New luminescent cyclometalated iridium(III) complexes containing fluorinated phenylisoquinoline-based ligands: Synthesis, structures, photophysical properties and DFT calculations

Article abstract of DOI:10.1016/j.cclet.2015.12.007

Two new fluorinated phenylisoquinoline-based iridium(III) complexes, [Ir(f₂piq)₂(bipy)][PF₆] (3a) and [Ir(fmpiq)₂(bipy)][PF₆] (3b) (f₂piq = 1-(2,4-difluorophenyl)isoquinoline, fmpiq = 1-(4-

Full text of DOI:10.1016/j.cclet.2015.12.007

Accepted Manuscript
Title: New luminescent cyclometalated iridium(III) complexes
containing fluorinated phenylisoquinoline-based ligands:
Synthesis, structures, photophysical properties and DFT
calculations
Author: Gao-Nan Li Cheng-Wei Gao Hao-Hua Chen Dong
Liu Wei Sun Guang-Ying Chen Zhi-Gang Niu
PII:
S1001-8417(15)00476-3
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.cclet.2015.12.007
CCLET 3500
To appear in:
Chinese Chemical Letters
Received date:
Revised date:
Accepted date:
21-10-2015
11-11-2015
2-12-2015
Please cite this article as: G.-N. Li, C.-W. Gao, H.-H. Chen, D. Liu, W. Sun,
G.-Y. Chen, Z.-G. Niu, New luminescent cyclometalated iridium(III) complexes
containing fluorinated phenylisoquinoline-based ligands: Synthesis, structures,
photophysical properties and DFT calculations, Chinese Chemical Letters (2015),
http://dx.doi.org/10.1016/j.cclet.2015.12.007
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Graphical Abstract
New luminescent cyclometalated iridium(III) complexes containing fluorinated phenylisoquinoline-based ligands: Synthesis,
structures, photophysical properties and DFT calculations
Gao-Nan Li a,c, Cheng-Wei Gao a, Hao-Hua Chen a, Dong Liu a, Wei Sun a, Guang-Ying Chen b, Zhi-Gang Niu a,b,c,*
a College of Chemistry and Chemical Engineering, Hainan Normal University, Haikou 571158, China
b Key Laboratory of Tropical Medicinal Plant Chemistry of Ministry of Education, Hainan Normal University, Haikou 571158,
China
c State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University,
Nanjing 210093, China
N
N
N
Ir
R2
2
PF6
R1
3a~3b
3a: R1 = F, R2 = F
3b: R1 = F, R2 = CH3
Two new fluorinated phenylisoquinoline-based iridium(III) complexes have been synthesized and fully characterized. Their
photophysical properties have been investigated, and the lowest-energy electronic transitions of absorption spectra have been
analyzed by means of time-dependent density functional theory (TD-DFT).
*
Corresponding author.
E-mail address: niuzhigang1982@126.com (Z.-G. Niu).
Page 1 of 8

Original article
New luminescent cyclometalated iridium(III) complexes containing fluorinated
phenylisoquinoline-based ligands: Synthesis, structures, photophysical properties and
DFT calculations
Gao-Nan Li a,c, Cheng-Wei Gao a, Hao-Hua Chen a, Dong Liu a, Wei Sun a, Guang-Ying Chen b, Zhi-Gang
Niu a,b,c,*
a College of Chemistry and Chemical Engineering, Hainan Normal University, Haikou 571158, China
b Key Laboratory of Tropical Medicinal Plant Chemistry of Ministry of Education, Hainan Normal University, Haikou 571158, China
c State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, China
ARTICLE INFO
ABSTRACT
Two
new
fluorinated
phenylisoquinoline-based
iridium(III)
complexes,
1-(2,4-
Article history:
[Ir(f2piq)2(bipy)][PF6] (3a) and [Ir(fmpiq)2(bipy)][PF6] (3b) (f2piq
=
Received 21 October 2015
Received in revised form 11 November 2015
Accepted 2 December 2015
Available online
difluorophenyl)isoquinoline, fmpiq = 1-(4-fluoro-2-methylphenyl)isoquinoline, bipy = 2,2’-
bipyridine), have been synthesized and fully characterized. Single crystal X-ray diffraction
study has been undertaken on complexes 3a−3b, which show that each adopts the distorted
octahedral coordination geometry with the cis-C,C' and trans-N,N' configuration. The
photoluminescence spectra of 3a−3b exhibit yellow and orange emission maxima at 584 and
600 nm, respectively. The frontier molecular orbital diagrams and the lowest-energy electronic
transitions of 3a−3b have been calculated with density functional theory (DFT) and time-
dependent DFT (TD-DFT). The absorption and emission spectra of complex 3b is red-shifted
relative to those of complex 3a, as a consequence of the nature of the methyl group.
Keywords:
Iridium(III) complex
Phenylisoquinoline
Crystal structure
Photoluminescence
DFT calculation
1. Introduction
After the pioneering work of Forrest, Thompson, and coworkers [1] over the past decade, many efforts have been devoted toward the
design, synthesis, and photophysical investigation of new phosphorescent cyclometalated iridium(III) complexes [2-11]. Substantial
research has demonstrated that the chemical structures of cyclometalated ligands (C^N ligands) can strongly affect the photophysical
properties of iridium(III) complexes. On the other hand, the introduction of a strongly electron-withdrawing group in the C^N ligand
could cause a great increase of the luminescence efficiency [12,13].
In pursuit of highly emissive iridium complexes, most recently, we have reported a series of cyclometalated phenylisoquinoline-
based iridium(III) complexes containing different electron-withdrawing substituents (−CF3, −CHO, −CN and −F) [14]. Their
photophysical and electrochemical properties have been investigated, showing that the introduction of the electron-withdrawing
fluorine group in the C^N ligand could improve phosphorescence quantum yields effectively. These results prompted us to study how
the fluorine group in different positions of C^N ligands affect the pertinent emission properties. Hence, two new fluorine-modificative
phenylisoquinoline iridium(III) complexes (3a−3b) have been prepared in this paper (Scheme 1). The spectroscopic and luminescence
properties of these complexes are studied, and the lowest-energy electronic transitions are calculated with density functional theory
(DFT) and time-dependent DFT (TD-DFT).
*
Corresponding author.
E-mail address: niuzhigang1982@126.com (Z.-G. Niu).
Page 2 of 8

N
N
N
Cl
Cl
IrCl3, 135 o
C
Ir
Ir
R2
R2
R2
EtOEtOH, H2O,
2
2
R1
R1
N
R1
2a~2b
1a~1b
N
N
a: R1 = F, R2 = F
1) 2,2'-bipyridine, DCM, MeOH
2) DCM, MeOH, NH4PF6
Ir
R2
b: R1 = F, R2 = CH3
2
PF6
R1
3a~3b
Scheme 1. Synthetic routes of Ir(III) complexes 3a−3b.
2. Experimental
1H NMR spectra were recorded on a Bruker AM 400 MHz instrument. Chemical shifts were reported in ppm relative to Me4Si as the
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. UV–vis spectra were recorded on a Hitachi U3900/3900H spectrophotometer.
Fluorescence spectra were carried out on a Hitachi F−7000 spectrophotometer.
All air-sensitive and/or water-sensitive reactions were carried out under a dry nitrogen atmosphere. All commercial chemicals were
used without further purification unless otherwise stated. Solvents were dried and degassed following standard procedures. Column
chromatography was carried out using 200-300 µm mesh silica.
2.1 Preparation of 1-(2,4-difluorophenyl)isoquinoline (f2piq, 1a)
A mixture of 1-chloroisoquinoline (2.0 mmol), (2,4-difluorophenyl)boronic acid (2.2 mmol), Pd(dppf)2Cl2 (5~10 mg) and potassium
acetate (4.0 mmol) was dissolved in anhydrous 1,4-dioxane (10 mL) and heated at 90 oC under nitrogen for 10 h. After cooling to room
temperature, the mixture was poured into water (20 mL) and extracted with dichloromethane. The combined organic layers were dried
over Na2SO4 and concentrated in vacuum. The crude product was purified by column chromatography to afford pure product 1a as a
1
white solid. Yield: 93%. H NMR (400 MHz, CDCl3):
δ 8.56 (d, 1H, J = 5.2 Hz), 7.83 (d, 1H, J = 8.0 Hz), 7.71 (d, 1H, J = 8.4 Hz),
7.64~7.66 (m, 2H), 7.46~7.51 (m, 2H), 7.00 (t, 1H, J = 8.4 Hz), 6.93 (t, 1H, J = 9.2 Hz). MS-ESI: m/z calculated: 241.1; found: 242.1
(M+1), 264.1 (M+Na).
2.2 Preparation of 1-(4-fluoro-2-methylphenyl)isoquinoline (fmpiq, 1b)
A
procedure analogous to that for 1a was employed with (4-fluoro-2-methylphenyl)boronic acid instead of 2,4-
difluorophenyl)boronic acid to afford 1b as a white solid. Yield: 90%. 1H NMR (400 MHz, CDCl3):
δ
8.62 (d, 1H, J = 5.6 Hz), 7.89 (d,
1H, J = 8.0 Hz), 7.83 (d, 1H, J = 8.0 Hz), 7.68~7.72 (m, 2H), 7.54 (t, 1H, J = 8.0 Hz), 7.44 (t, 1H, J = 7.6 Hz), 7.13 (d, 1H, J = 8.0 Hz),
7.05 (d, 1H, J = 8.0 Hz), 2.47 (s, 3H). MS-ESI: m/z calculated: 237.1; found: 238.1 (M+1), 260.1 (M+Na).
2.3. Preparation of [Ir(f2piq)2(bipy)][PF6] (3a)
A mixture of IrCl3·3H2O (1.0 mmol) and the ligand 1a in 6 mL of ethoxyethanol and H2O (v/v = 2 : 1) was refluxed for 12 h under
nitrogen. Upon cooling to room temperature, the orange precipitate was collected by filtration and washed with cooled MeOH. After
drying, the crude product of cholorobridged dimer complex 2a was used directly in next step without further purification. A mixture of
the above dimer complex 2a and 2,2'-bipyridine (N^N ligand, 2.0 equiv.) was dissolved in 6 mL of DCM and MeOH (v/v = 2 : 1) and
heated at 40 oC under nitrogen for 6 h. After cooling to room temperature, NH4PF6 (2.5 equiv.) was added to the above solution. The
mixture was stirred at room temperature for 3 h, and then evaporated to dryness. The solid was purified by column chromatography to
afford pure product 3a, Yield: 63%. 1H NMR (400 MHz, CDCl3):
δ 8.70 (d, 2H, J = 8.0 Hz), 8.27 (t, 2H, J = 9.2 Hz), 8.16 (t, 2H, J =
8.0 Hz), 7.88 (d, 2H, J = 8.0 Hz), 7.67~7.79 (m, 8H), 7.54 (t, 2H, J = 6.4 Hz), 7.46 (d, 2H, J = 6.0 Hz), 7.20 (d, 2H, J = 6.0 Hz), 6.61
(t, 2H, J = 9.2 Hz). MS-ESI: m/z calculated: 829.2; found: 829.3 (M−PF6). Anal. Calcd. for C40H24F10IrN4P: C, 49.33; H, 2.48, N, 5.75.
Found: C, 49.56, H, 2.53, N, 5.91.
[Ir(fmpiq)2(bipy)][PF6] (3b) was obtained by a method similar to the preparation of 3a. Yield: 73%. 1H NMR (400 MHz, CDCl3):
δ
8.74 (d, 2H, J = 7.2 Hz), 8.18 (t, 2H, J = 7.6 Hz), 8.16~8.20 (m, 3H), 8.16~8.20 (m, 3H), 7.84~7.89 (m, 3H), 7.76 (t, 3H, J = 7.6 Hz),
7.66 (t, 3H, J = 7.6 Hz), 7.43~7.47 (m, 4H), 7.25~7.28 (m, 2H), 6.68 (t, 2H, J = 9.6 Hz), 2.31 (s, 6H). MS-ESI: m/z calculated: 821.2;
found: 821.3 (M−PF6). Anal. Calcd. for C42H30F8IrN4P: C, 52.23; H, 3.13, N, 5.80. Found: C, 52.48, H, 3.21, N, 5.82.
2.4. Crystal structure determination
Page 3 of 8

X-ray diffraction data were collected with an Agilent Technologies Gemini A Ultra diffractometer equipped with graphite-
monochromated Mo Kα radiation (λ = 0.71073 Å) and Cu Kα radiation (λ = 1.5418 Å) at room temperature. Data collection and
reduction were processed with CrysAlisPro software [15]. The structure was solved and refined using Full-matrix least-squares based
on F2 with program SHELXS-97 and SHELXL-97 [16] within Olex2 [17]. During the refinement, the SQUEEZE option in the program
PLATON was used to exclude the contribution from the highly disordered PF6 anion that cannot be modeled even with restraints [18-
19]. The 131 electrons voided by SQUEEZE closely corresponds to 1.87 PF6 anion (131 electrons). 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.
Crystallographic data (excluding structure factors) for the structural analyses have been deposited with the Cambridge Crystallographic
Data Centre, Nos. 1062895 and 1062896 for 3a and 3b, respectively.
2.5. Computational details
All calculations were carried out with Gaussian 09 software package [20]. The 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 [21-23]. The LANL2DZ basis set was used to
treat the Ir atom, whereas the 6-31G* basis set was used to treat C, H, N and F 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
[24,25].
2.6. Luminescence quantum efficiency
The luminescence quantum efficiencies were calculated by comparison of the fluorescence intensities (integrated areas) of a
standard sample fac-Ir(ppy)3 and the unknown sample according to the equation [26-28].
I
Astd ηunk
2
Φunk = Φstd
(
unk )(
Istd Aunk ηstd
)(
)
Where Φunk and Φstd are the luminescence quantum yield values of the unknown sample and fac-Ir(ppy)3 solutions (Φstd = 0.4) [28],
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. The
ηunk and ηstd terms represent the refractive indices of the corresponding solvents (pure solvents were assumed).
3. Results and discussion
3.1. Description of the crystal structure
The crystals of 3a−3b suitable for X-ray structural analysis were obtained by slow evaporation of CH2Cl2/MeOH solution. The
crystallographic data and structure refinement details are given in Table 1; selected bond lengths and bond angles obtained by X-ray
diffractions are collected in Table S1 in Supporting information.
The perspective views of the cation of [Ir(f2piq)2(bipy)][PF6] and [Ir(fmpiq)2(bipy)][PF6] are depicted in Fig. 1. In the two similar
crystal structures, iridium(III) adopts a distorted [(C N)2Ir(N N)]+ octahedral geometry with the cis-C,C' and trans-N,N' configuration
for phenylisoquinoline-based ligand. Simultaneously, the angles of atoms on the para positions of the octahedron range from
172.34(12)º to 173.61(15)º for 3a and 168.56(15)º to 171.91(17)º for 3b .
The Ir−C bonds of these complexes (Ir−Cav = 2.018 Å) are shorter than the Ir−N bonds (Ir−Nav = 2.099 Å). In particular, the Ir−N
bond lengths from C N ligands are significantly shorter than that from N N ligands, consistent with strong trans influence of the
carbon donors. All other bond lengths and angles within the chelate ligands are typical for this type of complexes [14, 29]. The bite
angles of the phenylisoquinoline-based ligands (80.26º for 3a, 79.51º for 3b) and the bipyridine ligands (77.03º for 3a, 76.12º for 3b)
lie in the same range as that observed in the literature for similar complexes [30]. In addition, the X-ray data show the large torsion
angles (C8-C9-C10-C11, -31.35º for 3a and -31.30º for 3b), which suggest that the –F group can cause larger molecular deformation.
3a
3b
Page 4 of 8

Fig. 1. ORTEP views of 3a and 3b with the atom-numbering scheme at the 50% probability level. Hydrogen atoms and PF6 anion are
omitted for clarity.
Table 1
Crystallographic data and structure refinement details for complexes 3a,3b.
3a
3b
Empirical formula
Mr
C40H24F4IrN4
828.85
C42H30F8IrN4P
965.87
Crystal system
Space group
Monoclinic
C2/c
Triclinic
P
1
Wavelength / Å
X-Radiation (graphite
monochromator)
T / K
0.7107
1.5418
Cu-K
Mo-K
α
α
293(2)
293(2)
a (Å)
b (Å)
c (Å)
13.7242(3)
14.6295(3)
21.0184(5)
90.00
105.467(3)
90.00
4067.20(16)
4
1.354
10.1347(3)
11.2862(3)
17.3147(5)
80.139(2)
88.001(2)
69.641(3)
1828.68(9)
2
α
β
γ
(°)
(°)
(°)
V (Å3)
Z
Dcalcd (Mg/m3)
F(000)
1.754
948
1620
Absorption coefficient
3.330
8.175
(mm−1)
Index ranges
−14 ≤ h ≤ 17
−18 ≤ k ≤ 14
−26 ≤ l ≤ 20
0.0173
1.186
0.0235, 0.0840
−12 ≤ h ≤ 10
−13 ≤ k ≤ 12
−20 ≤ l ≤ 20
0.0571
1.077
0.0414, 0.1013
Rint
GOF (F2)
R1a, wR2b (I >2
σ(I))
R1a, wR2b (all data)
0.0310, 0.0879
0.0460, 0.1065
a R1 = Σ||Fo| − |Fc||/Σ|Fo|.
b wR2 = [Σw(Fo2 − Fc2)2/Σw(Fo )]1/2
2
The hydrogen bond interactions in the crystal structures are presented in Fig. 2 and the details are summarized in Table 2. This
conformation of 3a allows the establishment of two intramolecular C–H···F and C–H···N hydrogen bonds, making the seven-membered
and five-membered rings, respectively. However, the crystal structure of 3b exhibit both the intramolecular (C–H···N) and
intermolecular (C–H···F) hydrogen bond interactions. And the molecular skeleton of 3b is linked by the C–H···F intermolecular
hydrogen bonds to form a one-dimensional chain structure.
3a
3b
Fig. 2. Part of the crystal structures of 3a–3b, showing selected non-covalent contacts of the C–H···F and C–H···N types (dashed red lines).
Atoms involved in hydrogen bonds are shown as balls of arbitrary radii. All other atoms and covalent bonds are represented as wires or sticks.
Symmetry codes: (i) –x+1, y, –z+1/2 (3a); (i) x, y–1, z (3b).
Table 2
Hydrogen bonding arrangements for 3a–3b (Å, °).
Complex
D―H···A
C1−H1···N2
C7−H7···F1
C2−H2···F1i
C4−H4···F1i
C15−H15···N2
C31−H31···N1
D―H
0.93
0.93
0.93
0.93
0.93
0.93
H···A
2.60
2.27
2.43
2.40
2.59
2.59
D···A
D―H···A
121
109
145
147
3.179(5)
2.715(5)
3.238(7)
3.222(8)
3.097(7)
3.071(8)
3a
3b
114
113
Symmetry codes: (i) x, y–1, z.
Page 5 of 8

3.2. Electronic absorption spectra
The UV−Vis absorption spectra of 3a and 3b in CH2Cl2 solution at room temperature are presented in Fig. 3, and the data are
provided in Table 3. All these complexes exhibit intense bands at the higher energies (250-350 nm), which are assigned to the spin-
allowed ligand-centered (LC) π-π* transitions. Somewhat weaker bands at lower energies (350-550 nm) are observed, which are
attributed to both spin-allowed (singlet-to-singlet metal-to-ligand charge transfer, 1MLCT) and spin-forbidden (singlet-to-triplet metal-
3
to-ligand charge transfer, MLCT) transitions [31-34]. In comparison with 3a, the lowest lying absorption band for complex 3b is
significantly red-shifted. The findings indicate that the substitution of F by CH3 could lower the HOMO-LUMO gap.
Fig. 3. Electronic absorption spectra of 3a–3b in CH2Cl2 at room temperature.
Table 3
Photophysical properties of complexes 3a/3b.
Absorption wavelength
λabs (nm)
290, 338, 354, 371, 415, 438
Emission
λem (nm)
584
a
Complex
Φem
3a
3b
0.11
297, 342, 357, 377, 430, 459
600
0.074
a fac-Ir(ppy)3 as referenced standard (0.4) [28].
3.3. Emission properties
The normalized emission spectra of 3a−3b in degassed CH2Cl2 solution at room temperature are given in Fig. 4, and the
corresponding data are also listed in Table 3. The two iridium complexes exhibit broad and structureless emission bands centered at
584 and 600 nm, respectively, indicating that they are yellow and orange light-emitting materials. It is interesting to note the
substituent changes in C N ligand of 3b have a marked bathochromic effect on the phosphorescence spectra. It is also evident from
Table S2 (Supporting information) that the substitution of F by CH3 on the C N ligand increases the electron density around the
iridium center (38.83→39.76%) and raises the highest occupied molecular orbital (HOMO) level (-6.083→-5.848 eV), thereby
resulting in a reduced HOMO−LUMO energy gap (3.358→3.177eV).
Fig. 4. Normalized emission spectra of 3a−3b in CH2Cl2 at room temperature.
Phosphorescence relative quantum yields (
room temperature by using typical phosphorescent fac-Ir(ppy)3 as a standard (
Φ
) of 3a−3b in dichloromethane solution were measured to be 0.074−0.11 (Table 3) at
= 0.40) [28]. The comparatively low phosphorescence
Φ
yield observed for CH3-substituted complex 3b may be attributed to the intramolecular electron-transfer quenching of the excited state
by the methyl group [35]. A comparison of the quantum yields observed for these complexes with the previously known related
complex [Ir(C N)2(bipy)]PF6 (C N = 1-(3-fluoro-4-methylphenyl)isoquinoline) (Φ = 0.16) [14] is noteworthy. The results show the
substitution at 3,4-positions is more effective than 2,4-positions.
3.4. Theoretical Calculations
Page 6 of 8

Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations were performed for complexes 3a−3b to
investigate the lowest-energy electronic transition of the ultraviolet absorption spectra. The most representative molecular frontier
orbital diagrams are presented in Fig. 5. The calculated spin-allowed electronic transitions and electron density distributions are
summarized in Tables 4 and S2.
For all of the species investigated, the electron density of the highest occupied molecular orbital (HOMO) is centered on the metal
with a substantial contribution from the cyclometalating ligands, as is also reported for similar iridium cyclometalated complexes
[36,37]. Conversely, the electron density in the lowest unoccupied molecular orbital (LUMO) locates mainly on the ancillary ligands.
The successive unoccupied molecular orbital LUMO+1 primarily originates from the cyclometalating ligands. The theory calculations
of DFT reveal that the lowest-energy electronic transitions (438 nm for 3a, 459 nm for 3b) both arise from HOMO→LUMO+1 orbital
electronic transitions (Table 4). In comparison with 3a (3.583 eV), the reduction of energy gap for 3b (3.463 eV) is consistent with the
red shift observed in absorption spectra.
Fig. 5. The frontier molecular orbital diagrams of complexes 3a−3b from DFT calculations.
Table 4
Main experimental and calculated optical transitions for 3a−3b.
Oscillation
Strength
0.0971
Calcd
(nm)
428
Exptl
(nm)
438
Complex
Orbital excitations
Transition
Character
3a
3b
HOMO → LUMO+1
HOMO → LUMO+1
MLCT/LLCT
MLCT/LLCT
dπIr/πPh-R/quinolinyl → π*
dπIr/πPh-R/quinolinyl → π*
Ph-R/quinolinyl
Ph-R/quinolinyl
0.0979
446
459
4. Conclusion
In conclusion, two new fluorinated phenylisoquinoline-based iridium(III) complexes [Ir(C N)2(bipy)][PF6] (3a−3b) have been
synthesized and thoroughly characterized by studying their crystallographic, spectroscopic and luminescence properties. X-ray
diffraction studies of complexes 3a−3b reveal that they all possess pseudo-octahedral coordination geometry. The theoretical
calculations have also been performed to rationalize the lowest-energy electronic transitions of ultraviolet absorption spectra.
Photoluminescence is observed in the yellow (3a) and orange regions (3b) at room temperature with quantum yield of 0.074-0.11.
Upon a change of substituent on cyclometalated ligand, the absorption and emission spectra exhibit a strong dependence on the
chemical structures of the ligands. The results will facilitate the design of new phenylisoquinoline-based ligands for light-emitting
iridium complexes.
Acknowledgment
This work was supported by the National Natural Science Foundation of China (No. 21501037), the Natural Science Foundation of
Hainan Province (No. 20152017) and the Science and Research Project of Education Department of Hainan Province (Nos. Hjkj2013-
25 and Hnky2015-27).
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