Synthesis and resonance energy transfer study on a random terpolymer containing a 2-(pyridine-2-yl)thiazole donor-type ligand and a luminescent [Ru(bpy)2(2-(triazol-4-yl)pyridine)]2+ chromophore

Article abstract of DOI:10.1021/ma201193e

A statistical terpolymer, containing a 2-(pyridine-2-yl)-1,3-thiazole donor-type system and an acceptor-type [Ru(bpy)₂(2-(triazol-4-yl) pyridine)]²⁺ chromophore as well as methyl methacrylate as comonomer, was synthesized using the c

Full text of DOI:10.1021/ma201193e

ARTICLE
pubs.acs.org/Macromolecules
Synthesis and Resonance Energy Transfer Study on a Random
Terpolymer Containing a 2-(Pyridine-2-yl)thiazole Donor-Type Ligand
and a Luminescent [Ru(bpy)2(2-(triazol-4-yl)pyridine)]2+ Chromophore
||
Bobby Happ,†,‡,§ Johann Sch€afer,§, Roberto Menzel,†,§ Martin D. Hager,†,‡,§ Andreas Winter,†,‡,§
||
||
J€urgen Popp,§, ,^ Rainer Beckert,*,†,§ Benjamin Dietzek,*,§, ,^ and Ulrich S. Schubert*,†,‡,§
†Laboratory of Organic and Macromolecular Chemistry (IOMC), Friedrich-Schiller-University Jena, Humboldtstrasse 10, 07743 Jena,
Germany
‡Dutch Polymer Institute (DPI), P.O. Box 902, 5600 AX Eindhoven, The Netherlands
§Jena Center for Soft Matter (JCSM), Friedrich-Schiller-Universit€at Jena, Humboldtstrasse 10, 07743 Jena, Germany
Institute for Photonic Technology Jena (IPhT), Albert-Einstein-Strasse 9, 07745 Jena, Germany
^Institute for Physical Chemistry, Friedrich-Schiller-University Jena, Helmholtzweg 4, 07743 Jena, Germany
S Supporting Information
b
ABSTRACT: A statistical terpolymer, containing a 2-(pyridine-2-yl)-
1,3-thiazole donor-type system and an acceptor-type [Ru(bpy)2-
(2-(triazol-4-yl)pyridine)]2+ chromophore as well as methyl metha-
crylate as comonomer, was synthesized using the controlled reversible
additionꢀfragmentation chain transfer polymerization (RAFT) ap-
proach. Additionally, the appropriate donor- and acceptor-type co-
polymers were synthesized, whereas only a maximum content of
5 mol % of the ruthenium(II) chromophore could be incorporated
into the macromolecules caused by its nitro-functionalization. The
resulting terpolymer exhibited a direct F€orster resonance energy
transfer from the thiazole to the ruthenium(II) subunit as indicated
by emission spectroscopy of the Ru(II) phosphorescence as well as
lifetime measurements and quantum yield determinations of the
thiazole fluorescence. The efficiency of the energy transfer was found to be higher than 70%.
’ INTRODUCTION
of the materials. Applications in the field of supramolecular
chemistry, conducting and photoresponsive materials, and cata-
lysis were established.5,7,32ꢀ37 In particular, the work of Frꢀechet and
Meyer is noteworthy regarding the synthesis of linear macro-
molecules containing bipyridine-functionalized ruthenium(II)
complexes. Frꢀechet et al. synthesized polymers containing cou-
Relating to artificial photosynthetic systems which are capable
to harvest and exploit photons enabled by solar energy,
ruthenium(II) complexes coordinated by N-heterocycles, such
as 2,20-bipyridines (bpy) and 2,20:60,200-terpyridines (tpy), have
been widely studied due to their predictable coordination
behavior as well as their interesting photophysical and electro-
chemical properties.1ꢀ19 Rutheniumꢀpolypyridine complexes
have particularly drawn significant interest, since they are able to
catalyze reduction and oxidation processes under visible light
irradiation enclosing a broad range of substrates. These privileges
could be utilized for applications including, e.g., the photocatalytic
decomposition of water and the implementation in photovoltaic
devices.20ꢀ26 The light sensitizing feature of ruthenium coordina-
tion compounds has been further used as luminescent chemosen-
sors as well as for the production of singlet molecular oxygen.27ꢀ31
Thus, considerable effort in the synthesis of metal-containing
polymers has been accomplished for combining the beneficial
properties of a metal ion complex, which provides the optoelectronic
capacity, and a polymer backbone enhancing the processability
2+
marin and Ru(dmbpy)3 (dmbpy = 4,40-dimethyl-2,20-bipyridine)
chromophores using a grafting as well as a copolymerization
approach utilizing free radical polymerization procedures. The
resulting bichromophoric macromolecules exhibited enhanced
absorption and luminescence properties compared to the single
Ru(II) complexes due to an efficient (>95%) energy transfer
between the coumarin donor dyes and the ruthenium subunit.38,39
Meyer et al. established a molecular assembly that combined both
the light-harvesting and electron transfer properties of a natural
photosynthetic system within a single macromolecule.33 The
Received: May 26, 2011
Revised:
July 14, 2011
Published: August 01, 2011
r
2011 American Chemical Society
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Scheme 1. Schematic Representation of the Various Synthesized Polymer Systems
support material in these studies was a mixed styrene-based
copolymer, which was prepared by free radical random copolymer-
ization of styrene with p-(chloromethyl)styrene. This copolymer
pictured a versatile precursor for the addition of a variety of
functional groups by nucleophilic substitution of chloride from
the pendant chloromethyl groups.40
However, the functionalization of polypyridine-based che-
lators with polymerizable groups can be synthetically trouble-
some and, therefore, requires new approaches in the
preparation of analogous bidentate chelating ligands that also
possess well-defined coordination properties and can be pre-
pared as well as modified with high effectiveness.41 In this
respect the CuI-catalyzed 1,3-cycloaddition of organic azides with
terminal alkynes (the CuAAC reaction) has a great potential
due to its mild reaction conditions and wide range of usable
substrates.42,43 The development of the CuAAC reaction
resulted in an increased interest toward the coordination
chemistry of 1,4-functionalized 1H-[1,2,3]triazoles due to
their potential as N-donor ligands.44ꢀ49
2-(pyridine-2-yl)thiazole donor-type system (Scheme 1). This
terpolymer is designed in order to mimic natural strategies for
light harvesting and—potentially—to be incorporated in supra-
molecular systems for conversion of energy from sunlight into
chemical energy.12,50ꢀ52 The thiazole dye absorbs light and
transfers a fraction of the excitation energy to a ruthenium(II)
complex, where a metal-to-ligand charge-transfer (MLCT) state
is directly excited for charge separation. Hence, the transition
metal complex can act as a primary electron donor when, in
perspective, combined with an electron acceptor, e.g., a semi-
conductor nanoparticle.50,53 Thus, the photoinduced molecular
processes resemble those in natural light harvesting, where the
capability of the special pair to harvest sunlight is increased by
dressing it with extended antenna structures.54ꢀ56 For the system
under investigation the main focus is on the energy transfer
taking place in the random donorꢀacceptor terpolymer. The
donor and acceptor units are designed for efficient F€orster
resonance energy transfer (FRET) as reported by Sch€afer et al.57
The successful incorporation of the donor and acceptor has been
confirmed by size exclusion chromatography (SEC) coupled
with a photodiode array detector. The trzpy ligand coordinated
to the ruthenium(II) ion included two features at the same
time: (i) affording the polymerizable group and (ii) an electron-
withdrawing moiety on the pyridine, which is responsible for the
In this contribution, the synthesis of a light-harvesting
terpolymer by controlled reversible additionꢀfragmentation
chain transfer (RAFT) radical polymerization is reported, com-
prising a luminescent ruthenium(II) complex coordinated
by a 2-(1H-[1,2,3]triazol-4-yl)pyridine system (trzpy) and a
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Scheme 2. Schematic Representation of the Synthesis of the Acceptor-Type Ruthenium(II) Complex
ruthenium complex luminescence. The latter consideration
facilitated the energy transfer studies with respect to emission
spectroscopy of the acceptor-type ruthenium subunit. The blue-
fluorescent thiazole was characterized by a good stability toward the
radical polymerization conditions as well as a considerable high
luminescence quantum yield.58
5-position of the pyridine ring. The copper(I)-catalyzed 1,3-
dipolar cycloaddition of 2-ethynyl-5-bromopyridine and 11-
azidoundecan-1-ol yielded 1 under typical CuAAC reaction
conditions, whereas 10 mol % of CuSO4 and 0.5 equiv of sodium
ascorbate served as Cu(I) source.43 Consecutive Sonogashira
cross-coupling with trimethylsilylacetylene and Pd0(PPh3)4, as
catalytic active palladium(0) source, as well as subsequent
deprotection of the trimethylsilyl-group by potassium fluoride
afforded 2 in moderate yield (47%). The following Sonogashira
coupling with 4-nitro-1-iodobenzene provided component 3.
The purity of the compounds has been proven by NMR spec-
troscopy, mass spectrometry, and elemental analysis. The hydro-
xyl moiety was changed to methyl methacrylate in order to
introduce a polymerizable group. The straightforward esterifica-
tion of 3 with methacryloyl chloride gave 4 in good yield (89%).
’ RESULTS AND DISCUSSION
Synthesis of the Monomers. The general synthesis route
of the acceptor-type ruthenium(II) complex 5 is depicted in
Scheme 2. In the first three steps, copper(I)-catalyzed azideꢀ
alkyne coupling (CuAAC) and Pd(0)-catalyzed Sonogashira
coupling were used to set up the trzpy scaffold bearing an
electron-withdrawing 4-nitrophenylacetylene moiety on the
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Scheme 3. Schematic Representation of the Synthesis of a
Polymerizable Donor-Type Thiazole Ligand
yielding the desired donor-type copolymer. The polymers 9a,c
were further purified by preparative SEC due to remaining
monomer 5 (see SEC graphs in the Supporting Information).
Selected characterization data of the final products are summar-
ized in Table 1.
A noteworthy synthesis issue appeared concerning the copo-
lymerization of the heteroleptic ruthenium(II) complex 5 and
MMA. It was found after optimization of the reaction conditions
(Table 2) that initiation of the polymerization only occurred if
the molar content of 5 did not exceed 5 mol %. This fact was
attributed to the retardation nature of the NO2 group.64 Conse-
quently, the ruthenium(II) content of the terpolymer 9c was kept
below 5 mol % to ensure an efficient initiation of the reaction.
Energy Transfer Studies. When considering the emission and
absorption spectra of the donorꢀacceptor pair 5 and 8 (Figure 1), it
is apparent that the requirements for FRET are met, which were a
significant emission quantum yield of the donor and a spectral over-
lap of the donor emission and the acceptor absorption band. The
overlap between the donor (8) emission and the acceptor (5)
extinction (hatched region in Figure 1) resulted in an overlap
integral value of J = 4.6 Mꢀ1 cmꢀ1 nm4 (compare Table 3). The
F€orster radius, which corresponds to the distance between donor
and acceptor at which the efficiency of FRET drops to 50%, was
calculated to R0 = 4 nm. The average distance between the donor
and the acceptor units had to be smaller than R0 in order to
obtain efficient FRET, which was achieved by copolymerizing 5
and 8 in a polymer backbone delivering 9c. In the terpolymer the
thiazoles were randomly distributed in the vicinity of the Ru(II)
complexes. Because of the fact that the geometrical constraints
discussed above were met, FRET from the thiazole to the MLCT
band of 5 (centered at 450 nm) was expected to occur in the
polymer.
In order to verify the appearance of FRET in the donorꢀ
acceptor polymer 9c, excitation spectra were recorded of the
donor-type polymer 9b, the acceptor-type polymer 9a, and the
donorꢀacceptor polymer 9c (see Figure 2). For recording the
luminescence excitation spectra of the Ru(II) subunit the emis-
sion was monitored at 620 nm, where no donor fluorescence
from subunit 8 appeared. Therefore, a difference in the lumines-
cence excitation spectra of 9a and 9c indicated contributions
from thiazole excitation to the luminescence of the ruthenium-
(II) unit as seen in the additional excitation band at 380 nm in 9c
(see Figure 2). This excitation band is spectrally centered, where
the thiazole emission is excited in the donor-type polymer 9b as
indicated by the dashed line in Figure 2. These findings point
toward FRET; i.e., excitation of the donor led to amplified
luminescence of the acceptor.
The heteroleptic ruthenium(II) complex 5 was synthesized by
heating cis-dichlorobis(4,40-dimethyl-2,20-bipyridine)ruthenium(II)
Ru(dmbpy)2Cl2 and ligand 4 under microwave irradiation
45
(120 ꢀC). The methacryl moiety was found to be stable under
these conditions as confirmed by preliminary experiments. After
the reaction was completed, a 10-fold excess of NH4PF6 was
added to precipitate the ruthenium(II) complex. Precipitation
occurred usually within 30 min, and the complex was finally
purified by recrystallization from ethanol and subsequent
washing with cold ethanol (yield >90%). The verification of
the structure was carried out by 1H and 13C NMR spectroscopy
as well as by high-resolution mass spectrometry (HR-ESI MS).
The 4-hydroxythiazole 6 was prepared by a cyclization process
of pyridine-2-carbothioamide with ethyl 2-bromophenylacetate.59
Williamson-type etherification of 6 with 3-bromopropan-1-ol as
electrophile yielded 7 in good yield (68%) under mild condi-
tions. Subsequently, the hydroxyl group was reacted with metha-
cryloyl chloride under basic conditions to yield the polymerizable
ester 8 (Scheme 3). All compounds had to be purified by column
chromatography to ensure a proper reagent grade for the
following radical polymerization reactions. The confirmation of
the structures was performed by NMR spectroscopy, mass
spectrometry, and elemental analysis.
Synthesis of the Polymers. Two copolymers and one
terpolymer were synthesized based on a poly(methyl methacrylate)
(PMMA) backbone, where 8 served as the donor and 5 as the
acceptor unit, respectively (Scheme 4). In general, statistical
RAFT copolymerizations were performed in concentrated solu-
tions (∼2 M solution of the monomer) to allow the polymeriza-
tions to proceed in a controlled manner.60 2-Cyanobutan-2-yl
benzodithioate (CBBD) was used as RAFT agent, since it is
known to provide a narrow molar mass distribution, in particular
for PMMA, as it has been described in the literature.61,62 The
conversion of the reactions was driven to roughly 80% using a
standard reaction time of 16 h. Because of the insolubility of 5 in
commonly utilized solvents for radical polymerization (i.e.,
toluene, ethanol), the RAFT polymerizations were performed
in N,N-dimethylacetamide (DMA), as described elsewhere.63
After the reaction, 9b was precipitated into cold diethyl ether
The additional excitation band in the luminescence of the
Ru(II) subunit is accompanied by a reduction of the donor-based
quantum yield in the donorꢀacceptor polymer 9c compared to
that of 9b (Table 3). While measuring the donor-based quantum
yield in donor-type polymer 9b was straightforward, the quantum
yield measurement in the donorꢀacceptor polymer 9c required
adequate care: because of overlapping donor and acceptor
absorptions (see Figures 1 and 2), it was not possible to
exclusively excite donor molecules in the donorꢀacceptor poly-
mer in order to directly measure the donor-based emission
quantum yields. Taking into account these overlapping absorp-
tions, the molar extinction coefficients of donor and acceptor
at the excitation wavelength had to be considered as well as the
ratio of donors and acceptors within the polymer chain. Con-
sidering these properties, the quantum yield measurement in the
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Scheme 4. Schematic Representation of the Synthesis of the Statistical Copolymers 9aꢀc
Table 1. Selected Characterization Data for the Polymers 9aꢀc
polymer
Ru(II) content [mol %]a
dye content [mol %]a
Mn,theo
Mn,NMR [g molꢀ1 a
]
DPa,b
Mn,SEC [g molꢀ1 c
]
PDId
9a
9b
9c
3
8 500
11 700
11 200
9 000
12 000
12 800
90
90
5 000
15 100
8 000
1.32
1.13
1.32
7
6
10
127
a Determined by 1H NMR spectroscopy. b Degree of polymerization. c Determined by SEC using PMMA calibration. d Polydispersity index determined
by SEC.
donorꢀacceptor polymer 9c followed the same procedure as the
emission quantum yield measurements of 8 and 9b.
lifetimes, whereas the emission spectrum of 9b was similar to that
of 8 (see Figure 3). The reason for the increased lifetime was
attributed to random coiling of the polymer in solution changing
sufficiently the environment of individual dyes.65 Nevertheless,
choosing 9b as reference was a critical step for the analysis of the
excitation energy transfer in the donorꢀacceptor polymer 9c:
the lengths of 9b and 9c are not identical, and additionally, the
reference polymer could exhibit a different coiling compared to
the donorꢀacceptor polymer. Nonetheless, energy transfer
efficiencies were calculated as described in the Experimental Section
using the quantum yields and lifetime measurements from the
reference system 9b and the donorꢀacceptor polymer 9c.
In the work presented here the donor-type polymer 9b,
lacking acceptor molecules, was synthesized as reference system
for 9c. It is expected that the fluorescence quantum yield and the
lifetime of the reference polymer are practical for calculating the
transfer efficiency for energy transfer in the donorꢀacceptor
polymer 9c. The importance of using such a reference system
instead of the monomeric unit 8 is obvious from Table 3. Upon
integration into the polymer, the fluorescence quantum yield of
the thiazole increased compared to the monomeric fluorophore.
Such behavior is in agreement with the measured fluorescence
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Table 2. Optimization of the Reaction Conditions of the
Copolymerization of 5 and MMA
M/I ratioa Ru(II) content [mol %] tR [h] AIBN [mol %] conv [%]
100
200
50
10
10
10
10
10
6
18
18
18
18
18
18
18
0.25
0.25
0.25
0.5
0
0
0
100
100
100
100
0
1
0
0.25
0.25
0
4
85
a Monomer/initiator ratio (MMA/CBBD).
Figure 2. Excitation spectra of the donorꢀacceptor polymer 9c (red)
and the acceptor polymer 9a (black) recorded by monitoring the
luminescence of 5 at 620 nm (solid), normalized to maximal intensity
in the MLCT excitation band at 460 nm. The donor polymer fluores-
cence excitation spectrum from 9b recorded at 450 nm (dashed) was
normalized to the maximal emission intensity. The spectra were taken in
dichloromethane at room temperature.
Figure 1. Extinction and emission spectra of 8 (red) and 5 (black) at
room temperature measured in dichloromethane (excitation at 370 and
462 nm, respectively). The hatched region indicates the donorꢀaccep-
tor spectral overlap, and the dashed line displays the integrand of the
overlap integral.
Table 3. Representation of the Photophysical Properties
from 8ꢀ9c
λabs,max (nm) λem,max (nm)
J
compd
[log ε]
[excitation] Φa τ (ns)b (Mꢀ1 cmꢀ1 nm4)
8
375 [5.14]
286 [5.47]
330 [5.17]
443 [4.68]
375 [5.14]
285
447 [370]
620 [460]
0.40
1.8
9a
9b
9c
447 [370]
449 [370]
0.58
0.06
2.7
0.064c
4.6d
ꢀe
350
442
a Emission quantum yield measured in dichloromethane at room tem-
perature. b Lifetime measured in dichloromethane at room temperature.
c Overlap integral considering homotransfer for 9b. d Overlap integral of
emission from 8 with absorption of 9a. No single-exponential decay
was observed.
Figure 3. In panel A, the dashed line denotes the emission spectra of the
reference polymer 9b and the solid line the emission of the monomer 8
in dichloromethane, excited at 375 nm. In panel B, the red line fits the
monoexponential decay of the measured data (dotted).
e
Time-resolved measurements of the donor lifetime in 9b and
9c (see Figure 4) revealed that the donor emission decayed more
rapidly in the presence of an acceptor as the interaction between
the donor and the acceptor quenched the donor emission. On
the basis of the temporal emission profiles of the donor in 9b
and 9c, the FRET efficiency E was calculated to be 70% (see
Experimental Section for details). Although there are many
possibilities for excitation quenching in polymers—such as energy
migration, excitonꢀexciton annihilation,66ꢀ68 and excimer
formation69—it was assumed that this shortening of the donor
decay time in the donorꢀacceptor polymer is dominated
by FRET. Because of the overlap between donor emission and
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Figure 5. Donor fluorescence curves of compound 9b (donor alone
polymer) and of 9c (donorꢀacceptor polymer) in different solvents:
acetonitrile (red squares), dichloromethane (blue circles), chloroform
(black triangles). The longer living fluorescence (single-exponential
decay) stems from the donor alone polymer and the shortened
fluorescence (non-exponential decay) from the donorꢀacceptor poly-
mer. Excitation wavelength: 290 nm.
Figure 4. Donor decay profile of the reference polymer 9b and the
donorꢀacceptor polymer 9c in dichloromethane at room temperature,
excited at 290 nm. The instrument response function (IRF) was
measured by scattered light.
donor absorption (see Figure 1) homoenergy transfer, i.e., FRET
between dyes of the same type, is not excluded, but the calculated
overlap integral for such energy transfer, and consequently the
resulting transfer rate, was 2 orders of magnitude smaller than
FRET between donor and acceptor molecules of the type 8 and 5
(see Table 3). Thus, in polymer 9c no considerable homoenergy
transfer will occur, even if there is a higher number of donor than
acceptor molecules. Along the same lines contributions from
back-energy transfer, i.e., FRET from the acceptor to the donor
subunit, were excluded. Excimer formation was excluded as well
because it typically causes an additional emission band beyond
the red end of the fluorescence, which was not observed for 9c.70
Comparing the FRET results presented here to analogous work
on other polymers and dendrimers,65,71,72 it can be stated that in
9 effects, such as energy migration, excimer formation, or local
concentration quenching, were avoided.73 These effects cause a
reduction of the emission quantum yield and a nonexponential
emission decay. Neither of these effects were observed in the
reference polymer 9b. Probably this is caused by the low
concentration of donor units in the polymer backbone compared
to dendritic systems.65
Additionally, Figure 4 shows a nonexponential donor emission
in the presence of acceptor units in the terpolymer. This is due to
the fact that no fixed donorꢀacceptor distances existed within
the polymer. This situation resulted in different FRET rates for
individual donorꢀacceptor pairs and, therefore, different decay
rates for individual photoexcited donors.
Moreover, preliminary solvent-dependent donor lifetime mea-
surements were carried out and are depicted in Figure 5. The
measured donor lifetimes in presence of the ruthenium(II) acceptor
were shortened (non-single-exponential decay) compared to the
donor alone lifetimes (single-exponential decay) due to the reso-
nance energy transfer. The shape of the decay curves of the polymers
themselves in different solvents are very similar, and thus, no signi-
ficant change in the conformation of the polymers can be concluded.
A comparison of the transfer efficiencies in the different solvents was
not possible because the avalanche photodiode detects scattered
photons from the excitation pulse as well. This may result in
incorrect calculated transfer efficiencies.
example, Dexter type energy transfer can also occur at donorꢀ
ꢀ
acceptor distances smaller than 10 Å, when donor emission and
acceptor absorption spectrally overlap.70 Furthermore, transla-
tional diffusion can cause an enhancement of the FRET efficiency
compared to systems with a static distance distribution of donor
and acceptor as reported by Lakowicz et al.74 and Thomas et al.75
Regardless of a possibly incomplete description of the excitation
energy transfer only by FRET, the donorꢀacceptor polymers
designed for efficient FRET allow enhanced light harvesting in a
Ru(II) complex, whereupon energy is focused into the 1MLCT
band. By considering the charge separating character of the
MLCT states, this process increased the accessibility of Ru(II)
complexes as primary electron donors in photocatalytic systems.
’ CONCLUSIONS
Polymers containing a 1,3-thiazole dye (energy donor) and a
ruthenium(II) chromophore (energy acceptor) were synthe-
sized using a controlled RAFT polymerization procedure. The
terpolymer was able to relay the absorbed energy by energy
transfer from the thiazole donor to the ruthenium(II) acceptor.
The ruthenium(II) content in the macromolecules was limited to
5 mol % at most, since for higher metal content the polymeri-
zation could not be initiated. The donorꢀacceptor functional-
ized terpolymer displayed a reasonable energy transfer efficiency
of over 70%. Those polymeric systems will be practical, e.g., in
terms of the synthesis of artificial photosynthetic systems, in
which they can act as light-harvesting antennas.
’ EXPERIMENTAL SECTION
Materials and Instrumentation. All reagents were acquired
from commercial sources and used without further purification. Solvents
were dried and distilled according to standard procedures and stored
under nitrogen. All reactions were performed in air-dried flasks under a
nitrogen atmosphere, unless stated otherwise. For the Pd0-catalyzed
cross-coupling and the RAFT polymerization procedures, the solvents
were degassed by bubbling with nitrogen 0.5 h before use. Purification of
the reaction products was carried out by column chromatography using
Of course, any description of donor quenching in donorꢀ
acceptor polymers is incomplete using F€orster’s theory only; for
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40ꢀ63 μm silica gel. Analytical thin layer chromatography (TLC) was
performed on aluminum sheets precoated with silica gel 60 F254, and
visualization was accomplished with UV light (254 nm). Preparative size
exclusion chromatography (SEC) was carried out on Bio-Rad S-X1
beads (size exclusion 600ꢀ14 000 g/mol), swollen in dichloromethane.
The conversion of the copolymerization reactions was determined by 1H
NMR spectroscopy. The heteroleptic ruthenium(II) complexes were
synthesized by microwave-assisted reactions using a Biotage Initiator
ExpEU (maximum power: 400 W; working frequency: 2450 MHz) with
closed reaction vials. During the experiments the temperature and the
9b, respectively (see Table 3).
ΦDA
E ¼ 1 ꢀ
ΦD
ð3Þ
The obtained value of 90% for the transfer efficiency E is only an
estimate because of the uncertainty for the measured quantum yields.
But the significant reduction of the donor fluorescence quantum yield
upon incorporation into the donorꢀacceptor polymer from Φ = 0.58
(9b) to 0.06 (9c) proved FRET to take place. A more accurate value for
E is achieved from the time-resolved measurements. Consequently, the
value E = 0.7 in this article was discussed and assumed.
1
pressure profiles were detected. 1D (1H and 13C) and 2D (1Hꢀ H
COSY) nuclear magnetic resonance spectra were recorded on a Bruker
AC 300 (300 MHz) at 298 K. Chemical shifts are reported in parts per
million (ppm, δ scale) relative to the signal of the applied solvent.
5-Bromo-2-ethynylpyridine,45 2-cyanobutan-2-yl benzodithioate,61
dichloro(cycloocta-1,5-diene)ruthenium(II),45 cis-dichlorobis(4,40-di-
methyl-2,20-bipyridine)ruthenium(II),45 and 5-phenyl-2-(pyridin-2-
yl)-1,3-thiazol-4-ol59 were synthesized according to literature reports.
Photophysical Measurements and Calculations. Measure-
ments of the fluorescence intensity were carried out on a Perkin-Elmer
lambda16 UV/vis spectrometer in the perpendicular excitationꢀemis-
sion geometry, while the absorbance at the excitation wavelength was
<0.05. The calculation of fluorescence quantum yields was done
according to following equation76
Synthesis of 11-(4-(5-Bromopyridin-2-yl)-1H-1,2,3-triazol-
1-yl)undecan-1-ol (1). Sodium azide (590 mg, 9 mmol) was
dissolved in dimethyl sulfoxide (20 mL), and 11-bromo-1-undecanol
(1.5 g, 6 mmol) was added subsequently. After stirring 24 h at room
temperature, water (30 mL) was added to quench the reaction, and the
suspension was extracted three times with diethyl ether. The organic
phases were combined, washed with brine, and dried over Na2SO4. The
solution was subsequently concentrated in vacuo to yield 11-azido-1-
undecanol as slight yellow oil (1.25 g, 98%).
To a solution of the organic azide, 2-ethynyl-5-bromopyridine
(1.07 g, 5.9 mmol) and CuSO4 (88 mg, 0.59 mmol, dissolved in 1 mL
water) in an EtOH/water mixture (7:3 ratio, 50 mL) was added sodium
ascorbate (570 mg, 2.9 mmol, dissolved in 2 mL of water), and the
reaction was stirred for 72 h at room temperature. The yellow precipitate
was filtered and recrystallized from ethanol, yielding the pure product as
I Ar n2
Φ ¼ Φr
ð1Þ
Ir A nr2
1
white solid (1.55 g, 68%). H NMR (CDCl3, 300 MHz): δ = 8.63
where Φ is the quantum yield, I is the corrected integrated emission
intensity, A is the absorbance at the excitation wavelength, and n is the
refractive index of the solvent, i.e., in this study dichloromethane of
spectroscopic grade from Sigma-Aldrich. The subscript “r” refers to a
reference fluorophore of known quantum yield, whereas quinine sulfate
(Φ = 0.55) was used in our investigations.76
The fluorescence decay curves were obtained by a Hamamatsu streak
scope C4334 in time-correlated single photon counting (TCSPC)
modus. Triggering was carried out by the Hamamatsu trigger unit
C4792-01. After excitation with a frequency-tripled Ti-sapphire laser
(Tsunami, Newport Spectra-Physics GmbH), i.e., λex = 290 nm, in
perpendicular direction the fluorescence emission wavelength were
separated by a Chromex 250IS imaging spectrograph. The repetition
rate of the laser was adjusted to 0.8 MHz by a pulse selector (model
3980, Newport Spectra-Physics GmbH). All measurements were carried
out at concentrations below 10ꢀ6 M. Solvent-dependent donor lifetime
measurements were performed with a time-correlated single-photon
counting module from Becker & Hickl using an avalanche photodiode as
detector. The solvents were acetonitrile, dichloromethane, and
chloroform.
In order to quantify the efficiency of FRET the time-dependent
intensity decay curve of the donor-alone polymer 9b was measured and
compared to the respective intensity decay of 8 incorporated into the
donorꢀacceptor polymer 9c using eq 2, which can be derived from ref
77. Here, τD and τDA refer to the donor lifetime in the donor-alone
polymer 9b and to the donor lifetime in the donorꢀacceptor polymer
9c, respectively. IDA is the time-dependent intensity of the donor
fluorescence in presence of an acceptor, which is normalized to the
amplitude I0DA. The resultant efficiency E is 0.7.
(s, 1H), 8.12ꢀ8.08 (m, 2H), 7.91 (dd, J = 8.5 Hz, J = 2.1 Hz, 1H), 4.42
(t, J = 7.2 Hz, 2H, NꢀCH2), 3.67ꢀ3.61 (m, 2H, OꢀCH2), 1.98ꢀ1.93
(m, 2H), 1.59ꢀ1.54 (m, 2H), 1.39ꢀ1.27 (m, 14H). 13C NMR (CDCl3,
75 MHz): δ = 150.4, 148.9, 147.4, 139.4, 121.9, 121.3, 119.3, 62.8, 50.5,
32.7, 30.0, 29.4, 29.3, 29.2, 28.8, 26.3, 25.7. ESI-TOF MS: m/z = 418.33
(15%, [M + Na]+), 394.14 (100%, [M]+). Anal. Calcd for C18H27BrN4O:
C, 54.69%; H, 6.88%; N, 14.17%. Found: C, 54.76%; H, 7.08%; N, 14.02%.
Synthesis of 11-(4-(5-Ethynylpyridin-2-yl)-1H-1,2,3-triazol-
1-yl)undecan-1-ol (2). To a solution of 11-(4-(5-bromopyridin-2-
yl)-1H-1,2,3-triazol-1-yl)undecan-1-ol (1, 1.5 g, 3.79 mmol), CuI (34
mg, 0.18 mmol), and tetrakis(triphenylphosphine)palladium(0) (220
mg, 0.18 mmol) in NEt3/THF (1:1 ratio, 50 mL) was added trimethyl-
silylacetylene (280 mg, 2.8 mmol), and the mixture was stirred 48 h at
40 ꢀC. After removal of the solvent under reduced pressure, the residue
was purified by gel filtration on silica (CHCl3/EtOAc 2:1 ratio).
For the deprotection, the product was dissolved in dichloromethane
(30 mL) and treated with tetrabutylammonium fluoride trihydrate
(1.8 g, 1.5 equiv). After 4 h, the solvent was removed and the crude
product was finally purified by column chromatography on silica
(EtOAc) yielding the product as off-white powder (580 mg, 45%). 1H
NMR (CDCl3, 300 MHz): δ = 8.66 (s, 1H), 8.16ꢀ8.14 (m, 2H), 7.85
(dd, J = 8.2 Hz, J = 2.0 Hz, 1H), 4.41 (t, J = 7.1 Hz, 2H, NꢀCH2),
3.64ꢀ3.59 (m, 2H, OꢀCH2), 3.25 (s, 1H, CtCꢀH), 1.95ꢀ1.92 (m,
2H), 1.56ꢀ1.51 (m, 2H), 1.33ꢀ1.25 (m, 14H). 13C NMR (CDCl3,
75 MHz): δ = 152.4, 149.7, 147.7, 139.9, 122.3, 119.3, 118.0, 80.8, 80.5,
62.9, 50.5, 32.7, 30.1, 29.4, 29.3, 29.2, 28.8, 26.3, 25.6. ESI-TOF MS: m/z
= 340.24 (100%, [M]+). Anal. Calcd for C20H28N4O: C, 70.56%; H,
8.29%; N, 16.46%. Found: C, 70.22%; H, 7.98%; N, 16.41%.
Synthesis of 11-(4-(5-((4-Nitrophenyl)ethynyl)pyridine-2-yl)-
1H-1,2,3-triazol-1-yl)undecan-1-ol (3). 11-(4-(5-Ethynylpyridin-
2-yl)-1H-1,2,3-triazol-1-yl)undecan-1-ol (2, 450 mg, 1.32 mmol), 4-ni-
tro-1-iodobenzene (336 mg, 1.35 mmol), tetrakis(triphenylphosphine)-
palladium(0) (30 mg, 0.026 mmol), and CuI (5 mg, 0.026 mmol) were
dissolved in a NEt3/THF mixture (3:7, 30 mL), and the solution was
stirred for 72 h at room temperature. The solution was evaporated under
reduced pressure, and the pure product was isolated by column
chromatography over silica (CHCl3/EtOAc 8:1 ratio) as a slight yellow
Z
τDA
τD
1
IDAðtÞ dt
E ¼ 1 ꢀ
¼ 1 ꢀ
ð2Þ
τD
ID0 A
In analogy to the determination of the transfer efficiency based on
time-resolved measurements, the emission quantum yield of the donor
was measured in 9b (donor-only polymer) and in the donorꢀacceptor
polymer 9c in order to calculate the transfer efficiency from eq 3, where
ΦDA and ΦD refer to the donor emission quantum yield of 8 in 9c and
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powder (560 mg, 92%). 1H NMR (CDCl3, 300 MHz): δ = 8.74 (s, 1H),
8.26ꢀ8.22 (m, 2H), 8.19ꢀ8.17 (m, 2H), 7.92 (dd, J = 8.2 Hz, J = 2.1 Hz,
1H), 7.71ꢀ7.68 (m, 2H), 4.42 (t, J = 7.1 Hz, 2H, NꢀCH2), 3.63 (t, J =
6.6 Hz, 2H, OꢀCH2), 1.99ꢀ1.93 (m, 2H), 1.58ꢀ1.53 (m, 2H),
1.34ꢀ1.27 (m, 14H). 13C NMR (CDCl3, 75 MHz): δ = 152.0, 149.9,
147.5, 147.3, 139.6, 132.3, 129.4, 123.7, 122.4, 119.5, 118.0, 91.2, 90.8,
62.9, 50.5, 32.7, 30.1, 29.4, 29.3, 29.2, 28.8, 26.3, 25.6. ESI-HRMS calcd
for C26H32N5O3 [M + H]+: 462.2500. Found: 462.2486.
Synthesis of 11-(4-(5-((4-Nitrophenyl)ethynyl)pyridine-2-yl)-
1H-1,2,3-triazol-1-yl)undecyl Methacrylate (4). 11-(4-(5-((4-
Nitrophenyl)ethynyl)pyridine-2-yl)-1H-1,2,3-triazol-1-yl)undecan-1-ol (3,
400 mg, 0.88 mmol) and triethylamine (240 μL, 1.76 mmol) were dissolved
in dry dichloromethane (10 mL). The solution was cooled to 0 ꢀC,
methacryloyl chloride (200 μL, 2 mmol) was added, and subsequently
the solution was stirred for 2 h at 0 ꢀC and further 24 h at room temperature.
The reaction mixture was washed with saturated NaHCO3 solution, and
after drying of the organic layer over MgSO4, the solvent was removed in
vacuo. The crude product was purified by column chromatography on silica
(EtOAc/CHCl3 3:1) providing the pure product as slight yellow solid (410
mg, 88%). 1H NMR (CDCl3, 300 MHz): δ = 8.75 (s, 1H), 8.27ꢀ8.24 (m,
2H), 8.21ꢀ8.17 (m, 2H), 7.94 (dd, J = 8.2 Hz, J = 2.1 Hz, 1H), 7.72ꢀ7.69
(m, 2H), 6.09 (s, 1H, C = CH2), 5.54 (s, 1H, C = CH2), 4.42 (t, J = 7.1 Hz,
2H, NꢀCH2), 4.13 (t, J = 6.7 Hz, 2H, OꢀCH2), 2.01ꢀ1.97 (m, 2H), 1.93
(s, 3H, CH3), 1.70ꢀ1.64 (m, 2H), 1.35ꢀ1.26 (m, 14H). 13C NMR
(CDCl3, 75 MHz): δ = 167.5, 151.7, 149.8, 147.3, 139.8, 136.5, 132.4,
129.3, 125.1, 123.7, 122.6, 119.7, 118.1, 91.0, 64.8, 50.6, 30.2, 29.41,
29.38, 29.31, 29.1, 28.9, 28.5, 26.4, 25.9, 18.3. ESI-HRMS calcd for
C30H35N5NaO4 [M + Na]+: 552.2587. Found: 552.2580.
(m, 2H), 7.33ꢀ7.24 (m, 2H), 4.69 (t, J = 5.9 Hz, 2H, OꢀCH2), 3.87
(t, J = 5.9 Hz, 2H, CH2ꢀOH), 2.90 (s, 1H, OH), 2.10 (p, J = 5.9 Hz, 2H,
CH2). 13C NMR (CDCl3, 63 MHz): δ = 160.9, 159.2, 150.9, 149.5,
137.0, 131.5, 128.7, 126.97, 126.96, 124.3, 118.9, 115.0, 67.7, 59.2, 32.8.
EI MS: m/z = 312.09 (100%, [M]+), 254.05 (75%, [MꢀC3H6O]+).
Anal. Calcd for C17H16N2O2S: C, 65.36%; H, 5.16%; N, 8.97%; S,
10.26%. Found: C, 65.38%; H, 5.18%; N, 9.10%; S, 9.92%.
Synthesis of 3-((5-Phenyl-2-(pyridin-2-yl)thiazol-4-yl)oxy)-
propyl Methacrylate (8). To a solution of 3-((5-phenyl-2-(pyridin-2-
yl)thiazol-4-yl)oxy)propan-1-ol (7, 1.40 g, 4.48 mmol) and triethylamine
(2.24 g, 22.4 mmol) in dry CH2Cl2 (30 mL) was added methacryloyl
chloride (0.94 g, 8.96 mmol). The reaction was stirred for 24 h at ambient
temperature, and subsequently, the organic phase was thoroughly washed
with water (3 ꢁ 20 mL) and saturated NaHCO3 solution to hydrolyze the
excess acid chloride. After drying of the organic phase over MgSO4 and
evaporation of the solvent (T<40ꢀC), the crude product was purified using
column chromatography on silica (CHCl3) yielding the pure product as
yellow oil (1.5 g, 88%). 1H NMR (CDCl3, 250 MHz): δ = 8.60 (d, J =
4.70 Hz, 1H), 8.09 (d, J = 7.9 Hz, 1H), 7.83ꢀ7.67 (m, 3H), 7.45ꢀ7.32 (m,
2H), 7.32ꢀ7.19 (m, 2H), 6.13 (s, 1H, CdCꢀH), 5.55 (s, 1H, CdCꢀH),
4.64 (t, J = 6.3 Hz, 2H, OꢀCH2), 4.40 (t, J = 6.3 Hz, 2H, C(O)OꢀCH2),
2.26 (p, J = 6.3 Hz, 2H, CH2), 1.95 (s, 3H, CH3). 13C NMR (63 MHz,
CDCl3): δ = 167.4, 160.5, 158.9, 151.2, 149.4, 136.9, 136.3, 131.6, 128.8,
126.94, 126.85, 125.5, 124.2, 118.9, 114.8, 67.1, 61.7, 29.0, 18.3. EI MS:
m/z = 380.12 (30%, [M]+), 254.05 (10%, [MꢀC7H11O2]+). Anal. Calcd
for C21H20N2O3: C, 66.29%; H, 5.30%; N, 7.36%; S, 8.43%. Found: C,
66.41%; H, 5.32%; N, 7.22%; S, 7.98%.
General RAFT Copolymerization Procedure. The respective
methacrylate-functionalized monomer, methyl methacrylate (125 μL,
1.163 mmol), 2-cyanobutan-2-yl benzodithioate (2.7 mg, 1.6 μmol,
1 mol %), and 2,20-azobis(2-methylpropionitrile) (0.5 mg, 0.4 μmol,
0.25 mol %) were dissolved in N,N-dimethylacetamide (600 μL) in a
2 mL microwave vial. The vial was sealed, and the solution was degassed
for 0.5 h under nitrogen. Subsequently, the reaction mixture was stirred
at 85 ꢀC (oil bath temperature) for 16 h. The crude product was
precipitated in cold diethyl ether and purified by preparative size
exclusion chromatography (BioBeads S-X1, CH2Cl2 as eluent) yielding
the pure desired copolymer.
Synthesis of Bis(4,40-dimethyl-2,20-bipyridine)-[11-(4-(5-
((4-nitrophenyl)ethynyl)pyridin-2-yl)-1H-1,2,3-triazol-1-yl)-
undecyl methacrylate]ruthenium(II) Hexafluorophosphate (5).
cis-Dichlorobis(4,40-dimethyl-2,20-bipyridine)ruthenium(II) (87 mg,
0.16 mmol) and 11-(4-(5-((4-nitrophenyl)ethynyl)pyridin-2-yl)-1H-
1,2,3-triazol-1-yl)undecyl methacrylate (4, 85 mg, 0.16 mmol) were
suspended in ethanol (10 mL). After heating under microwave irradia-
tion at 125 ꢀC for 2 h, the red solution was filtered and treated with a
10-fold excess of NH4PF6. Subsequently, precipitation occurred within
30 min, and the red precipitate was filtered off after 1 day. The preci-
pitate was washed twice with cold ethanol, and recrystallization from
Synthesis of Polymer 9a. According to the general procedure,
bis(4,40-dimethyl-2,20-bipyridine)-[11-(4-(5-((4-nitrophenyl)ethynyl)-
pyridin-2-yl)-1H-1,2,3-triazol-1-yl)undecyl methacrylate]ruthenium-
(II) hexafluorophosphate (5, 60 mg, 0.047 mmol) was reacted to yield
the product as red solid (106 mg, 45%). 1H NMR (CDCl3, 300 MHz): δ
= 8.80 (br), 8.35ꢀ8.10 (br), 7.70ꢀ7.50 (br), 7.45ꢀ7.25 (br), 7.15ꢀ7.08
(br), 4.40 (br), 3.95 (br), 3.58 (s), 2.60ꢀ2.45 (br), 2.05ꢀ1.65 (br),
1.45ꢀ1.15 (br), 1.0 (s), 0.8 (s). 13C NMR (CDCl3, 75 MHz): δ = 178.1,
177.8, 176.9, 157.0, 156.6, 156.3, 152.9, 150.9, 150.8, 147.8, 147.1, 140.4,
132.7, 128.8, 128.7, 128.0, 127.7, 126.0, 124.9, 124.6, 124.2, 124.1, 123.7,
122.4, 121.5, 93.7, 87.7, 54.4ꢀ51.8, 44.9, 44.5, 29.4, 21.5, 21.2, 18.7, 16.5.
Synthesis of Polymer 9b. According to the general procedure,
3-((5-phenyl-2-(pyridin-2-yl)thiazol-4-yl)oxy)propyl methacrylate (8,
35 mg, 0.093 mmol) was reacted to yield the product as orange solid
(81 mg, 51%). 1H NMR (CDCl3, 300 MHz): δ = 8.59 (br), 8.15ꢀ8.0
(br), 7.8ꢀ7.70 (br), 7.40ꢀ7.30 (br), 4.60 (br), 4.20 (br), 3.70ꢀ3.45
(br), 2.2ꢀ1.70 (br), 1.48ꢀ1.30 (br), 1.0 (br), 0.83 (br). 13C NMR
(CDCl3, 75 MHz): δ = 178.1, 177.8, 176.9, 160.4, 158.7, 151.1, 149.3,
148.3, 137.1, 131.5, 128.9, 128.7, 126.9, 124.2, 123.1, 119.0, 114.7, 66.9,
65.8, 54.3ꢀ51.7, 44.8, 44.5, 18.7, 16.4, 15.2.
1
ethanol yielded the pure product as red powder (184 mg, 89%). H
NMR (CD2Cl2, 300 MHz): δ = 8.75 (s, 1H), 8.29ꢀ8.07 (m, 8H),
7.73ꢀ7.46 (m, 7H), 7.31ꢀ7.26 (m, 3H), 7.16 (d, J = 5.9 Hz, 1H), 6.07
(s, 1H, CdCꢀH), 5.56 (m, 1H, CdCꢀH), 4.39 (t, J = 7.4 Hz, 2H,
NꢀCH2), 4.12 (t, J = 6.7 Hz, 2H, C(O)OꢀCH2), 2.61ꢀ2.56 (m, 12H,
CH3), 1.92ꢀ1.87 (m, 2H), 1.67ꢀ1.59 (m, 6H), 1.34ꢀ1.24 (m, 14H).
13C NMR (CD2Cl2, 75 MHz): δ = 156.9, 156.7, 156.3, 152.8, 151.0,
150.8, 150.7, 150.6, 150.5, 147.9, 147.0, 140.4, 132.7, 128.8, 128.7, 128.6,
128.0, 127.7, 126.0, 124.9, 124.85, 124.6, 124.5, 124.2, 124.1, 123.7,
122.4, 121.5, 93.5, 87.9, 64.7, 29.5, 29.4, 29.38, 29.34, 29.2, 28.8, 28.6,
26.2, 26.0, 21.1, 21.06, 21.02, 18.0. ESI-TOF MS: m/z = 1144.33 (5%,
[MꢀPF6]+), 499.69 (100%, [Mꢀ2PF6]2+). ESI-HRMS calcd for
C54H59N9O4Ru [Mꢀ2PF6]2+: 499.6861. Found: 499.6881.
Synthesis of 3-((5-Phenyl-2-(pyridine-2-yl)thiazol-4-yl)oxy)-
propan-1-ol (7). To a solution of 5-phenyl-2-(pyridin-2-yl)thiazol-4-
ol (6, 4.0 g, 15.8 mmol) and 3-bromopropan-1-ol (2.60 g, 18.9 mmol) in
dimethyl sulfoxide (100 mL) was added fine ground K2CO3 (2.60 g,
18.9 mmol). The purple mixture was stirred for 24 h at room
temperature followed by addition of 200 mL of H2O. The solution
was extracted with CHCl3 (3 ꢁ 100 mL). The combined organic phases
were washed with H2O (3 ꢁ 100 mL) to remove the dimethyl sulfoxide,
dried over MgSO4, and concentrated in vacuo. The brown oil was
purified using gel filtration (silica, CHCl3) to yield the pure ether as a
yellow oil (3.35 g, 68%). 1H NMR (CDCl3, 250 MHz): δ = 8.59 (d, J =
4.8 Hz, 1H), 8.05 (d, J = 8.0 Hz, 1H), 7.82ꢀ7.71 (m, 3H), 7.44ꢀ7.34
Synthesis of Polymer 9c. According to the general procedure,
bis(4,40-dimethyl-2,20-bipyridine)-[11-(4-(5-((4-nitrophenyl)ethynyl)-
pyridin-2-yl)-1H-1,2,3-triazol-1-yl)undecyl methacrylate]ruthenium-
(II) hexafluorophosphate (5, 60 mg, 0.047 mmol) and 3-((5-phenyl-
2-(pyridin-2-yl)thiazol-4-yl)oxy)propyl methacrylate (8, 35 mg, 0.093 mmol)
were reacted to yield the product as red solid (42 mg, 36%). 1H NMR
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ARTICLE
(CDCl3, 300 MHz): δ = 8.58 (br), 8.30ꢀ7.90 (br), 7.85ꢀ7.30 (br),
7.20ꢀ7.0 (br), 4.51 (br), 4.15 (br), 3.55 (s), 2.50 (br), 1.92ꢀ1.70 (br),
1.34ꢀ1.24 (br), 1.0 (br), 0.83 (br). 13C NMR (CDCl3, 75 MHz): δ =
178.1, 177.8, 177.0, 151.1ꢀ150.0, 149.5, 137.0, 136.70, 136.24, 132.9,
131.6, 128.8ꢀ126.9, 124.3, 123.6, 118.9, 67.0, 54.4, 51.8, 44.9, 44.5,
29.7ꢀ28.5, 26.3, 26.0, 21.2, 18.7, 16.5.
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S
Supporting Information. SEC traces of all polymers as
b
well as UV/vis absorption and emission spectra. This material is
available free of charge via the Internet at http://pubs.acs.org.
’ AUTHOR INFORMATION
Corresponding Author
*Fax +49 (0)3641 948212, e-mail c6bera@uni-jena.de (R.B.);
Fax +49 (0)3641 206399, e-mail benjamin.dietzek@uni-jena.
de (B.D.); Fax +49 (0)3641 948202, e-mail ulrich.schubert@
uni-jena.de (U.S.S.).
(32) Manners, I. Synthetic Metal-Containing Polymers; Wiley-VCH:
Weinheim, 2004.
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Natl. Acad. Sci. U. S. A. 2000, 97, 7687–7691.
(34) Schubert, U. S.; Winter, A.; Newkome, G. R. Terpyridine-Based
Financial support of this work by the Dutch Polymer Institute
(DPI), the Fonds der Chemischen Industrie (B.D.), and the
Thuringian Ministry for Education, Science and Culture [grant
#B514-09049, Photonische Mizellen (PhotoMIC)] is kindly
acknowledged.
Materials; Wiley-VCH: Weinheim, 2011.
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