A Designed TEMPO-derivate Catalyst with Switchable Signals of EPR and Photoluminescence: Application in the Mechanism of Alcohol Oxidation

Article abstract of DOI:10.1002/cctc.201800345

Construction the in situ, real-time monitoring methodology for chemical changes, especially in the mechanism of oxidation, has long been regarded as a significant and challenging concern. Herein, we designed and synthesized a TEMPO-mediated alkynylplatinum(II) terpyridine complex with switchable activity in photoluminescence and EPR (Electron Paramagnetic Resonance) spectra. This complex of alkynylplatinum(II) terpyridine-TEMPO [(2, 2,6,6-tetramethylpiperidin-1-yl)oxyl] is paramagnetic, while the in situ formed alkynylplatinum(II) terpyridine-TEMPOH is diamagnetic, so that concentration changes of TEMPO/ TEMPOH species were obtained successfully by photoluminescence and EPR spectra in an operando way. As a model example, we investigated the mechanism of alcohol oxidation mediated by TEMPO/ bis(acetoxy)iodo]benzene (BAIB). It was found that, with the consumption of co-oxidant (BAIB), the concentration and conformation of catalyst (TEMPO) were changed gradually, and the vital role of catalyst and co-oxidant in the benzyl alcohol oxidation was clearly showed by photoluminescence and EPR spectroscopies. On the basis of these observations, we suggested an effective methodology to study the mechanism of chemical reaction, which is promising for further practical applications in analytical or environmental issues.

Full text of DOI:10.1002/cctc.201800345

Accepted Article
Title: A designed TEMPO-derivate Catalyst with Switchable Signals of
EPR and Photoluminescence: Application in the Mechanism of
Alcohol Oxidation
Authors: Lu Yin, Jiaxiang Zhang, Jia Yao, and Haoran Li
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Link to VoR: http://dx.doi.org/10.1002/cctc.201800345
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ChemCatChem
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A Designed TEMPO-derivate Catalyst with Switchable Signals of
EPR and Photoluminescence: Application in the Mechanism of
Alcohol Oxidation
[a]
[a]
[a]
[a,b]
Lu Yin, Jiaxiang Zhang, Jia Yao, and Haoran Li *
Abstract: Construction the in situ, real-time monitoring methodology
for chemical changes, especially in the mechanism of oxidation, has
long been regarded as a significant and challenging concern. Herein,
Bruckner who presented commendably the first three coupled
operando spectroscopies setup for mechanistic studies of
copper/TEMPO-catalyzed alcohol oxidation. They have directly
I
II
we
designed
and
synthesized
a
TEMPO-mediated
detected the redox reaction of TEMPO and Cu /Cu , and
postulated that TEMPO could stabilize the copper complex-
TEMPO intermediate.[7] However, in some cases, the TEMPOH
species are also key intermediates in the recycle process, the
detection of TEMPOH species have not been concerned much.
If we developed a method to take notice of TEMPO species and
TEMPOH species at the same time, we could trace more details
about TEMPO-mediated reaction.
alkynylplatinum(II) terpyridine complex with switchable activity in
photoluminescence and EPR (Electron Paramagnetic Resonance)
spectra. This complex of alkynylplatinum(II) terpyridine-TEMPO
[
(2,2,6,6-tetramethylpiperidin-1-yl)oxyl] is paramagnetic, while the in
situ formed alkynylplatinum(II) terpyridine-TEMPOH is diamagnetic,
so that concentration changes of TEMPO/ TEMPOH species were
obtained successfully by photoluminescence and EPR spectra in an
operando way. As a model example, we investigated the mechanism
of alcohol oxidation mediated by TEMPO/ bis(acetoxy)iodo]benzene
As we know, TEMPO is paramagnetic species which can be
detected by EPR spectrum, whereas TEMPOH belongs to
diamagnetic species, which can be detected by other spectrum,
fluorescence spectrum, for example. The fluorescence spectrum
has the advantages of high sensitivity, chemical specificity,
selectivity and continuity in studying catalysis,[8] and the
spectroscopy of EPR is powerful in studying solid catalysts and
molecular interactions in situ studies,[ specifically in detecting
paramagnetic species containing unpaired electrons. Thus, the
fluorescence and EPR spectroscopies are complementary each
other, but signals of the two spectra are not likely to occur in the
meantime. For purpose of obtaining a realistic situation of the
working catalytic reaction without sacrificing required reaction
conditions, simultaneous integration of two in situ
spectroscopies to monitor the composition of product is
(BAIB). It was found that, with the consumption of co-oxidant (BAIB),
the concentration and conformation of catalyst (TEMPO) were
changed gradually, and the vital role of catalyst and co-oxidant in the
benzyl alcohol oxidation was clearly showed by photoluminescence
and EPR spectroscopies. On the basis of these observations, we
suggested an effective methodology to study the mechanism of
chemical reaction, which is promising for further practical
applications in analytical or environmental issues.
9]
Introduction
TEMPO-mediated oxidations of alcohols attract much
attention.[1] Those pathway are facilitated by the transition metal
or metal-free stoichiometric oxidants,[2, 3] to undergo two-electron
redox steps. Of the particular contribution in this field is the use
of TEMPO and copper as oxidants pioneered by the groups of
Sheldon and Stahl.[4] Currently available set-ups for catalyst
characterization and reaction monitoring range all the way,[5]
whereas the intermittent sampling methods may lose part of
information more or less, so real-time and in situ methods for
studying the working catalyst and interpretation of reaction
mechanism are necessary. In recent years, the UV, infrared, and
Raman spectroscopy were most common in application of in situ
oxidation,[6] but in situ EPR and fluorescence spectra are
relatively rare. Pioneering work has been done by the group of
[10]
becoming more advantageous. If a TEMPO-mediated catalyst
with switchable responses to EPR and photoluminescence
spectroscopy was synthesized, the status of TEMPO and
TEMPOH species could be achieved easily in a reaction.
Based on knowledge of structure-reactivity relationships of
catalysts, we have rationally designed and synthesized a novel
bifunctional molecular probe with fluorescence and EPR
6
properties, [Pt(terpy-TEMPO)(C≡CPh)](PF ), (Complex 1, terpy
=
2,2':6',2''-terpyridine), which is also an appropriate TEMPO-
containing platinum terpyridine complex catalyst. As alcohol was
oxidized by TEMPO, accordingly, aldehyde and TEMPOH were
formed. Subsequently, the TEMPOH was converted to TEMPO
again by the co-oxidant of BAIB which was mole equivalent to
alcohol. So the change of TEMPO/TEMPOH signal could reflect
the process of substrate oxidation in real time. In addition, the
different molecular states of Complex 1 can be detected by
different spectroscopic methods during the catalytic reaction, to
show directly the real-time state of the reaction process. Then
we revisited the well-known alcohol oxidation by using Complex
1 instead of TEMPO in along with BAIB. In this case, benzyl
alcohol oxidation was catalyzed efficiently by Complex 1 as
TEMPO did. Moreover, it could act excellently as an
EPR/fluorescence bi-functional probe in this reaction, due to the
entirely different behavior of TEMPO style (paramagnetic
species) and in situ formation of TEMPOH style (diamagnetic
species) from Complex 1.
[
a]
b]
L Yin, J Zhang, Prof. J Yao, Prof. H Li
Department of Chemistry, ZJU-NHU United R&D Center, Zhejiang
University
Hangzhou 310027, PR China
E-mail: lihr@zju.edu.cn
[
Prof. H Li
State Key Laboratory of Chemical Engineering, Department of
Chemical and Biological Engineering, Zhejiang University
Hangzhou 310027, PR China
Supporting information for this article is given via a link at the end of
the document.
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Thus,
a
method of coupled fluorescence/EPR was
2, [Pt(terpy)(C≡CPh)](PF
6
), without TEMPO was gained by the
established to monitor directly the changes of chemical reaction.
Via operando combining the fluorescence and EPR spectra, we
could obtain an efficient method for the studying of the catalytic
mechanism.
analogous copper-catalyzed method.
Generally speaking, rich photophysical properties were
showed by alkynylplatinum(II) terpyridine complexes,[14] so it was
unambiguous that Complex 1 displayed typical π-π*, LLCT and
MLCT transitions (Figure 1 A). The transitions of Complex 1
were similar to Complex 2 in which there was no substituent of
TEMPO. Therefore, the TEMPO radical introduced to the
terpyridine did not affect the electron transition of the
alkynylplatinum(II) terpyridine. Upon subsequent adding of
ascorbic acid into the DMF solution of Complex 1(the
experimental details see supporting information), the complex
gradually turned into diamagnetic species Complex 1’ (Figure 1
B) leading to the switch off of the EPR signals, meanwhile,
luminescence emission switched on. It was visualized that the
EPR signal lost, and at the same time the luminescence
appeared (Figure 1 B, C), which was reversible upon adding
BAIB (Figure S4). Furthermore, the emission property of
Complex 1’ was analogous to Complex 2 to show a maximum
emission wavelength at 566 nm, verified by the similar
fluorescence spectra of the two complexes (Figure 1 B).
Therefore, Complex 1 shows obvious EPR signals and potential
emission signals. Moreover, these properties are very helpful in
the study of reaction mechanism.
Results and Discussion
Photophysical Studies of the Complexes
Platinum terpyridine complexes were prepared via
a
modified ligand-chelation and ion-exchange methods, as
illustrated in Scheme 1. These complexes with different
substituent in terpyridine ligand, terpy, terpy-TEMPO or terpy-
TEMPOH, were named as [Pt(terpy)(C≡CPh)](PF
Pt(terpy-TEMPO)(C≡CPh)](PF ), Complex 1;
TEMPOH)(C≡CPh)]( PF ), Complex 1’, respectively.
6
), Complex 2;
[
6
[Pt(terpy-
6
Complex 1 was prepared according to the method of
Burstall et al[11] and Lippard et al[12] as modified by our group in
synthesis of Platinum terpyridine-TEMPO complex.[13] Complex
Scheme 1. Synthetic routes and structures of alkynylplatinum(II) terpyridyl Complexes 1, 1’ and 2.
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Figure 1. UV-Vis spectra, photoluminescence spectra and EPR spectra of compelxes. A) curves of Complex 1(black) and 2 (red) was UV-Vis spectra, B) curves
of Complex 2 (blue), Complex 1 (cyan) and Complex 1’ (green) were photoluminescence spectra, C) and curves of TEMPO (violet), Complex 1 (orange), and
-
4
-1
Complex 1’(pink) were EPR spectra, all in the DMF at the concentration of 1×10 mol. L , rt.
with time. As
a co-oxidant, BAIB experienced hydrogen
Coupled Operando Spectroscopic Studies of Complex 1
in the Catalytic Reaction
abstraction from TEMPOH, forming PhI and AcOH.
During the alcohol oxidation, Complex 1 was explored to
TEMPO-mediated catalyst, as well as the bi-functional probe
with switchable signal of EPR and photoluminescence. So
fluorescence emission and EPR spectroscopic studies were
performed to visualize the catalyst species of TEMPO/TEMPOH.
Piancatelli and co-workers described an effective BAIB/TEMPO-
catalyzed oxidation of alcohols.[15] Thereby, the famous oxidation
of benzyl alcohol to benzaldehyde was revisited to demonstrate
the advantages in studying mechanism by using Complex 1
instead of TEMPO in along with BAIB as a co-oxidant, and the
mechanism of benzyl alcohol oxidation was also discussed.
Under the standard conditions, Complex 1 exhibited a high
selectivity (99%) and excellent efficiency in oxidation of benzyl
alcohol to benzaldehyde (detected by GC, Figure S8).
Figure 2. Time dependence of the intensity of EPR signals (Complex 1) and
the emission intensity of Complex 1’ during BzOH oxidation with
BAIB/Complex 1 in DMF, rt.
Through the combination of EPR and photoluminescence
techniques, Complex 1 could manifest actively EPR signal as
well as luminescence signal in the oxidation system. Here the
EPR signal of Complex 1 showed broadened and decreased but
the emission band appeared with time at maximum wavelength
The reaction rate of catalyst can be observed directly with the
aid of Complex 1 which produced the EPR signal as well as the
luminescence signal. As Figure 2 showed obviously, there were
three stages in the whole reaction. The first stage (Figure 2, 0-
5
66 nm after adding benzyl alcohol (abbreviated to BzOH),
indicating the oxidation of Complex 1 (TEMPO style) to Complex
’ (TEMPOH style), as showed in Figure 1 B, C. In the meantime,
15 min), the concentrations of Complex 1 and 1’ kept steady,
1
while benzyl alcohol was converted by the oxoammonium salt
the oxidation reaction was also evidenced from the
corresponding GC analysis (Figure S8), in which benzaldehyde
+
(
TEMPO style) which is commonly known as a kind of stronger
oxidant compare to the corresponding radical style in oxidation
of alcohols.[16,17] Our control experiments showed clearly that
(
abbreviated to BA) increased and benzyl alcohol decreased
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TEMPO or BAIB alone could not oxidize benzyl alcohol
efficiently (Table S1).
In the second stage (Figure 2, 15-45 min), the steady state
was destroyed, where the photoluminescence intensity
enhanced, and EPR intensity fell off.
situ-formed TEMPO+ species, and at the same time, TEMPO+
was reduced to another mole of TEMPOH. Two moles of
TEMPOH may be deprotonated by BAIB[19], BAIB accordingly
release the AcOH and PhI, and TEMPOH was turned to
Complex 1 (evidenced by the EPR spectrum).
In the third stage (Figure 2, 45-65 min), the concentrations of
TEMPO and TEMPOH species were in another steady state: the
EPR signal of was low intensity, and the photoluminescence
signal of was relative high intensity.
In general, the oxidation of the alcohols was closely related to
the states of catalysts, thus more information on the oxidation
mechanism of the substrate could be obtained through the
detailed changes of the catalysts.
Scheme 3. Proposed reaction pathway for alcohols oxidation by BAIB and
Complex 1.
In accordance with the established calibration curves (eqs.1
and 2, methods of measurement were in supporting information)
between the concentration and intensity in the region of 0.1-1.0
-1
mol. L , the intensities showed in Figure 2 were transformed to
corresponding concentrations in Figure 3, and the equations of
time-resolved density were fitted as eqs. (3) and (4). Where y
values referred to the intensity of EPR signal of Complex 1 in eq.
Scheme 2. The process of acid-catalysed disproportionation of nitroxyl radical
[
[
1], alcohol oxidation of BzOH [2], and reduction reaction of TEMPOH species
3].
(
1) or emission signal intensity of Complex 2 in eq. (2). C
1
, C1’
New Insights on Transformation and Termination States
of TEMPO Species in the Benzyl Alcohol Oxidation by
Complex 1/BAIB System
and C referred to the concentration of Complex 1, 1’ and 2,
respectively. Here, we have done an approximate treatment.
Because of the very similar luminescent properties of Complex
2
1' and 2, showed in Figure 1, B, we regarded approximatively
The strategies of coupled operando spectra make the
possibility to gain insight into the vital changes of
TEMPO/TEMPOH and states of termination for working catalysts
in order to know a more comprehensive mechanism in the
alcohol oxidation. There were also three key processes in the
benzyl alcohol oxidation by BAIB/TEMPO system. Firstly, Since
the calibration cure of Complex 2 (eq. 2) as Complex 1'.
As could be seen in Figure 3, the two curves were
symmetric trend but the inflection points were noticeably
different. The large change rates of TEMPOH species were
located at 21 min and 36 min. Nevertheless, for the
concentration of TEMPO species, the turning points were
+
located at 28 min and 43 min.
no TEMPO appeared at the beginning of the alcohol oxidation
2
yEPR = 0.01765+ 2.02[C ],R = 0.9959................................................ （. . 1）
reaction, it was formed by disproportionation of the nitroxyl
radical (Scheme 2, disproportionation process [1]).[18] Secondly,
the TEMPO+ species oxidized effectively alcohol, forming
aldehyde and TEMPOH species (Scheme 2, alcohol oxidation
process [2]). Thirdly, In the presence of co-oxidant (BAIB),
TEMPO was regenerated from TEMPOH, and BAIB was
reduced to PhI and AcOH (Scheme 2, regeneration reaction
process [3]).
1
2
yEmission = 0.02737 +1.34[C ],R = 0.9962........................................... （. . 2）
2
-3
3
2
2
C  (3.8 10 t -0.1014t -11.17t  205.2) / (t -60.05t 1030)........ （. . 3）
1
-
3
3
2
2
C  ( -8.0 10 t 1.283t - 67.75t 1197.3) / (t -75.26t 1532).... （. . 4）
1
'
Based on the above results, we present an integrated
reaction mechanism (Scheme 3). One mole of TEMPO species
Complex 3) and one mole of TEMPOH species (evidenced by
the emission spectrum, Figure 2) were formed from the
disproportionation of two moles of TEMPO species (Complex 1).
Then benzyl alcohol was oxidized to benzaldehyde by the in
At the point of 21 min, the concentration of TEMPOH
species went up rapidly, which revealed the TEMPO
regeneration process became slow in consuming the TEMPOH
species (Scheme 3), and then the TEMPOH species were
accumulated. However, the concentration of TEMPO species
+
(
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changed sharply at the point of 28 min, which was tardive about
example of combined EPR-photoluminescence spectra to give
an extremely direct and quantitative evidence for the
mechanistic studies in the alcohol oxidation. Hence, more
mechanistic information of reaction rate in each step of the
reaction cycle reinforced the previous proposals, and those
details of the in-situ information allow not only can
quantificationally detect the composition of working catalyst, but
also can modulate the catalytic components for increased
activity. This method highlighted the advantage of the new
combining spectroscopic methods and can be potentially applied
in other catalytic reaction in which TEMPO is used as catalyst.
7
min compared to TEMPOH species. We speculated this might
be ascribed to the delayed response of TEMPO species. For
TEMPO species, because of lack of BAIB and substrates,
regeneration process and oxidation process became slow,
whereas the disproportionation process was not affected. It
probable that regeneration process and oxidation process
maintained a balance about 7 min, later on, the balance was
destructed. Therefore, the concentration of TEMPO species was
changed dramatically at 28 min. Similarly, the difference of the t
and t was also 7 min.
2
4
Experimental Section
Materials and physical measurements
We measured the emission and UV-Vis spectra by an Edinburgh
instruments FLS 920 spectrophotometer and an analytic Shimadzu
UV/Vis spectrophotometer. EPR spectrometer used was a computer-
controlled X-band (9.5 GHz) EPR spectrometer (Bruker A300). In order
to adjust the temperature, a Bruker ER 4131VT variable temperature
accessory control unit was equipped. In this way, the temperature can be
control in accuracy of ± 0.1 K. We set typical ESR parameters as follows:
sweep width was 60 G; 9.439 GHz was the microwave frequency;
3
receiver gain was 1.59×10 ; center field was 3508 G; power was 15.99
mW; the modulation frequency was 100 kHz; the amplitude was 1 G; the
conversion time was 42 msec and time constant was 10.24 msec with 1
X-scans for each 6144-point spectrum. GC-2010 (SHIMADZU) equipped
with an automatic injector (SHIMADZU) was used to detect the alcohol
and aldehyde.
Figure 3. Time dependence of the concentrations of Complex 1 EPR signal
red), the concentrations of Complex 1’ (black) and the concentrations of
subtraction (blue) TEMPO-TEMPOH) during BzOH oxidation with
BAIB/Complex 1 in DMF, rt.
(
We recorded the UV-Vis spectra at 25 oC through a quartz cell,
Consequently, with the aid of EPR and fluorescence spectrum
during the oxidation reaction, the delicate balance of TEMPO
and TEMPOH species was visualized. This highlighted the bi-
functional role of Complex 1 and an effective catalyst in the
oxidation reaction.
emission dynamic experiments were recorded through a quartz cell at
25 C, and EPR dynamic experiments spectra were recorded at 25 o
o
C
2
through quartz capillary placed for O admission.
Synthesis of Terpy-TEMPO
Synthesis of 2,2,6,6–Tetramethyl-4- (2,2’:6’,2’’ -terpyridin-4’-yloxy)-
piperidi-1-oxyl (L, terpy-TEMPO). Ligand L was prepared by a reported
Conclusions
procedure,20 Yield 4.2 g, 90%. Melting point was located 128-130°C.
In conclusion, we designed and synthesized a bifunctional
probe which exhibited EPR signal and emission signal in a
reaction. In order to understand more about the quantitative
concentration changes of TEMPO/TEMPOH species during the
ESI-MS: [M+H]+ 404.01, 426.13. Elemental analysis calculation for
.
12 27 4
C H N O
2
: C, 71.44; H, 6.74; N, 13.90. Experiment value: C, 71.20; H,
6.70; N, 13.89.
in-situ reaction,
a strategy of coupled EPR/fluorescence
techniques was proposed.
During the alcohol oxidation by BAIB/Complex 1 system,
the two in-situ forms of TEMPO and TEMPOH species reacted
Synthesis of chlorine salt of [Pt(terpy-TEMPO)Cl]
Cl·H O·CH OH
2 3
+
with substrates and mole equivalent BAIB, respectively. By
[
Pt(terpy-TEMPO)Cl]·H
2
O·CH
3
OH was prepared by
a
reported
procedure,[
13]
Yield: 2.76 g, 96%. ESI-MS: [M-Cl] 634.5. Elemental
+
means
of
the
simultaneous
EPR-Photoluminescence
spectroscopic analysis, we could easily get the information of
the delicate balance between alcohol and BAIB. After the
reaction, the Complex 1 was terminated in the states of
TEMPOH species revealed by the emission spectrum.
2 4 5
analyses for C25H33Cl N O Pt: C, 41.72; H, 4.62; N, 7.79. Experiment
value: C, 41.76; H, 4.60; N, 7.75.
As far as we know, the alkynylplatinum(II) terpyridine-TEMPO
catalyst is a new kind of bifunctional probe, and this is the first
6
Synthesis of [Pt(terpy-TEMPO)Cl](PF )
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A 100 ml round three-necked bottle was charged with [Pt(terpy-
dependence of in-situ oxidation reactions. The electrons paramagnetic
resonance (EPR) signals of the TEMPO derive were recorded by using a
spectrometer (Bruker A300). The concentrations of samples were also
1×10-4 mol. L , except in the time-dependence of in-situ oxidation
reactions.
TEMPO)Cl]Cl·H
50 mL). The mixture is stirred and heated until the various cultures melt
together. And then added gradually NH PF (2 mmol, 0.34 g) methyl
2 3
O·CH OH (0.14 g, 0.20 mmol), and dried methyl alcohol
(
-1
4
6
alcohol solution (10 ml), immediately, the clear solution in round bottom
became turbid. Stirred the mixture for about 3 h latter, the suspension
became dark orange and the solid was completely precipitated. We
collected the product and washed with deionized water (300 ml) for 3
Typical process for oxidation of phenylcarbinol
times, and dried in vacuo, to obtain [Pt(terpy-TEMPO)Cl](PF
6
) 0.13 g,
yield 84.7%.
We chose homogeneous oxidation of benzyl alcohol as oxidation
model, and apply [Pt(terpy-TEMPO)(C≡CPh)](PF
study. In a general procedure, we added 2.2 mmol BAIB (0.71 g) to 2
mmol benzyl alcohol (0.22 g) and [Pt(terpy-TEMPO)(C≡CPh)](PF
0.085 g, 0.2 mmol) in the scale of 2 ml DMF, at 25 oC, temperature
6
) in the mechanism
6
Synthesis of [Pt(terpy-TEMPO)(C≡CPh)](PF )
6
)
(
1
.0 mmol [Pt(terpy-TEMPO)Cl](PF
mmol CuI (0.06 g) in 100 ml DMF, sealed in a 200 ml three neck flask.
The mixture was protected by a bubble filled with N . And then injected
.0 mmol phenylacetylene (0.2 ml), added 3.0 mmol triethylamine (0.3
6
) (0.78 g) was mixed with 0.3
control accuracy at ±1 oC; stirring rate: 1000 r/min; oxygen pressure: 1
atm. About 1 h latter, the reaction was completed, and then the gas
chromatography was used to analysis the composition of the mixture.
2
2
o
ml) subsequently. After stirring the mixture in 55 C for about 48 h in dark
place, the reaction mixture turned to dark brown solution. We treated the
GC analyzed methods: The assay of residual benzyl alcohol and
product were calculated according to the internal standard method, and
the ortho-nitrotoluene was added as the internal standard in the test.
mixture with Et
solids. Then we collected this solid by filtration and washed with another
0 ml Et O. At last, this solid were dried in vacuum drying oven. The
Yield was 0.67 g (96%). ESI-MS calculation for PtC32 is 699.2.
Found: 700.3. Calculations of elemental analysis for PtC32 PF
were C, 45.40; H, 3.79; N, 6.63. Experiment value: C, 44.14; H, 3.64; N,
.42.
2
O (500 ml) in three times to completely precipitate ochre
1
2
32 4 2
H N O
Acknowledgements
H N O
32 4 2
6
6
Financial support from the National Natural Science
Foundation of China (21573196, J1210042), National High
Technology Research and Development Program of China (863)
(SS2015AA020601), and Fundamental Research Funds of the
Central Universities, China, is gratefully acknowledged. The
authors sincerely acknowledge Prof. Dr. Congmin Wang for
helpful discussions. We also thank Instrumental Analysis Center
of Zhejiang University for analysis support. The authors declare
no conflict of interest.
6
Synthesis of hexafluorophosphate of [Pt(terpy)Cl](PF )
We prepared the chlorine salt complex, [Pt(terpy)Cl]Cl·2H
according to the procedures of Burstall and Lippard,[11, 12] then dissolved
the compound [Pt(terpy)Cl]Cl·2H
2
O,
2
O in water, added much excess of the
, stirred at 25 C and after the counterion metathesis, precipitates
o
NH
4
PF
6
were formed largely. We collected the products and washed the solid two
times (10 ml Et O), dried overnight in vacuum drying oven.
2
Keywords: Platinum(II) terpyridine complex • TEMPO
derivatives • Alcohol oxidation • EPR Spectroscopy •
Fluorescence Spectroscopy
6
Synthesis of [Pt(terpy)(C≡CPh)](PF )
1
.0 mmol [Pt(terpy)Cl](PF
0.06 g) in 40 ml DMF, sealed in a 100 ml three neck flask. Those
mixtures were protected by a bubble filled with N . And then injected 2.0
6
) (0.61 g) was mixed with 0.3 mmol CuI
[
1]
a) I. W. C. E. Arends, Y. X. Li, R. Ausan, R. A. Sheldon, Tetrahedron
006, 62, 6659-6665; b) P. Gamez, I. W. C. E. Arends, R. A. Sheldon, J.
(
2
2
Reedijk, Adv. Synth. Catal. 2004, 346, 805-811; c) R. A. Sheldon, I. W.
C. E. Arends, Adv. Synth. Catal. 2004, 346, 1051-1071; d) K. X. Chen,
P. F. Zhang, Y. Wang, H. R. Li, Green Chem. 2014, 16, 2344-2374; e)
A. E. Fernandes, O. Riant, K. F. Jensen, A. M. Jonas, Angew. Chem.
Int. Ed. 2016, 55, 11044-11048; f) M. Hirota, K. Furihata, T. Saito, T.
Kawada, A. Isogai, Angew. Chem. Int. Ed. 2010, 49, 7670-7672; g) L.
Jia, K. X. Chen, C. M. Wang, J. Yao, Z. R. Chen, H. R. Li, RSC Adv.
mmol phenylacetylene (0.2 ml), added 3.0 mmol triethylamine (0.3 ml)
subsequently. After stirring the mixture in 55 oC for about 48 h in dark
place, the reaction mixture turned to dark brown solution. We treated the
mixture with Et
solids. Then we collected this solid by filtration and washed with another
0 ml Et O. At last, this solid were dried in vacuum drying oven. The
Yield was 0.60 g (82%). ESI-MS calculation for PtC23 : 529.1 Found:
: C, 40.96; H,
.39; N, 6.23. Experiment value: C, 41.04; H, 2.37; N, 5.96.
2
O (500 ml) in three times to completely precipitate ochre
1
2
16 3
H N
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Entry for the Table of Contents
FULL PAPER
A
TEMPO-mediated
platinum
Lu Yin, Jiaxiang Zhang, Jia Yao, and
Haoran Li *
terpyridine complex was designed and
synthesized. This complex showed
switchable signals of EPR and
photoluminescence in situ states,
which can serve as catalyst and
bifunctional probe during the reaction.
Hereby, a method combined EPR and
fluorescence spectra was established
and applied successfully to study the
mechanism of alcohol oxidation.
Page No. – Page No.
A designed TEMPO-derivate Catalyst
with Switchable Signals of EPR and
Photoluminescence: Application in
the Mechanism of Alcohol Oxidation
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