An "attachment through coordination" approach to side chain dendritic polymers

Article abstract of DOI:10.1002/ejoc.200500370

This paper reports the synthesis of side chain dendritic polymers by a newly developed "attachment through coordination" methodology. Initially, aromatic/aliphatic polyethers bearing two uncomplexed terpyridine (tpy) groups per repeating unit are prepared, and dendritic fragments corefunctionalized with tpy-Ru^IIICl₃ moieties are afterwards attached onto these free tpy side groups. The two second-generation alkoxy-decorated side dendrons employed here provided solubility in the final polymeric system and potential for the development of ordered structures. Selective complexation between terpyridines and ruthenium ions proved to be an efficient tool for the complete coverage of all initial polymeric-tpy groups. Perfectly substituted dendronized polymers carrying two (dendritic)tpy-Ru ^II-tpy side moieties per repeating unit were thus synthesized, as demonstrated by their ¹H NMR characterization. A polymerizable macromonomer diol already carrying the side (dendritic)tpy-Ru^II-tpy moieties was synthesized at the same time, enabling subsequent polymerization through the "macromonomer" growth approach. Wiley-VCH Verlag GmbH & Co. KGaA, 2005.

Full text of DOI:10.1002/ejoc.200500370

FULL PAPER
An “Attachment Through Coordination” Approach to Side Chain
Dendritic Polymers
Aikaterini K. Andreopoulou[a] and Joannis K. Kallitsis*[a]
Keywords: Dendronized polymers / N-ligands / Ruthenium / Terpyridines
This paper reports the synthesis of side chain dendritic poly-
mers by a newly developed “attachment through coordina-
tion” methodology. Initially, aromatic/aliphatic polyethers
bearing two uncomplexed terpyridine (tpy) groups per re-
peating unit are prepared, and dendritic fragments core-
functionalized with tpy-RuIIICl3 moieties are afterwards at-
tached onto these free tpy side groups. The two second-gen-
eration alkoxy-decorated side dendrons employed here pro-
vided solubility in the final polymeric system and potential
for the development of ordered structures. Selective com-
plexation between terpyridines and ruthenium ions proved
to be an efficient tool for the complete coverage of all initial
polymeric-tpy groups. Perfectly substituted dendronized
polymers carrying two (dendritic)tpy-RuII-tpy side moieties
per repeating unit were thus synthesized, as demonstrated
by their 1H NMR characterization. A polymerizable macro-
monomer diol already carrying the side (dendritic)tpy-RuII-
tpy moieties was synthesized at the same time, enabling sub-
sequent polymerization through the “macromonomer”
growth approach.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2005)
literature up until now. For the preparation of dendronized
polymers the well established “macromonomer” growth ap-
proach[4] requires the preparation of polymerizable macro-
monomers carrying the side dendrons prior to polymeriza-
tion. On the other hand, the “divergent” or “attach to”
methodology for SCDPs[4] proceeds either through con-
struction of the side dendrons at appropriate side function-
alities of the main polymeric chains or by attachment of
prefabricated dendrons onto preexisting polymeric main
chains. To extend these methodologies for the fabrication
of SCDPs in which the side dendrons were held on the main
polymeric backbones through metal to ligand coordination
bonding, one would have either to prepare macromonomers
carrying the side dendritic wedges connected through me-
tal-ligand bonds or to attach the desired dendrons onto
functional main polymeric chains by employing such coor-
dination connectivity.
The latter pathway, an “attachment through coordina-
tion” approach, has been employed in this contribution.
More particularly, dendronized aromatic/aliphatic poly-
ethers, in which two side-dendritic moieties are held onto
each main polymeric repeating unit through terpyridine-
RuII-terpyridine (tpy-RuII-tpy) connecting points, have been
developed. Through this “attachment through coordina-
tion” methodology, we were able to fulfil the prerequisite
for dendronized polymers: that is, perfectly substituted
polymers bearing side dendrons at every single repeating
unit. At their peripheries the side dendrons used in this
study bear alkoxy groups that have in the past offered the
potential for the preparation of dendronized polymers
forming ordered layered structures.[5] The defined distance
Introduction
The syntheses and characterization of dendrons, dendri-
mers and side chain dendritic polymers (SCDPs) has been
the target of intense scientific research over the past decades
and has now reached a point where it is aiming in even
more complicated directions, such as the development of
supramolecular, self-assembling structures. Many such
molecules, polymeric or monomeric, elegantly organized
into multicomponent structures through various interac-
tions, are the newest trend in the general field of dendri-
mers, and so efforts are currently being devoted towards the
combination of different inter- or intramolecular forces that
may give rise to well formed, well defined materials pos-
sessing controllable properties arising from, or depending
on, the final material’s organizational patterns.[1] One fasci-
nating approach for the fabrication of such architectural
systems is the employment of metal to ligand bonding be-
tween different molecular entities or parts of the same
molecule.[2] This kind of connectivity offers the opportunity
to incorporate a large number of metals, each one providing
its own unique properties (e.g., optical, electrochemical,
catalytic and so on) to the final dendritic system.[3]
As far as SCDPs are concerned, the concept of side den-
dritic moieties attached in regular fashion onto linear poly-
meric main chain backbones through metal to ligand bond-
ing has not, to the best of our knowledge, appeared in the
[a] Department of Chemistry, University of Patras,
26500 Patras, Greece
Fax: +30-2610-997-122
E-mail: J.Kallitsis@chemistry.upatras.gr
4448
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI: 10.1002/ejoc.200500370
Eur. J. Org. Chem. 2005, 4448–4458

An “Attachment Through Coordination” Approach to Side Chain Dendritic Polymers
FULL PAPER
of the two RuII ions attached on the same monomeric unit, tected terphenyl diol with two tpy side groups in its middle
the distances along the polymeric main chain determined phenylene ring. Removal of the THP groups was performed
by the spacer length, and finally the interchain distances by treatment with camphorsulfonic acid, while its complex-
dictated by the generation and the type of substitution of ation with the tpy units was reversed by stirring the crude
the alkoxy-decorated dendrons should result in regular po- material in aqueous Na2CO3 solution. The desired ter-
sitioning of the RuII ions with distances on nanometer phenyl diol 5 was obtained in gram scale quantities and was
1
scales (2–4 nm).
fully characterized by H and 13C NMR spectroscopy (see
In addition to the dendronized polymeric complexes de- inset in Figure 1).
scribed above, a macromonomer already bearing the side
Afterwards, diol 5 was polymerized with aliphatic dibro-
(dendritic)tpy-RuII-tpy moieties has also been synthesized, mides containing 11 or 12 methylene units under phase-
showing that such dendronized systems may also be pre- transfer polymerization conditions[10] (Scheme 2). It is
pared by the “macromonomer” route. All the initial mono- worth mentioning that the resulting aromatic-aliphatic
mers and polymers, as well as the final dendronized poly- polyethers are readily soluble in common chlorinated sol-
meric complexes and the macromonomer dendronized com- vents such as CHCl3, o-DCB, and TCE, unlike the initial
plex, have been characterized and their structural perfection diol 5, which was only slightly soluble in o-DCB, forcing us
has been demonstrated by NMR spectroscopy and UV/Vis to perform the polymerizations over long periods of time to
experiments.
ensure complete monomer consumption. Polyethers PETH-
1
x=11 and PETH-x=12 were fully characterized by H and
13C NMR techniques (Figure 1), while their molecular
characteristics were evaluated by GPC vs. PS standards
Results and Discussion
In order to accomplish this “attachment through coordi- with CHCl3 as eluent (Table 1). It is reasonable to assume
nation” strategy for the preparation of side chain dendritic that their true molecular weights differ from those esti-
polymers we first had to synthesize the desired main chain mated by GPC not only because of the semi-rigid nature
polymeric backbones. These had to bear side functionali- of the polymeric backbones but also because of possible
ties, in particular terpyridine (tpy) moieties, onto which the interactions between the free tpy ligands and the chromato-
side dendritic fragments would later on be attached through graphic stationary phase. In cases in which low molecular
metal to ligand bonding. For that reason we designed and weight materials were obtained (e.g., PETH-x=12(iii); see
synthesized aromatic/aliphatic polyethers with two side tpy Table 1), the true number average molecular weight was cal-
groups per repeating unit, as depicted in Schemes 1 and 2. culated from the 1H NMR spectrum by the end-group
The aromatic dibromide 3 was prepared by etherification analysis technique. More particularly, peaks corresponding
of 4Ј-(p-hydroxyphenyl)-2,2Ј:6Ј,2ЈЈ-terpyridine (OH-Ph-tpy; to aromatic protons of the diol could be found at δ = 7.1,
1)[6] with 1,4-dibromo-2,5-bis(bromomethyl)benzene (2)[7] and these, together with the tpy proton peaks at δ = 8.7,
(Scheme 1). Palladium mediated-cross coupling[8] of 3 with gave the actual degree of polymerization of the PETH-
the THP-protected (THP
=
tetrahydropyranyl) hy- x=12(iii) sample [DPn = 3 Mn(NMR) = 3280]. Compari-
droxyphenyl boronic acid 4[9] produced the THP-end-pro- son of the DPn obtained from the NMR end-group analysis
Scheme 1. Synthesis of monomer diol 5.
Eur. J. Org. Chem. 2005, 4448–4458
www.eurjoc.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4449

A. K. Andreopoulou, J. K. Kallitsis
FULL PAPER
Scheme 2. Synthesis of polymers PETH-x=11 and PETH-x=12.
1
Figure 1. H NMR of PETH-x=12(i) in CDCl3 and of diol 5 in [D6]DMSO (see inset).
4450
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2005, 4448–4458

An “Attachment Through Coordination” Approach to Side Chain Dendritic Polymers
FULL PAPER
Table 1. Molecular weight characteristics of the initial polyethers for PETH-x=12(iii) with that provided by GPC demon-
PETH-x=11 and PETH-x=12.[a]
strates an underestimation of the true molecular character-
istics of the synthesized polymers.
Polymer
Mn
Mw
Mw/Mn
1
Additionally, as can be seen in the H NMR spectrum
of PETH-x=12(i) (Figure 1), no end groups at δ = 6.8 or
7.1 – corresponding to the aromatic protons of the initial
diol 5 adjacent to the hydroxy functionalities – are evident
in the case of the higher molecular weight materials, so we
can conclude that those are indeed high molecular weight
polymeric materials.
PETH-x=11(i)
PETH-x=11(ii)
PETH-x=12(i)
PETH-x=12(ii)
PETH-x=12(iii)[b]
8800
2520
7160
9710
1070
21900
4110
13030
26130
1680
2.5
1.6
1.8
2.7
1.6
[a] By size exclusion chromatography (GPC) with CHCl3 as eluent,
at room temperature, vs. PS standards. [b] For PETH-x=12(iii) the
Mn was calculated from its 1H NMR spectrum by end-group analy-
ses and was found to be equal to 3280, DPn = 3.
For the preparation of the tpy core-functionalized side
dendritic wedges we etherified the dendritic benzyl bromide
1
Figure 2. H NMR of uncomplexed G2-tpy dendron in CDCl3.
Scheme 3. Synthesis of G2-tpyRuIIICl3 dendron 7.
Eur. J. Org. Chem. 2005, 4448–4458
www.eurjoc.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4451

A. K. Andreopoulou, J. K. Kallitsis
FULL PAPER
6
[11] with OH-Ph-tpy 1 (Scheme 3, Figure 2). The particular
Having prepared the main polymeric backbones and the
alkoxy-decorated second-generation dendron 6 was em- ruthenium-functionalized side-dendrons we were able to
ployed in order to confer solubility to the final metal-con- proceed to their complexation, to afford the final dendron-
taining polymeric systems and, more importantly, for future ized ruthenium loaded polymers. As shown in Scheme 4,
correlations with some analogous dendronized polyethers polyethers PETH-x=11(i) and PETH-x=12(i) were
that had been found to present interesting self-organiza- treated with the monocomplexed dendron 7 under reductive
tional solid-state patterns.[5] The paramagnetic G2-tpyRuII- conditions in the presence of catalytic amounts of N-ethyl-
ICl3 dendron 7 was synthesized by heating of the uncom- morpholine in CHCl3/EtOH solutions. In order to ensure
plexed dendron 6 at reflux with RuCl3·xH2O in THF/EtOH complete coverage of all free polymeric tpy units with the
solution, and was used without further purification.
side dendrons, excesses of dendron 7 and long reaction
Scheme 4. Synthesis of dendronized polymeric complexes Ia and Ib.
4452
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2005, 4448–4458

An “Attachment Through Coordination” Approach to Side Chain Dendritic Polymers
FULL PAPER
times were employed. The final dendronized polymeric ma-
These dendronized highly Ru-loaded polymers are solu-
terials Ia and Ib, respectively, were precipitated from the ble in common organic solvents such as CHCl3, THF, and
reaction mixture after counterion exchange with addition DMSO, allowing their characterization by 1H and 13C
of excess of methanolic NH4PF6 solution.[12] The red poly- NMR techniques. A typical 1H NMR spectrum, for the
meric powders were collected and thoroughly washed with dendronized polymeric complex Ib, is presented in Figure 3.
diethyl ether for the selective removal of the excess side den- The spectrum of Ib possesses all the characteristic peaks
dritic monocomplex employed. We were thus able to obtain corresponding to the aromatic protons of tpyRuIItpy pro-
pure, perfectly dendronized aromatic-aliphatic polyethers tons: both those arising from the main polymeric backbone
bearing two side (dendritic)tpy-RuII-tpy moieties on every and those arising from the side dendritic fragments. On
1
single polymeric unit (Ia and Ib).
comparison of the H NMR spectra of the uncomplexed
1
Figure 3. H NMR of dendronized polymeric complex Ib in [D6]DMSO.
Eur. J. Org. Chem. 2005, 4448–4458
www.eurjoc.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4453

A. K. Andreopoulou, J. K. Kallitsis
FULL PAPER
polyether PETH-x=12(i) (Figure 1) and of the respective
dendronized polymeric complex Ib (Figure 3) one can ob-
serve the expected downfield shift of the 3Ј and 3 tpy pro-
tons after complexation – from δ = ca. 8.6 to 9 and 9.35,
respectively – and the upfield shift of the 6 tpy protons,
from δ = ca. 8.6 to ca. 7.3. Moreover, no differentiation
between the dendritic tpy protons and the tpy protons of
the main polymeric chain was seen, due to the similarity of
their neighboring environment.
Additionally, and most importantly, no peaks corre-
sponding to uncomplexed, free tpy units along the poly-
meric main chains, at δ = 8.6–8.71, were detected. This can
be clearly seen in the inset of Figure 3, where the region
from δ = 9.6 to 7.8 is enlarged. We can thus safely draw
the conclusion that this “attachment through coordination”
methodology employed for the preparation of side dendritic
polymers had proved efficient, producing perfectly substi-
tuted polymers with two side dendrons on every single re-
peating unit and, moreover, held onto the polymeric main
backbones through metal to ligand (tpy-RuII-tpy) bonding.
Unfortunately, the dendronized polymeric complexes Ia and
Figure 4. Concentration-dependence measurements of the reduced
viscosities of PETH-x=11(i) in CHCl3 and of Ia in DMSO, at
30°C.
Ib could not be characterized by GPC. Similar problems macromonomer carrying the desired dendritic fragments
have also been reported in the literature and have been as- prior to polymerization. The initial diol 5 was thus treated
signed to the strong interaction of ruthenium with the sta- with excess G2-tpyRuIIICl3 monocomplex 7 in THF/EtOH
tionary phase used in the GPC columns.[13]
solution containing a catalytic amount of N-ethylmorph-
On the other hand, viscosity measurements were per- oline (Scheme 5). The dendronized macromonomer dicom-
formed for a dendronized polymeric complex and its un- plex was precipitated from the reaction mixture after coun-
complexed polymeric precursor. Figure 4 shows the vis- terion exchange with addition of excess methanolic
cosity values obtained for polymeric complex Ia in com- NH4PF6 solution. All excess of G2-dendritic monocomplex
parison with its precursor PETH-x=11(i). Polyether was selectively removed by washing with diethyl ether. This
PETH-x=11(i) showed typical polymeric behavior with an macromonomer dicomplex II also showed improved solu-
intrinsic viscosity [n] = 0.13 in CHCl3 at 30°C. In the case bilities relative to the initial diol 5, being soluble in CHCl3,
1
of the polymeric complex Ia the viscosity measurements THF, DMSO, etc. The H NMR spectrum of the second-
were performed in DMSO, also at 30°C. An increase in the generation macromonomer dicomplex II is presented in
reduced viscosity is evident as the concentration decreases. Figure 5, with an assignment of all peaks. Also in this case,
Such behavior has been reported for various coordination no peaks corresponding to free tpy units were detected in
polymers containing tpy-RuII-tpy groups and can be ex- the δ = 9.5 to 7.8 region. Moreover, the 1H NMR spectrum
plained in terms of the polyelectrolytic nature of the poly- of the dicomplex II is in perfect agreement with its counter-
mers due to the presence of the RuII and their counteri- part for the dendronized polymeric complex Ib presented in
ons.[14] Attempts to reduce the polyelectrolyte repulsion and Figure 3, providing additional evidence for the structural
obtain true viscosity values by means of intrinsic viscosity perfection of the dendronized polyether prepared through
were also made, by addition of NH4PF6 to the DMSO solu- the “attachment through coordination” approach. This
tions, but even a 10 mm salt concentration caused the poly- macromonomer dicomplex should also give us the opportu-
meric complex to precipitate from the solution. In any case, nity to prepare the whole series of dendronized polymers
these observations alone demonstrate the different nature with other generation side dendrons and two RuII ions on
of the dendronized polymeric complexes with respect to the every repeating polymeric unit.
uncomplexed polyether precursors. Unfortunately, CHCl3
Examination of the prepared materials’ optical proper-
could not be used as solvent for Ia. Actually the polymeric ties was performed with the aid of UV/Vis absorption mea-
complexes, even though macroscopically soluble in CHCl3, surements in dilute CHCl3 solutions (Figure 6). Since the
gave irreproducible viscosity values, probably owing to the uncomplexed diol 5 was insoluble in CHCl3 we prepared
formation of aggregates. As an example, a 0.23 gdL–1 solu- the corresponding didodecyloxy-end-functionalized un-
tion of the dendronized complex Ia in CHCl3 gave an nred complexed monomer (model compound M; see Experimen-
= 0.08 dLg–1 at 30°C, while the same polymeric complex in tal) in order to compare its absorption spectra safely with
DMSO at C = 0.23 gdL–1 gave an nred = 0.53 dLg–1.
those of the other materials in the same solvent. For the
Recognizing that the well established “macromonomer” uncomplexed samples, PETH-x=12 and model compound
route towards dendronized polymers can guarantee the M, characteristic bands attributable to the free tpy groups
structural perfection of the final polymers in all cases, we can be found at 284 nm. After the formation of the tpy-
decided to take a first step towards it and to prepare a RuII-tpy complexes, materials Ib and II, another intense
4454
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2005, 4448–4458

An “Attachment Through Coordination” Approach to Side Chain Dendritic Polymers
FULL PAPER
Scheme 5. Synthesis of dendronized macromonomer II.
peak can be observed at 310 nm, originating from the li-
Conclusions
gand-centered (LC) π–π* transition of the tpy ligand. In
addition, the characteristic band of tpy-RuII-tpy complexes,
In conclusion we were able to prepare second-generation
arising from the d–π* metal to ligand charge transfer alkoxy-functionalized SCDPs by a newly developed “at-
(MLCT) transitions, is now obvious at 496 nm. Moreover tachment through coordination” approach. The coordina-
the monocomplexed G2-tpyRuIIICl3 dendron 7 presents a tion chemistry of the tpy-RuII-tpy complexes has been used
band at ca. 420 nm, as would be expected for a tpy-RuIII for the attachment of alkoxy(G2)-tpy-functionalized den-
monocomplex.
drons onto polymeric backbones bearing two tpy side
Eur. J. Org. Chem. 2005, 4448–4458
www.eurjoc.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4455

A. K. Andreopoulou, J. K. Kallitsis
FULL PAPER
1
Figure 5. H NMR of macromonomer dicomplex II in [D6]DMSO.
groups per repeating unit. In addition, a macromonomer the influence of the polymeric architectures on their final
diol already carrying the side dendrons was synthesized, properties further.
opening the pathway for the development of such dendron-
ized polymers through the “macromonomer” route. Evi-
dence for the dicomplexes’ structural perfection came from Experimental Section
their NMR characterization. Their UV/Vis absorption
Materials: Second-generation dendron 6,[11] 4Ј-(p-hydroxyphenyl)-
spectra are also in accordance with the incorporation of the
2,2Ј:6Ј,2ЈЈ-terpyridine (1),[6] 1,4-dibromo-2,5-bisbromomethyl ben-
tpy-RuII-tpy moieties. The developed methodology should
give us the ability to arrange the Ru centers nicely in well
defined, predictable positions along the polymeric chains
zene (2),[7] and catalyst PdCl2(dppf)[15] were prepared by literature
procedures. The synthesis of 2-tetrahydropyranyloxy-4-phenylbo-
ronic acid (4) was described in a previous publication.[9] Tetra-
and finally in the whole polymeric matrix and to explore hydrofuran (THF) was distilled from sodium prior to use. Reagents
4456 © 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim www.eurjoc.org
Eur. J. Org. Chem. 2005, 4448–4458

An “Attachment Through Coordination” Approach to Side Chain Dendritic Polymers
FULL PAPER
134.20, 137.21, 141.12, 149.51, 150.15, 156.24, 156.82, 157.12,
160.00 ppm.
Camphorsulfonic acid (CSA; 6.31 g, 27.17 mmol) was added to a
solution of THP-protected diol (2.00 g, 1.81 mmol) in DMA
(100 mL) and THF (100 mL) and the mixture was stirred at room
temperature for 48 h. THF was then removed under reduced pres-
sure, Na2CO3 (2 m, 120 mL) was then added, and the mixture was
stirred for another 48 h. Filtration, washing with H2O, MeOH,
CHCl3, and n-hexane, and drying under vacuum afforded the final
1
monomeric diol 5 as a white solid. Yield 1.64 g (96.7%). H NMR
(400 MHz, 80°C [D6]DMSO, TMS): δ = 5.1 (s, 4 H), 6.83 (d, 4 H),
7.1 (d, 4 H), 7.3 (d, 4 H), 7.5 (t, 4 H), 7.53 (s, 2 H), 7.85 (d, 4 H),
8.01 (t, 4 H), 8.63–8.65 (s, 4H and d, 4 H), 8.74 (d, 4 H) ppm.
13C NMR (100 MHz, 80°C, [D6]DMSO, TMS): δ = 68.15, 115.69,
116.01, 117.76, 121.38, 124.93, 128.69, 130.27, 130.40, 130.58,
131.65, 133.93, 137.93, 140.83, 149.40, 149.74, 155.46, 156.02,
157.37, 159.82 ppm. C62H44N6O4 (936): calcd. C 79.49, H 4.7, N
8.97; found C 79.61, H 5.09, N 8.6.
Figure 6. UV/Vis absorption spectra in CHCl3 (Ϸ 10–5 m). All spec-
tra were normalized to the 284 nm peak of dicomplex II.
Uncomplexed G2-Dendron-tpy: A mixture of 1 (0.50 g, 1.54 mmol),
G2-dendron 6 (1.90 g, 1.70 mmol), K2CO3 (0.43 g, 3.08 mmol), and
18-crown-6 (0.04 g, 0.15 mmol) in acetone (60 mL) was heated at
reflux for 48 h. Filtration and rotary evaporation of the organic
solvent afforded the crude product, which was stirred with MeOH
for several hours. Drying under vacuum at 40°C gave the final
and solvents of analytical grade purity were purchased from Ald-
rich or Merck and were used without further purification unless
otherwise noted. Aliphatic dibromide x = 12 was recrystallized
from methanol. All reactions were performed under argon. Degas-
sing of reaction mixtures was performed by subsequent cycles of
evacuation and filling with argon (three times).
1
product as a viscous oil. Yield 2.01 g (96%). H NMR (400 MHz,
25°C, CDCl3, TMS): δ = 0.86 (t, 12 H), 1.25–1.43 (two m, 72 H),
1.76 (m, 8 H), 3.93 (t, 8 H), 4.97 (s, 4 H), 5.07 (s, 2 H), 6.4 (d, 2
H), 6.56 (m, 3 H), 6.7 (d, 2 H), 7.08 (d, 2 H), 7.35 (t, 2 H), 7.86–
7.88 (m, 4 H), 8.66 (d, 2 H), 8.71–8.75 (m, 4 H) ppm. 13C NMR
(100 MHz, 25°C, CDCl3, TMS): δ = 14.32, 22.97, 26.40, 29.64–
29.93, 32.23, 68.56, 70.60, 70.70, 101.49, 102.32, 106.26, 106.88,
115.77, 118.73, 121.70, 123.99, 128.87, 131.25, 137.09, 139.41,
149.44, 152.30, 156.30, 156.89, 160.08, 160.68, 160.98 ppm.
Instrumentation: 1H and 13C NMR spectra were obtained on a
Bruker Avance DPX (400 MHz and 100 MHz, respectively) spec-
trometer in CDCl3 or [D6]DMSO and with TMS as internal stan-
dard. Gel permeation chromatography (GPC) measurements for
polyethers PETH-x=11 and PETH-x=12 were carried out with a
Polymer Lab chromatograph with two Ultra Styragel linear col-
umns with pore sizes of 104 and 500 Å, respectively, UV detector
(254 nm), polystyrene standards, and CHCl3 as eluent, at 25°C
with a flow rate of 1 mLmin–1. Viscosity measurements of poly-
mers PETH-x=11(i) and Ia were conducted in CHCl3 or DMSO
with Ubbelohde- or Ostwald-type viscometers, respectively, at 30°C
in a Scott Gerate AVS. 310. The UV spectra were recorded on a
Hewlett Packard 8452A Diode Array UV/Visible spectrophotome-
ter, in dilute CHCl3 (Ϸ 10–5 m) solutions.
Monocomplex 7: A solution of uncomplexed G2-dendron-tpy
(0.5233 g, 0.3840 mmol), RuCl3·xH2O (0.0836 g, 0.4031 mmol),
THF (5 mL), and EtOH (15 mL) was heated at reflux for 24 h.
After cooling to room temperature the solvent was reduced to al-
most half its volume and the resulting mixture was filtered, washed
with EtOH and cold acetone, and dried under vacuum, affording
monocomplex 7 as a brown powder, which was used without fur-
ther purification. Yield 0.47 g (78.3%).
Dibromide 3: A mixture of 1 (2.445 g, 7.523 mmol), 2 (1.270 g,
3.010 mmol), K2CO3 (8.306 g, 0.060 mol), and 18-crown-6 (0.159 g,
0.602 mmol) in CH3CN (120 mL) was heated at reflux for 48 h.
The solvent was evaporated under reduced pressure and the mix-
ture was dispersed in H2O, stirred, and filtered. Washing with H2O,
EtOH, and n-hexane afforded the desired monomer 3 as a yellowish
powder, which was used without further purification. Yield 2.60 g
(95%).
General Polymerization Procedure: A carefully degassed mixture of
diol 5 (0.200 g, 0.210 mmol), α,ω-aliphatic dibromide (x = 11,
0.066 g, 0.210 mmol; x = 12: 0.070 g, 0.210 mmol), TBAH (0.029 g,
0.085 mmol), o-DCB (2 mL), and NaOH (10 n, 1 mL) was vigor-
ously stirred at 120°C under a continuous stream of argon for 5
days. The resulting mixture was diluted with CHCl3 and precipi-
tated from a tenfold amount of MeOH, filtered, redisolved in
CHCl3, filtered once more in order to remove any traces of salt,
and precipitated in MeOH or film-cast to produce the final poly-
meric material in powder or film form. Elemental analyses for
Diol 5: A degassed mixture of 3 (2.60 g, 2.86 mmol), 4 (2.54 g,
11.44 mmol), PdCl2(dppf) (0.10 g, 0.14 mmol), THF (200 mL) and
NaOH (3 m, 11.43 mL, 34.28 mmol) was heated under reflux with
vigorous stirring for 96 h. Most of the organic solvent was after-
wards removed under reduced pressure, MeOH was then added
and, after filtration and washing with MeOH, H2O, and n-hexane,
the THP-end-protected diol was obtained as a grayish powder.
PETH-x=12(i): C74H66O4N6 (1102): calcd. C 80.58, H 5.99, N
7.62; found C 80.78, H 5.77, N 7.25.
PETH-x=11(i): C73H64N6O4 (1088): calcd. C 80.51, H 5.88, N
7.72; found C 80.74, H 5.85, N 7.31.
PETH-x=12(i): 1H NMR (400 MHz, 25°C, CDCl3, TMS): δ =
1
Yield 2.00 g (63.5%). H NMR (400 MHz, CDCl3, 25°C, TMS): δ
= 1.5–2 (three m, 12 H), 3.63 (m, 2 H), 3.95 (m, 2 H), 5.08 (s, 4
H), 5.47 (t, 2 H), 7.02 (d, 4 H), 7.12 (d, 4 H), 7.33 (t, 4 H), 7.4 (d, 1.26 (broad, 12 H), 1.43 (m, 4 H), 1.77 (m, 4 H), 3.97 (t, 4 H), 5.05
4 H), 7.64 (s, 2 H), 7.83–7.89 (d, 4H and m, 4 H), 8.66 (d, 4 H),
(m, 4 H), 6.93–7 (two d, 8 H), 7.31 (m, 4 H), 7.38 (d, 4 H), 7.63
8.7 (s, 4 H), 8.73 (d, 4 H) ppm. 13C NMR (100 MHz, 25°C, CDCl3,
(s, 2 H), 7.8–7.85 (m, 8 H), 8.6–8.71 (m, 12 H) ppm. 13C NMR
TMS): δ = 19.22, 25.60, 30.78, 62.57, 68.48, 96.82, 115.70, 116.74, (100 MHz, 25°C, CDCl3, TMS): δ = 26.02, 29.31–29.55, 68.11,
118.73, 121.74, 124.12, 128.90, 130.72, 131.39, 131.67, 133.51, 68.30, 114.43, 115.29, 118.29, 121.32, 123.69, 128.48, 130.33,
Eur. J. Org. Chem. 2005, 4448–4458
www.eurjoc.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4457

A. K. Andreopoulou, J. K. Kallitsis
FULL PAPER
131.00, 131.31, 132.01, 133.79, 136.76, 140.73, 149.07, 149.73,
155.82, 156.38, 158.75, 159.52 ppm.
132.48, 132.51, 137.03, 141.2, 149.44, 150.16, 156.27, 156.89,
159.18, 159.97 ppm.
Dendronized Polymeric Complexes Ia and Ib: A solution of poly-
meric material [PETH-x=11(i): 0.0200 g, 0.0184 mmol, or PETH-
Acknowledgments
x=12(i): 0.0200 g, 0.0181 mmol], monocomplex
7 (0.1155 g,
The authors are indebted to Profs. D. Papaioannou and G. Bokias
(University of Patras) for helpful discussions and Mr. D. Vachliotis
for his efforts during the NMR measurements. This work was par-
tially supported by the Operational Program for Education and
Initial Vocational Training on “Polymer Science and Technology”
3.2a, 33H6, administered through the Ministry of Education in
Greece.
0.0735 mmol or 0.1140 g, 0.0726 mmol, respectively), CHCl3
(8 mL), EtOH (3 mL), and N-ethylmorpholine (10 drops) was
heated at reflux for 5 days. The resulting deep red solution was
filtered through celite and the desired polymeric complex Ia or Ib
was obtained after precipitation with addition of excess saturated
NH4PF6/MeOH solution, filtration, and washing with EtOH, H2O,
and diethyl ether. Yield 0.0420 g for Ia and 0.0376 g for Ib (50%
and 45%, respectively). Dendronized polymeric complex Ia: 1H
NMR (400 MHz, 80°C, [D6]DMSO, TMS): δ = 0.84 (t, 24 H), 1.25
(broad, 158 H), 1.69 (m, 20 H), 3.96 (m, 20 H), 5.05 (s, 8 H), 5.25
(m, 8 H), 6.41 (s, 4 H), 6.58 (s, 10 H), 6.79 (s, 4 H), 7.1 (b, 4 H),
7.27–7.5 (broad, 28 H), 7.7 (s, 2 H), 8.02 (m, 8 H), 8.37 (m, 8 H),
9.03 (m, 8 H), 9.34 (s, 8 H) ppm. 13C NMR (100 MHz, 80°C, [D6]
DMSO, TMS): δ = 13.62, 21.96, 25.36, 28.59–28.9, 31.17, 67.26,
69.05, 100.01, 101.00, 105.52, 106.62, 114.28, 115.30, 120.14,
124.54, 127.52, 129.02, 130.09, 131.84, 137.76, 138.97, 146.50,
152.10, 154.8, 157.99, 159.37, 159.74, 160.02 ppm.
[1] a) G. R. Newkome, C. N. Moorefield, F. Vögtle, Dendrimers
and Dendrons: Concepts, Syntheses, Applications, Wiley-VCH,
New York, 2001; b) Dendrimers and other Dendritic Polymers
(Eds: J. M. J. Fréchet, D. A. Tomalia) Wiley-VCH, New York,
2001; c) J. M. J. Fréchet, S. Hecht, Angew. Chem. 2001, 113,
76–94; Angew. Chem. Int. Ed. 2001, 40, 74–91; d) V. Percec, M.
Glodde, T. K. Bera, Y. Miura, I. Shiyanovskaya, K. D. Singer,
V. S. K. Balagurusamy, P. A. Heiney, I. Schnell, A. Rapp, H.-
W. Spiess, S. D. Hudson, H. Duan, Nature 2002, 419, 384–387.
[2] a) J. M. Lehn, Supramolecular Chemistry, VCH, Weinheim,
1995; b) U. S. Schubert, C. Eschbaumer, Angew. Chem. 2002,
114, 3016–3050; Angew. Chem. Int. Ed. 2002, 41, 2892–2926.
[3] a) G. R. Newkome, E. He, C. N. Moorefield, Chem. Rev. 1999,
99, 1689–1746; b) G. R. Newkome, E. He, L. A. Gordinez,
Macromolecules 1998, 31, 4382–4386; c) E. C. Constable,
Chem. Commun. 1997, 1073–1080; d) J. D. Diaz, D. G. Storrier,
S. Bernhard, K. Takada, H. D. Abruña, Langmuir 1999, 15,
7351–7354; e) A. El-ghayoury, H. Hofmeier, A. P. H. J.
Schenning, U. S. Schubert, Tetrahedron Lett. 2004, 45, 261–
264.
Dicomplex II: A mixture of diol 5 (20.0 mg), monocomplex 7
(100.7 mg), THF (15 mL), EtOH (5 mL), and N-ethylmorpholine
(5 drops) was heated at reflux for 48 h. After cooling to room tem-
perature the deep red solution was filtered from celite and the sol-
vent was reduced to almost half its volume. Addition of excess satu-
rated NH4PF6/MeOH solution caused the complex to precipitate
as a red powder, which was filtered and washed with EtOH, H2O,
n-hexane, and cold diethyl ether. Yield 57 mg (60%). 1H NMR
(400 MHz, 80°C, [D6]DMSO, TMS): δ = 0.84 (t, 24 H), 1.24–1.4
(two m, 144 H), 1.70 (m, 16 H), 3.95 (t, 16 H), 5.05 (s, 8 H), 5.25
(two s, 8 H), 6.41 (s, 4 H), 6.58 (s, 8 H), 6.66 (s, 2 H), 6.78 (s, 4 H),
6.93 (d, 4 H), 7.27 (m, 12 H), 7.37 (t, 8 H), 7.5 (broad, 8 H), 7.65
(s, 2 H), 8.03 (t, 8 H), 8.37 (d, 8 H), 9.03 (d, 8 H), 9.35 (s, 8 H) ppm.
13C NMR (100 MHz, 80°C, [D6]DMSO, TMS): δ = 13.78, 21.96,
25.37, 28.59–29.65, 31.16, 67.36, 67.90, 69.12, 69.20, 100.14,
101.09, 105.70, 106.69, 115.16, 115.37, 115.53, 120.25, 124.69,
127.55, 129.06, 129.10, 130.12, 131.37, 133.49, 137.84, 139.11,
146.52, 152.04 (broad), 154.87, 156.97, 158.03, 159.42, 159.81,
160.05 ppm. C242H302F24N12O18P4Ru2 (4444): calcd. C 65.35, H
6.8, N 3.78; found C 65.70, H 6.11, N 3.43.
[4] a) A. D. Schlüter, J. P. Rabe, Angew. Chem. 2000, 112, 860–880;
Angew. Chem. Int. Ed. 2000, 39, 864–883; b) A. Zhang, l. Shu,
Z. Bo, A. D. Schlüter, Macromol. Chem. Phys. 2003, 204, 328–
339.
[5] A. K. Andreopoulou, B. Carbonnier, J. K. Kallitsis, T. Pakula,
Macromolecules 2004, 37, 3576–3587.
[6] a) E. C. Constable, P. Harverson, D. R. Smith, L. Whall, Poly-
hedron 1997, 16, 3615–3623; b) M. Heller, U. S. Schubert, Eur.
J. Org. Chem. 2003, 947–961.
[7] J. E. Kim, S.-Y. Song, H.-K. Shim, Synth. Met. 2001, 121,
1665–1666.
[8] N. Miyaura, A. Suzuki, Chem. Rev. 1995, 95, 2457–2483.
[9] A. K. Andreopoulou, J. K. Kallitsis, Macromolecules 2002, 35,
5808–5815.
[10] V. Percec, M. Kawasumi, Macromolecules 1993, 26, 3917–3928.
[11] Z. Bo, X. Zhang, X. Yi, M. Yang, J. Shen, Y. Ren, S. Xi, Polym.
Bullet. 1997, 38, 257–264.
[12] a) K. T. Potts, D. A. Usifer, A. Guadlupe, H. D. Abruña, J.
Am. Chem. Soc. 1987, 109, 3961–3967; b) E. C. Constable,
A. M. W. Cargill Thompson, D. A. Tocher, M. A. M. Daniels,
New J. Chem. 1992, 16, 855–867.
[13] a) J. Serin, X. Schultze, A. Adronov, J. M. J. Fréchet, Macro-
molecules 2002, 35, 5396–5404; b) J. K. Lee, D. Yoo, M. F.
Rubner, Chem. Mater. 1997, 9, 1710–1712.
[14] a) R. Knapp, S. Kelch, O. Schmelz, M. Rehahn, Macromol.
Symp. 2003, 204, 267–286; b) H. Hofmeier, S. Schmatloch, D.
Wouters, U. S. Schubert, Macromol. Chem. Phys. 2003, 204,
2197–2203.
Model Compound M: A carefully degassed mixture of diol 5 (0.11 g,
0.12 mmol), dodecyl bromide C12H25Br (0.117 g, 0.47 mmol),
TBAH (0.016 g, 0.047 mmol), o-DCB (1.5 mL), and NaOH (10 n,
1 mL) was vigorously stirred at 120°C under a continuous stream
of argon for 24 h. The resulting mixture was diluted with CHCl3
and precipitated from a tenfold amount of MeOH, filtered, redis-
olved in CHCl3, filtered once more in order to remove any traces of
salt, and precipitated from MeOH. The model didodecyloxy end-
functionalized diol, M, was obtained as a yellowish powder. Yield
0.126 g (84.3%). 1H NMR (400 MHz, 25°C, CDCl3, TMS): δ =
0.87 (t, 6 H), 1.25 (m, 32 H), 1.46 (m, 4 H), 1.8 (m, 4 H), 3.99 (t,
4 H), 6.96 (d, 4 H), 7.01 (d, 4 H), 7.35 (dd, 4 H), 7.39 (d, 4 H),
7.64 (s, 2 H), 7.84 (d, 4 H), 7.89 (m, 4 H), 8.66 (d, 4 H), 8.7 (s, 4
H), 8.74 (d, 4 H) ppm. 13C NMR (100 MHz, 25°C, CDCl3, TMS):
δ = 14.32, 22.96, 26.41, 29.62–29.9, 32.21, 68.55, 68.6, 114.86,
115.76, 118.72, 121.65, 123.95, 128.83, 130.67, 131.52, 131.53,
[15] T. Hayashi, M. Konishi, M. Kumada, T. Higushi, K. Hirotsu,
J. Am. Chem. Soc. 1984, 106, 158–163.
Received: May 24, 2005
Published Online: September 1, 2005
4458
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2005, 4448–4458