35 卷 1 期
2016. 1
结
构
化 学 （JIEGOU HUAXUE）
Chinese J. Struct. Chem.
Vol. 35, No. 1
114─118
Blue-green Phosporescent Iridium
Complex with Terdentate Ligand①
CHEN Man WANG Xue-Mei HE Yu-Heng
YANG Jian WANG Song TONG Bi-Hai②
(School of Metallurgy Engineering, Anhui University
of Technology, Maanshan, Anhui 243002, China)
ABSTRACT
An ionic iridium(III) complex [Ir(F2dpyb)(bzdpp)2Cl][OTf] with 1,3-difluoro-
4,6-di(2-pyridinyl) benzene (F2dpybH) terdentate ligand and benzyldiphenylphosphine (bzdpp)
ligand was synthesized and characterized. The structure of iridium complex was verified by
single-crystal X-ray crystallography. It crystallizes in monoclinic, space group P21/n with a =
14.3654(7), b = 23.0026(10), c = 15.7964(7) Å,β = 97.6029(11), V = 5173.9(4) Å3, Z = 4, F(000) =
2552, Dc = 1.645 Mg/m3, Mr = 1281.49 and μ = 0.071 mm−1. The UV-vis absorption and
phosphorescence of the complex were discussed. The complex was ‘aggregation induced emission
(AIE)’ active. It exhibited no emission in CH2Cl2 solution but strong blue-green emission in solid
state under ultraviolet light excitation. The complex emitted a strong phosphorescence centered at
493 nm when doped in PMMA. Its lifetime is 0.755 μs and quantum yield is approximately 0.134.
Keywords: iridium complex, aggregation induced emission (AIE), crystal structure,
phosphorescence; DOI: 10.14102/j.cnki.0254-5861.2011-0816
1 INTRODUCTION
compatibility.
Many researches were focused on developing a
Cyclometalated Ir(III) complexes are of great
vast range of derivatives of the Ir(C^N)3 and
interest because of their application prospect in
Ir(C^N)2(L^X) structural classes[4] {C^N = anionic
full-color flat-panel displays and sensors[1, 2]. Owing
bidentate cyclometallating ligands such as 2-phen-
to the strong spin-orbital mixing of heavy metal
ylpyridine; L^X = anionic ancillary ligands like
ions in phosphorescent iridium complexes, both
acetylacetone}. Parallel to these endeavors,
singlet and triplet excitons can be fully utilized,
Williams et al. have synthesized the Ir(III) complex
creating the possibility for iridium complexes to
[Ir(dpyx)(ppy)Cl] [5] , in which dpyx denotes
reach an internal quantum efficiency of 100%[3]. At
tridentate 1,3-bis(2-pyridyl)-4,6-dimethylbenzene,
the same time, the Ir(III) complexes are promising
and reported the possession of higher emission
candidates in various sensor applications on account
efficiency (Φ = 0.76) versus the tris-bidentate
of their high luminescence quantum yields, long-
analogue fac-[Ir(ppy)3] (Φ = 0.40). Haga et al. have
lived emitting states, good solubility and bio-
also shown successful preparation of analogous
Received 20 May 2015; accepted 19 December 2015 (CCDC 1041045)
① Supported by the National Natural Science Foundation of China (21572001), the Natural Science Foundation from Bureau of Education
of Anhui Province (KJ2013A063) and the Anhui Province Undergraduate Innovation and Entrepreneurship Training Program (201510360119)
② Corresponding authors. E-mail: tongbihai@163.com
2016
Vol. 35
结
构
化
学（JIEGOU HUAXUE）Chinese
Ir(III) complexes with single tridentate chelate, plus
[6-10]
one extra bidentate and monodentate ligands
.
Studies on the preparation of Ir(III) complexes with
J.
Struct. Chem.
115
98:2) to give the desired product as a light yellow
solid of iridium complex [Ir(F2dpyb)(bzdpp)2Cl][OTf] (111 mg, 93%).
the sole tridentate chelates, i.e. bis-tridentate Ir(III)
Anal. Calcd. (%) for C55H43N2ClF5P2SO3Ir: C,
complexes, have been executed but with limited
52.20; H, 3.62; N, 2.34. Found (%): C, 52.14; H,
[11]
. The iridium complexes composed of
3.68; N, 2.29. 1H NMR (400 MHz, CDCl3) δ: 9.23
tridentate cyclometalated ligands such as the type of
(d, J = 6.0Hz, 2H), 7.96 (t, J = 8.4Hz, 2H), 7.75 (d,
N^C^N-coordinating ligands are believed to possess
J = 8.4Hz, 2H), 7.37 (t, J = 5.6Hz, 2H), 7.24 (t, J =
better thermal stability and symmetry than those
6.8Hz, 4H), 7.02 (t, J = 8.0Hz, 8H), 6.86～6.90 (m,
success
[12]
with two bidentate ligands
. Therefore, designing
8H), 6.82 (t, J = 7.2Hz, 2H), (t, J = 7.6Hz, 4H), 6.32
and studying Ir(N^C^N) materials are a worthwhile
(d, J = 8.0Hz, 4H), 6.23 (t, J = 11.2Hz, 1H), 3.93 (t,
undertaking. In this paper we report the synthesis,
J = 3.6Hz, 4H). 19F NMR (376 MHz, CDCl3) δ:
crystal structure and photophysics properties of a
–78.05 (s, 3F), –104.30 (d, J = 3.0Hz, 2F). 31P NMR
novel iridium complex [Ir(F2dpyb)(bzdpp)2Cl][OTf]
(162 MHz, CDCl3) δ: –10.76 (s, 2P). MS ((+)-ESI):
(F2dpybH = 1,3-difluoro-4,6-di(2-pyridinyl) ben-
m/z
1047.6
+
(calcd.
1047.2
for
+
[C54H43N2ClF2P2Ir] , [M-OTf] ).
zene, bzdpp = benzyldiphenylphosphine).
2. 3
2
=
Structure determination
Crystals suitable for X-ray diffraction were
EXPERIMENTAL
obtained by slow evaporation from a methanol and
2. 1
dichloromethane solution at room temperature. A
Apparatus and materials
Positive-ion ESI mass spectra were recorded on a
light yellow crystal of iridium complex with appro-
Perkin Elmer Sciex API 365 mass spectrometer.
ximate dimensions of 0.37mm × 0.26mm × 0.03mm
NMR spectra were recorded on a Bruker AV400
was selected and mounted on a glass fiber. The
spectrometer using CDCl3 as solvent. UV/Vis
intensity data were collected on a Bruker Smart
absorption spectra were recorded on a Shimadzu
APEX CCD-based diffractometer equipped with a
UV-2501
Photolumine-
graphite-monochromator equipped with a MoKα
scence (PL) spectra were measured with a Shimadzu
radiation (λ = 0.71073 Å) by using an ω scan mode
RF-5301PC fluorescence spectrophotometer. Lu-
at 150(2) K. The empirical absorption was applied
minescence lifetime was determined on an Edin-
to the intensity data. A total of 39659 reflections
burgh FL920 time-correlated pulsed single-photon-
were collected in the range of 1.77<θ<27.50 (–18≤
coun- ting instrument. All the chemicals were com-
h≤18, –29≤k≤29, –20≤l≤–20), of which 11882
mercially available and used without further puri-
were independent (Rint = 0.0248) and 9208 were
fication. All the solvents were dried using standard
observed with I > 2σ(I). The intensity data were
methods before use.
corrected for Lorentz and polarization effects as
2. 2
PC
spectrophotometer.
well as for empirical absorption based on the
Synthesis of iridium complex
A mixture of [Ir-(F2dpyb)Cl(μ-Cl)]2
[12]
(53 mg,
multi-scan technique. The structure was solved by
0.05 mmol), benzyldiphenylphosphine (54, 0.20
direct methods and refined by full-matrix least-
mmol) and AgOTf (51 mg, 0.020 mmol) in xylene
squares techniques on F2 with SHELX-97[13, 14]. All
(20 mL) was heated to 180 °C under a nitrogen
non-H atoms were refined with anisotropic displace-
atmosphere for 12 h. Then the solvent was removed
ment parameters. The hydrogen atoms were located
under reduced pressure. The remaining solid was
theoretically and refined with riding model position
purified by column chromatography (silica, dichloro-
parameters as well as fixed isotropic thermal para-
methane/methanol, gradient elution from 100:0 to
meters. The final R = 0.0627, wR = 0.1446 (w =
116
CHEN M. et al.: Blue-green Phosporescent Iridium Complex with Terdentate Ligand
2
1/[σ
2
(Fo2)
(Fo +
2
+ (0.0575P) + 31.6261P], where P =
2Fc2)/3),
No. 1
chlorine ligand is in trans position of coordinated C
(Δ/σ)max = 0.001, S = 1.099, (Δρ)max
atom. The bond lengths of Ir-C (1.915(8) Å), Ir-Cl
3
(2.467(2) Å) and Ir-N, spanning from 2.072(6) to
= 2.707 and (Δρ)min = –1.938 e/Å .
2.077(6) Å, are within the range reported for closely
3 RESULTS AND DISCUSSION
related complexes[5-11]. The two Ir–P bonds were
ranging from 2.3757(18) to 2.3881(19) Å. The
3. 1
F2dpyb chelation results in a N(2)–Ir–N(1) bond
Molecular structure
The crystal structure of iridium complex is given
angles of 160.6(3)°, appreciably lower than the
in Fig. 1; the selected bond lengths and bond angles
idealized 180° value. The two benzyl groups are
are listed in Table 1. The new iridium complex
both close to chlorine ligand because of lesser steric
consists of a cationic distorted octahedrally coor-
hindrance. Furthermore, the C–C, C–N, C–F and
dinated iridium(III) center ligated by a F2dpyb
C–P bond lengths and angles are within normal
ligand, two bzdpp ligands and a chlorine ligand
ranges and in agreement with the corresponding
-
with a negative [OTf] counter anion. The two
parameters described for similarly constituted
bzdpp ligands chelate the iridium center with P-P in
complexes[5-11]. Furthermore, the aromatic stacking
the trans configuration to reduce the steric
interactions between bzdpp ligands observed in the
hindrance. The F2dpyb ligand chelates the iridium
supramolecular structure with the distances of 3.802
center with almost a planar configuration. The
Å link the adjacent units to yield a 1 D chain (Fig. 3).
Table 1.
Selected Bond Lengths (Å) and Bond Angles (°)
Bond
Dist.
Bond
Dist.
Bond
Dist.
Ir–C(11)
1.915(8)
Ir–N(1)
2.077(6)
Ir–P(1)
2.3881(19)
Ir–N(2)
2.072(6)
Ir–P(2)
2.3757(18)
Ir–Cl(1)
2.467(2)
Angle
( °)
Angle
(°)
Angle
(°)
C(11)–Ir–N(2)
80.1(3)
N(1)–Ir–P(2)
92.91(17)
C(11)–Ir–Cl(1)
179.6(2)
C(11)–Ir–N(1)
80.6(3)
C(11)–Ir–P(1)
89.5(2)
N(2)–Ir–Cl(1)
99.83(18)
N(2)–Ir–N(1)
160.6(3)
N(2)–Ir–P(1)
93.85(17)
N(1)–Ir–Cl(1)
99.5(2)
C(11)–Ir–P(2)
90.0(2)
N(1)–Ir–P(1)
86.58(17)
P(2)–Ir–Cl(1)
90.32(7)
N(2)–Ir–P(2)
86.48(17)
P(2)–Ir–P(1)
179.32(7)
P(1)–Ir–Cl(1)
90.21(7)
Fig. 1.
Crystal structure of the [Ir(F2dpyb)(bzdpp)2Cl]+ cation with selected displacement
ellipsoids drawn at the 30% probability level. H atoms are omitted
2016
Vol. 35
结
学（JIEGOU HUAXUE）Chinese
化
J.
Struct. Chem.
117
π-π stacking interactions between benzyldiphenylphosphine ligands
Fig. 2.
3. 2
构
The iridium complex was almost nonluminous in
Photophysical properties
organic solutions under ultraviolet radiation at room
of iridium complex
UV-vis absorption spectra of iridium complex are
temperature. In contrast, it emits intense lumines-
shown in Fig. 3. The strong band around 272 nm
cence in solid or doped in PMMA (polymethyl
4
(3.82 × 10 M
-1
-1
cm ) is assigned to a typical
methacrylate). The photoluminnescence spectra are
spin-allowed π-π* transition of the ligands, and the
also shown in Fig. 3. Doped in PMMA, iridium
1
3
-1
-1
cm )
complex emits intense luminescence with emission
corresponds likely to spin-allowed singlet metal-
wavelength in 493 nm, corresponding to blue-green
moderate band at 382 nm (8.7 × 10 M
1
to-ligand charge-transfer ( MLCT). On the other
light emitting. In pure solid or doped in PMMA, the
hand, the weak absorptions at ca. 420～460 nm (< 1
rotation of diphenyl rotors of the bzdpp ligand is
-1
-1
M cm ) can be assigned to a spin-forbidden triplet
3
highly restricted resulting in an emission enhan-
metal-to-ligand charge- transfer ( MLCT). From the
cement. These experiments primarily support the
absorption edge (466 nm), the energy gap was
‘aggregation induced emission (AIE)’ activity of
[5]
this complex.
calculated to be 2.66 eV .
60
50
40
40
30
30
20
20
10
10
Emission Intensity (a. u.)
A
B
50
3
-1
-1
Extinction Coefficient (x 10 M cm )
60
0
0
300
400
500
600
700
Wavelength (nm)
Fig. 3.
Absorption (A, in CH2Cl2 solution) and emission spectra (B, 1% in PMMA)
of iridium complex recorded at room temperature
The photophysical data of iridium complex in
decay rate constant kr is calculated to be 1.775 × 105
By integra-
s-1, and the nonradiative decay rate constant knr is
ting sphere measurements, the iridium complex in
11.475 × 105 s-1. The constant kr is less than knr, so
PMMA shows medium phosphorescence quantum
most of the excited state energy was released with
efficiency (ca. 0.134). The excited state lifetime is
no emission form.
PMMA
are
listed
in
Table
2.
determined to be 755 ns. Accordingly, the radiative
118
CHEN M. et al.: Blue-green Phosporescent Iridium Complex with Terdentate Ligand
Table 2.
No. 1
Photophysical Data of Complex Recorded in PMMA (1%) at RT
em λmax (nm) τobs (μs) em Φ (%) kr [a] (×105 s‐1) knr [a] (×105 s‐1) Iridium complex 493 0.755 13.4 1.775 11.475 [a] (kr + knr) = 1/τobs, where τobs is the emission lifetime. The radiative decay rate constant kr is calculated by Φ (%) = kr / (kr + knr)
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