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Multicomponent Self-Assembly Spontaneous Formation of a Cylindrical Complex from Five Ligands and Six Metal Ions.

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C 0 M M U N I C AT1 O N S
capable of spontaneously generating well-defined inorganic
complexes from a larger set of components. comprising at
least two types of ligands and/or metal ions. The design and
choice of these components must fulfill criteria at all three
levels of molecular programming and information input that
determine the output of the desired final species- -recognition, orientation, and termination.
We report here on two such multiligand, multimetal, selfassembly processes involving two types of ligands and several Cu' ions: the generation of a cylindrical complex 1 and
the related component species 2 (Scheme 1). The formation
of a capped complex will be described elsewhere.[121
Multicomponent Self-Assembly:
Spontaneous Formation of a Cylindrical Complex
from Five Ligands and Six Metal Ions**
By Ptriil Basfer, Jean-Marie Lehn,* AndrG DeCian,
and Jean Fischer
Self-assembly consists of the spontaneous generation of a
well-defined. discrete supramolecular architecture from a
given set of components under specific conditions. Such processes require the design of "programmed" supramolecular
systems that rely on the information stored in the components and on the interaction algorithm that operates through
molecular recognition events.". 21 Depending o n the nature
of the molecules involved, the self-assembly can be organic
o r inorganic. In the assembly of supermolecules from metal
ions and ligands, the latter must contain the steric program
that is "read" by the metal ions following the algorithm
represented by their coordination geometry. The selfassembly of a given superstructure involves three stages :
recognition between the components, correct orientation so
as to allow growth, and termination of the process leading to
a discrete, finite supramolecular species." - 31
The formation of double-helical metal complexes, the helicates,[,
results from the self-organization of oligobipyridine (bpy) strands and Cu' o r Ag' ions that possess
tetrahedral coordination ge0metry.1~- 51 The interaction of
appropriately substituted oligo-bpy strands o r related ligands with metal ions prefering octahedral coordination may
yield triple-helical complexes.['* 81 Closed inorganic structures have been obtained, for instance, from the self-assemo r C U * + [ ~ions
~ ] and bis-p-diketone type
bly of Ni2+[9d1
ligands, of four Pt" metal complex fragments and four 4,4bpy groups,"'' and of four C u + ions and four bispyridylpyridazine ligands." ' I
The self-assembly of the helicates and related structures
involves just one type of ligand and metal ion. Further progress in the understanding and the control of the self-assembly and self-organization of inorganic (as well as of purely
organic) superstructures requires the conception of systems
[*] Prof. Dr. J.-M. Lehn, Dr. P Baxter
Laboratoire de Chimie Supramoleculaire
Institut Le Bel, Universite Louis Pasteur
4. rue Blaise Pascal, F-67000 Strasbourg (France)
Dr. A. DeCian, Prof. Dr. J. Fischer
Laboratoire de Cristallochimle et de Chimie Structurale
Institut Le Bel. Universite Louis Pasteur
4. rue Blaise Pascal, F-67000 Strasbourg (France)
I**]
This work was supported by the Centre National de la Recherche Scientifiquc (URA 422 and URA 424). P. B. thanks the Royal Society for a
one-year postdoctoral fellowship. We thank Prof. G. Wipff and E. Engler,
Stmsbourg. for the computer-generated representations.
2
Scheme 1. Schematic representation of the structures of 1 and 2. Phenyl and
methyl substituents are omitted for clarity. = Cu.
Hexaazatriphenylene (HAT) and its derivatives are ligands with three metal coordination sites, which yield, for
instance, a trinuclear complex by complexation of three
[Ru(bpy),]* units.['3, It appeared that a similar complex
might be formed with three [Cu(bpy)]+ units or related
groups.
Hexaphenylhexaazatriphenylene Ph,-HAT 3 was synthesized by condensation of benzil with hexaaminobenwas obtained by reduction of 1,3,5-tri~ e n e , ~16]
' ~which
'
amino-2,4,6-trinitrobenzenewith sodium in liquid ammonia.116,'71When 3 equiv dimethyl-bpy 4 and 1 equiv 3 in
CH,C1, were treated with [Cu(CH,CN),]BF, in CH,CN,
the reaction mixture showed first the reddish color
= 457 nm, c = 6550 M - 'cm- ') characteristic of bisbpy Cu' complexes (for Cu1(4),]+: i.,,, = 454 nm, e =
6700 M-'cm-'['*'). After 1.5 equiv [Cu(CH,CN),]BF, the
solution turned brown and after the addition of 2.5 equiv,
intensely purple (>,.
= 568 nm, E = 15 700 M - 'cm- ;
shoulder at 700 nm, c = 6570 M - 'cm-'), an unusual color
for a Cu' complex. These observations may be interpreted as
follows: initially the [Cu(4),]+ complex is formed exclusively
until at 1 .5 equiv the free ligand 4 is consumed. Upon further
addition of [Cu(CH,CN),]BF,, the weaker ligand Ph,-HAT
3 (whose pyrazine-type N atoms are poorer binding sites
than the bpy N atoms) participates; the [Cu(bpy),]+ species
opens up and [Cu(bpy)]+ units bind to the coordination sites
of ligand 3. Finally at 3 equiv [Cu(CH,CN),]BF,, a single
+
R
I
R
species is present, the trinuclear circular complex 2 (as the
2-(BF,)3 salt).
This proposed sequence is supported by mass spectrometry performed on the solutions containing different amounts
of the Cu' salt, which reveals the formation of [Cu(4),]BF4
and [CU,(~)(~),](BF,),.~'~]
The 'H N M R spectrum of the
2-(BF,), in CD,CI, also corresponds to the postulated structure.
Treatment of 3 itself with 3 equiv [Cu(CH,CN),]BF, in
CH,CN also afforded an orange-red solution which may
correspond to the formation of branched oligomeric and
polymeric Cu' complexes. This would amount to the spontaneous growth through self-assembly of coordination compounds resembling dendrimer-["' and arborol-typel"'
structures. Such a process may allow an entry into the selfassembly of oligomeric and polymeric coordination architectures from branching multinucleating ligands and suitable
metal
The results above were taken as sufficient evidence for the
generation ofcomplex 2. They also suggested that it might be
possible to achieve the self-assembly of a cylindrical, cagelike
structure 1 if 4 were replaced by ligand 5, in which two bpy
subunits are linked in the 5,s' positions. The quaterpyridine
(qpy) 5 was synthesized as follows: lithiation of 6 with BuLi
followed by treatment with SnMe,CI (1.2 equiv) gave 7
(63 YO;b.p. 200-205 "C). The regioselective monolithiation
of 2,s-dibromopyridine at position 5 with 1 equiv nBuLi and
subsequent treatment with CuCI, (0.5 equiv) was followed
by oxidative dimerization with 0, to provide 8 (30%; m.p.
248-249.5 'C). Finally reaction of 8 with 2 equiv 7 in the
presence of [Pd(PPh,),] gave 5 (68%; m.p. 249.5-250 "C).
During the slow addition of a solution of [Cu(MeCN),]BF, (6 equiv in CH,CN) to a stirred mixture of 3
(2 equiv) and 5 (3 equiv) in CH2CI, under argon, the color of
the reaction mixture changed from initially reddish brown
through dark brown to finally deep purple. The suspension
of 5 went into solution, and after about 20 h of stirring the
solvent was evaporated under vacuum leaving a dark-purple.
air-stable, solid. This was redissolved in CH,NO,, filtered,
and benzene was added dropwise to the filtrate. The solid
was removed by filtration and then dried under vacuum at
room temperature to give deep-purple. microcystalline
powder in quantitative yield (i,,, = 546 nm, E =
27600M-'cm-';
699nm,
E = 13500M-'cn-';
CH,Cl,).
The ' H N M R spectrum, the FAB (fast atom bombardment) mass spectrum, and the microanalytical data agree
with the formulation of this compound as [ C ~ ~ ( 3 ) ~ ( 5 ) , ] (BF,),. that is. 1-(BFJ6. This complex was found to be
markedly more stable than the trinuclear complex 2; repeated recrystallizations of the latter. for example, from CH,CI,/
hexane invariably resulted in some decomposition. whereas
the hexanuclear complex 1 was stable under the same conditions; 1 also underwent slow oxidation upon exposure to air
for several months. The 'H (500 MHz) and I3C (50.3 MHz)
N M R spectra of l-(BF& indicate that all three qpy ligands
as well as the two Ph,-HAT ligands areequivalent in solution
on the NMR timescale.
The construction of complex 1 was confirmed by its X-ray
crystal structure determination (Fig.
It is indeed an
/
6 Y=Br
7 Y=SnMe3
5
8 X=Br
Fig. 1 Model of the crystal structure of the self-assembled cylindrical tnorganic complex 1. Top- Side view Bottom: View along the vertical axis.
inorganic cagelike compound resulting from the self-assembly of two flat circular HAT ligands 3 that form the top and
bottom. three bridging quaterpyridine groups 5, and six Cu'
ions that hold the five organic components together.
Complex 1 possesses a C , axis passing through the middle
of the central C-C bond of one of the qpy units; this distorsion from the threefold symmetry may be due to crystal
packing. The top and bottom HAT units are close to planar
(maximum deviation from mean plane 0.19 A) and almost
parallel to each other (13.3" angle between the normals t o
their mean planes): they are not eclipsed as shown in
Scheme 1. but rotated with respect to each other by about
27" (Fig. I bottom). Every bpy group in the three qpy units
is approximately planar (maximum deviation of 0.32 A), and
the two bpy groups of the two equivalent qpy groups are
twisted with respect to each other by an angle of 36"; those
of the qpy located on the binary axis are twisted by 25". The
vertical qpy bridges are inclined by an angle of 66" with
respect to the axis passing through the center of the two HAT
units. The Cu' sites are distorted from tetrahedral coordination. with a dihedral angle of 72" between the N-Cu-N planes
corresponding to the bpy and HAT units. The three Cu'
ions lie in the HAT plane and form approximately an equilateral triangle with a mean edge length of 6.85 8,. The planes
of the phenyl rings form a 60" angle with the plane of the
respective HAT unit. The overall twist of the structure results
in a triple-helical shape of the complex. Bond lengths and
angles d o not show any peculiarity.
Complex 1 has a cylindrical internal cavity with a height
of 7 . 4 A (mean distance between the HAT planes) and a
radius of about 5.5 8, (based on the nitrogen atoms of the
three qpy groups). Taking the van der Waals radii into account the cylindrical void has a height of approximately 4 8,
and a radius of 4 8,; one may envisage binding substrate
molecules in this cavity, in particular flat, aromatic units of
suitable dimensions. Thus 1 would be a self-assembled
molecular receptor for appropriate substrate species.[*]
An investigation into the precise structural requirements
of the ligands 3 and 5 which control the self-assembly of the
cage complex 1 is in progress. We are also working on the
extension of the process described here to related ligands.
The formation of structure 1 demonstrates the remarkable
self-organization of a closed inorganic architecture by the
Fig. 2. CPK representation of 1. The side view corresponds to Figure 1 top.
[*] I f a suitable substrate were to he spontaneously and selectively included into
1 in the course of the self-assembly, this would represent an assembly of
twelve (!) partners into an elective community (EC), a very timely process.
A i i g i w Chcni. Inr.
Ed. Eii,ql. 1993, 32, N o . I
((3
spontaneous and correct assembly of altogether eleven particles consisting of two types of ligands and one type of metal
ion. The operation of this instructed supramolecular system
fulfills the three levels of molecular programming and of
information input: recognition, orientation, and termination.
Received. October 14. 1992 [Z 5624 IE]
German version' Angim. C'heni. 1993. 105. 92
[I] J.-M. Lehn, Angerc. Chem. 1990, 102, 1347; Angeii.. Chrm. 1nr. Ed. Engl.
1990, 29, 1304.
121 J.-M. Lehn in Per.speclive.\ in Coortlinulton ChemisrrJ- (Eds.: A. F. Williams, C. Floriani. A. E. Merhach), Verlag Helvetica Chimica Acta. Basel
and VCH, Weinheim, 1992, p. 447.
[3] A. Pfeil, J.-M. Lehn. J. Chem. Soc. Chrm. Commun. 1992. 838.
[4] J.-M. Lehn. A. Rigault, J. Siegel, J. Harrowfield, B. Chevrier. D. Moras.
Proc. Nurl. Acud. Sci. USA 1987. 27. 2565; J.-M. Lehn, A. Ripault. An&wi..
Chem. 1988, 100. 1121, Angeir. Cliem. I n f . Ed Engl 1988, 2 7 ~1095
[S] T. M. Garrett, U. Koert, J.-M. Lehn, A. Rigault. D. Meyer. J. Fischer. J.
Chem. Sot.. Chrm. Commun. 1990, 557.
[6] See also: E. C. Constable. R. Chotalia. J. Chem Soc. Chrni. Commun.
1992, 64. and references cited therein.
171 R. Krimer, J.-M. Lehn. unpublished results.
[81 A. F. Williams. C. Piguet, G. Bernardinelli. Angew. Chrm. 1991. 103. 1530;
Angels. Chem. Ini. Ed. Engl. 1991, 30, 1490.
[9] a) R. Kohler, R. Kirmse. R. Richter, J. Sieler. E. Hoyer, Z . Anorg. Allg.
Chem. 1986, 537, 133; b) J. R. Bradhury, J. L. Hampton. D. P. Martone.
A. W. Maverick, fnorg. C k m . 1989, 28. 2392.
[lo] M. Fujita. J. ydzaki, K.Ogura. J. A m . Chem. Soc. 1990. 112. 5645.
[l I] M.-T. Youinou, N. Rahmouni, J. Fischer. J. A. Osborn. Angeii.. Chrm.
1992. 104. 771; A n g c v . Chcm. Inl. Ed. Engl. 1992. 31, 733.
[12] R. Krdmer. J.-M. Lehn. unpublished results.
[13] R. Nasielski-Hinkens, M. Benedek-Vamos. D Maetens. J. Nasielski. J.
Urgunomet. Chem. 1981. 217, 179.
[I41 A. Masschelein, A. Kirsch.De Mesmaeker, C . Verhoeven. R. NasielskiHinkens, fnorg. Chnn. Acra 1987, 129, L13.
[I51 B. Kohne, K. Praefcke, Lfehgs Ann. Chcm. 1985. 522.
[16] J. Nasielski, C. Moucheron, D. Verhoeven. R. Nasielski-Hinkens. fiwohr&on Left. 1990, 31, 2573.
[I71 D. Z. Rodgers. J. Urg. Chem. 1986. 51, 3904.
[18] J. R. Hall, M. R. Litzow. R. A. Plowman, Anal. Chem. 1963. 35, 2124; E.
Miiller, C . Piguet. G. Bernardinelli. A. F. Williams. Inorg. Chern. 1988.27.
849.
1191 FAB and electrospray mass spectrometry have been used to identify the
complexes formed in solution from various ligands and metal ions; such
data give direct information on complexation equilibria: P. Baxter. A. Van
Dorsselaer, R. Krimer, JLM. Lehn, A. Marquis-Rigault. unpublished results.
[20] D. A. Tomalia. A . M . Naylor, W. A. Goddard 111, A n p w . (%en?. 1990.
102,119; Angew. Chem. fnt. Ed. Engl. 1990.29.138; C . J. Hawker. J. M . J.
F r k h e t , J. Am. Chem. Soc. 1990. 112, 7638.
[21] G. R. Newkoine, Z:q. Yao. G. R. Baker. V. K.Gupta, P. S. Russo, M. J.
Saunders. J. Am. Chem. Soc. 1986,108,849; G . R. Newkome. G . R. Baker, M. J. Saunders, P. s. Russo, V. K. Gupta, Z.-q. Yao. J. E. Miller. K.
Bouillion, J. Chem. Soc., Chem. Comn~un.1986, 752.
[22] For the stepwise synthesis of branched multinuclear complexes see- G.
Denti, S. Campagna, S. Serroni, M. Cianio. V. Balzani, J. A m . Chem. Sw.
1992, 114, 2944, and references therein. See also: S. Serroni. G . Denti, S.
Campagna, A. Juris, M. Ciano, V. Balzani, Angpii.. Chem. 1992. 104. 1540;
AnKen. Chem. Int. Ed. Engi. 1992.31. Nr. 11.
[23) a ) Crystal data: Suitable single crystal of I-(BF,),F, ' 4C,H,CI, ' 5 H z 0
were obtained by slow diffusion of pentane into a solution of I-(BF& in
1.1,2,2-tetrachloroethane(initially cooled in air to liquid N, temperature)
at room temperature. A single crystal was cut otlt from a cluster of crystals
and mounted o n a rotation-free goniometer head (Philips PW1100.'16 automatic diffractometer). M = 4104.9, monoclinic, space group C2;c. (t =
33.978(10),b= 30.141(9),c=20.840(6)~. V=19846.8AZ.g,,,,, =1.374,
Z = 4, p(CuKz)= 33.755 c m - ' (graphite monochromator). A total of
9377 reflections were collected at - 100 C ; the temperature was held constant with a gas flow device of our own construction. For all calculations
the Enraf-Nonius Mole/VAX package 123b] was used. with the exception
of data reduction program which was our own. The raw step-scan data
were converted to intensities by the Lehmann-Larsen method [23c]. The
intensities of three reflections measured every hour during the entire daia
collection period showed a decay of 46%; therefore a second data collection was started using two crystals. With the first one, data with
3' < 0 < 35' were collected. with the second remaining data. For each
crystal, a linear decay of 16% was corrected. After application of separate
Lorentz, polarization, and absorption corrections. the latter based on psi
scans, the scale between the two sets was determined from 120 common
reflections using a least-squares procedure. The structure was solved using
MULTAN [23dl. After refinement of the heavy atoms, the hydrogcn
V C H ~ ~ ~ l u ~ . g e s e l l . ~mhH,
r / i u / W-6940
r
Weinhemi, 1993
S 10.00+ .25/0
OS70-0~33~93j~lO1-~071
71
atoms of the core were introduced in structure factor calculations by theiiand isotropic temperature factors
computed coordinates (C-H = 0 95
such as B(H) = 1.3 Beqv(Cj A', but not refined. The overall temperature
factor of the structure is high (5.4 A') indicating some disorder and low
diffraction power, therefore the accuracy obtained is lower than normally
expected. Full least-squares refinements; u2(F2)= uzeeum,.@02.
R ( F ) = 0.103, Riv(F) = 0.147. The scattering tdctor coefficients and anomalous dispersion coefficients come from ref. [23e]. b) B. A. Frenz, Tilr
Enruf-Noniirs CAD4-SDP in Compuling in Crj truilogruph~.(Eds.: H.
Schenk. R. Olthof-Hazekamp. H. Van Koningveld. G. C Bassi). Delft
University Press, 1978, pp. 64-71: c) M. S. Lehmann, F. K. Larsen, Actu
Crjtrullogr. Secr. A 1974. 30, 580; d ) G. Germain, P. Main, M. M. Woolfson. ihid. B 1970, 26, 274; ihid. A 1971. 27. 368; e) D. T. Cromer, J. T.
Waber. Inrurnurionul Tuhles for X-Ruj, C r j s ~ u l l o g r u p l ~Vol.
j . IV. The Kynoch Press. Birmingham. 1974. Tables 2.2 b and 2.3.1 ; f ) further details of
the crystal structure investigation are available on request from the Director of the Cambridge Crystallographic Data Centre. Universily Chemical
Laboratory, Lensfield Road. GB-Cambridge. CB2 IEW (UKj. on quoting
the full journal citation.
A)
+
Cavities for Binding Two Metal Atoms:
A Novel Pentanuclear Copper(1) Complex with
an Anionic, Pentadentate Aryl Ligand with Two
ovtho-Chelating Diamine Substituents**
By G. Marc Kapteijn, Ingrid C. M . Wehman-Ooyevaar,
David M . Grove, Wiberih J: J. Smeets, Anthony L. Spek,
and Gerard van Koten*
A
B
Scheme 1. Bonding modes of ncn. I n structures of type A iicn may function as
a two-, four-, or six-electron donor ligand
clearly show that completion of the Li and Cu coordination
spheres requires formation of larger aggregates. In the case
of 1 this is achieved by dimerization; in the case of 2 by
linkage of two Cu(ncn) units with two CuBr units. We have
now expanded the simple cavity of ncn by replacing one
methyl group of each NMe, unit by CH,CH,NMe, to form
a potentially pentacoordinate, anionic N,N,C,N,N ligand 4.
We report here on our investigation of the bonding properties of 4 to copper(!) centers, specifically on an arylcopper
copper bromide compound in which aryldicopper cations
are stabilized by intramolecular coordination and a CuBr,
dianion.
The design and use of multidentate ligands is of great
interest in organometallic chemistry."] We are studying the
construction of cavities formed by organic ligdnds, in which
a metal ion is bound by a metal-carbon CJ bond and the
metal center is coordinatively saturated as a result of additional intramolecular coordination of heteroatoms present
in the surface enclosing the cavity. A simple representative of
this class of ligands is the anionic aryldiamine ncn which
coordinates through the two N and one C atoms and exhibits
[2,6-(CH,NMe,),C,H3]-
ncn
versatile bonding modes ranging from monodentate ( 0 - C )
and bidentate (C,N) to tridentate (mer- or .fac-N,C,N),12'
depending on the metal (structure A in Scheme 1). Interestingly, several examples are known in which ncn formally
binds two metal atoms by either a two-electron three-center
(2e-3c) bond, whereby Cip,, bridges two metal atoms, as in
1 [31 and 2,[41or by a (2e + 2e)-3c bond, whereby Clgs0bridges
two unlike metal atoms as i n 3 (structure B in Scheme 1).Is1
The structures of 1 and 2 in the solid state and in solution
1
[Li,(ncn)J
[Cu,Br,(ncn),]
4
The precursor to 4, compound 5, was synthesized from the
reaction of 1 equivalent of 2,6-(CH,Br),C,H,Br with 2
equivalents of HN(Me)CH,CH,NMe, in the presence of
NEt, as a base.[61Treatment of 5 with two equivalents of
2,6-[CH,N(Me)CH,CH,NMe,],C,H,Br
5
n-butyllithium afforded the lithium salt of 4 which was isolated as the unique adduct 6 of aryllithium and lithiumbromide.16]When 6 was treated with two equivalents of CuBr in
benzene a novel type of pentanuclear Cu' complex 7 was
2
[TaCl,(~-ncn)(~-C-rBu)(ZnC1)13
[*I
[**I
72
Prof. Dr. G. van Koten, G M. Kapteijn, I. C. M. Wehrnan-Ooyevaar.
Dr. D. M. Grove
Debye Research Institute
Department of Metal-Mediated Synthesis
University of Utrecht
Padualaan 8, NL-3584 CH Utrecht (The Netherlands)
W. J. J. Smeets. Dr. A. L. Spek
Bijvoet Centre for Biornolecular Research
Laboratory for Crystal and Structural Chemistry
University of Utrecht
This research was supported by Shell Research B.V. (G. M. K..
I. C. M. W-0.) and also in part (W. J. J. S.. A. L. S.) by the Netherlands
Foundation for Chemical Research (S. 0. N.) with financial aid from the
Netherlands Organization for Scientific Research (N. W. 0.).
2:.
VCH ~,rlufisXest,l~ri.hnfI
mhH. W-6Y40 Wc.mhrim. 1993
isolated in 73 YOyield.['' In the X-ray crystal structure of 7
the monoclinic unit cell contains two molecules of 7 and two
molecules of diethyl ether. 7 is a pentanuclear Cu' complex
most readily described as two cationic organocopper moieties [Cu,(4)]' linked by a CuBrZ- dianion (Fig. l).[*] The
two aryl ligands 4 bridge a pair of Cu atoms (Cu2, Cu3 or
Cu4, Cu5) at the anionic Clpsocenter, the Cu-C,,,,-Cu angles
are very acute (Cu2-Cl-Cu3 73.8(2); Cu4-CI9-Cu5
73.6(2)"). In combination with the short Cu ... Cu distances
(Cu... Cu 2.456(1) A) and the four similar Cu-C distances
(Cu-C 2.049(6) A) these geometric parameters are indicative
0570-OR33i93i01Of-0072 5 10.00-t ,2510
Angel,. Chem. Inr. Ed. Engl. 1993. 32, N u . I
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