Syntheses and characterizations of 5-nitro-2-(3’,5’-di(trifluoromethyl)phenyl)pyridyl-containing iridium(III) complexes and the two-band white photoluminescence properties in solution

Article abstract of DOI:10.1080/00958972.2016.1230671

A derivative of 2-phenylpyridine (Hppy), 5-nitro-2-(3’,5’-di(trifluoromethyl) phenyl)pyridine (HL), is prepared. The L-containing cyclometalated iridium(III) complexes with mono- and bidentate ancillary ligands, [Ir(L)₂(PPh₃)Cl] (1) and [Ir(L)₂(pic)] (2, pic = picolinic acid), are synthesized and characterized. The photoluminescence (PL) spectra of 1 and 2 in CH₂Cl₂ solutions show emission maxima at 558 and 560 nm, corresponding to yellow light emission with the Commission Internationale de L’eclairage (CIE) coordinates of (0.45, 0.54) and (0.46, 0.52), respectively. However, the luminescence intensity of 2 with PL quantum yield of 0.71 is obviously stronger that of 1 with PLQY of 0.19. The two-band white PL properties of 2 and [Ir(dfppy)2(PPh₃)(NCS)] (3, dfppy = 2-(4,6-difluorophenyl)pyridine) with efficient blue light emission are investigated. The CH₂Cl₂ solutions of 2 and 3 in the molar ratio of 1: 5 show white light emission with the CIE coordinates of (0.33, 0.41).

Full text of DOI:10.1080/00958972.2016.1230671

Journal of Coordination Chemistry
ISSN: 0095-8972 (Print) 1029-0389 (Online) Journal homepage: http://www.tandfonline.com/loi/gcoo20
[Syntheses and characterizations of 5-nitro-2-
(3’,5’-di(trifluoromethyl)-phenyl)pyridyl-containing
iridium(III) complexes and the two-band white
photoluminescence properties in solution
Jia-Xin Xu, Hao Xue, Hao Zou, Si-Wen Ke, Tao Qin, Xin Wang, Xuan Shen &
Dun-Ru Zhu
To cite this article: Jia-Xin Xu, Hao Xue, Hao Zou, Si-Wen Ke, Tao Qin, Xin Wang,
Xuan Shen & Dun-Ru Zhu (2016): [Syntheses and characterizations of 5-nitro-2-(3’,5’-
di(trifluoromethyl)-phenyl)pyridyl-containing iridium(III) complexes and the two-band
white photoluminescence properties in solution, Journal of Coordination Chemistry, DOI:
10.1080/00958972.2016.1230671
To link to this article: http://dx.doi.org/10.1080/00958972.2016.1230671
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Date: 01 September 2016, At: 07:42

Publisher: Taylor & Francis
Journal: Journal of Coordination Chemistry
DOI: http://dx.doi.org/10.1080/00958972.2016.1230671
[Syntheses and characterizations of
5-nitro-2-(3',5'-di(trifluoromethyl)-phenyl)pyridyl-containing
iridium(III) complexes and the two-band white photoluminescence
properties in solution
Jia-Xin Xu, Hao Xue, Hao Zou, Si-Wen Ke, Tao Qin, Xin Wang, Xuan Shen*,
Dun-Ru Zhu*
College of Chemical Engineering, State Key Laboratory of Materials-oriented
Chemical Engineering, Nanjing Tech University, Nanjing 210009, PR China
ABSTRACT
A derivative of 2-phenylpyridine (Hppy), 5-nitro-2-(3',5'-di(trifluoromethyl)phenyl)-
pyridine (HL), is prepared. The L-containing cyclometalated iridium(III) complexes
with mono- and bidentate ancillary ligands, [Ir(L)2(PPh3)Cl] (1) and [Ir(L)2(pic)] (2,
pic = picolinic acid), are synthesized and characterized. The photoluminescence (PL)
spectra of 1 and 2 in CH2Cl2 solutions show emission maxima at 558 and 560 nm,
corresponding to yellow light emission with the CIE coordinates of (0.45, 0.54) and
(0.46, 0.52), respectively. However, the luminescence intensity of 2 with PL quantum
yield (PLQY) of 0.71 is obviously stronger that of 1 with PLQY of 0.19. The
two-band white photoluminescence properties of 2 and [Ir(dfppy)2(PPh3)(NCS)] (3,
dfppy = 2-(4,6-difluorophenyl)pyridine) with efficient blue light emission are
investigated. The CH2Cl2 solutions of 2 and 3 in the molar ratio of 1:5 show white
1

light emission with the CIE coordinates of (0.33, 0.41).
KEYWORDS
5-nitro-2-(3',5'-di(trifluoromethyl)phenyl)pyridine; iridium(III) complex; yellow light
emission; CIE coordinates; two-band white emission
CONTACT
Xuan Shen, E-mail: shenxuan@njtech.edu.cn
Dun-Ru Zhu, E-mail: zhudr@njtech.edu.cn (D.-R. Zhu).
1. Introduction
Organic light-emitting diodes (OLEDs) show tremendous potential in display and
lighting technologies [1–4]. White organic light-emitting diodes (WOLEDs) attract
attentions in lighting source applications because of their outstanding properties, such
as low cost, low heating value, low power consumption, good flexibility, high quality
white light emission, etc. [5, 6]. Three main approaches can be applied to realize
white light emission. i. Color conversion method combines blue-emitting devices with
color conversion layers to design and fabricate WOLEDs [7–9]. ii. Efficient white
polymer light-emitting diodes based on wide band-gap conjugated polymer doped
with red, green, and blue (three primary colors, RGB) emitters on its side or main
chain have the advantages of simple device structure and low-cost manufacturing
compared to WOLEDs based on small molecules [10–12]. iii. Color blending method
is the most widely applied in fabrication of WOLEDs, with RGB or two
complementary color luminescent materials being encapsulated in the multiple
emissive layers in which each layer emits different colors combining into white light
emission [13, 14], or in a single emissive layer emitting white light directly[15, 16].
Though the RGB method can easily reach the standard white light emission due to the
simultaneous existence of the three primary colors, it has some disadvantages such as
complex processing, high operational voltage and undesired spectral variation [17].
2

Thus, two complementary colors method is becoming more and more important for
fabricating WOLEDs because it solves those problems.
Luminescent cyclometalated iridium(III) complexes containing 2-phenylpyridyl
(ppy) or its derivatives have been widely used in the field of OLEDs because of their
outstanding photochemical and photophysical properties [18–20]. Furthermore,
emission wavelengths of ppy-based Ir(III) cyclometalated complexes can be tuned so
as to cover a full range of visible colors by modification of ppy [21–24].
Herein, we present the design, syntheses and characterization of a ppy derivative,
5-nitro-2-(3',5'-di(trifluoromethyl)phenyl)pyridine (HL), and L-containing
cyclometalated Ir(III) complexes with mono- and bidentate ancillary ligands,
[Ir(L)2(PPh3)Cl] (1) and [Ir(L)2(pic)] (2, pic = picolinic acid). The two-band white
photoluminescence properties in solutions of 2 and [Ir(dfppy)2(PPh3)(NCS)] (3,
4,6-dfppy = 2-(4,6-difluorophenyl)pyridyl), another cyclometalated Ir(III) complex
with efficient blue light emission reported in our previous work [25], are also
investigated.
2. Experimental
2.1. Reagents and physical measurements
All reagents were purchased from Aldrich or Alfa Aesar and used as received. All
solvents were distilled from the relevant dehydrants under argon prior to use. All
procedures were carried out in inert gas atmosphere despite the air stability of the
complexes. The reactants of the synthesis of HL, 2-chloro-5-nitropyridine and
3,5-di(trifluoromethyl)phenylboric acid, were prepared according to the available
literature [26] and [27], respectively.
Ultraviolet and visible spectra were recorded on a Perkin Elmer Lambda 35
spectrophotometer at room temperature in dichloromethane solutions at 1.0 × 10–5
mol·L–1. IR spectra (4000–400 cm-1) were recorded on a Thermo Nicolet FT/IR-380
spectrophotometer in KBr pellets at room temperature. Elemental analyses were
3

performed on a Yanaco CHN Corder MT-3. DSC data were obtained using a
Shimadzu DSC–50 differential calorimeter. Electrospray ionization (ESI) mass
spectra were carried out with a Thermo Finnigan LCQADVANTAGE MAX mass
spectrometer. 1H NMR measurements were taken on a Bruker AVANCE–500 in
chloroform-d and chemical shifts were given in ppm relative to tetramethylsilane as
an internal reference standard. Liquid photoluminescence (PL) spectra were obtained
on a Varian Cary Eclipse spectrofluorometer, at the highest spectral resolution, using
an excitation wavelength of 320 nm. Spectra were corrected after measurement using
the emission calibration obtained from measuring a calibrated lamp spectrum.
2.2. Synthesis of HL
2-Chloro-5-nitropyridine (2.5366 g, 16.0 mmol), 3,5-di(trifluoromethyl)phenylboric
acid (4.1269 g, 16.0 mmol), PPh3 (0.5246 g, 2.0 mmol), palladium acetate (0.1123 g,
0.5 mmol) and 50 mL ethylene glycol diethyl ether were added successively into a
200 mL three-necked flask. The mixture was stirred under argon at room temperature
for 20 min. Then after 50 mL aqueous solution of potassium carbonate (2 mol·L–1)
was added, the reaction mixture was further refluxed with stirring for 24 h. After the
reaction mixture was cooled to room temperature, all solids were removed by
filtration and the filtrate was collected for liquid separation. The aqueous phase was
extracted with ethyl acetate (80 mL × 3) and the extract was collected together with
the organic phase of the liquids separation, followed by washing with saturated brine
(80 mL × 3). The solution was further dried over anhydrous magnesium sulfate and
then all solvents were removed by rotary evaporation, leading to the crude product.
The crude product was further purified by passing through a silica gel column using
petroleum ether (b.p. 60–90 ºC)/ethyl acetate (30:1 v/v) as the eluent. The brilliant
yellow crystals of HL which were suitable for X-ray diffraction analysis were
obtained by recrystallization from ethanol in a yield of 3.6900 g (68.6%). Anal.
Calc(%) for HL (C13H6F6N2O2, 336.19): C, 46.44; H, 1.80; N, 8.33. Found(%): C,
4

46.31; H, 1.83; N, 8.39. M.p.: 120–122 ºC (DSC). IR (KBr, ν, cm–1): 3108, 1600,
1579, 1525, 1449, 1355, 1277, 1172, 1137. 1H NMR (CDCl3, 500 MHz) δ (ppm):
9.55 (d, J = 2.45 Hz, 1H), 8.63 (dd, J = 2.55, 2.60 Hz, 1H), 8.58 (s, 2H), 8.04 (s, 1H),
8.02 (s, 1H). ESI-MS: m/z = 336 (M+).
2.3. Synthesis of [Ir(L)2(PPh3)Cl] (1)
IrCl3·H2O (0.9498 g, 3.0 mmol) and HL (3.0257 g, 9.0 mmol) were dissolved in a
mixture of 2-ethoxyethanol (90 mL) and water (30 mL). Then the solution was
refluxed under argon for 24 h. After the solution cooled to room temperature, the
orange-yellow precipitate was collected by filtration and then washed with 95%
ethanol (180 mL) and acetone (180 mL), respectively, giving the crude product
[Ir(L)2Cl]2 in a yield of ca. 2.0475 g (76.0%). As an intermediate, no further
purification of [Ir(L)2Cl]2 was carried out before it was used to synthesize 1 and 2.
PPh3 (0.2098 g, 0.8 mmol) was added into a solution of [Ir(L)2Cl]2 (0.3592 g, 0.2
mmol) in chloroform (80 mL) and then the reaction mixture was refluxed under argon
for 48 h. After cooling to room temperature, the reaction mixture was filtered and the
filtrate was rotary evaporated to remove the solvent, giving the crude product.
Purification of the crude product was realized by passing it through a silica gel
column using petroleum ether (b.p. 60–90 ºC)/ethyl acetate (3:1 v/v) as eluent.
Eventually, orange-yellow microcrystals of 1 were obtained by recrystallization from
the same mixed solvents used in the column chromatography with a yield of 0.3008 g
(64.8%). Anal. Calc(%) for 1 (C44H25ClF12IrN4O4P, 1160.07): C, 45.55; H, 2.17; N,
4.83. Found(%): C, 45.72; H, 2.25; N, 4.67. M.p.: 358–360 ºC (DSC). IR (KBr, ν,
cm–1): 3075, 1618, 1561, 1529, 1487, 1347, 1280, 1181, 1128. 1H NMR (CDCl3, 500
MHz) δ (ppm): 9.93 (d, J = 5.4 Hz, 1H), 8.63 (t, J = 2.8, 2.8 Hz, 2H), 8.05 (t, J = 6.4,
6.4 Hz, 3H), 7.80 (t, J = 3.0, 3.0 Hz, 2H), 7.59 (tt, J = 5.2, 5.2, 5.2, 5.2 Hz, 4H), 7.48
(t, J = 3.9, 3.8 Hz, 3H), 7.37 (m, 6H), 7.25 (d, J = 4.2 Hz, 2H), 7.06 (t, J = 4.8, 4.8 Hz,
2H). ESI-MS: m/z = 1125 ((M – Cl–)+), 863 ((M – Cl– – PPh3)+).
5

2.4. Synthesis of [Ir(L)2(pic)] (2)
By replacing PPh3 with picolinic acid (0.1970 g, 1.6 mmol) and increasing the
quantity of [Ir(L)2Cl]2 (0.7182 g, 0.4 mmol), the reaction was carried out in a similar
synthetic method as for 1. The crude product of the reaction was purified by passing
through a silica gel column using dichloromethane/ethyl acetate (1:1 v/v) as the eluent.
The orange-yellow crystals of 2 containing one molecule of ethyl acetate which were
suitable for X-ray diffraction analyses were acquired by recrystallization from
petroleum ether (b.p. 60–90 ºC)/ethyl acetate (4:1 v/v) in a yield of 0.6007 g (70.0%).
Anal. Calc(%) for 2·CH3COOC2H5 (C36H22F12IrN5O8, 1073.09): C, 40.30; H, 2.07; N,
6.53. Found(%): C, 40.18; H, 2.17; N, 6.46. M.p.: 377–379 ºC (DSC). IR (KBr, ν,
cm–1): 3080, 1670, 1618, 1557, 1529, 1490, 1350, 1283, 1180, 1123. 1H NMR (CDCl3,
500 MHz) δ (ppm): 9.52 (s, 1H), 8.60 (dd, J = 5.8, 5.9 Hz, 2H), 8.25 (m, 4H), 8.18 (d,
J = 3.8 Hz, 2H), 8.07 (t, J = 6.7, 6.4 Hz, 1H), 7.84 (s, 1H), 7.80 (s, 1H), 7.71 (s, 1H),
7.59 (t, J = 3.9, 3.8 Hz, 1H). ESI-MS: m/z = 985 (M+).
2.5. X-ray crystallography
The diffraction data of HL and 2 were collected on a Bruker SMART APEX II CCD
area detector diffractometer equipped with a rotating anode generator using
monochromated Mo Kα radiation (λ = 0.71073 Ǻ) at room temperature. Multi-scan
absorption corrections were applied by using SADABS. The structures were solved
2
by direct methods and refined by full-matrix least-squares based on F using
SHELXTL–97 [28]. All non-disordered non-hydrogen atoms were refined
anisotropically according to the thermal parameters. Atoms of disordered groups were
refined with fixed site occupancy factors (SOF) in isotropic approximation.
Hydrogens were introduced in calculated positions and included in the refinement,
riding on their respective parent atoms. The structural analyses for HL and 2 were
processed smoothly, while a solvent molecule (CH3COOC2H5) was observed in the
6

crystals of 2. Basic information pertaining to crystal parameters and structure
refinement of HL and 2 are summarized in Table 1.
Table 1.
3. Results and discussion
3.1. Syntheses
HL, a ppy derivative in which two trifluoromethyl groups are introduced to the
phenyl and one nitro to the pyridyl of ppy, has been synthesized by the Suzuki
coupling reaction of 2-chloro-5-nitropyridine and 3,5-di(trifluoromethyl)phenylboric
acid. The L-containing cyclometalated Ir(III) dichloro-bridged dimer [Ir(L)2Cl]2,
which is the intermediate for syntheses of 1 and 2, can be prepared by the reaction of
IrCl3·H2O and HL. The reaction of [Ir(L)2Cl]2 with excess PPh3 leads to 1 in which
there are two monodentate ancillary ligands Cl– and PPh3, while excess picolinic acid
results in 2 with one bidentate ancillary ligand (Scheme 1). HL, 1 and 2 have been
characterized by 1H NMR, IR, UV-vis, ESI mass spectrometry, as well as DSC
measurements and elemental analyses. In particular, the assignment of the 1H NMR
spectral signals of 1 and 2 is straightforward by comparison with those of related
cyclometalated Ir(III) complexes containing ppy or its derivatives [29, 30]. Because of
the proton–proton coupling of the phenyl and pyridyl rings in L and ancillary ligands,
the proton peak signals in the 1H NMR spectra of 1 and 2 cannot be attributed
completely. Nevertheless, the total numbers of the protons do agree with the
molecular formulas of 1 and 2.
Scheme 1.
3.2. Crystal structures of HL and 2
Single crystal structures of HL and 2 are represented with ORTEP diagrams in Figure
7

1. Compared with ppy, two electron-withdrawing trifluoromethyl and one nitro
groups have been introduced to the phenyl and pyridyl rings in HL. There are two
similar HL molecules in the asymmetric unit, showing analogous configurations. As
expected, there is considerable disorder of the fluorine atoms of the trifluoromethyl
groups in HL [31]. Twelve fluorines are disordered over two positions, respectively,
three of them with SOF of 0.57:0.43, three of them with SOF of 0.83:0.17, three of
them with SOF of 0.58:0.42 and the rest with SOF of 0.60:0.40. In two molecules, the
phenyl and pyridyl rings are nearly coplanar with the dihedral angles of 6.66 and
2.52°, respectively. Furthermore, two nitro groups are also slightly skewed with
respect to the pyridyl rings with the dihedral angles of 9.17 and 12.00°, respectively.
Two kinds of intermolecular C–H···O hydrogen bonds (∠D–H···A = 163, 177° and
d(H···A) = 2.48, 2.57 Å) stabilize the molecular conformation. Two kinds of
face-to-face type π–π stacking interactions involving overlapping phenyl and pyridyl
rings with centroid-to-centroid distances of 3.833 and 3.850 Å pack the molecules in
layered arrays.
2 crystallizes in the triclinic space group P1¯ together with an ethyl acetate
molecule, adopting a distorted octahedral coordination geometry around Ir(III)
consisting of two N,C-bidentate L ligands and one N,O-bidentate pic ligand.
Compared with free HL, six fluorines in 2 are also disordered over two positions,
respectively, three of them with SOF of 0.82:0.18, the other three with SOF of
0.57:0.43. The structure prefers the trans-NL–NL and cis-NL–Npic chelate disposition,
corresponding to a meridional (mer) configuration with respect to N atoms [32],
similar to those reported for cyclometalated Ir (III) complexes, [Ir(5-NO2-ppy)2(pic)]
(5-NO2-ppy = 2-phenyl-5-nitropyridyl) [33] and [Ir(dfNppy)2(pic)] (dfNppy =
2-(2’,4’-difluorophenyl)-5-nitropyridyl) [34] containing other ppy derivatives and the
same pic ancillary ligand. Similar to the free HL in the solid state, the phenyl and
pyridyl rings in 2 are also nearly coplanar with dihedral angles of 7.64 and 3.45°,
respectively. Furthermore, the Ir–C, Ir–N and Ir–O bond lengths and angles of 2 are
8

also similar to those of [Ir(5-NO2-ppy)2(pic)] and [Ir(dfNppy)2(pic)], suggesting that
modification of ppy will not change the structures of the corresponding ppy- or its
derivatives-containing Ir(III) complexes greatly, while keeping the stability of the
complexes, which is one of the key factors in applications of Ir(III) complexes as
OLEDs materials.
Figure 1.
3.3. Photophysical properties of 1 and 2
The UV-vis absorption and the liquid photoluminescence (PL) spectra of 1 and 2 in
dichloromethane solutions of 3 × 10–5 mol·L–1 at room temperature are shown in
Figure 2 and the spectroscopic data are summarized in Table 2.
Figure 2.
Table 2.
The electronic energy gap between the highest occupied molecular orbital
(HOMO) and the lowest unoccupied molecular orbital (LUMO) of the ppy-containing
cyclometalated Ir(III) complexes can be adjusted by modifying the ppy fragment to
achieve the emission wavelengths over the entire visible region. Compared with the
analogues of 1 and 2, same mono- and bidentate ancillary ligands-containing Ir(III)
complexes [Ir(5-NO2-ppy)2(PPh3)Cl] and [Ir(5-NO2-ppy)2(pic)] [32],
[Ir(dfNppy)2(PPh3)Cl] and [Ir(dfNppy)2(pic)] [33] in which different modified groups
are introduced to the ppy fragments, the UV-vis absorption spectra of 1 and 2 show
obvious blue-shifts. Not only the spin-allowed intraligand (1IL) π–π* charge transfer
absorption bands, but also the spin-allowed singlet ligand-centered (1LC),
metal-to-ligand charge transfer (1MLCT), and the spin-forbidden triplet
9

ligand-centered (3LC), metal-to-ligand charge transfer (3MLCT) absorptions bands
shift about 50–100 nm to high energy, suggesting that the HOMO–LUMO energy
gaps (Eg) of 1 and 2 should be greater than those of their analogues,
[Ir(5-NO2-ppy)2(PPh3)Cl] and [Ir(5-NO2-ppy)2(pic)], [Ir(dfNppy)2(PPh3)Cl] and
[Ir(dfNppy)2(pic)] [35]. This result is further shown by the liquid PL spectra 1 and 2,
exhibiting emission peaks with wavelengths of 558 and 560 nm, corresponding to
yellow light-emitting. However, the solutions of [Ir(5-NO2-ppy)2(PPh3)Cl],
[Ir(5-NO2-ppy)2(pic)], [Ir(dfNppy)2(PPh3)Cl] and [Ir(dfNppy)2(pic)] mostly show red
or red-orange luminescence. Moreover, the PL quantum yields (PLQYs) of 1 and 2 in
solutions are measured by a relative method using 0.2 μg/mL quinine sulfate solution
in 0.5 N sulfuric acid as a standard [36] with the values of 0.19 and 0.71, respectively.
Furthermore, the Commission Internationale de L’éclairage (CIE) coordinates of 1
and 2 are determined as (0.45, 0.54) and (0.46, 0.52), respectively, being close to that
of the saturated yellow light, (0.50, 0.50).
3.4. Two-band white photoluminescence properties of 2 and 3 in solution
In previous works, another cyclometalated Ir(III) complex with the ppy derivative
2-(4,6-difluorophenyl)pyridyl as the main ligand and PPh3, NCS– as the ancillary
ligands, [Ir(dfppy)2(PPh3)(NCS)] (3), has been reported as an efficient blue
phosphorescent emitter with the PLQY of 0.39 [25]. The PL spectra of 3 in CH2Cl2
solution show emission maxima at 456 nm with the CIE coordinates of (0.14, 0.24).
The yellow light emission of 2 and blue light emission of 3 can be approximately
considered as two complementary colors. In addition, the connecting line of the CIE
coordinates of 2 and 3, (0.46, 0.52) and (0.14, 0.42), passes through the white light
region of chromaticity coordinate. Thus, two-band white light-emitting properties of 2
and 3 in solution are investigated. First, the PL spectra of 2 and 3 are independently
measured in CH2Cl2 solutions of 3 × 10–5 mol·L–1 at room temperature. Then, the PL
spectra measurement of the mixture of 2 and 3 in the mole ratio of 1:1 in CH2Cl2
10

solution with total concentration of 3 × 10–5 mol·L–1 at room temperature is also
carried out. As shown in Figure 3, the emission maxima of 2 and 3 do not change with
the values of 560 and 456 nm, respectively. The spectra of the mixture show
independent emission peaks of 2 and 3, exhibiting weaker luminescent intensity
caused by the reduction of concentrations. The three curves pass through the same
point. Thus, it can be concluded that luminescence of 2 and 3 do not interfere with
each other in solution.
Figure 3.
On this basis, the PL spectra of a serious of CH2Cl2 solutions containing 2 and 3
in different mole ratios with constant total concentration of 3 × 10–5 mol·L–1 are
measured. As shown in Figure 4 (left), with the increase of the mole ratio of 3, the
short wavelength region of the spectra corresponding to light emission of 3 gradually
increases, accompanied by decrease of the long wavelength region of the spectra
corresponding to the light emission of 2. As expected, all curves pass through the
same point. The CIE coordinates of all combinations are estimated from the PL
spectra and are also shown in Figure 4 (right), exhibiting good colinearity. The CIE
coordinates of the mixture of 2 and 3 with the mole ratio of 1:5 are (0.33, 0.41), being
close to those of pure white light (0.33, 0.33).
Figure 4.
4. Conclusion
A new derivative of Hppy, 5-nitro-2-(3',5'-di(trifluoromethyl)phenyl)- pyridine (HL)
has been synthesized. The L-containing Ir(III) complexes with mono- and bidentate
ancillary ligands, 1 and 2 were synthesized and characterized. The PL spectra of 1 and
2 in CH2Cl2 solutions show emission maxima at 558 and 560 nm, corresponding to
11

yellow light emission with the CIE coordinates of (0.45, 0.54) and (0.46, 0.52),
respectively. However, the luminescent intensity of 2 with PLQY of 0.71 is stronger
that of 1 with PLQY of 0.19. The two-band white photoluminescence properties with
the complementary color emitting of 2 and 3, a blue light emitter, are investigated.
The CH2Cl2 solution of 2 and 3 in the molar ratio of 1:5 shows the best white light
emission with CIE coordinates of (0.33, 0.41), suggesting the potential applications of
2 and 3 as WOLED materials.
Supplementary material
Crystallographic data for the structure reported in this article have been deposited
with the Cambridge Crystallographic Data Center as supplementary publication Nos.
CCDC 1478519 (HL) and 1477140 (2·CH3COOC2H5). Copies of the data can be
obtained free of charge via www.ccdc.cam.ac.uk (or from the Cambridge
Crystallographic Centre, 12 Union Road, Cambridge CB21EZ, UK; Fax: +44 1223
336033; e-mail: deposit@ccdc.cam.ac.uk).
Acknowledgements
We are grateful to the National Natural Science Foundation of China (Grant No.
21476115) and Top-notch Academic Programs Project of Jiangsu Higher Education
Institutions (Grant No. PPZY2015A044) for financial support.
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Scheme and Figures captions:
14

Scheme 1. Synthetic routes of HL, 1 and 2.
Figure 1. ORTEP diagrams of HL and 2. The hydrogens and solvent molecules are
omitted for clarity. Selected bond distances (Å) and angles (°) for HL: C5–C6
1.487(3), C2–N2 1.466(3), N2–O1 1.195(3), N2–O2 1.203(3), C8–C12 1.490(4),
C10–C13 1.495(4); N1–C5–C6 115.96(17), C4–C5–C6 122.66(18), C7–C6–C5
120.34(18), C11–C6–C5 121.68(18); for 2: Ir1–N1 2.033(4), Ir1–N3 2.003(4), Ir1–N5
2.141(4), Ir1–O6 2.125(4), Ir1–C11 2.049(5), Ir1–C24 2.022(5); N1–Ir1–N3
172.59(17), O6–Ir1–C24 169.49(16), N5–Ir1–C11 166.83(18).
Figure 2. UV-vis absorption and liquid PL spectra (λex = 320 nm) of 1 and 2 in
CH2Cl2 solutions (3 × 10–5 mol·L–1) at room temperature. The luminescent intensity
of PL spectra is normalized.
Figure 3. PL spectra of 2, 3 and the mixture of 2 and 3 in the mole ratio of 1:1 in
CH2Cl2 solutions with constant concentration of 3 × 10–5 mol·L–1 at room temperature.
The luminescent intensity is expressed as the relative strength.
Figure 4. PL spectra of the mixture of 2 and 3 in different mole ratios in CH2Cl2
solutions with the constant total concentration of 3 × 10–5 mol·L–1 at room
temperature (left) and corresponding CIF coordinates (right) with the data of (0.46,
0.52) (2), (0.43, 0.49) (2:3 = 1:1), (0.40, 0.46) (2:3 = 1:2), (0.36, 0.43) (2:3 = 1:3),
(0.33, 0.41) (2:3 = 1:5), (0.30, 0.37) (2:3 = 1:6), (0.25, 0.33) (2:3 = 1:9), (0.27, 0.35)
(2:3 = 1:10), (0.14, 0.24) (3).
15

Table 1. Crystal date for HL and 2.
HL
C13H6F6N2O2
336.20
2·CH3COOC2H5
C32H14F12IrN5O6·C4H8O2
1072.79
293(2)
0.71073
Empirical formula
Formula weight
Temperature (K)
Radiated used (λ[Å])
Crystal size (mm3)
Crystal system
Space group
a (Å)
296(2)
0.71073
0.16 × 0.14 × 0.12
monoclinic
P21/c
0.18 × 0.14 × 0.12
triclinic
P1¯
8.105(4)
19.783(10)
17.307(9)
90.00
91.125(7)
90.00
2774(3)
8
1.610
0.163
1344
1.56–25.00
19402
9.513(3)
b (Å)
12.670(4)
16.605(5)
92.952(4)
103.745(4)
97.417(4)
1920.8(10)
2
1.855
3.593
1044
1.27–25.00
13628
c (Å)
α (º)
β (º)
γ (º)
V (Å3)
Z
ρ
calc. (g cm-3)
μ (mm-1)
F(000)
Scan range θ (º)
Number of total
reflections
Number of unique
reflections (Rint)
Number of data/
restraints/parameters
Goodness-of-fit on F
R1, ωR2 [I > 2σ(I)]
R1, ωR2 (all data)
(Δ/σ)max
4867 (0.0325)
4867/111/527
6690 (0.0577)
6690/106/615
2
1.092
0.963
0.0653, 0.1976
0.1086, 0.2278
0.005
0.0536, 0.1209
0.0835, 0.1325
0.008
Δρmax, Δρmin (e Ǻ-3)
0.274, –0.319
1.178, –1.121
16

Table 2. Photophysical properties of 1 and 2.
Absorption
Complex
PL
λ (nm) (ε, 103 L·mol–1·cm–1)
λmax (nm) PLQYs CIE
271 (40.3), 319sh (12.4), 404 (3.3)
285 (41.9), 312sh (36.1), 451 (5.9)
558
560
0.19
0.71
(0.45, 0.54)
(0.46, 0.52)
1
2
17

Scheme 1
18

19

20

21

22

23