Synthesis of organoplatinum poly (dendrimer)s: Pronounced effect of size and geometry of small organoplatinum linkers on the copolymerization efficiency with bifunctional dendritic macromonomers

Article abstract of DOI:10.1002/chem.200900880

The copolymerizations of two series of surface functionalized bis(acetylene) G1-G3 dendrimers, one (S-Gn) having a structural rigid skeleton and the other (L-Gn) a relatively more flexible architecture, with two platinum linkers, cis-[(Et₂PCH₂CH₂PEt ₂)PtCl₂] (2) and [Cl-(Et₃P)₂Pt- C≡C-P-C₆H₄-], (3) were investigated. For both series of dendrimers, only linear and/or cyclic oligomers were formed when the cis-platinum linker 2 was used. However, high molecular weight (100-200 kD) organoplatinum poly(dendrimer)s were obtained from both series when the elongated linear rod-liked platinum linker 3 was employed and the formation of cyclic oligomers was greatly suppressed for both the structural rigid S-Gn and the structural flexible L-Gn series. These results are in sharp contrast to our earlier findings (S.-Y. Cheung, H.-F. Chow, T. Ngai, X. Wei, Chem. Eur. J. 2009, 75, 2278-2288) obtained by using a shorter linear platinum linker trans-[Pt-(PEt₃)₂Cl₂] (1), where a larger amount of cyclic oligomers was formed from the structural flexible L-Gn dendrimers. A model was proposed to rationalize how the geometry and size of the platinum linker could control the copolymerization behaviours of these dendritic macromonomers.

Full text of DOI:10.1002/chem.200900880

DOI: 10.1002/chem.200900880
Synthesis of Organoplatinum PolyACTHNUTRGNE(NUG dendrimer)s: Pronounced Effect of Size
and Geometry of Small Organoplatinum Linkers on the Copolymerization
Efficiency with Bifunctional Dendritic Macromonomers
Siu-Yin Cheung[a] and Hak-Fun Chow*[a, b]
Abstract: The copolymerizations of
two series of surface functionalized bi-
s(acetylene) G1–G3 dendrimers, one
(S-Gn) having a structural rigid skele-
ton and the other (L-Gn) a relatively
more flexible architecture, with two
lecular weight (100–200 kD) organopla-
tinum poly(dendrimer)s were obtained
from both series when the elongated
linear rod-liked platinum linker 3 was
employed and the formation of cyclic
oligomers was greatly suppressed for
both the structural rigid S-Gn and the
structural flexible L-Gn series. These
results are in sharp contrast to our ear-
lier findings (S.-Y. Cheung, H.-F. Chow,
T. Ngai, X. Wei, Chem. Eur. J. 2009, 15,
2278–2288) obtained by using a shorter
linear platinum linker trans-[Pt-
AHCTNUGRTEG(NNNU PEt3)2Cl2] (1), where a larger amount
of cyclic oligomers was formed from
the structural flexible L-Gn dendrim-
ers. A model was proposed to rational-
ize how the geometry and size of the
platinum linker could control the co-
polymerization behaviours of these
dendritic macromonomers.
platinum
linkers,
cis-
[(Et2PCH2CH2PEt2)PtCl2] (2) and [Cl-
ꢀ
G
vestigated. For both series of dendrim-
ers, only linear and/or cyclic oligomers
were formed when the cis-platinum
linker 2 was used. However, high mo-
Keywords: dendrimers · platinum ·
polymerization
Introduction
polymers,[3] poly(dendrimer)s,[4] poly(dendrimer) networks[5]
have already been reported. While there have been exten-
sive studies on dendrimer–linear polymer hybrids and
dendronized polymers, there are only a handful of examples
on poly(dendrimer)s.[4,5] One unique feature in the synthesis
of poly(dendrimer)-based molecules is that dendrimer con-
nection is formed via the two functionalities located on the
dendrimer surface (outer-sphere–outer-sphere connection)
(Scheme 1). This synthetic approach is therefore anticipated
to experience less steric retardation than the graft to-, graft-
from, or macromonomer polymerization strategies used for
the synthesis of dendronized polymers,[3] in which dendrimer
connection is realized via functional group(s) anchored near
the sterically more hindered focal point position (inner-
sphere–inner-sphere connection).
The synthesis of nanoscopic architectures with controllable
size and shape from dendritic building blocks has become a
subject of topic interest due to their potential catalysis, bio-
logical, and diagnostic applications.[1] One inherent advant-
age of using dendrimers as the basic structural motif is be-
cause of their high structural homogeneity and well-defined
three-dimensional topology, which enable one to exert
better control on the final dimension and shape of, and func-
tional group location in the target architecture. Many cova-
lently-linked structures based on dendritic building blocks
such as dendrimer–linear polymer hybrids,[2] dendronized
[a] S.-Y. Cheung, Prof. Dr. H.-F. Chow
Department of Chemistry
We reported earlier that poly(dendrimer)s with a high
degree of polymerization (DP) value (30–1000 based on
laser light scattering data) could be obtained from the co-
polymerization of surface functionalized bis(acetylene) den-
The Chinese University of Hong Kong
Shatin, NT, Hong Kong SAR (China)
Fax : (+852)26035057
dritic macromonomers and trans-[PtACTHNUTRGNEUNG
(PEt3)2Cl2] (1).[4b] To
E-mail: hfchow@cuhk.edu.hk
[b] Prof. Dr. H.-F. Chow
further elaborate on the general efficiency of this synthetic
strategy, we later modified the backbone structure of the
dendritic macromonomers and found that structurally more
rigid Frꢀchet type oligo(benzyl ether) dendrimers S-Gn (n=
1–3) tended to give organoplatinum poly(dendrimer)s trans-
The Center of Novel Functional Molecules
The Chinese University of Hong Kong
Shatin, NT, Hong Kong SAR (China)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.200900880.
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Chem. Eur. J. 2009, 15, 8874 – 8879

FULL PAPER
Scheme 1. a) Synthesis of dendronized polymer via focal point functional
group connection and b) poly(dendrimer) via surface functional group
connection.
Scheme 2. Cyclization vs polymerization for S-Gn and L-Gn with trans-
[PtACTHUNTGRNENUG(PEt3)2Cl2] 1.
even the sterically bulky G3 macromonomers could be co-
polymerized to form poly(dendrimer)s of high molecular
weight (Mw ~150–190 kD based on SEC calculations). This
present study reveals that there are intrigue factors that con-
trol the cyclization versus propagation pathways during the
copolymerization process, and that one can control the for-
mation of the oligomers versus poly(dendrimer)s by careful
design of the macromonomer and linker group. It was noted
that formation of cyclic oligomers involving structurally flex-
ible small monomers[6] and macromonomers[7] had been re-
ported before.
Results and Discussion
The syntheses of the surface functionalized bis(acetylene)
dendrimers S-Gn or L-Gn had been reported earlier,[4c]
while the organoplatinum complexes 2[8] and 3[5] were pre-
pared according to literature methods. The copolymerization
of S-Gn/L-Gn with organoplatinum complexes 2 or 3 is a
step-growth reaction and involves the polycondensation of
the terminal acetylene moiety on the dendrimer surface
Pt-S-Gn with higher DP values than structurally more flexi-
ble oligo(3-phenylpropyl ether) dendrimers L-Gn (n=1–
3).[4c] The main problem associated with the latter class of
dendritic monomers was their relatively higher propensity to
form cyclic oligomers due to the presence of the more flexi-
ble and elongated branches (Scheme 2). The DP values of
the poly(dendrimer)s obtained from this study ranged from
20–60 (based on SEC data). However, the weight% of the
cyclic oligomers (calculated up to the pentamer) obtained
could be as high as 14%.
À
with the platinum chlorine bond. The reactions were con-
ducted under reaction conditions (8.7 mm; CuI, iPr2NH,
CHCl3, 408C, 48 h) that were identical to those involving
trans-[Pt
effect of the platinum linkers on the formation of the poly-
ACHTUNGTREN(NUGN dendrimer)s (Scheme 3). After polymerization, the yellow
(PEt3)2Cl2] (1)[4b] in order to evaluate the structural
ACHTUNGTRENNUNG
In this paper we wish to report that changing the small or-
ganoplatinum linker and hence its geometry, size and rigidi-
ty also has a profound effect on the polymerization efficien-
cy. Hence, no poly(dendrimer)s, but only oligomers were
formed from using the cis-[(Et2PCH2CH2PEt2)PtCl2] (2)
linker. On the other hand, formation of cyclic oligomers was
greatly suppressed if an elongated linear rigid rod organo-
ꢀ
products, cis-Pt-S-Gn, cis-Pt-L-Gn, long-trans-Pt-S-Gn and
long-trans-Pt-L-Gn were isolated by passing them through a
short column of alumina and washing with CHCl3 to remove
the copper salt, followed by precipitation in MeOH. The re-
sulting polymers were subjected to 1H, 13C, and 31P NMR
spectroscopic characterizations. On the other hand, size-ex-
clusion chromatographic (SEC) analyses were performed on
samples obtained prior to precipitation to ensure the SEC
platinum complex [ClACHTNUTRGNE(NUG Et3P)2Pt-C C-p-C6H4-]2 (3) was used
as the linker. By using this elongated linker, we showed that
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8875

H.-F. Chow and S.-Y. Cheung
Scheme 3. 1:
1 Copolymerizations of S-Gn and L-Gn with cis-
[(Et2PCH2CH2PEt2)PtCl2] 2 and elongated trans-platinum linker 3. a)
CuI, iPr2NH, CHCl3, 408C, 48 h.
results reflected the full molecular weight distribution and
not just that of the precipitated fractions.
Copolymerizations with cis-platinum linker 2: Examination
1
of the H NMR spectra of the various cis-Pt-L-Gn and cis-
Pt-S-Gn revealed the presence of both the dendritic and the
cis-platinum linker moieties (see Supporting Information for
details). However, their 31P{1H} NMR spectra showed that
presence of many peaks (Figure 1), suggesting the product
Figure 2. SEC chromatograms of a) cis-Pt-S-G1, b) cis-Pt-L-G1, c) cis-Pt-
S-G2, d) cis-Pt-L-G2, e) cis-Pt-S-G3, and f) cis-Pt-L-G3 (solid lines). The
dotted lines are SEC traces of the corresponding dendritic macromono-
mers (data taken from reference [4c]).
Table 1. SEC data of cis-Pt-S-Gn and cis-Pt-L-Gn oligomers.[a]
Sample
SEC Mw ꢂ 10À3[b]
DP[b]
PDI[b]
cis-Pt-S-G1
cis-Pt-S-G2
cis-Pt-S-G3
cis-Pt-L-G1
cis-Pt-L-G2
cis-Pt-L-G3
3
6
6
4
7
13
3
3
2
3
3
3
1.6
1.5
1.3
2.1
1.6
1.6
Figure 1. 31P{1H} NMR spectra (122 MHz, CDCl3) of a) cis-Pt-L-G2 and
b) cis-Pt-S-G2, showing sets of 31P signals together with the correspond-
ing 195Pt satellite peaks.
[a] SEC conditions: Waters Styragel columns (HR1, HR2, HR3 and
HR4; 7.8ꢂ300 mm in serial) at 408C using THF as eluent (flow rate=
1.0 mLmin-1) on a Waters HPLC 515 pump with a Waters 2489 tunable
UV absorbance detector. [b] Values calculated from SEC data based on
polystyrene standards.
had a very high degree of heterogeneity. More strikingly, the
SEC chromatograms of the products showed the presence of
mainly oligomeric species (Figure 2). The degree of poly-
merization (DP) values, as calculated based on polystyrene
standards, were around 2–3 (Table 1) and the polydispersity
indexes (PDI) ranged from 1.3–2.1. Mass spectral analyses
of the slowest running SEC fraction from the various cis-Pt-
L-Gn and cis-Pt-S-Gn samples confirmed that they were un-
reacted dendritic macromonomer, 1:1 Pt–dendritic monomer
adduct, cyclic monomer, and/or their fragmentation prod-
ucts (Figure 3). The preferential formation of cyclic metallo-
oligomers from non-linear platinum linkers and preorgan-
ized dendritic ligands had been reported before.[8] The re-
sults obtained here suggested that the geometry of the small
platinum linker played an important role in controlling the
outcome of the polymerization process. The placement of
two dendritic macromonomers at a 908 relationship at the
platinum metal center would create severe steric congestion
and angle strain of the resulting complex. As a result, the
polymerization process was strongly disfavored and only
oligomers/cyclic oligomers were formed from using the 908
cis-platinum complex 2.
Copolymerizations with long-trans-platinum linker 3: The
1H and 13C NMR spectra of long-trans-Pt-S-Gn and long-
trans-Pt-L-Gn again showed the presence of both the den-
dritic and platinum components. In sharp contrast to those
of the cis-Pt-L-Gn and cis-Pt-S-Gn, the 31P{1H} spectra of
these poly(dendrimer)s consisted mainly of one major peak
(see Supporting Information for details), suggesting the
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Chem. Eur. J. 2009, 15, 8874 – 8879

Synthesis of Organoplatinum Poly(dendrimer)s
FULL PAPER
peaks due to the cyclic oligomers that were so prominent in
the SEC chromatographs of the poly(dendrimer)s obtained
from the copolymerization of the same dendritic macromo-
nomers with the shorter platinum linker trans-[PtACHTUNGTRNEG(UN PEt3)2Cl2]
(1), were greatly suppressed. Since the individual oligomeric
peaks could not be clearly picked out, we were unable to
calculate the weight% of the low molecular weight (LMW)
oligomers in the present study. Nonetheless, it could be
clearly seen that the amount of LMW oligomers was greatly
suppressed by switching the platinum linker from the short-
er linker 1 to the longer one 3. Second, both the S-Gn and
L-Gn macromonomers copolymerized well with the longer
platinum linker 3 to form poly(dendrimer)s with high DP
values (Table 2). It was noted that the DP values obtained
Table 2. SEC data of long-trans-Pt-S-Gn and long-trans-Pt-L-Gn poly-
AHCTUNGTRENNUNG
(dendrimer)s.[a]
Sample
SEC Mw ꢂ 10À3[b]
DP[b]
PDI[b]
59 (34)[c]
72 (60)[c]
34 (21)[c]
46 (39)[c]
41 (22)[c]
36 (19)[c]
2.5
2.3
2.2
2.0
2.0
1.9
Figure 3. MALDI-TOF spectrum of the slowest running SEC fraction
from cis-Pt-S-G2.
long-trans-Pt-S-G1
long-trans-Pt-S-G2
long-trans-Pt-S-G3
long-trans-Pt-L-G1
long-trans-Pt-L-G2
long-trans-Pt-L-G3
107
191
148
91
127
188
polymerization reactions proceeded smoothly to give poly-
ACHTUNGTRENNUNG(dendrimer)s of high DP values. The appearance of the SEC
[a] SEC conditions: Waters Styragel columns (HR1, HR2, HR3 and
HR4; 7.8ꢂ300 mm in serial) at 408C using THF as eluent (flow rate=
1.0 mLminÀ1) on a Waters HPLC 515 pump with a Waters 2489 tunable
UV absorbance detector. [b] Values calculated from SEC data based on
polystyrene standards. [c] Number in parenthesis referred to the corre-
chromatograms was even more astonishing (Figure 4). First,
sponding value obtained from using the shorter trans-[PtACHTUNGTRENNUNG(PEt3)2Cl2]
linker. The data were extracted from reference [4c].
from the structurally rigid S series were still larger than that
of the structurally flexible L series of the same generation,
indicating the structural flexibility of the macromonomers
still exerted the same role in controlling the polymerization
process. Third, a major peak with a shorter retention time as
compared to the corresponding trans-Pt-S/L-Gn was found
in all cases. SEC calculations also confirmed that the DP
values of the long-trans-Pt-S/L-Gn poly(dendrimer)s were
consistently higher than those of the trans-Pt-S/L-Gn poly-
AHCTUNGTREG(NNNU dendrimer)s. Fourth, both third-generation macromono-
mers S-G3 and L-G3, previously found to have problems to
undergo copolymerization, could form organoplatinum poly-
AHCTUNGTREG(NNNU dendrimer)s with good DP values with the longer rod-liked
linker 3. It should be pointed out here that although the
SEC calculated DP values are in the order of 102, the actual
DP values can be 1.5–14 times higher as the hyperbranched
poly(dendrimer)s have a much larger mass per unit length
than the polystyrene standards.[4b] Unfortunately, we were
unable to obtain their absolute molecular weights by laser
light-scattering studies as they tended to form large aggre-
gates in relatively concentrated solutions.[4c] On the other
hand, the SEC experiments were conducted in highly dilut-
ed THF solutions at elevated temperature (408C), under
which conditions aggregate formation was greatly sup-
pressed.
Figure 4. SEC chromatograms of a) long-trans-Pt-S-G1, b) long-trans-Pt-
L-G1, c) long-trans-Pt-S-G2, d) long-trans-Pt-L-G2, e) long-trans-Pt-S-
G3, and f) long-trans-Pt-L-G3. The dotted lines are plots of the corre-
sponding trans-Pt-L-Gn or trans-Pt-S-Gn taken from reference [4c].
Chem. Eur. J. 2009, 15, 8874 – 8879
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8877

H.-F. Chow and S.-Y. Cheung
Based on the experimental results obtained from this and
our previous studies,[4c] a model was proposed to rationalize
the various observations in the copolymerizations between
the different platinum linkers and the dendritic macromono-
mers (Scheme 4). The addition of the first dendritic macro-
this process must be slower as compared to the correspond-
ing step in 3. In this situation, the second acetylenic func-
tionality of the first macromonomer may have enough op-
portunity and time to react with the Pt metal center to form
cyclic monomers/oligomers (path F). This then creates a
unique situation where the structural rigidity of the macro-
monomer can exert its control on the extent of propagation
versus cyclic oligomerization. The L series, having a flexible
structure and hence a high degree of freedom to orient the
second acetylenic group to the Pt center, will have a higher
opportunity than the rigid S series to form cyclic oligomers.
This is also the reason why a clear difference in the poly-
merization behaviour can only be observed between the two
series of dendritic macromonomers with platinum linker 1.
Conclusions
The synthesis of organoplatinum poly(dendrimer)s by the
copolymerizations of surface-bifunctional dendritic macro-
monomers with two small platinum linker molecules 2 and 3
were reported. It was found that the geometry and the size
of the platinum linker could exert a profound effect on the
polymerization efficiency. The cis-Pt linker 2 produced
mainly oligomers with both the structural rigid S series and
structural flexible L series of macromonomers. On the other
hand, poly(dendrimer)s with high DP values were obtained
from the long-trans-Pt linker 3. The formation of cyclic olig-
omers, and the differential behaviour of the S and L series
observed during copolymerizations with the shorter trans-
[PtACTHUNTGRNEUGN(PEt3)2Cl2], was not found with the long-trans-Pt linker 3.
A model was formulated to rationalize the various observa-
tions. We believe this working model can also be used to
predict the cyclization versus propagation pathways of other
polymerization reactions involving macromonomers. More
importantly, we demonstrated that even the G3 dendritic
macromonomers could copolymerize efficiently to give pol-
y(dendrimer)s of Mw values of 150–190 kD (based on SEC
data), suggesting the outer-sphere-outer-sphere connection[1]
is a viable strategy to construct nanoscopic-sized materials
with controlled architecture.
Scheme 4. Polymerization vs cyclization of dendritic macromonomers
with Pt-linkers.
monomer to the platinum linker should be a relatively facile
process. However, addition of the second macromonomer is
subjected to stronger steric inhibition due to the anchorage
of the first macromonomer. Among the three platinum link-
ers, the steric environment around the long-trans-Pt-linker 3
is the least congested due to the larger spatial separation of
À
the two Pt Cl bonds. As a result, addition of the second
macromonomer should be more facile and both the rigid S
and flexible L series of macromonomers can undergo co-
polymerization efficiently (path A), and cyclization is great-
ly suppressed (path B). On the other hand, the steric envi-
ronment around the cis-Pt-linker 2 is the most congested, as
Experimental Section
General information: The cis-Pt linker 2[9] and the elongated trans-Pt
linker 3[5] were prepared according to literature procedure. For the cis-
Pt-S-Gn and cis-Pt-L-Gn poly(dendrimer)s (n=1, 2 and 3), they are mix-
ture of oligomers and cyclic oligomers even after precipitation, therefore
the NMR data were just taken for recording purpose. Details of which
are given in the Supporting Information.
À
the remaining Pt Cl bond is located cis to the first macro-
monomer with a 908 bonding angle. In this case, addition of
the second macromonomer to the same Pt center is strongly
prohibited (path C) and therefore only LMW oligomers (DP
~2–3) are formed (path D), regardless of the structural ri-
gidity of the macromonomer. For the trans-Pt-linker 1, steric
congestion around the Pt center must be less than that in 2,
but stronger than that in 3. In this case, addition of the
second macromonomer is not strictly prohibitive. As a
result, poly(dendrimer)s formation is plausible (path E) but
General procedure for the synthesis of long-trans-poly(dendrimer)s: A
mixture of the S-Gn or L-Gn dendrimers (1.0 equiv, 8.7 mm), the elongat-
ed trans-Pt linker 3 (1.0 equiv) in CHCl3/iPr2NH (v/v 1:1) was frozen in a
sealed tube under liquid N2 and degassed with N2 (3ꢂ). The mixture was
allowed to warm to 258C followed by the addition of CuI (0.5 equiv).
The mixture was then heated at 408C for 48 h. The solvent was concen-
trated in vacuo and the residue dissolved in minimum amount of CHCl3,
filtered through a short pad of alumina. A sample of the aliquot was then
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Synthesis of Organoplatinum Poly(dendrimer)s
FULL PAPER
taken out for GPC analysis. The residue compounds was purified by pre-
cipitation in MeOH to obtain the target poly(dendrimer)s.
(m, 28H; ArOCH2), 2.89–2.62 (m, 28H; ArCH2 + PhCH2), 2.34–1.92
(m, 52H; PCH2 + ArCH2CH2 + PhCH2CH2), 1.44–1.09 ppm (m, 36H;
PCH2CH3); 13C NMR (75 MHz, CDCl3): d=160.3, 153.2, 144.0, 143.9,
141.6, 138.3, 137.5, 131.3, 130.9, 128.6, 128.5, 128.2, 126.6, 126.3, 126.0,
long-trans-Pt-S-G1: Starting from S-G1 dendrimer (100 mg, 0.131 mmol),
Pt-linker
CHCl3/iPr2NH (v/v 1:1, 15 mL), the polymer (220 mg, 92%; 182 mg, 76%
after precipitation) was obtained as
yellow powder. 1H NMR
3 (148 mg, 0.131 mmol) and CuI (12.5 mg, 0.066 mmol) in
ꢀ
ꢀ
115.5, 109.2 (C CPt), 107.2, 106.8 (C CPt), 99.0, 67.6, 66.9, 32.5, 32.2,
32.0, 30.9, 30.7, 16.4 (quintet like, 1J
(C,P)=17.6 Hz; PCH2), 8.5 ppm;
31P NMR (122 MHz, CDCl3): d=11.1 ppm (1J
(Pt,P)=2370 Hz).
AHCTUNGTRENNUNG
a
AHCTUNGTRENNUNG
(300 MHz, CDCl3): d=7.58–7.16 (m, 26H; ArH + biphenyl-ArH), 6.88
(s, 4H; core-ArH), 6.67 (s, 4H; ArH), 6.54 (s, 2H; ArH), 5.12–4.86 (m,
12H; ArCH2O), 2.32–2.00 (m, 24H; PCH2), 1.36–1.10 ppm (m, 36H;
PCH2CH3); 13C NMR (75 MHz, CDCl3): d=160.3, 160.2, 153.2, 139.8,
137.6, 136.9, 133.4, 131.3, 131.1, 128.7, 128.1, 127.7, 127.5, 126.4, 115.9,
long-trans-Pt-L-G3: Starting from L-G3 dendrimer (154 mg,
0.037 mmol), Pt-linker 3 (41.9 mg, 0.037 mmol), CuI (3.5 mg, 0.019 mmol)
in CHCl3/iPr2NH (v/v 1:1, 4.2 mL), the product (191 mg, 99%; 160 mg,
83% after precipitation) was obtained as a yellow powder. 1H NMR
(300 MHz, CDCl3): d=7.53–7.12 (m, 82H; ArH + biphenyl-ArH), 7.07
ꢀ
ꢀ
109.4 (C CPt), 108.4 (C CPt), 106.4, 101.6, 70.7, 70.2, 16.5 (quintet like,
1J(C,P)=17.5 Hz; PCH2), 8.5 ppm; 31P NMR (122 MHz, CDCl3): d=
(major peak): 11.1 (1J(Pt,P)=2370 Hz); (minor peak): 14.9 ppm (1J-
(Pt,P)=2390 Hz).
G
(d, 3J
42H; ArH), 4.04–3.79 (m, 60H; ArOCH2), 2.95–2.61 (m, 60H; ArCH2 +
ACHTUNGTREN(NUNG H,H)=7.2 Hz, 4H; ArH), 6.82 (s, 4H; core-ArH), 6.47–6.25 (m,
E
U
PhCH2), 2.34–1.95 (m, 84H; PCH2 + ArCH2CH2 + PhCH2CH2), 1.41–
1.08 ppm (m, 36H; PCH2CH3); 13C NMR (75 MHz, CDCl3) (C CPt
ꢀ
long-trans-Pt-S-G2: Starting from S-G2 dendrimer (60.0 mg,
0.037 mmol), Pt-linker 3 (42.1 mg, 0.037 mmol), CuI (3.5 mg, 0.019 mmol)
in CHCl3/iPr2NH (v/v 1:1, 4.2 mL), the polymer (87 mg, 87%; 78 mg,
78% after precipitation) was obtained as a yellow powder. 1H NMR
(300 MHz, CDCl3): d=7.51–7.20 (m, 46H; ArH + biphenyl-ArH), 6.88
(s, 4H; core-ArH), 6.67 (s, 12H; ArH), 6.60–6.50 (m, 6H; ArH), 5.07–
4.88 (m, 28H; ArCH2O), 2.32–2.01 (m, 24H; PCH2), 1.36–1.09 ppm (m,
36H; PCH2CH3); 13C NMR (75 MHz, CDCl3): d=160.2, 160.1, 153.1,
139.8, 139.3, 137.6, 136.8, 133.3, 131.3, 131.1, 128.6, 128.1, 127.6, 126.6,
signal was too weak to be observed): d=160.31, 160.26, 153.2, 144.0,
143.94, 143.88, 141.6, 138.3, 137.5, 131.3, 130.9, 128.6, 128.5, 128.2, 126.3,
ꢀ
126.0, 115.4, 109.2 (C CPt), 107.2, 99.0, 67.6, 66.92, 66.85, 32.5, 32.2, 32.0,
30.9, 30.8, 30.7, 16.4 (quintet like, 1J
G
31P NMR (122 MHz, CDCl3): d=(major peak): 11.1 (1J
ACHTUNGTRENNUNG
(minor peaks): 14.9 (1J(Pt,P)=2390 Hz), 8.7 ppm (1J
G
ACHTUNGTRENNUNG
ꢀ
ꢀ
126.3, 115.8, 109.3 (C CPt), 108.4 (C CPt), 106.4, 101.6, 70.5, 70.1, 16.4
(quintet like, 1J(C,P)=17.7 Hz; PCH2), 8.4 ppm; 31P NMR (122 MHz,
CDCl3): d=(major peak): 11.2 (1J
(Pt,P)=2370 Hz); (minor peaks): 15.0
(1J(Pt,P)=2390 Hz), 8.7 ppm (1J
(Pt,P)=2320 Hz).
ACHTUNGTRENNUNG
Acknowledgements
AHCTUNGTRENNUNG
N
ACHTUNGTRENNUNG
We thank the Research Grants Council, Hong Kong SAR for the finan-
cial support (Project No: 400404).
long-trans-Pt-S-G3: Starting from S-G3 dendrimer (119 mg, 0.036 mmol),
Pt-linker 3 (40.8 mg, 0.036 mmol), CuI (3.4 mg, 0.018 mmol) in CHCl3/
iPr2NH (v/v 1:1, 4.1 mL), the product (115 mg, 73%; 79 mg, 50% after
precipitation) was obtained as a yellow powder. 1H NMR (300 MHz,
[1] G. R. Newkome, C. N. Moorefield, F. Vçgtle, Dendrimers and Den-
drons. Concepts, Syntheses, Applications, Wiley-VCH, Weinheim,
2001, pp. 539–562.
CDCl3): d=7.50–7.16 (m, 86H; ArH
+ biphenyl-ArH), 6.83 (s, 4H;
core-ArH), 6.66 (brs, 28H; ArH), 6.55 (brs, 14H; ArH), 5.06–4.79 (m,
60H; ArCH2O), 2.34–1.99 (m, 24H; PCH2), 1.35–1.08 ppm (m, 36H;
[2] For recent examples: a) S. J. Guillaudeu, M. E. Fox, Y. M. Haidar,
E. E. Dy, F. C. Szoka, J. M. J. Frꢀchet, Bioconjugate Chem. 2008, 19,
461–469; b) L. A. Connal, R. Vestberg, C. J. Hawker, G. G. Qiao,
Macromolecules 2007, 40, 7855–7863; c) C. Kojima, Y. Toi, A.
Harada, K. Kono, Bioconjugate Chem. 2007, 18, 663–670.
[3] For recent reviews: a) A. Zhang, L. Shu, Z. Bo, A. D. Schlꢃter, Mac-
romol. Chem. Phys. 2003, 204, 328–339; b) A. D. Schlꢃter, C. R.
Chim. 2003, 6, 843–851; c) A. D. Schlꢃter, Top. Curr. Chem. 2005,
245, 151–191; d) H. Frauenrath, Prog. Polym. Sci. 2005, 30, 325–384.
[4] For examples: a) R. N. Ganesh, J. Shraberg, P. G. Sheridan, S. Thayu-
manavan, Tetrahedron Lett. 2002, 43, 7217–7220; b) H.-F. Chow, C.-F.
Leung, W. Li, K.-W. Wong, L. Xi, Angew. Chem. 2003, 115, 5069–
5073; Angew. Chem. Int. Ed. 2003, 42, 4919–4923; c) S.-Y. Cheung,
H.-F. Chow, T. Ngai, X. Wei, Chem. Eur. J. 2009, 15, 2278–2288.
[5] H.-F. Chow, C.-F. Leung, L. Xi, L. W. M. Lau, Macromolecules 2004,
37, 3595–3605.
[6] a) N. V. Tsarevsky, B. S. Sumerlin, K. Matyjaszewski, Macromolecules
2005, 38, 3558–3561; b) B. A. Laurent, S. M. Grayson, J. Am. Chem.
Soc. 2006, 128, 4238–4239.
[7] K.-N. Lau, H.-F. Chow, M.-C. Chan, K.-W. Wong, Angew. Chem.
2008, 120, 7018–7022; Angew. Chem. Int. Ed. 2008, 47, 6912–6916.
[8] a) H.-B. Yang, N. Das, F. Huang, A. M. Hawkridge, D. C. Muddiman,
P. J. Stang, J. Am. Chem. Soc. 2006, 128, 10014–10015; b) H.-B. Yang,
A. M. Hawkridge, S. D. Huang, N. Das, S. D. Bunge, D. C. Muddiman,
P. J. Stang, J. Am. Chem. Soc. 2007, 129, 2120–2129.
13
ꢀ
PCH2CH3); C NMR (75 MHz, CDCl3) (C CPt signal was too weak to
be observed): d=160.2, 160.1, 153.1, 139.9, 139.3, 137.6, 136.8, 133.3,
ꢀ
131.3, 131.1, 128.7, 128.1, 127.7, 126.4, 115.8, 108.0 (C CPt), 106.4, 101.7,
70.6, 70.2, 70.1, 16.4 (quintet like, 1J
(C,P)=17.7 Hz; PCH2), 8.5 ppm;
31P NMR (122 MHz, CDCl3): d=(major peak): 11.1 (1J
(minor peaks): 14.9 (1J(Pt,P)=2390 Hz), 8.6 ppm (1J
(Pt,P)=2320 Hz).
long-trans-Pt-L-G1: Starting from L-G1 dendrimer (111 mg,
0.119 mmol), Pt-linker (134 mg, 0.119 mmol), CuI (11.3 mg,
ACHTUNGTREN(NGNU Pt,P)=2370 Hz);
A
ACHTUNGTRENNUNG
3
0.059 mmol) in CHCl3/iPr2NH (v/v 1:1, 13.6 mL), the product (229 mg,
97%; 174 mg, 74% after precipitation) was obtained as a yellow powder.
3
1H NMR (300 MHz, CDCl3): d=7.44 (d, J
(H,H)=7.5 Hz, 4H; biphenyl-
ArH), 7.38–7.12 (m, 18H; ArH + biphenyl-ArH), 7.05 (d, 3J
ACTHNUTRGNE(NUG H,H)=
8.1 Hz, 4H; ArH), 6.82 (s, 4H; core-ArH), 6.35 (s, 4H; ArH), 6.31–6.21
(m, 2H; ArH), 3.97–3.77 (m, 12H; ArOCH2), 2.85–2.57 (m, 12H;
ArCH2
+ PhCH2), 2.32–2.11 (m, 24H; PCH2), 2.11–1.91 (m, 12H;
ArCH2CH2
+
PhCH2CH2), 1.34–1.07 ppm (m, 36H; PCH2CH3);
13C NMR (75 MHz, CDCl3): d=160.31, 160.28, 153.3, 144.0, 141.7, 138.4,
137.6, 131.3, 131.0, 128.6, 128.5, 128.3, 126.6, 126.4, 126.0, 115.5, 109.2
ꢀ
ꢀ
(C CPt), 107.3, 106.8 (C CPt), 99.0, 67.6, 66.9, 32.6, 32.3, 32.1, 31.0, 30.9,
16.4 (quintet like, 1J(C,P)=17.5 Hz; PCH2), 8.5 ppm; 31P NMR
(122 MHz, CDCl3): d=11.1 ppm (1J
(Pt,P)=2370 Hz).
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
long-trans-Pt-L-G2: Starting from L-G2 dendrimer (131 mg,
0.066 mmol), Pt-linker 3 (74.2 mg, 0.066 mmol), CuI (6.2 mg, 0.033 mmol)
in CHCl3/iPr2NH (v/v 1:1, 7.5 mL), the product (175 mg, 87%; 174 mg,
86% after precipitation) was obtained as a yellow powder. 1H NMR
[9] M. Ferrer, M. Mounir, O. Rossell, E. Ruiz, M. A. Maestro, Inorg.
Chem. 2003, 42, 5890–5899.
(300 MHz, CDCl3): d=7.45 (d, 3J
7.39–7.12 (m, 38H; ArH + biphenyl-ArH), 7.06 (d, 3J
4H; ArH), 6.82 (s, 4H; core-ArH), 6.45–6.24 (m, 18H; ArH), 4.02–3.82
ACHTUNGTRENNUNG
G
Received: April 3, 2009
Published online: July 27, 2009
Chem. Eur. J. 2009, 15, 8874 – 8879
ꢁ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
8879