Coordination-driven self-assembly of metallodendrimers possessing well-defined and controllable cavities as cores

Article abstract of DOI:10.1021/ja066804h

The design and self-assembly of novel cavity-cored metallodendrimers via noncovalent interactions are described. By employing [G0]-[G3] 120° ditopic donor linkers substituted with Frechet-type dendrons and appropriate rigid di-Pt(II) acceptor subunits, [G

Full text of DOI:10.1021/ja066804h

Published on Web 01/27/2007
Coordination-Driven Self-Assembly of Metallodendrimers
Possessing Well-Defined and Controllable Cavities as Cores
Hai-Bo Yang,*,† Adam M. Hawkridge,§ Songping D. Huang,‡ Neeladri Das,†
Scott D. Bunge,‡ David C. Muddiman,§ and Peter J. Stang*,†
Contribution from the Department of Chemistry, UniVersity of Utah, 315 South 1400 East, Room
2020, Salt Lake City, Utah 84112, W. M. Keck FT-ICR Mass Spectrometry Laboratory and
Department of Chemistry, North Carolina State UniVersity, Raleigh, North Carolina 27695, and
Department of Chemistry, Kent State UniVersity, Kent, Ohio 44242
Received September 21, 2006; E-mail: hbyang@chem.utah.edu; stang@chem.utah.edu
Abstract: The design and self-assembly of novel cavity-cored metallodendrimers via noncovalent
interactions are described. By employing [G0]-[G3] 120° ditopic donor linkers substituted with Fre´chet-
type dendrons and appropriate rigid di-Pt(II) acceptor subunits, [G0]-[G3]-rhomboidal metallodendrimers
and [G0]-[G3]-hexagonal, “snowflake-shaped” metallodendrimers with well-defined shape and size were
prepared under mild conditions in high yields. The assemblies were characterized with multinuclear NMR
(1H and 31P), mass spectrometry (ESI-MS and ESI-FT-ICR-MS), and elemental analysis. Isotopically resolved
mass spectrometry data support the existence of the metallodendrimers with rhomboidal and hexagonal
cavities, and NMR data are consistent with the formation of all ensembles. The structures of [G0]- and
[G1]-rhomboidal metallodendrimers were unambiguously confirmed via single-crystal X-ray crystallography.
The shape and size of two [G3]-hexagonal metallodendrimers were investigated with MM2 force-field
modeling.
Although modern supramolecular chemistry1 emerged from
the studies of such covalent macrocycles as crown ethers,
cyclophanes, calixaranes, cryptands, etc., it is currently domi-
nated by the biomimetic motive of noncovalent interactions such
as hydrogen bonding, metal-ligand coordination, π-π stacking,
electrostatic and van der Waals forces, hydrophobic and
hydrophilic interactions, etc. The power and versatility of this
bio-derived motive has been illustrated by numerous examples
of the use of noncovalent interactions in the synthesis of large
supramolecular assemblies in the past few decades. Supramo-
lecular dendrimers are a recent and important subset of such
self-assembled structures.
increasing attention3 not only because of the aesthetically
pleasing structures of these molecules but also as a result of
their various applications in host-guest chemistry,4 material
science,5 and membrane chemistry.6 Up to now, two comple-
mentary methodologies,3a,7 the divergent and the convergent,
have been employed in the preparation of dendrimers. However,
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Dendrimers2 are highly branched, three-dimensional macro-
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† University of Utah.
§ North Carolina State University.
‡ Kent State University.
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J. AM. CHEM. SOC. 2007, 129, 2120-2129
10.1021/ja066804h CCC: $37.00 © 2007 American Chemical Society

Self-Assembly of Cavity-Cored Metallodendrimers
A R T I C L E S
such covalent synthetic protocols often suffer from time-
consuming procedures and unsatisfactory yields resulting from
steric congestions. Compared to the conventional stepwise
formation of covalent bonds, the self-assembly process driven
by noncovalent interactions that is now universally recognized
to be crucial in the proliferation of all biological organisms offers
considerable synthetic advantages, including significantly fewer
steps, fast and facile formation of the final products, and inherent
defect-free assembly. As a consequence, attention has recently
turned to the self-assembly of dendrimers to provide well-
defined nanoscale architectures8 via a variety of noncovalent
interactions such as electrostatic interactions,9 hydrogen bond-
ing10 and metal-ligand coordination.11,12
Stimulated by the fact that natural pore-forming proteins play
a critical role in the biological process, acting as viral helical
coats13 and transmembrane channels,14 quite a few attempts have
been undertaken to build artificial supramolecular arrays with
porous structures by taking advantage of noncovalent interac-
tions.15 In particular, cavity-cored dendrimers have recently
received considerable attention because of their elaborate
structures and potential applications in delivery and recogni-
tion.16 For example, dendritic folate rosettes as ion channels in
lipid bilayers have been prepared, providing new insights into
the mechanism of ion transportation in biological process.10g
Previously, Percec et al. reported a library of amphiphilic
dendritic dipeptides that self-assemble into helical pores both
in solution and in bulk.16h However, considering nature’s simple
but delicate approach to desirable biomaterials, the design and
construction of cavity-cored dendrimers with predefined shape,
size, and ultimately function is still extraordinarily challenging.
In the past decade, the formation of discrete supramolecular
species by coordination-driven self-assembly has evolved to be
a well-established process.17 This approach offers a variety of
opportunities for the preparation of nanoscopic supramolecular
ensembles of predetermined shape, size, and symmetry, such
as molecular squares,18 rectangles,19 rhomboids,20 triangles,21
and hexagons.22 Encouraged by the power and versatility of this
methodology, we envisioned that the construction of metallo-
dendrimers with well-designed and controlled cavities would
be realized by the proper choice of subunits with predefined
angles and symmetry. In addition, the possibility to fine-tune
the size and shape of the cavities in metallodendrimers would
help provide an enhanced understanding of the geometrical
requirements necessary for molecular self-assembly. Further-
more, this strategy would likely give rise to the design and
synthesis of novel supramolecular species with desired func-
tionality arising from their unique interior cavities and dendritic
exteriors.
Recently we reported the self-assembly of the first metallo-
dendrimers exhibiting a nonplanar hexagonal cavity with an
internal core radius of approximately 1.6 nm, by the combination
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A R T I C L E S
Yang et al.
Figure 1. Graphical representation of the self-assembly of rhomboidal and
hexagonal, “snowflake-shaped” metallodendrimers.
Scheme 1 . Synthesis of [G0]-[G3] 120° Angular Dendritic Donor
Precursors
Figure 2. Structures of [G0]-[G3] 120° angular donor precursors 5a-d.
Scheme 2 . Self-Assembly of [G0]-[G3] 120° Angular Dendritic
Linkers 5a-d with 60° Di-platinum Acceptor 6 To Afford
Rhomboidal Metallodendrimers 7a-d
of 120° dendritic donor subunits (substituted with Fre´chet-type
dendrons) and 120° di-Pt(II) acceptor angular linkers in a 1:1
stoichiometric ratio.23 Here we report the results obtained when
we extended the investigations to the self-assembly of rhom-
boidal and “snowflake-shaped” metallodendrimers possessing
cavities of various size and shape at the core through the use of
coordination-driven self-assembly (Figure 1).
Results and Discussion
Synthesis of 120° Angular Dendritic Donor Subunits. The
synthesis of [G0]-[G3] 120° donor building blocks 5a-d
commenced with acylation of the commercially available
compound 3,5-dibromo-phenol (1) to give 2 (Scheme 1). The
3,5-bis-pyridylethynyl-phenyl ester 3 was prepared by pal-
ladium-mediated coupling reaction from ester 2 with 4-ethy-
nylpyridine in reasonable yield (66%). Upon ester hydrolysis
and etherification, the [G0]-[G3] 120° precursors 5a-d (Figure
2), substituted with Fre´chet-type dendrons, were obtained in
good yields.
dimensional polygon is determined by the value of the turning
angle within its angular components. Thus, the combination of
60° units with 120° linking components will yield a molecular
rhomboid. Stirring the [G0]-[G3] 120° angular donors 5a-d
with an equimolar amount of the known 60° angular acceptor,
2,9-(trans-Pt(PEt3)2NO3)2-phenanthrene (6), in CD2Cl2 for 14
h resulted in [2+2] rhomboidal metallodendrimers 7a-d,
respectively, in excellent yields (Scheme 2). Multinuclear NMR
(1H and 31P) analysis of [G0]-[G3] assemblies 7a-d exhibited
Synthesis of [G0]-[G3]-Rhomboidal Metallodendrimers
7a-d. With the 120° dendritic precursors in hand, the self-
assembly of metallodendrimers with rhomboidal cavities was
investigated. In general, the shape of an individual two-
(23) Yang, H.-B.; Das, N.; Huang, F.; Hawkridge, A. M.; Muddiman, D. C.;
Stang, P. J. J. Am. Chem. Soc. 2006, 128, 10014-10015.
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Self-Assembly of Cavity-Cored Metallodendrimers
A R T I C L E S
Figure 3. Calculated (top) and experimental (bottom) ESI-MS spectra of [G0]-[G2]-rhomboidal metallodendrimers 7a (A), 7b (B), and 7c (C).
very similar characteristics, which all suggested the formation
of discrete, highly symmetric metallodendrimers with rhom-
boidal cavities. The 31P{1H} NMR spectra of the [G0]-[G3]
assemblies 7a-d displayed a sharp singlet (ca. 14.6 ppm) shifted
upfield from the signal of the starting platinum acceptor 6 by
approximately 6.4 ppm. This change, as well as the decrease in
coupling of the flanking 195Pt satellites (ca. ∆J ) -177 Hz), is
consistent with back-donation from the platinum atoms. In the
1H NMR spectrum of each assembly, the R-hydrogen nuclei of
the pyridine rings exhibited 0.75-0.78 ppm downfield shifts,
and the â-hydrogen nuclei showed about 0.2 ppm downfield
shifts, due to the loss of electron density that occurs upon
coordination of the pyridine N atom with the Pt(II) metal center.
It is noteworthy that two doublets were observed for these
R-hydrogen nuclei, as this might be attributed to hindered
rotation about the Pt-N(pyridyl) bond, which has been previ-
Figure 4. Calculated (top) and experimental (bottom) ESI-FT-ICR-MS
spectra of [G3]-rhomboidal metallodendrimer 7d.
ously reported.24
The structures of the rhomboidal metallodendrimers 7a-d
1/1) solution of 7a and 7b respectively at ambient temperatures
for 3 days. Both 7a and 7b crystallize in the triclinic space group
P1h but are not isomorphous to each other, as revealed by their
different unit cell geometries and dimensions. Table 1 sum-
marizes the data collection, structure solution, and refinement
for 7a and 7b.
have also been confirmed by mass spectrometry (ESI-MS and
ESI-FT-ICR-MS). In the ESI mass spectra of the [G0]-[G2]
assemblies 7a-c, peaks attributable to the loss of nitrate
counterions, [M - 2NO3]2+ (m/z ) 1486.9 for 7a, m/z ) 1699.0
for 7b, and m/z ) 2123.8 for 7c) and [M - 3NO3]3+ (m/z )
970.5 for 7a, m/z ) 1112.0 for 7b, and m/z ) 1394.8 for 7c),
where M represents the intact assemblies, were observed. These
peaks were isotopically resolved, and they agree very well with
their respective theoretical distribution (Figure 3). The ESI-FT-
ICR mass spectrum of the [G3] assembly 7d showed two
charged states at m/z ) 1961.4 and 1455.5, corresponding to
the [M - 3NO3]3+ and [M - 4NO3]4+ species, respectively,
and their isotopic resolution is in excellent agreement with the
theoretical distribution (Figure 4). The analysis of the signals
observed in the full mass spectra confirmed that there was no
other assembled species formed (see Supporting Information).
X-ray crystallographic analysis unambiguously established
the structures of 7a and 7b to be both discrete [G0]- and [G1]-
rhomboidal metallodendritic assembles (Figures 5 and 6).
Crystals suitable for single-crystal X-ray analysis were grown
by vapor diffusion of n-pentane into a CH2Cl2/CH3COCH3 (v/v
The asymmetric unit of each structure contains a half
molecule situated around the center of inversion in the unit cell.
The entire supramolecular assembly is thus generated by
inversion. At the molecular level, both structures feature a well-
defined rhombus with an approximately 2.3 × 1.3 nm cavity
that embodies the porosity of the crystal. In both structures,
this cavity is partially filled with disordered nitrate anions and
solvent molecules. No attempt was made to completely model
such multiple disorders inside the cavity because these nitrate
anions and solvent molecules appear to occupy different
positions with fractional occupancies. The rhomboidal structure
of 7a has external dimensions of ca. 3.3 nm long and 2.8 nm
wide, while 7b spreads out over an area of ca. 4.2 × 2.8 nm2.
Except for a slight difference in their conformation, the two
molecules 7a and 7b can almost be superimposed with each
other in their rhomboidal parts (Figure 7).
(24) (a) Tarkanyi, G.; Jude, H.; Palinkas, G.; Stang, P. J. Org. Lett. 2005, 7,
4971-4973. (b) Yang, H.-B.; Das, N.; Huang, F.; Hawkridge, A. M.; Diaz,
D. D.; Arif, A. M.; Finn, M. G.; Muddiman, D. C.; Stang, P. J. J. Org.
Chem. 2006, 71, 6644-6647.
Synthesis of Hexagonal, “Snowflake-Shaped” Metallo-
dendrimers 10a-d with Smaller Cavities. According to the
9
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A R T I C L E S
Yang et al.
Table 1. Crystal Data and Structure Refinement for 7a and 7b
7a
7b
empirical formula
formula weight
temp (K)
crystal system
space group
C130H172N8O6P8Pt4
2968.99
173 ( 2
triclinic
C158H196N8O10P8Pt4
3393.16
173 ( 2
triclinic
P1h
P1h
unit cell dimensions
a ) 10.050(2) Å
b ) 18.319(4) Å
c ) 21.396(5) Å
R ) 76.932(4)°
â ) 80.904(4)°
γ ) 78.553(4)°
V ) 3734.0(15) Å3
Z ) 1
a ) 14.111(3) Å
b ) 14.348(3) Å
c ) 26.476(5) Å
R ) 79.705(3)°
â ) 78.901(3)°
γ ) 76.468(3)°
V ) 5063.8(18) Å3
Z ) 1
density (calcd, g/cm3)
1.268
3.862
1428
1.179
2.893
1810
abs coeff (mm-1
F(000)
)
crystal size
θ range for data collection 1.96-50.1
0.04 × 0.09 × 0.13 0.07 × 0.12 × 0.17
1.86-60.3
reflns collected/unique
refinement method
30035/13186
[R(int) ) 0.0424]
full-matrix least-
squares on F 2
9071/0/753
56271/28106
[R(int) ) 0.0740]
full-matrix least-
squares on F 2
14701/0/947
1.034
data/restraints/params
GOF on F 2
1.508
Figure 5. Crystal structure of [G0]-rhomboidal metallodendrimer 7a. The
NO3 anions and solvent molecules have been omitted for clarity.
final R indices
R1 ) 0.0722,
wR2 ) 0.2095
5.846, -0.915
R1 ) 0.0805,
wR2 ) 0.2211
4.546, -1.797
-
2
[Fo2 > 2σ(Fo )]
largest peak, hole (e/Å3)
Figure 7. Wireframe representation of the crystal structures of 7a and 7b
-
as they are superimposed with each other. The NO3 anions, solvent
molecules, and hydrogen atoms have been omitted for clarity.
which enclose a 120° angle) with six appropriate linear linker
units L2 (offering two coordination sites oriented 180° from each
other). When the [G0]-[G3] 120° angular donor subunits 5a-d
were reacted with the linear di-Pt(II) acceptor 1,4-bis((PMe3)2-
Pt(OTf))2-benzene (8) in CD2Cl2 at room temperature, the [6+6]
“snowflake-shaped” metallodendrimers 10a-d, respectively,
were formed (Scheme 3). 31P{1H} NMR analysis of the reaction
mixtures is consistent with the formation of a single, highly
symmetric species, as indicated by the appearance of a sharp
singlet (ca. -12.8 ppm) with concomitant 195Pt satellites, shifted
upfield by ca. 6.5 ppm as compared to 8 (Figure 9A). As
expected, a decrease in coupling of the flanking 195Pt satellites
was also observed (ca. ∆1JPPt ) -131 Hz), lending further
Figure 6. Crystal structure of [G1]-rhomboidal metallodendrimer 7b. The
NO3 anions and solvent molecules have been omitted for clarity.
-
“directional bonding” model25 and the “symmetry interaction”
model,26 discrete hexagonal entities of the type A2 L2 can be
6
6
rationally assembled via the combination of six shape-defining
and directing corner units A2 (offering two coordination sites
(25) (a) Stang, P. J.; Olenyuk, B. Acc. Chem. Res. 1997, 30, 502-518. (b)
Olenyuk, B.; Fechtenko¨tter, A.; Stang, P. J. J. Chem. Soc., Dalton. Trans.
1998, 1707.
(26) (a) Caulder, D. L.; Raymond, K. N. J. Chem. Soc., Dalton Trans. 1999, 1185.
(b) Caulder, D. L.; Raymond, K. N. Acc. Chem. Res. 1999, 32, 975-982.
9
2124 J. AM. CHEM. SOC. VOL. 129, NO. 7, 2007

Self-Assembly of Cavity-Cored Metallodendrimers
A R T I C L E S
Scheme 3 . Self-Assembly of [G0]-[G3] 120° Angular Dendritic
Linkers 5a-d with Linear Di-platinum Acceptors 8 and 9 To Afford
Hexagonal, “Snowflake-Shaped” Metallodendrimers 10a-d and
11a-d
Figure 8. Partial 1H NMR spectra of free [G3]-donor subunit 5d (A), [G3]-
hexagonal metallodendrimer 10d (B), and [G3]-hexagonal metallodendrimer
11d (C).
1
support to the formation of the complexes. In the H NMR
spectra of metallodendrimers 10a-d, the R-H and â-H of the
pyridine rings exhibited 0.21-0.27 ppm and ca. 0.28-0.32 ppm
downfield shifts, respectively, relative to uncoordinated 5a-d
1
(Figure 8B). The sharp NMR signals in both the 31P and H
NMR spectra along with the solubility of these species ruled
out the formation of oligomers.
Figure 9. 31P NMR spectra of [G3]-hexagonal metallodendrimer 10d (A)
and [G3]-hexagonal metallodendrimer 11d (B).
Mass spectrometric studies of the hexagonal metallodendrim-
ers 10a-d were performed using the ESI-FT-ICR technique,
which kept the assembly intact during the ionization process
while obtaining the high resolution required for unambiguous
determination of individual charge states. In fact, it is very
challenging to determine accurate masses for these charged
metallodendrimers because of the large molecular weight and
isotopic shift. In the ESI-FT-ICR mass spectra of [G0] and [G1]
assemblies 10a and 10b, the peaks at m/z )1597.1 (10a) and
m/z )1851.8 (10b), corresponding to [M - 5OTf]5+ respectively
were observed, and their isotopic resolutions are in excellent
agreement with the theoretical distributions (Figure 10A,B). The
charged state at m/z ) 1644.0 was observed in the ESI-FT-
ICR mass spectrum of [G2] assembly 10c, which corresponds
to [M - 7OTf]7+. It was isotopically resolved (Figure 10C),
and it agrees very well with the theoretical distribution.
According to the “symmetry interaction” model,26 the dis-
crepancy between the 120° angle needed for the hexagons and
the 108° angle needed for the analogous pentagons can easily
be accounted for once one considers the size of the macrocyclic
assembly. Since the building blocks are relatively large and
therefore quite flexible, small distortions of the ideal bond angles
of the subunits can occur and make up for the necessary 12°
difference per corner between a hexagon and a pentagon.
Therefore, it is necessary to discuss all the peaks exhibited in
the full ESI-FT-ICR mass spectra of the assemblies to exclude
the formation of a pentagon or a heptagon. By way of an
example, the full ESI-FT-ICR mass spectrum of [G1] assembly
10b displayed 10 multiple-charged molecular peaks (Figure 11).
The reasonable fragments attributable to these peaks are
9
J. AM. CHEM. SOC. VOL. 129, NO. 7, 2007 2125

A R T I C L E S
Yang et al.
Figure 10. Calculated (top) and experimental (bottom) ESI-FT-ICR-MS spectra of [G0]-[G2]-hexagonal metallodendrimers 10a (A), 10b (B), and 10c (C).
other factors (e.g., the highly charged nature of the assembled
structures and/or the interplay between entropic and enthalpic
contributions27) that are not yet fully understood.
Synthesis of Hexagonal, “Snowflake-Shaped” Metallo-
dendrimers 11a-d with Larger Cavities. Another type of
“snowflake-shaped” metallodendrimers 11a-d, with larger
hexagonal cavities compared to those of metallodendrimers
10a-d, were synthesized by using a longer linear di-Pt(II)
acceptor, 4,4′-bis((PEt3)2Pt(OTf))2-biphenyl (9). Multinuclear
NMR (1H and 31P) analysis of the [G0]-[G3] assemblies 11a-d
demonstrated the existence of discrete, highly symmetric species.
A sharp peak with platinum satellites at ca. 16.0 ppm was
observed in the 31P{1H} NMR spectra of the [G0]-[G3]
assemblies, shifted upfield from the peak of the starting platinum
acceptor 9 by approximately 6.2 ppm (Figure 9B). The JPt-P
decreased by about 150 Hz for all assemblies upon pyridyl
coordination. As expected, in the 1H NMR spectra, the R-H of
the pyridine rings shifted slightly from 8.6 ppm in the free
donors to 8.7 ppm in the assemblies, and â-H exhibited
Figure 11. Full ESI-FT-ICR mass spectrum of [G1]-hexagonal metallo-
dendrimer 10b. The letters correspond to the fragments listed in Table 2.
Table 2. Theoretical and Experimental ESI-FT-ICR Mass
Fragments from [G1]-Hexagonal Metallodendrimer 10b
m/z
fragmenta
calcd
found
approximately 0.4 ppm downfield shifts (Figure 8). In contrast
1
A
B
C
D
E
F
G
H
I
[2(8) + 2(5b) - 3OTf]3+
[8 + 2(5b) - 2OTf]2+
[2(8) + 3(5b) - 3OTf]3+
[2(8) + 5b - 2OTf]2+
[3(8) + 4(5b) - 4OTf]4+
[8 + 5b - OTf]+
961.897
983.300
962.592
983.833
to the results for rhomboidal metallodendrimers 7a-d, the H
NMR spectra of 10a-d and 11a-d showed only one doublet
for the R-H protons of the pyridine ring linked to the Pt(II)
center.
1161.297
1218.190
1250.310
1517.320
1666.878
1716.730
1816.420
1851.770
1161.711
1218.797
1251.159
1518.497
1668.138
1717.994
1817.765
1851.742
Compared to the hexagonal metallodendrimers 10a-d, it is
more difficult to get strong mass signals for the charged
ensembles 11a-d, even under the ESI-FT-ICR-MS conditions,
on account of their larger molecular weight. For instance, the
[G3]-hexagonal metallodendrimer 11d has a molecular weight
of 19 097.9 Da. With considerable effort, the peak attributable
to [M - 7OTf]7+ was observed in the ESI-FT-ICR-MS spectra
of the [G0]-[G2]-hexagonal assemblies 11a-c, which, along
with the isotopic resolution (i.e., direct charge state determi-
nation), allow for the molecularity of hexagonal metalloden-
drimers to be unambiguously established (Figure 12).
Unfortunately, all attempts to grow X-ray-quality single
crystals of the hexagonal metallodendrimers 10a-d and 11a-d
failed. MM2 force-field simulations were employed to optimize
the geometry of the [G3]-metallodendrimers 10d and 11d
[4(8) + 5(5b) - 4OTf]4+
[3(8) + 4(5b) - 3OTf]3+
[2(8) + 3(5b) - 2OTf]2+
[10b - 5OTf]5+
J
a The letters correspond to the peak labeling in Figure 11.
summarized in Table 2. No evidence for any other species, such
as a [5+5] pentagonal assembly, was found. Similar results were
observed in the full mass spectra of [G0]- and [G2]-metallo-
dendrimers 10a and 10c (see Supporting Information).
The combination of a linear ditopic unit with a 120° angular
unit in a 1:1 ratio may yield pentagons as well as hexagons,
since small distortions in the bond angles of the building blocks
are energetically not very costly.17a In the case of [G0]-[G2]-
metallodendrimers 10a-c, only hexagons are found. This may
be the result of a particular conformational rigidity of the system
(favoring the ideal geometry to a greater extent than usual) or
(27) (a) Yamamoto, T.; Arif, A. M.; Stang, P. J. J. Am. Chem. Soc. 2003, 125,
12309-12317. (b) Das, N.; Ghosh, A.; Arif, A. M.; Stang, P. J. Inorg.
Chem. 2005, 44, 7130-7137.
9
2126 J. AM. CHEM. SOC. VOL. 129, NO. 7, 2007

Self-Assembly of Cavity-Cored Metallodendrimers
A R T I C L E S
Figure 12. Calculated (top) and experimental (bottom) ESI-FT-ICR-MS spectra of [G0]-[G2]-hexagonal metallodendrimers 11a (A), 11b (B), and 11c (C).
as a core, with an internal radius of approximately 2.9 nm and
an outer radius of about 5.2 nm.
Conclusions
The work presented here provides a very simple yet effective
approach to the construction of well-defined charged metallo-
dendrimers possessing cavities with various size and shape
within their cores via coordination-driven self-assembly. By
combination of the predesigned 120° angular dendritic donors
and di-Pt(II) acceptors with appropriate angles (60° and 120°),
[G0]-[G3]-rhomboidal metallodendrimers and two types of
“snowflake-shaped” metallodendrimers were prepared under
mild conditions. Multinuclear NMR (1H and 31P) analysis of
all assemblies revealed very similar characteristics that are
suggestive of the formation of discrete, highly symmetric
species. The sharp NMR signals in both the 31P and 1H NMR,
along with the solubility of these species, ruled out the formation
of oligomers. The structures of all the metallodendrimers were
further established by mass spectrometry (ESI-MS and ESI-
FT-ICR-MS) and elemental analysis. The structures of [G0]-
and [G1]-rhomboidal dendrimers 7a and 7b were unambigu-
ously confirmed via X-ray crystallography.
Hence, we have demonstrated that highly convergent synthetic
protocols based on the simultaneous assembly of appropriate
predetermined building blocks allow the rapid construction of
novel cavity-cored metallodendrimers. In particular, this ap-
proach makes it possible to prepare a variety of metalloden-
drimers with well-defined and controlled cavities as cores
through the proper choice of subunits with predefined angles
and symmetry, which enriches the library of different-shaped
cavity-cored metallodendrimers. For instance, metallodendrimers
having nonplanar hexagonal cavities with different internal radii
of approximately 1.6,23 2.5, and 2.9 nm have been obtained by
this methodology. Furthermore, the shape of the cavities of the
supramolecular dendrimers can be rationally designed to be
either a rhomboid or a hexagon. Extending this idea further to
Figure 13. Space-filling models of hexagonal metallodendrimers 10d (A)
additional two-dimensional structures, such as squares, rect-
angles, and triangles, and even three-dimensional architectures
like trigonal prisms and trigonal bipyramids, is currently under
investigation.
and 11d (B) optimized with the MM2 force-field simulation. Trimethyl
and triethyl groups have been removed after the optimization for clarity.
(Figure 13). Simple space-filling models of the simulated
structures indicate that 10d and 11d have a very similar
nonplanar hexagonal cavity at their cores. In the case of 10d,
the cored-cavity metallodendrimer has an internal radius of
approximately 2.5 nm, while the outer radius is about 4.5 nm.
Likewise, the metallodendrimer 11d has an even larger cavity
Experimental Section
Triethylamine was distilled from sodium hydroxide, and tetrahy-
drofuran (THF) was distilled from K(s)/benzophenone. Dendritic
bromide [Gn]-Br,7a 2,9-(trans-Pt(PEt3)2NO3)2-phenanthrene (6),21e 1,4-
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A R T I C L E S
Yang et al.
bis((PMe3)2Pt(OTf))2-benzene (8),28 and 4,4′-bis((PEt3)2Pt(OTf))2-bi-
phenyl (9)28 were prepared according to literature procedures. Deuter-
ated solvents were purchased from Cambridge Isotope Laboratory
(Andover, MA). All other reagents were purchased (Aldrich or Acros)
and used without further purification. NMR spectra were recorded on
[G1]-Br, 60.5 mg, 0.203 mmol; for the reaction with [G2]-Br and [G3]-
Br, 30 mg, 0.115 mmol) and appropriate NaH were placed in a 25 mL
Schlenk flask followed by 2-3 mL of anhydrous DMF. The mixture
was stirred for 30 min. The appropriate [Gn]-Br was then added under
nitrogen. The reaction was continued at 65 °C for another 2 h and then
quenched by 10 mL of water, extracted with CH2Cl2 (3 × 20 mL), and
dried (MgSO4). The solvent was removed by evaporation on a rotary
evaporator. The residue was purified by column chromatography on
silica gel (acetone/hexane ∼1/1) to give compounds 5a-d.
a Varian Unity 300 or a Varian XL-300 spectrometer. The 1H and 13
C
NMR chemical shifts are reported relative to residual solvent signals,
and 31P NMR resonances are referenced to an external unlocked sample
of 85% H3PO4 (δ 0.0). Element analysis was performed by Atlantic
Microlab (Norcross, GA). Mass spectra for 7a-c were recorded on a
Micromass Quattro II triple-quadrupole mass spectrometer using
electrospray ionization with a MassLynx operating system. Mass spectra
for 7d, 10a-d, and 11a-d were recorded on a modified ESI-FT-ICR
mass spectrometer (Varian, Inc., Lake Forest, CA) equipped with an
actively shielded 9.4 T superconducting magnet (Cryomagnetics, Oak
Ridge, TN).
Successful X-ray crystallographic data collections for 7a and 7b were
carried out at -100 °C using a Bruker-AXS APEX2 diffractometer.
Crystals of 7c are mechanically too fragile to be handled at low
temperatures. The selected single crystals of 7a and 7b were each coated
with Fluorolube along with the mother liquor and frozen in a cold
nitrogen stream to form an amorphous protective matrix.
5a. Yield: 66.7 mg (white solid), 85%. Rf ) 0.40 (acetone/hexane
1
2/1). Mp: 170-171 °C. H NMR (CD2Cl2, 300 MHz): δ 8.60 (dd,
J ) 5.2 Hz and J ) 1.5 Hz, 4H, HR-Py), 7.39-7.45 (m, 10H, Hâ-Py,
ArH and PhH), 7.21 (d, 2H, ArH), 5.12 (s, 2H, PhCH2O). 13C NMR
(CD2Cl2, 75 MHz): δ 159.0, 150.2, 136.6, 131.0, 129.0, 128.6, 128.2,
127.9, 125.9, 124.1, 119.3, 92.5, 87.5, 70.7. MS (FAB): m/z 387.1 (M
+ 1)+. Anal. Calcd for C27H18N2O: C, 83.92; H, 4.69; N, 7.25.
Found: C, 83.66; H, 4.67; N, 6.99.
5b. Yield: 108.2 mg (white solid), 89%. Rf ) 0.38 (acetone/hexane
1
2/1). Mp: 183-184 °C. H NMR (CD2Cl2, 300 MHz): δ 8.60 (dd,
J ) 5.0 Hz and J ) 1.5 Hz, 4H, HR-Py), 7.33-7.44 (m, 15H, Hâ-Py,
ArH and PhH), 7.19 (d, 2H, ArH), 6.69 (d, J ) 2.1 Hz, 2H, ArH),
6.59 (t, J ) 2.1 Hz, 1H, ArH), 5.07 (s, 2H, ArCH2O), 5.06 (s, 4H,
PhCH2O). 13C NMR (CD2Cl2, 75 MHz): δ 160.6, 158.9, 150.2, 139.1,
137.2, 130.9, 128.9, 128.4, 128.3, 127.9, 126.0, 124.1, 119.3, 106.6,
101.8, 92.6, 87.6, 70.4. MS (FAB): m/z 599.1 (M + 1)+. Anal. Calcd
for C41H30N2O3: C, 82.25; H, 5.05; N, 4.68. Found: C, 82.13; H, 5.15;
N, 4.65.
Synthesis of Acetic Acid 3,5-Dibromo-phenyl Ester 2. A mixture
of 3,5-dibromophenol (0.85 g, 3.37 mmol) and acetic anhydride (1.03
g, 10.09 mmol) was heated at 70 °C for 2 h. The mixture was poured
onto ice, neutralized with K2CO3, and extracted with diethyl ether
(3 × 20 mL). The combined organic layers were washed with water
(2 × 25 mL) and brine (25 mL) and dried (Mg2SO4). The solvent was
removed by evaporation on a rotary evaporator. The residue was
purified by column chromatography on silica gel (acetone/hexane 1/10)
to give 2 as a pale pink solid. Yield: 0.90 g, 95%. Rf ) 0.4 (acetone/
5c. Yield: 102.4 mg (white solid), 87%. Rf ) 0.35 (acetone/hexane
1
2/1). Mp: 165-166 °C. H NMR (CD2Cl2, 300 MHz): δ 8.58 (dd,
J ) 5.7 Hz and J ) 1.5 Hz, 4H, HR-Py), 7.31-7.42 (m, 25H, Hâ-Py,
ArH and PhH), 7.19 (d, 2H, ArH), 6.68 (d, J ) 2.1 Hz, 6H, ArH),
6.56 (m, 3H, ArH), 5.06 (s, 2H, ArCH2O), 5.04 (s, 8H, PhCH2O), 5.00
(s, 4H, ArCH2O). 13C NMR (CD2Cl2, 75 MHz): δ 160.5, 158.9, 150.2,
139.7, 139.1, 137.3, 131.0, 128.9, 128.5, 128.3, 127.9, 126.0, 124.1,
119.3, 106.6, 101.8, 101.7, 92.6, 87.6, 70.4, 70.3. MS (FAB): m/z
1023.0 (M + 1)+. Anal. Calcd for C69H54N2O7: C, 81.00; H, 5.32; N,
2.74. Found: C, 81.07; H, 5.35; N, 2.69.
1
hexane 1/10). Mp: 56-57 °C. H NMR (CD2Cl2, 300 MHz): δ 7.57
(t, J ) 1.5 Hz, 1H, ArH), 7.27 (d, 2H, ArH), 2.28 (s, 3H, OCCH3). 13
C
NMR (CD2Cl2, 75 MHz): δ 168.8, 151.9, 131.9, 124.5, 21.1. MS
(CI): m/z 294.9 (M + 1)+.
Synthesis of 3,5-Bis-pyridylethynyl-phenyl Ester 3. A 100 mL
Schlenk flask was charged with 2 (0.96 g, 3.41 mmol), 4-bromopyridine
hydrochloride (1.14 g, 8.17 mmol), tetrakis(triphenylphosphine)-
palladium(II) (470 mg, 5 mol %), and CuI (31 mg, 2 mol %), degassed,
and back-filled three times with N2. Triethylamine (2.5 mL) and dried
THF (40 mL) were introduced into the reaction flask by syringe. The
reaction was stirred under an inert atmosphere at 60 °C for 16 h. The
solvent was removed by evaporation on a rotary evaporator. The residue
was purified by column chromatography on silica gel (acetone/hexane
1/1) to give 3 as a pale yellow solid. Yield: 0.76 g, 66%. Rf ) 0.2
(acetone/hexane 1/1). Mp: 152-153 °C. 1H NMR (CD2Cl2, 300
MHz): δ 8.61 (br, 4H, HR-Py), 7.63 (t, J ) 1.5 Hz, 1H, ArH), 7.40 (d,
5d. Yield: 151.6 mg (pale yellow glassy solid), 79%. Rf ) 0.30
1
(acetone/hexane 2/1). Mp: 78-79 °C. H NMR (CD2Cl2, 300 MHz):
δ 8.58 (d, J ) 5.4 Hz, 4H, HR-Py), 7.31-7.42 (m, 45H, Hâ-Py, ArH
and PhH), 7.19 (s, 2H, ArH), 6.68 (br, 14H, ArH), 6.55 (m, 7H, ArH),
4.99-5.02 (m, 30H, ArCH2O and PhCH2O). 13C NMR (CD2Cl2, 75
MHz): δ 160.3, 160.2, 158.7, 150.1, 139.6, 139.5, 139.0, 137.1, 130.8,
128.7, 128.6, 128.4, 128.2, 128.0, 127.8, 125.7, 123.9, 119.2, 106.5,
101.7, 101.6, 92.4, 87.5. MS (FAB): m/z 1871.6 (M + 1)+. Anal. Calcd
for C125H102N2O15: C, 80.19; H, 5.49; N, 1.50. Found: C, 80.12; H,
5.64; N,1.41.
J ) 5.1 Hz, 4H, Hâ-Py), 7.34 (d, 2H, ArH), 2.32 (s, 3H, OCCH3). 13
C
General Procedure for the Preparation of [G0]-[G3]-Rhom-
boidal Metallodendrimers 7a-d. To a 0.5 mL dichloromethane-d2
solution of nitrate 6 (5.2 mg, 0.00447 mmol) was added a 0.5 mL
dichloromethane-d2 solution of the appropriate [G0]-[G3] dendric
donor precursor 5a-d, drop by drop, with continuous stirring (10 min).
The reaction mixture was stirred overnight at room temperature. The
solution was evaporated to dryness, and the product was collected.
[G0]-Rhomboidal Metallodendrimer 7a. Yield: 6.86 mg (pale
yellow solid), 99%. 1H NMR (CD2Cl2, 300 MHz): δ 9.35 (d, J ) 5.4
Hz, 4H, HR-Py), 8.84 (s, 4H, H4), 8.72 (d, J ) 5.4 Hz, 4H, HR-Py),
7.95 (d, J ) 4.5 Hz, 4H, H2), 7.80 (d, J ) 5.4 Hz, 4H, H1), 7.65 (s,
4H, H10), 7.59 (d, J ) 6.6 Hz, 8H, Hâ-Py), 7.39-7.52 (m, 16H, PhH
and ArH), 5.20 (s, 4H, OCH2Ph), 1.36-1.37 (m, 48H, PCH2CH3),
1.10-1.20 (m, 72H, PCH2CH3). 31P{1H} NMR (CD2Cl2, 121.4 MHz):
δ 14.7 (s, 1JPt-P ) 2708.9 Hz). Anal. Calcd for C130H172N8O14P8Pt4·CH2-
Cl2: C, 49.42; H, 5.51; N, 3.52. Found: C, 49.65; H, 5.63; N, 3.47.
[G1]-Rhomboidal Metallodendrimer 7b. Yield: 7.56 mg (pale
yellow solid), 96%. 1H NMR (CD2Cl2, 300 MHz): δ 9.36 (d, J ) 5.7
Hz, 4H, HR-Py), 8.84 (s, 4H, H4), 8.70 (d, J ) 6.0 Hz, 4H, HR-Py),
NMR (CD2Cl2, 75 MHz): δ 169.1, 150.9, 150.1, 132.6, 130.6, 126.0,
125.7, 124.1, 91.5, 88.3, 21.1. MS (CI): m/z 339.2 (M + 1)+.
Synthesis of 3,5-Bis-pyridylethynyl-phenol 4. To a stirred solution
of 3 (0.75 g, 2.22 mmol) in methanol (20 mL) was added 1 M NaHCO3
(25 mL). The reaction was stirred until TLC indicated complete
consumption of 3. The solvent volume was reduced to half, and a large
amount of brown precipitate appeared. The brown solid was collected
by filtration, washed with water (3 × 20 mL), and dried under vacuum.
1
Yield: 0.59 g, 99%. Mp: >250 °C dec. H NMR (DMSO-d6, 300
MHz): δ 8.65 (br, 4H, HR-Py), 7.54 (br, 4H, Hâ-Py), 7.28 (s, 1H, ArH),
7.05 (s, 2H, ArH). 13C NMR (DMSO-d6, 75 MHz): δ 157.8, 150.0,
129.8, 125.7, 122.9, 119.5, 92.3, 87.0. MS (CI): m/z 297.2 (M + 1)+.
General Procedure for the Preparation of [G0]-[G3] Dendritic
Precursors 5a-d. Compound 4 (for the reaction with [G0]-Br and
(28) (a) Manna, J.; Kuehl, C. J.; Whiteford, J. A.; Stang, P. J.; Muddiman,
D. C.; Hofstadler, S. A.; Smith, R. D. J. Am. Chem. Soc. 1997, 119, 11611-
11619. (b) Manna, J.; Kuehl, C. J.; Whiteford, J. A.; Stang, P. J.
Organometallics 1997, 16, 1897-1905.
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2128 J. AM. CHEM. SOC. VOL. 129, NO. 7, 2007

Self-Assembly of Cavity-Cored Metallodendrimers
A R T I C L E S
7.95 (d, J ) 5.4 Hz, 4H, H2), 7.78 (d, J ) 5.4 Hz, 4H, H1), 7.65 (s,
4H, H10), 7.59 (d, J ) 5.7 Hz, 8H, Hâ-Py), 7.34-7.47 (m, 26H, PhH
and ArH), 6.74 (d, 4H, J ) 2.1 Hz, ArH), 6.62 (t, J ) 2.1 Hz, 2H,
ArH), 5.15 (s, 4H, OCH2Ar), 5.07 (s, 8H, OCH2Ph), 1.36-1.37 (m,
48H, PCH2CH3), 1.10-1.20 (m, 72H, PCH2CH3). 31P{1H} NMR (CD2-
(m, 258H, ArH and PhH), 6.98 (s, 24H, ArH), 6.60-6.63 (m, 84H,
ArH), 6.48 (br, 42H, ArH), 4.91-5.05 (m, 180H, OCH2Ar and OCH2-
Ph), 1.04 (m, 216H, PCH3). 31P{1H} NMR (acetone-d6/CD2Cl2 1/1,
121.4 MHz): δ -12.8 (s, JPt-P ) 2732.1 Hz). Anal. Calcd for
C870H852F36N12O126P24Pt12S12: C, 59.22; H, 4.87; N, 0.95. Found: C,
1
1
Cl2, 121.4 MHz): δ 14.6 (s, JPt-P ) 2707.7 Hz). Anal. Calcd for
58.96; H, 5.21; N, 0.86.
C
158H196N8O18P8Pt4: C, 53.86; H, 5.61; N, 3.18. Found: C, 53.56; H,
General Procedure for the Preparation of [G0]-[G3]-Hexagonal
Metallodendrimers 11a-d. To a 0.5 mL dichloromethane-d2 solution
of triflate 9 (6.02 mg, 0.00458 mmol) was added a 0.5 mL dichlo-
romethane-d2 solution of the appropriate [G0]-[G3] dendric donor
precursor 5a-d, drop by drop, with continuous stirring (10 min). The
reaction mixture was stirred overnight at room temperature. The solution
was evaporated to dryness, and the product was collected.
[G0]-Hexagonal Metallodendrimer 11a. Yield: 7.40 mg (pale
yellow solid), 95%. 1H NMR (CD2Cl2, 300 MHz): δ 8.69 (d, J ) 5.1
Hz, 24H, HR-Py), 7.82 (d, J ) 6.0 Hz, 24H, Hâ-Py), 7.61 (s, 6H, ArH),
7.34-7.50 (m, 90H, ArH and PhH), 5.17 (s, 12H, OCH2Ph), 1.35 (m,
144H, PCH2CH3), 1.09-1.19 (m, 216H, PCH2CH3). 31P{1H} NMR
(CD2Cl2, 121.4 MHz): δ 16.0 (s, 1JPt-P ) 2686.9 Hz). Anal. Calcd for
5.96; N, 2.92.
[G2]-Rhomboidal Metallodendrimer 7c. Yield: 9.58 mg (pale
yellow solid), 98%. 1H NMR (CD2Cl2, 300 MHz): δ 9.37 (d, J ) 6.0
Hz, 4H, HR-Py), 8.85 (s, 4H, H4), 8.68 (d, J ) 6.0 Hz, 4H, HR-Py),
7.94 (d, J ) 5.7 Hz, 4H, H2), 7.76 (d, J ) 5.7 Hz, 4H, H1), 7.65 (s,
4H, H10), 7.59 (d, J ) 4.8 Hz, 8H, Hâ-Py), 7.30-7.44 (m, 46H, PhH),
6.71-6.74 (m, 12H, ArH), 6.57-6.60 (m, 6H, ArH), 5.14 (s, 4H, OCH2-
Ar), 5.06 (s, 16H, OCH2Ph), 5.03 (s, 8H, OCH2Ar), 1.36 (m, 48H,
PCH2CH3), 1.09-1.19 (m, 72H, PCH2CH3). 31P{1H} NMR (CD2Cl2,
1
121.4 MHz): δ 14.6 (s, JPt-P ) 2707.7 Hz). Anal. Calcd for
C214H244N8O26P8Pt4: C, 58.78; H, 5.62; N, 2.56. Found: C, 58.61; H,
6.02; N, 2.22.
C
390H516 F36N12O42P24Pt12: C, 45.94; H, 5.10; N, 1.65. Found: C, 45.86;
[G3]-Rhomboidal Metallodendrimer 7d. Yield: 13.03 mg (pale
yellow glassy solid), 96%. 1H NMR (CD2Cl2, 300 MHz): δ 9.36 (d, J
) 5.4 Hz, 4H, HR-Py), 8.83 (s, 4H, H4), 8.65 (d, J ) 5.4 Hz, 8H,
HR-Py), 7.95 (d, J ) 5.7 Hz, 4H, H2), 7.74 (d, J ) 5.4 Hz, 4H, H1),
7.66 (s, 4H, H10), 7.58 (d, J ) 4.5 Hz, 8H, Hâ-Py), 7.30-7.42 (m,
86H, PhH), 6.62-6.75 (m, 28H, ArH), 6.55 (br, 14H, ArH), 5.09 (s,
4H, OCH2Ar), 4.94-5.02 (m, 56H, OCH2Ph and OCH2Ar), 1.36 (m,
48H, PCH2CH3), 1.09-1.19 (m, 72H, PCH2CH3). 31P{1H} NMR (CD2-
H, 5.34; N, 1.62.
[G1]-Hexagonal Metallodendrimer 11b. Yield: 8.51 mg (pale
yellow solid), 97%. 1H NMR (CD2Cl2, 300 MHz): δ 8.69 (d, J ) 5.4
Hz, 24H, HR-Py), 7.82 (d, J ) 5.7 Hz, 24H, Hâ-Py), 7.62 (s, 6H, ArH),
7.32-7.46 (m, 120H, ArH and PhH), 6.72 (s, 12H, ArH), 6.61 (s, 6H,
Ar), 5.12 (s, 12H, OCH2Ar), 5.08 (s, 24H, OCH2Ph), 1.35 (m, 144H,
PCH2CH3), 1.09-1.19 (m, 216H, PCH2CH3). 31P{1H} NMR (CD2Cl2,
1
1
121.4 MHz): δ 16.0 (s, JPt-P ) 2687.6 Hz). Anal. Calcd for
Cl2, 121.4 MHz): δ 14.6 (s, JPt-P ) 2707.7 Hz). Anal. Calcd for
C474H588F36N12O54P24Pt12S12: C, 49.63; H, 5.17; N, 1.47. Found: C,
C326H340N8O42P8Pt4·CH2Cl2: C, 63.81; H, 5.60; N, 1.82. Found: C,
49.64; H, 5.35; N, 1.42.
63.99; H, 5.82; N, 1.68.
[G2]-Hexagonal Metallodendrimer 11c. Yield: 10.28 mg (pale
yellow solid), 96%. H NMR (CD2Cl2, 300 MHz): δ 8.67 (br, 24H,
HR-Py), 7.81 (d, J ) 5.1 Hz, 24H, Hâ-Py), 7.62 (s, 6H, ArH), 7.32-
7.44 (m, 180H, ArH and PhH), 6.70-6.71 (m, 36H, ArH), 6.57-6.80
(m, 18H, Ar), 5.11 (s, 12H, OCH2Ar), 5.05 (s, 48H, OCH2Ph), 5.02
General Procedure for the Preparation of [G0]-[G3]-Hexagonal
Metallodendrimers 10a-d. To a 0.5 mL acetone-d6 solution of triflate
8 (5.50 mg, 0.00515 mmol) was added a 0.5 mL dichloromethane-d2
solution of the appropriate [G0]-[G3] dendric donor precursor 5a-d,
drop by drop, with continuous stirring (10 min). The reaction mixture
was stirred overnight at room temperature. The solution was evaporated
to dryness, and the product was collected.
1
(s, 24H, OCH2Ar), 1.35 (m, 144H, PCH2CH3), 1.09-1.20 (m, 216H,
1
PCH2CH3). 31P{1H} NMR (CD2Cl2, 121.4 MHz): δ 16.0 (s, JPt-P
)
2689.4 Hz). Anal. Calcd for C642H732 F36N12O78P24Pt12S12: C, 55.01;
H, 5.26; N, 1.20. Found: C, 55.21; H, 5.46; N, 1.21.
[G0]-Hexagonal Metallodendrimer 10a. Yield: 7.41 mg (pale
1
yellow solid), 99%. H NMR (acetone-d6/CD2Cl2 1/1, 300 MHz): δ
[G3]-Hexagonal Metallodendrimer 11d. Yield: 14.18 mg (pale
8.86 (d, J ) 5.7 Hz, 24H, HR-Py), 7.70 (d, J ) 6.3 Hz, 24H, Hâ-Py),
7.25-7.41 (m, 48H, ArH and PhH), 6.99 (s, 24H, ArH), 5.10 (s, 12H,
OCH2Ph), 1.05-1.07 (m, 216H, PCH3). 31P{1H} NMR (acetone-d6/
CD2Cl2 1/1, 121.4 MHz): δ -12.8 (s, 1JPt-P ) 2734.5 Hz). Anal. Calcd
for C282H348F36N12O42P24Pt12: C, 38.79; H, 4.02; N, 1.93. Found: C,
38.39; H, 4.40; N, 1.79.
1
yellow glassy solid), 97%. H NMR (CD2Cl2, 300 MHz): δ 8.66 (br,
24H, HR-Py), 7.79 (br, 24H, Hâ-Py), 7.63 (s, 6H, ArH), 7.30-7.41 (m,
300H, ArH and PhH), 6.62-6.73 (m, 84H, ArH), 6.55 (br, 42H, ArH),
4.99-5.07 (m, 180H, OCH2Ar and OCH2Ph), 1.33 (m, 144H, PCH2-
CH3), 1.07-1.20 (m, 216H, PCH2CH3). 31P{1H} NMR (CD2Cl2, 121.4
MHz): δ 16.0 (s, 1JPt-P ) 2696.1 Hz). Anal. Calcd for C978H1020F36N12-
[G1]-Hexagonal Metallodendrimer 10b. Yield: 8.32 mg (pale
O
126P24 Pt12S12·2CH2Cl2: C, 61.07; H, 5.36; N, 0.87. Found: C, 60.74;
H, 5.80; N, 0.81.
1
yellow solid), 97%. H NMR (acetone-d6/CD2Cl2 1/1, 300 MHz): δ
8.87 (d, J ) 6.3 Hz, 24H, HR-Py), 7.70 (d, J ) 6.3 Hz, 24H, Hâ-Py),
7.23-7.40 (m, 78H, ArH and PhH), 6.99 (s, 24H, ArH), 6.64 (d, J )
2.1 Hz, 12H, ArH), 6.54 (t, J ) 2.1 Hz, 6H, ArH), 5.05 (s, 12H, OCH2-
Ar), 5.00 (s, 24H, OCH2Ph), 1.05-1.07 (m, 216H, PCH3). 31P{1H}
NMR (acetone-d6/CD2Cl2 1/1, 121.4 MHz): δ -12.8 (s, 1JPt-P ) 2730.3
Hz). Anal. Calcd for C366H420F36N12O54P24Pt12S12: C, 43.94; H, 4.23;
N, 1.68. Found: C, 43.64; H, 4.37; N, 1.58.
Acknowledgment. P.J.S. thanks the NIH (GM-57052) and
the NSF (CHE-0306720) for financial support. We also thank
the NSF (CHE-9708413) and the University of Utah Institutional
Funds Committee for funding the Micromass Quattro II mass
spectrometer. D.C.M. and A.M.H. thank the W. M. Keck
Foundation and NCSU for generous financial support. We thank
Mr. Jeffrey A. Bertke for his help on determining the crystal
structures.
[G2]-Hexagonal Metallodendrimer 10c. Yield: 10.55 mg (pale
1
yellow solid), 98%. H NMR (acetone-d6/CD2Cl2 1/1, 300 MHz): δ
8.82 (br, 24H, HR-Py), 7.67 (br, 24H, Hâ-Py), 7.23-7.34 (m, 138H,
ArH and PhH), 6.99 (s, 24H, ArH), 6.63 (d, J ) 2.7 Hz, 36H, ArH),
6.50 (t, J ) 2.7 Hz, 12H, ArH), 5.05 (s, 12H, OCH2Ar), 4.96-4.98
(m, 72H, OCH2Ar and OCH2Ph), 1.05-1.07 (m, 216H, PCH3). 31P-
Supporting Information Available: 1H and 13C NMR spectra
1
of compounds 2-4 and 5a-d, H and 31P NMR spectra of
metallodendrimers 7a-d, 10a-d, and 11a-d, crystallographic
files (in CIF format) of [G0]- and [G1]-rhomboidal metallo-
dendrimers 7a and 7b, and full mass spectra of metalloden-
drimers 7a-d and 10a-c. This material is available free of
charge via the Internet at http://pubs.acs.org.
1
{1H} NMR (acetone-d6/CD2Cl2 1/1, 121.4 MHz): δ -12.8 (s, JPt-P
) 2730.3 Hz). Anal. Calcd for C534H564F36N12O78P24Pt12S12·2CH2Cl2:
C, 50.61; H, 4.50; N, 1.32. Found: C, 50.32; H, 4.62; N, 1.16.
[G3]-Hexagonal Metallodendrimer 10d. Yield: 14.83 mg (pale
yellow glassy solid), 98%. 1H NMR (acetone-d6/CD2Cl2 1/1, 300
MHz): δ 8.79 (br, 24H, HR-Py), 7.66 (br, 24H, Hâ-Py), 7.21-7.40
JA066804H
9
J. AM. CHEM. SOC. VOL. 129, NO. 7, 2007 2129