Linear bimetallic alkynylplatinum(II) terpyridyl complexes bearing p-phenylene ethynylene oligomers: Synthesis, characterization, aggregation, and photophysical properties

Article abstract of DOI:10.1021/om500115s

The series of luminescent bimetallic alkynylplatinum(II) terpyridyl complexes [(tBu₃-tpy)PtC≡C(ArC≡C)_nPt(tBu ₃-tpy)](PF₆)₂ (I-IV; tBu₃-tpy = 4,4′,4″-tritertbutyl-2,2′:6′,2″-terpyridine, Ar

Full text of DOI:10.1021/om500115s

Article
pubs.acs.org/Organometallics
Linear Bimetallic Alkynylplatinum(II) Terpyridyl Complexes Bearing
p‑Phenylene Ethynylene Oligomers: Synthesis, Characterization,
Aggregation, and Photophysical Properties
Peng Xu, Haotian Wu, Hongxing Jia, Shifan Ye, and Pingwu Du*
Department of Materials Science and Engineering, Department of Chemistry, CAS Key Laboratory of Materials for Energy
Conversion, University of Science and Technology of China, Hefei, People’s Republic of China 230026
S
* Supporting Information
ABSTRACT: The series of luminescent bimetallic alkynyl-
platinum(II) terpyridyl complexes [(tBu3-tpy)PtCC(ArCC)n-
Pt(tBu3-tpy)](PF6)2 (I−IV; tBu3-tpy = 4,4′,4″-tritertbutyl-
2,2′:6′,2″-terpyridine, Ar = C6H2(n-hexyloxy)2-2,5), in which
two platinum(II) centers are linked by p-phenylene ethynylene
oligomers, were synthesized and characterized. Their electronic
absorption and luminescent behaviors were studied by steady-
state spectroscopy and transient spectroscopy. Concentration-
dependent emission data show that all of the complexes form
self-assembled aggregates in certain concentration ranges.
Complex IV, bearing a longer p-phenylene ethynylene oligomer,
exhibits higher propensity in comparison to I−III to form aggregates at a concentration of >1 × 10−5 M, probably resulting from
stronger metal−metal interactions and π−π stacking. All four of the complexes displayed biexponential decays with lifetimes in the
range of nanoseconds in dilute solutions.
light-emitting diodes,15 and self-assembling soft matters.16 All of
INTRODUCTION
■
these applications are considered to be closely related to long-lived
Research on photofunctional transition-metal complexes has
excited states or d8−d8 metal−metal interactions and/or π−π
stacking.17
been an active field in the past few decades.1 Among them,
platinum(II) complexes coordinated to nitrogen or phosphorus
donor atoms have been widely studied because square-planar
platinum(II) complexes exhibit rich photophysical and photo-
chemical properties.2 One early example is the binuclear
derivative [Pt2(μ-P2O5H2)4]4− (often called “platinum pop”),
showing long-lived excited states in solution, which has been
studied for various photoinduced chemical reactions such as
C−H bond cleavage of isopropyl alcohol and halogen atom
abstraction.2b Luminescent excited states were later found in
platinum(II) diimine and terpyridyl complexes, but their
lifetimes are usually short (<1 μs) in solution.3 After the first
introduction of an alkynyl group into platinum(II) diimine
complexes by Che et al. in 1994,4 their long-lived excited states
were further studied by Eisenberg et al. in 20003b and Schanze
et al. in 2001.5 Later, the same strategy was used in platinum
terpyridyl complexes by Yam et al. in 20016 and Wu et al. in
20027 to enhance the lifetime of the metal-to-ligand (MLCT)
excited states. Since then, studies on alkynylplatinum(II)
complexes have been rising.7,8
Aside from the considerable work carried out on the development
of simple monometallic alkynylplatinum(II) complexes, multi-
nuclear alkynylplatinum(II) complexes in which transition-metal
centers are connected by a rigid or flexible backbone have been
found to show very interesting properties.15a,18 The Yam group19
and the Yang group20 reported a series of multinuclear alkynyl-
platinum(II) complexes bearing a rigid branched backbone, which
showed enhanced gelation, two-photon absorption, or two-photon-
induced luminescence properties compared with mononuclear
metal complexes. The Gladysz group21 reported a series of
trans,trans-(C6F5)(R3P)2Pt(CC)nPt(PR3)2(p-tol) (R = p-tol)
complexes, which exhibited phosphorescence from triplet states
concentrated on the C4 segments. Studies on binuclear alkynyl-
platinum(II) terpyridyl complexes with double metal centers which
are bridged by long linear conjugated oligomerd are relatively
rare.18a,22 Herein, we report the synthesis, characterization,
aggregation, and photophysical properties of linear binuclear
alkynylplatinum(II) complexes bearing p-phenylene ethynylene
oligomers, in which a terpyridyl group is used as the second
ligand.
Due to significant spectral differences between the monomers
and oligomers, metal−metal interactions are frequently observed
in various transition-metal complexes, such as those of Rh(II),
Pd(II), Pt(II), and Au(I).9 As a representative class of transition-
metal complexes, alkynylplatinum(II) complexes have attracted
great interest in the applications of photocatalysis,10 colorimetric
sensors,11 luminescent sensors,12 molecular probes,13 solar cells,14
Received: February 1, 2014
© XXXX American Chemical Society
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Scheme 1. Synthesis and Photographs of the Binuclear Platinum(II) Complexes I−IV
a
Scheme 2. Synthesis of the Terminal Dialkynes 5 and 7
a
Reagents and conditions: (a) TMSA, Pd(PPh3)2Cl2, CuI, PPh3, TEA/toluene, 90 °C, 82%; (b) K2CO3, THF/CH3OH, room temperature, 92%;
(c) 9, Pd(PPh3)2Cl2, CuI, TEA/THF, 50 °C, 86%; (d) K2CO3, THF/CH3OH/DCM, room temperature, 82%.
Sonogashira coupling of alkyne 5 with a 2-fold amount of
bromide compound 11 failed. We hypothesized that bromide 11
could be replaced by the more active iodide 9 (Scheme 2).
Experiments revealed that this approach afforded the desired
product 10 under mild conditions with 86% yield. Desilylation of
compound 10 afforded terminal alkyne 7, in which CH2Cl2/
CH3OH/THF was used as the reaction medium due to its poor
solubility of 10 in CH3OH/THF mixed solvent.
RESULTS AND DISCUSSION
■
Synthesis and Characterization. The design of bimetallic
platinum(II) complexes bearing increasing lengths of p-phenyl-
ene ethynylene oligomers is shown in Scheme 1 (I−IV).
Following a modified synthesis procedure for related mono-
nuclear complexes,7,23 the facile removal of chloride from
[(N∧N∧N)PtCl] (N∧N∧N = terpyridine) and replacement by
alkynyl ligands yielded alkynylplatinum(II) complexes in
moderate to high yields with cuprous iodide as the catalyst.
Initially, a series of terminal alkyne ligands with increasing
lengths of p-phenylene ethynylene oligomers was synthesized
(Scheme 2). The expeditious synthesis of these alkynes is based
on simultaneous Sonogashira coupling at two terminal positions.
Alkoxy side chains on the p-phenylene ethynylene unit were used
to improve the solubility when the length of the rigid carbon
skeleton increased, as was done in many previous publications of
luminescent conjugated polymers.24 1,4-Bis(hexyloxy)benzene 1
was used as the starting material to synthesize compound 2,
followed by an iodination reaction to produce 1-bromo-4-
iodobenzene 3. The subsequent Sonogashira coupling of 3 with
trimethylsilylacetylene (TMSA) and removal of the TMS group
in CH3OH/THF provided the terminal alkyne 5 in 92% yield
(Scheme 2). Moreover, an endeavor was made to transform 5
into compound 10. However, synthesis of compound 10 by
Starting from compound 3, the terminal alkyne 6 was also
synthesized according to the standard Sonogashira coupling and
deprotection procedures as mentioned above (Scheme 3).
Following the strategy for synthesis of alkyne 7, alkyne 8 was
prepared with 93% yield. With the terminal dialkyne compounds
5−8 in hand, the preparation of complexes I−IV was successfully
achieved. Following a modified procedure for related
alkynylplatinum(II) terpyridyl complexes,17e,18a two platinum
terpyridyl species were capped at the end positions of these
terminal alkynes catalyzed by cuprous iodide in a mixture of
chloroform and triethylamine (TEA), giving high yields (87% for
I, 88% for II, 90% for III, and 86% for IV) (Scheme 1). All these
1
complexes have been well characterized by H NMR, FT-IR,
HRMS, and elemental analysis.
In order to obtain more structural information on complexes
I−IV, we tried to grow single crystals in many different solvents,
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a
Scheme 3. Synthesis of the Terminal Dialkynes 6 and 8
a
Reagents and conditions: (a) TMSA, Pd(PPh3)2Cl2, CuI, PPh3, TEA/THF, 35 °C, 77%; (b) (i) K2CO3, THF/CH3OH, room temperature, 93%,
(ii) 3, TMSA, Pd(PPh3)2Cl2, CuI, TEA/THF, 35 °C, 74%; (c) (i) TMSA, Pd(PPh3)2Cl2, CuI, PPh3, TEA/toluene, 90 °C, 73%; (ii) see (b), 78%;
(d) 9, Pd(PPh3)2Cl2, CuI, TEA/THF, 50 °C, 88%; (e) K2CO3, THF/CH3OH/DCM, room temperature, 93%.
such as acetonitrile, chloroform, methanol, dimethyl sulfoxide,
and dimethylformamide. However, despite many attempts to
grow crystals of complexes I−IV, we have not yet obtained high-
quality crystals suitable for X-ray single-crystal diffraction. In
contrast, using the same procedure as was attempted for
synthesis of complexes I−IV, we did succeed in synthesizing
the analogous bimetallic alkynylplatinum(II) terpyridyl complex
V (Figure 1). V has no long alkoxy side chains on the p-phenylene
respectively. The Pt−C distance is 1.972(4) Å. The above bond
distances and angles indicate the distortion from square-planar
geometry imposed by the constraints of the terpyridyl ligand.
Other bond distances and angles (see the Supporting Information
for more detailed crystal information) are similar to those of
cationic platinum(II) terpyridyl complexes reported in the
literature.6,8c,17a,18a,25 According to complex V, we assume that
complexes I−IV also have a similar slightly distorted square planar
geometry conformation (Scheme 1).
Steady-State Spectroscopy. The steady-state absorption
and emission spectra of I−V were studied in dichloromethane
(CH2Cl2) and acetonitrile (CH3CN) solutions. The absorption
and emission data are summarized in Table 1. The UV−vis
absorption spectra of I−IV in CH2Cl2 with a concentration of
1 × 10−6 M features intense absorptions at <320 nm
(B1, maximized at 287 nm for I, 263 nm for II, 261 nm for III,
260 nm for IV), moderate absorptions in the range of 300−470 nm
(B2, maximized at 339 nm with ε = 47525 dm3 mol−1 cm−1 for I,
391 nm with ε = 50408 dm3 mol−1 cm−1 for II, 406 nm with ε =
84217 dm3 mol−1 cm−1 for III, 414 nm with ε = 137070 dm3
mol−1 cm−1 for IV), and weak absorptions in the range of 430−
610 nm (B3, maximized at 537 nm with ε = 14153 dm3 mol−1
cm−1, 520 nm with ε = 19744 dm3 mol−1 cm−1, 512 nm with
ε= 27344 dm3 mol−1 cm−1, 509 nm with ε= 33547 dm3 mol−1 cm−1
for I−IV, respectively) (Table 1 and Figure 2). There are,
however, some overlaps between B1 and B2 and between B2 and
B3. The higher energy B1 bands and moderate absorption bands
B2 are tentatively ascribed to the internal ligand (IL) π−π*
((ArCC)n) (for the absorption and emission data of 5−8, see
the Supporting Information, Figures S1 and S2 and Table S1)
and π−π* (tBu3-tpy) transitions.26 The bands B3 are the
characteristic absorptions of alkynylplatinum(II) terpyridyl
complexes, which could be assigned as the [dπ(Pt)−π*(tBu3-tpy)]
metal-to-ligand charge transfer (MLCT) transition and/or the
[π(ArCC)−π*(tBu3-tpy)] ligand-to-ligand charge transfer
(LLCT) transition.16a,17b,18a,b In the visible region, the moderate
absorption bands (B2) were found to shift to lower energy (i.e.,
red shift) on going from I to IV, due to the increasing conjugated
p-phenylene ethynylene unit, which could decrease the energy
gap of HOMO−LUMO levels. However, the weak absorption
bands (B3) shift to higher energy (i.e., blue shift) from I to IV.
The lower energy absorption in complex I indicates the stronger
electronic coupling between the two platinum metal centers via
the p-phenylene ethynylene oligomer. Such an electronic coupling
Figure 1. Complex V and its single-crystal X-ray diffraction structure.
Thermal ellipsoids are shown at the 50% probability level. Anions and
hydrogen atoms have been omitted for clarity.
ethynylene unit. Red crystals of V suitable for single-crystal X-ray
diffraction were grown by the slow diffusion of diethyl ether into a
concentrated solution of V in chloroform. The molecular structure
of V is shown in Figure 1, and the crystal packing is given in
Scheme S1 in the Supporting Information. The Pt−N distances
range from 1.958(3) to 2.009(3) Å, with the central nitrogen
having the shortest distance. The N(1)−Pt−N(3) and N(2)−Pt−
C(alkyne) “trans” angles are 161.13(13) and 176.50(14)°,
C
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a
Table 1. Electronic Absorption and Emission Data for Complexes I−V
CH2Cl2
CH3CN
λabs (nm) (ε (dm3 mol−1 cm−1)) λem (nm) (τ (ns) )
b
c
d
b
c
e
complex λabs (nm) (ε (dm3 mol−1 cm−1))
λem (nm) (τ (ns) )
Φem
Φem
I
339 (47525), 537 (14153)
391 (50408), 520 (19744)
406 (84217), 512 (27344)
414 (137070), 509 (33547)
f
674 (0.6, 8.8), 707 (0.5, 11.8)
657, 673 (0.8, 7.2), 717 (0.4, 5.7)
652 (0.8, 7.5), 717 (0.6, 28.9)
653 (0.3, 8.3), 719 (0.6, 30.0)
0.0019
0.028
0.022
0.15
338 (43462), 508 (12405)
385 (43375), 485 (20879)
404 (67312), 481 (28217)
410 (83911), 478 (30751)
560 (4.1)
7.8 × 10−5
4.0 × 10−5
4.1 × 10−5
2.4 × 10−3
1.8 × 10−3
II
III
IV
V
563 (0.5, 4.2)
561 (0.5, 4.2)
557 (1.0, 6.7)
646 (19.8)
f
f
466 (10678)
a
b
c
d
Data obtained at 298 K (concentration 1 × 10−6 M). λex 500 nm. λex 450 nm. Luminescence quantum yield was measured by the
e
f
reported method in refs 7, 8, and 27 and using a degassed CH2Cl2 solution of [Ru(bpy)3](PF6)2 as the reference. CH3CN solution was used. Not
measured.
Figure 3. Normalized emission spectra of complexes I−IV in CH2Cl2
(top) and CH3CN (bottom) at 298 K at a concentration of 1 × 10−6
(λex 500 nm).
M
Figure 2. Normalized absorption spectra of complexes I−IV in CH2Cl2
(top) and CH3CN (bottom) at 298 K (concentration 1 × 10−6 M).
interaction decreases in IV because of the long distance between
the two Pt(II) metal centers, as evidenced by the observed blue
shift of the low-energy absorption band. The tendency of
absorption features with a concentration of 1 × 10−6 M in
CH3CN is similar to that in CH2Cl2 (Figure 2). More detailed
absorption spectraof complexes I−V with different concentrations
in CH3CN are shown in Figure S3 and Figures S4a−S6a
(Supporting Information). Table 1 summarizes the absorption data
of those complexes.
suggests that the peaks in complex I can be assigned as metal-
to-ligand charge transfer (3MLCT) and alkynyl-to-terpyridine ligand-
to-ligand charge transfer (3LLCT) transitions. When the length of
the molecular bridge between the two platinum(II) metal centers is
increased, the high-energy emission band shows a significant
blue shift from I to III, which is consistent with the blue shift of
the low-energy absorption bands (B3) in the visible region. There is
no significant difference between III and IV. It seems the emission
spectrum of complex II is the combination of complex I and
complexes III and IV, indicating that the frontier energy levels
change from I to III and IV via II. With the increasing length of the
conjugated dialkyne ligands, the acetylide-based LUMO will be
decreased, resulting in more pronounced intraligand (IL) π−π*
transitions and the disappearance of MLCT transitions. According
to previous work,16a,18a,29 the emission double peaks of complexes I
could be tentatively assigned as MLCT and LLCT transitions. The
emission peaks of complexes II could be tentatively assigned as
MLCT, LLCT, and IL π−π* transitions. The emission peaks of
complexes III and IV could be tentatively assigned as LLCT and IL
π−π* transitions. However, in the more polar solvent CH3CN,
upon excitation at the same wavelength, the multiple emission peaks
Excitation of complexes I−IV at 500 nm in CH2Cl2 with a
concentration of 1 × 10−6 M leads to emission spectra in the
range 625−765 nm. The photoluminescence quantum yields
(Φem) were determined by using a degassed CH2Cl2 solution of
[Ru(bpy)3](PF6)2 as the reference (Table 1).27 Interestingly, all
these complexes show multiple emission peaks (maximized at
674 and 707 nm for I with Φem = 0.0019, at 657, 673, and 717 nm
for II with Φem = 0.028, at 652 and 717 nm for III with Φem
=
0.022, and at 653 and 719 nm for IV with Φem = 0.15) and the
higher energy band (the left peak) is more intense than the lower
energy (the right peak) (Figure 3 and Table 1). Previously pub-
lished work on alkynylplatinum(II) terpyridyl complexes7,24a,25b,28
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turn into a single peak in the range 520−670 nm (maximized at
analogous alkynylplatinum(II) complexes.11,16b,18a However,
upon further increasing the number of p-phenylene ethynylene
units, the aggregation does occur in the present system. The
appearance of the new emission band of complex IV suggests that
the conjugated linear backbone has a strong propensity to
aggregate, and thus it increases intermolecular interactions.
The above observation was further confirmed by concen-
tration-dependent experiments in CH3CN. Different concen-
trations of complexes I−IV were prepared, ranging from 1 × 10−6
to 1 × 10−4 M, and the emission spectra of each concentration
were recorded. As shown in Figure 5 for complexes I and IV,
560 nm for I with Φem = 7.8 × 10−5, at 563 nm for II with Φem
=
4.0 × 10−5, at 561 nm for III with Φem = 4.1 × 10−5, and at 557 nm
for IV with Φem = 2.4 × 10−3). Only a negligible emission peak
maximized at ∼585 nm could be observed (Figure 3). These results
indicate that the polarity of the solvents has a significant effect on the
HOMO−LUMO gap in these Pt(II) complexes.3a,30 The emission
data of V are also shown in Table 1.
Aggregation Properties. With the increase of concen-
tration from 1 × 10−6 to 1 × 10−5 M in acetonitrile, complexes
I−IV have very similar low-energy absorption bands, as shown in
Figure 4. Interestingly, unlike the case for the absorption spectra,
Figure 4. Absorption spectra (top) and emission spectra (bottom) of
complexes I−IV in CH3CN at 298 K (concentration 1 × 10−5 M, λex
500 nm).
Figure 5. Normalized emission spectra of complexes I (top) and IV
(bottom) at different concentrations in CH3CN at 298 K (λex 500 nm).
complex IV exhibits very different emission properties from
I−III in the same solvent at 1 × 10−5 M. The emission band of
complex IV between 520 and 670 nm dramatically dropped with
an increase of concentration. Instead, a new broad band between
650 and 850 nm maximized at 780 nm appeared. The obvious
emission change of IV in solutions is believed to result from the
formation of aggregates at a high concentration,24a,26 indicating
that the longer p-phenylene ethynylene oligomers facilitate
stronger intermolecular interactions. The origin of the low-
energy emission band might be from Pt···Pt interactions and/or
π−π stacking, a typical feature of platinum(II) terpyridyl
complexes.2a,6,12 The emission band maximized at 780 nm was
tentatively assigned to be from states of a triplet metal−metal-to-
ligand charge transfer (3MMLCT) transition.19,24a,26
As observed in both CH2Cl2 and CH3CN at the concentration
1 × 10−5 M, no significant Pt···Pt and/or π−π interaction
occurred from I to III owing to the sterically bulky tert-butyl
groups on the terpyridyl ligand, which might prevent the
molecules from coming close to each other. Yam et al. have
reported that the bulky terpyridine ligand could hinder the
occurrence of Pt···Pt interactions and/or π−π stacking in
when the concentration increases, the intensity of the high-
energy emission band sharply decreases accompanied by an
increase in the low-energy band. At the concentration of 2 × 10−5 M
for complex I, there is only a small change for the high-energy
emission band in the range 520−670 nm. Surprisingly, at a
concentration of 2 × 10−5 M for complex IV, the high-energy
band in the range 520−670 nm almost disappeared and a broad
emission band in the low-energy region dominated the emission
spectra, indicating that strong aggregation occurred. With a
further increase in the concentration to 2 × 10−5 M, similar
aggregation behaviors were also observed for complexes II and
III (Figures S4 and S5, Supporting Information). For instance,
with a concentration of 2 × 10−5 M, a significant 3MMLCT emission
band was observed for complex I starting at approximately 638 nm
and maximized at 792 nm (Figure 5). When the concentration was
increased to 1 × 10−4 M, the high-energy emission band in the range
3
520−670 nm was replaced by a broad low-energy MMLCT
emission band. The emission spectra of aggregated complexes II and
III in high concentrations are similar to that of complex I and are
given in Figures S3 and S4 (Supporting Information). However, the
formation of aggregates of complex V was not observed even at a
E
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Figure 6. Luminescent decay profiles of complex IV in CH3CN at 298 K at different concentrations: (a) 1 × 10−6 M; (b, c) 1 × 10−4 M. The red lines are
the fitting curves.
concentration of 1 × 10−4 M, which indicates that the electron-
donating alkoxy side chains in complexes I−IV significantly
promoted the Pt···Pt π−π stacking interactions (Figure S6,
Supporting Information).
at 1 × 10−6 M (Table 1 and Figures S13 and S14 (Supporting
Information)).
At a higher concentration, luminescent decays of those
complexes show different lifetimes, probably because of the
formation of self-assembled aggregates. For instance, complex IV
shows two lifetimes at τ1 = 1.0 ns and τ2 = 6.7 ns with a
concentration of 1 × 10−6 M at 557 nm in deaerated CH3CN
solution but it shows τ1 = 0.5 ns and τ2 = 3.1 ns with a
concentration of 1 × 10−4 M at the same wavelength (Figure 6a,b).
Meanwhile, a new single-exponential decay (τ = 0.3 ns) at 775 nm
was observed (Figure 6c), which might be a feature originating from
the aggregates under these conditions. A similar change in emission
lifetime was also observed in complex I in the lower energy region
(Figures S13 and S15 (Supporting Information)).
Luminescent Decays. Emission lifetime measurements
were performed using a nanosecond pulsed laser system
conducted in CH2Cl2 or CH3CN solution at room temperature.
With a concentration of 1 × 10−6 M in deaerated CH2Cl2
solution, excited at 450 nm, all of the binuclear alkynylplatinum-
(II) terpyridyl complexes I−IV show biexponential decays
(Table 1 and Figures S7−S10 (Supporting Information)). For
example, at 674 nm, complex I shows two lifetimes at τ1 = 0.6 ns
and τ2 = 8.8 ns, while at 707 nm lifetimes are seen at τ1 = 0.5 ns
and τ2 = 11.8 ns. At the same concentration, when measurements
are conducted in deaerated CH3CN solution, complexes II−IV
also show biexponential decays with lifetimes in the range of
nanoseconds (Figure 6 and Figures S11 and S12 (Supporting
Information)). Similar biexponential decays were observed in
some other alkynylplatinum(II) complexes at 77 K reported by
Chong et al.31 The biexponential decays τ1 and τ2 of compound I
in CH2Cl2 could be tentatively ascribed to originate from
simultaneous luminescence from MLCT and LLCT states,
respectively. Due to the tentative assignments of the multiple
emission bands in compounds III and IV, the biexponential
decays τ1 and τ2 of these two compounds could be ascribed to
originate from simultaneous luminescence from LLCT and IL
π−π* transition states, respectively. As for compound II, the two
high-energy emission bands are strongly overlapped and the
biexponential decays τ1 and τ2 are fitted with the experimental
data, probably resulting from mixed MLCT, LLCT, and IL π−π*
transitions. All the lifetimes τ1 are shorter than τ2, which could be
attributed to the luminescent decay rate of one excited state
being faster than the other. However, complexes I and V are
different from II−IV and show single-exponential decay (τ = 4.1 ns
at 560 nm for I and τ = 19.8 ns at 646 nm for V) in acetonitrile
CONCLUSION
■
In conclusion, a series of p-phenylene ethynylene oligomers were
prepared. On the basis of these dialkynes, four binuclear
alkynylplatinum(II) terpyridyl complexes were synthesized and
characterized. Their luminescent properties and aggregation
behaviors were probed by UV−vis spectroscopy and lumines-
cence spectroscopy. The UV−vis spectra show that the polarity
of the solvents has a slight effect on the absorption spectra but
exhibits a significant effect on the emission spectra in these Pt(II)
complexes. Being promoted by the electron-donating alkoxy
groups, intermolecular aggregation could be observed for all
these complexes I−IV even in the presence of bulky tert-butyl
groups. Concentration-dependent emission spectra show the
appearance of a broad low-energy emission band when the
concentration increases, accompanied by a decrease of the high-
energy emission band. The emission spectra also show that
complex IV has the highest propensity to form aggregates due to
its longer p-phenylene ethynylene oligomer ligand. Therefore,
the length of the molecular bridge and concentration in solution
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(M + Na)+. 1H NMR (CDCl3, 400 MHz): δ 0.89 (12H, m), 1.34 (16H,
m), 1.49 (8H, m), 1.82 (8H, m), 3.35 (2H, s), 3.99 (8H, m), 6.97 (2H,
s), 6.98 (2H, s). 13C NMR (CDCl3, 75 MHz): δ 14.2, 22.7, 22.8, 25.7,
25.8, 29.3, 29.4, 31.66, 31.72, 69.7, 69.8, 80.1, 82.5, 91.4, 112.8, 114.9,
117.2, 118.0, 153.5, 154.3. FT-IR (KBr): νmax 3285, 2958, 2940, 2923,
2871, 2852, 1499, 1470, 1385, 1274, 1218, 1197, 1058, 1026, 993,
861, 647 cm−1.
Synthesis of 7. While a mixture of DCM/THF/MeOH (1/1/1,
v/v) was used as the reaction solvent, desilylation procedures similar to
those for 5 were adopted to give a yellow solid in 82% yield. ESI-MS
(m/z): 949.75 (M + Na)+. 1H NMR (CDCl3, 400 MHz): δ 0.89 (18H,
m), 1.34 (24H, m), 1.50 (12H, m), 1.83 (12H, m), 3.35 (2H, s), 4.00
(12H, m), 6.98 (2H, s), 6.99 (2H, s), 7.00 (2H, s).
Synthesis of 8. Desilylation procedures similar to those for 7 were
adopted to give a yellow solid in 93% yield. ESI-MS (m/z): 1249.83
(M + Na)+. 1H NMR (CDCl3, 400 MHz): δ 0.90 (24H, m), 1.34 (32H,
m), 1.50 (16H, m), 1.83 (16H, m), 3.341 (2H, s), 4.01 (16H, m), 6.98
(2H, m), 7.00 (2H, s), 7.008 (2H, s), 7.012 (2H, s). 13C NMR (CDCl3,
100 MHz): δ 14.2, 22.7, 22.8, 25.75, 25.80, 25.82, 29.30, 29.40, 29.45,
31.68, 31.75, 31.76, 69.78, 69.84, 69.86, 69.91, 82.4, 91.4, 91.73, 91.74,
112.7, 114.4, 114.6, 115.2, 117.4, 117.5, 118.1, 153.5, 153.67, 153.70,
154.3. FT-IR (ATR): νmax 3312, 2944, 2198, 2105, 1598, 1496, 1469,
1385, 1275, 1221, 1061, 1035, 861, 735 cm−1.
Synthesis of 10. To a degassed solution of 5 (374 mg, 1.1 mmol)
and 9 (1.35 g, 2.7 mmol) in THF (20 mL) and Et3N (20 mL) were
added Pd(PPh3)2Cl2 (84 mg, 0.12 mmol) and CuI (23 mg, 0.12 mmol).
The resulting mixture was degassed for another 5 min and stirred
overnight at 50 °C under an argon atmosphere. After completion of the
reaction, the solvent was removed in vacuo. The residue was purified by
flash chromatography on silica gel (PE/DCM) to give 10 (1.05 g, 86%)
as a yellow solid. 1H NMR (CDCl3, 300 MHz): δ 0.26 (18H, s), 0.90
(18H, m), 1.34 (24H, m), 1.51 (12H, m), 1.82 (12H, m), 3.99 (12H, m),
6.94 (2H, s), 6.96 (2H, s), 6.99 (2H, s).
Synthesis of 11. 3 (7.25 g, 15 mmol), PPh3 (238 mg, 0.91 mmol),
THF (100 mL), and Et3N (60 mL) were added to a modified Schlenk
tube with a stir bar. The mixture was stirred and degassed with argon for
20 min, followed by the addition of Pd(PPh3)2Cl2 (317 mg, 0.45 mmol),
CuI (171 mg, 0.90 mmol), and (trimethylsilyl)acetylene (1.5 g, 15.3 mmol).
After the Teflon screw valve was closed, the contents of the tube were heated
at 35 °C and stirred for 30 h. More alkyne (0.4 g, 4.1 mmol) was added, and
stirring was continued for another 36 h to complete the reaction (as observed
by TLC). Then the mixture was cooled and the solvents were removed
under reduced pressure. Water was added to the residue, and this solution
was extracted with DCM. The combined organic layers were dried over
anhydrous MgSO4, filtered, and concentrated. The residue was purified by
flash chromatography on silica gel (PE/DCM) to give 11 (5.24 g, 77%) as an
oil. 1H NMR (CD2Cl2, 400 MHz): δ 0.24 (9H, s), 0.91 (6H, m), 1.34 (8H,
m), 1.49 (4H, m), 1.77 (4H, m), 3.94 (4H, m), 6.94 (1H, s), 7.07 (1H, s).
Synthesis of 1-Bromo-4-ethynyl-2,5-bis(hexyloxy)benzene
(12). Preparation of the title compound followed the same procedure
as for compound 5 (93%). 1H NMR (CDCl3, 300 MHz): δ 0.90 (6H,
m), 1.33 (8H, m), 1.48 (4H, m), 1.79 (4H, m), 3.29 (1H, s), 3.96 (4H, q,
J = 6.6 Hz), 6.97 (1H, s), 7.08 (1H, s). FT-IR (KBr): νmax 3285, 2924,
2858, 2099, 1490, 1464, 1378, 1267, 1215, 1071, 1044, 1016, 995, 939,
858, 754, 729 cm−1.
were found to play important roles in Pt···Pt and/or π−π
interactions.
EXPERIMENTAL SECTION
■
General Considerations. Solvents were dried by conventional
methods and distilled under nitrogen prior to use. [Pt(tBu3-tpy)Cl]-
(PF6),32 1,33 and 934 were synthesized following the literature
procedure. Compounds 2,35 3,36 4,37 5,37 7,38 10,38 11,36 and 1239
were synthesized by using modified literature procedures and
1
characterized by H NMR spectroscopy, mass spectrometry, and/or
FT-IR data, which were consistent with literature data. All platinum(II)
complexes have been successfully characterized by 1H NMR and FT-IR
spectroscopy, elemental analysis, and HRMS. IR spectra were recorded on
an FT-IR (Nicolet iS10) instrument. High-resolution mass spectral
(HRMS) analyses were carried out using MALDI-TOF-MS techniques.
NMR spectra were recorded in CDCl3 using TMS as the internal
reference. Reference peaks for CD2Cl2 and CD3CN in 1H NMR were set
at 5.32 and 1.94 ppm, respectively. Coupling constants (J) are given in Hz.
Flash chromatography was performed on silica gel (300−400 mesh).
Synthesis of 2-Bromo-1,4-bis(hexyloxy)benzene (2). To a
stirred solution of 1 (5.23 g, 18.8 mmol) in dichloromethane (DCM,
90 mL) was added Br2 (1.45 mL, 28.3 mmol). After it was stirred at
room temperature overnight, the reaction mixture was quenched by
addition of water. The organic layer was removed, and the aqueous layer
was extracted with DCM. The combined organic layers were washed
with aqueous solution of sodium sulfite (saturated), dried over
anhydrous MgSO4, filtered, and concentrated. The crude product was
purified by flash chromatography on silica gel (PE/DCM) to afford 2
(6.24 g, 93%). 1H NMR (CDCl3, 400 MHz): δ 0.90 (6H, m), 1.34 (8H,
m), 1.46 (4H, m), 1.77 (4H, m), 3.88 (2H, t, J = 6.8 Hz), 3.95 (2H, t, J =
6.8 Hz), 6.80 (2H, m), 7.10 (1H, d, J = 2.4 Hz).
Synthesis of 3. To a stirred solution of 2 (8.55 g, 24 mmol) in HOAc
(100 mL) and water (10 mL) were added NaCl (5.6 g, 95.8 mmol), KI
(10 g, 60.2 mmol), and NaIO4 (10.2 g, 47.7 mmol) successively at room
temperature, and the mixture was then heated to 75 °C for 72 h. After it
was cooled to room temperature, the reaction mixture was quenched by
the addition of water. The mixture was extracted with DCM. The
combined organic layers were washed with an aqueous solution of
sodium sulfite (saturated), dried over anhydrous MgSO4, filtered, and
concentrated. The residue was purified by flash chromatography on
1
silica gel (PE/DCM) to afford 3 (10.15 g, 88%) as a white solid. H
NMR (CDCl3, 300 MHz): δ 0.91 (6H, m), 1.35 (8H, m), 1.49 (4H, m),
1.80 (4H, m), 3.94 (4H, m), 6.98 (1H, s), 7.28 (1H, s).
Synthesis of 4. 2 (2.4 g, 5.0 mmol), PPh3 (0.16 g, 0.61 mmol),
toluene (50 mL), and Et3N (25 mL) were added to a modified Schlenk
tube with a stir bar. The mixture was stirred and degassed with argon for
20 min, followed by the addition of Pd(PPh3)2Cl2 (0.213 g, 0.30 mmol),
CuI (0.213 g, 1.1 mmol), and (trimethylsilyl)acetylene (1.7 mL, 12 mmol).
After the Teflon screw valve was closed, the contents of the tube were
heated at 90 °C and stirred for 48 h. Then the contents were cooled and the
solvents were removed under reduced pressure. Water was added to the
residue, and this solution was extracted with DCM. The combined organic
layers were dried over anhydrous MgSO4, filtered, and concentrated. The
residue was purified by flash chromatography on silica gel (PE/DCM) to
give 4 (1.92 g, 82%) as a yellowish solid. 1H NMR (CDCl3, 300 MHz): δ
0.25 (18H, s), 0.90 (6H, m), 1.33 (8H, m), 1.50 (4H, m), 1.78 (4H, m),
3.94 (4H, t, J = 6.3 Hz), 6.89 (2H, s).
Synthesis of 5. 4 (1.3 g, 2.8 mmol) was dissolved in a mixture of
THF and CH3OH (100 mL, 1/1, v/v). Powdered potassium carbonate
(1.5 g, 10.9 mmol) was added in one portion, and the reaction mixture
was stirred at room temperature overnight. The reaction mixture was
diluted with DCM and washed with water. The organic layer was dried
over MgSO4, and the solvent was removed in vacuo. The crude product
was purified by chromatography on silica gel (PE/DCM) to give 5 (829
mg, 92%) as a yellowish solid. 1H NMR (CDCl3, 300 MHz): δ 0.90 (6H,
m), 1.33 (8H, m), 1.46 (4H, m), 1.80 (4H, m), 3.33 (2H, s), 3.97 (4H, t,
J = 6.6 Hz), 6.95 (2H, s).
Synthesis of 13. To a degassed solution of 12 (2.39 g, 6.27 mmol)
and 3 (2.75 g, 5.69 mmol) in THF (40 mL) and Et3N (30 mL) were
added Pd(PPh3)2Cl2 (160 mg, 228 mmol) and CuI (55 mg, 289 mmol).
The resulting mixture was degassed for another 5 min and stirred
overnight at 35 °C under an argon atmosphere for 3 days. After
completion of the reaction, solvent was removed in vacuo. The residue
was purified by flash chromatography on silica gel (PE/DCM) to give 13
1
(3.1 g, 74%) as a yellow solid. ESI-MS (m/z): 759.33 (M + Na)+. H
NMR (CDCl3, 300 MHz): δ 0.89 (12H, m), 1.34 (16H, m), 1.51 (8H,
m), 1.82 (8H, m), 3.98 (8H, m), 7.00 (2H, s), 7.09 (2H, s). 13C NMR
(CDCl3, 75 MHz): δ 14.2, 22.72, 22.75, 25.75, 25.79, 29.30, 29.33,
31.65, 31.70, 70.0, 70.2, 90.1, 113.0, 113.4, 117.8, 118.3, 149.6, 154.1.
FT-IR (KBr): νmax 3078, 3043, 2955, 2943, 2926, 2866, 1502, 1468,
1411, 1385, 1271, 1212, 1036, 981, 938, 868, 856 cm−1.
Synthesis of 6. Desilylation procedures similar to those for 5 were
adopted to give a yellow solid in 78% yield. ESI-MS (m/z): 649.67
G
dx.doi.org/10.1021/om500115s | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Synthesis of 1,2-Bis(2,5-bis(hexyloxy)-4-((trimethylsilyl)-
ethynyl)phenyl)ethyne (14). Preparation of the title compound
followed the same procedure as for compound 4 (73%). ESI-MS (m/z):
793.58 (M + Na)+. 1H NMR (CDCl3, 400 MHz): δ 0.26 (18H, s), 0.89
(12H, m), 1.34 (16H, m), 1.51 (8H, m), 1.81 (8H, m), 3.96 (4H, t, J =
6.4 Hz), 3.99 (4H, t, J = 6.4 Hz), 6.93 (2H, s), 6.95 (2H, s). 13C NMR
(CDCl3, 75 MHz): δ 1.2, 14.17, 14.22, 22.8, 25.80, 25.86, 29.4, 29.5,
31.7, 31.8, 69.6, 69.8, 91.5, 100.2, 101.3, 113.8, 114.6, 117.1, 117.5,
153.5, 154.3. FT-IR (KBr): νmax 2956, 2938, 2858, 2154, 1506, 1466,
1423, 1386, 1273, 1248, 1231, 1210, 1050, 1031, 897, 863, 843 cm−1.
Synthesis of 15. Preparation of the title compound followed the
same procedure as for compound 10 (88%). ESI-MS (m/z): 1394.03
(M + Na)+. 1H NMR (CDCl3, 400 MHz): δ 0.26 (18H, s), 0.90 (24H,
m), 1.34 (32H, m), 1.52 (16H, m), 1.83 (16H, m), 3.99 (16H, m), 6.94
(2H, m), 6.96 (2H, s), 6.998 (2H, s), 7.002 (2H, s). 13C NMR (CDCl3,
75 MHz): δ 0.1, 14.17, 14.21, 22.8, 25.79, 25.82, 25.9, 29.39, 29.43, 29.5,
31.8, 69.6, 69.8, 91.6, 91.69, 91.71, 100.2, 101.3, 113.8, 114.36, 114.44,
114.7, 117.1, 117.4, 117.5, 153.5, 153.6, 154.3. FT-IR (KBr): νmax 2951,
2926, 2859, 2152, 1510, 1467, 1426, 1385, 1274, 1249, 1211, 1046, 899,
860, 841, 758 cm−1.
General Synthesis of Binuclear Alkynylplatinum(II) Terpyr-
idyl Complexes. To a degassed solution of diterminal alkyne 5 (15 mg,
0.046 mmol) and [Pt(tBu3-tpy)Cl](PF6) (73 mg, 0.094 mmol) in
CHCl3 (10 mL) and Et3N (5 mL) was added CuI (3 mg, 0.016 mmol).
The resulting mixture was degassed for another 5 min and stirred for
24 h in the dark at room temperature under an argon atmosphere.
Solvent was removed in vacuo, and the residue was dispersed in
CH3OH. Then NH4PF6 (30 mg, 0.184 mmol) dissolved in deionized
water (20 mL) was added to the solution, which was sonicated for 5 min.
Finally, the precipitate was filtered out and washed with water and ethyl
ether to afford I (72 mg, 87%) as a black solid (Scheme 1).
2957, 2932, 2870, 2195, 2115, 1618, 1557, 1510, 1467, 1427, 1392,
1372, 1273, 1257, 1212, 1123, 1028, 845 cm−1; MS (MALDI-TOF-
HRMS with DHB as matrix) calcd for [(C136H182N6O8Pt2)2+ + 1e]+
2417.3309, found 2417.3682. Anal. Calcd for C136H182F12N6O8P2Pt2·
3MeOH: C, 59.27; H, 7.03; N, 2.96. Found: C, 59.17; H, 7.22; N, 2.73.
V: red solid, NaClO4 was used to precipitate the product, yield 86%;
−
ESI-MS (m/z) 658.6 (M − 2ClO4 ); 1H NMR (CD2Cl2, 400 MHz) δ
1.49 (36H, s), 1.50 (18H, s), 7.49 (4H, s), 7.71 (4H, d, J = 6.0 Hz), 8.19
(4H, s), 8.25 (4H, s), 9.22 (4H, d, J = 6.4 Hz); 13C NMR (CD3CN, 100
MHz) δ 30.3, 30.7, 37.1, 38.1, 101.2, 104.8, 122.4, 124.3, 126.2, 126.9,
132.7, 154.9, 155.1, 159.9, 168.0, 168.5; FT-IR (ATR) νmax 3078, 2962,
2909, 2872, 2115, 1617, 1556, 1482, 1423, 1402, 1371, 1256, 1088, 867,
840 cm−1. Anal. Calcd for C64H74Cl2N6O8Pt2: C, 50.69; H, 4.92; N, 5.54.
Found: C, 50.87; H, 4.76; N, 5.33.
X-ray Structural Determinations of [(tBu3-tpy)PtCCArC
CPt(tBu3-tpy)](ClO4)2 (V; Ar = 1,4-Phenyl). Red crystals suitable for
single-crystal X-ray diffraction were grown by the slow diffusion of
diethyl ether into a concentrated solution of V in chloroform. The
crystal (0.25 × 0.22 × 0.20 mm3) was placed onto the tip of a glass
fiber and mounted on a Bruker SMART APEX II CCD Platform
diffractometer for data collection at 100(2) K.40 Data collection was
carried out using Mo Kα radiation (graphite monochromator) with a
frame time of 90 s and a detector distance of 5.00 cm. The initial sets of
frames were oriented such that orthogonal wedges of reciprocal space
were surveyed. The space group was assigned as P21/c for V. The
structure was determined by direct methods and refined by employing
full-matrix least squares on F2 (Bruker-AXS, SHELXTL-97).41 All non-
hydrogen atoms were refined with anisotropic displacement parameters.
All hydrogen atoms were placed in ideal positions and refined as riding
atoms with relative isotropic displacement parameters. The final full-
matrix least-squares refinement converged to R1 = 0.0382 (F2, I > 2σ(I))
and wR2 = 0.0756 (F2, all data).
Compounds II−IV were prepared by a procedure similar to that for
compound I.
1
I: dark red solid, yield 87%; H NMR (CD3CN, 300 MHz) δ 0.80
ASSOCIATED CONTENT
■
(6H, m), 1.30 (12H, m), 1.47 (36H, s), 1.55 (18H, s), 1.87 (4H, m),
4.10 (4H, m), 7.07 (2H, m), 7.73 (4H, m), 8.34 (8H, m), 9.21 (4H, m);
13C NMR (DMSO-d6, 75 MHz) δ 13.9, 22.2, 25.4, 29.7, 30.3, 31.6, 36.2,
37.2, 68.6, 99.8, 105.0, 114.9, 116.4, 121.4, 123.6, 125.2, 153.3, 153.5,
153.7, 158.5, 166.2, 166.9; FT-IR (ATR) νmax 3115, 3058, 2953, 2113,
1616, 1558, 1495, 1469, 1427, 1402, 1365, 1256, 1200, 1123, 1025, 874,
852, 831 cm−1; MS (MALDI-TOF-HRMS with DHB as matrix) calcd
for [(C76H98N6O2Pt2)2+ + 1e]+ 1516.7041, found 1516.5025. Anal.
Calcd for C76H98F12N6O2P2Pt2: C, 50.50; H, 5.46; N, 4.65. Found:
C, 50.86; H, 5.15; N, 4.32.
S
* Supporting Information
Figures, tables, and a CIF file giving NMR spectra of 2−8, 10−
15, and I−V, X-ray crystallographic data of V, absorption and
emission spectra of 5−8 and I−V, and luminescent decay data of
I−V. This material is available free of charge via the Internet at
http://pubs.acs.org.
AUTHOR INFORMATION
■
II: dark red solid, yield 88%; 1H NMR (CD3CN, 300 MHz) δ 0.80
(6H, m), 0.92 (6H, m), 1.28 (16H, m), 1.38 (8H, s), 1.46 (36H, s), 1.43
(18H, s), 1.85 (8H, m), 4.03 (8H, m), 6.95 (2H, s), 7.07 (2H, m), 7.70
(4H, m), 8.30 (8H, m), 9.17 (4H, m); 13C NMR (DMSO-d6, 100 MHz)
δ 13.8, 13.9, 22.2, 22.4, 25.3, 29.0, 29.8, 30.3, 31.2, 31.9, 36.2, 37.2, 68.4,
69.0, 91.2, 99.1, 106.7, 111.3, 114.7, 117.1, 117.8, 121.1, 123.5, 125.1,
152.8, 153.2, 153.4, 153.7, 158.1, 166.1, 167.0; FT-IR (ATR) νmax 3116,
3066, 2957, 2928, 2870, 2192, 2112, 1668, 1616, 1556, 1502, 1468,
1419, 1373, 1254, 1206, 1123, 1027, 839 cm−1; MS (MALDI-TOF-
HRMS with DHB as matrix) calcd for [(C96H126N6O4Pt2)2+ +1e]+
1816.9131, found 1816.9128. Anal. Calcd for C96H126F12N6O4P2Pt2·
MeOH: C, 54.44; H, 6.12; N, 3.93. Found: C, 54.16; H, 5.77; N, 4.27.
III: dark red solid, yield 90%; 1H NMR (CD2Cl2, 400 MHz) δ 0.85
(6H, t, J = 7.2 Hz), 0.92 (12H, m), 1.36 (24H, m), 1.50 (36H, s), 1.54
(12H, s), 1.59 (18H, s), 1.89 (12H, m), 4.08 (12H, m), 7.03 (2H, s),
7.04 (2H, s), 7.07 (2H, s), 7.70 (4H, dd, J = 6.0 Hz, J = 2.0 Hz), 8.11 (4H,
d, J = 1.6 Hz), 8.16 (4H, s), 9.34 (4H, d, J = 6.0 Hz); FT-IR (ATR) νmax
3116, 3061, 2955, 2931, 2869, 2194, 2117, 1617, 1557, 1508, 1468,
1423, 1393, 1375, 1275, 1255, 1208, 1032, 873, 837 cm−1; MS (MALDI-
TOF-HRMS with DHB as matrix) calcd for [(C116H154N6O6Pt2)2+ + 1e]+
2117.1220, found 2117.2197. Anal. Calcd for C116H154F12N6O6P2Pt2: C,
57.84; H, 6.44; N, 3.49. Found: C, 57.47; H, 6.09; N, 3.84.
Corresponding Author
*E-mail for P.D.: dupingwu@ustc.edu.cn.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was financially supported by the National Natural
Science Foundation of China (Grant No. 21271166), the
Fundamental Research Funds for Central Universities (Grant
Nos. WK2060140015, WK2060190026), the Program for New
Century Excellent Talents in University (NCET), and the
Thousand Young Talents Program. The authors wish to thank
Professor Jun Jiang at University of Science and Technology of
China for helpful discussions. Professor Rui Cao from Renmin
University of China is gratefully acknowledged for X-ray data
collection. The authors thank the anonymous reviewers for their
valuable comments and suggestions to improve the paper.
REFERENCES
■
IV: bright red solid, yield 86%; 1H NMR (CD2Cl2, 400 MHz) δ 0.88
(24H, m), 1.38 (32H, m), 1.50 (36H, s), 1.55 (18H, s), 1.59 (16H, m),
1.88 (16H, m), 4.08 (16H, m), 7.05 (8H, m), 7.70 (4H, s), 8.11 (4H, s),
8.16 (4H, s), 9.34 (4H, d, J = 4.4 Hz); FT-IR (ATR) νmax 3117, 3062,
(1) (a) Marx, T.; Wesemann, L.; Dehnen, S.; Pantenburg, I. Chem. Eur.
J. 2001, 7, 3025−3032. (b) Yam, V. W. W. Structure and Bonding:
Photofunctional Transition Metal Complexes; Springer: Heidelberg,
Germany, 2007.
H
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Article
(2) (a) Wong, K. M. C.; Hui, C. K.; Yu, K. L.; Yam, V. W. W. Coord.
Chem. Rev. 2002, 229, 123−132. (b) Roundhill, D. M.; Gray, H. B.; Che,
C. M. Acc. Chem. Res. 1989, 22, 55−61.
(18) (a) Yam, V. W. W.; Wong, K. M. C.; Zhu, N. Y. Angew. Chem., Int.
Ed. 2003, 42, 1400−1403. (b) Chan, K. H. Y.; Chow, H. S.; Wong, K. M.
C.; Yeung, M. C. L.; Yam, V. W. W. Chem. Sci. 2010, 1, 477−482.
(c) Yam, V. W. W.; Chan, K. H. Y.; Wong, K. M. C.; Chu, B. W. K.
Angew. Chem., Int. Ed. 2006, 45, 6169−6173.
(19) Chan, C. K. M.; Tao, C. H.; Li, K. F.; Wong, K. M. C.; Zhu, N. Y.;
Cheah, K. W.; Yam, V. W. W. Dalton Trans. 2011, 40, 10670−10685.
(20) Chen, L. J.; Zhang, J.; He, J. M.; Xu, X. D.; Wu, N. W.; Wang, D.
X.; Abliz, Z.; Yang, H. B. Organometallics 2011, 30, 5590−5594.
(21) de Quadras, L.; Shelton, A. H.; Kuhn, H.; Hampel, F.; Schanze, K.
S.; Gladysz, J. A. Organometallics 2008, 27, 4979−4991.
(22) Yam, V. W. W.; Hui, C. K.; Yu, S. Y.; Zhu, N. Y. Inorg. Chem. 2004,
43, 812−821.
(3) (a) Cummings, S. D.; Eisenberg, R. J. Am. Chem. Soc. 1996, 118,
1949−1960. (b) Hissler, M.; McGarrah, J. E.; Connick, W. B.; Geiger, D.
K.; Cummings, S. D.; Eisenberg, R. Coord. Chem. Rev. 2000, 208, 115−
137. (c) Hissler, M.; Connick, W. B.; Geiger, D. K.; McGarrah, J. E.;
Lipa, D.; Lachicotte, R. J.; Eisenberg, R. Inorg. Chem. 2000, 39, 447−457.
(4) Chan, C. W.; Cheng, L. K.; Che, C. M. Coord. Chem. Rev. 1994, 132,
87−97.
(5) Whittle, C. E.; Weinstein, J. A.; George, M. W.; Schanze, K. S. Inorg.
Chem. 2001, 40, 4053−4062.
(6) Yam, V. W. W.; Tang, R. P. L.; Wong, K. M. C.; Cheung, K. K.
Organometallics 2001, 20, 4476−4482.
(23) (a) Wong, K. M. C.; Tang, W. S.; Chu, B. W. K.; Zhu, N. Y.; Yam,
V. W. W. Organometallics 2004, 23, 3459−3465. (b) Du, P.; Schneider,
J.; Jarosz, P.; Zhang, J.; Brennessel, W. W.; Eisenberg, R. J. Phys. Chem. B
2007, 111, 6887−6894.
(7) Yang, Q. Z.; Wu, L. Z.; Wu, Z. X.; Zhang, L. P.; Tung, C. H. Inorg.
Chem. 2002, 41, 5653−5655.
(8) (a) Zhang, D.; Wu, L. Z.; Zhou, L.; Han, X.; Yang, Q. Z.; Zhang, L.
P.; Tung, C. H. J. Am. Chem. Soc. 2004, 126, 3440−3441.
(b) Chakraborty, S.; Wadas, T. J.; Hester, H.; Flaschenreim, C.;
Schmehl, R.; Eisenberg, R. Inorg. Chem. 2005, 44, 6284−6293.
(c) Wadas, T. J.; Wang, Q. M.; Kim, Y. J.; Flaschenreim, C.; Blanton,
T. N.; Eisenberg, R. J. Am. Chem. Soc. 2004, 126, 16841−16849.
(d) Guo, F. Q.; Sun, W. F.; Liu, Y.; Schanze, K. Inorg. Chem. 2005, 44,
4055−4065.
(24) (a) Po, C.; Ke, Z. H.; Tam, A. Y. Y.; Chow, H. F.; Yam, V. W. W.
Chem. Eur. J. 2013, 19, 15735−15744. (b) Hijazi, A.; Walther, M. E.;
Besnard, C.; Wenger, O. S. Polyhedron 2010, 29, 857−863.
(25) (a) Yam, V. W. W.; Hui, C. K.; Wong, K. M. C.; Zhu, N. Y.;
Cheung, K. K. Organometallics 2002, 21, 4326−4334. (b) Yang, Q. Z.;
Tong, Q. X.; Wu, L. Z.; Wu, Z. X.; Zhang, L. P.; Tung, C. H. Eur. J. Inorg.
Chem. 2004, 1948−1954. (c) Lai, S.-W.; Chan, M. C. W.; Cheung, K.-K.;
Che, C.-M. Inorg. Chem. 1999, 38, 4262−4267. (d) Lu, W.; Chan, M. C.
W.; Cheung, K. K.; Che, C. M. Organometallics 2001, 20, 2477−2486.
(e) Lu, W.; Chan, M. C. W.; Zhu, N. Y.; Che, C. M.; He, Z.; Wong, K. Y.
Chem. Eur. J. 2003, 9, 6155−6166. (f) Lu, W. C.; M, C. W.; Zhu, N.; Che,
C.-M.; Li, C.; Hui, Z. J. Am. Chem. Soc. 2004, 126, 7639−7651.
(26) Wong, K. M. C.; Yam, V. W. W. Coord. Chem. Rev. 2007, 251,
2477−2488.
(9) (a) Chen, Y.; Lu, W.; Che, C. M. Organometallics 2013, 32, 350−
353. (b) Luo, J.; Khusnutdinova, J. R.; Rath, N. P.; Mirica, L. M. Chem.
Commun. 2012, 48, 1532−1534. (c) Plutino, M. R.; Castriciano, M. A.;
Mazzaglia, A.; Saporita, M.; Romeo, A.; Scolaro, L. M. J. Porphyrins
Phthalocyanines 2011, 15, 1052−1061.
(10) (a) Du, P.; Schneider, J.; Fan, L.; Zhao, W.; Patel, U.; Castellano,
F. N.; Eisenberg, R. J. Am. Chem. Soc. 2008, 130, 5056−5058. (b) Du, P.
W.; Schneider, J.; Jarosz, P.; Eisenberg, R. J. Am. Chem. Soc. 2006, 128,
7726−7727. (c) Zhong, J. J.; Meng, Q. Y.; Wang, G. X.; Liu, Q.; Chen,
B.; Feng, K.; Tung, C. H.; Wu, L. Z. Chem. Eur. J. 2013, 19, 6443−6450.
(11) Yam, V. W. W.; Wong, K. M. C.; Zhu, N. Y. J. Am. Chem. Soc.
2002, 124, 6506−6507.
(12) Tang, W. S.; Lu, X. X.; Wong, K. M. C.; Yam, V. W. W. J. Mater.
Chem. 2005, 15, 2714−2720.
(13) Crossley, E. L.; Aitken, J. B.; Vogt, S.; Harris, H. H.; Rendina, L.
M. Angew. Chem., Int. Ed. 2010, 49, 1231−1233.
(14) (a) Pei, Q. B.; Yu, G.; Zhang, C.; Yang, Y.; Heeger, A. J. Science
1995, 269, 1086−1088. (b) Kwok, E. C. H.; Chan, M. Y.; Wong, K. M.
C.; Lam, W. H.; Yam, V. W. W. Chem. Eur. J. 2010, 16, 12244−12254.
(c) Guo, F. Q.; Ogawa, K.; Kim, Y. G.; Danilov, E. O.; Castellano, F. N.;
Reynolds, J. R.; Schanze, K. S. Phys. Chem. Chem. Phys. 2007, 9, 2724−
2734.
(15) (a) Chan, C. K. M.; Tao, C. H.; Li, K. F.; Wong, K. M. C.; Zhu, N.
Y.; Cheah, K. W.; Yam, V. W. W. J. Organomet. Chem. 2011, 696, 1163−
1173. (b) Furuta, P. T.; Deng, L.; Garon, S.; Thompson, M. E.; Frechet,
J. M. J. J. Am. Chem. Soc. 2004, 126, 15388−15389.
(16) (a) Wong, K. M. C.; Yam, V. W. W. Acc. Chem. Res. 2011, 44,
424−434. (b) Chan, K. H. Y.; Lam, J. W. Y.; Wong, K. M. C.; Tang, B. Z.;
Yam, V. W. W. Chem. Eur. J. 2009, 15, 2328−2334. (c) Tam, A. Y. Y.;
Wong, K. M. C.; Yam, V. W. W. Chem. Eur. J. 2009, 15, 4775−4778.
(d) Yu, C.; Chan, K. H. Y.; Wong, K. M. C.; Yam, V. W. W. Chem. Eur. J.
2008, 14, 4577−4584. (e) Yeung, M. C. L.; Yam, V. W. W. Chem. Sci.
2013, 4, 2928−2935. (f) Chung, C. Y. S.; Li, S. P. Y.; Louie, M. W.; Lo,
K. K. W.; Yam, V. W. W. Chem. Sci. 2013, 4, 2453−2462.
(17) (a) Yam, V. W. W.; Tang, R. P. L.; Wong, K. M. C.; Ko, C. C.;
Cheung, K. K. Inorg. Chem. 2001, 40, 571−574. (b) Yu, C.; Wong, K. M.
C.; Chan, K. H. Y.; Yam, V. W. W. Angew. Chem., Int. Ed. 2005, 44, 791−
794. (c) Lo, H. S.; Yip, S. K.; Zhu, N. Y.; Yam, V. W. W. Dalton Trans.
2007, 4386−4389. (d) Tanaka, Y.; Wong, K. M. C.; Yam, V. W. W.
Chem. Sci. 2012, 3, 1185−1191. (e) Leung, S. Y. L.; Tam, A. Y. Y.; Tao,
C. H.; Chow, H. S.; Yam, V. W. W. J. Am. Chem. Soc. 2012, 134, 1047−
1056. (f) Zhang, H. X.; Kato, M.; Sasaki, Y.; Ohba, T.; Ito, H.;
Kobayashi, A.; Chang, H. C.; Uosaki, K. Dalton Trans. 2012, 41, 11497−
11506.
(27) (a) Demas, J. N.; Crosby, G. A. J. Phys. Chem. 1971, 75, 991−
1024. (b) Calvert, J. M.; Caspar, J. V.; Binstead, R. A.; Westmoreland, T.
D.; Meyer, T. J. J. Am. Chem. Soc. 1982, 104, 6620−6627.
(28) Chung, C. Y. S.; Yam, V. W. W. J. Am. Chem. Soc. 2011, 133,
18775−18784.
(29) Castellano, F. N.; Pomestchenko, I. E.; Shikhova, E.; Hua, F.;
Muro, M. L.; Rajapakse, N. Coord. Chem. Rev. 2006, 250, 1819−1828.
(30) Han, X.; Wu, L. Z.; Si, G.; Pan, J.; Yang, Q. Z.; Zhang, L. P.; Tung,
C. H. Chem. Eur. J. 2007, 13, 1231−1239.
(31) Chong, S. H. F.; Lam, S. C. F.; Yam, V. W. W.; Zhu, N. Y.; Cheung,
K. K.; Fathallah, S.; Costuas, K.; Halet, J. F. Organometallics 2004, 23,
4924−4933.
(32) (a) Muro, M. L.; Daws, C. A.; Castellano, F. N. Chem. Commun.
2008, 6134−6136. (b) Yip, H. K.; Cheng, L. K.; Cheung, K. K.; Che, C.
M. J. Chem. Soc., Dalton Trans. 1993, 2933−2938.
(33) Norris, B. N.; Pan, T. Q.; Meyer, T. Y. Org. Lett. 2010, 12, 5514−
5517.
(34) Mayor, M.; Didschies, C. Angew. Chem., Int. Ed. 2003, 42, 3176−
3179.
(35) Moy, C. L.; Kaliappan, R.; McNeil, A. J. J. Org. Chem. 2011, 76,
8501−8507.
(36) Breul, A. M.; Schafer, J.; Pavlov, G. M.; Teichler, A.; Hoppener, S.;
Weber, C.; Nowotny, J.; Blankenburg, L.; Popp, J.; Hager, M. D.;
Dietzek, B.; Schubert, U. S. J. Polym. Sci., Part A: Polym. Chem. 2012, 50,
3192−3205.
(37) Plater, M. J.; Sinclair, J. P.; Aiken, S.; Gelbrich, T.; Hursthouse, M.
B. Tetrahedron 2004, 60, 6385−6394.
(38) Zhou, C. Z.; Liu, T. X.; Xu, J. M.; Chen, Z. K. Macromolecules
2003, 36, 1457−1464.
(39) (a) Iwadate, N.; Suginome, M. Org. Lett. 2009, 11, 1899−1902.
(b) Luo, F. T.; Ko, S. L.; Chao, D. Y. Tetrahedron Lett. 1997, 38, 8061−
8062.
(40) APEX2 v2009; Bruker AXS, Madison, WI, 2009.
(41) Sheldrick, G. M. Acta Crystallogr., Sect. A 2008, A64, 112−122.
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dx.doi.org/10.1021/om500115s | Organometallics XXXX, XXX, XXX−XXX