Solution self-assembly and photophysics of platinum complexes containing amphiphilic triblock random copolymers prepared by romp

Article abstract of DOI:10.1021/om900083n

Ring-opening metathesis polymerization was used to synthesize amphiphilic, phosphorescent block copolymers that self-assemble into nanometer-scaled aggregates when dissolved in a selective solvent. The triblock random copolymer architecture is built up by

Full text of DOI:10.1021/om900083n

2888
Organometallics 2009, 28, 2888–2896
Solution Self-Assembly and Photophysics of Platinum Complexes
Containing Amphiphilic Triblock Random Copolymers Prepared by
ROMP
Fabian Niedermair, Martina Sandholzer, Gabriele Kremser, and Christian Slugovc*
Institute for Chemistry and Technology of Materials (ICTM), Graz UniVersity of Technology, Graz, Austria
ReceiVed February 4, 2009
Ring-opening metathesis polymerization was used to synthesize amphiphilic, phosphorescent block
copolymers that self-assemble into nanometer-scaled aggregates when dissolved in a selective solvent.
The triblock random copolymer architecture is built up by using an oligoglycol-substituted norbornene
derivative for the hydrophilic part, 2,3-norbornenedicarboxylic acid dimethyl ester, as the first segment
of the hydrophobic part and a statistical segment made using norbornene-functionalized dyes as the second
segment of the hydrophobic part. The dyes comprise a blue fluorescent carbazole derivative serving as
the host and a red phosphorescent platinum complex serving as the guest material. Emission properties
of the amphiphilic triblock random copolymer dissolved in a nonselective solvent are exclusively
determined by the host material. Only blue emission of the carbazole-derivative can be observed. When
the polymer is dissolved in a selective solvent, polymer aggregates are formed and energy transfer occurs.
In this case, deep red phosphorescence stemming from the platinum complex used as guest component
can be observed. The amphiphilic triblock random copolymer architecture allows for the dispersion of
the platinum chromophore in a solvent in which the parent chromophore is insoluble, the realization of
a large Stokes shift of about 260 nm and significant suppression of platinum complex self-quenching,
resulting in considerable phosphorescent quantum yields. Absorbance, luminescence, quantum yield, and
lifetime measurements of this polymer and several model polymers in selective and unselective solvents
as well as in the solid state have been performed to understand the energy transfer from the host to the
guest dye in this particular system.
than the triplet energy level of the emitting dopant guest.7 To
reduce quenching effects associated with triplet-triplet an-
Introduction
Phosphorescent cyclometalated platinum(II) complexes con-
tinue to be intensively investigated due to their interesting and
useful photophysical properties.1,2 These complexes show
significant absorption bands in the visible range and have a
relatively large Stokes shift and long luminescence lifetimes.3
Application in phosphorescent devices, such as chemical sen-
sors,4 organic light emitting devices (OLEDs),5 and photovol-
taics,6 often requires the use of a host material, which has to be
selected carefully, e.g., in terms of providing efficient Fo¨rster
energy transfer to name one important prerequisite. The crucial
issue is that the triplet energy level of the host must be higher
nihilation, the phosphorescent dyes are normally dispersed in a
conductive polymer host. However, these blend systems are
prone to undergo phase separation.8 Covalent incorporation of
the guest into the host-polymer, by contrast, prevents phase
separation, leads to higher efficiencies, and constitutes a further
step toward an easy and reliable processing of the material.9,10
Covalent attachment to amphiphilic block copolymers that self-
assemble on the nanoscale, in particular, opens up a pathway
toward the design of functional materials with complex struc-
(7) Xia, H.; Li, M.; Lu, D.; Zhang, C.; Xie, W.; Liu, X.; Yang, B.; Ma,
Y. AdV. Funct. Mater. 2007, 17, 1757–1764.
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2004, 16, 537–541. (b) Ding, J.; Gao, J.; Cheng, Y.; Xie, Z.; Wang, L.;
Ma, D.; Jing, X.; Wang, F. AdV. Funct. Mater. 2006, 16, 575–581. (c)
McGehee, M. D.; Bergstedt, T.; Zhang, C.; Saab, A. P.; O’Regan, M. B.;
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1354. (d) Tung, Y. L.; Lee, S. W.; Chi, Y.; Chen, L. S.; Shun, C. F.; Wu,
F. I.; Carty, A. J.; Chou, P. T.; Peng, S. M.; Lee, G. H. AdV. Mater. 2005,
17, 1059–1064. (e) Lamansky, S.; Djurovich, P.; Murphy, D.; Abdel-Razzaq,
F.; Lee, H. E.; Adachi, C.; Burrows, P. E.; Forrest, S. R.; Thompson, M. E.
J. Am. Chem. Soc. 2001, 123, 4304–4312. (f) Kwong, R. C.; Sibley, S.;
Dubovoy, T.; Baldo, M.; Forrest, S. R.; Thompson, M. E. Chem. Mater.
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M.; Feng, J.; Cheng, G.; Wu, Z. J.; Ma, Y. G.; Liu, S. Y.; Sheng, J. C.;
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* Corresponding author. Fax: +43 316 873 8951. E-mail: slugovc@
tugraz.at.
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10.1021/om900083n CCC: $40.75
2009 American Chemical Society
Publication on Web 04/17/2009

Pt Complexes with Amphiphilic Random Copolymers
Organometallics, Vol. 28, No. 9, 2009 2889
tures and novel properties. The self-assembly behavior of block
copolymers has, therefore, become of increasing interest within
various sub-areas of materials research,11 such as electronic
applications,12 drug delivery,13 and separation and dispersant
technologies.14,15 Compared to small-molecule amphiphilic
micelles, block copolymer assemblies show increased stability16
and high guest encapsulation ability.17 The major advantage of
block copolymers, however, is that one can adjust not only the
chemical nature of the blocks but also the molecular charac-
teristics (composition, molecular weight, functional groups) and
consequently the size and structure of the aggregates.17,18
Attachment of metal complexes to amphiphilic block copoly-
mers allows the hybridization of the intrinsic properties of the
metal complex (e.g., photophysical properties) with the self-
assembly behavior of the block copolymer, taking a further step
toward the design of “smart materials”.19,20 Herein, the prepara-
tion, characterization, and self-organization of amphiphilic
triblock random copolymers containing a blue fluorescent host
and a red phosphorescent guest are described. As the polym-
erization method, ring-opening metathesis polymerization (ROMP)
was used because highly functional group tolerant initiators
enable a straightforward preparation of well-defined, function-
alized polymers.21 Moreover, ROMP allows for the preparation
of block copolymers via “living polymerization”.22,25 The
decisive influence of the polymer architecture on the function,
i.e., (a) the dispersion of the platinum chromophore in a solvent
in which the parent chromophore is insoluble, (b) the realization
of a large Stokes shift of about 260 nm, and (c) the significant
suppression of platinum complex aggregation and, thus, con-
siderable gain of phosphorescent quantum yield, will be
discussed in detail.
Results and Discussion
Synthesis. The polymerizable Pt(II) complex 3 was prepared
in a three-step procedure. First, the precursor κ2(N,C2)-(11-(2-
phenylpyridine-3-yloxy)undecan-1-ol)-κ1(N)-(11-(2-phenylpy-
ridine-3-yloxy)undecan-1-ol)chloroplatinum(II) (2a) was pre-
pared similar to a literature procedure23 using 11-(2-phenylpyridin-
3-yloxy)undecan-1-ol (1c) (for synthesis and preparation of 11-
(2-phenylpyridine-3-yloxy)undecan-1-ol see the Supporting
Information) and K2PtCl4 as the starting materials. 2a was
subsequently reacted with 5-formyl-8-hydroxyquinoline24 in
degassed CH2Cl2/EtOH and K2CO3 at room temperature using
a method similar to that described in the work of Brooks et
al.23 Purification was accomplished by flash chromatography
on silica (CH2Cl2, then acetone; Rf ) 0.74), yielding 2b as an
orange solid (39%), which, in the third step, was esterified with
in situ generated norbornene-2-acid chloride, yielding upon
workup the polymerizable complex 3 (cf. Scheme 1).
A similar esterification reaction of 11-[3,6-di(4-formylphe-
nyl)-9H-carbazol-9-yl]undecan-1-ol (5) was used to prepare
monomer 6. For the formation of the core unit 5, a Suzuki cross-
coupling protocol was used. Precursor 4c, which was prepared
via a hydroboration reaction of 3,6-dibromo-9-(undec-10-enyl)-
9H-carbazole (4b), was reacted with 4-formylphenylboronic acid
and Na2CO3 in a mixture of degassed toluene/EtOH/H2O in the
presence of the catalyst Pd(PPh3)4 at 90 °C for 20 h. The raw
product was purified by flash chromatography on silica (Cy/
EA ) 5:1, Rf ) 0.52 in Cy/EA ) 1:1), yielding a yellow solid
(29%) (cf. Scheme 2). Monomers 3 and 6 were isolated and
used as a mixture of their corresponding endo and exo isomers.
Monomers were characterized by NMR and IR spectroscopy
and elemental analysis (cf. Supporting Information).
(11) (a) Matyjazewski, K.; Gnanou, Y.; Leibler, L. Macromolecular
Engineering. Precise Synthesis, Materials Properties, Applications, Vol.
4; Wiley-VCH Verlag GmbH & Co., KGaA: Weinheim, 2007. (b) Lazzari,
M.; Liu, G.; Lecommandoux, S. Block Copolymers in Nanoscience; Wiley-
VCH Verlag GmbH & Co., KGaA: Weinheim, 2006.
(12) Edrington, A. C.; Urbas, A. M.; DeRege, P.; Chen, S.; Swager,
T. M. AdV. Mater. 2001, 13, 421–425.
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Colloids Surf. B 1999, 16, 3–27. (b) Kwon, G. S.; Okano, T. Pharm. Res.
1999, 16, 597–600. (c) Torchilin, V. P. Expert Opin. Ther. Pat. 2005, 15,
63–75. (d) Nishiyama, N.; Kataoka, K. AdV. Polym. Sci. 2006, 193, 67–
101.
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Biomacromolecules 2005, 6, 1280–1288. (b) Shin, H.-I.; Min, B. G.; Jeong,
W.; Park, C. Macromol. Rapid Commun. 2005, 26, 1451–1457. (c) Moad,
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Angew. Chem. Int. Ed. 2000, 39, 3310-3312.
The amphiphilic triblock random copolymers poly b-1, poly
b-2, and poly b-3 were synthesized using a modified “second-
generation Grubbs” initiator (G) by stepwise polymerization of
each block (Scheme 3).25 As building blocks, norbornene
derivatives with an ester anchor group were chosen. The anchor
group significantly influences the initation and propagation rates
and consequently the polydispersity, as well as the molecular
weight of the polymers.26 Therefore, only monomers with the
same anchor group were used.
(17) Jenehke, S. A.; Chen, X. L. Science 1998, 279, 1903–1907.
(18) (a) Choucair, A.; Eisenberg, A. Eur. Phys. J. E 2003, 10, 37–44.
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(19) Fustin, C.-A.; Guillet, P.; Schubert, U. S.; Gohy, J. -F. AdV. Mater.
2007, 19, 1665–1673.
(20) Wong, W.-Y. Dalton Trans. 2007, 4495–4510.
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GmbH & Co. KGaA: Weinheim, 2003. (b) Buchmeiser, M. R. Chem. ReV.
2000, 100, 1565–1604. (c) Slugovc, C. Macromol. Rapid Commun. 2004,
25, 1283–1297. (d) Bielawski, C. W.; Grubbs, R. H. Prog. Polym. Sci. 2007,
32, 1–29. (e) Yang, S. K.; Weck, M. Macromolecules 2008, 41, 346–351.
(f) Kimyonok, A.; Weck, M. Macromol. Rapid Commun. 2007, 28, 152–
157. (g) South, C. R.; Higley, M. N.; Leung, K. C.-F.; Lanari, D.; Nelson,
A.; Grubbs, R. H.; Stoddart, J. F.; Weck, M. Chem.sEur. J. 2006, 12,
3789–3797. (h) Carlise, J. R.; Wang, X.-Y.; Weck, M. Macromolecules
2005, 38, 9000–9008. (i) Mayers, A.; Kimyonok, A.; Weck, M. Macro-
molecules 2005, 38, 8671–8678. (j) Sandholzer, M.; Lex, A.; Trimmel, G.;
Saf, R.; Stelzer, F.; Slugovc, C. J. Polym. Sci., Part A: Polym. Chem. 2007,
45, 1336–1348. (k) Noormofidi, N.; Slugovc, C. Macromol. Chem. Phys.
2007, 208, 1093–1100. (l) Sandholzer, M.; Bichler, S.; Stelzer, F.; Slugovc,
C. J. Polym. Sci., Part A: Polym. Chem. 2008, 46, 2402–2413. (m)
Sandholzer, M.; Schuster, M.; Varga, F.; Liska, R.; Slugovc, C. J. Polym.
Sci., Part A: Polym. Chem. 2008, 46, 3648–3661. (n) Burtscher, D.; Lexer,
C.; Mereiter, K.; Winde, R.; Karch, R.; Slugovc, C. J. Polym. Sci., Part A:
Polym. Chem. 2008, 46, 4630–4635. (o) Lexer, C.; Saf, R.; Slugovc, C. J.
Polym. Sci., Part A: Polym. Chem. 2009, 47, 299–305.
Compound 7 was chosen as the hydrophobic monomer, while
endo,exo-bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid bis[2-
[2-(2-ethoxyethoxy]ethoxy]ethyl] ester (8)27 was used for the
preparation of the hydrophilic block. An overall polymer length
of 300 repeating units was targeted, while the molar ratio of
the hydrophobic block to the hydrophilic block was kept
constant at 2:1. Finally, a third segment was copolymerized
using a mixture of 3 equiv of 3 and 17 equiv of 6. Thus, the
(23) Brooks, J.; Babayan, Y.; Lamansky, S.; Djurovich, P. I.; Tsyba, I.;
Bau, R.; Thompson, M. E. Inorg. Chem. 2002, 41, 3055–3066.
(24) Clemo, G. R.; Howe, R. J. Chem. Soc. Abstr. 1955, 3552–3553.
(25) (a) Slugovc, C.; Riegler, S.; Hayn, G.; Saf, R.; Stelzer, F. Macromol.
Rapid Commun. 2003, 24, 435–439. (b) Riegler, S.; Demel, S.; Trimmel,
G.; Slugovc, C.; Stelzer, F. J. Mol.Catal. A 2006, 257, 53–58.
(26) Slugovc, C.; Demel, S.; Riegler, S.; Hobisch, J.; Stelzer, F.
Macromol. Rapid Commun. 2004, 25, 475–480.
(22) Lynn, D. M.; Kanaoka, S.; Grubbs, R. H. J. Am. Chem. Soc. 1996,
118, 784–790.
(27) Sandholzer, M.; Fritz-Popovski, G.; Slugovc, C. J. Polym. Sci., Part
A: Polym. Chem. 2008, 46, 401–413.

2890 Organometallics, Vol. 28, No. 9, 2009
Scheme 1. Synthesis of the Polymerizable Pt Complex 3a
Niedermair et al.
a
Reagents and conditions: (a) 11-bromoundecan-1-ol, K2CO3/NaOH ) 1:1, 2-butanone, 90 °C, 24 h (75%); (b) phenylboronic acid, Pd(PPh3)4,
K2CO3, toluene/EtOH/H2O ) 1:1:1, 95 °C, 24 h (94%); (c) K2PtCl4, ethoxyethanol/H2O ) 3:1, 80 °C, 21 h (46%); (d) 5-formyl-8-hydroxyquinoline,
CH2Cl2/EtOH ) 1:1, K2CO3, RT (73%); (e) cyclopentadiene, acryloyl chloride, CH2Cl2, RT, 12 h, then pyridine, DMAP, CH2Cl2, RT (51%).
Scheme 2. Synthesis of the Polymerizable Carbazole Host Material 6a
a
Reagents and conditions: (a) 11-bromoundec-1-ene, NaOH, DMSO/H2O, 70 °C, 20 h (89%); (b) BH3 · THF, THF, RT, 12 h (82%); (c)
4-formylphenylboronic acid, Na2CO3, Pd(PPh3)4, toluene/EtOH/H2O, 90 °C, 20 h (29%); (d) cyclopentadiene, acryloyl chloride, CH2Cl2, RT, 12 h,
then DMAP, pyridine, 0 °C, 30 min, RT, 24 h (47%).
third segment exhibits a random distribution of repeating units
comprising a platinum complex and a carbazole unit. Using the
reaction conditions described in the caption of Scheme 3
followed by repeated precipitation of CH2Cl2 solutions from
n-pentane gave poly b-1 in 63% yield.
from the results obtained by TLC control of the reaction
progress. Gel permeation chromatography (GPC) of poly b-1
in THF relative to polystyrene standards revealed a polydis-
persity index (PDI) of 1.53 and a number average molecular
weight (Mn) of 75 100 g/mol. Corresponding data for poly b-2
and poly b-3 were similar (poly b-2: PDI ) 1.23, Mn ) 61100
g/mol and poly b-3: PDI ) 1.24, Mn ) 70200 g/mol) and
underline the reliability of the polymerization method.
Similarly, two reference triblock random copolymers poly
b-2 and poly b-3 were prepared by varying the last randomly
composed segment (cf. Figure 1). In the case of poly b-2, the
last segment was built up using 17 equiv of 7 and 3 equiv of 3;
that is, no carbazole-bearing monomer was used. In the case of
poly b-3, the platinum-bearing monomer was replaced by
monomer 6 (3 equiv). Both polymers were isolated in 75% yield.
Aggregate Preparation and Characterization. As reported
previously,27 MeOH is a selective solvent for the oligoglycol-
functionalized segment of the triblock random copolymer and
therefore suited for promoting the self-assembly of the material
in solution. A dispersion of polymer aggregates was obtained
by simply stirring 0.1 wt % of the corresponding polymer in
methanol under ambient conditions for 18 h. The formation of
aggregates in MeOH was ensured by NMR spectroscopy and
dynamic light scattering (DLS). 1H NMR spectra were recorded
in CD3OD and compared to those obtained from CDCl3
solutions. Representative results are discussed for poly b-1
(Figure 2). Whereas characteristic carbazole signals could be
observed in the spectrum recorded in CDCl3, these signals were
not detected when CD3OD was used as the solvent. These results
suggest that the segment comprising both dyes forms the cores
1
The block polymer composition was verified by H NMR
spectroscopy in a nonselective solvent (CDCl3) via integration
of the multiplet at 5.58-5.10 ppm, representing the polymer
double bond and the triplet at 1.20 ppm, representing the methyl
groups of monomer 8. By evaluation of the integrals an amount
of about 33% ( 3% of 8 was determined, which was consistent
for poly b-1, poly b-2, and poly b-3. Integrals of the peaks at
10.01, 8.37, 7.91-7.82, 7.46, and 7.05 ppm characteristic for
the carbazole moiety confirmed the successful incorporation of
6. NMR spectroscopic evidence for the incorporation of 3 could
not be gained, due to the minute ratio (<1 mol %) of 3.
However, complete polymerization of 3 and 6 can be assumed

Pt Complexes with Amphiphilic Random Copolymers
Organometallics, Vol. 28, No. 9, 2009 2891
Scheme 3. Synthesis of the Pt-Containing Amphiphilic Block
Copolymer poly b-1 (molar equiv: 8:G:7:3:6 ) 100:1:200:3:17)a
Figure 1. Depiction of poly b-2 (molar equiv: 8:G:7:3:7 ) 100:
1:200:3:17) and poly b-3 (molar equiv: 8:G:7:6:7 ) 100:1:200:3:
17).
a
Reagents and conditions: (a) 8 and G in dry and degassed CH2Cl2,
RT, 2 h, then addition of 7, RT, 1 h, then addition of a mixture of 3
and 6, RT, 1 h, then addition of ethyl vinyl ether (excess), RT, 1 h
(63%).
of the aggregates.28 Further evidence for this hypothesis was
retrieved by evaluation of the integral ratio for the peaks
representing the polymer backbone’s double bonds (signal
ranging from 5.51 to 5.19 ppm) and the signal assigned to the
COOCH2 group (peaking at 4.19 ppm). In CDCl3 this ratio was
determined to be 2:1.2, while in CD3OD a ratio of 2:4 was
revealed. The ratio obtained from the CD3OD spectra corre-
sponds to the theoretically expected value for a homopolymer
of monomer 8 and constitutes a strong indication for the
presence of aggregates with a shell composed of the oligoglycol-
bearing segment of the triblock random copolymer.
The block copolymer aggregates were characterized by
dynamic light scattering using a Malvern ZetaSizer NanoZS
equipped with a 633 nm laser. Measurements were performed
at 20 °C. A summary of the particle sizes in methanol is given
in Table 1. All triblock random copolymers under investigation
formed aggregates in MeOH with diameters ranging from 81
to 88 nm. Monomodal size distributions with narrow PDIDLS
values (0.03-0.09) were obtained in all cases.
1
Figure 2. H NMR spectra of poly b-1 in CD3OD and CDCl3.
Table 1. Aggregate Sizes of Triblock Random Copolymers in
Methanol Determined by DLS; Mn’s as well as PDIs Determined
from GPC Measurements
b
polymer
diametera [nm]
PDIDLS
Mn [g/M]
PDIb
poly b-1
poly b-2
poly b-3
88
81
81
0.09
0.03
0.06
75 100
61 100
70 200
1.53
1.23
1.24
a Determined by dynamic light scattering at 20 °C; 0.1 wt % in
methanol. b Determined by GPC with THF as the solvent; calibrated
against polystyrene standards.
Photophysical Properties. Optical properties of the am-
phiphilic triblock random copolymers poly b-1, poly b-2, and
poly b-3 were investigated by UV/vis absorption and photolu-
minescence spectroscopy; excitation spectra complement the
results. Emphasis is given to the comparison of the photophysi-
cal properties in a selective solvent, i.e., MeOH and a nonselec-
tive solvent, namely, CHCl3. Photophysical data of monomers
3 and 6 were established for comparison and completeness.
Furthermore, data from thin films of the materials and measure-
(28) Bertin, P. A.; Watson, K. J.; Nguyen, S. T. Macromolecules 2004,
37, 8364–8372.

2892 Organometallics, Vol. 28, No. 9, 2009
Niedermair et al.
Figure 3. Absorption and emission spectra of 3, 6, and poly b-1 measured in CHCl3 at RT. Absorption: 9 ) 3, [3] ) 2.1 × 10-5 M (λmax
) 468 nm); 2 ) 6, [6] ) 2.2 × 10-5 M (λmax ) 361 nm); b ) poly b-1, [poly b-1] ) 1.4 × 10-1 mg/mL (λmax ) 361 nm). Fluorescence:
0 ) 3, [3] ) 4.9 × 10-6 M (λex ) 467 nm); ∆ ) 6, [6] ) 3.9 × 10-8 M (λex ) 360 nm); O ) poly b-1, [poly b-1] ) 4.5 × 10-2 mg/mL
(λex ) 360 nm).
ments of quantum yields and luminescence lifetime of the
phosphorescent dyes under various conditions will be presented.
The absorption spectrum of complex 3 measured in diluted
solution of CHCl3 ([3] ) 2.1 × 10-5 M) at room temperature
under ambient conditions showed a significant absorption band
in the visible region. This lowest energy absorption band is
centered at 468 nm, with an extinction coefficient of 13.1 ×
103 cm-1 M-1 and can be assigned to an intraligand charge
transfer transition (ILCT) of the coordinated quinolinolate
ligand.3 Complex 3 emitted red light with its maximum at 621
nm (λex ) 468 nm) in CHCl3 solution. The absorption feature
of 3 peaking at 468 nm matches favorably with the emission at
453 nm (λex ) 360 nm) of monomer 6, which exhibits its lowest
energy absorption maximum at 361 nm. Thus, efficient energy
transfer from the host (carbazole derivative 6) to the guest
(platinum complex 3) can be anticipated (cf. Figure 3). It is
worth mentioning that several similar carbazole-based dyes
bearing different substituents at the 3- and 6-positions are not
suited as host materials because of less favorable photophysical
properties.7,29,30
emission (weak and broad emission band from 440 to 520 nm)
was negligible (cf. Figure 4). In addition, the corresponding
excitation spectrum recorded in methanol (for an emission
wavelength (λexc) of 625 nm) supports the feasibility of the
energy transfer. Two prominent peaks were observed. The more
dominant excitation band at 370 nm characterizes the carbazole
moiety; the weaker band at 480 nm belongs to the platinum
dye (cf. Supporting Information).
DLS measurements of the diluted MeOH samples, previously
used for spectroscopic measurements, confirmed the presence
of block copolymer aggregates. Particle sizes nicely resembled
those obtained from solutions of higher concentration (cf. Table
1). The occurrence of energy transfer in MeOH but not in CHCl3
might be simply explained by the fact that in the aggregates a
“solid state like” environment is created31 and the distance
between host and guest is reduced.32 Maximized spectral overlap
between the donor emission and the acceptor absorption,
improved orientation, and a shortened distance between the
donor and the acceptor should lead to more efficient FRET.33
To support this hypothesis, a thin film of poly b-1 was prepared
by drop-casting a methanolic solution onto glass and examining
its photophysical properties. Surprisingly, considerable host
emission peaking at 437 nm in addition to the expected guest
emission peaking at 625 nm was observed under these conditions
(cf. Figure 4). This observation might be explained by either
an increased luminescence quantum yield of the host material
in the solid state or a less efficient energy transfer in the film.
The latter might be ascribed to the tendency of square-planar
platinum chromophores to form aggregates and excimers in
The block copolymer poly b-1 exhibited the characteristic
carbazole absorption bands at 246, 315, and 361 nm, as well as
a weak absorption band at 467 nm, attributed to the incorporated
platinum chromophore. The emission maximum of poly b-1 in
CHCl3 with λmax ) 450 nm (λex ) 360 nm) is very similar to
the emission maximum of the monomer 6 in CHCl3 (λmax
)
453 nm); thus no energy transfer to the phosphorescent platinum
dye occurred under these conditions. In sharp contrast, a solution
of aggregated poly b-1 in methanol exhibited bright red
luminescence with its emission maximum peaking at 625 nm
(λex ) 370 nm). In this case, efficient energy transfer from the
carbazole host to the platinum guest occurred, whereas host
(31) Riess, G. Prog. Polym. Sci. 2003, 28, 1107–1170, and references
therein.
(32) (a) Foerster, T. Ann. Phys. 1948, 437, 55–75. (b) May, V.; Kuehn,
O. Charge and Energy Transfer Dynamics in Molecular Systems, 2nd ed.;
Wiley-VCH, 2004. (c) Scholes, G. D.; Curutchet, C.; Mennucci, B.; Cammi,
R.; Tomasi, J. J. Phys. Chem. B 2007, 111, 6978–6982.
(33) Lakowicz, J. R. In Principles of Fluorescence Spectroscopy; Kluwer
Academic/Plenum Publisher: New York, 1999.
(29) Kremser, G.; Hofmann, O. T.; Sax, S.; Kappaun, S.; List, E. J. W.;
Zojer, E.; Slugovc, C. Monatsh. Chem. 2008, 139, 223–231.
(30) (a) Adamovich, V.; Brooks, J.; Tamayo, A.; Alexander, A. M.;
Djurovich, P. I.; D’Andrade, B. W.; Adachi, C.; Forrest, S. R.; Thompson,
M. E. New J. Chem. 2002, 26, 1171–1178. (b) D’Andrade, B. W.; Brooks,
J.; Adamovich, V.; Thompson, M. E.; Forrest, S. R. AdV. Mater. 2002, 14,
1032–1036.
(34) Farley, S. J.; Rochester, D. L.; Thompson, A. L.; Howard, J. A. K.;
Williams, J. A. G. Inorg. Chem. 2005, 44, 9690–9709.

Pt Complexes with Amphiphilic Random Copolymers
Organometallics, Vol. 28, No. 9, 2009 2893
Figure 4. Absorption (b), excitation (9), and emission (0) spectra of poly b-1 measured in MeOH and thin film excitation (2) and
emission (∆) spectra of a drop-casted film on glass of poly b-1 from MeOH (2 mg mL-1 copolymer) (λex ) 370 nm, λexc ) 625 nm).
Absorption in MeOH: [poly b-1] ) 1.0 × 10-1 mg/mL. Excitation in MeOH: [poly b-1] ) 3.4 × 10-2 mg/mL (λexc ) 625 nm). Emission
in MeOH: [poly b-1] ) 3.4 × 10-2 mg/mL (λex ) 370 nm).
Table 2. PLQY and Lifetimes of poly b-1, poly b-2, and the
concentrated solutions as well as in the solid state.2,34-36 Since
Platinum Monomer 3
the aggregation of the platinum dyes can also affect the energies
conc of 3
[mg/mL]
τair
τN2
PLQY air PLQY N2
of the acceptor states, a different spectral overlap with the
corresponding host system can be anticipated. The latter includes
polymer
[µs]a
[µs]a
[%]
[%]
poly b-1c
3.2 × 10-3 11 ( 1 14 ( 1
3.3 ( 0.5
4.4 ( 0.5
2
interactions that involve overlap of the dz orbitals, which
b
b
poly b-2c
3.4 × 10-3
2 ( 1
6 ( 1
-
-
poly b-2d 7.2 × 10-4
5 ( 2 19 ( 2
3 ( 2 30 ( 2
0.2 ( 0.2
0.2 ( 0.2
1.1 ( 0.5
7.6 ( 1
frequently lead to dσ*(Pt2)fπ*(ligand) (metal-metal to ligand
charge transfer, MMLCT) excited states These low-energy
excited states result in more red-shifted spectra compared to
mononuclear absorption.37
Aggregate formation in this particular system was studied
using model polymer poly b-2 (cf. Figure 1). The emission
spectrum of poly b-2 in CHCl3 exhibited the same emission
maximum (623 nm) as the platinum monomer 3 in CHCl3 (621
nm). By contrast, the emission spectrum of poly b-2 in methanol
showed only a very weak emission with three major emission
bands at 586, 631, and 708 nm, which is a strong indication for
aggregation of the platinum dyes.34,35
Aggregation was further studied by photoluminescence
quantum yield (PLQY) and lifetime measurements (τ) in
solution. Quantum yields of the corresponding compounds were
measured in aerated as well as degassed CHCl3 and MeOH
solutions using 4-dicyanomethylene-2-methyl-6-(4-(dimethyl-
amino)styryl)-4H-pyran (DCM) as the standard.38 Quenching
by oxygen was determined by measuring the luminescence
lifetime in aerated and degassed solutions of CHCl3 and MeOH
using a frequency-based method.39 Results are presented in
Table 2.
3d
1.1 × 10-3
a Apparent lifetimes measured at a modulation frequency of 5.5 kHz
(for PLQY measurements λex ) 470 nm was applied). b PLQY could not
be determined (broad excimer emission). c Measured in MeOH.
d Measured in CHCl3.
1% (1.1 × 10-2 mg/mL) to 7.6 ( 1% (1.1 × 10-3 mg/mL).
The increase of quantum yields at higher dilutions indicates self-
quenching at higher concentrations.3,40 Luminescence lifetime
of 3 in CHCl3 ranged from 1 ( 1 to 3 ( 1 µs in aerated solutions
and from 23 ( 1 µs to 30 ( 1 µs in degassed solutions. The
PLQY of the triblock random copolymer poly b-1 (2.3 wt %
of 3) was determined to be 4.4 ( 0.5% in degassed MeOH,
indicating some self-quenching of the platinum dyes in the core
of the aggregate. Self-quenching by Pt-Pt interactions can be
further confirmed by shorter lifetimes of the dye in poly b-1
compared to 3, namely, 14 ( 1 µs in degassed solution (Table
2). However, aggregation in poly b-2 was considerably more
pronounced, as evidenced by particularly low PLQYs in MeOH
and low PLQYs in CHCl3, not exceeding 1.1 ( 0.5 µs in the
latter case. It is to note that the influence of the solvent (MeOH
vs CHCl3) on the values for PLQY and lifetimes cannot be
retrieved directly from these experiments since 3 is not soluble
in MeOH. However, these results indicate a significant sup-
pression of self-quenching of the platinum chromophores when
copolymerized with the carbazole dye like in poly b-1.
PLQY in degassed CHCl3 solution of the platinum monomer
3 showed slight concentration dependence, ranging from 5.2 (
(35) Ionkin, A. S.; Marshall, W. J.; Wang, Y. Organometallics 2005,
24, 619–627.
(36) Williams, J. A. G.; Develay, S.; Rochester, D. L.; Murphy, L.
Coord. Chem. ReV. 2008, 252, 2596–2611.
(37) Ma, B.; Li, J.; Djurovich, P. I.; Yousufuddin, M.; Bau, R.;
Thompson, M. E. J. Am. Chem. Soc. 2005, 127, 28–29.
(38) Bondarev, S. L.; Knyukshto, V. N.; Stepuro, V. I.; Stupak, A. P.;
Turban, A. A. J. Appl. Spec. 2004, 71, 194–201.
(39) Huber, C.; Klimant, I.; Krause, C.; Werner, T.; Mayr, T.; Wolfbeis,
O. S. Fresenius J. Anal. Chem. 2000, 368, 196–202.
To further investigate the characteristics of the energy transfer
in the host/guest system, a blend of poly b-2 and poly b-3 was
prepared, using the same molar ratio (3:6 ) 3:17) as in the
(40) Lai, S.-W.; Chan, M. C. W.; Cheung, T.-C.; Peng, S.-M.; Che,
C.-M. Inorg. Chem. 1999, 38, 4046–4055.

2894 Organometallics, Vol. 28, No. 9, 2009
Niedermair et al.
block random copolymer poly b-1. poly b-2 and poly b-3 were
mixed in CHCl3, and the solvent was evaporated. The dried
residue was dispersed in methanol (0.1 wt %), resulting in the
formation of aggregates with a diameter of 90 nm (PDI ) 0.10).
Luminescence measurements revealed an emission maximum
of 475 nm in MeOH (λex ) 360 nm), which is comparable to
the emission maximum of 483 nm for poly b-3 (λex ) 360 nm)
(Vide infra). Excitation of poly b-2/poly b-3 in methanol at 460
nm revealed weak emission with maxima at 577 and 680 nm,
which are comparable to the emission maxima of poly b-2 in
methanol (λex ) 470 nm) located at 586 and 708 nm. Although
both host and guest should be in close proximity in the core of
the aggregate, no energy transfer occurred. The same accounts
for photoluminescence thin film spectra of the polymer blend
poly b-2/poly b-3, which were obtained by drop-casting either
a MeOH solution or a CHCl3 solution, containing 1 mg mL-1
of the polymer blend, onto a glass slide. Excitation of the
obtained film (either from MeOH or from CHCl3) at 360 nm
revealed mainly blue emission at 434 nm and almost no red
emission at 615 nm (see Supporting Information).
According to these results, it is essential to copolymerize host
and guest in order to provide an efficient energy transfer when
exciting the material at 360 nm. Simple blending of a carbazole
host bearing copolymer with a platinum guest bearing copoly-
mer, on the contrary, does not result in the desired energy
transfer. Thus, a critical distance of platinum guest and carbazole
host has to be maintained to guarantee efficient energy transfer.
According to Fo¨rster theory, an estimated radius for which 50%
of the populated excited states of the host are transferred to the
guest is about 4 nm.32,33 In the case of poly b-1, the highest
possible intramacromolecular distance of two chromophores was
estimated using an MM2 optimized model to be about 5 nm.
Thus, at least some energy transfer should even occur in a
solution of poly b-1 in a nonselective solvent. This inconsistency
and all observations reported above might be best explained by
the formation of carbazole-platinum complex aggregates under
solid state conditions (like in thin films or micelle cores) and
eventually exciplex emission from these aggregates. In a good
solvent for the carbazole moiety, these aggregates are broken and
platinum complex self-aggregation occurs. The resulting platinum
complex excimer emission is very weak and hardly observable.
Although no direct spectroscopic evidence for this hypothesis could
be retrieved, further experiments support this theory.
Figure 5. Emission spectra of poly b-1 (0) (λex ) 370 nm) and
poly b-2 (∆) (λex ) 470 nm) measured in degassed MeOH at room
temperature ([poly b-1] ) 1.0 × 10-1 mg/mL, [poly b-2] ) 1.4 ×
10-1 mg/mL). The luminescence intensity of the broad excimer
emission of poly b-2 in MeOH (O) is about 20 times lower
compared to the luminescence intensity of poly b-1 in MeOH at
628 nm.
First, the luminescence spectrum of poly b-1 in CHCl3 at 77
K exhibited the blue emission of the host and the red emission
of the guest complex with its maximum at 606 nm (λex ) 370
nm, cf. Supporting Information). The blue shift of the emission
maximum of the platinum dye can be attributed to rigidochromic
effects.41 More importantly, the experiment clearly reveals the
feasibility of energy transfer in solution. Presumably, thermal
deactivation of the platinum dye is the reason for the absence
of platinum luminescence at room temperature in nonselective
solvents.
Figure 6. Emission spectra of poly b-1 measured in MeOH (0)
([poly b-1] ) 1.0 × 10-1 mg/mL) and in MeOH/CH2Cl2 ) 1:1
(∆) (λex ) 370 nm in both cases).
only CH2Cl2 but also MeOH were attained into the core, as
revealed by the red-shifted emission wavelength42 of the
solvatochromic carbazole dye (cf. Supporting Information).43The
solvatochromism of the carbazole dye shows that also the polarity
Second, the originally red-emitting MeOH dispersion of poly
b-1 (λmax ) 628 nm; [poly b-1] ) 1.0 × 10-1 mg/mL; 1 mL)
instantly turned green upon addition of CH2Cl2 (1 mL),
characterized by a broad emission band at 504 nm (Figure 6).
DLS measurements confirmed the presence of triblock random
copolymer aggregates with a diameter of about 300 nm under
these conditions. The increase of aggregate diameter can be
explained by swelling of the aggregate due to increased
incorporation of solvent into the aggregate’s core. In fact, not
(42) Investigating the solvatochromic emission behavior of the carbazole
dye in the corresponding block copolymer system of poly-b-3 revealed
different emission maxima in the solvents MeOH (λmax ) 483 nm), CHCl3
(λmax ) 451 nm), CH2Cl2 (λmax ) 459 nm), and MeOH/CH2Cl2 ) 1:1 (λmax
) 504 nm). Similar maxima were obtained for the corresponding monomer
6 (cf. Supporting Information). At present, a reasonable explanation is
missing for the surprisingly low energy of the emission maximum in MeOH/
CH2Cl2. Effects such as aggregation and excimer formation cannot be
excluded as the reason for this behavior, especially because carbazole
derivatives are well known to form excimers.43
(43) Benten, H.; Guo, J.; Ohkita, H.; Ito, S.; Yamamoto, M.; Sakumoto,
N.; Hori, K.; Tohda, Y.; Tani, K. J. Phys. Chem. B 2007, 111, 10905–
10914.
(41) Lees, A. J. Comments Inorg. Chem. 1995, 17, 319–46.

Pt Complexes with Amphiphilic Random Copolymers
Organometallics, Vol. 28, No. 9, 2009 2895
spectra were recorded at 125 MHz. Assignment of the peaks was
done by DEPT and COSY NMR spectroscopy. Solvent residual
peaks were used for referencing the NMR spectra to the corre-
sponding values given in the literature.46 FT-IR spectra were
obtained from films on KBr or NaCl windows with a Perkin-Elmer
Spectrum One and a DTGS detector. UV-visible absorption spectra
were recorded on a Cary 50 Bio UV-visible spectrophotometer;
fluorescence spectra, on a Hitachi F-7000 fluorescence spectrometer
(www.inula.at) equipped with a red-sensitive photomultiplier R 928
from Hamamatsu (www.hamamatsu.com). The emission spectra
were not corrected for the sensitivity of the PMT. Phase angle
measurements in solution were performed using the following
system. A dual-phase lock-in amplifier (DSP 830; Stanford Research
Inc.) was used for sine-wave modulation of the LED at a frequency
of 5.5 kHz and for detection. The optical system consisted of a
blue LED (λmax ) 470 nm, Roithner Lasertechnik; Vienna, Austria)
combined with a BG 12 band-pass filter (Schott; Mainz, Germany)
and a red-sensitive PMT module (H5701-02; Hamamatsu; Herr-
sching, Germany) equipped with a long-pass filter (OG590; Schott;
Mainz, Germany). The measurements were carried out in aerated
and in degassed MeOH and CHCl3 solutions. The apparent lifetimes
were determined according to the equation tan ∆φ ) 2πντ, where
∆φ indicates the phase shift, ν the modulation frequency, and τ
the luminescence lifetime. Photoluminescence (PL) quantum yields
were measured on a Hitachi F-7000 fluorescence spectrometer
(www.inula.at) equipped with a red-sensitive photomultiplier R 928
from Hamamatsu (www.hamamatsu.com) and a Perkin-Elmer
Lambda 9 UV/vis/near-infrared spectrophotometer. The emission
spectra were not corrected for the sensitivity of the PMT. Relative
quantum yield of luminescence was determined according Demas
and Crosby47 using 4-dicyanomethylene-2-methyl-6-(4-dimethyl-
aminostyryl)-4H-pyrane (Φ ) 0.57)38 as a standard. DSC measure-
ments were made with a Perkin-Elmer Pyris Diamond differential
scanning calorimeter equipped with a Perkin-Elmer CCA7 cooling
system using liquid nitrogen. A nitrogen flow of 20 mL/min and a
heating rate of 10 °C/min were used. Glass transition temperatures
(Tg) from the second heating run were read as the midpoint of
change in heat capacity. The number average molecular weights
(Mn) as well as the polydispersity index (PDI) were determined by
gel permeation chromatography with THF and CHCl3 as solvent
using the following arrangements. THF setup: Merck Hitachi L6000
pump, separation columns of Polymer Standards Service, 8 × 300
mm SDV 5 µm grade size (106, 104, and 103 Å), combined
refractive index-viscosity detector from Viscotec, Viscotec 200.
CHCl3 setup: Merck Hitachi L6000 pump, separation columns of
Polymer Standards Service, 8 × 300 mm SDV linear XL 5 µm
grade size, differential refractometer 410 detector from Waters Ltd.
Polystyrene standards purchased from Polymer Standard Service
were used for calibration of both setups. Particle sizes were
determined by DLS using the Malvern ZetaSizer NanoZS equipped
with a 633 nm laser. Measurements were performed at 20 °C.
MALDI-TOF mass spectra were recorded on a Micromass TofSpec
2E. The instrument is equipped with a nitrogen laser (337 nm
wavelength, operated at a frequency of 5 Hz) and a time lag
focusing unit. Spectra were taken in reflectron mode at an
accelerating voltage of +20 kV. Analysis of data was done with
MassLynx 3.4 (Micromass, Manchester, UK). Samples were
dissolved in THF (1 mg/mL). Dithranol or retinoic acid was used
as matrix (10 mg/mL in THF). Solutions were mixed in the cap of
a microtube in the ratio of 1 µL:10 µL. A 0.5 µL amount of the
resulting mixture was spotted onto the target and air-dried.
of the host/guest environment plays a significant role for the energy
transfer efficiency. The emission energy of the donor can be
affected by the solvent polarity, which in addition leads to a
different spectral overlap with the acceptor absorption band.
The latter experiment constitutes a proof of principle for using
such aggregates for sensing purposes and further supports the
hypothesis that carbazole-platinum complex exciplexes are
responsible for the red emission in the solid state and in polymer
aggregates.
Conclusion
In this contribution, the synthesis, characterization, and self-
assembly of amphiphilic triblock random copolymers bearing
a blue fluorescent host and a red phosphorescent guest prepared
by ROMP were presented. Emission properties of the am-
phiphilic triblock random copolymer dissolved in a nonselective
solvent are exclusively determined by the host material. Only
the blue emission of the carbazole derivative can be observed.
When the polymer is dissolved in a selective solvent, polymer
aggregates are formed and energy transfer occurs. In this case
deep red phosphorescence stemming from the platinum complex
used as guest component can be observed. The amphiphilic
triblock random copolymer architecture, thus, allows for (a) the
dispersion of the platinum chromophore in a solvent in which
the parent chromophore is insoluble, (b) the realization of a
large Stokes shift of about 260 nm, and (c) significant suppres-
sion of platinum complex self-aggregation, resulting in consid-
erable phosphorescent quantum yields. Addition of an unselec-
tive solvent to the polymer aggregates dispersed in a selective
solvent leads to the virtual shutdown of the energy transfer and
recovery of the host emission.
The effect is attributed not only to fluorescence resonance
energy transfer, i.e., change of distance of the chromophores,
but also to the formation of dye aggregates. In the absence of
a good solvent for the carbazole moiety, carbazole-platinum
complex aggregates are formed in the core of the block
copolymer micelle. These host-guest aggregates are responsible
for an efficient energy transfer, and the corresponding exciplex
type exhibits a good phosphorescence quantum yield. Further-
more, platinum complex self-aggregation is suppressed by
physical separation.44 Such undesired self-aggregation resulting
in almost nonluminescent excimers of the platinum complexes
was observed in block copolymer aggregates without copoly-
merized carbazole host.
The amphiphilic triblock random copolymers introduced
herein hold promise for applications in optical sensing. Inves-
tigations along this line are currently ongoing in our laboratories.
Experimental Section
Manipulations were performed under an inert atmosphere of
purified nitrogen or argon using Schlenk techniques and/or a
glovebox. Unless otherwise noted, materials were obtained from
commercial sources (Aldrich, Fluka, or Lancaster) and were used
without further purification. 5-Formyl-8-hydroxyquinoline24 and the
initiator (H2IMes)(pyridine)2RuCl2(dCHPh) (G)45a were prepared
1
according to the literature. H NMR spectra were recorded on a
Varian INOVA 500 MHz spectrometer at 500 MHz; 13C(1H) NMR
Synthesis of the Polymerizable Pt(II) Complex 3. To a solution
of cyclopentadiene (150 µL, 1.82 mmol) in dry CH2Cl2 (6 mL)
was added dropwise acryloyl chloride (25 µL, 0.31 mmol). The
(44) Cho, J.-Y.; Domercq, B.; Barlow, S.; Suponitsky, K. Y.; Li, J.;
Timofeeva, T. V.; Jones, S. C.; Hayden, L. E.; Kimyonok, A.; South, C. R.;
Weck, M.; Kippelen, B.; Marder, S. R. Organometallics 2007, 26, 4816–
4829.
(45) (a) Sanford, M. S.; Love, J. A.; Grubbs, R. H. Organometallics
2001, 20, 5314–5318. (b) Slugovc, C.; Demel, S.; Stelzer, F. Chem.
Commun. 2002, 2572–2573.
(46) Gottlieb, H. E.; Kotylar, V.; Nudelman, A. J. Org. Chem. 1997,
62, 7512–7515.
(47) Demas, J. N.; Crosby, G. A. J. Phys. Chem. 1971, 75, 991–1024.

2896 Organometallics, Vol. 28, No. 9, 2009
Niedermair et al.
yellow reaction mixture was stirred at room temperature. After 3 h
2 (105.9 mg; 0.150 mmol), pyridine (20 µL; 0.248 mmol), and
DMAP (1.9 mg; 0.016 mmol; 10.4 mol %) were added, and the
orange solution was stirred at room temperature. After 20 h the
solvent was removed and the orange residue was purified by column
chromatography (SiO2, eluent Cy/EA ) 2:1, Cy/EA ) 1:2 and EA;
Rf ) 0.2 in Cy/EA ) 2:1). The resulting orange solid was further
purified by washing with hot methanol and n-pentane. Yield: 20.0
mg (16%). Mixture of 67% endo- and 33% exo-derivatives; only
13C(1H) NMR (δ, 20 °C, CDCl3, 125 MHz): 191.9 (2C, CHO),
174.7 (1C, nbCOO), 147.8 (2C, ph1), 141.0 (2C, c3,6), 137.6 (1C,
nb5), 135.6 (1C, nb6), 134.4, 132.2 (4C, c8a,9a, ph4), 130.3 (4C, ph3,5),
127.4 (4C, ph2,6), 125.5 (2C, c4,5), 123.4 (2C, c4a,4b), 119.3 (2C,
c2,7), 109.4 (2C, c1,8), 64.2 (1C, undec11), 49.6 (1C, nb7), 45.6 (1C,
nb1), 43.4 (1C, undec1), 43.2, 42.4 (2C, nb2,4), 31.8 (1C, undec10),
29.6-29.0 (5C, undec4-8), 28.5 (1C, undec2), 27.2 (1C, undec3),
25.8 (2C, undec9, nb3). Characteristic exo-signals: 176.2 (1C,
nbCOO), 137.8 (2C, nb5,6). IR (film on KBr window cast from
CH2Cl2 solution, cm-1): 2925 (s), 2854 (s), 2730 (w), 1727 (m),
1698 (s), 1631 (w), 1594 (s), 1564 (w), 1518 (w), 1483 (s), 1465
(m), 1391 (w), 1353 (w), 1335 (w), 1308 (w), 1272 (w), 1215 (m),
1171 (m), 1028 (w), 905 (w), 838 (w), 804 (m), 719 (w). Anal.
Found for C33H39NO4: C,77.00; H, 7.88; N, 2.89. Calcd: C, 77.16;
H, 7.65; N, 2.73.
1
NMR data for the endo-isomer are given. H NMR (δ, 20 °C,
CDCl3, 500 MHz): 9.97 (s, 1H, CHO), 9.88 (d, 1H, 3JHH ) 8.5 Hz,
3
3
q4), 9.08 (d, 1H, JHH ) 4.9 Hz, q2), 8.94 (d, 1H, JHH ) 5.6 Hz,
py6), 8.27 (d, 1H, 3JHH ) 7.8 Hz, ph6), 7.86 (d, 1H, 3JHH ) 8.3 Hz,
q6), 7.54-7.52 (m, 1H, q3), 7.37 (d, 1H, 3JHH ) 7.3 Hz, py4), 7.28
(d, 1H, 3JHH ) 8.3 Hz, ph3), 7.19 (t, 1H, 3JHH ) 7.1 Hz, py5), 7.11
(t, 1H, JHH ) 7.6 Hz, ph4), 7.02-6.99 (m, 1H, ph5), 6.95 (d, 1H,
3
Synthesis of poly b-1. 8 (70 mg, 0.13 mmol) was dissolved in
dry, degassed CH2Cl2 (5 mL). Then, the reaction mixture was
concentrated by removing approximately 1 mL of the solvent in
Vacuo. A solution of the initiator G (1.0 mg, 0.0014 mmol) in
CH2Cl2 (0.5 mL) was added to the reaction mixture, which was
stirred at room temperature for 2 h. TLC monitoring revealed
completeness of the reaction by the absence of the monomer spot
(TLC for 8: EA; detection: 2% KMnO4 solution, Rf ) 0.5). Then,
7 (58 mg, 0.27 mmol) was added. The reaction mixture was stirred
for 1 h until the absence of the monomer was confirmed by TLC
(Cy:EA ) 5:1; detection: 2% KMnO4 solution; Rf ) 0.6). Finally,
a mixture of 3 (3.4 mg, 0.0041 mmol) and 6 (15.6 mg, 0.023 mmol)
in CH2Cl2 (0.5 mL) was added to the reaction mixture. After 1 h
the absence of both monomers was confirmed by TLC (Cy:EA )
1:1, UV/vis detection; Rf 3 ) 0.6, Rf 6 ) 0.8). The polymerization
reaction was quenched by adding ethyl vinyl ether (50 µL). After
stirring for another 15 min the reaction mixture was concentrated
by partially removing the solvent under reduced pressure. Finally,
the reaction mixture was added dropwise to stirred n-pentane (80
mL) to precipitate the polymer. Purification was done by subsequent
repeated precipitation (2 times) of CH2Cl2 solutions from n-pentane.
3JHH ) 8.3 Hz, q7), 6.19-6.18 (m, 1H, nb5), 5.93-5.91 (m, 1H,
nb6), 4.10 (t, 2H, 3JHH ) 6.6 Hz, CH2 ), 4.04-3.97 (m, 2H, CH211),
1
3.20 (bs, 1H, nb1), 2.96-2.93 (m, 1H, nb2), 2.90 (bs, 1H, nb4),
2.00-1.87 (m, 4H, nb3,7), 1.64-1.51 (m, 6H, CH22-4), 1.43-1.26
(m, 12H, CH25-10). 13C(1H) NMR (δ, 20 °C, CDCl3, 125 MHz):
190.4 (1C, CHO), 175.0 (1C, CdO), 174.0 (1C, q8), 156.1 (1C,
py3), 153.1 (1C, ph2), 148.3 (1C, py6), 147.0, 146.9 (2C, py2, q8a),
143.2 (1C, q2), 141.4 (1C, ph3), 138.5 (1C, ph1), 137.9 (1C, nb5),
137.2 (1C, py4), 132.5 (1C, nb6), 131.3 (1C, q4), 130.4 (1C, q4a),
128.60, 128.59 (2C, ph6, q6), 124.1, 123.6 (2C, q3, ph5), 121.5, 121.4
(2C, ph4, py5), 117.3 (1C, q5), 115.1 (1C, q7), 69.4 (1C, CH2 ),
1
64.5 (1C, CH211), 49.8 (1C, nb7), 45.9 (1C, nb1), 43.5, 42.7 (2C,
nb2,4), 29.7, 29.64, 29.62, 29.5, 29.4, 29.3, 29.1, 28.8, 26.3, 26.1
(10C, nb3, CH22-10). Characteristic exo-signals: 176.5 (CdO), 138.2,
135.9 (nb5,6), 64.7 (COOCH2). IR (film on NaCl window cast from
CHCl3 solution, cm-1): 3093 (w), 3060 (w), 2926 (m), 2852 (m),
2709 (w), 1729 (m), 1663 (m), 1588 (m), 1561 (m), 1506 (s), 1472
(m), 1427 (m), 1396 (w), 1365 (w), 1342 (m), 1309 (w), 1276 (m),
1245 (m), 1210 (m), 1185 (w), 1172 (w), 1147 (m), 1111 (w), 1063
(w), 1027 (w), 840 (w), 828 (w), 790 (w), 782 (w), 733 (m), 714
(w), 650 (m), 598 (w). Anal. Found for C40H44N2O5Pt: C, 57.89;
H, 5.55; N, 3.18. Calcd: C, 58.03; H, 5.36; N, 3.38. MALDI-TOF
MS: calcd 850.28; found 850.28.
1
The polymer was dried in Vacuo. Yield: 93 mg (63%). H NMR
(δ, 20 °C, CDCl3, 500 MHz): 10.01 (bs, ≈0.05H, CHO), 8.36 (bs,
≈0.09H, c4,5), 8.05-7.63 (m, ≈0.32H, ph2,3,5,6, c2,7), 7.42 (bs,
≈0.09H, c1,8), 5.57-5.10 (m, 2H, HCdCH), 4.36-4.02 (m, 1.2H,
COOCH2), 3.80-3.45 (m, 11H, OCH2, OCH3), 3.39-2.62 (m, 4H,
cp1-3,5), 1.97 (bs, 1H, cp4a), 1.47 (bs, 1H, cp4b), 1.20 (t, 2H,
OCH2CH3). FT-IR (film on NaCl, cm-1): 3621 (w), 3450 (w), 2952
(m), 2868 (m), 1732 (s), 1599 (w), 1437 (m), 1383 (w), 1349 (w),
1256 (m), 1196 (m), 1172 (s), 1113 (m), 1045 (w), 965 (w,
Synthesis of Bicyclo[2.2.1]hept-5-ene-2-carboxylicacid 11-
[3,6-Di(4-formylphenyl)carbazol-9-yl]undecyl Ester (mixture
of the endo- and exo-form) (6). Cyclopentadiene (62.2 µL, 0.76
mmol) was dissolved in dry CH2Cl2 (3 mL). Acryloyl chloride (18.4
µL, 0.23 mmol) was added dropwise to the reaction mixture, and
the solution was stirred at room temperature for 7 h. Subsequently
5 (103 mg, 0.19 mmol) and DMAP (2 mg, 0.02 mmol) were added.
The reaction mixture was cooled using an ice bath, and pyridine
(20 µL, 0.25 mmol) was added slowly. The reaction was stirred
for a further 30 min. Then, the ice bath was removed and the
mixture was stirred at room temperature for 24 h. The reaction
was quenched with H2O (2 mL). Then, the organic layer was
washed four times with saturated NaHCO3 solution (50 mL) and
four times with 5% HCl solution (50 mL). After drying the organic
layer over Na2SO4 and removing the solvent under vacuum the
residue was purified by column chromatography on silica (Cy/EA
) 15:1; Rf ) 0.86 in Cy/EA ) 1:1) to give a yellow solid (70 mg,
56%). Mixture of 78% endo- and 22% exo-derivatives; only NMR
ν
trans CdC), 842 (w), 803 (w), 742 (w, νcis CdC). GPC (in THF): Mn
75 100 g/mol; PDI 1.53. GPC (in CHCl3): Mn 92 300 g/mol, PDI
1.59. DSC: Tg not observed.
Acknowledgment. Financial support by the Austrian
Science Fund (FWF) in the framework of the Austrian Nano
Initiative (Research Project Cluster 0700, Integrated Organic
Sensor and Optoelectronics Technologies, Research Project
0701 and 0715) is gratefully acknowledged. The authors
thank Prof. Robert Saf and Karin Bartl for MALDI-TOF MS
measurements and Josefine Hobisch for GPC measurements.
Umicore’s Precious Metals Chemistry division is acknowl-
edged for a generous loan of K2PtCl4.
1
data for the endo-isomer are given. H NMR (δ, 20 °C, CDCl3,
500 MHz): 10.08 (s, 2H, CHO), 8.45 (s, 2H, c4,5), 8.01-7.99 (d,
4H, 3JHH ) 8.3 Hz, ph3,5), 7.92-7.90 (d, 4H, 3JHH ) 8.3 Hz, ph2,6),
7.82-7.80 (d, 2H, 3JHH ) 8.5 Hz, c2,7), 7.54-7.53 (d, 2H, 3JHH
)
Supporting Information Available: Detailed synthetic proce-
dures, comprehensive photophysical data (tables, absorption, emis-
sion and excitation spectra), DLS, and MALDI-TOF data. This
materialisavailablefreeofchargeviatheInternetathttp://pubs.acs.org.
8.5 Hz, c1,8), 6.19-6.17 (bs, 1H, nb5), 5.92-5.90 (bs, 1H, nb6),
4.39-4.37 (t, 2H, undec1), 4.07-3.98 (m, 2H, undec11), 3.19 (s,
1H, nb1), 2.95-2.89 (m, 2H, nb2,4), 1.96-1.86 (m, 3H, nb3, undec2),
1.61-1.50 (m, 5H, nb3, nb7, undec10), 1.37-1.25 (m, 14H,
undec3-9). Characteristic exo signals: 6.14-6.09 (m, 2H, nb5,6).
OM900083N