Oxygen and temperature sensitivity of blue to green to yellow light-emitting Pt(ii) complexes

Article abstract of DOI:10.1039/c2dt30835e

The synthesis and photophysical properties of a series of yellow-green to blue-green emitting heteroleptic, cyclometalated Pt(ii)(acac) complexes based on substituted phenylpyridine and tetrahydroquinoline ligands is reported. The luminescence intensities and lifetimes of these compounds were also studied in poly(styrene) films with respect to their responses to oxygen and temperature. Particularly, due to the insensitivity to oxygen quenching, these complexes are promising candidates as inert reference dyes in optical sensors. On the other hand, the Pt(ii) complex with 2-(4-bromophenyl)-5,6,7,8-tetrahydroquinoline as C^N ligand, displays a strong temperature quenching effect. The distinct response to temperature was additionally calibrated after incorporation in poly(vinylidene chloride-co-acrylonitrile) serving as oxygen-blocking matrix copolymer. The resulting yellow-green-emitting temperature sensor signifies an interesting alternative to the available mostly red emitting temperature-sensitive probes.

Full text of DOI:10.1039/c2dt30835e

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Dalton
Transactions
An international journal of inorganic chemistry
www.rsc.org/dalton
Volume 41 | Number 32 | 28 August 2012 | Pages 9555–9798
ISSN 1477-9226
COVER ARTICLE
Schäferling, Holder et al.
Oxygen and temperature sensitivity of blue to green to yellow light-emitting
Pt(II) complexes

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PAPER
Oxygen and temperature sensitivity of blue to green to yellow light-emitting
Pt(II) complexes
Cüneyt Karakus,a Lorenz H. Fischer,b Sebastian Schmeding,c Johanna Hummel,c Nikolaus Risch,c
Michael Schäferling*b and Elisabeth Holder*a
Received 17th April 2012, Accepted 18th May 2012
DOI: 10.1039/c2dt30835e
The synthesis and photophysical properties of a series of yellow-green to blue-green emitting heteroleptic,
cyclometalated Pt(II)(acac) complexes based on substituted phenylpyridine and tetrahydroquinoline
ligands is reported. The luminescence intensities and lifetimes of these compounds were also studied in
poly(styrene) films with respect to their responses to oxygen and temperature. Particularly, due to the
insensitivity to oxygen quenching, these complexes are promising candidates as inert reference dyes in
optical sensors. On the other hand, the Pt(II) complex with 2-(4-bromophenyl)-5,6,7,8-
tetrahydroquinoline as C^N ligand, displays a strong temperature quenching effect. The distinct response
to temperature was additionally calibrated after incorporation in poly(vinylidene chloride-co-acrylonitrile)
serving as oxygen-blocking matrix copolymer. The resulting yellow-green-emitting temperature sensor
signifies an interesting alternative to the available mostly red emitting temperature-sensitive probes.
sensitive probes with respect to color tunability, brightness, sen-
Introduction
sitivity, dynamic range, and photostability.1,11,12
Phosphorescent metal complexes are known to be of great practi-
cal interest in many fields of science and technology. They are
successfully implemented in light-emitting diodes1 and photo-
voltaics,2 as well as of interesting use as labels,3 amongst many
other relevant applications. Generally, triplet emitting transition
metal complexes are the probes of choice applied in optical
oxygen sensors. Oxygen indicators such as polypyridyl ruthe-
nium(II)4 and iridium(III) complexes5–7 have successfully been
used as an alternative to the widely used platinum(II)- or palla-
dium(II)-porphyrins.8,9 However, some of these oxygen-sensitive
probes have rather long luminescence decays up to milliseconds.
In contrast, the lifetimes of heteroleptic Pt(II) or Ir(III) complexes
are in the range from 1 to 10 μs and are perfectly suited for time-
resolved fluorescence detection and imaging, and in addition,
they exhibit much higher quantum yields, photostabilities and
sensitivities than related Ru(II) polypyridyl complexes.1,10–12
Contrary to the latter, Pt(II) or Ir(III) complexes offer a tremen-
dous ability for color tuning due to overlapping metal–ligand
charge transfer (MLCT) transitions.1,11,12 Therefore, Pt(II) and
Ir(III) complexes surpass the established luminescent oxygen-
As a consequence of their favourable properties, it has already
been demonstrated that platinum(II) complexes can be bene-
ficially applied to chemosensors,13 light-emitting devices,14
photovoltaics15,16 and colorimetric oxygen sensors,17 and, due to
their good cell membrane permeability, also in imaging of living
cells.18 Moreover, Pt(II) complexes are also promising indicators
for optical dual oxygen and temperature sensors, if they can be
combined with a second indicator and the resulting pressure and
temperature signals can be separated by optical filters. This can
be achieved, if the indicators emit at sufficiently different wave-
lengths without spectral overlap.5,19,20
In the red spectral region, it was found that e.g. bis(coumarin
acetylide)platinum(II) complexes demonstrate better oxygen sen-
sitivity than tris(2,2′-bipyridyl)ruthenium(II) complexes.21 On
the other hand, heteroleptic iridium(III) complexes5,6 reveal
excellent temperature sensitivity in the green spectral region
compared to red-emissive platinum(II)-porphyrins that reveal
only negligible temperature response.22,23
Generally, heteroleptic Pt(II) complexes with one cyclometa-
lating and one ancillary ligand like (Z)-5-hydroxy-2,2,6,6-tetra-
methylhept-4-en-3-one are known to be rather stable, color-
tunable, well-soluble and emissive in the microsecond region,12
while their emissive states are assigned to mixed 3LC-MLCT
states.12
We describe the synthesis of yellow-green via green to blue-
green emitting heteroleptic cyclometalated platinum(II) com-
plexes, which are based on substituted phenylpyridine- and tetra-
hydroquinoline-type C^N ligands and (Z)-5-hydroxy-2,2,6,6-
tetramethylhept-4-en-3-one as ancillary ligand. Contrary to the
commercial phenylpyridine-type C^N ligands, the halogen-
aFunctional Polymers Group and Institute of Polymer Technology,
University of Wuppertal, Gaußstr. 20, D-42097 Wuppertal, Germany.
E-mail: holder@uni-wuppertal.de; Fax: +49-202-439-3880;
Tel: +49-202-439-3879
bInstitute of Analytical Chemistry, Chemo- and Biosensors, University of
Regensburg, D-93040 Regensburg, Germany.
E-mail: michael.schaeferling@chemie.uni-regensburg.de
cOrganic Chemistry, University of Paderborn, Warburger Str. 100,
D-33098 Paderborn, Germany
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substituted tetrahydroquinoline C^N ligands were available via a
Mannich reaction. The resulting heteroleptic yellow-green to
blue-green emitting platinum(II) compounds were mixed into
poly(styrene) (PS) as polymer matrix to form sensitive films.
Their temperature dependency was investigated by following
their reduced luminescence lifetimes.
NH2OH·HCl in order to form the individual target tetrahydroqui-
nolines25 L3–L5 (Scheme 1). The particular Mannich bases
were prepared by aminomethylation of the respective phenyl-
ketone derivatives with N,N-dimethylmethyleneiminiumchlor-
ide27,28 (Scheme 1). The C^N ligands L3–L5 were readily
soluble in solvents of medium polarity. Their molecular weights
1
were expectedly observed while the H and 13C NMR spectra
revealed the characteristic pattern. Additionally, ligands L3–L5
were characterized by FT-IR spectroscopy and their bulk purity
was furthermore confirmed by elemental analysis. Finally, five
Pt(II) complexes 1–5 were synthesized (Scheme 2) by using a
facile two step synthesis.1,5,6,12,29 Tailoring the Lewis method,29
the C^N ligands L1–L5 (Chart 1) and K2PtCl4 were heated for
16 h in a mixture of 2-ethoxyethanol and water (3 : 1) at 80 °C.
The resulting μ-chloro-bridged precursor dimers of complexes
1–5 were isolated in a yield of 68% to 84%. In order to receive
the dipivaloylmethane Pt(II) complexes 1–5, in yields of 36% to
79%, the individual dimers were heated (3–6 h) with dipivaloyl-
Results and discussion
Synthesis and characterization
A series of C^N ligands L1–L5 (Chart 1) was used in order to
subsequently prepare a set of Pt(II) complexes 1–5 revealing
temperature sensitivity at short wavelengths. Rather than using
C–C coupling chemistry,1,6,24 the synthesis of three tetrahydro-
quinoline-based C^N ligands L3–L5 took place by the reaction
of the respective Mannich bases25 with 1-morpholinocyclohex-
ene,26 then forming 1,5-diketones,25 which were cyclized with
methane, using Na2CO3 as
a base, in 2-ethoxyethanol
(Scheme 2). Note longer reaction times lead to significant for-
mation of by-products. The Pt(II) complexes 1–5 were chromato-
graphically purified over silica gel using dichloromethane and
n-hexane (1 : 3 v/v) and re-crystallized, correspondingly.
Complexes 1–5 were readily soluble in halogenated solvents
like chloroform but also in n-hexane. In the ESI mass spectra the
molecular ions [M + H]+ (M = neutral complexes) were
Chart 1 C^N ligands L1–L5 used in order to subsequently prepare
Pt(II) complexes 1–5.
Scheme 2 Exemplified synthetic route from ligands L1–L5 via
μ-chloro-bridged precursor dimers 1–5 to Pt(II) complexes 1–5.
Scheme 1 Synthesis of 5,6,7,8-tetrahydroquinoline derivatives L3–L5 in yields of L3 46%, L4 50% and L5 54%. X = –Br (L3), –F (L4), –CF3
(L5).
9624 | Dalton Trans., 2012, 41, 9623–9632
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expectedly observed at m/z 533.2, 569.2, 666.1, 605.2 and
of complexes 1–5 show a characteristic pattern of two maxima,
ranging from the blue to the yellow spectral region (Table 1).
The determined extinction coefficients of 3500–29 000 and
quantum efficiencies of 5.2–15.0% are comparable to those of
similar complexes previously reported in the literature.12,30–33
The strong absorption for all complexes 1–5 at 225–345 nm can
be related to spin-allowed ligand-centered transitions (π → π*),
which are the expected absorption bands in this region.18,34,35
Solvatochromatic metal-to-ligand charge transfer (MLCT) and
ligand-to-ligand charge transfer (LLCT) transitions are located
between 350 and 450 nm.18,12
1
655.2. The H and 13C NMR spectra showed the characteristic
t
pattern of the signals of Bu from the dipivaloylmethane ancil-
lary ligand at 1.23–1.31 ppm, and the olefinic proton at
5.83–5.90 ppm. For complexes 2, 4 and 5 19F NMR confirmed
likewise the aromatic fluorine and aromatic –CF3 resonances,
respectively. Additionally, complexes 1–5 were characterized by
FT-IR spectroscopy and their purity was moreover affirmed by
elemental analysis.
The UV-vis absorption and emission spectra of complexes
1–5 were recorded in n-hexane at a concentration of 1 ×
10−5 mol L−1 and are shown in Fig. 1 and 2, while the data are
summarized in Table 1, correspondingly. The emission spectra
The β-diketonato ligand has no detectable influence on the
luminescence properties of the excited state.1,5,6,12 The emission
3
of the complexes 1–5 is due to a mixed LC-MLCT state12 and
the particular effects of the respective C^N substituents can
directly be seen in the emission spectra (Fig. 2), correspondingly.
Compared to complex 1, the fluoro-substituted complexes 2, 4
and 5 demonstrate a blueshift; in contrast, the bromo-substituted
complex 3 illustrates a redshift. Obviously, the +I effect of the
aliphatic ring is stronger than the −I effect of the bromo-substitu-
ent.1,6,12 Thus, significant emission color tuning from blue
through green to yellow has been achieved by varying the cyclo-
metalating C^N ligands and, more specifically, in case of the
5,6,7,8-tetrahydroquinoline derivatives L3–L5 by modifying the
commercially available phenylketone-derivatives that have been
used in order to prepare the Mannich base intermediates
(Scheme 1).
Fig. 1 UV-vis spectra of 1–5 in n-hexane solutions (c = 1 ×
10−5 mol L−1) at room temperature.
Pressure and temperature sensitivity
The complexes 1–5 were incorporated into poly(styrene) (PS)
films (thickness 6 μm) and their luminescence lifetimes (Table 1)
were measured according the rapid lifetime determination (RLD)
method.36,37 The lifetimes τ0 in absence of oxygen are usually
not much affected by the polymer matrix, but it determines sig-
nificantly the sensitivity of the luminophore to oxygen and temp-
erature.38 Despite its limited oxygen permeability, PS is a
standard polymer matrix for the characterization of oxygen and
temperature sensitivities of quenchable probes. Thus, Stern–
Volmer constants are available for many phosphorescent metal–
ligand complexes for comparison.39
The light source for excitation is a 405 nm LED and the lumi-
nescence intensity is integrated in two precisely timed gates by a
triggered CCD camera.
After a short light pulse, the luminescence intensity is
acquired in the first gate A1. Likewise, the intensity in the
Fig. 2 Luminescence spectra of complexes 1–5 in n-hexane (c = 1 ×
10−5 mol L−1).
Table 1 Photophysical data of Pt(II) complexes 1–5 in n-hexane (c = 1 × 10−5 mol L−1) at room temperature
UV-vis (nm) {ε(dm3 mol−1 cm−1)}
λmax-em. (nm)
Φ (%)
τ0 (μs)a
1
2
3
4
5
251 (26 100), 287 (21 600), 326 (13 500), 335 (13 800), 363 (8700), 382 (9300), 408 (5100)
250 (29 000), 282 (22 400), 317 (15 000), 329 (16 500), 358 (9600), 374 (11 000)
254 (18 900), 286 (21 500), 324 (3900), 340 (8400), 380 (5600)
251 (17 500), 280 (17 900), 318 (6400), 336 (5500), 374 (5300), 391 (3500)
252 (19 300), 285 (18 600), 307 (5100), 337 (6100), 392 (6000), 410 (4400)
488, 524
468, 501
505, 535
491, 526
501, 538
15
5.7
5.2
6.4
7.0
5.8
9.1
10.8
5.2
6.9
a At 50 mbar air pressure and 30 °C in a 6 μm poly(styrene) film.
This journal is © The Royal Society of Chemistry 2012
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Fig. 3 Temperature dependence of the luminescence lifetime of the
cyclometalated Pt(II) complexes ppy 1, 2,4-Fppy 2, Brph-thq 3, Fph-thq
4 and CF3ph-thq 5 in PS at 1000 mbar air pressure. The values for
Brph-thq are fitted according to eqn (3) for demonstration.
Fig. 4 Response of the luminescence lifetimes of ppy 1, 2,4-Fppy 2,
Brph-thq 3, Fph-thq 4 and CF3ph-thq 5 in PS to oxygen at a temperature
of 30 °C displayed as Stern–Volmer plots with linear fits according to
eqn (2). τ0 refers to the lifetime at 10 kPa pO2 and 30 °C.
second gate A2 and the dark images are recorded. The whole
imaging process has been described in previous works.40
The luminescence lifetime (τ) can be estimated according to
eqn (1).41
Table 2 Stern–Volmer constants KSV and temperature coefficients of
the cyclometalated Pt(II) complexes 1–5 in 6 μm PS films
Complex
KSV [10−4 mbar−1 b
]
T-coeff. [%τ/°C]a,b
t2 ꢀ t1
1
2
3
4
5
1.6
0.9
1.6
1.2
1.1
0.54
0.66
0.76
0.58
0.51
τ ¼
ð1Þ
lnðA1=A2Þ
where t1 and t2 are delay times of the two gates A1 and A2 after
the excitation pulse. However, this equation only gives correct
lifetimes if the decay of luminescence is monoexponential and
both time gates are of the same length. Usually, the condition of
monoexponential decay is not fulfilled. Thus, only mean values
of τ can be obtained with this simple process. But RLD is a valu-
able method to characterize relative changes of τ responding to
luminescence quenching by oxygen or thermal quenching. The
ratiometric measurement provides an intrinsically referenced
signal, independent from variations in the intensity of the exci-
tation light and other common interferences in luminescence
measurements and, therefore, is more accurate than the detection
of changes in luminescence intensity. All the imaging measure-
ments were performed with square samples of 3 × 3 cm size of
the dyed PS films. The samples were fixed inside a calibration
chamber, capable of holding air pressures from 50 to 2000 mbar
and temperatures from 1 to 60 °C. A more detailed description
of the chamber and the imaging setup is described in a previous
publication.5
The response of the luminescence of the studied complexes to
increasing temperature is shown in Fig. 3. All measurements
were performed using PS as the matrix polymer. It displays a
moderate oxygen permeability P of 1.9 × 10−13 cm3 (STP) cm
(cm2 s Pa)−1 (STP = standard temperature and pressure).42
In general, thermal quenching is observed for every lumines-
cent dye. With increasing temperature the nonradiative relaxation
rates are increasing. This is due to the Boltzmann distribution,
which governs the population of the vibrational levels of the
electronic states. At higher temperatures the deactivating states
become thermally activated and the energy difference between
the electronic states can be converted more easily into vibrational
energy. The calibration plots for the temperature response are
nonlinear and can be fitted by an Arrhenius-type equation
a At 30 °C and 1000 mbar air pressure. b In PS.
(eqn (2)), with k0 as the temperature independent decay rate for
the deactivation of the excited state, k1 as the pre-exponential
factor, and ΔE as the energy gap between emitting level and
deactivating excited level.43 The temperature dependency of
Brph-thq 3 is fitted exemplarily in Fig. 3.
ꢀ
ꢁ
1
ΔE
¼ k0 þ k1 exp ꢀ
ð2Þ
τ
RT
The luminescence quenching of the Pt(II) emitters 1–5 by
oxygen is depicted in Fig. 4 in the form of Stern–Volmer plots.
The luminescence lifetime is proportional to partial oxygen
pressure (pO2) according to the Stern–Volmer equation (eqn
(3)). The excited triplet state is deactivated by a collision with
oxygen.
I0 τ0
¼
¼ 1 þ KSV½Qꢁ
τ
ð3Þ
I
In this equation, I0 is the luminescence intensity and τ0 the life-
time in the absence of quencher (oxygen). I and τ are fluor-
escence intensity and lifetime, respectively, in the presence of an
oxygen concentration of [Q]. The presence of oxygen quenches
the luminescence lifetime and intensity likewise.
The Stern–Volmer constants KSV and the temperature coeffi-
cients obtained from these measurements are shown in Table 2.
Generally, the oxygen sensitivity of the studied platinum com-
plexes is very weak in contrast to other phosphorescent metal
complexes such as platinum(II)-porphyrins,22,44,45 ruthenium(III),46
9626 | Dalton Trans., 2012, 41, 9623–9632
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tetramethylhept-4-en-3-one as ancillary ligand. Divergent to the
commercial phenylpyridine-type ligands,12 the halogen-substi-
tuted tetrahydroquinoline ligands were available via a Mannich
reaction leading to a series of novel Pt(II) complexes. The intro-
duced complexes reveal lifetimes of several microseconds and
quantum yields of up to 15%. These luminescence intensities
and lifetimes of the Pt(II) complex series were also studied with
respect to their responses to oxygen and temperature. All
addressed cyclometalated Pt(II) complexes show generally only a
very low sensitivity to oxygen and temperature. Particularly, the
insensitivity to oxygen quenching is unusual for phosphorescent
metal–ligand complexes. Accordingly, these complexes are
promising candidates to be used as inert reference dyes in optical
sensors. However, the 2-(4-bromophenyl)-5,6,7,8-tetrahydroqui-
noline substituted Pt(II) complex was found to display a strong
temperature quenching effect. This response to temperature was
calibrated after incorporation in PVDCAN. The resulting green-
emitting temperature sensor represents an appealing alternative
to the available but mostly red light-emitting temperature-sensi-
tive probes.
Fig. 5 Temperature dependence of the luminescence lifetime of Brph-
thq 3 in PVDCAN at various air pressures.
or some iridium(III)1,5,6 complexes characterized in PS. These
represent typical luminescent oxygen indicators with Stern–
Volmer constants that are significantly higher compared to the
complexes presented here. The calculated lifetimes τ0 of the
complexes are all in the same range around 5–7 μs, thus, their
Stern–Volmer constants are also alike within the accuracy of this
determination method. With exception of 2,4-Fppy 2 and Brph-
thq 3, also thermal quenching is only very weakly pronounced.
Hence, these luminophores are promising candidates for inert
reference complexes that can be applied e.g. in optical sensors or
for ratiometric dual-wavelength fluorescence measurements. Par-
ticularly, complex 4 and 5 are rather insensitive to either thermal
or oxygen quenching. The latter can be further suppressed by
incorporation in gas-blocking polymer materials.5,6
In terms of optical sensor applications, the complex 3 is inter-
esting as a temperature-sensitive probe. Its temperature coeffi-
cient is almost as high as that of typical luminescent indicators
for T such as ruthenium and europium complexes.9,37 The
advantage of this new T probe compared to the frequently
applied ruthenium complexes is that it is only marginally
quenched by oxygen. Ruthenium probes always respond likewise
to temperature and oxygen. Thus, 3 was incorporated in a gas-
blocking polymer matrix of poly(vinylidene chloride-co-acrylo-
nitrile) (PVDCAN). The results of the response to temperature
are shown in Fig. 5.
Experimental section
General remarks
All reagents were used as purchased from commercial suppliers
without further purification. All reactions were carried out by
using standard Schlenk techniques under an atmosphere of dry
argon. Solvents were used as purchased without further purifi-
cation. 1H NMR and 13C NMR spectra were performed on a
BRUKER ARX 125, ARX 200 and ARX 500 as well as on a
BRUKER III AVANCE 600; 19F NMR spectra were performed
on a BRUKER AVANCE 400. Chemical shifts were quoted rela-
tive to the internal standard tetramethylsilane (Me4Si) in CDCl3
solutions. For 1H (s = singlet, d = doublet, t = triplet, q = quartet
and m = multiplet), 13C NMR data, J values are given in Hertz
(Hz). Mass spectrometry was carried out by using electron
impact (EI, 70 eV) and electrospray ionization (ESI) techniques
on a Finnigan MAT 8230 and a Bruker Daltonics MICROTOF
instrument, respectively. Fourier transform infrared (FT-IR)
spectra were recorded on a JASCO FT/IR-4200 as well as on a
Nicolet 510 P FT-IR spectrometer. Elemental analysis (EA) was
performed on a Perkin Elmer 240 B and on a HEKAtech
EuroEA 3000 (CHNS) setup, correspondingly. UV-vis spectra
were measured with a JASCO V-550 UV-vis spectrometer (1 cm
cuvettes) at concentrations of 1 × 10−5 mol L−1. The emission
spectra were performed using a CARY Eclipse fluorescence
It is evident that the resulting optical temperature sensor is vir-
tually inert to oxygen quenching and exhibits a constant lumi-
nescence in a very broad air pressure range from 50 to
1950 mbar. In contrast to luminescent indicators for temperature
based on ruthenium,41,47 europium,9,48 or iridium5,6 complexes,
the emission of 3 is comparably short-wave, enabling a combi-
nation with a second red emitting indicator such as platinum(II)-
porphyrins for simultaneous detection of oxygen in dual sensors.
spectrophotometer at concentrations of 1 × 10−5 mol L−1
.
Absorption and emission spectra for the determination of
pressure and temperature sensitivity were recorded on a Lambda
14p Perkin-Elmer UV-vis spectrophotometer (Waltham, MA,
USA, www.perkinelmer.com) and an Aminco AB 2 lumines-
cence spectrometer (Thermo Scientific Inc., Waltham, MA,
USA, www.thermo.com), respectively. The p/T calibration
chamber was provided by the German Aerospace Center (DLR)
in Göttingen.9 All time-resolved measurements were performed
with a PCO SensiCam 12 bit b/w CCD camera (PCO, Kelheim,
Germany, www.pco.de) equipped with a Schneider-Kreuznach
Xenon 0.95/17 lens (Jos. Schneider Optische Werke, Bad
Conclusions
The synthesis and photophysical properties of a series of yellow-
green to blue-green light-emitting heteroleptic, cyclometalated
[(C^N)Pt(II)(acac)] complexes is reported. The platinum(II)
complexes are based on substituted phenylpyridine- and tetrahy-
droquinoline-type C^N ligands and (Z)-5-hydroxy-2,2,6,6-
This journal is © The Royal Society of Chemistry 2012
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Kreuznach, Germany, www.schneiderkreuznach.com) and a
405-66-60 405 nm LED from Roithner Lasertechnik (Vienna,
Austria, www.roithner-laser.com). The excitation light was
focused by a PCX 18_18 MgF2 TS lens from Edmund Optics
(Karlsruhe, Germany, www.edmundoptics.com). It was filtered
through a BG 12 filter (Schott, Mainz, Germany, www.schott.
com) with a thickness of 2 mm. Emission was detected through
a GG 475 high pass filter purchased from AHF Analysentechnik
(www.ahf.de). The PS films and the PVDCAN films containing
the Pt(II) complexes 1–5 were prepared with a knife coating
device on a solid poly(ethylene terephtalate) (PET) support.
The concentration of the polymer solutions was 5% (w/w)
in THF. The polymers were purchased from Sigma-Aldrich
(www.sigmaaldrich.com). In order to increase the luminescence
intensity recorded by the camera, the backside of the PET foils
740 mg (89%) colorless solid. 1H NMR (500 MHz, CDCl3): δ =
2.85 (s, 6H), 3.48–3.53 (t, 2H), 3.72–3.76 (t, 2H), 7.12–7.18 (m,
4
3JH,F = 9.0 Hz, 2H), 8.01–8.06 (m, JH,F = 5.5 Hz, 2H),
12.62–12.88 (bs, 1H).
Synthesis of dimethyl-(3-oxo-3-(4-trifluoromethylphenyl))pro-
pylammoniumchloride. 4-(Trifluoromethyl)acetophenone 5.0 g
(26.5 mmol) and N,N-dimethyliminiumchloride (2.5 g,
26.5 mmol). Yield: 4.32 g (58%) colorless solid. 1H NMR
(500 MHz, CDCl3): δ = 2.87 (s, 6H), 3.50–3.57 (t, 2H),
3
3.80–3.84 (t, 2H), 7.85–7.90 (m, J = 8.0 Hz, 2H), 8.11–8.16
(m, 3J = 8.0 Hz, 2H), 12.54–12.72 (bs, 1H).
General procedure for the diketones25
The enamine (0.1 mol) and the Mannich base (0.1 mol) were
stirred in abs. dioxane (100 mL) for 16 h under reflux. After
adding distilled water (30 mL) the mixture was heated for 1 h.
The mixture cooled and water (30 mL) was added and extracted
with dichloromethane (4 × 40 mL). The organic layers were
combined and washed with diluted hydrochloric acid (20 mL)
and water.
was coated with
a highly reflective layer of TiO2 in
silicone. Chromatography: Separations were carried out on
Geduran Si 60 (0.063–0.200 mm). Thin layer chromatography
(TLC) was performed on Analtech uniplate silica gel GF plates
(500 micron, 20 × 20 cm) and developed with (n-hexane–ethyl
acetate: 10 : 3).
Methyleniminiumchloride,27,28 the enamine49 and 1-morpho-
linocyclohexene,26 as well as the dimers29 1 and 2 and com-
plexes12 1 and 2 were synthesized according to partly modified
literature procedures.
Synthesis of 2-(3-oxo-3-(4-bromophenyl)-propyl)cyclohexa-
none. Dimethyl-(3-oxo-3-(4-bromophenyl))propylammonium-
chloride (6.04 g, 20.7 mmol) and 1-morpholinocyclohexene
1
(3.5 g, 20.7 mmol). Yield: 4.17 g (65%) brown oil. H NMR
Synthesis of N,N,N′,N′-tetramethylmethanediamine. Dimethyl-
amine (40%, 45 mL, 0.4 mol) was added drop-wise to a stirred
ice cooled solution of formaldehyde (37%, 15 mL, 0.2 mol).
Yield: 16.7 g (81%), bp.: 82 °C (Lit.50 Yield: 85%, bp.:
(500 MHz, CDCl3): δ = 1.32–1.48 (m, 1H), 1.58–1.71 (m, 3H),
1.79–1.88 (m, 2H), 1.99–2.14 (m, 3H), 2.21–2.44 (m, 2H),
3
2.82–3.10 (m, 2H), 7.53–7.57 (d, J = 8.5 Hz, 2H), 7.79–7.82
3
(d, J = 8.5 Hz, 2H). 13C NMR (125 MHz, CDCl3): δ = 24.56
1
81.5–83 °C). H NMR (200 MHz, CDCl3): δ = 2.23 (s, 12 H,
(t), 25.09 (t), 28.08 (t), 34.60 (t), 36.36 (t), 42.23 (t), 49.94
(d), 128.08 (s), 129.67 (d), 131.84 (d), 135.58 (s), 199.19 (s),
213.04 (s).
N(CH3)2), 2.72 (s, 2 H, CH2).
Synthesis of N,N-dimethyliminiumchloride. Acetylchloride
(8.5 ml, 0.12 mol) in diethylether (50 mL) was added drop-wise
to a ice cooled suspension of N,N,N′,N′-tetramethylmethanedi-
amine (10.2 g, 0.10 mol). The mixture was stirred overnight at
room temperature. The iminium salt was rapidly filtrated, washed
with diethyl ether and then dried under vacuum. Yield: 8.4 g
Synthesis of 2-(3-oxo-3-(4-fluorophenyl)-propyl)cyclohexa-
none. Dimethyl-(3-oxo-3-(4-fluorophenyl))propylammoniumch-
loride (740 mg, 3.2 mmol) and (530 mg, 3.2 mmol) enamine
1-morpholinocyclohexene. Yield: 128 mg (16%) yellow oil after
purification by column chromatography on silica gel (CH2Cl2–
Et2O 1 : 1 as eluent). 1H NMR (500 MHz, CDCl3): δ =
1.39–1.50 (m, 1H), 1.61–1.73 (m, 3H), 1.83–1.89 (m, 1H),
2.02–2.17 (m, 3H), 2.26–2.34 (m, 1H), 2.36–2.46 (m, 2H),
2.87–2.96 (m, 1H), 3.04–3.14 (m, 1H), 7.07–7.13 (t, 2H),
1
(90%) (Lit.51 Yield: 92%). H NMR (200 MHz, CDCl3): δ =
3.79 (s, 6 H, N(CH3)2), 8.49 (s, 2 H, CH2vN).
General procedure for the Mannich bases25
3
7.97–8.03 (m, JH,F = 9.0 Hz, 2H). 13C NMR (125 MHz,
The ketone (10 mmol) and N,N-dimethyliminiumchloride
(10 mmol) were refluxed in abs. acetonitrile (25 mL) for 3–4 h
under dry conditions. The Mannich base was filtrated after
cooling down in the fridge and dried under vacuum.
CDCl3): δ = 24.66 (t), 25.09 (t), 28.10 (t), 34.62 (t), 36.33 (t),
42.25 (t), 49.98 (d), 115.60 (d, 2JC,F = 20 Hz), 130.75 (d, 3JC,F
8 Hz), 133.33 (d, JC,F = 3 Hz), 165.69 (d, JC,F = 245 Hz),
=
4
1
198.67 (s), 213.10 (s).
Synthesis of dimethyl-(3-oxo-3-(4-bromophenyl))propylam-
moniumchloride. 4′-Bromoacetophenone (9.96 g, 50 mmol) and
N,N-dimethyliminiumchloride (4.69 g, 50 mmol). Yield: 8.38 g
(57%) colorless crystals. Bp.: 194.6 °C (Lit.52: 200.5–201.5 °C).
1H NMR (500 MHz, CDCl3–MeOD): δ = 2.80 (s, 6H),
Synthesis of 2-(3-oxo-3-(4-trifluoromethylphenyl)-propyl)-
cyclohexanone. Dimethyl-(3-oxo-3-(4-trifluoromethylphenyl))-
propylammoniumchloride (4.1 g, 22 mmol) and 1-morpholino-
cyclohexene (3.6 g, 22 mmol). Yield: 2.0 g (30%) pale yellow
solid after purification by column chromatography on silica gel
(CH2Cl2–Et2O 1 : 1 as eluent). 1H NMR (500 MHz, CDCl3): δ =
1.34–1.44 (m, 1H), 1.55–1.68 (m, 3H), 1.74–1.84 (m, 1H),
1.95–2.10 (m, 3H), 2.20–2.28 (m, 1H), 2.28–2.43 (m, 2H),
2.87–2.95 (m, 1H), 3.04–3.12 (m, 1H), 7.61–7.65 (d, 3J = 8.0 Hz,
2H), 7.98–8.03 (d, 3J = 8.0 Hz, 2H). 13C NMR (125 MHz,
3
3.41–3.46 (t, 2H), 3.56–3.61 (t, 2H), 7.54–7.58 (d, J = 8.5 Hz,
2H), 7.79–7.83 (d, 3J = 8.5 Hz, 2H).
Synthesis of dimethyl-(3-oxo-3-(4-fluorophenyl))propylammo-
niumchloride. 4-Fluoroacetophenone (500 mg, 3.6 mmol) and
339 mg (3.6 mmol) N,N-dimethyliminiumchloride. Yield:
9628 | Dalton Trans., 2012, 41, 9623–9632
This journal is © The Royal Society of Chemistry 2012

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3
3
CDCl3): δ = 24.39 (t), 25.04 (t), 27.99 (t), 34.52 (t), 36.65 (t),
7.42–7.50 (q, J = 8.0 Hz, 2H), 7.67–7.70 (d, J = 8.0 Hz, 2H),
1
3
3
42.15 (t), 49.81 (d), 123.59 (q, JC,F = 272 Hz), 125.52 (q, JC,F
8.05–8.09 (d, J = 8.0 Hz, 2H). 13C NMR (125 MHz, CDCl3):
2
= 4 Hz), 128.38 (4JC,F = 1 Hz), 134.10 (q, JC,F = 32 Hz),
δ = 22.72 (t), 23.13 (t), 28.60 (t), 32.83 (t), 118.08 (d), 124.31
139.49 (s), 199.06 (s), 212.77 (s).
(q, 1JC,F = 272 Hz), 125.54 (q, 3JC,F = 4 Hz), 127.03 (d), 130.24
2
4
(q, JC,F = 32 Hz), 131.80 (s), 137.54 (d, JC,F = 1 Hz),
143.22 (s), 152.99 (s), 157.71 (s). IR (KBr): ν (cm−1) = 2942,
2867, 2361, 1688, 1620, 1569, 1460, 1329, 1255, 1164,
1124, 1067, 1015, 856, 833, 810, 599. MS (70 eV): m/z (%) =
279 (1), 278 (15), 277 (100), 249 (17), 180 (3). C16H14F3N
(277.11): calcd C 69.30, H 5.09, N 5.05; found C 69.13, H 4.41,
N 5.00.
General procedure for the functionalized C^N ligands L3–L525
The diketone (10 mmol) and the hydroxylamine hydrochloride
(10 mmol) were stirred in ethanol (10 mL) overnight
under reflux. The reaction mixture was subsequently cooled
down to room temperature, neutralized with Na2CO3,
mixed with water (50 mL) and extracted with dichloromethane
(4 × 30 mL). The organic layers were dried over Na2SO4 and
evaporated. The crude product was purified by column
chromatography.
General procedure for the Pt(II)-μ-dichloro-bridged
dimers1,5,6,12,29
K2PtCl4 and ligand HC^N (2.2 equiv.) was stirred in a Schlenk
flask for 16 h at 80 °C in a mixed solution of 2-ethoxyethanol
and water (3 : 1). After cooling down to room temperature, the
respective dimeric complexes were isolated in water, filtered, and
washed with water and ethanol. The precursor complexes were
dried under reduced pressure.
Synthesis of 2-(4-bromophenyl)-5,6,7,8-tetrahydroquinoline.
2-(3-Oxo-3-(4-bromophenyl)propyl)cyclohexanone (3.0 g,
4.4 mmol) and NH2OH·HCl (674 mg, 9.7 mmol). Yield: 1.27 g
(46%) yellow solid after purification by column chromatography
on silica gel (CH2Cl2 as eluent). Bp.: 114.5 °C (Lit.27:109 °C).
1H NMR (500 MHz, CDCl3): δ = 1.79–1.85 (m, 2H), 1.88–1.94
(m, 2H), 2.74–2.79 (t, 2H), 2.96–3.00 (t, 2H), 7.34–7.39 (m,
2H), 7.52–7.55 (m, 2H), 7.81–7.84 (m, 2H). 13C NMR
(125 MHz, CDCl3): δ = 22.79 (t), 23.20 (t), 28.59 (t), 32.85 (t),
117.53 (d), 122.75 (s), 128.37 (d), 131.17 (s), 131.70 (d), 137.51
(d), 138.72 (s), 153.22 (s), 157.41 (s). IR (KBr): ν (cm−1) =
2929, 2859, 2360, 2343, 1683, 1653, 1575, 1560, 1541, 1510,
1487, 1456, 1256, 1131, 1068, 1005, 806, 743. MS (70 eV): m/z
(%) = 289 (97), 288 (54), 287 (100), 261 (13), 208 (5), 180 (10),
77 (6). C15H14BrN (287.03): calcd C 62.52, H 4.90, N 4.86;
found C 62.29, H 4.40, N 4.87.
Dimer 1.12,29 2-Phenylpyridine (400 mg, 2.577 mmol) and
K2PtCl4 (486 mg, 1.171 mmol). Yield: 325 mg (72%) yellow
green powder.
Dimer 2.12 2,4-Difluorophenylpyridine (442 mg, 2.312 mmol)
and K2PtCl4 (441 mg, 1.051 mmol). Yield: 356 mg (80%)
yellow green powder.
Dimer 3. 2-(4-Bromophenyl)-5,6,7,8-tetrahydroquinoline
(697 mg, 2.420 mmol) and K2PtCl4 (457 mg, 1.100 mmol).
Yield: 480 mg (84%) dark green powder.
Synthesis of 2-(4-fluorophenyl)-5,6,7,8-tetrahydroquinoline.
Dimer 4. 2-(4-Fluorophenyl)-5,6,7,8-tetrahydroquinoline
(214 mg, 0.942 mmol) and K2PtCl4 (178 mg, 0.428 mmol).
Yield: 137 (70%) dark green powder.
2-(3-Oxo-3-(4-fluorophenyl)propyl)cyclohexanone
(2.4
g,
4.8 mmol) and NH2OH·HCl (672 mg, 4.8 mmol). Yield: 1.1 g
(50%) yellow oil after purification by column chromatography
on silica gel (petrol ether–Et2O 6 : 1 as eluent). 1H NMR
(500 MHz, CDCl3): δ = 1.81–1.86 (m, 2H), 1.90–1.95 (m, 2H),
Dimer 5. 2-(4-Trifluoromethylphenyl)-5,6,7,8-tetrahydroqui-
noline (212 mg, 0.765 mmol) and K2PtCl4 (144 mg,
0.347 mmol). Yield: 120 mg (68%) yellow green powder.
3
2.77–2.81 (t, 2H), 2.96–3.00 (t, 2H), 7.09–7.14 (m, JH,F = 9.0
4
Hz, 2H), 7.39–7.40 (s, 2H), 7.91–7.95 (m, JH,F = 5.5 Hz, 2H).
13C NMR (125 MHz, CDCl3): δ = 22.79 (t), 23.19 (t), 28.52
(t), 32.83 (t), 115.37 (d), 115.54 (d), 117.53 (d), 128.50 (d),
128.57 (d), 130.69 (s), 136.08 (s), 137.47 (d), 153.63 (s), 157.31
General procedure for the Pt(II) complexes1,5,6,12
The particular dimers were stirred in a Schlenk flask with dipiva-
loylmethane (3 equiv.) and Na2CO3 (10 equiv.) in 2-ethoxyetha-
nol at 80 °C for 3–6 h. The residue was filtered, purified using
thin layer chromatography (n-hexane–ethyl acetate) or column
chromatography (CH2Cl2–n-hexane) and re-crystallized,
correspondingly.
1
(s), 163.22 (d, JC,F = 255 Hz). IR (KBr): ν (cm−1) = 3068,
3048, 3018, 2934, 2880, 2860, 2835, 1684, 1600, 1589, 1570,
1511, 1458, 1433, 1419, 1388, 1355, 1293, 1230, 1185, 1159,
1126, 1096, 1048, 1015, 989, 938, 849, 834, 812, 749, 668,
557, 520, 483. MS (70 eV): m/z (%) = 228 (67), 229 (6), 227
(100), 226 (92), 199 (70), 133 (19), 77 (10). C15H14FN
(227.11): calcd C 79.27, H 6.21, N 6.16; found C 79.35, H 7.31,
N 6.54.
Complex 1.12
Synthesis of 2-(4-trifluoromethylphenyl)-5,6,7,8-tetrahydro-
quinoline. 2-(3-Oxo-3-(4-trifluoromethylphenyl)propyl)cyclo-
hexanone (2.68 g, 9 mmol) and NH2OH·HCl (626 mg,
9 mmol). Yield: 1.35 g (54%) yellow oil after purification by
column chromatography on silica gel (petrol ether–Et2O 6 : 1 as
1
eluent). H NMR (500 MHz, CDCl3): δ = 1.81–1.89 (m, 2H),
1.90–1.98 (m, 2H), 2.79–2.84 (t, 2H), 2.97–3.03 (t, 2H),
This journal is © The Royal Society of Chemistry 2012
Dalton Trans., 2012, 41, 9623–9632 | 9629

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Complex 3.
Dimer 1 (311 mg, 0.405 mmol), 2,2,6,6-tetramethyl-3,5-hepta-
nedione (166 mg, 0.903 mmol) and Na2CO3 (319 mg,
3.01 mmol). After purification by column chromatography on
silica gel (CH2Cl2–n-hexane 1 : 3 as eluent) yellow crystals
(252 mg, 58%) (Found: C 50.06, H 5.37, N 2.52. C22H27NO2Pt
requires C 49.62, H 5.11, N 2.63); νmax/cm−1 3106, 3045, 2952,
2919, 2855, 2352, 1731, 1605, 1583, 1523, 1487, 1458, 1308,
1272, 1243, 1218, 1181, 1139, 1066, 1023, 1010, 952, 930, 873,
1
822, 787, 740, 722, 658 and 629; H NMR (600 MHz; CDCl3;
Me4Si) 1.30k (s, 9 H, CH3), 1.31i (s, 9 H, CH3), 5.83j (s, 1H,
CH), 7.06–8.18b,g (m, 2H, ArH), 7.23f (td, J = 7.4, 1.3 Hz, 1 H,
ArH), 7.43–7.52h (m, 1H, ArH), 7.63d (d, J = 8.0 Hz, ArH),
7.69e (dd, J = 7.6, 1.1 Hz, 1H, ArH), 7.81c (td, J = 7.8, 1.5 Hz,
1H, ArH) and 9.03a (d, J = 5.2 Hz, 1H, ArH); 13C NMR
(100 MHz; CDCl3; Me4Si) 28.36, 28.64, 41.07, 41.50, 93.22,
118.29, 121.17, 122.92, 123.39, 129.28, 130.97, 137.95, 140.06,
144.70, 147.11, 168.58, 193.76 and 195.12; m/z (ESI): 533.2
(M+-C22H27NO2Pt requires 532.17); λmax-absorption(n-hexane)/nm
251 (ε/dm3 mol−1 cm−1 26 100), 287 (21 600), 326 (13 500),
Dimer 3 (178 mg, 0.173 mmol), 2,2,6,6-tetramethyl-3,5-hepta-
nedione (95 mg, 0.518 mmol) and Na2CO3 (183 mg,
1.725 mmol). After purification by column chromatography on
silica gel (CH2Cl2–n-hexane 1 : 3 as eluent) yellow crystals
(150 mg, 65%) (Found
C
47.28,
H
4.99,
N
2.16.
C26H32BrNO2Pt requires C 46.92, H 4.85, N 2.10); νmax/cm−1
2955, 2934, 2905, 2866, 2366, 2334, 1591, 1587, 1548, 1526,
1497, 1443, 1412, 1389, 1358, 1243, 1221, 1185, 1143, 1070,
1038, 873, 822, 794, 751, 708, 654 and 614; 1H NMR
(600 MHz; CDCl3; Me4Si) 1.24l (s, 9H, CH3), 1.31j (s, 9H,
CH3), 1.79–1.92b,c (m, 4H, CH2), 2.82d (t, J = 6.3 Hz, 2H,
CH2), 3.57a (t, J = 6.4 Hz, 2H, CH2), 5.88k (s, 1H, CH),
7.19–7.24g,h (m, 2H, ArH), 7.37f (d, J = 8.1 Hz, 1H, ArH), 7.46e
(d, J = 8.1 Hz, 1H, ArH), 7.86i (d, J = 1.7 Hz, 1H, ArH) ppm.
13C NMR (100 MHz; CDCl3; Me4Si) 21.81, 22.91, 28.51,
28.69, 29.10, 30.89, 32.25, 40.69, 42.21, 92.51, 115.31, 121.97,
123.66, 126.43, 131.55, 132.36, 138.24, 138.98, 145.15, 162.74,
165.77, 193.56, 195.48, 206.79 ppm; m/z (ESI): 666.1
(M+-C26H32BrNO2Pt requires 664.13); λmax-absorption(n-hexane)/
nm 254 (ε/dm3 mol−1 cm−1 18 900), 286 (21 500), 324 (3900),
340 (8400), 380 (5600); λmax-emission(n-hexane)/nm 505,
535; Quantum yield(n-hexane)/% 10.8.
335 (13 800), 363 (8700), 382 (9300), 408 (5100); λmax-emission
(n-hexane)/nm 488, 524; Quantum yield(n-hexane)/% 15.
-
Complex 2.12
Complex 4.
Dimer 2 (151 mg, 0.180 mmol), 2,2,6,6-tetramethyl-3,5-hepta-
nedione (100 mg, 0.540 mmol) and Na2CO3 (191 mg,
1.800 mmol). After purification by column chromatography on
silica gel (CH2Cl2–n-hexane 1 : 3 as eluent) yellow crystals
(74 mg, 36%) (Found: C 47.08, H 4.23, N 2.49. C22H25F2NO2Pt
requires C 46.48, H 4.43, N 2.46); νmax/cm−1 2977, 2948, 2923,
2901, 2858, 2362, 1605, 1545, 1530, 1497, 1437, 1397, 1362,
1297, 1243, 1225, 1189, 1160, 1143, 1114, 1095, 1066, 984,
Dimer 4 (105 mg, 0.115 mmol), 2,2,6,6-tetramethyl-3,5-hepta-
nedione (71 mg, 0.385 mmol) and Na2CO3 (136 mg,
1.280 mmol). After purification by column chromatography on
silica gel (CH2Cl2–n-hexane 1 : 3 as eluent) yellow crystals
(110 mg, 79%) (Found C 51.70, H 5.46, N 1.71. C26H32FNO2Pt
requires C 51.65, H 5.33, N 2.32); νmax/cm−1 2995, 2934, 2858,
1587, 1545, 1530, 1494, 1451, 1412, 1389, 1358, 1308, 1268,
1243, 1221, 1185, 1142, 873, 848 and 791; 1H NMR (600 MHz;
CDCl3; Me4Si) 1.23l (s, 9H, CH3), 1.30j (s, 9H, CH3),
1.77–1.94b,c (m, 4H, CH2), 2.81d (t, J = 6.2 Hz, 2H, CH2), 3.56a
(t, J = 6.2 Hz, 2H, CH2), 5.88k (s, 1H, CH), 6.79h (td, J = 8.6,
2.6 Hz, 1H, ArH), 7.30–7.40f,g,i (m, 3H, ArH), 7.44e (d, J =
8.1 Hz, 1H, ArH) ppm. 13C NMR (100 MHz; CDCl3; Me4Si)
21.85, 22.94, 28.50, 28.71, 29.03, 32.24, 40.78, 42.70, 92.52,
110.49, 110.72, 115.05, 115.79, 115.98, 123.97, 124.06, 130.85,
139.01, 142.47, 162.44, 165.84, 193.48, 195.49 ppm. 19F NMR
1
956, 876, 848, 801, 768, 751, 737, 701, 658 and 633; H NMR
(600 MHz; CDCl3; Me4Si) 1.31i (s, 9H, CH3), 1.31g (s, 9H,
CH3), 5.87h (s, 1H, CH), 6.60e (m, 1H, ArH), 7.15–7.19b,f (m,
2H, ArH), 7.86c (m, J = 1H, ArH), 8.00d (d, J = 8.1 Hz, 1H,
ArH), 9.05a (d, J = 6.1 Hz, 1H, ArH). 13C NMR (100 MHz;
CDCl3; Me4Si) 28.31, 28.37, 28.64, 28.86, 41.05, 41.46, 93.54,
99.19, 112.90, 121.12, 122.05, 138.59, 147.06, 194.25,
195.49 ppm. 19F NMR (400 MHz, CDCl3): δ = −112.75,
−106.94 ppm; m/z (ESI): 569.2 (M+-C22H25F2NO2Pt requires
568.15); λmax-absorption(n-hexane)/nm 250 (ε/dm3 mol−1 cm−1
29 000), 282 (22 400), 317 (15 000), 329 (16 500), 358 (9600),
374 (11 000); λmax-emission(n-hexane)/nm 468, 501; Quantum
yield(n-hexane)/% 9.1.
9630 | Dalton Trans., 2012, 41, 9623–9632
This journal is © The Royal Society of Chemistry 2012

View Article Online
D. Hertel, E. Holder, K. Meerholz and U. S. Schubert, Adv. Mater., 2008,
20, 129; N. Tian, A. Thiessen, R. Schiewek, O. J. Schmitz, D. Hertel,
K. Meerholz and E. Holder, J. Org. Chem., 2009, 74, 2718; C. Ulbricht,
N. Rehmann, E. Holder, D. Hertel, K. Meerholz and U. S. Schubert,
Macromol. Chem. Phys., 2009, 210, 531; N. Tian, Y. V. Aulin,
D. Lenkeit, S. Pelz, O. V. Mikhnenko, P. W. M. Blom, M. A. Loi and
E. Holder, Dalton Trans., 2010, 39, 8613; N. Tian, D. Lenkeit, S. Pelz,
D. Kourkoulos, D. Hertel, K. Meerholz and E. Holder, Dalton Trans.,
2011, 40, 11629.
(400 MHz, CDCl3): δ = −75.21 ppm; m/z (ESI): 605.2
(M+-C26H32FNO2Pt requires 604.21); λmax-absorption(n-hexane)/
nm 251 (ε/dm3 mol−1 cm−1 17 500), 280 (17 900), 318 (6400),
336 (5500), 374 (5300), 391 (3500); λmax-emission(n-hexane)/nm
491, 526; Quantum yield(n-hexane)/% 5.2.
Complex 5.
2 B. O’Regan and M. Grätzel, Nature, 1991, 353, 737; V. Marin,
E. Holder, M. M. Wienk, E. Tekin, D. Kozodaev and U.
S. Schubert, Macromol. Rapid Commun., 2005, 26, 319; V. Marin,
E. Holder and U. S. Schubert, J. Polym. Sci., Part A: Polym. Chem.,
2004, 42, 374.
3 C. Li, J. Lin and Y. S. Guo Zhang, Chem. Commun., 2011, 47, 4442;
E. Holder, M. A. R. Meier, V. Marin and U. S. Schubert, J. Polym. Sci.,
Part A: Polym. Chem., 2003, 41, 3954; V. Marin, E. Holder,
M. A. R. Meier, R. Hoogenboom and U. S. Schubert, Macromol. Rapid
Commun., 2004, 25, 793; E. Holder, D. Oelkrug, H.-J. Egelhaaf,
H. A. Mayer and E. Lindner, J. Fluoresc., 2002, 12, 383.
4 I. Gryczynski, J. Malicka, E. Holder, N. DiCesare and J. R. Lakowicz,
Chem. Phys. Lett., 2003, 372, 409; E. Holder, G. Schoetz, V. Schurig and
E. Lindner, Tetrahedron: Asymmetry, 2001, 12, 2289; E. Holder,
G. Trapp, J. C. Grimm, V. Schurig and E. Lindner, Tetrahedron: Asymme-
try, 2002, 13, 2673; E. Holder, O. Trapp, G. Trapp, V. Marin,
R. Hoogenboom and U. S. Schubert, Chirality, 2004, 16, 363.
5 L. H. Fischer, M. I. J. Stich, O. S. Wolfbeis, N. Tian, E. Holder and
M. Schäferling, Chem.–Eur. J., 2009, 15, 10857.
Dimer 5 (103 mg, 0.099 mmol), 2,2,6,6-tetramethyl-3,5-hepta-
nedione (55 mg, 0.296 mmol) and Na2CO3 (105 mg,
0.990 mmol). After purification by column chromatography on
silica gel (CH2Cl2–n-hexane 1 : 3 as eluent) yellow solid (66 mg,
50%) (Found C 49.57, H 4.31, N 2.29. C27H32F3NO2Pt requires
C 49.54, H 4.93, N 2.14); νmax/cm−1 2966, 2930, 2866, 2362,
1591, 1562, 1530, 1497, 1480, 1454, 1412, 1389, 1362, 1311,
1243, 1164, 1120, 1074, 959, 902, 873, 808, 791, 747, 712, 650
and 610; 1H NMR (600 MHz; CDCl3; Me4Si) 1.25l (s, 9H,
CH3), 1.31j (s, 9H, CH3), 1.79–1.94b,c (m, 4H, CH2),
2.81–2.83d (t, J = 6.3 Hz, 2H, CH2), 3.56–3.63a (t, J = 6.4 Hz,
2H, CH2), 5.90k (s, 1H, CH), 7.32h (dd, J = 8.0, 1.3 Hz, 1H,
ArH), 7.43g (d, J = 8.1 Hz, 1H, ArH), 7.46f (d, J = 8.1 Hz, 1H,
ArH), 7.50e (d, J = 8.1 Hz, 1H, ArH), 8.05i (d, J = 1.3 Hz, 1H,
ArH) ppm. 13C NMR (100 MHz; CDCl3; Me4Si) 21.75, 22.87,
28.51, 28.62, 29.15, 32.33, 40.81, 42.24, 53.39, 92.58, 115.84,
120.26, 122.03, 126.25, 132.50, 136.20, 139.04, 149.56, 163.10,
165.20, 193.71, 195.63 ppm. 19F NMR (400 MHz, CDCl3): δ =
−63.21 ppm; m/z (ESI): 655.2 (M+-C27H32F3NO2Pt requires
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Acknowledgements
The authors acknowledge the DFG (Deutsche Forschungs-
gemeinschaft) for financially supporting this work with grant
applications HO3911/3-1 and HO3911/6-1. E. H. acknowledges
Prof. Ullrich Scherf for granting access to the tools of the Macro-
molecular Chemistry at the University of Wuppertal (BUW) and
Melanie Dausend and Ilka Polanz (Organic Chemistry, BUW)
for performing routine mass spectrometry as well as Ralf Radon
(Analytical Chemistry, BUW) and the group of Prof. Klaus
Meerholz at the University of Cologne for their help with the
elemental analysis.
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