. D. Thompson, Science 1991, 253. 301; c) R .
J? VCH Verlag.~g~~scll.~chu/t
mbH, W-6940 Weinheim,1993
Chiarelli, A. Rassat. P. Rey, J. Chem. Soc. Clzem. Commun. 1992, 1081; A.
Rassat, Mol. C r w . Liy. C r w . , in press.
[3] Ferromagnetism may be two-dimensional in some rather exceptional conditions, but it is never one-dimensional. See: R. L. Carlin. Magnerochemisrry, Springer, Berlin, 1986; F. Palacio in ref, [l c], pp. 1 --34.
141 For the different mechanisms of ferromagnetic couplings in molecular
solids derived from free radicals see: a j H. Iwamura, Adi,. PhJ.7. Org.
Ckein. 1990. 26, 179, b) C.Kollmar, 0. Kahn. A x . Chein. Res., in press.
[S] A. Caneschi. D. Gatteschi. L. Pardi, R. Sessoli. Heh. Cliim. Aciu, in press.
[6] Sometimes referred to as crystul engineering toois: substituents, chemical
functions, and structural features giving rise to strong and directional
intermolecular bonds such as hydrogen bonds. chlorinexhlorine bonds,
[71 P. Dauber. A w . Climi. Re7. 1980,13, 105; R. Taylor. 0.Kennard, ihrd
1984, f 7, 320: G . R. Desirdju, C r w u l Engineering: the Design of Orgunic
Solids. Elsevier. New York. 1989; M. C. Etter, Ace. Chem. Res. 1990, 23.
120; J. A. Zerkowski, C. T. Seto. D. A. Wierda, G. M. Whitesides, J. A m .
Cheni. Soc. 1990. 112, 9028; M. C. Etter, J. Phys. Chem. 1991, 95, 4601.
[8] IUPAC name of 1 : ?-(4-hydroxyphenyl)-4,4,5,5-tetramethyl-4,S-dihydro1 H-imidazolyl-1-oxy-3-oxide.
(91 MO calculations were performed with the MOPAC Version 5.0 package
(QCPE no. 581, J. J. P. Stewart, Department of Chemistry, Indiana University) with MNDO and AM1 methods.
[lo] Such calculations revealed the presence of atoms with positive (NO
groups) and negative (H atoms of the O H and CH, groups) electron spin
densities, as well as a localization of the frontier orbitals in different spatial
regions-the singly occupied molecular orbital (SOMO) is Iocahzed on
both NO groups and the highest doubly occupied MO (HOMO) and the
lowest unoccupied one (LUMO) mainly on the aromatic substituent.
1111 H.M. McConnell, J. Chrm. P h ~ x1963, 39, 1910.
[l?] J. B. Coodenough, Mugnetism und /he Chemical Bond, Interscience, New
York, 1963, p. 167: H. M. McConnell, Proc. R. A . Welch Found. Con/.
Chrm. Res. 1967, If, 144; K.Awaga, T. Sugano. M. Kinoshita. Chem.
Phys. Let/. 1987. 141. 840.
[I31 E. F. Ullman. J. H. Osiecki. D. G. B. Boocock. R. Darcy, J Am. Chem.
Soc. 1972. 94, 7049.
[14] Crystal data: C,,H,,N,O,, orthorhombic, PcuZ,, u =11.765(3), h =
12.726(4), c =17.601(4)& V = 2638(1)A3, Z = 8, eta,.,, =1.26gcm-';
.0 7107 A), graphite monochromator;
Enraf-Nonius CAD-4, Mo,, (i=
T = 293 k 3 K ; measuring range: 2.0 < 20 < 5 0 : 8023 measured reflections, 2647 unique reflections, 1978 reflections with F > lo(F). The structure was solved by using direct methods (MULTAN82 package); the full
matrix refinement on F (MoLEN package) converged a t R = 0.084,
Rw = 0.044. Further details of the crystal structure investigation are available on request from the Director of the Cambridge Crystallographic Data
Centre. 12 Union Road, GB-Cambridge CB2lEZ (UK), on quoting the
full journal citation.
[18] The 0-H and C-H stretching vibrations corresponding to the OH and
CH, groups of radical 1 in the dilute solution (CCI,) and solid state (KBr)
IR spectra have striking differences. For both vibrations, when solid-state
hydrogen bonds form their stretching frequencies decrease. See ref. [7].
[16] It is thought that short contacts between atoms with positive and negative
spin densities as well a s intermolecular overlaps between SOMO-HOMO
and SOMO-LUMO lead to FM intermolecular interactions. See refs. [4.
11, 121.
[17] R. Kubo, Lecture.c in Theoretical Physics, Interscience, New York, 1959.
p. 120; A. Bencini, D. Gatteschi, EPR uf Exchunge Coupled Sq'slems,
Springer. Berlin, 1990, p. 135ff.
[IS] D. D. Swank, C. P. Landee. R. D. Willet, P h n . Re>,.B 1979, 20. 2184.
[19] Y. Nakazawa. M. Tamura, N. Shirakawa, D. Shiomi. M. Takahashi, M.
Kinoshita, M. Ishikawa, Phys. Rev. B 1992, 46. 8906.
A Two-Dimensional Ice with the Topography
of Edge-Sharing Hexagons Intercalated between
CdNi(CN), Layers
By Ki-Min Park, Reikn Kumda, and Toschitake Iwamoto*
The topography of two-dimensional ice, that is, a two-dimensional network of H,O molecules in the solid state, is
related to the connection mode for 0 atoms participating in
the network. The hydrogen-bonded network of the H,O
Prof. Dr. T. Iwdmoto, Dr. K.-M. Park, Prof. Dr. R. Kuroda,
Department of Chemistry, College of Arts and Sciences
The University of Tokyo
Komaba, Meguro, Tokyo 153 (Japan)
Tekfax: Int. code + (813j3488-2904
0570-0833/93i0606-0KRI$ 10.00f ,2510
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