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Controlling Translational Isomerism in [2]Catenanes.

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J. Org. Ch,m 1969, 31. 2703; d ) M . Buchmeiser, H. Schottenberger, J.
Organomi,t. C'hem. 1992,441,457; h i d . 1992, 436,223, and references therein;
e ) G Doisneau. G. Balvoine. T. Fillebeen-Khan, ibid. 1992, 425, 113; f) K .
Schlogl. W. Steyrer, Monutsh. Chrm. 1965, 96, 1520.
171 J. R. Fritch. K. P. C. Vollhardt, J. An?. Chem. Soc. 1979, 100,1239;J. R. Fritch,
K. P. C. Vollhardt. Organomelullics 1982, 1, 580; U . H. F. Bunz, M. Altmann,
Mukromol. Chem. Rupid Commun. 1994, 15, 785.
[8] a) For the synthesis of arylalkynyl polymers through Pd coupling, see, for
example. T. Yamamoto, M . Takagi, K. Kim, T. Maruyama, K . Kubota, H.
Kanbara. T Kurihara, T. Kaino. J. Chem. Soc. Chem. Commun. 1993, 797;
D. L. Trumbo, C. S. Marvel. J. Poljm. Sci. Polym. Chem. Ed. 1986,2411 ; T. X.
Neenan. M R Callstrom, L. M. Scaramontzos, K. R. Stewart. G. M .
Whiteaides. Mucromoledrs 1988,21, 3525; D. R. Rutherford, J. K. Stille. ibid.
1988. 21. 3530; b) Pd-catalyzed coupling of alkynes with alkylhalides: I. P.
Beletskaya. J. Organomrt. Chem. 1983, 250, 551; I. Cassar, ihid. 1975, 93.253;
H. A. Dieck. R. F. Heck, ihid. 1975, 93, 259; K . Sonoshigara, Y Tohda, N.
Haglhara. fiwfihrdrun Lett. 1975. 4467.
191 M . Alami, F Ferri. G. Linstrumelle, Tetruhedron Lett. 1993. 34, 6403.
[lo] D. Demus. L. Richter. Textures o / l i q u i d Cry.sral,s,Verlag Chemie, Weinheim.
[I I ] Powder spectra. Siemens diffractometer D500, Cu,, radiation; distances found
11.2. 7 1. 6.4. 5.1, 4.8, 4.3, and 3.7 A. The reflection corresponding to the 11.2
distance is the most intense and probably represents the Co-Co distance in the
chain The 7.1 distance probably represents the interchain distance.
[12] A "streak" i n the phase diagram is seen in the powder diffractogram as a
pattern of unstructured scattering intensity with a sharp rise at small scattering
angles. Although the integrated intensity of a streak can be very large, it is not
necessarily observable on account of the large signal width.
Controlling Translational Isomerism in
Peter R. Ashton, Llu'isa Perez-Garcia, J. Fraser Stoddart,* Andrew J. P. White, and David J. Williams
The recognition processes that lead to the self-assembly[" of
are controlled by the information stored in the
molecular components which are constructed from "preprogramed" starting materials. This information[31is trapped within the [2]catenanes molecules whose properties are quite different from those of their individual molecular components. The
study of phenomena such as translational isomerism, a structural character is ti^[^] of many of these intriguing molecules,
may provide insight into the recognition processes that operate
during their formation and subsequently in their molecular
states. Furthermore, the control of the translational isomerism
in catenanes is important in demonstrating their chemical properties and for predicting possible application^.[^] Some recent
examples illustrate[,. 'I the progress that has been made already
toward the construction of controllable catenanes and rotaxanes. In our own research laboratory, after the [2]catenane 14 PF, had been self-assembled,[2J the [2]catenane 2-4 PF, was
also synthesizedc8]by a template-directed approach in the belief
that the different n-donating abilities of the 1,5-dioxynaphthalene unit and the hydroquinone ring would influence strongly the relative populations of the rapidly equilibrating transla[*] Prof J. F. Stoddart. Dr. L. Perez-Garcia, P. R. Ashton
School of Chemistry, The University of Birmingham
Edghaston. Birmingham B15 2TT (UK)
Dr. D J. Williams, Dr. A. J. P. White
Chemical Crystallography Laboratory
Department of Chemistry, Imperial College
South Kensington, London SW7 2AY (UK)
This work was supported by the Engineering and Physical Sciences and Engineering Research Councial (UK). We thank the Ministerio de Educatcion y
Cienca (Spain) for a Fleming Postdoctora~Fellowship (to L. P.-G.).
Angcm ('liem In/.Ed. Engl. 1995, 34, No.
tional isomers. In the event, the position of the equilibrium was
found to be highly dependent on the dielectric constant of the
medium in which the [2]catenane was dissolved.
Another way to exercise control over the translational isomerism is by using n-extended viologen units as building blocks
in the construction of interlocked molecular structures. We
recently reported on the self-assembly, characterization, and
electrochemical properties of the [2]catenane 3-4 PF, ,['I in
which the macrocyclic polyether, bis-p-phenylene[34]crown-10
(BPP34C1O), is encircled by a tetracationic cyciophane containing one bipyridinium and one bis(pyridinium)ethylene unit.['' In
the case of 3-4PF6, the translational isomer, in which
BPP34C10 encircles the bipyridinium rather than the bis(pyridinium)ethylene unit, is by far the more predominant one in
CD,COCD, solution at low temperature. This selectivity is a
consequence of the lower n-accepting ability of the n-extended
viologen unit relative to that of the parent viologen unit.
By combining both strategies, that is, by altering the different
binding abilities of both the n-donor and n-acceptor units in
these catenated structures, we should be able to exercise more
control over their translational isomerism. Thus, we have designed and self-assembled a [2]catenane in which all four building blocks, the two z-donor and two n-acceptor units, are different. Here, we describe the synthesis of the [2]catenane 4-4PF,,
which incorporates 1/5NPP36C10, a macrocyclic polyether containing one hydroquinone ring and one 1.5-dioxynaphthalene
unit, as the n-electron rich macrocycle and a tetracationic cyclophane incorporating one bipyridinium and one bis(pyridinium)ethylene unit as the n-electron deficient components. We
report on the characterization of 4-4PF, by fast atom bombardment mass spectrometry (FABMS), X-ray crystallography, and
dynamic 'H NMR spectroscopy.
The [2]catenane 4-4PF6 was self-assembled using a templatedirecting methodology (Scheme 1) .["] The instantaneous formation of a complex between 1/5NPP36C10 and 5-2PF, was
followed by stepwise alkylation of 6 to form the [2]catenane
4-4PF6, which was isolated in 58% yield after counterion exchange and crystallization. The reaction was carried out in
dimethylformamide (DMF) in the dark with an excess of the
macrocyclic polyether. Positive-ion FABMS of this new compound revealed" 'I peaks at m / z = 1567,1422. and 1277 characteristic of the successive loss of one, two, and three PF;
counterions, respectively, from the molecular ion of 4-4 PF, .
0 VCH VerlugsgesellsihaftmhH, 0-69451 Weinlteim, 1995
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The observation of peaks
at m/z = 836 and 690, corresponding to the loss of
one and two counterions,
respectively, from the tetracationic
component of the [2]catenane, is characteristic[”] of
the fragmentations of a
[2]catenane by loss of one
of its rings-in this case,
the neutral crown ether.
The catenated structure
of 4-4PF6 was confirmed
by X-ray crystallography;[’3, L41 suitable single
crystals were grown by vapor diffusion of diisopropyl ether into an acetonitrile solution of the
compound. The major
point to note about the
solid-state structure (Fig. 1)
Scheme 1. The template-directed syntheis that 4-4PF6
sis of the (2lcatenane 4-4PF6
only one isomer. The
macrocyclic polyether is
threaded through the center of the extended tetracationic cyclophane; the 1,5-dioxynaphthalene unit is positioned within the cavity of the tetracationic
ic cyclophane (Fig.
The incorporation of one extended viologen in place of the bipyridinium
unit into one of the sides of the tetracationic cyclophane increases
significantly its overall dimensions
and alters its recognition properties. The length increases from 10.3
to 11.2 A and the width from 6.8 to
The center of the 1,5dioxynaphthalene unit lies closer to
the bipyridinium unit (3.50 A) than
to the double bond (3.72 A) of the
n-extended viologen component
(Fig. 2). In common with 1-4PF6,
the [2]catenane 4-4PF6 forms extended polar stacks in the crystals.
An interesting feature of this stack
is that the double bond of the extended viologen component lies appreciably closer (3.42 A) to the hydroquinone ring of an adjacent
[2]catenane than to the 1,SdioxyFig, 2, Part of the extended
naphthalene unit within the
[2]catenane (3.72 A); indeed the
polar stacks present in the
separation is less than the incrystals of the the [2]catenane
tramolecular distance (3.50 A) be4-4pF*.
tween 1,s-dioxynaphthalene and
the bipyridinium units.
The [2]catenane 4-4PF6 consists of four different n systems,
and therefore an equilibrium between four different translational isomers is possible (Scheme 2). Like [2]catenane 1-4PF6,[’I
the new [2]catenane 4-4 PF, exhibits temperature-dependent
H NMR spectra.[’*] However, the differences in the recognition processes between its components imbue the system with a
high level of structural selectivity. One process (X/X’) is the
equilibration of the n-electron rich hydroquinone ring and 1 3 dioxynaphthalene unit between positions either inside or
alongside the tetracationic cyclophane. In the case of 4-4PF6,
both in CD,COCD, and CD,CN solutions, ’H NMR spectroscopic studies indicate that the circumrotation of 1/5NPP36C10
through the tetracationic cyclophane is already slow on the
Fig. 1. The structure of the [2]catenane 4-4PF6 in the crystal; the additional stabilizing C - H . . . n and C-H . . O interactions are shown.
cyclophane, sandwiched between the n-electron deficient
bipyridinium and bis(pyridinium)ethylene units;[’51 the hydroquinone ring is located outside of the cavity alongside the
bipyridinium component. The molecule has crystallographic C,
symmetry about an axis passing through the centers of the
ethylenic double bond, the 1,5-dioxynaphthalene ring, the
bipyridinium unit, and the hydroquinone ring. The [2]catenane
is stabilized further by a) T-type edge-to-face interactions between the 1,5-dioxynaphthalene and the p-xylyl spacers of the
tetracationic cyclophane,[l6]and b) weak C-H . . .O hydrogen
bonding of the central oxygen atom in each polyether chain with
both a P-xylYl hydrogen atom and One Of the a-CH hydrogen
atoms of the bipyridinium unit, at each “end” of the tetracation
Verlugsgrsellschaft mhH. 0-69451 Weinheim, 1995
Scheme 2. Equilibrium between the translational isomers (I-IV) ofthe [2]catenane
4-4PF, in solution.
0570-083319510505-05723 i0.00+ .25/0
Angew Cllem. Ini. Ed. Engl. 1995, 34, No. J
' H N M R timescale at room temperature, in other words, the
process X/X' is "frozen out" and the aromatic x-electron donors
(hydroquinone and 1,5-dioxynaphthalene) d o not interchange
their positions. The equilibrium (Scheme 2) is predominantly in
favor of the translational isomers I and 11, where the 1,5-dioxynaphthalane ring occupies the position inside the tetracationic
cyclophane. This conclusion may be drawn from the fact that
the ' H N M R spectrum at room temperature in CD,COCD,
shows three well-resolved signals at 6 = 3.77, 5.71, and 6.37
corresponding to the H-4/8, H-3/7. and H-2/6 protons, respectively. of the 1,5-dioxynaphthaIene unit, and one well-resolved
singlet at 6 = 6.08 for the hydroquinone ring protons. None of
the chemical shifts for these signals undergo any changes at
lower temperatures, at least down to -4O"C, indicating that the
two types of aromatic rings do not interchange on the 'H N M R
timescale. At + 40 "C, the four aromatic signals are slightly
broadened, indicating that process X/X' is starting to occur on
the 'H N M R timescale. At this temperature, saturation transfer
experiments led us to identify some low-intensity broad resonances present in the ' H N M R spectrum, corresponding to the
averaged signals resulting from protons in the rapidly equilibrating translational isomers 111 and IV, where the hydroquinone unit is located inside the tetracationic cyclophane.
Thus, irradiation of these weak signals at 6 =7.13 and 7.36,
corresponding. respectively, to H-3/7 and H-4/8 on the
"alongside" 1.5-dioxynaphthalene unit indicated that they are
undergoing exchange with a triplet at 6 = 5.73 and a doublet at
6 = 3.68, corresponding to the same protons on the "inside"
1,5-dioxynaphthalene unit in the rapidly equilibrating translational isomers I and 11. Direct integration of these signals in the
'H N M R spectrum at room temperature, where process X/X'
has already been frozen out, gave an equilibrium ratio of 88: 12
for the translational isomers I and 11 versus 111 and TV. The
second dynamic process (Y/Y' in Scheme 2) exhibited by 4-4PF6
involves pirouetting of 1/5NPP36C10 around the tetracationic
cyclophane. At room temperature, this process is fast on the
' H N M R timescale. However, below - 4 0 ° C it is frozen out
and the major isomer detected is the translational isomer I,
where the x-electron deficient bipyridinium unit is located inside
the tetracationic cyclophane. This is indicated by the relative
simplicity of the ' H N M R spectrum, in which only four major
signals are observed for the a-bipyridinium protons, two doublets, corresponding to the bipyridinium unit, and two doublets,
corresponding to the bis(pyridinium)ethylene unit. This temperature-dependent behavior associated with process Y/Y' was accompanied by changes in the ' H N M R signals arising from all
the protons in the tetracationic cyclophane component of the
[2]catenane. Thus, at - 40 "C, the signal corresponding to the
olefinic protons of the bis(pyridinium)ethylene unit in translational isomer I appears at 6 = 6.60, only A6 = 0.10 downfield
relative to the analogous signal in the room-temperature spectrum. This observation confirms that this signal corresponds to
translational isomer I, where the x-extended viologen resides
alongside the polyether cavity. Once again, a saturation transfer
experiment at - 20 "C showed the existence of site exchange
between a high-intensity signal at 6 = 6.56 (I) and a low-intensity signal at f = 6.15 (11). These signals are associated with site
exchange of the olefinic protons of a bis(pyridinium)ethylene
unit, alongside and inside the macrocyclic polyether. This is
evidence for the population of both translational isomers I and
I1 (Scheme 7). Integration of the signals at - 40 "C gave a ratio
of 95: 5 for isomers I and 11. Neither of the other two possible
isomers (I11 or IV) were detected at this temperature. In solution
at low temperatures [2]catenane 4-4 PF, exists almost exclusively as one amongst four possible translational isomers. This one
. < . / i i v i i . In/.Ed. Engl. 1995, 34, NCI.5
isomer is precisely the same as that observed in the solid by
X-ray crystallography.
The [2]catenane 4-4 PF, shows how the recognition processes
operating between the components of interlocked molecular
systems express themselves in the properties of the moleculesin this case, by controlling translational isomerism. This finding
demonstrates the progress that is being made toward the construction of controllable [2]catenanes.
Experimental Procedure
4-4PF6: A solution of 5 (53 mg, 0.06 mmol) in dry D M F ( 5 mL) was added to a
solution of 11SNPP36C10 (77 mg. 0.13 mmol) in dry D M F (4 mL). A deep red color
was formed immediately, and a solution of 6 (13 mg, 0.07 mmol) in dry D M F
(1 mL) was added. After the reaction mixture had been stirred at room temperature
for 15 d, the suspension was poured in Et,O (50 mL). The red solid was filtered off,
washed with Et,O (10 mL) and CH,CI, (I0 mL). and then dried before being dissolved in H,O (15 mL) and Me,CO (5 mL). Then, a saturated aqueous solution of
NH,PF, was added, and the solution was left to stand for ca. I5 h, during which
time purple crystals formed. The suspension was filtered off, and the crystals were
washed with H,O (2 x 3 mL) and then dried to give 4-4PF6 as a purple solid (65 mg.
5 8 % ) . m.p. b300"C; positive-ton FABMS: mlr: 1567 [ M PF,]+. 1422 [ M 2 P F J C , 1277 [ M - 3PF,]+; ' H N M R (300 MHz. CD,CN): 4 = 3.20-4.30 (m,
32H). 3 . 3 7 ( d . J = 8.0Hz.2H),5.57(dd.J=7.5, 8.0 Hz. 2H). 5.61 (d. J =13.5 Hz,
2H), 5.68 ( s . 4H), 5.80 (d, J = 1 3 . 5 Hz, 2H). 6.09 (s, 4H). 6.10 ( s . 2H), 6.26 (d.
J = 7 5 Hz. 2H). 7.06 (d. 4H), 7.27 (br s. 4H). 7.88 (d. J = 8.5 Hz, 4H), 7.98 (d.
J = X.5 Hz, 4H). 8.73 (br s, 8H).
Received: August 20, 1994 [Z7253IE]
German version: Anyew. Chem. 1995. 107, 607
Keywords: catenanes . crown ethers . self-assembly . translational isomerism
[I] a) J. S. Lindsey. New J. Chem. 1991. 15. 153; b) D . Philp. J. F. Stoddart, Synleft
1991, 445; c) G. M. Whitesides, J. P. Mathias. C. T. Seto, Science 1991, 254.
[2] a) P. R. Ashton, T. T. Goodnow, A. E. Kaifer. M. V. Reddington. A. M. 2.
Slawin. N. Spencer, J. F. Stoddart, C. Vicent, D . J. Williams. Angew. Chem.
1989. I O l . 1404: Angel?. Chem. l n t . Ed. Engl. 1989, 28, 1396; b ) P. L. Anelli,
P. R. Ashton, R. Ballardini, V. Balzdni. M. Delgado. M. T. Gandolfi, T. T.
Goodnow, A. E. Kaifer, D. Philp. M. Pietraszkiewicz. L. Prodi, M. V. Reddington, A. M. Z. Slawin, N. Spencer, J. F. Stoddart, C. Vicent, D. J. Williams.
J. Am. Chem. Soc. 1992, 114, 193. and references therein.
[3] J.-M. Lehn, Science 1993, 260, 1762.
[4] G. Schill. K. Rissler, W. Vetter, Angew. Chrm. 1981,93. 197; Angew. Chem. I n [ .
Ed. Engl. 1981, 20, 187.
[5] a) J. F. Stoddart, Chem. Aust. 1992, 59, 576; b) R. A. Bissrll, J. F. Stoddart in
Compufutionsfor the Nuno-Scale (Eds.: P. E. Biochl, A. J Fisher, C. Joachim),
Kluwer. Dordrecht, 1993, p. 141 ; c) J. A. Preece. J. F. Stoddart in The Ultimate
Limitso/ FubricafionundMrasurrmenf (Ed.: M. Welland). Kluwer. Dordrecht,
1994. in press.
[6] a ) P. R. Ashton, R. A. Bissell, N. Spencer, J. F. Stoddart. M. S. Tolley. Srnlrlt
1992, 914; h) P. R. Ashton, R. A. Bissell, R. Gorski. D. Philp. N. Spencer,
J. F. Stoddart. M. S. Tolley. ibid. 1992, 919; c) P. R. Ashton, R. A. Bissell,
N . Spencer, J. F. Stoddart, M. S. Tolley, ibid. 1992, 923; d ) E. Cordova,
R. A. Bissell. N. Spencer, P. R. Ashton. J. F, Stoddart. A E. Kaifer.
J. Org. Chem. 1993, 58, 6550: e) R. A. Bissell, E. Cbrdova, A. E. Kaifer,
J. F. Stoddart. Nature 1994, 369, 133.
[7] a) F. Vogtle, W. M. Muller. M. Bauer. K. Rissdnen. Angrw Chrm. 1993, 105,
1356; Angen. Chem. I n i . Ed. Engl. 1993, 32, 1295; b) M. J. Gunter, M. R.
Johnston, J Chrm. Soc. Chem. Conmmun. 1994. 829; c) M. J. Gunter, D. C. R.
Hockless, M. R. Johnston, B. W. Skelton, A. H. White. J. A m . Chem. SOC.
1994, fl6, 4810; d) A. C. Benniston. A. Harnman. AngeH.. Chem. 1993, 105.
1553; Angeu.. Chem. I n f . Ed. Enpl. 1993. 32. 1459, e) A . C . Benniston.
A. Harriman, V. M . Lynch. Teiruhedron L e i f . 1994. 35. 1473.
[8] P. R. Ashton, R. Ballardini, V. Balzani. M. Blower, M. Ciano, M. T. Gandolfi,
L. Prodi, C. H . McLean, D Philp, N. Spencer, J. F. Stoddart, M. S. Tolley,
New J. Chem. 1993, 17,689.
[9] P. R. Ashton, R. Balldrdini, V. Balzani, M. T. Gandolfi. D. J.-F. Marquis.
L. Perez-Garcia. L. Prodi. J. F. Stoddart, M. Venturi, J Chmm. SQC.Chem.
Commun. 1994, 177.
(101 a) C. 0 . Dietrich-Buchecker. J.-P. Sauvage. Chrm. R ~ Y 1987,
87. 795;
b) J.-C. Chambron, C. Dietrich-Buchecker. J.-P. Sauvage. Top. Curr. Chrm.
1993, 165, 131;c) J. F. Stoddart, A n . Quim. 1993.89, 51 ; d) R. Hoss, F. Vogtle,
Angen. Chem. 1994, 106.389; Angew. Chem. I n [ . Ed. Engl. 1994,33,375: e) S.
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4'1 VCH Verlugs~i~.~ellsi~liufi
mhH. 0-69451 Weinheim. 1995
0570-0833/9SjOSO5-OS73S. 10.00 + .25:0
f) H. L. Anderson, A. Bashall, K. Henrick. M. McPartlin, J. K. M. Sanders,
Angew. Chem. 1994, 106, 445; Angeu.. Chem. l n t . Ed. Engl. 1994, 33, 429.
[I I] FAB mass spectra were obtained with a Kratos MSRORF mass spectrometer
coupled to a DS90 system. The atom gun (Ion Tech Limited) was operated at
7 keV with a tube current of 2 mA. The primary beam of atoms was produced
from research-grade krypton. Samples were dissolved in a sinall amount of
3-nitrobenzyl alcohol that had been coated onto a stainless steel probe. Spectra
were recorded in the positive-ion mode at a scan speed of 30 s per decade.
[I21 M. Vetter, G. Schill. Telruhedrun 1967, 23. 3079.
[I31 Crystal data for 4-4PF6.4MeCN: monoclinic, u = 35.075(10). h =14.171(3),
c = 20.020(6) A, /3 = 119.43(2)': V = 8669 A3, space group C2/c. Z = 4.
p ~ 1 . 4 g4 ~ m - p(CuKx)
= 1 R cm-', 4063 independent observed reflections
with [IF,I > 4u(/Fo(),20 <116"] refined to R = 0.116, Rw = 0.129.
[I41 Siemens P4/Ra diffractometer, o scans, Cu,, radiation (graphite monochromator). The structure was solved by direct methods and the major occupancy
non-hydrogen atoms refined anisotropically. The minor occupancy atoms were
refined isotropically. Further details of the crystal structure may be obtained
from the Director of the Cambridge Crystallographic Data Centre, University
Chemical Laboratory, Lensfield Road, Cambridge CB2 1EW (UK), on quoting the full journal citation.
[IS] The OC,,H,O axis of the 1.5-dioxynaphthalene unit is inclined by 34" to the
equatorral plane of the tetracationic cyclophane as defined by the mean plane
of its four methylene carbon atoms.
[16] The distances between H-4 and H-8 on the naphthalene rings and the centers
of their immediately adjacent p-xylyl rings are 2.99 8,and the C-H ' . . centroid
angles are 143'. In the case of the C-H . . ' 0 interactions between one of the
p-xylyl hydrogen atoms and the central oxygen atoms of the polyether chains.
the H . . .O distances are 2.49 8, and the C-H . . ' 0 angles are 167'. For the
C-H ' . 0 interactions between the r-CH hydrogen atoms of the bipyridinium
unit and the same oxygen atoms of the polyether chains, the H . . ' 0 distances
are 2.47 8, and the C - H . . . O angles are 169".
[17] The length is defined as the distance between the centroids of the two p-xylyl
rings. and the width as the distance between the centers of the bond(s) linking
the pyridinium rings.
[I81 The 'H NMR spectra were recorded on a Bruker AMX400 spectrometer operating at 400.13 MHz. All chemical shifts are referenced via the residual
CHDJOCHCD, or CHD,CN signals to Me&
[Mn(C *H 6N2
02)3 ](C10 ,& : A Polymeric
34- and 68-Membered Metallacyclic Network
Forming a Novel Woven Polycatenated Structure**
ever, rare.141We report here the discovery of an unusual, new,
flexibly bridged, interpenetrating polycatenane.
We have recently been exploiting the conformational preferences of a series of extended-reach organic ligands of the general
type 1to create a range of two- and three-dimensional polymeric
metallamacrocyclic networks.r51Extending this work, we have
explored the effect of changing the position of the exocyclic
0-donor group on the heterocyclic unit from ortho to the para
position relative to the ring nitrogen, as in N,N'-p-phenylenedimethylenebis(pyridin-4-one) (2, p-XBP4). This has resulted in
the formation, inter alia, of the polymer 3.
X-Ray analysis[61of 3 shows that the crystal structure is based
on a network of octahedrally coordinated Mn centers linked by
p-XBP4 ligands (Fig. 1). There are two distinct ligand geometries (A and B) present in the structure in a 2: l ratio. In A,
one of the pyridone rings is essentially orthogonal to the central
p-xylyl unit, whilst the other is in an "open book" conformation
with respect to it. Bridges of this type link pairs of Mn centers,
creating open 34-membered rings (Fig. 1 ) . Within each 34-membered ring, adjacent pairs of &-coordinated pyridone rings are
held in a near coplanar arrangement by weak CH . . .O hydrogen bonds ( H . " 0 2.33 and 2.48 A) between the ortho CH
group of one pyridone ring and the oxygen atom of its cis-coordinated neighbor.
David M. L. Goodgame,* Stephan Menzer,
Amanda M. Smith, and David J. Williams*
The past decade has seen the creation of many elegant interlocked molecular species, the most notable of which have been
the catenanes, rotaxanes, and "knots" pioneered principally by
Sauvage et al. and Stoddart et al.['I Key factors in the development of this work have been the use of metal templating combined with appropriate ligand design, and the employment of
noncovalent interactions as part of the synthetic strategy. An
important feature of both these approaches has been the use of
conformationally flexible components.
Concurrent with this has been the development of three-dimensional networks based primarily on linking metal centers with
rodlike or other essentially rigid bridging components.[" An
occasional product of this latter work has been the formation of
interpenetrating, adamantyl-like
Interleaved, extended networks incorporating flexible bridging units are, how[*] Dr. D. M. L. Goodgame. Dr. D. J. Williams, Dr. S. Menzer, A . M . Smith
Chemistry Department
Imperical College of Science.
Technology and Medicine
London SW7 2AY (UK)
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[**I This work was supported by the Science and Engineering Research Council
and the Commission of the European Communities.
Verlugsgesellschufl mbH. 0-69451 Wernherm, 1995
Fig. 1. Part of the network of 34- and 68-membered metallacycles, showing the
ligand geometries A and B in 3.
Ligands in arrangement B have the pyridone rings centrosymmetrically disposed but skewed to a position intermediate between an orthogonal orientation and an open-book conformation with respect to the p-xylyl spacer. These type B
bridges serve to link pairs of the 34-membered rings, thus creating a set of 68-membered rings (Fig. 1). The manganese atoms
within this network lie in the ab plane and are separated by two
unit cell translations in both the a and b directions.
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Angew. Chem. I n l . Ed. Engl. 1995, 34. No. 5
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isomerism, catenanes, controlling, translation
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