Intrachain electron and energy transfer in conjugated organometallic oligomers and polymers

Article abstract of DOI:10.1002/chem.200800304

The synthesis of polymers of the type (-Cz-C≡C-PtL ₂-C≡C-Cz-X-)_n along with the corresponding model compounds (Ph-PtL′₂-C≡C-Cz)₂-X-, where Cz = 3.3′-carbazole, X = nothing, Cz, or F (2,2′-fluorene), L = PBu ₃, and L′ = PEt₃ are reported. The electronic spectra (absorption, excitation, emission, and ns-transient spectra) and the photophysics of these species in 2-methyltetrahyrofuran (2MeTHF) at 298 and 77 K are presented. Evidence for singlet electron and triplet energy transfer from the Cz chromophore to the F moiety are provided and discussed in detail. The rate for electron transfer is very fast (>4×10¹¹ s ^-1), whereas that for triplet-triplet energy transfer is much slower (≈ 10³s^-1). This work represents a very rare example of studies that address electronic communication in the backbone of a conjugated organometallic polymer.

Full text of DOI:10.1002/chem.200800304

FULL PAPER
DOI: 10.1002/chem.200800304
Intrachain Electron and Energy Transfer in Conjugated Organometallic
Oligomers and Polymers
[
a, b]
[c]
[a]
[c]
Shawkat Mohammed Aly,
Cheuk-Lam Ho, Daniel Fortin, Wai-Yeung Wong,*
[a]
[
b]
Alaa S. Abd-El-Aziz, and Pierre D. Harvey*
Abstract: The synthesis of polymers of
the type (-Cz-CꢀC-PtL -CꢀC-Cz-X-)
methyltetrahyrofuran (2MeTHF) at
the F moiety are provided and dis-
298 and 77 K are presented. Evidence
for singlet electron and triplet energy
transfer from the Cz chromophore to
cussed in detail. The rate for electron
2
n
11
ꢁ1
along with the corresponding model
transfer is very fast (>4”10 s ),
compounds
where Cz=3,3’-carbazole, X=nothing,
(Ph-PtL’ -CꢀC-Cz) -X-,
whereas that for triplet–triplet energy
2
2
3
ꢁ1
transfer is much slower (ꢂ10 s ).
This work represents a very rare exam-
ple of studies that address electronic
communication in the backbone of a
conjugated organometallic polymer.
Cz, or F (2,2’-fluorene), L=PBu , and
3
Keywords: alkynes · electron trans-
fer · energy transfer · fluorene ·
metallopolymers · phosphorescence ·
platinum
L’=PEt are reported. The electronic
3
spectra (absorption, excitation, emis-
sion, and ns-transient spectra) and the
photophysics of these species in 2-
Introduction
ics. Recently, heavy-metal bis
form conjugated carbazole- and fluorene-based bis-
(ethynyl)–metal polymers (metal=platinum, gold, and mer-
cury), and their emission spectroscopy and photophysics
A
H
R
U
G
While mixed-aryl carbazole–fluorene-containing organic
dyads, polyads, oligomers, polymers- and dendrimers
ACHTREUNG
[1–5]
[6]
have been the subject of intense research in relation to
photo- and electro-luminescence with potential applications
in photonics such as photovoltaic cells and organic (OLED)
and polymer light-emitting diodes (PLED), the correspond-
ing organometallic polymers have been relatively much less
were investigated. The key feature is that incorporation of
a heavy metal in the backbone of the polymers can enhance
intersystem crossing, hence leading to an increase in the
population of the triplet states. This, in turn, leads on the
one hand to the potential application of white light emis-
sion, a current topic of intense research in OLEDs and
PLEDs, but also from a fundamental point of view, to other
channels of photo-induced electronic communication across
the backbone such as triplet–triplet energy transfer. To our
knowledge, no detailed investigation of (donor–acceptor)-
containing organometallic polymers exists to date.
[6–8]
investigated so far from a photophysical point of view.
These carbazole (Cz) and fluorene (F) moieties are prone to
[
9,10]
singlet electron transfer
fer,
and triplet–triplet energy trans-
[
9,10]
[11]
including the case in the Cz–F dyad,
and hence
bear important properties that have implications in photon-
Herein we report the synthesis of polymers of the type
[
a] S. M. Aly, D. Fortin, Prof. P. D. Harvey
DØpartement de chimie, UniversitØ de Sherbrooke
-Cz-CꢀC-PtL -CꢀC-Cz-X-) along with the corresponding
(
2
n
model compounds (Ph-PtL’ -CꢀC-Cz) -X-, in which Cz=
2
2
2
550 Boul. UniversitØ, Sherbrooke, PQ, J1K 2R1 (Canada)
3
,3’-carbazole, X=nothing, Cz, or F (2,2’-fluorene), L=
E-mail: Pierre.Harvey@USherbrooke.ca
PBu , and L’=PEt (see the structures in Scheme 1). The
[
b] S. M. Aly, Prof. A. S. Abd-El-Aziz
3
3
Department of Chemistry, University of British Columbia
Okanagan, 3333 University Way, Kelowna, BC, V1V 1V7 (Canada)
electronic spectra and the photophysics of these species in
2-methyltetrahydrofuran (2MeTHF) at 298 and 77 K are
presented. A discussion of the evidence for singlet and trip-
let energy transfer from the Cz chromophore to the F
moiety is made. The rate for electron transfer is fast (>4”
[
c] Dr. C.-L. Ho, Prof. W.-Y. Wong
Department of Chemistry and Centre for Advanced Luminescence
Materials
Hong Kong Baptist University, Waterloo Road, Hong Kong (China)
E-mail: rwywong@hkbu.edu.hk
1
1
ꢁ1
1
0 s ), whereas that for triplet–triplet energy transfer is
3
ꢁ1
much slower (ꢂ10 s ). This work represents a very rare
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.200800304.
example of detailed investigations that address electronic
Chem. Eur. J. 2008, 14, 8341 – 8352
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
8341

Scheme 1. Structures of organometallic polyynes and their model complexes.
communication in the backbone of a conjugated organome-
tallic polymer.
Scheme 3 shows the chemical structures and the synthesis
of the Pt metallopolymers P1–P3 and their model dinuclear
II
complexes M1–M3 in the present investigation. The desired
II
Pt diynes were isolated by preparative TLC plates on
Results and Discussion
silica. For P1–P3, purification was achieved by filtering the
crude sample through a short column using pure CH Cl as
2
2
Synthesis and characterization
the eluent. High purity products can be obtained by precipi-
tating the polymer solution in CH Cl from MeOH.
2
2
The precursors Ia–IIIa were synthesized by a Suzuki palladi-
All of the newmetal complexes and polymers are air-
stable and generally exhibit good solubility in chlorocarbons
such as CH Cl and CHCl . GPC analysis was used to esti-
um-catalyzed cross-coupling reaction between carbazole 3-
[11d]
boronic acid
and a formal electrophile (i.e. Cz-Br, Br-Cz-
2
2
3
Br, or Br-F-Br). When these carbazole and carbazole–fluo-
rene oligomeric chromophores were subjected to bromina-
tion, a series of newdibromide precursors wa s prepared.
The diethynyl compounds L1–L3 were prepared by applying
a palladium-catalyzed Sonogashira coupling reaction se-
quence. These were then converted to the diethynyl organic
precursors in moderate yields following a proto-desilylation
by using K CO in MeOH as the base (Scheme 2).
mate the molecular weight of each polymer (see data in the
Experimental Section). However, the data should be viewed
with caution in view of the difficulties associated with utiliz-
ing GPC for rigid-rod polymers, which have appreciable dif-
ferences in the hydrodynamic behavior from those for flexi-
ble polystyrene polymers. Hence, we would anticipate cer-
tain systematic errors in the GPC measurements. However,
the lack of discernible resonances that could be attributed
to end groups in the NMR spectra provides support for the
2
3
Scheme 2. Synthesis of diethynylated oligocarbazole and carbazole-fluorene ligands L1–L3. NBS=N-bromosuccinimide.
8342
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Chem. Eur. J. 2008, 14, 8341 – 8352

Electron and Energy Transfer in Metallopolymers
FULL PAPER
II
Scheme 3. Synthesis of Pt polyynes P1–P3 and diynes M1–M3.
viewthat there is a high degree of polymerization in most of
these polymers. The thermal properties of P1–P3 were ex-
amined by thermal gravimetric analysis (TGA) under nitro-
gen. Analysis of the TGA trace (heating rate: 208C min )
for the polymers shows that they have onset decomposition
temperatures (Tdecomp) around 3508C, indicative of their ex-
cellent thermal stability. Their degradation patterns are
quite similar and we observe sharp weight losses of 31 to
Photophysical properties
Establishment of the energy donor and acceptor: Because
of the very strong overlap between the absorption compo-
nent of the Cz and F chromophores, the establishment of
the donor and acceptor is appropriately made on the basis
of the fluorescence and phosphorescence spectra. Figure 1
shows the electronic spectra for P1, P2, P3, and M3.
ꢁ
1
3
5%, corresponding to the elimination of PBu and butyl
The emission spectrum of P1 exhibits a fluorescence band
with some vibronic structure at 382 and 400 nm (for exam-
ple), and a long tail in the red region associated with a weak
phosphorescence. This spectrum bears similarities with that
for P2 where the fluorescence vibronic structures also show
features at 380 and 400 nm. The phosphorescence portion of
the spectrum in P2 exhibits a relatively more intense lumi-
nescence with vibronic features starting at 488 nm. A com-
parison of the emission spectra of P1 and P2 allows one to
address the effect of the addition of a Cz chromophore be-
3
groups from the polymers.
These newcompounds we re characterized by analytical
1
13
31
and spectroscopic methods. The IR, NMR ( H, C, and P),
and mass spectral data shown in the Experimental Section
are in accordance with their chemical structures. The solu-
tion IR spectra of these newmetal complexes display a
single sharp n
A
C
H
T
R
E
U
N
G
(CꢀC) absorption band in the range of 2095–
ꢁ
1
2099 cm , consistent with a trans configuration of the ethy-
nylene ligands around the metal center. The absence of the
CꢀCH stretching mode of each compound at around
tween the Cz-CꢀC-PtL -CꢀC-Cz units; the phosphorescence
2
ꢁ
1
3
300 cm indicates the formation of a MꢁCꢀC bond. The
band is stronger in P2, very likely resulting from the central
Cz fragment. P3 exhibits a fluorescence (l(0–0) =404 nm) and
a phosphorescence (l(0–0) =540 nm) that differs in band
shape and position in comparison with that for P1 and P2,
demonstrating that these emissions arise from the F chromo-
NMR spectral data supported the conclusion that these
compounds have well-defined and symmetrical structures.
31
II
The P NMR spectra of the Pt complexes exhibit a single
resonance with a pair of Pt satellites, which confirms the
trans arrangement of the phosphine ligands around plati-
[14]
phore only. The Cz luminescence is not observed, which
indicates quenching of the Cz emission. Based on the posi-
tion of the 0–0 fluorescence and phosphorescence peaks
(Table 1 and Figure 1), one can readily predict the Cz and F
chromophores as both singlet and triplet energy donor and
acceptor, respectively (Figure 2). Evidence is provided
below.
1
II
num. The J values in the Pt diynes (ca. 2629–2643 Hz)
P,Pt
[12,13]
are typical of those found for related trans-PtP systems.
2
1
3
Notably, two distinct C NMR signals for the individual sp
carbons in these complexes were observed, and they are
shifted downfield with respect to the free ligands. The aro-
13
matic region of the C NMR spectra also gives more precise
information about the regiochemical structure of the main-
chain skeleton and reveals a high degree of structural regu-
larity in the polymers. As an example, only 12 well-defined
peaks appear in the aromatic region, related to the 24 aro-
matic carbon atoms of the symmetric diplatinum structure
for P1. The formulas of M1–M3 were successfully estab-
lished by the observation of intense molecular ion peaks in
the positive-ion FAB mass spectra.
M1, M2, and M3 exhibit fluorescence but not phosphores-
cence (see Table 1 and M3 in Figure 1 as an example). The
six compounds and polymers were also investigated at 77 K,
because of the convenient increase in emission intensity and
lifetimes (Table 3), giving access to the evaluation of energy
transfer rates.
Figure 3 exhibits the electronic spectra of the polymers in
2MeTHF at 77 K, which exhibit better vibronically resolved
bands. Based on the position of the 0–0 fluorescence and
Chem. Eur. J. 2008, 14, 8341 – 8352
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8343

W.-Y. Wong, P. D. Harvey et al.
Figure 1. Absorption (*), emission (black line) and excitation spectra (
gassed 2MeTHF at 298 K.
&
) of P1 (top left), P2 (top right), P3 (bottom left) and M3 (bottom right) in de-
[
a]
Table 1. UV/Vis absorption and emission data and lifetimes at 298 K in degassed 2MeTHF.
Absorption
Fluorescence
Phosphorescence
Lumophore
t
F
[ns]
P
t [ms]
l [nm]
l [nm]
l [nm]
A
H
R
U
G
A
H
R
U
G
M1
M2
M3
P1
P2
P3
226, 258, 290, 310 sh, 325
256, 320
246, 256, 292, 325, 350
256, 282, 290, 324, 340 sh
258, 320, 350 sh
350 sh, 415
370 sh, 420, 445 sh
404, 420
382, 400, 420 sh, 450 sh
380, 400, 420
404, 420 sh
–
–
–
Cz
Cz
F
Cz
Cz
F
0.160ꢃ0.050 (417 nm)
0.130ꢃ0.040 (420 nm)
0.120ꢃ0.010 (400 nm)
0.180ꢃ0.030 (415 nm)
0.070ꢃ0.010 (415 nm)
0.140ꢃ0.020 (420 nm)
–
–
–
–
–
long tail at ca. 500
488, 530
540, 565 sh
250, 294, 348
240ꢃ20 (536 nm)
[
a] sh=shoulder peak.
phosphorescence peaks, the assignment for both the singlet
and triplet energy donor (Cz) and acceptor (F) is also con-
firmed at this temperature (see Table 2). As concluded for
the 298 K data, P3 and the model compound M3 do not ex-
hibit any evidence for fluorescence of the Cz chromophore
at 77 K, indicating clear quenching. However, P3 exhibits
evidence of phosphorescence at 454 nm (narrow0–0 peak)
assigned to Cz. Unambiguous evidence for the existence of
weak phosphorescence in P3 and M3 is provided by time-re-
solved spectroscopy in the ms time scale (where fluorescence
has totally relaxed and is not present in the spectra).
Figure 4 compares the time-resolved spectra of P2 and P3,
and M2 and M3, where the Cz peak at 454 nm is observed
in both P2 and P3, and the peak at 450 nm in M2 and M3.
The presence of weak Cz phosphorescence indicates that
Figure 2. State diagram representing the Cz-CꢀC-Pt
A
T
E
N
)
-CꢀC-Cz frag-
3
2
the deactivation of the S state of Cz (by intramolecular sin-
ment with respect to F chromophore useful for the analysis of the energy
1
transfer processes in this work.
glet electron transfer to the F residue; see below) competes
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Electron and Energy Transfer in Metallopolymers
FULL PAPER
[
a]
Table 2. UV/Vis absorption and emission data and T
1
-T
1
transient lifetimes at 77 K in 2MeTHF.
Phosphorescence
(ꢃ 10%) l [nm]
Absorption
Fluorescence
F
F
F
P
Lumo-
phore
t
F
[ns]
t
P
[ms]
ttrans [ms]
[
b]
l [nm]
l [nm]
A
H
R
U
G
A
H
R
U
G
A
H
R
U
G
A
H
R
N
(lobs. [nm])
A
H
R
U
G
M1 268, 296, 310 sh, 326, 338 sh, 395 sh, 415
66 sh, 384 sh
M2 258, 274 sh, 325, 338 sh,
66 sh, 384 sh
0.0028
446, 478, 492
0.54
Cz
0.340ꢃ0.050 (410) 147ꢃ3 (446) 138
0.350ꢃ0.025 (400) 149ꢃ2 (447) 153
3
400 sh, 420
0.0021
447, 479, 491 sh
522, 565, 600 sh
455, 477, 490,
0.25
Cz
3
M3 260, 296, 325, 362, 380
399, 422, 447 0.17
0.17 (F)
0.49
Cz
F
Cz
not observed
132ꢃ6 (450)
–
0.290ꢃ0.025 (420) 175ꢃ1 (522) 193
P1 284, 292, 326, 346, 360, 370
395, 422
0.0068
0.215ꢃ0.015 (420) 61ꢃ1 (450)
0.280ꢃ0.020 (420) 66ꢃ1 (450)
74
504, 525 sh
P2 324, 348, 370
P3 288, 292, 360
395, 420
401, 423
0.0035
0.0077
458, 483, 505, 540 sh 0.47
454, 530, 570, 615 sh 0.14 (F)
Cz
Cz
F
70
–
not observed
52ꢃ2 (450)
0.290ꢃ0.030 (423) 316ꢃ23 (527) 329
[
a] sh=shoulder peak. [b] The parentheses indicate which chromophore was monitored.
Table 3. Electrochemical properties of selected ligands and complexes.
tensities. For both M3 and P3, the spectral signature is that
of the F chromophore based on the peak positions. At fur-
ther delay times (i.e. after the pulse maximum), the fluores-
cence intensities decrease and the band shape never changes
for all delay times. No sign of the Cz fluorescence was ob-
served for M3 and P3.
[
a]
[b]
[c]
Compound
E
ox [V]
EHOMO [eV]
E
g
[eV]
ELUMO [eV]
L1
L2
L3
0.61
0.54
0.65
0.41
0.39
0.36
0.38
ꢁ5.41
ꢁ5.34
ꢁ5.45
ꢁ5.21
ꢁ5.19
ꢁ5.16
ꢁ5.18
3.73
3.58
3.20
3.18
3.19
3.19
3.12
ꢁ1.68
ꢁ1.76
ꢁ2.25
ꢁ2.03
ꢁ2.00
ꢁ1.97
ꢁ2.06
[
d]
A
C
H
T
R
E
U
N
G
1 n
(Pt-(Cz) )
P1
P2
P3
Evidence for triplet energy and singlet electron transfer:
Based on the position of the 0–0 peak observed in the fluo-
rescence spectra, the upper energy donor (Cz) and lower
energy acceptor (F) were assigned. The excitation spectrum
of the fluorescence of M3 monitored at 400, 420, 450, and
ꢁ
1
+
[
a] 0.1m [Bu
4
N]PF
6
in CH
2
Cl
2
,
scan rate 100 mVs
,
versus Fc/Fc
couple. [b] Estimated from the onset wavelength of the solution-state op-
tical absorption. [c] LUMO=HOMO + E . [d] The synthesis of this po-
lymer has been reported previously, see reference
g
[
21]
.
4
75 nm (i.e. where only F is emitting) exhibits a low-energy
and redshifted peak at 390 nm (gray line), along with a
series of higher energy bands (Figure 6). Based on the ab-
sorption spectrum of Figure 3 (and the data of Table 1), the
observed 0–0 peak is located at 380 nm. This observation in-
dicates that the observed F fluorescence arises from the red-
with the intersystem crossing rate constant, without being
significantly larger. For example, the intersystem crossing
1
1
rate constant normally lies in the range between 10 and
12
ꢁ1
[14]
10
s
for heavy-atom-containing aromatics.
This state-
ment does not preclude the
possibility of sensitization of
the Cz triplet state by the F
chromophore (S –T ), although
1
1
such an event is much less en-
countered.
Evidence for total quenching
of the Cz fluorescence in P3
and M3 is provided by time-re-
solved spectroscopy during the
rise time of the laser excitation
pulse while excited at 340 nm
(
at this wavelength both chro-
mophores, Cz and F, are excit-
ed; see Figure 5). At the begin-
ning of the laser pulse (delay
time=43.5 ns), the signal inten-
sity is very weak but the vibron-
ic progression is perceptible. As
the delay time increases, the in-
tensity of the observed fluores-
cence expectedly increases, al-
lowing one to monitor the peak
Figure 3. Absorption ( ), emission (black line) and excitation spectra (&) of P1 (top left), P2 (top right), P3
(
&
bottom left) and M3 (bottom right) in degassed 2MeTHF at 77 K. Fluo=fluorescence; Phos=phosphores-
positions and their relative in- cence. For P2 and P3, the blue-shifted emissions (dashed line) are multiplied by 100 and 20, respectively.
Chem. Eur. J. 2008, 14, 8341 – 8352
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www.chemeurj.org
8345

W.-Y. Wong, P. D. Harvey et al.
arising from the
F chromo-
phore), the excitation spectrum
becomes different, resembling
more the observed absorption
spectrum (Figure 3). This result
indicates that both chromo-
phores (since the absorption is
composed of both units), but
primarily the Cz (since it is sig-
nificantly different from the ex-
citation spectrum with lobs
=
4
00, 420, 450, and 475 nm),
populate the lower-lying triplet
emissive state of F. Triplet
energy transfer Cz!F confirms
this (Figure 7).
While the exact individual
absorption profile for Cz and F
is unknown (and there is no
way of knowing because of the
conjugation between the two
chromophores), it is not possi-
ble to quantify the ratio of
Figure 4. Time-resolved emission spectra of P2 (top left), P3 (bottom left), M2 (top right), and M3 (bottom
right) in 2MeTHF at 77 K in the 10–50 ms time scale. The phosphorescence of the carbazole and fluorene chro-
mophores is indicated as Phos (Cz) and (F), respectively.
Figure 5. Time-resolved fluorescence spectra of M3 (top) and P3
(
bottom) in 2MeTHF at 77 K. The time delays are indicated on the
graphs and correspond to the rising time of the laser pulse where the
delay time of 43.5 ns is the beginning of the laser pulse and the delay
time of 45 ns is the pulse maximum (lexc =340 nm). The pulse width at
half maximum is 1.3 ns.
Figure 6. Excitation spectra of M3 and P3 in 2MeTHF at 77 K monitored
at different wavelengths. The grey lines represent a comparison mark of
the 0–0 peak of F with respect to the rest of the spectra.
shifted absorption system, which is that of F as well. Moni-
phosphorescence arising from the T (F) and T (Cz) states.
1
1
toring at 520 and 555 nm (i.e. in the phosphorescence band
Because of this uncertainty, it is also not possible to state
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Electron and Energy Transfer in Metallopolymers
FULL PAPER
sumably the 0–0 peak of F) is better defined. All in all, the
phosphorescence of F in P3 arises from both the Cz (via
triplet–triplet energy transfer) and F (via intersystem cross-
ing) moieties.
Evidence for triplet–triplet energy transfer is also provid-
ed from the transient spectra. The triplet–triplet absorption
[9,10]
processes for Cz and F are known.
In the presence of
triplet energy transfer, the triplet–triplet absorption is still
present, but in the presence of an efficient electron transfer
the triplet–triplet signature should vanish and be replaced
by an absorption band related to a charge-separated state;
Figure 7. Simplified representation of triplet energy transfer in organo-
metallic [-D-A-D-] systems. Transfers to both neighboring chromophores
n
are possible. Only one is shown for clarity.
ꢁ
in this work, F ion (i.e. fluorene anion) and [Cz-CꢀC-Pt-
+
with this experiment whether the Cz unit contributes to the
fluorescence of F in M3 (i.e. singlet–singlet energy transfer),
but the difference in excitation spectra monitored at 400,
A
H
R
U
G
3
2
spectra of M2, P2, M3, and P3, which are all very similar to
the triplet–triplet transient spectra of Cz and F,
4
5
20, 450, and 475 nm, representing the F unit, with that of
20 and 555 nm, representing
witness the presence of these species lying in their triplet
mostly Cz, is striking. The exci-
tation spectra monitored in the
F fluorescence band are those
of the F chromophore only,
whereas those monitored in the
F phosphorescence are those of
the Cz one (mostly). Thus, it
appears that the singlet–singlet
energy transfer from Cz to F is
relatively inefficient, which
strongly argues in favor of a
photo-induced electron transfer
process to explain the total ab-
sence of Cz fluorescence in M3
and P3. Based on this argument
and by analogy with other Cz–F
[9,10]
systems,
the quenching of
the Cz fluorescence is assigned
to an electron transfer from the
S1 state of Cz to F.
The emission spectrum of P3
monitored at 420 nm exhibits a
slightly redshifted signal with
Figure 8. Transient spectra of M2 (top left) and P2 (bottom left) in the 8–65 ms time scale and M3 (top right)
and P3 (bottom right) in 2MeTHF at 77 K excited at 355 nm in the 8–60 ms time scale.
respect to the absorption band (Figure 3), indicating also
that the F unit contributes to the observed fluorescence (of
F). At 450 nm, a signal associated with the Cz phosphores-
cence superimposed the fluorescence. The excitation spec-
trum monitored at this wavelength resembles that of the ab-
sorption, indicating that both Cz and F units contribute to
the overall intensity at 450 nm, consistent with the nature of
the emitted light. At 490 nm where the fluorescence and
phosphorescence of F is almost of no intensity, the excita-
tion spectrum (black line) differs from both the excitation
and absorption, strongly suggesting that the signature is that
of the Cz mostly. This is indeed confirmed by comparing
this excitation spectrum to that of the absorption spectra of
P1 and P2 (Figure 3) for which no F absorption occurs. The
excitation spectra monitored at 530 and 565 nm (in the
phosphorescence of the F unit), exhibit a band shape similar
to the absorption, except that the low-energy signal (i.e. pre-
states. No other band was observed, indicating that no
charge-separated state was detected in this time scale.
An investigation of the concentration effect on the emis-
ꢁ
6
ꢁ7
sion band in the range 1.8”10 to 4.4”10 m for P3 and
ꢁ
7
ꢁ5
2.2”10 to 1.2”10 m for M3 (typical concentrations in
this work) was performed to insure that no aggregation phe-
nomenon was observed. The resulting emission bands did
not change in position, shape, and relative intensity ratio.
Evidence for conjugation: Unambiguous evidence for conju-
gation across the polymer chain is provided by the compari-
son of the electronic spectra of compound IIIa (Figure 9), a
precursor presented in Scheme 2, with that of M3 and P3
(Figure 3 and Table 1). At 77 K, compound IIIa does not ex-
hibit phosphorescence, a process that is strongly promoted
by spin-orbit coupling due to the presence of Pt. In M3 and
P3, phosphorescence due to the F chromophore is the stron-
Chem. Eur. J. 2008, 14, 8341 – 8352
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
8347

W.-Y. Wong, P. D. Harvey et al.
The LUMO is also a p system localized primarily over
the F residue with some atomic contribution placed on the
neighboring C atoms of both Cz units. This not only indi-
cates the presence of weak conjugation over the Cz-F-Cz
fragment, but also the presence of a rather localized excited
state. The LUMO+1 and LUMO+2 exhibit p systems lo-
calized almost exclusively on the Cz unit, suggesting strong
localization of the upper excited states (i.e. S and T ). All
2
2
in all, the nature of these polyaromatic materials in their
ground state is conjugated, whereas the two lowest energy
excited states are localized.
Figure 9. Absorption (*), emission (black line), and excitation spectra
) of IIIa in 2MeTHF at 77 K (i.e. under the same experimental condi-
tions as in Figure 3).
Next, time-dependent DFT (TDDFT) was used to address
the nature of the lowest energy electronic transition, and
consequently the nature of the corresponding excited state.
The computed transition energy (0–0) is 359.5 nm, which
compares favorably with the 0–0 signal depicted (as a
shoulder) in the absorption spectra at 77 K for M3 and P3
(in the 360–380 nm range; Table 3). The computed oscillator
strength (f) is 1.13, indicating that the transition is allowed,
consistent with the observation. This transition is composed
of two components; HOMOꢁ2/LUMO and HOMO/LUMO
with a coefficient of 0.570 and 0.349, respectively. This result
corroborates that the low-energy excited state exhibits
(
&
gest signal. In addition, the peak positions for the fluores-
cence are 399 and 422 nm for M3 and 401 and 423 nm for
P3. These values are redshifted with respect to IIIa (388 and
409 nm; Figure 9). Both the redshift of the F fluorescence
and the enhancement of the phosphorescence intensity due
to intersystem crossing clearly demonstrate conjugation in
the Pt compounds.
Molecular orbital considerations: The frontier MOs are ad-
dressed by density functional theory (DFT) calculations
charge-transfer character of the type Cz-ꢀ-PtL -ꢀ-Cz!F, in-
2
cluding the HOMO!LUMO as well as the HOMOꢁ2!
using an optimized geometry for Cz-ꢀ-PtL -ꢀ-Cz-F-Cz-ꢀ-
LUMO transitions; the latter component being the major
2
[16]
PtL -ꢀ-Cz as a model (Figure 10). The degenerate HOMO
component.
2
Rates for triplet energy and singlet electron transfers at
7
7 K: The rate of triplet energy transfer (kET) is given by
0
[17]
0
kET =(1/t )ꢁ
A
H
R
U
G
e
times for the D–A dyad and a closely related compound in
0
e
which no energy transfer takes place. For P3 (t =52ꢃ2)
and M3 (132ꢃ6), P2 (66ꢃ6) and M2 (175ꢃ1 ms) were used
as comparative species, respectively. Hence, the triplet k
ET
3
3
ꢁ1
values are about 1.9”10 and 3.4”10 s for M3 and P3, re-
spectively. Taking into account the uncertainties, the lower
3
3
ꢁ1
and upper limits for kET for M3 are 1.5”10 and 2.3”10 s ,
3
3
ꢁ1
and for P3 are 1.4”10 and 5.1”10 s . The larger triplet
kET for P3 (excluding the uncertainties) agrees with a larger
number of pathways for energy transfers (one chromophore
on each side of the Cz) with respect to M3 (only one).
While these kET values compare favorably with those of
other triplet energy transfer systems, these values lie on
the lower end of the literature data. This is due to the fact
that only the short distance Dexter mechanism operates in
the triplet states, a process that involves a dual electron
transfer and therefore D–A orbital overlap. Owing to the
nonzero dihedral angle between Cz and F, these overlaps
are poorer (in comparison with fully conjugated planar sys-
Figure 10. MO representations of the frontier MOs of a model compound
Cz-ꢀ-PtL
-ꢀ-Cz-F-Cz-ꢀ-PtL -ꢀ-Cz. The energies are in a.u. (1 a.u.=
2
2
[17]
2
7.2114 eV).
[18]
[17]
(
together with HOMOꢁ1) and the nondegenerate
HOMOꢁ2 exhibit atomic contributions for a p system dis-
tributed over the Cz-ꢀ-PtL -ꢀ-Cz units in all cases, which is
2
consistent with this type of chromophore (Ph-ꢀ-PtL -ꢀ-
2
[
14c]
[18]
Ph).
This degeneracy is anticipated due to the identical
tems, or D-ꢀ-A for instance).
nature of the units. In addition, the HOMOꢁ2 also exhibits
an atomic contribution over the F chromophore, consistent
with the experimentally demonstrated conjugation in the
backbone, but does not showa Pt contribution. Instead, the
n-lone pairs of the P atoms, symmetrically appropriate for
the p system, are also computed.
A close examination of the fluorescence decay traces of
M3 and P3 indicates the presence of a single exponential,
meaning that the observed emissions arise from the F lumo-
phore only. Again, the Cz fluorescence is either totally
quenched or much too weak to be observed, which illus-
1
trates efficient singlet electron transfer ( Cz*!F). The lack
8348
www.chemeurj.org
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2008, 14, 8341 – 8352

Electron and Energy Transfer in Metallopolymers
FULL PAPER
of t (Cz) precludes an accurate evaluation of the rate of
Cz and NBD are not conjugated), the conversion of singlet
F
electron transfer, singlet k . By using the limit of our emis-
electron transfer at room temperature versus triplet energy
et
0
0
[9]
sion detection (F <0.0001), and k =(F /t )
A
H
R
U
G
A
H
R
N
transfer at 77 K was demonstrated. The time scale for
F
et
F
F
0
[18]
0
8
9
ꢁ1
F )],
where F and F are the fluorescence quantum
these events is 0.4”10 to 1.8”10 s for the electron trans-
F
F
F
ꢁ
1
yields for the donor in the dyad D–A and the model com-
pounds in which no electron transfer takes place (i.e. M1
fer at room temperature and 0.08 to 0.96 s for triplet
energy transfer at 77 K. These rates are much slower than
those reported in this work and are consistent with the pres-
ence (fast) or absence (slow) of conjugation. The shut down
of the electron transfer at lowtemperature comes from the
large solvent reorganization energy in frozen media. In this
work, the total quenching of the Cz fluorescence in M3 and
P3 is obvious. Therefore, a “shut down” mechanism was not
observed since total quenching of the Cz fluorescence was
observed at both temperatures. The reason for this most
likely comes from the fact that the oligomer M3 and the po-
lymer P3 are conjugated and so the cationic and anionic
charges are distributed over a large number of atoms.
0
=
0=
(
FF 0.033 at lexc =340 nm) and P1 (FF 0.0082 at lexc=
3
1
40 nm with respect to 9,10-diphenylanthracene; F =
F
[
19]
.0 )), one can evaluate the lower limit for singlet k (M3,
et
11
ꢁ1
11 ꢁ1
ket >10”10 s ; P3, ket >4”10 s ). These singlet ket
values occurring in the lowps time scale are comparable
with other rates measured for charge-separated states of var-
[18]
ious dyads.
In addition, the fact that a little bit of Cz
phosphorescence was observed for M3 and P3 suggesting
that ket competed (same order of magnitude) with the rate
1
1
12 ꢁ1
for intersystem crossing (normally in the 10 –10
scale),
s
time
[15]
indicates that the calculated limits for ket shown
above must be close to the real values.
M2 and P2, in which three Cz units are connected togeth-
er, were studied as well. The similarity in spectroscopic and
photophysical data (i.e. fluorescence and phosphorescence
lifetimes) between M1 and M2 and P1 and P2 reveals the
absence of singlet and triplet quenching no matter whether
there are two or three Cz units. This observation indicates
no singlet electron transfer and triplet energy transfer be-
tween the adjacent Cz and the central Cz in M2 and P2. No
triplet energy transfer rate could be measured at room tem-
perature since no Cz phosphorescence could be detected.
Concluding Remarks
This work reports the first example of quantified intrachain
electron transfer (inducing fluorescence quenching of D)
and energy transfer in conjugated organometallic polymers.
The rates are fast and slowfor singlet electron transfer and
triplet energy transfer, respectively. From the detailed emis-
sion spectral assignment, we can regard the Cz and F chro-
mophores as both singlet and triplet energy donor and ac-
ceptor, respectively. Apparently, kET is larger for P3 than for
M3 due to the number of possible sites for triplet energy
transfer, thus the photophysics of polymers are intrinsically
bound to differ from short-chain molecules. Remarkably, in-
tramolecular photophysical processes can influence the re-
sulting emission intensity of the various aryl fragments in
metallopolyynes. Based on the recorded spectra, it becomes
evident that depending on the selected aromatics, the inten-
sity of both the fluorescence and phosphorescence can be
adjusted. In this way, one can cover the whole visible spec-
trum (380–720 nm), hence inducing white light emission, a
much desired color for light-emitting diodes currently. Such
an approach will have an important impact on the way re-
searchers think in the design of novel metal-containing con-
jugated polymers for future practical optoelectronic applica-
tions.
Electrochemical findings: Cyclic voltammetry provides addi-
tional data regarding the thermodynamic driving forces for
the electron transfer process. The oxidation potentials mea-
sured for L1 and L2 (Table 3) are consistent with the pres-
ence of conjugation. For instance, the decrease in oxidation
potential on going from L1 to L2 indicates the presence of
an extended conjugation in L2 (two Cz units for L1 and
three Cz units for L2). Also, the increase in oxidation poten-
tials on going from L2 to L3 is consistent with the fact that
F is harder to oxidize than Cz, which also indicates that Cz
is more prone to act as an electron donor than F. A compar-
ison of the oxidation potentials between Ln and Pn (n=1–
3
(
) and polymer (-CꢀC-PtL -CꢀC-Cz-) (abbreviated as
ACHTREUNG
2
n
1
n
which is in agreement with the extension of the conjugation.
The relative tendency observed for L1 to L3 is also seen in
P1 to P3. All in all, the Cz center is the most likely unit
prone to oxidation, which agrees totally with the DFT find-
ings (see the degenerate HOMO and HOMOꢁ1). These
same calculations indicate that F is the most likely candidate
for reduction, in line with the electron transfer mechanism
occurring in the singlet state. No reduction wave was ob-
served within the electrochemical window of the solvent
used.
Experimental Section
General: All reactions were carried out under a nitrogen atmosphere by
using standard Schlenk techniques. Solvents were predried and distilled
from appropriate drying agents under an inert atmosphere prior to use.
Glassware was oven-dried at about 120 8C. All reagents and chemicals,
unless otherwise stated, were purchased from commercial sources and
used without further purification. The compounds 9-butylcarbazole-3-
Comments on singlet electron transfer versus triplet energy
transfer: In a recent paper dealing with dendrimers of carba-
zoles having norbornadiene (NBD) as a central core (where
[11d,20]
[21]
boronic acid,
hexylfluorene,
3,6-dibromo-9-butylcarbazole,
2,7-dibromo-9,9-di-
[21]
[22]
[23]
trans-[Pt
A
H
R
U
G
3
)
2
PhCl],
A
H
R
U
G
3 2 2
and trans-[Pt(PnBu ) Cl ]
were prepared according to the literature methods. Preparative TLC
Chem. Eur. J. 2008, 14, 8341 – 8352
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
8349

W.-Y. Wong, P. D. Harvey et al.
(
6
20 cm”20 cm) was performed on 0.7 mm silica plates (Merck Kieselgel
0 GF254) prepared in our laboratory.
Instrumentation: Infrared spectra were recorded as CH
using a Perkin–Elmer Paragon 1000 PC or Nicolet Magna 550 Series II
FTIR spectrometer, using CaF cells with a 0.5 mm path length. NMR
spectra were measured in appropriate deuterated solvents on a JEOL
EX270 or Varian Inova 400 MHz FT-NMR spectrometer, with
dissolved in CH
2
Cl
2
and the mixture was filtered through a short column
2 2
using pure CH Cl as eluent to give a brown solution of the polymeric
material. After removal of the solvent by using a rotary evaporator, a
brown powder was obtained. Further purification can be accomplished
2
2
Cl solutions
by precipitating the polymer solution in CH
pure P1 (91 mg, 59%). IR (CH Cl ): n˜ =2099 n
CDCl ): d=8.31–8.02 (m, 4H, Ar), 7.73–7.14 (m, 8H, Ar), 4.20 (m, 4H,
CH ), 2.19 (m, 12H, CH ), 1.79–1.30 (m, 32H, CH ), 0.95–0.86 ppm (m,
24H, CH ); C NMR (CDCl ): d=139.64, 139.00, 132.78, 128.77, 124.68,
122.76, 122.44, 119.82, 118.80, 118.06, 109.30, 108.76 (Ar), 108.51, 77.29
C), 42.92, 29.64, 26.07, 23.96, 21.97, 21.96, 13.97, 13.92 ppm (Bu);
2 2
Cl from MeOH to afford
2
ꢁ
1
1
2
2
A
H
R
U
G
; H NMR
(
3
a
1
31
H NMR chemical shifts quoted relative to SiMe
relative to an 85% H PO external standard. Fast-atom bombardment
FAB) mass spectra were recorded on a Finnigan MAT SSQ710 mass
4
, and P chemical shifts
2
2
2
1
3
3
4
3
3
(
(C
ꢀ
spectrometer in m-nitrobenzyl alcohol matrices. The molecular weights
of the polymers were determined by GPC (HP 1050 series HPLC with
visible wavelength and fluorescent detectors) using polystyrene standards
and THF as eluent, and the thermal analyses were performed with the
Perkin–Elmer TGA6 thermal analyzer. The UV/Vis spectra were record-
ed on a Hewlett-Packard diode array model 8452 A at Sherbrooke. The
emission and excitation spectra were obtained by using a double mono-
chromator Fluorolog 2 instrument from Spex. Phosphorescence time-re-
solved measurements were performed on a PTI LS-100 using a 1 ms tung-
sten flash lamp. Fluorescence and phosphorescence lifetimes were mea-
sured on a Timemaster Model TM-3/2003 apparatus from PTI. The
source was a nitrogen laser with a high-resolution dye laser (FWHM
ꢂ1.5 ns), and the fluorescence lifetimes were obtained from high-quality
decays and deconvolution or distribution lifetime analysis. The uncertain-
ties were about ꢃ40 ps based on multiple measurements. The flash pho-
tolysis spectra and the transient lifetimes were measured with a Luzchem
spectrometer using the 355 nm line of a YAG laser from Continuum (Ser-
ulite), and the 355 nm line from a OPO module pump by the same laser
3
1
1
1
P{ H} (CDCl
(%) for (C60
3
): d=3.89 ppm ( JPt,P=2362 Hz); elemental analysis calcd
Pt) : C 66.09, H 7.77, N 2.57; found: C 65.89, H 7.66,
=10700, M =8590, PDI=1.25; TGA: Tdecomp:
H
84
N
2
P
2
n
N 2.42; GPC (THF): M
348ꢃ58C.
w
n
Synthesis of P2: CuI (5.0 mg) was added to a mixture of L2 (89 mg,
.125 mmol) and trans-[Pt(PnBu Cl ] (84 mg, 0.125 mmol) in iPr NH/
CH Cl (40 mL, 1:1, v/v). After the same workup procedure as described
above, the polymer was isolated as a brown powder in 56% yield
0
A
H
R
U
G
3
)
2
2
2
2
2
ꢁ1
1
(
(
7
92 mg). IR (CH
s, 2H, Ar), 8.32 (s, 2H, Ar), 8.10 (m, 2H, Ar), 7.81 (m, 5H, Ar), 7.53–
.43 (m, 7H, Ar), 4.29 (m, 6H, CH ), 2.23 (m, 12H, CH ), 1.87 (m, 6H,
CH ), 1.67–1.49 (m, 30H, CH ), 0.99–0.89 ppm (m, 27H, CH
CDCl ): d=140.06, 139.95, 139.77, 138.97, 133.43, 133.11, 129.02, 125.26,
2
Cl
2
): n˜ = 2098 n
A
H
R
U
G
3
(C=C) cm ; H NMR (CDCl ): d=8.46
2
2
13
2
2
3
); C NMR
(
3
1
1
1
23.62, 123.49, 123.20, 122.85, 119.86, 118.89, 111.97, 109.24, 109.14,
08.98 (Ar), 108.23, 77.32 (CꢀC), 43.11, 29.69, 26.09, 23.97, 21.99, 20.64,
31
1
1
4.12, 13.91 ppm (Bu); P{ H} (CDCl
3
): d=3.89 ppm ( JPt,P =2358 Hz);
elemental analysis calcd (%) for (C76
.20; found: C 69.43, H 7.76, N 3.30; GPC (THF): M
34410, PDI=1.33; TGA: Tdecomp: 350ꢃ58C.
Synthesis of P3: This polymer was prepared similarly from L3 (81 mg,
.105 mmol) and trans-[Pt(PnBu Cl ] (70 mg, 0.105 mmol) and it was
H
99
N
3
P
2
Pt)
n
: C 69.59, H 7.61, N
(
FWHM=13 ns).
Quantum yield measurements: For room-temperature measurements, all
samples were prepared under an inert atmosphere (in a glove box, PO2
3
w
=45930, M
n
=
<
2
1
0 ppm) by dissolution of the different compounds in 2MeTHF using
mL quartz cells with septum (298 K) or quartz NMR tubes in liquid ni-
0
A
H
R
U
G
3
)
2
2
isolated as a pale brown powder in 57% yield (82 mg) after being puri-
trogen for 77 K measurements. Three different measurements (i.e. differ-
ent solutions) were performed for each set of photophysical data (quan-
tum yields, F and F ). The sample concentrations were chosen to corre-
F P
spond to an absorbance of 0.05 at the excitation wavelength. Each ab-
sorbance value was measured five times for better accuracy in the meas-
e e
urements of emission quantum yield (F ). The reference for F was 9,10-
ꢁ1
fied by the precipitation method. IR (CH
2
Cl
2
): n˜ =2099 n
A
H
R
U
G
;
1
H NMR (CDCl
H, Ar), 7.44 (m, 4H, Ar), 7.29 (m, 2H, Ar), 4.30 (m, 4H, CH
m, 16H, CH ), 1.88–1.53 (m, 32H, CH ), 1.26–0.73 ppm (m, 38H,
); C NMR (CDCl ): d=151.57, 140.86, 140.11, 139.39, 138.81,
3
): d=8.32 (s, 2H, Ar), 8.13 (s, 2H, Ar), 7.81–7.69 (m,
8
(
CH
2
), 2.26
2
2
13
2
CH
3
3
1
1
4
1
32.57, 129.10, 126.00, 125.04, 123.28, 123.16, 122.80, 122.61, 121.52,
[
19]
F
diphenylanthracene (F =1.0).
19.99, 119.81, 118.63, 109.22 (Ar) 108.83, 108.31 (CꢀC), 55.14 (quat. C),
Theoretical computations: Calculations were performed on an Intel
Xeon 3.40 GHz PC with the Gaussian 03 revision C.02 and Gausview 3.0
software package. The hybrid B3LYP exchange-correlation function was
2.96, 40.46, 31.07, 29.34, 26.30, 24.35, 24.00, 23.83, 22.67, 20.55, 14.10,
31
1
1
3.89 ppm (Bu); P { H} (CDCl
3
): d=3.95 ppm ( JPt,P =2357 Hz); ele-
mental analysis calcd (%) for (C81
H
108
N
2
P
2
Pt)
n
: C 71.18, H 7.96, N 2.05;
=21190, M =15890,
[
24–26]
used.
LANL2DZ pseudo-potentials and basis sets were used for plat-
found: C 71.29, H 7.76, N 2.32; GPC (THF): M
PDI=1.33; TGA: Tdecomp: 348ꢃ58C.
w
n
inum, 3–21G* pseudo-potentials for phosphorus, and 3–21G* basis sets
for all atoms
timized before the TDDFT calculation. Only the relevant (stronger oscil-
lator strength and wavefunction coefficients) molecular orbitals are
shown.
[
27,28]
except for platinum. The platinum structure file was op-
Synthesis of M1: The dehydrohalogenation reaction of L1 (23 mg,
.047 mmol) with two molar equivalents of trans-[Pt(PEt Cl(Ph)]
51 mg, 0.094 mmol) in the presence of CuI (3.0 mg) in iPr NH/CH Cl
40 mL, 1:1, v/v) afforded the title complex as a white solid in 21% yield
15 mg) after the usual workup by TLC on silica using CH Cl /hexane
0
A
H
R
U
G
3 2
)
(
(
(
(
(
2
2
2
Electrochemical measurements: Electrochemical measurements were
made using a Princeton Applied Research (PAR) model 273 A potentio-
stat. A conventional three-electrode configuration consisting of a glassy
carbon working electrode, and Pt wires as both the counter and reference
electrodes was used. The supporting electrolyte was 0.1m [Bu N]PF . Fer-
4 6
rocene was added as an internal standard after each set of measurements,
and all potentials reported were quoted with reference to the ferrocene–
ferrocenium (Fc/Fc ) couple at a scan rate of 100 mVs . The oxidation
potentials (Eox) were used to determine the HOMO energy levels using
the equation EHOMO =(Eox + 4.8) eV, and the LUMO energy levels were
2
2
1
ꢁ1
2:1, v/v) as eluent. IR (CH
2
Cl
2
): n˜ = 2096 n
A
H
R
U
G
; H NMR
CDCl ): d=8.33 (s, 2H, Ar), 8.09 (s, 2H, Ar), 7.77 (d, J=8.1 Hz, 2H,
3
Ar), 7.45–7.24 (m, 10H, Ph + Ar), 6.95 (t, J=8.1 Hz, 4H, Ph), 6.79 (t,
J=8.1 Hz, 2H, Ph), 4.29 (t, J=16.2 Hz, 4H, CH ), 1.81–1.61 (m, 28H,
of Bu), 1.41–1.39 (m, 4H, CH ), 1.17–0.92 ppm (m,
): d=156.83, 139.72,
2
CH
2
of Et + CH
2
2
13
4
1
1
3
1
2H, CH
3
3 3
of Et + CH of Bu); C NMR (CDCl
+
ꢁ1
39.29, 138.72, 133.32, 129.22, 127.19, 125.33, 123.27, 122.86, 122.39,
21.05, 120.03, 119.02, 110.58, 108.91 (Ar), 108.25, 108.69 (CꢀC), 42.92,
31
1
3
1.19, 20.56, 13.90 (Bu), 15.11, 8.07 ppm (Et); P{ H} (CDCl ): d=
determined from ELUMO =(EHOMO + E
lies at ꢁ4.8 eV with respect to the vacuum.
Syntheses
g
) eV, where the ferrocene value
1
+
0.99 ppm ( JPt,P =2643 Hz); FAB-MS: m/z: 1508 [M ]; elemental analy-
[
29]
sis calcd (%) for C72
H 6.53, N 1.95.
100 2 4 2
H N P Pt : C 57.36, H 6.69, N 1.86; found: C 57.20,
The syntheses of L1–L3 are given in the Supporting Information.
Synthesis of P1: A mixture of trans-[Pt(PnBu Cl ] (100 mg, 0.150 mmol)
and one equivalent of L1 (73 mg, 0.150 mmol) was dissolved in iPr NH/
CH Cl (40 mL, 1:1, v/v), and CuI (5.0 mg) was subsequently added.
After the mixture was stirred overnight at room temperature, all volatile
components were removed under reduced pressure. The residue was re-
Synthesis of M2: Similar to M1, this complex was prepared from L2
(23 mg, 0.033 mmol) and purified on preparative TLC plates with
A
H
R
U
G
3
)
2
2
CH
yield of 30% (17 mg). IR (CH
(CDCl ): d=8.47 (s, 2H, Ar), 8.34 (s, 2H, Ar), 8.07 (s, 2H, Ar), 7.80 (t,
J=8.1 Hz, 4H, Ar), 7.53–7.24 (m, 10H, Ph + Ar), 6.94–6.78 (m, 8H, Ph
2 2
Cl /hexane (2:3, v/v) as eluent to give an oily solid in an isolated
2
ꢁ1
1
Cl
2
): n˜ =2097 n
A
T
E
N
(CꢀC) cm
; H NMR
2
2
2
3
8350
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ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2008, 14, 8341 – 8352

Electron and Energy Transfer in Metallopolymers
FULL PAPER
+
Ar), 4.29 (m, 6H, CH
.45–1.42 (m, 6H, CH ), 1.16–0.92 ppm (m, 45H, CH
): d=140.06, 139.94, 139.77, 138.72, 137.21, 133.20,
32.98, 129.62, 127.32, 127.18, 125.68, 125.36, 124.78, 123.59, 122.88,
21.53, 121.02, 119.07, 111.91, 110.54, 109.16, 108.92 (Ar), 108.76, 108.25
2
), 1.81–1.61 (m, 30H, CH
2
of Et + CH
2
of Bu),
P. Lu, M. Hanif, D. Lu, G. Cheng, Y. Ma, J. Phys. Chem. B 2006,
110, 17784; d) M. Li, S. Tang, F. Shen, M. Liu, W. Xie, H. Xia, L.
Liu, L. Tian, Z. Xie, P. Lu, M. Hanif, D. Lu, G. Cheng, Y. Ma,
Chem. Commun. 2006, 3393; e) P. I. Shih, C. L. Chiang, A. K. Dixit,
C. K. Chen, M. C. Yuan, R. Y. Lee, C. T. Chen, E. W. G. Diau, C. F.
Shu, Org. Lett. 2006, 8, 2799; f) K. T. Wong, Y. M. Chen, Y. T. Lin,
H. C. Su, C. C. Wu, Org. Lett. 2005, 7, 5361; g) C.-L. Ho, W.-Y.
Wong, G.-J. Zhou, B. Yao, Z. Xie, L. Wang, Adv. Funct. Mater. 2007,
1
2
3
of Et + CH
3
of
1
3
Bu); C NMR (CDCl
1
1
3
3
1
1
(
(
CꢀC), 43.08, 31.21, 19.14, 13.53 (Bu), 15.11, 7.69 ppm (Et); P{ H}
1
+
3
CDCl ): d=11.00 ppm ( JPt,P =2629 Hz); FAB-MS: m/z: 1729 [M ]; ele-
mental analysis calcd (%) for C88
found: C 61.01, H 6.56, N 2.50.
115 3 4 2
H N P Pt : C 61.13, H 6.70, N 2.43;
1
7, 2925.
Synthesis of M3: A similar procedure to that for M1 was employed by
using L3 (48 mg, 0.062 mmol) to produce a white solid in 22% yield
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2006, 44, 3882; b) S. Lu, T. Liu, L. Ke, D. G. Ma, S. J. Chua, W.
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(
(
8
8
4
24 mg) after workup by TLC on silica by eluting with CH
2
Cl
2
/hexane
): d=
ꢁ1
1
2:3, v/v). IR (CH
.32 (s, 2H, Ar), 8.09 (s, 2H, Ar), 7.82–7.69 (m, 8H, Ar), 7.53–7.24 (m,
2
Cl
2
): n˜ = 2095 n
A
H
R
U
G
;
H NMR (CDCl
3
H, Ph + Ar), 6.96 (t, J=13.5 Hz, 4H, Ph), 6.79 (t, J=8.1 Hz, 4H, Ph),
.30 (t, J=8.1 Hz, 4H, CH
2
), 2.08–2.03 (m, 4H, CH
of Bu), 1.58–1.24 (m, 4H, CH
of Bu), 0.99–0.92 (m, 6H, CH
2
), 1.84–1.58 (m, 28H,
), 1.24–1.03 (m, 40H,
), 0.80–0.70 ppm (m,
): d=151.60, 140.97, 140.10, 139.27,
CH
CH
2
of Et + CH
of Et + CH
2
2
2
2
3
1
3
1
1
1
1
2
1
0H, CH
2
CH
3
); C NMR (CDCl
3
38.71, 132.63, 130.89, 128.80, 127.20, 126.09, 125.00, 123.27, 122.81,
22.40, 121.72, 121.06, 120.21, 119.74, 118.92, 110.53, 109.17, 108.76 (Ar),
08.32, 71.76 (CꢀC), 55.12 (quat. C), 42.93, 40.35, 31.17, 26.06, 23.13,
3
1
1
3
0.54, 19.13, 13.35 (Bu), 15.26, 7.68 ppm (Et); P{ H} (CDCl ): d=
1
664; g) U. H. F. Bunz, Chem. Rev. 2000, 100, 1605; h) W.-Y. Wong,
Dalton Trans. 2007, 4495; i) W.-Y. Wong, Macromol. Chem. Phys.
008, 209, 14.
1
+
0.97 ppm ( JPt,P =2629 Hz); FAB-MS: m/z: 1784 [M ]; elemental analy-
sis calcd (%) for C93
H 7.12, N 1.46.
124 2 4 2
H N P Pt : C 62.61, H 7.01, N 1.57; found: C 62.55,
2
[
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Received: February 19, 2008
Published online: July 28, 2008
8352
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ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2008, 14, 8341 – 8352