Orange-Red Phosphorescent Iridium(III) Complexes Bearing Bisphosphine Ligands: Synthesis, Photophysical and Electrochemical Properties, and DFT Calculations

Article abstract of DOI:10.1021/acs.organomet.7b00740

Nine new phosphorus-coordinated iridium(III) complexes of the form [Ir(C^{^}N)₂(P^{^}P)]PF₆, [Ir(F-piq)₂(xantphos)]PF₆ (1), [Ir(F-piq)₂(binap)]PF₆ (2), [Ir(F-piq)₂

Full text of DOI:10.1021/acs.organomet.7b00740

Article
Cite This: Organometallics XXXX, XXX, XXX−XXX
Orange-Red Phosphorescent Iridium(III) Complexes Bearing
Bisphosphine Ligands: Synthesis, Photophysical and Electrochemical
Properties, and DFT Calculations
Gao-Nan Li,†,§ Shao-Bin Dou,†,§ Tao Zheng,† Xiao-Qing Chen,† Xiao-Han Yang,† Shuang Wang,†
Wei Sun,† Guang-Ying Chen,‡ Zheng-Rong Mo,‡ and Zhi-Gang Niu*,†
†College of Chemistry and Chemical Engineering, Hainan Normal University, Haikou 571158, People’s Republic of China
‡Key Laboratory of Tropical Medicinal Plant Chemistry of Ministry of Education, Hainan Normal University, Haikou 571158,
People’s Republic of China
S
* Supporting Information
ABSTRACT: Nine new phosphorus-coordinated iridium(III) complexes of the form
[Ir(C∧N)2(P∧P)]PF6, [Ir(F-piq)2(xantphos)]PF6 (1), [Ir(F-piq)2(binap)]PF6 (2),
[Ir(F-piq)2(dppp)]PF6 (3), [Ir(Me-piq)2(xantphos)]PF6 (4), [Ir(Me-piq)2(binap)]PF6
(5), [Ir(Me-piq)2(dppp)]PF6 (6), [Ir(CF3O-piq)2(xantphos)]PF6 (7), [Ir(CF3O-
piq)2(binap)]PF6 (8), and [Ir(CF3O-piq)2(dppp)]PF6 (9) (F-piq = 1-(4-fluorophenyl)-
isoquinoline, Me-piq = 1-(p-tolyl)isoquinoline, CF3O-piq = 1-(4-(trifluoromethoxy)-
phenyl)isoquinoline, xantphos = 9,9-dimethyl-4,5-bis(diphenylphosphino)xanthene,
binap = 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl, dppp = 1,3-bis-
(diphenylphosphanyl)propane), have been synthesized and fully characterized. The
crystal structures of 1, 7, and 9 have been determined by X-ray analysis. The most
representative molecular orbital energy-level diagrams and the lowest energy electronic transitions of 1−9 have been calculated
with density functional theory (DFT) and time-dependent DFT (TD-DFT). All of the complexes are orange-red emissive with
quantum efficiencies of 3.2−24.4% and lifetimes of 1.77−3.19 μs in degassed CH2Cl2 solution at room temperature. These
research results reveal that the Me-piq C∧N ligand and xantphos P∧P ligand are beneficial for a red shift of absorption and
emission wavelength. Complex 4 has better charge transfer ability, which probably promises its use as a red-phosphorescent
material.
more reports of red phosphors with the motif [Ir-
(C∧N)2(P∧P)]PF6.
INTRODUCTION
■
During the last few decades, a considerable amount of interest
has been drawn to the application of iridium(III) complexes in
white organic light-emitting diodes (WOLEDs) and full-color
displays.1−5 For the realization of white emission, it is essential
to obtain high efficiency and color purity for the three primary
blue-, green-, and red-emitting materials.6,7 Indeed, true red
emitters are more difficult because their luminescent quantum
yields tend to be lower due to the smaller energy gap.8,9
Therefore, our goal is to design novel red-emissive Ir(III)
complexes with larger quantum yields, for the realization of
highly efficient WOLEDs.
Studies on photoluminescent iridium complexes bearing
diphosphine ligands have been carried out in recent years due
to their chemical stability, excellent color tunability, and high
quantum efficiencies. In 2013, a series of Ir(III) complexes with
bent-diphosphine ligands were first reported by Hor et al.
These complexes covered a broad emission range from 472 nm
(blue) to 569 nm (orange) with quantum efficiencies up to 0.38
at room temperature.10 More recently, Zysman-Colman and
co-workers prepared 13 cationic iridium(III) complexes of the
form [Ir(C∧N)2(P∧P)]PF6. All of the complexes were sky blue
emissive, but their photoluminescence quantum yields (ΦPL)
were generally low.11 However, to date, there have been no
In order to push the emission of [Ir(C∧N)2(P∧P)]PF6
complexes further into the red region, one key requirement is
to choose a suitable C∧N cyclometalating ligand. Iridium(III)
complexes with 1-phenylisoquinoline (piq) are well-known as
red-emitting materials. The first important example was the
[Ir(piq)3] complex, which emitted red phosphorescence with a
wavelength maximum at 620 nm and showed good red color
purity with CIE characteristics (0.68, 0.32).12 Afterward,
numerous substituted bis(1-phenylisoquinolinato) cyclometa-
lating iridium complexes were reported, such as [Ir-
(piq)2(acac)] (λem 622 nm),13 [Ir(piq-F)2(acac)] (λem 600
nm),13 [Ir(5-f-1piq)2(acac)] (λem 632 nm),14 [Ir(5-f-1fpi-
q)2(acac)] (λem 609 nm),14 and mer-[Ir(1-piq)2(ppy)] (λem
620 nm).15
Herein, we incorporated three piq-based C∧N ligands (F-piq,
Me-piq, and CF3O-piq) and three steric blocking diphosphine
P∧P ligands (xantphos, binap, and dppp) to yield an array of
nine cationic Ir(III) species (Figure 1). Their electrochemical
and optical properties have been measured and analyzed. Again,
Received: October 4, 2017
© XXXX American Chemical Society
A
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Figure 1. Chemical structures of complexes 1−9.
the absorption spectra are rationalized on the basis of density
functional theory (DFT) and time-dependent DFT (TD-
DFT). The luminescent properties have been investigated both
in the solid state and in solution (at room temperature and 77
K).
which suggests that the chemical formula of each Ir(III)
complex is [Ir(C∧N)2(P∧P)]PF6. The 31P NMR spectra for
complexes 1−9 show singlet resonances from −30.70 to
−10.63 ppm, indicating the two phosphorus atoms in the P∧P
ligand, whereas the septets at around −144 ppm are
characteristic of the PF6 anion. The ESI-MS spectra give
diagnostic peaks which are ascribed to [Ir(C∧N)2(P∧P)]+.
Complexes 1−9 were further characterized by FT-IR, and the
purity was confirmed by elemental analysis. The IR spectra of
complexes 1−9 have almost the same tendency, which reveal
RESULTS AND DISCUSSION
■
Synthesis and Characterization. The syntheses of the
piq-based cyclometalating ligands 3a−c and their derived
complexes 1−9 are shown in Scheme 1. These compouds 3a−c
were prepared by the Suzuki coupling reaction between 1-
chloroisoquinoline and the corresponding substituted boronic
acid (2a−c) under palladium catalysis in good yields (91.8−
94.6%). Cyclometalated Ir(III) dichloro-bridged dimers, [Ir-
(C∧N)2(μ-Cl)]2, were synthesized by iridium trichloride
hydrate with 2.2 equiv of 3a−c in a 2:1 mixture of 2-
ethoxyethanol and deionized water according to a similar
method reported by Nonoyama.16 Then the new phosphorus-
coordinated iridium(III) complexes 1−9 were obtained by the
reaction of [Ir(C∧N)2(μ-Cl)]2 with bisphosphine ligands (P1−
P3) in CH2Cl2/MeOH (1/1) followed by addition of excess
NH4PF6. All of these new compounds were characterized by
1H, 13C, and 31P NMR spectroscopy and ESI-MS spectrometry.
In 1H NMR spectra, the ratio of the C∧N to P∧P ligands is 2:1,
−
the strong P−F stretches of the PF6 group in the range of
843−846 cm−1.
Structural Description. Single-crystal structures of 1, 7,
and 9 were obtained through X-ray diffraction analysis, and the
ORTEP diagrams are shown in Figure 2. The crystallographic
data and structure refinement details are given in Table S1 in
the Supporting Information; selected bond lengths and bond
angles are collected in Table S2 in the Supporting Information.
These iridium(III) complexes have a distorted-octahedral
coordination geometry around Ir, retaining the cis-C,C and
trans-N,N configuration of the C∧N cyclometalating ligands.17
Meanwhile, the two phosphorus atoms of the P∧P ligand are
disposed trans with respect to the carbon atoms of the C∧N
ligand. All of the Ir−C (2.028(4)−2.065(5) Å), Ir−N
B
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Scheme 1. Synthetic Routes of Ir(III) Complexes 1−9
−
Figure 2. Molecular structures of complexes 1, 7, and 9. PF6 counterions, solvent molecules, and hydrogen atoms are omitted for clarity.
(2.060(4)−2.091(4) Å), and Ir−P bond lengths (2.4248(13)−
2.5113(12) Å) are close to those in previously reported iridium
complexes bearing phosphine ligands.18,19
complex 9 with a six-membered chelate ring (2.4248(13)−
2.4504(13) Å). Additionally, one of the phenyl rings is almost
fixed in a parallel position with the isoquinoline ring, whereas
another phenyl ring is twisted out of planarity from the
aforementioned fragment by 27.231(116)° (1), 25.618(107)°
(7), and 22.295(144)° (9), respectively.
The P−Ir−P angles can be seen to vary in a regular manner.
The P−Ir−P bond angles (96.35(4)−97.85(4)°) of complexes
1 and 7 with the xantphos ligand are significantly greater than
the P−Ir−P bond angle (94.49(4)°) of complex 9 with a dppp
ligand. This is apparently due to the size of the chelate formed
by the P∧P ligand at the metal center. To accommodate the
varying sizes of chelate rings, the Ir−P bonds are found to vary
in consequence, those in complexes 1 and 7 with an eight-
membered chelate ring showing longer Ir−P bonds
(2.4959(13)−2.5113(12) Å) in comparison to those in
Photophysical Properties. The UV−vis absorption
spectra of complexes 1−9 in CH2Cl2 solution at room
temperature are depicted in Figure 3, and the data are provided
in Table 1.
Similar to the case for many other cationic [Ir(C∧N)2(P∧P)]+
iridium complexes found in the literature,20−22 the absorption
spectra of complexes 1−9 are dominated by multiple bands
C
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The normalized emission spectra of 1−9 in the CH2Cl2
solution (at room temperature and 77 K) and in the solid state
are given in Figure 4. The corresponding data are also given in
Table 1.
Under photoexcitation, all Ir(III) complexes in solution at
room temperature emit intense orange to red light with
emission maxima bunched between 589 and 619 nm (Figures
4a and 5). Meanwhile, the emission spectra are broad and
structureless, indicating that the emissive excited states are
27,28
3
dominantly the MLCT character.
It should be noted that
the emission wavelengths for 1, 4, and 7 are red-shifted relative
to other series of complexes 2−3, 5−6, and 8−9, respectively.
Moreover, complex 4 exhibits emission spectra even more red
shifted in comparison to the other complexes (1 and 7) of the
series. Thus, the emission spectrum of 4 (λem 619 nm) is in the
expected red region. The results are in good agreement with
those of the lowest-energy electronic transition in the above
UV−vis spectra.
As the temperature is decreased to 77 K, marked variations
are noted in the emission spectra (Figure 4b). For complexes
2−3, 5−6, and 8−9, a significant hypsochromic shift in
emission maxima is seen. The shift occurs because the
relaxation rate of the solvent is strongly dependent on
temperature, as illustrated by Balter et al.29 In contrast, the
emission bands of complexes 1, 4, and 7 show a slight
bathochromic shift. It is conceivable that the phenomenon
depends on the change of P∧P ancillary ligands. Namely, the
structural relaxation of iridium complexes with the xantphos
ligand was not suppressed at lower temperature. Additionally,
the vibrational structure in emission spectra at 77 K is present,
since at low temperature the fine structure of different vibronic
levels of S1 → S0 is not affected by the collision−inactivation.30
For solid-state emissions (Figure 4c), all of these complexes
have a stronger bathochromic effect and broader emission in
comparison to those in the solution state, which is consistent
with the excimer formation arising from π−π stacking
Figure 3. UV−vis spectra of complexes 1−9 in CH2Cl2 at room
temperature.
originating from ligand-centered π−π* transitions and MLCT
transitions. The intense bands at higher energies (240−320
nm) are assigned to the spin-allowed ligand-centered (LC)
1π−π* transitions. The weaker bands at lower energies (320−
500 nm) are attributed to charge transfer transitions, with their
nature being both spin-allowed (singlet to singlet metal to
1
ligand charge transfer, MLCT) and spin-forbidden (singlet to
triplet metal to ligand charge transfer (3MLCT) and ligand-
23−26
3
centered π−π* transition).
From Table 1, it is found that the xantphos ancillary ligand of
complexes 1, 4, and 7 and the Me-piq cyclometalating ligand of
complexes 4−6 both can cause an absorption maximum red
shift in the latter low-energy region. Consequently, complex 4
has the longest absorption wavelength (425 nm). In addition,
from the absorption edges (395−425 nm) of complexes 1−9,
their corresponding optical energy gaps (Eg) are estimated to
be 2.92−3.14 eV, which correlates well with the variation rules
of the HOMO−LUMO energy gaps discussed below.
Table 1. Optoelectronic Characterization of Complexes 1−9
emission
absorption
solution
solid
a
electrohem
a
b
a
c
a
d
d
d
e
f
kr (105 s−1
)
knr (105 s−1
)
τr (μs)
λem (nm)
λem (nm)
Φabs (%)
Eox (V)
RT
77K
complex λabs (nm)
Eg (eV)
λem (nm)
Φem (%) τ (μs)
1
2
3
4
5
6
7
8
9
297, 361,
416
2.98
3.02
3.12
2.92
3.02
3.08
3.06
3.03
3.14
611
598
589
619
596
589
610
602
593
3.2
24.4
5.5
2.66
3.19
2.01
2.33
2.73
2.05
2.58
2.83
1.77
0.12
3.64
83.1
613 (654)
587 (631)
581 (625)
620 (663)
594 (637)
588 (635)
617 (658)
588 (633)
584 (611)
622
17.1
0.99
285, 338,
373, 411
0.77
0.27
0.17
0.23
0.30
0.18
0.45
0.55
2.37
4.70
4.12
3.43
4.58
3.70
3.08
5.10
13.1
36.5
58.3
42.7
33.1
56.1
22.1
18.1
617
594
30.1
17.7
12.2
28.8
21.7
17.7
34.8
21.0
0.96
0.95
0.90
0.91
0.97
1.05
1.05
1.04
277, 365,
398
272, 355,
425
4.0
625
290, 339,
377, 411
6.4
611
286, 357,
403
6.2
600
291, 356,
405
4.6
621
282, 340,
375, 410
12.8
9.8
602
278, 363,
395
571 (602)
a
b
c
Data were collected from degassed CH2Cl2 solutions at room temperature. The optical energy gap Eg determined from the absorption onset. fac-
Ir(ppy)3 as reference standard (0.4).44 Radiative decay rate (kr), nonradiative decay rate (knr), and pure radiative lifetime (τr) estimated from the
measured quantum yields and lifetimes. Data were collected from degassed CH2Cl2 solutions at 77 K. The solid-state absolute quantum yields were
d
e
f
measured by employing an integrating sphere.
D
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state at room temperature, which is indicative of a mixing of
32−34
3
3LC (3π−π*) and CT (3MLCT) excited states.
Phosphorescence relative quantum yields (Φem) of 1−9 in
dichloromethane solution were measured to be 3.2−24.4%
(Table 1) at room temperature by using the typical
phosphorescent fac-Ir(ppy)3 as a standard (Φ = 0.40). The
quantum efficiency of complex 2 (24.4%) is higher relative to
those of complexes 1 (3.2%) and 3 (5.5%). Possibly, this is
because the steric hindrance of the bulky diphosphine ligands
prevents deactivation of the emitters by limiting energy transfer
between the complexes.10 A similar effect is also observed for
complexes 5 (6.4%) and 8 (12.8%), respectively. The
introduction of the electron-withdrawing group (−F) in
complex 2 results in a dramatic increase in the phosphor-
escence quantum yield. It can be surmised that the presence of
the C−F bonds leads to the reduced radiationless deactivation
rate.35,36 Furthermore, the solid-state absolute quantum yields
(Φabs) of 1−9 were measured to be 12.2−34.8% (Table 1) by
employing an integrating sphere. We note that the Φabs values
of these complexes are noticeably improved. Obviously, the
Φabs values of 2, 5, and 8 are much higher than those of other
complexes in the corresponding series. This proves again the
aforementioned steric hindrance effect of the binap ligand.
Phosphorescence (solution) is obtained in all cases with
microsecond lifetimes at room temperature, ranging from 1.77
to 3.19 μs, which suggests a possible triplet nature of the
emissive excited state. Interestingly, complexes 3, 6, and 9 have
significantly shorter excited-state lifetimes than analogues 1−2,
4−5, and 7−8. Such results indicate that the three Ir complexes
possess effective T1 to S0 radiative relaxation, which is beneficial
for the OLED operation.
From the quantum yields Φem and the τ lifetime values, the
radiative decay rate (kr), the nonradiative decay rate (knr), and
the pure radiative lifetime (τr) were calculated for a series of
complexes through the equations kr = Φem/τ, knr = (1 − Φem)/
38
τ,37 and τr ≈ τ/Φem (see Table 1). Thus, the emission
quantum yield (Φem) is generally formulated as Φem = kr/(kr +
knr). From the equation, we can conclude that a large kr and a
small knr are required to increase the quantum yield. For 2, the
kr value is the largest and the knr value is the smallest within the
investigated complexes, which makes it distinctive as being the
most strongly emissive in the family of complexes. The radiative
lifetime (τr) was deduced to be 13.1−83.1 μs for all complexes
1−9. This value is comparable to that of the red-emitting Ir(III)
complexes.12,38
Figure 4. Normalized emission spectra of 1−9 in the CH2Cl2 solution
at room temperature (a) and 77 K (b) and in the solid state (c).
Theoretical Calculations. Density functional theory
(DFT) and time-dependent DFT (TD−DFT) calculations
have been performed for complexes 1−9 to gain insights into
the lowest-energy electronic transition. The HOMO−LUMO
energy-level diagrams for these complexes and the energy gap
are presented in Figure 6. The calculated spin-allowed
electronic transitions are provided in Table 2 and compared
with the experimental absorption spectral data.
As seen in Figure 6, the HOMOs of 1−9 are mainly
dominated by iridium d orbitals and π orbitals of phenyl and
pyridine rings of the two cyclometalating ligands, along with a
minor contribution from the ancillary ligand. Meanwhile, the
LUMO/LUMO+1 are mostly located on π* orbitals of phenyl
and pyridine rings of the two cyclometalating ligands.
Therefore, the lowest-energy electronic transition (HOMO
→ LUMO, HOMO → LUMO+1) of these Ir(III) complexes
1−9 are ascribed as MLCT, LL′CT, and ILCT π → π*
Figure 5. Photo showing PL of 1−9 (from left to right) in solution (in
CH2Cl2 under irradiation by a UV lamp at 365 nm).
interactions in the solid state.31 Specifically, a structured
vibronic emission profile is found for complex 9 in the solid
E
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Figure 6. Molecular orbital energy-level diagrams of HOMOs and LUMOs in iridium complexes 1−9.
Table 2. Main Experimental and Calculated Optical Transitions for Complexes 1−9
complex
HOMO (eV)
LUMO (eV)
LUMO+1 (eV)
oscillation strength (eV)
calcd (nm)
exptl (nm)
1
2
3
4
5
6
7
8
9
HOMO → LUMO+1
HOMO → LUMO
HOMO → LUMO+1
HOMO → LUMO+1
HOMO → LUMO
HOMO → LUMO+1
HOMO → LUMO+1
HOMO → LUMO
HOMO → LUMO+1
−6.065
−6.109
−6.101
−5.889
−5.958
−5.929
−6.136
−6.172
−6.225
−2.493
−2.511
−2.464
−2.412
−2.410
−2.385
−2.550
−2.581
−2.576
−2.427
0.0791
0.0865
0.1441
0.0652
0.0860
0.1284
0.0732
0.0926
0.1243
412
415
399
429
425
415
415
417
403
416
411
398
425
411
403
405
410
395
−2.395
−2.352
−2.318
−2.497
−2.520
transitions,39 which are consistent with the actual absorptions
(Table 2).
centered oxidations are reversible and the irreversibility
increases as the contribution to the HOMO of the cyclo-
metalating phenyl(s) increases.40,41 From Table 1, it can be
seen that the Eox values are in the order 4−6 < 1−3 < 7−9,
which is consistent with the actual electron-donating ability of
−CH3 > −F > −OCF3. These findings indicate the electron-
donating (−CH3) group can improve the HOMO energy
levels, while the electron-withdrawing fluorine atom lower them
effectively, especially − OCF3 group. The variation tendency is
approximately consistent with DFT calculations.
In Figure 6, the HOMO levels of complexes 4−6 are
distinctly greater than those of the other two families of
complexes 1−3 and 7−9, owing to the increases in the electron
density around the iridium center provided by the electron-
donating methyl group on the C∧N ligand. The increase in
HOMO levels reduces the HOMO−LUMO energy gap,
thereby leading to red-shifted emission. For complexes 4−6,
the HOMO−LUMO gap of 4 is the smallest of all complexes,
which is dependent on the nature of the ancillary ligand.
However, while simply replacing the P∧P ancillary ligand results
in a slight change in HOMO value, further replacing the −CH3
substituent group on cyclometalating ligands leads to a
significant change in HOMO energy level. This behavior, in
combination with the aforementioned emission spectra,
supports the supposition that the cyclometalating ligand with
electron-donating group plays an important role in the red-
shifted emission. This observation agrees well with the
photophysical properties discussed above.
Electrochemical Properties. The electrochemical behav-
iors of these iridium complexes were investigated by cyclic
voltammetry. The electrochemical waves are shown in Figure
S1 in the Supporting Information, and the oxidation potentials
(Eox) are compiled in Table 1. All nine complexes introduced in
this work exhibit quasi-reversible monoelectronic oxidation
peaks around 0.90−1.05 V. The oxidation processes are linked
to metal-centered orbitals with a contribution from the phenyl
part of cyclometalated fragments, which was confirmed by our
DFT calculations (Figure 6). It is assumed that pure metal-
CONCLUSION
■
In conclusion, nine orange to red emitting cationic heteroleptic
iridium(III) complexes incorporating bisphosphine ancillary
ligands have been synthesized and characterized. Their
photophysical properties, theoretical calculations, and electro-
chemical behaviors have been investigated. The molecular
structures of complexes 1, 7, and 9 reveal that they all possess
pseudo-octahedral coordination geometry. Analyses of DFT
and TD-DFT calculations indicate that the lowest-energy
electronic transitions are attributed to MLCT, LL′CT, and
ILCT π → π* transitions. However, the emission spectra in
solution at room temperature are broad and structureless,
suggesting that the lowest excited states are dominantly
3MLCT excitations. Through optimization of three C∧N
cyclometalating ligands (F-piq, Me-piq, and CF3O-piq) and
three P∧P ancillary ligands (xantphos, binap, and dppp), we
have rationally designed the red-emitting complex 4 (λem 619
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dealing with air-sensitive reactions were carried out under a nitrogen
atmosphere.
nm), which would be a potential candidate for red
phosphorescent materials.
Syntheses. 1-(4-Fluorophenyl)isoquinoline (F-piq, 3a). To a
degassed solution of 1-chloroisoquinoline (1.0 g, 6.11 mmol) and (4-
fluorophenyl)boronic acid (2a; 940 mg, 6.72 mmol) in 1,4-dioxane
(20 mL) was added Pd(dppf)Cl2 (0.21 g, 0.31 mmol) and potassium
phosphate (1.27 g, 9.17 mmol), and then the reaction mixture was
degassed under vacuum and charged with N2. The mixture was heated
to 80 °C and stirred for 10 h under a nitrogen atmosphere. The
mixture was poured into water and extracted multiple times with ethyl
acetate. The combined organic phases were washed with brine and
dried over Na2SO4. After concentration, the residue was purified by
column chromatography to give the desired compound 3a (1.28 g,
EXPERIMENTAL SECTION
■
General Methods. NMR spectra were recorded on a Bruker AM
400 MHz instrument (1H, 400 MHz; 13C, 100 MHz; 31P, 162 MHz).
Chemical shifts were reported in ppm relative to Me4Si as internal
standard. ESI-MS spectra were recorded on an Esquire HCT-Agilent
1200 LC/MS spectrometer. The elemental analyses were performed
on a Vario EL Cube Analyzer system. IR spectra were taken on a
Nicolet 6700 FTIR spectrometer (400−4000 cm−1) with KBr pellets.
UV−vis spectra were recorded on a Hitachi U3900/3900H
spectrophotometer. Fluorescence spectra were carried out on a
Hitachi F-7000 spectrophotometer as deaerated CH2Cl2 solutions at
room temperature and 77 K, as well as for the neat solid powders. The
absolute quantum efficiencies (Φabs) in the solid state were measured
on a PL quantum yield measurement system (Hamamatsu, Model
C9920-01). Luminescence lifetime curves were measured on an
Edinburgh Instruments FLS920P fluorescence spectrometer, and the
data were treated as one-order exponential fitting using OriginPro 8
software. All solutions were deaerated by nitrogen bubbling for 30 min
before measurements.
1
yield 93.8%) as a white solid. H NMR (400 MHz, CDCl3): δ (ppm)
8.60 (d, J = 6.0 Hz, 1H, Py-H), 7.97 (d, J = 8.4 Hz, 1H, Ar-H), 7.93 (d,
J = 8.0 Hz, 1H, Ar-H), 7.79−7.84 (m, 4H, Ar-H, Py-H), 7.73−7.78 (m,
2H, Ar-H), 7.59 (t, J = 8.0 Hz, 1H, Ar-H). 13C NMR (100 MHz,
CDCl3): δ (ppm) 158.53, 143.87, 142.08, 137.03, 134.11, 132.30,
130.79, 130.68, 128.05, 127.43, 126.71, 126.48, 121.19, 118.74, 116.46,
112.56. MS (ESI): m/z 224.1 [M + 1]+.
1-(p-Tolyl)isoquinoline (Me-piq, 3b). A procedure analogous to
that described for compound 3a was used with (4-methylphenyl)-
boronic acid (2b) instead of (4-fluorophenyl)boronic acid (2a) to
afford 3b as a white solid. Yield: 94.6%. 1H NMR (400 MHz, CDCl3):
δ (ppm) 8.60 (d, J = 6.0 Hz, 1H, Py-H), 8.13 (d, J = 8.4 Hz, 1H, Ar-
H), 7.87 (d, J = 8.4 Hz, 1H, Ar-H), 7.51−7.70 (m, 5H, Ar-H, Py-H),
7.28−7.36 (m, 2H, Ar-H), 2.47 (s, 3H, CH3). 13C NMR (100 MHz,
CDCl3): δ (ppm) 160.92, 142.32, 138.59, 137.00, 136.82, 130.06,
129.98, 129.16, 127.81, 127.18, 127.08, 126.88, 119.83, 21.49. MS
(ESI): m/z 220.1 [M + 1]+, 242.2 [M + Na]+.
1-(4-(Trifluoromethoxy)phenyl)isoquinoline (CF3O-piq, 3c). A
procedure analogous to that described for compound 3a was used
with 4-(trifluoromethoxy)phenyl)boronic acid (2c) instead of (4-
fluorophenyl)boronic acid (2a) to afford 3c as a white solid. Yield:
91.8%. 1H NMR (400 MHz, CDCl3): δ (ppm) 8.59−8.60 (m, 1H, Py-
H), 8.04 (d, J = 8.4 Hz, 1H, Ar-H), 7.85 (d, J = 8.0 Hz, 1H, Ar-H),
7.62−7.74 (m, 4H, Ar-H, Py-H) 7.52 (t, J = 7.6 Hz, 1H, Ar-H), 7.39
(d, J = 8.0 Hz, 2H, Ar-H). 13C NMR (100 MHz, CDCl3): δ (ppm)
159.03, 149.48, 141.86, 137.99, 136.83, 131.41, 130.17, 127.46, 127.04,
126.93, 126.46, 120.69, 120.34. MS (ESI): m/z 290.1 [M + 1]+, 312.1
[M + Na]+.
The luminescence quantum efficiencies in solution were calculated
by comparison of the fluorescence intensities (integrated areas) of the
standard sample fac-Ir(ppy)3 and the unknown sample according to
the equation42−44
2
⎛
⎝
⎞
⎠
⎛
⎜
⎝
⎞⎛
⎞
⎟
⎠
ηunk
Iunk Astd
⎜
⎜
⎟
⎟
Φ
= Φ
⎟⎜
unk
std
I
A
η
std ⎠⎝
unk
std
where Φunk and Φstd are the luminescence quantum yield values of the
unknown sample and fac-Ir(ppy)3 solutions (Φstd = 0.4),44
respectively, Iunk and Istd are the integrated fluorescence intensities of
the unknown sample and fac-Ir(ppy)3 solutions, respectively, Aunk and
Astd are the absorbance values of the unknown sample and fac-Ir(ppy)3
solutions at their excitation wavelengths, respectively, and the ηunk and
ηstd terms represent the refractive indices of the corresponding solvents
(pure solvents were assumed).
X-ray Structure Determination. X-ray diffraction data were
collected with an Agilent Technologies Gemini A Ultra diffractometer
equipped with graphite-monochromated Mo Kα radiation (λ = 0.7107
Å) and Cu Kα radiation (λ = 1.5418 Å) at room temperature. Data
collection and reduction were processed with CrysAlisPro software.45
All of the structures were solved using Superflip46 and refined using
SHELXL-201447 within Olex2.48 All non-hydrogen atoms were found
in alternating difference Fourier syntheses and least-squares refinement
cycles and, during the final cycles, refined anisotropically. Hydrogen
atoms were placed in calculated positions and refined as riding atoms
with a uniform value of Uiso.
[Ir(F-piq)2(xantphos)]PF6 (1). A mixture of IrCl3·3H2O (1.0 mmol)
and the ligand 3a (2.2 mmol) in 6 mL of ethoxyethanol and H2O (2/1
v/v) was heated to reflux at 120 °C for 12 h under a nitrogen
atmosphere. Upon cooling to room temperature, the red precipitate
was collected by filtration and washed with water and cooled MeOH.
After drying, the chloro-bridged dimer complex 4a was used directly in
the next step without further purification. A mixture of the above
dimer complex 4a (100 mg) and P1 ligand (2.5 equiv) was dissolved in
6 mL of DCM and MeOH (2/1 v/v), heated to 40 °C, and stirred for
19 h under a nitrogen atmosphere. After the mixture was cooled to
room temperature, NH4PF6 (5.0 equiv) was added. The mixture was
stirred at room temperature for 1 h and then evaporated to dryness.
The solid was purified by column chromatography to afford pure
Electrochemical Measurements. Cyclic voltammetry (CV) was
performed on a CHI 1210B electrochemical workstation, with a glassy-
carbon electrode as the working electrode, a platinum wire as the
counter electrode, an Ag/Ag+ electrode as the reference electrode, and
0.1 M n-Bu4NClO4 as the supporting electrolyte.
1
complex 1. Yield: 53%. H NMR (400 MHz, DMSO): δ (ppm) 8.63
(d, J = 8.4 Hz, 2H), 8.33(d, J = 8.4 Hz, 2H), 8.14−8.16 (m, 2H),
7.96−8.02 (m, 6H), 7.67 (d, J = 7.6 Hz, 2H), 7.48 (d, J = 6.8 Hz, 2H),
7.38 (t, J = 7.6 Hz, 2H), 7.26 (t, J = 7.6 Hz, 2H), 7.07 (t, J = 7.6 Hz,
4H), 6.94−6.99 (m, 6H), 6.74−6.83 (m, 6H), 6.61 (dt, J1 = 8.4 Hz, J2
= 2.4 Hz, 2H), 6.33 (t, J = 8.0 Hz, 4H), 5.19 (t, J = 8.8 Hz, 2H), 1.48
(s, 6H). 13C NMR (100 MHz, DMSO): δ (ppm) 145.51, 141.99,
140.01, 136.45, 136.35, 133.12, 132.70, 132.24, 132.09, 131.98, 131.89,
130.34, 130.13, 129.92, 129.83, 128.72, 128.37, 127.85, 127.22, 126.55,
126.48, 125.19, 124.79, 121.95, 120.08, 116.76, 116.40, 115.94, 115.75,
115.32, 115.10, 109.97, 109.74, 35.20, 28.56. 31P NMR (162 MHz,
DMSO): δ (ppm) −20.87, −144.18 (hept). MS (ESI): m/z 1215.3 [M
− PF6]+ (calcd 1215.3). Anal. Calcd for C69H50F8IrN2OP3: C, 60.92;
H, 3.71; N, 2.06. Found: C, 60.15; H, 3.76; N, 2.01. IR (KBr pellet,
cm−1): 3061 (w), 2965 (w), 2856 (w), 1576 (m), 1406 (m), 1240
Computational Details. All calculations were carried out with
Gaussian 09 software package.49 Density functional theory (DFT) and
time-dependent DFT (TD-DFT) were employed with no symmetry
constraints to investigate the optimized geometries and electron
configurations with the Becke three-parameter Lee−Yang−Parr
(B3LYP) hybrid density functional theory.50−52 The LANL2DZ
basis set was used to treat the Ir atom, whereas the 6-31G* basis
set was used to treat C, H, O, N, F, and P atoms. Solvent effects were
considered within the SCRF (self-consistent reaction field) theory
using the polarized continuum model (PCM) approach to model the
interaction with the solvent.53,54
Materials. IrCl3·3H2O and other chemicals were obtained from
commercial sources and used without further purification. All solvents
were purified and dried by standard procedures. All of the reactions
G
DOI: 10.1021/acs.organomet.7b00740
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
(m), 1193 (m), 1087 (w), 843 (s), 744 (m), 695 (m), 557 (w), 515
(m).
[Ir(F-piq)2(binap)]PF6 (2). H NMR (400 MHz, CDCl3): δ (ppm)
1041.4 [M − PF6]+ (calcd 1041.3). Anal. Calcd for C59H50F6IrN2P3:
C, 59.74; H, 4.25; N, 2.36. Found: C, 59.80; H, 4.32; N, 2.28. IR (KBr
pellet, cm−1): 3058 (w), 2925 (w), 1669 (w), 1577 (s), 1540 (m),
1432 (m), 1383 (m), 1192 (m), 844 (s), 744 (m), 696 (m), 588 (w),
556 (m), 516 (m).
1
8.39 (d, J = 8.4 Hz, 2H), 7.85−7.94 (m, 6H), 7.70−7.77 (m, 6H), 7.55
(d, J = 8.8 Hz, 2H), 7.34−7.46 (m, 8H), 6.94−7.02 (m, 4H), 6.86−
6.91 (m, 4H), 6.73 (t, J = 7.6 Hz, 4H), 6.73 (d, J = 9.2 Hz, 4H), 6.50−
6.58 (m, 8H), 6.07 (d, J = 8.4 Hz, 2H), 5.31−5.34 (m, 2H). 13C NMR
(100 MHz, CDCl3): δ (ppm) 147.19, 140.86, 136.47, 135.53, 135.48,
135.44, 134.01, 132.71, 132.66, 132.62, 130.08, 129.77, 128.81, 128.11,
128.01, 127.97, 127.92, 127.86, 127.42, 127.34, 127.30, 126.66, 126.31,
120.35, 117.24, 117.05, 110.49, 110.27. 31P NMR (162 MHz, CDCl3):
δ (ppm) −11.49, −144.17 (hept). MS (ESI): m/z 1259.3 [M − PF6]+
(calcd 1259.3). Anal. Calcd for C74H50F8IrN2P3: C, 63.29; H, 3.59; N,
1.99. Found: C, 63.38; H, 3.47; N, 2.05. IR (KBr pellet, cm−1): 3058
(w), 2918 (w), 2853 (w), 1583 (m), 1543 (w), 1383 (w), 1252 (s),
1220 (m), 843 (s), 740 (m), 699 (m), 558 (w), 517 (w).
1
[Ir(CF3O-piq)2(xantphos)]PF6 (7). H NMR (400 MHz, CDCl3): δ
(ppm) 8.48 (d, J = 8.4 Hz, 2H), 8.28 (d, J = 6.4 Hz, 2H), 7.98−8.01
(m, 2H), 7.80−7.92 (m, 6H), 7.48 (d, J = 6.8 Hz, 2H), 7.26−7.30 (m,
2H), 7.18 (t, J = 7.2 Hz, 2H), 7.12 (d, J = 6.4 Hz, 2H), 6.96 (t, J = 7.2
Hz, 4H), 6.84−6.88 (m, 6H), 6.64−6.78 (m, 8H), 6.24 (t, J = 8.0 Hz,
4H), 5.50 (s, 2H), 1.52 (s, 6H). 13C NMR (100 MHz, CDCl3): δ
(ppm) 153.36, 146.08, 142.46, 136.85, 133.46, 133.41, 133.36, 133.00,
132.81, 132.76, 132.71, 131.85, 130.86, 130.41, 130.03, 129.74, 128.62,
128.58, 128.54, 128.29, 128.24, 128.19, 128.15, 127.42, 126.51, 126.03,
125.05, 121.83, 121.48, 114.58, 29.84, 28.72. 31P NMR (162 MHz,
CDCl3): δ (ppm) −20.92, −144.18 (hept). MS (ESI): m/z 1347.3 [M
− PF6]+ (calcd 1347.3). Anal. Calcd for C71H50F12IrN2O3P3: C, 57.14;
H, 3.38; N, 1.88. Found: C, 57.32; H, 3.41; N, 1.86. IR (KBr pellet,
cm−1): 3068 (w), 2968 (w), 1584 (w), 1409 (m), 1250 (s), 1183 (m),
844 (s), 747 (m), 698 (w), 512 (w).
1
[Ir(F-piq)2(dppp)]PF6 (3). H NMR (400 MHz, CDCl3): δ (ppm)
8.31 (d, J = 8.4 Hz, 2H), 8.16 (d, J = 6.4 Hz, 2H), 7.91−7.95 (m, 2H),
7.67−7.77 (m, 8H), 7.59 (t, J = 8.4 Hz, 2H), 7.43 (t, J = 7.2 Hz, 2H),
7.36 (t, J = 7.2 Hz, 4H), 7.98 (d, J = 6.4 Hz, 2H), 6.69 (dt, J1 = 8.4 Hz,
J2 = 2.4 Hz, 2H), 6.35−7.40 (m, 10H), 6.10−6.13 (m, 2H), 3.22−3.25
(m, 2H), 3.04−3.08 (m, 2H), 2.82−3.93 (m, 2H). 13C NMR (100
MHz, CDCl3): δ (ppm) 147.15, 141.18, 136.59, 133.52, 133.48,
133.43, 132.81, 131.94, 131.36, 130.81, 130.39, 129.93, 129.54, 129.51,
129.19, 128.99, 128.11, 127.28, 127.24, 127.13, 127.08, 127.04, 126.03,
121.59, 118.54, 118.36, 110.20, 109.97, 23.68, 21.48. 31P NMR (162
MHz, CDCl3): δ (ppm) −30.26, −144.17 (hept). MS (ESI): m/z
1049.3 [M − PF6]+ (calcd 1049.3). Anal. Calcd for C57H44F8IrN2P3:
C, 57.33; H, 3.71; N, 2.35. Found: C, 57.45; H, 3.83; N, 2.25. IR (KBr
pellet, cm−1): 3060 (w), 2923 (w), 2853 (w), 1579 (m), 1542 (w),
1383 (w), 1195 (m), 844 (s), 745 (m), 698 (m), 560 (w), 525 (w).
[Ir(CF3O-piq)2(binap)]PF6 (8). 1H NMR (400 MHz, CDCl3): δ
(ppm) 8.40 (d, J = 8.4 Hz, 2H), 7.97 (d, J = 8.4 Hz, 4H), 7.81−7.91
(m, 10H), 7.57 (d, J = 8.4 Hz, 2H), 7.35−7.43 (m, 8H), 6.86−6.92
(m, 6H), 6.74 (t, J = 7.2 Hz, 4H), 6.68 (d, J = 6.4 Hz, 2H), 6.62 (t, J =
8.0 Hz, 4H), 6.52 (t, J = 8.0 Hz, 4H), 6.07 (t, J = 7.6 Hz, 2H), 5.40 (s,
2H). 13C NMR (100 MHz, CDCl3): δ (ppm) 158.09, 148.21, 146.32,
136.24, 135.57, 133.90, 133.86, 133.04, 132.07, 131.11, 130.59, 129.47,
129.16, 128.91, 128.37, 127.81, 127.42, 127.16, 127.01, 126.77, 126.20,
126.03, 125.51, 125.32, 120.75, 119.73, 113.47. 31P NMR (162 MHz,
CDCl3): δ (ppm) −12.06, −144.15 (hept). MS (ESI): m/z 1391.0 [M
− PF6]+ (calcd 1391.3). Anal. Calcd for C76H50F12IrN2O2P3: C, 59.42;
H, 3.28; N, 1.82. Found: C, 59.49; H, 3.36; N, 1.74. IR (KBr pellet,
cm−1): 3058 (w), 2925 (w), 2853 (w), 1579 (w), 1385 (w), 1252 (m),
1160 (s), 1089 (w), 843 (s), 745 (m), 696 (m), 521 (w).
1
[Ir(Me-piq)2(xantphos)]PF6 (4). H NMR (400 MHz, CDCl3): δ
(ppm) 8.51 (d, J = 8.4 Hz, 2H), 8.27 (d, J = 6.8 Hz, 2H), 7.93 (d, J =
7.6 Hz, 2H), 7.76−7.85 (m, 4H), 7.68 (d, J = 8.0 Hz, 2H), 7.42 (d, J =
6.8 Hz, 2H), 7.24 (t, J = 7.2 Hz, 2H), 7.14 (t, J = 7.2 Hz, 2H), 7.00 (d,
J = 6.4 Hz, 2H), 6.92 (t, J = 7.2 Hz, 4H), 6.74−6.84 (m, 10H), 6.66−
6.70 (m, 2H), 6.60 (d, J = 7.6 Hz, 2H), 6.23 (t, J = 8.0 Hz, 4H), 5.54
(s, 2H), 1.71 (s, 6H), 1.50 (s, 6H). 13C NMR (100 MHz, CDCl3): δ
(ppm) 153.24, 146.41, 141.50, 141.25, 136.68, 133.47, 132.90, 132.30,
131.58, 130.96, 130.39, 129.72, 129.54, 128.81, 128.30, 127.86, 127.07,
125.85, 124.76, 123.93, 120.39, 29.84, 28.81, 21.84. 31P NMR (162
MHz, CDCl3): δ (ppm) −19.47, −144.21 (hept). MS (ESI): m/z
1207.4 [M − PF6]+ (calcd 1207.3). Anal. Calcd for C71H56F6IrN2OP3:
C, 63.06; H, 4.17; N, 2.07. Found: C, 63.15; H, 4.22; N, 2.02. IR (KBr
pellet, cm−1): 3063 (w), 2923 (w), 2861 (w), 1588 (m), 1407 (m),
1243 (w), 1090 (w), 844 (s), 745 (m), 697 (w), 558 (w), 575 (w).
[Ir(Me-piq)2(binap)]PF6 (5). 1H NMR (400 MHz, CDCl3): δ (ppm)
8.43 (d, J = 7.6 Hz, 2H), 7.81−7.91 (m, 4H), 7.67−7.72 (m, 8H), 7.57
(d, J = 8.8 Hz, 2H), 7.47−7.49 (m, 8H), 6.88−7.00(m, 8H), 6.81−
7.85 (m, 4H), 6.67 (t, J = 7.2 Hz, 4H), 6.61 (d, J = 8.0 Hz, 2H), 6.43−
6.49 (m, 4H), 6.11 (d, J = 8.4 Hz, 2H), 5.43 (s, 2H), 1.62 (s, 6H). 13C
NMR (100 MHz, CDCl3): δ (ppm) 147.59, 142.03, 139.95, 136.37,
135.67, 133.94, 132.65, 132.23, 131.90, 130.82, 129.82, 129.21, 128.68,
128.16, 127.94, 127.82, 127.67, 127.45, 127.19, 126.51, 126.47, 123.97,
119.41, 21.78. 31P NMR (162 MHz, CDCl3): δ (ppm) −10.63,
−144.23 (hept). MS (ESI): m/z 1251.4 [M − PF6]+ (calcd 1251.4).
Anal. Calcd for C76H56F6IrN2P3: C, 65.37; H, 4.04; N, 2.01. Found: C,
65.43; H, 4.13; N, 1.96. IR (KBr pellet, cm−1): 3052 (w), 2923 (w),
2850 (w), 1587 (m), 1440 (w), 1381 (w), 1151 (w), 1087 (w), 843
(s), 745 (m), 698 (m), 557 (w), 521 (w).
[Ir(CF3O-piq)2(dppp)]PF6 (9). 1H NMR (400 MHz, CDCl3): δ
(ppm) 8.40 (d, J = 8.4 Hz, 2H), 8.12 (d, J = 6.4 Hz, 2H), 7.66−7.77
(m, 10H), 7.58 (t, J = 7.2 Hz, 2H), 7.38−7.41 (m, 2H), 7.28−7.31 (m,
4H), 6.90 (d, J = 6.8 Hz, 2H), 6.76 (d, J = 8.0 Hz, 2H), 6.36−6.43 (m,
10H), 6.20 (s, 2H), 3.17−3.22 (m, 2H), 2.98−3.07 (m, 2H), 2.83−
2.92 (m, 2H). 13C NMR (100 MHz, CDCl3): δ (ppm) 148.97, 147.13,
143.25, 136.59, 133.46, 133.42, 133.38, 132.06, 131.46, 129.48, 129.44,
129.40, 129.27, 129.23, 129.18, 129.02, 128.32, 127.37, 127.18, 127.14,
127.09, 127.06, 126.19, 123.08, 122.23, 121.61, 119.05, 114.95, 23.85,
21.52. 31P NMR (162 MHz, CDCl3): δ (ppm) −30.15, −144.13
(hept). MS (ESI): m/z 1181.1 [M − PF6]+ (calcd 1181.2). Anal. Calcd
for C59H44F12IrN2O2P3: C, 53.44; H, 3.34; N, 2.11. Found: C, 53.51;
H, 3.47; N, 2.03. IR (KBr pellet, cm−1): 3063 (w), 2928 (w), 1578
(m), 1437 (w), 1383 (w), 1252 (s), 1188 (m), 1094 (w), 846 (s), 746
(m), 696 (m), 647 (w), 557 (m), 518 (m).
ASSOCIATED CONTENT
■
S
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.7b00740.
Crystallographic data summary and selected bond
distances and angles for 1, 7 and 9, cyclic voltammo-
grams for 1−9, 1H, 13C, and 31P (1−9) NMR spectra for
3a−3c and 1−9, and ESI-MS spectra for 1−9 (PDF)
[Ir(Me-piq)2(dppp)]PF6 (6). 1H NMR (400 MHz, CDCl3): δ (ppm)
8.41 (d, J = 8.8 Hz, 2H), 8.13 (d, J = 6.4 Hz, 2H), 7.65−7.77 (m,
10H), 7.57 (t, J = 7.2 Hz, 2H), 7.38−7.40 (m, 2H), 7.28−7.32 (m,
4H), 6.90 (d, J = 6.4 Hz, 2H), 6.76 (d, J = 7.6 Hz, 2H), 6.36−7.41 (m,
10H), 6.20 (s, 2H), 3.17−3.21 (m, 2H), 3.04−3.08 (m, 2H), 2.85−
2.92 (m, 2H), 1.98 (s, 6H). 13C NMR (100 MHz, CDCl3): δ (ppm)
147.12, 142.30, 139.52, 136.36, 133.54, 133.50, 133.46, 133.16, 131.57,
131.02, 130.78, 129.62, 128.86, 128.73, 127.73, 127.43, 127.06, 126.99,
126.95, 126.09, 123.71, 120.72, 29.80, 24.33, 21.78. 31P NMR (162
MHz, CDCl3): δ (ppm) −30.70, −144.14 (hept). MS (ESI): m/z
Accession Codes
CCDC 1576155−1576157 contain the supplementary crystal-
lographic data for this paper. These data can be obtained free of
charge via www.ccdc.cam.ac.uk/data_request/cif, or by email-
ing data_request@ccdc.cam.ac.uk, or by contacting The
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
H
DOI: 10.1021/acs.organomet.7b00740
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
(22) Leung, S. K.; Kwok, K. Y.; Zhang, K. Y.; Lo, K. K. W. Inorg.
Chem. 2010, 49, 4984−4995.
AUTHOR INFORMATION
■
Corresponding Author
*E-mail for Z.-G.N.: niuzhigang1982@126.com.
ORCID
(23) Niu, Z. G.; Liu, D.; Zuo, J.; Zou, Y.; Yang, J. M.; Su, Y. H.; Yang,
Y. D.; Li, G. N. Inorg. Chem. Commun. 2014, 43, 146−150.
(24) Zhao, Q.; Liu, S. J.; Shi, M.; Wang, C. M.; Yu, M. X.; Li, L.; Li,
F. Y.; Yi, T.; Huang, C. H. Inorg. Chem. 2006, 45, 6152−6160.
Zhi-Gang Niu: 0000-0003-4842-1464
(25) Colombo, M. C.; Hauser, A.; Gudel, H. U. Top. Curr. Chem.
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Author Contributions
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§G.-N.L. and S.-B.D. contributed equally to this work.
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Lee, J. Y.; Jin, S. H. J. Mater. Chem. C 2013, 1, 2368−2378.
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Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
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This work was supported by the National Natural Science
Foundation of China (21501037), the 2016 National
Innovation Experiment Program for University Students,
Hainan Province Natural Science Foundation of Innovative
Research Team Project (2017CXTD007), and Program for
Innovative Research Team in University (IRT-16R19).
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DOI: 10.1021/acs.organomet.7b00740
Organometallics XXXX, XXX, XXX−XXX