Synthesis of triangular metallodendrimers via coordination-driven self-assembly

Article abstract of DOI:10.1021/jo300016a

A new family of 60° dendritic di-Pt(II) acceptor tectons have been successfully designed and synthesized, from which a series of novel "three-component" triangular metallodendrimers were prepared via [3 + 3] coordination-driven self-assembly. The structur

Full text of DOI:10.1021/jo300016a

Article
pubs.acs.org/joc
Synthesis of Triangular Metallodendrimers via Coordination-Driven
Self-Assembly
Qing Han,† Li-Lei Wang,† Quan-Jie Li,‡ Guang-Zhen Zhao,† Jiuming He,§ Bingjie Hu,∥ Hongwei Tan,‡
Zeper Abliz,§ Yihua Yu,∥ and Hai-Bo Yang*,†
†Shanghai Key Laboratory of Green Chemistry and Chemical Processes, Department of Chemistry, East China Normal University,
3663 North Zhongshan Road, Shanghai 200062, P. R. China
‡Department of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
§Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, P. R. China
∥Shanghai Key Laboratory of Magnetic Resonance, Department of Physics, East China Normal University, Shanghai 200062, P. R.
China
S
* Supporting Information
ABSTRACT: A new family of 60° dendritic di-Pt(II) acceptor tectons have been
successfully designed and synthesized, from which a series of novel “three-
component” triangular metallodendrimers were prepared via [3 + 3]
coordination-driven self-assembly. The structures of newly designed triangular
1
metallodendrimers are characterized by multinuclear NMR (1H and 31P), H
DOSY NMR, mass spectrometry (CSI-TOF-MS), and elemental analysis. The
shape and size of all supramolecular dendritic triangles were investigated with
PM6 semiempirical molecular orbital methods.
Coordination-driven self-assembly9 has proven to be a
particularly powerful method for the construction of supra-
INTRODUCTION
■
Dendrimers1 are highly branched, three-dimensional macro-
molecular two-dimensional (2-D) and three-dimensional (3-D)
structures with well-defined shape and size.10,11 Among the
known artificial metallacycles, triangle12 has attracted consid-
erable attention since the first example12a of a cyclic organogold
molecular triangle reported by Vaughan in 1970. However, the
formation of supramolecular triangles sometimes suffers from
the noticeable equilibrium with other macrocyclic species when
flexible building blocks are employed.13 For example, Fujita and
co-workers have reported that the self-assembly of [Pd(en)-
(ONO2)2] with longer and more flexible 180° dipyridine
ligands affords equilibrium mixtures of molecular squares and
triangles.13a According to the directional-bonding method-
ology,9a,c a predesigned supramolecular triangle can be
assembled by the reaction of three rigid ditopic 60° tectons,
serving as the corners, with three linear sides.14 For instance, we
have realized the formation of supramolecular multiferrocenyl
triangles from the combination of 60° ferrocenyl building
blocks with different sized linear donor subunits via
coordination-driven self-assembly.11a With the aim of develop-
ing self-assembly of novel supramolecular functionalized
molecules comprised of several dendritic wedges extending
outward from an internal core. In the past few decades, the
design and synthesis of diverse dendrimers2 has evolved to be
one of the most attractive subjects within supramolecular
chemistry because of their wide applications in host−guest
chemistry,3 catalysis,4 materials science,5 and nanomedicine,6
etc. In general, two complementary methodologies,2a the
divergent and the convergent, have been employed in the
preparation of dendrimers. However, such covalent synthetic
protocols sometimes 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 exhibits considerable synthetic advantages includ-
ing comparatively fewer steps, fast and facile formation of the
final products, and inherent detect-free assembly. In particular,
self-assembly provides an efficient approach to the construction
of the higher order supramolecular dendrimers. As a
consequence, there has been an increasing interest in the
studies of self-assembly of dendrimers to provide well-defined
nanoscale architectures7 via a variety of noncovalent
interactions8 such as electrostatic interactions, hydrogen
bonding, and metal−ligand coordination.
Received: January 31, 2012
Published: March 20, 2012
© 2012 American Chemical Society
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triangles, the design and synthesis of new 60° tectons is still
necessary.
Herein we have successfully synthesized a new family of 60°
dendritic metal-containing corners (Figure 1) from which a
Scheme 1. Synthesis of 60° Dendritic Di-Pt(II) Acceptor
Subunits 1a−c
Figure 1. Molecular structures of [G-1]−[G-3] 60° dendritic di-Pt(II)
acceptor subunits 1a−c.
series of novel supramolecular metallodendritic triangles were
obtained via coordination-driven self-assembly. These triangu-
lar metallodendrimers are formed via the directional-bonding
approach that is not template directed. It should be noted that
supramolecular metallodendrimers are of special interest
because of a variety of materials and synthetic applications.15,16
For example, we have previously reported the self-assembly of a
variety of metallodendrimers with cavities of various shapes and
sizes such as rhomboids and hexagons.16a−f Moreover, a family
of new metallodendritic squares has been synthesized from 4,4′-
For the assembly of supramolecular metallodendritic
triangles, 4,4-bipyridyl (5) was employed as 180° linear
building blocks. The self-assembly of triangular metalloden-
drimers 6a−c proceeded essentially quantitatively as outlined in
Scheme 2. Heating the mixtures of 4,4-bipyridyl (5) and the
́
bipyridines funtionalized with Frechet dendrons and (dppp)-
Pt(II) or Pd(II) triflate by Schalley’s group.16g Very recently,
Newkome and co-workers have reported the synthesis and
photophysical properties of a series of new dendron-
functionalized bis(terpyridine)−iron(II) or −cadmium(II)
metallomacrocycles.16h Herein we report our results on the
self-assembly of triangular metallodendrimers from the newly
designed 60° dendritic corners without using a template.
Scheme 2. Self-Assembly of Supramolecular Triangular
Metallodendrimers 6a−c via [3 + 3] Coordination-Driven
Self-Assembly
RESULTS AND DISCUSSION
■
The new 60° dendritic di-Pt(II) acceptors 1a−c can be easily
synthesized in three steps as shown in Scheme 1. The Frechet-
́
type dendrons were introduced by an etherification reaction of
3,6-dibromophenanthrene-9,10-diol17 (2) with the correspond-
ing dendritic bromides.16f Compounds 3a−c were then reacted
with 4 equiv of Pt (PEt3)4 to give bromide complexes 4a−c.
Subsequent halogen abstraction with AgNO3 resulted in the
isolation of bisnitrate salts 1a−c in reasonable yield. It was
found that 60° dendritic diplatinum linkers 1a−c displayed
singlets (19.27 ppm for 1a; 19.29 ppm for 1b; 19.00 ppm for
1c), accompanied by concomitant 195Pt satellites in the 31P{1H}
NMR spectra. Single crystals of di-Pt(II) dibromide complex
4a, suitable for X-ray diffraction studies, were grown by slow
vapor evaporation of a solution of a solvent mixture (CH2Cl2
/CH3OH: 1/1) at ambient temperature for 2−3 days. An
ORTEP representation of the structure of 4a (Figure S1, see
the Supporting Information) shows that it is indeed a suitable
candidate for a 60° building unit, with the angle between the
two platinum coordination planes being approximately 62°.
The distance between the two Pt centers in 4a is 7.7 Å. All of
the atoms (except for the triethylphosphine ligands) lie
approximately in the same plane.
corresponding 60° dendritic diplatinum acceptors 1a−c in a 1:1
stoichiometric ratio in aqueous acetone (water/acetone 1/6)
overnight resulted in supramolecular metallodendritic triangles
6a−c, respectively. 31P{1H} NMR analysis of the reaction
mixtures is consistent with the formation of single, highly
symmetric species as indicated by the appearance of a sharp
singlet (ca. 11.8 ppm) with concomitant 195Pt satellites, shifted
upfield by ca. 7.2 ppm as compared to the precursors 1a−c
(Figure 2). In the 1H NMR spectrum of each assembly (Figure
3), the α-hydrogen nuclei of the pyridine rings exhibited 0.16−
0.67 ppm downfield shifts and the β-hydrogen nuclei showed
about 0.74−0.92 ppm downfield shifts because of the loss of
electron density that occurs upon coordination of the pyridine-
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Mass-spectrometric studies of triangular metallodendrimers
6a−c were performed by the cold-spray ionization (CSI)-TOF-
MS technique, which allows the assemblies to remain intact
during the ionization process in order to obtain the high
resolution required for unambiguous determination of individ-
ual charge-states.18 The high molecular weight and complex
isotope splitting of such charged multiplatinum species
necessitates high-resolution mass spectral analysis in order to
determine their absolute molecular weight and their molec-
ularity, which reveals the absolute stoichiometry of constituent
subunits and can definitively rule out the possibility of
byproduct assembly. All results of mass studies of assemblies
6a−c have provided strong support for the formation of
triangular metallodendrimers. In the CSI-TOF-MS spectrum of
[G-1] assembly 6a, for example, peaks at m/z = 2401.5 and m/
z = 1552.8, corresponding to the charge states [M − 2 PF6]2+
and [M − 3 PF6]3+, respectively, were observed and their
isotopic resolutions are in excellent agreement with the
theoretical distributions (Figure 4A). Similarly, the CSI-TOF-
MS spectrum of [G-2] triangular metallodendrimer 6b (Figure
4B) exhibited two charged states at m/z = 1977.1 and m/z =
1466.8, related to [M − 3 PF6]3+ and [M − 4 PF6]4+,
respectively. These peaks were isotopically resolved, and they
agree very well with their theoretical distribution. Given the
significantly larger molecular weight (8,906.8 Da) of the [G-3]
triangular metallodendrimer 6c it is more difficult to get strong
mass signals even under the CSI-TOF-MS conditions. With
considerable effort, the peak at m/z = 2083.19 was observed in
the CSI-TOF-MS spectrum of [G-3]-assembly 6c, which
corresponds to the [M − 4 PF6]4+charge state. This peak was
isotopically resolved and agrees with the theoretical distribu-
tion, although overlap with the signals of minor unknown
fragments was also observed (Figure 3C).
Figure 2. Partial 31P{1H} NMR spectra (400 MHz, CDCl3, 298K) of
[G-3] 60° di-Pt(II) acceptor 1c (A) and [G-3] triangular metal-
lodendrimer 6c (B).
Large supramolecular coordination compounds and flexible,
high-generation dendrimers often prove difficult to crystallize.
All attempts to grow X-ray quality single crystals of triangular
metallodendrimers 6a−c have proven to be unsuccessful to
date. Therefore, the geometry structures of the supramolecular
metallodendritic triangles 6a−c were optimized by PM6
semiempirical molecular orbital methods, respectively. In the
optimized structure (Figure 5), it was found that 6a−c have a
roughly planar triangular ring at its core surrounded by three-
component dendron subunits. The sides of the triangles 6a−c
are 4.0, 4.7, and 5.9 nm in length, respectively, and the internal
cavity is approximately 1.7 nm. Moreover, simulations reveal
that the underlying triangular structures, “scaffolds”, all retain
their planar and rigid structures even when derivatized with
dendrons units. In all cases, the flexible nature of the pendent
dendron moieties and the rigid nature of the triangular cavity
can be observed from modeling studies. In order to obtain
further structural information, the diffusion coefficient (D) of
newly designed dendritic triangles was determined by two-
dimensional diffusion-ordered NMR (DOSY) experiments.
1
Figure 3. Partial H NMR spectra (400 MHz, CDCl3, 298K) of 4,4′-
dipyridine (A) and [G-1]−[G-3] triangular metallodendrimers 6a (B),
6b (C), and 6c (D).
N atom with the Pt(II) metal center. It is noteworthy that the
existence of two sets of doublets for both the α- and β-pyridine
protons is an important characteristic feature of the 1H NMR of
these triangles.7a,14a Given that the pyridine rings of the side
unit and the phenanthrene system of the corner lie in the same
plane, the formation of the macrocyclic structure creates a
different environment for the inner and outer pyridine protons,
hence the different chemical shifts. The similar results have
been reported in the previous literature.7a,14a The sharp NMR
1
The H DOSY NMR measurements for assemblies 6a−c in
CDCl3 were carried out under similar conditions (3.06 × 10−3
mol/L, 293 K), respectively. It was found that the D values
decrease gradually with an increase of the molecular weight (see
the Supporting Information), which is in good agreement with
the modeling results.
signals in both the 31P{1H} and H NMR spectra (see the
Supporting Information) along with the solubility of these
species ruled out the formation of oligomers.
1
CONCLUSION
In summary, we have designed and synthesized a new class of
60° dendritic di-Pt(II) acceptor subunits, from which novel
■
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Figure 4. Theoretical (top) and experimental (bottom) CSI-TOF-MS spectra of [G-1]−[G-3] triangular metallodendrimers 6a (A), 6b (B), and 6c
(C).
Figure 5. Simulated molecular model of triangular metallodendrimers 6a (A), 6b (B), and 6c (C).
before use. Deuterated solvents and all other reagents were purchased
three-component triangular metallodendrimers can be easily
formed via [3 + 3] coordination-driven self-assembly, thus
enriching the library of dendritic metallacycles. More
importantly, compared to some previous reports of the
construction of supramolecular triangles, this study provides
highly efficient approach to the construction of such species
without any assistance of templates. All triangular metal-
lodendrimers were characterized with multinuclear NMR, CSI-
TOF-MS, and elemental analysis. Their structural properties
have been studied by using PM6 semiempirical molecular
orbital methods, which indicate that all metallodendrimers have
triangular rings with internal radii of approximately 1.7 nm.
This research has once again proven the versatility and
modularity of the directional bonding approach to self-
assembly, which surely will be employed for the synthesis of
other functional dendritic metallacycles in the future.
1
and used without further purification. H NMR, 13C NMR, and 31P
NMR spectra were recorded on a 300 MHz spectrometer (1H: 300
MHz; 13C: 75 MHz; 31P: 121.4 MHz) at 298 K or a 400 MHz
spectrometer (1H: 400 MHz; 13C: 100 MHz; 31P: 161.9 MHz) at 298
K. The 1H and 13C NMR chemical shifts are reported relative to
residual solvent signals, and 31P NMR resonances are referenced to an
internal standard sample of 85% H3PO4 (δ 0.0). Coupling constants
(J) are denoted in Hz and chemical shifts (δ) in ppm. Multiplicities are
denoted as follows: s = singlet, d = doublet, m = multiplet, t = triplet.
Synthetic Procedures. Synthesis of 3a−c. Under an
atmosphere of nitrogen, 2 (772 mg, 2.10 mmol), [G-n]-Br
(for G-0, 0.59 mL, 4.83 mmol; for G-1, 1.85 g, 4.83 mmol; for
G-2, 3.9 g, 4.83 mmol), and K2CO3 (2.9 g, 21.0 mmol) were
dissolved in DMF (25 mL). The mixture was heated at reflux
for 18 h and then cooled to room temperature. Solvent was
then distilled, and the resulting mixture was poured into water
and extracted with methylene chloride (15 mL × 3). The
methylene chloride solution was washed with water, dried over
anhydrous magnesium sulfate, and filtered. The crude products
were purified by column chromatography on silica gel
(dichloromethane/petroleum ether ∼1/1) to give compounds
3a−c.
EXPERIMENTAL SECTION
■
General Information. All reactions were performed under an
atmosphere of nitrogen unless stated otherwise. Toluene was distilled
from sodium/benzophenone. Dimethylformamide (DMF) was dis-
tilled before use. All solvents were degassed under N2 for 30 min
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3a. Yield: 0.58 g (white solid), 65%. Rf = 0.74 (dichloromethane/n-
hexane 1/1). Mp: 190−193 °C. 1H NMR (CDCl3, 300 MHz): δ 8.66
(s, 2H), 8.10 (d, J = 8.7 Hz, 2H), 7.69 (d, J = 6.3 Hz, 2H), 7.52−7.49
(m, 4H), 7.43−7.36 (m, 6H), 5.27 (s, 4H). 13C NMR (CDCl3, 75
MHz): δ 143.2, 136.9, 130.6, 129.0, 128.6, 128.4, 125.4, 124.3, 120.6,
75.5. MALDI-MS for C28H20Br2O2Na [(M + Na) +]: 569.00. IR (neat)
ν/cm−1: 2925, 1589, 1564, 1455, 1344, 1310, 1048, 813, 753, 734, 696.
3b. Yield: 0.92 g (white glassy solid), 45%. Rf = 0.50 (dichloro-
[(M − Br)+]: 2603.86. IR (neat) ν/cm−1: 2987, 2971, 2901, 2360,
1594, 1452, 1407, 1394, 1251, 1149, 1066, 1056, 892, 733, 697. Anal.
Calcd for C136H152Br2O14P4Pt2: C, 60.85; H, 5.71. Found: C, 61.19; H,
5.93.
Synthesis of 1a−c. A 50 mL round-bottom Schlenk flask was
charged with 0.066 mmol of bromide complexes 4a−c (for 4a, 99 mg,
0.07 mmol; for 4b, 128 mg, 0.07 mmol; for 4c, 188 mg, 0.07 mmol)
and 12 mL of dichloromethane. To the solution was added 56 mg
(0.33 mmol) of AgNO3 at once at room temperature, resulting in a
yellowish precipitate of AgBr. After 24 h, the suspension was filtered
through a glass fiber filter, and the filtrate was evaporated to dryness
under reduced pressure. Through this experimental procedure, the
yellow glassy solids were obtained as the desired products 1a−c.
1a. Yield: 80 mg (yellow crystalline solid), 83%. Mp: 81−83 °C. 1H
NMR (CDCl3, 400 MHz): δ 8.44 (s, 2H), 7.80 (d, J = 8.0 Hz, 2H),
7.60−7.55 (m, 6H), 7.43−7.34 (m, 6H), 5.26 (s, 4H), 1.3 (br, 24H),
1.20−1.12 (m, 36H). 13C NMR (CDCl3, 100 MHz): δ 141.7, 137.8,
135.7, 128.5, 128.22, 128.17, 128.0, 125.1, 124.7, 124.6, 124.5, 120.8,
75.1, 12.9, 12.8, 12.6, 7.5. 31P NMR (CDCl3, 161.9 MHz): δ 12.27 (s,
1JPt−P = 2888.3 Hz). CSI-TOF-MS for C52H80NO5P4Pt2 [(M −
NO3)+]: 1312.53. IR (neat) ν/cm−1: 2924, 2855, 1608, 1575, 1454,
1378, 1276, 1152, 1085, 1034, 824, 765, 733, 700. Anal. Calcd for
C52H80N2O8P4Pt2: C, 45.41; H, 5.86; N, 2.04. Found: C, 45.26; H,
5.96; N, 1.96.
1
methane/n-hexane 3/1). Mp: 150−152 °C. H NMR (CDCl3, 300
MHz): δ 8.67 (d, J = 1.5 Hz, 2H), 8.08 (d, J = 8.7 Hz, 2H), 7.69 (d, J =
9.0 Hz, 2H), 7.37−7.29 (m, 20H), 6.74 (d, J = 2.1 Hz, 4H), 6.57 (t, J =
2.1 Hz, 2H), 5.18 (s, 4H), 4.93 (s, 8H). 13C NMR (CDCl3, 75 MHz):
δ 160.1, 143.1, 139.3, 136.7, 130.7, 129.1, 128.6, 128.3, 128.0, 127.5,
125.5, 124.3, 120.7, 106.9, 101.9, 75.3, 70.1. MALDI-MS for
C56H44Br2O6Na [(M + Na)+]: 993.20. IR (neat) ν/cm−1: 2893,
1595, 1451, 1376, 1290, 1165, 1013, 819, 752, 730, 694. Anal. Calcd
for C56H44Br2O6: C, 69.14; H, 4.56. found: C, 69.10; H, 4.33.
3c. Yield: 1.45 g (white glassy solid), 38%. Rf = 0.36 (dichloro-
methane/n-hexane 4/1). Mp: 45− 47 °C. 1H NMR (CDCl3, 400
MHz): δ 8.65 (s, 2H), 8.09 (d, J = 8.8 Hz, 2H), 7.69 (d, J = 6.3 Hz,
2H), 7.34−7.28 (m, 40H), 6.72 (s, 4H), 6.62 (s, 8H), 6.51 (s, 6H),
5.15 (s, 4H), 4.93 (s, 16H), 4.82 (s, 8H). 13C NMR (CDCl3, 100
MHz): δ 160.1, 160.0, 143.2, 139.4, 139.2, 136.7, 130.7, 129.1, 128.5,
128.3, 127.9, 127.5, 124.3, 120.8, 106.8, 106.4, 102.0, 101.6, 70.0, 69.9.
MALDI-MS for C112H92Br2O14Na [(M + Na)+] 1841.60. IR (neat) ν/
cm−1: 2971, 2901, 2361, 1595, 1451, 1407, 1393, 1253, 1066, 892, 735,
697. Anal. Calcd for C112H92Br2O14: C, 73.84; H, 5.09. Found: C,
74.00; H, 5.30.
1
1b. Yield: 101 mg (yellow glassy solid), 80%. Mp: 59−61 °C. H
NMR (CDCl3, 400 MHz): δ 8.44 (s, 2H), 7.78 (d, J = 8.4 Hz, 2H),
7.59 (d, J = 8.0 Hz, 2H), 7.37−7.33 (m, 20H), 6.82 (s, 4H), 6.56 (s,
2H), 5.20 (s, 4H), 4.92 (s, 8H), 1.54−1.52 (m, 24H), 1.17−1.13 (m,
36H). 13C NMR (CDCl3, 100 MHz): δ 160.1, 141.5, 140.3, 136.7,
135.8, 128.6, 128.2, 128.0, 127.6, 124.9, 124.8, 120.7, 106.7, 101.3,
74.8, 70.0, 12.9, 12.8, 12.6, 7.8, 7.5. 31P NMR (CDCl3, 161.9 MHz): δ
19.29 (s, 1JPt−P = 2870.5 Hz). CSI-TOF-MS for C80H104NO9P4Pt2 [(M
− NO3)+]: 1736.73. IR (neat) ν/cm−1: 2960, 2925, 2871, 2736, 2353,
1670, 1595, 1453, 1378, 1262, 1152, 1084, 1035, 804, 765, 734, 698.
Anal. Calcd for C80H104N2O12P4Pt2: C, 53.39; H, 5.82; N, 1.56. Found:
C, 53.74; H, 6.05; N, 1.38.
Synthesis of 4a−c. A 50-mL Schlenk flask was charged under
nitrogen with 3a−c (for 3a, 72 mg, 0.13 mmol; for 3b, 126 mg, 0.13
mmol; for 3c, 237 mg, 0.13 mmol) and Pt(PEt3)4 (334 mg, 0.5 mmol).
Freshly distilled toluene (8.0 mL) was added to the flask under
nitrogen by syringe, and the resulted bright yellow solution was stirred
for 72 h at 99 °C. The solvent was then removed in vacuo. The residue
was washed with methanol (4 × 2.0 mL) and purified by column
chromatography on silica gel (dichloromethane/methyl alcohol ∼500/
1) to give compounds 4a−c.
1
1c. Yield: 265 mg (white glassy solid), 69%. Mp: 39−43 °C. H
4a. Yield: 158 mg (yellow crystalline solid), 86%. Rf = 0.63
(dichloromethane/methyl alcohol 500/1). Mp: 155−157 °C. 1H
NMR (CDCl3, 400 MHz): δ 8.51 (s, 2H), 7.84 (d, J = 8.0 Hz, 2H),
7.59−7.57 (m, 6H), 7.43−7.34 (m, 6H), 5.28 (s, 4H), 1.69−1.68 (m,
24H), 1.12−1.04 (m, 36H). 31P NMR (CDCl3, 161.9 MHz): δ 12.69
(s, 1JPt−P = 2763.6 Hz). 13C NMR (CDCl3, 100 MHz): δ 141.6, 138.1,
137.74, 127.65, 126.3, 129.3, 128.4, 128.2, 127.9, 124.7, 120.6, 75.0,
14.3, 14.1, 14.0, 7.78, 7.72. CSI-TOF-MS for C52H80BrO2P4Pt2 [(M −
Br)+]: 1331.46. IR (neat) ν/cm−1: 2962, 2874, 2361, 2343, 1661,
1572, 1454, 1085, 1306, 1034, 821, 765, 730, 696. Anal. Calcd for
C52H80Br2O2P4Pt2: C, 44.26; H, 5.71. Found: C, 44.51; H, 5.94.
4b. Yield: 215 mg (yellow glassy solid), 90%. Rf1 = 0.56
(dichloromethane/methyl alcohol 500/1). Mp: 71−74 °C. H NMR
(CDCl3, 400 MHz): δ 8.52 (s, 2H), 7.79 (d, J = 8.0 Hz, 2H), 7.60 (d, J
= 8.0 Hz, 2H), 7.37−7.29 (m, 20H), 6.85 (s, 4H), 6.56 (s, 2H), 5.23
(s, 4H), 4.93 (s, 8H), 1.69−1.68 (m, 24H), 1.11−1.04 (m, 36H). 31P
NMR (CDCl3, 161.9 MHz): δ 12.68 (s, 1JPt−P = 2762.0 Hz). 13C NMR
(CDCl3, 100 MHz): δ 160.1, 141.5, 130.5, 137.8, 136.9, 136.5, 129.4,
128.6, 128.0, 127.6, 124.5, 120.6, 106.8, 101.4, 74.8, 70.1, 14.3, 14.1,
14.0, 7.8. CSI-TOF-MS for C80H104Br2O6P4Pt2Na [(M − Br)+]:
1755.68. IR (neat) ν/cm−1: 2962, 2931, 2907, 2872, 2353, 1672, 1594,
1452, 1374, 1151, 1033, 825, 764, 731, 697. Anal. Calcd for
C80H104Br2O6P4Pt2: C, 52.35; H, 5.71. found: C, 52.69; H, 5.79.
4c. Yield: 265 mg (white glassy solid), 76%. Rf1 = 0.51
(dichloromethane/methyl alcohol 500/1). Mp: 46−51 °C. H NMR
(CDCl3, 400 MHz): δ 8.53 (s, 2H), 7.83 (d, J = 7.6 Hz, 2H), 7.62 (d, J
= 8.4 Hz, 2H), 7.34−7.29 (m, 40H), 6.82 (s, 4H), 6.63 (s, 8H), 6.51
(s, 6H), 5.21 (s, 4H), 4.93 (s, 16H), 4.80 (s, 8H), 1.68 (br, 24H),
1.10−1.04 (m, 36H). 31P NMR (CDCl3, 121.4 MHz): δ 12.48 (s,
1JPt−P = 2729.1 Hz). 13C NMR (CDCl3, 100 MHz): δ 160.1, 160.0,
141.5, 140.5, 139.3, 139.2, 136.7, 136.5, 129.3, 128.5, 128.3, 127.9,
127.7, 127.5, 124.5, 120.5, 106.7, 106.5, 106.4, 101.5, 101.4, 74.8, 70.0,
69.9, 14.3, 14.1, 13.9, 7.8, 7.7. CSI-TOF-MS for C136H152BrO14P4Pt2
NMR (CDCl3, 400 MHz): δ 8.46 (s, 2H), 7.82 (d, J = 7.6 Hz, 2H),
7.61 (d, J = 8.8 Hz, 2H), 7.34−7.28 (m, 40H), 6.80 (s, 4H), 6.63 (s,
8H), 6.51 (s, 6H), 5.20 (s, 4H), 4.93 (d, J = 9.6 Hz, 16H), 4.80 (s,
8H), 1.52 (br, 24H), 1.15−1.13 (m, 36H). 13C NMR (CDCl3, 100
MHz): δ 160.1, 160.0, 141.6, 140.2, 139.1, 136.7, 135.9, 128.5, 128.3,
128.2, 128.0, 127.5, 125.0, 120.7, 106.7, 106.5, 101.4, 74.8, 70.0, 69.9,
12.9, 12.8, 12.6, 7.8, 7.5. 31P NMR (CDCl3, 161.9 MHz): δ 19.00 (s,
1JPt−P = 2888.3 Hz). CSI-TOF-MS for C136H152NO17P4Pt2 [(M −
2NO3)2+]: 1262.07. IR (neat) ν/cm−1: 2964, 2928, 2875, 2736, 2352,
1669, 1596, 1452, 1378, 1277, 1154, 1084, 1036, 824, 765, 735, 699.
Anal. Calcd for C136H152N2O20P4Pt2·H2O: C, 61.25; H, 5.82; N, 1.05.
Found: C, 61.03; H, 5.97; N, 1.17.
General Procedure for the Preparation of Supramolecular
Triangular Metallodendrimers 6a−c. 4.5 mL mixed solvents of
acetone and H2O (v/v 6/1) were added to a mixture of nitrate salts
1a−c (for 1a, 17.7 mg, 0.0129 mmol; for 1b, 23.1 mg, 0.0129 mmol;
for 1c, 34.1 mg, 0.0129 mmol) and the appropriate donor building
block 4,4′-bipyridyl (2.01 mg, 0.0129 mmol). The reaction mixture was
then stirred for 14 h at 55−60 °C, upon which starting materials were
completely dissolved and the reaction mixture attained a yellow color.
−
The PF6− salt of 6a−c was synthesized by dissolving the yellow NO3
salt 6a−c in acetone/H2O and adding a saturated aqueous solution of
KPF6 to precipitate the product, which was collected by vacuum
filtration.
1
6a. Yield: 19.1 mg (yellow solid), 97%. H NMR (CDCl3, 400
MHz): δ 9.38 (d, J = 5.2 Hz, 6H), 8.89 (d, J = 4.8 Hz, 6H), 8.80 (s,
6H), 8.44 (d, J = 5.2 Hz, 6H), 8.29 (d, J = 5.6 Hz, 6H), 7.97 (d, J = 8.0
Hz, 6H), 7.61−7.59 (m, 18H), 7.46−7.39 (m, 18H), 5.33 (s, 12H),
1.38 (br, 72H), 1.18−1.13 (m, 108H). 13C NMR (CDCl3, 100 MHz):
δ 154.0, 152.9, 144.6, 141.9, 137.8, 135.2, 129.3, 128.5, 128.3, 128.1,
126.0, 125.4, 124.4, 121.1, 75.2, 13.0, 12.8, 12.6, 7.6. 31P NMR
1
(CDCl3, 161.9 MHz): δ 11.82 (s, JPt−P = 2700.5 Hz). CSI-TOF-MS,
[M − 2PF6]2+, 2401.53; [M − 3PF6]3+, 1552.82. Anal. Calcd for
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The Journal of Organic Chemistry
Article
C186H264F36O6N6P18Pt6: C, 43.87; H, 5.23; N, 1.65. found: C, 43.87;
H, 5.38; N, 1.66.
6b. Yield: 23.9 mg (yellow solid), 95%. H NMR (CDCl3, 300
Vladimirov, N.; Frechet, J. M. J. J. Am. Chem. Soc. 2001, 123, 18.
(c) Marsitzky, D.; Vestberg, R.; Blainey, P.; Tang, B. T.; Hawker, C. J.;
Carter, K. R. J. Am. Chem. Soc. 2001, 123, 6965. (d) Le Derf, F.;
́
1
MHz): δ 9.42 (d, J = 5.4 Hz, 6H), 8.89 (d, J = 5.4 Hz, 6H), 8.84 (s,
6H), 8.45 (d, J = 5.7 Hz, 6H), 8.25 (d, J = 5.7 Hz, 6H), 7.96 (d, J = 8.1
Hz, 6H), 7.59 (d, J = 8.4 Hz, 6H), 7.40−7.33 (m, 60H), 6.85 (s, 12H),
́ ́
Levillain, E.; Trippe, G.; Gorgues, A.; Salle, M.; Sebastian, R.-M.;
Caminade, A.-M.; Majoral, J.-P. Angew. Chem., Int. Ed. 2001, 40, 224.
(e) Gong, L.-Z.; Hu, Q.-S.; Pu, L. J. Org. Chem. 2001, 66, 2358.
(4) (a) Chase, P. A.; Gebbink, R. J. M. K.; van Koten, G. J.
Organomet. Chem. 2004, 689, 4016. (b) Oosterom, G. E.; Reek, J. N.
H.; Kamer, P. C. J.; van Leeuwen, P. W. N. M. Angew. Chem., Int. Ed.
2001, 40, 1828. (c) Dendrimer Catalysis; Gade, L., Ed.; Springer:
Heidelberg, 2006.
6.60 (s, 6H), 5.27 (s, 12H), 4.96 (s, 24H), 1.37 (m, 72H), 1.18−1.08
1
(m, 108H). 31P NMR (CDCl3, 121.4 MHz): δ 11.81 (s, JPt−P
=
2718.1 Hz). CSI-TOF-MS, [M − 3PF6]3+, 1977.07; [M − 4PF6]4+,
1446.81. Anal. Calcd for C270H336F36O18N6P18Pt6: C, 50.94; H, 5.32;
N, 1.32. Found: C, 50.92; H, 5.49; N, 1.12.
6c. Yield: 33.6 mg (yellow solid), 93%. 1H NMR (CDCl3, 400
MHz): δ 9.41 (br, 6H), 8.88−8.84 (m, 12H), 8.45 (d, J = 4.0 Hz, 6H),
8.28 (br, 6H), 8.00 (d, J = 7.6 Hz, 6H), 7.61 (d, J = 8.0 Hz, 6H), 7.36−
7.30 (m, 120H), 6.83 (s, 12H), 6.66 (s, 24H), 6.54 (s, 18H), 5.26 (s,
(5) (a) Balzani, V.; Ceroni, P.; Juris, A.; Venturi, M.; Campagna, S.;
Puntoriero, F.; Serroni, S. Coord. Chem. Rev. 2001, 219, 545.
(b) Andronov, A.; Frec
(c) Freeman, A. W.; Koene, C.; Malenfant, P. R. L.; Thompson, M. E.;
Frechet, J. M. J. J. Am. Chem. Soc. 2000, 122, 12385. (d) Weener, J.-W.;
́
het, J. M. J. Chem. Commun. 2000, 1701.
12H), 4.96 (s, 48H), 4.84 (s, 24H), 1.38−1.36 (m, 72H). 1.15−1.11
́
1
(m, 108H). 31P NMR (CDCl3, 161.9 MHz): δ 11.89 (s, JPt−P
=
Meijer, E. W. Adv. Mater. 2000, 12, 741. (e) Newkome, G. R.; He, E.;
Godínez, L. A.; Baker, G. R. J. Am. Chem. Soc. 2000, 122, 9993.
(f) Lupton, J. M.; Samuel, I. D. W.; Beavington, R.; Burn, P. L.;
2703.7 Hz). CSI-TOF-MS, [M − 4PF6]4+, 2083.19.
ASSOCIATED CONTENT
Bassler, H. Adv. Mater. 2001, 13, 258.
̈
■
(6) (a) Svenson, S.; Tomalia, D. A. Commentary. Adv. Drug Delivery
S
* Supporting Information
́
Rev. 2005, 57, 2106. (b) Gillies, E. R.; Frechet, J. M. J. Drug Discovery
Crystal data and structure of 4a, characterization of the
Today 2005, 10, 35. (c) Boas, U.; Christensen, J. B. Dendrimers in
Medicine and Biotechnology; Royal Chemical Society Publishing:
Cambridge, U.K., 2006. (d) Dendrimer-Based Nanomedicine;
Majoros, I. J., Baker, J. R., Jr., Eds.; Pan Stanford Publishing:
Stanford, CA, 2008.
compounds 3a−c, 4a−c, and 1a−c, H and 31P NMR spectra
1
of 6a−c, and 1H DOSY NMR spectra of 6a−c. This material is
available free of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*E-mail: hbyang@chem.ecnu.edu.cn.
(7) For selected reviews, see: (a) Zeng, F.; Zimmerman, S. C. Chem.
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Chem. Rev. 1999, 99, 1689. (c) Bosman, A. W.; Janssen, H. M.; Meijer,
■
E. W. Chem. Rev. 1999, 99, 1665. (d) Frec
Sci. U.S.A. 2002, 99, 4782.
́
het, J. M. J. Proc. Natl. Acad.
Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS
■
Prof. H.-B. Yang thanks the NSFC (91027005 and 21132005),
Shanghai Shuguang Program (09SG25), Innovation Program of
SMEC (10ZZ32), RFDP (20100076110004) of Higher
Education of China, and “the Fundamental Research Funds
for the Central Universities” for financial support.
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