Ligand effects on luminescence of new type blue light-emitting mono(2-phenylpyridinato)iridium(III) complexes

Article abstract of DOI:10.1021/ic800376e

Newly prepared hydrido iridium(III) complexes [Ir(ppy)(PPh ₃)₂(H)L]^0,+ (ppy = bidentate 2-phenylpyridinato anionic ligand; L = MeCN (1b), CO (1c), CN^- (1d); H being trans to the nitrogen of ppy ligand) emit blue light at the emission λ _max (452-457, 483-487 nm) significantly shorter than those (468, 495 nm) of the chloro complex Ir(ppy)(PPh₃)₂(H)(Cl) (1a). Replacing ppy of 1a-d with F₂ppy (2,4-difluoro-2-phenylpyridinato anion) and F₂Meppy (2,4-difluoro-2-phenyl-m-methylpyridinato anion) brings further blue-shifts down to the emission λ_max at 439-441 and 465-467 nm with CIE color coordinates being x = 0.16 and y = 0.18-0.20 to display a deep-blue photoemission. No significant blue shift is observed by replacing PPh₃ of 1a with PPh₂Me to produce Ir(ppy)(PPh₂Me)₂(H)(Cl) (1aPPh₂Me), which displays emission λ_max at 467 and 494 nm. The chloro complexes, [Ir(ppy)(PPh₃)₂(Cl)(L)]^0,+ (L = MeCN (2b), CO (2c), CN^- (2d)) having a chlorine ligand trans to the nitrogen of ppy also emit deep-blue light at emission λ_max 452-457 and 482-487 nm.

Full text of DOI:10.1021/ic800376e

Inorg. Chem. 2008, 47, 6289-6295
Ligand Effects on Luminescence of New Type Blue Light-Emitting
Mono(2-phenylpyridinato)iridium(III) Complexes
Min-Sik Eum,† Chong Shik Chin,*,† Song yi Kim,† Choongil Kim,† Sung Kwon Kang,‡ Nam Hwi Hur,†
Ji Hoon Seo,§ Gu Young Kim,§ and Young Kwan Kim§
Chemistry Department, Sogang UniVersity, Seoul 121-742, Korea, Chemistry Department,
Chungnam National UniVersity, Daegeon 305-764, Korea, and Department of Information
Display, Hongik UniVersity, Seoul 121-791, Korea
Received February 27, 2008
Newly prepared hydrido iridium(III) complexes [Ir(ppy)(PPh3)2(H)L]0,+ (ppy ) bidentate 2-phenylpyridinato anionic
ligand; L ) MeCN (1b), CO (1c), CN- (1d); H being trans to the nitrogen of ppy ligand) emit blue light at the
emission λmax (452-457, 483-487 nm) significantly shorter than those (468, 495 nm) of the chloro complex
Ir(ppy)(PPh3)2(H)(Cl) (1a). Replacing ppy of 1a-d with F2ppy (2,4-difluoro-2-phenylpyridinato anion) and F2Meppy
(2,4-difluoro-2-phenyl-m-methylpyridinato anion) brings further blue-shifts down to the emission λmax at 439-441
and 465-467 nm with CIE color coordinates being x ) 0.16 and y ) 0.18-0.20 to display a deep-blue
photoemission. No significant blue shift is observed by replacing PPh3 of 1a with PPh2Me to produce
Ir(ppy)(PPh2Me)2(H)(Cl) (1aPPh2Me), which displays emission λmax at 467 and 494 nm. The chloro complexes,
[Ir(ppy)(PPh3)2(Cl)(L)]0,+ (L ) MeCN (2b), CO (2c), CN- (2d)) having a chlorine ligand trans to the nitrogen of ppy
also emit deep-blue light at emission λmax 452-457 and 482-487 nm.
Introduction
complexes (fac-Ir(ppy)3 and mer-Ir(ppy)3) and bis(ppy)
complexes, cis-Ir(ppy)2LL′3 and trans-Ir(ppy)2LL′4 with the
two ppy ligands cis and trans to each other, respectively.
In the course of searching new blue-light emitting materi-
als, we recently began our investigation into another type of
complexes containing only one ppy ligand, Ir(ppy)(PR3)2LL′
with the two phosphines trans to each other and two cis-
ancillary ligands L and L′ because there are three different
types of ligands ppy, axial ligand PR3, and ancillary ligands
L and L′ that could be modified to control the luminescence
characteristics of the complexes. We now wish to report a
new type of photoluminescent monoppy Ir(III) complexes
[Ir(C∧N)(PR3)2LL′]0,+ (C∧N ) ppy, F2ppy, F2Meppy; PR3
) PPh3, PPh2Me) emitting deep- and sky-blue light when L
and L′ are strong field ligands such as H-, CO, and CN-
and medium-field ligand MeCN.
Iridium(III) complexes containing 2-phenylpyridinato ligand
(ppy, bidentate anionic ligand) have been intensively and
extensively studied because they are efficient phosphorescent
materials emitting lights in the region of red, green, and blue,
which are tuned by modification of ppy as well as by
introducing diverse ancillary ligands.1 There are three
different types of ppy-iridium complexes investigated for
their photo- and electrical-luminescent properties: tris(ppy)2
* To whom correspondence should be addressed. E-mail: cschin@
sogang.ac.kr. Phone: +82-16-230-7239. Fax: +82-2-701-0967.
†
Sogang University.
Chungnam National University.
Hongik University.
‡
§
(1) (a) Holder, E.; Langeveld, B. M. W.; Schubert, U. S. AdV. Mater.
2005, 17, 1109–1121. (b) Baldo, M. A.; Thompson, M. E.; Forrest,
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10.1021/ic800376e CCC: $40.75  2008 American Chemical Society
Inorganic Chemistry, Vol. 47, No. 14, 2008 6289
Published on Web 06/07/2008

Eum et al.
were obtained by a combination of the direct methods and difference
Fourier syntheses and refined by full matrix least-squares on F2
using SHELXTL.12 All non-hydrogen atoms were refined anisotro-
pically. Hydrogen atoms were added in calculated positions. Details
of crystallographic data collection for 1aPPh2Me and 2b are listed
in Table 1.
Synthesis. Schlenk-type glass wares were used in most of
experiments for synthesis and measurements although newly
prepared complexes are stable in solution to be handled in air.
2-Phenylpyridine (ppyH), PPh3, PPh2Me, pyridine, MeCN, AgOTf,
tetrabutylammonium cyanide, Pd(PPh3)4, 2-bromopyridine, 2,4-
difluorophenylyboronic acid, and 2-bromo-4-methylpyridine were
purchased from Aldrich. F2ppyH and F2MeppyH were synthesized
by Suzuki coupling reactions.13 IrCl3 ·xH2O and CO were obtained
from Pressure Chemicals and Dong-A Gas Co., Korea, respectively.
Iridium complexes, [Ir(ppy)(H)(NCMe)(PPh3)2]+ (1b)14 and [Ir-
(COD)Cl]215 were synthesized by the literature methods. 1a, 1aF2,
1aF2Me, and 1aPPh2Me have been prepared practically by the same
method described below for 1a.
Figure 1. Chemical Structures of [Ir(C^N)(L)(H)(PR3)2]0,+ (1) and [Ir(p-
py)(L)(Cl)(PPh3)2]0,+ (2).
No luminescent property has been reported for monoppy
iridium(III) complexes, Ir(ppy)(PR3)2LL′, whereas synthesis
of [Ir(ppy)(PPh3)2(H)(CO)]+ and analogues were previously
reported5 with no luminescence data. Isoelectronic os-
mium(II) analogues were reported with photophysical prop-
erties.6 We recently reported that stronger field ancillary
ligands L and L′ cause a significant blue shift of the emission
λmax for bis(ppy) complexes Ir(ppy)2LL′.7
To establish the effects of trans ligands to ppy on the
luminescent property, two different series of complexes, 1
and 2, have been synthesized in this study (below Figure 1).
The two ligands, chlorine and hydrogen, have been chosen
in this study since (i) both H- and Cl- are anionic ligands
and (ii) hydride (H-) is a strong field ligand whereas chloride
(Cl-) is weak one.
Synthesis of Ir(ppy)(H)(Cl)(PPh3)2 (1a). A reaction mixture
of [Ir(COD)Cl]2 (0.1 g, 0.14 mmol), PPh3 (0.15 g, 0.56 mmol),
and ppyH (43 mg, 0.28 mmol) in 2-ethoxyethanol (10 mL) was
refluxed under N2 (1 atm) for six hours. After cooling down to 25
°C, the yellow precipitate was filtered off and washed with methanol
(3 × 10 mL), recrystallized in CHCl3/n-pentane, and dried under
1
vacuum. The yield was 0.23 g and 93% based on 1a. H NMR
(300 MHz; CDCl3): δ 8.93 (d, J ) 5.4 Hz, 1H), 7.38-7.32 (m,
15H), 7.16 (t, J ) 7.2 Hz, 6H), 7.11-7.06 (m, 13H), 6.63-6.55
(m, 1H), 6.36 (d, J ) 7.8 Hz, 2H), 5.96 (t, J ) 7.2 Hz, 1H), -16.72
(t, J ) 16.8 Hz, 1H). 13C NMR (75.5 MHz, CDCl3): δ 165.51,
149.75, 148.04, 143.61, 142.44, 135.42, 134.18, 131.92, 130.17,
129.02, 127.34, 122.49, 120.57, 119.35, 117.30. 31P NMR (81 MHz,
CDCl3): δ 10.56. (s). IR (KBr, cm-1): 2130 (m, νIr-H). Anal. Calcd
for IrC47NH39ClP2: C, 62.21; H, 4.33; N, 1.54. Found: C, 62.18;
H, 4.39; N, 1.53.
Ir(F2ppy)(H)(Cl)(PPh3)2 (1aF2). 1H NMR (300 MHz; CDCl3):
δ 9.00 (d, J ) 5.1 Hz, 1H), 7.82 (d, J ) 8.7 Hz, 1H), 7.41-7.35
(m, 13H), 7.21 (t, J ) 6.9 Hz, 6H), 7.16-7.10 (m, 12H), 6.68 (t,
J ) 5.7 Hz, 1H), 6.04-5.97 (m, 1H), 5.76 (d, J ) 9.0 Hz, 1H),
-16.76 (t, J ) 16.5 Hz, 1H). 13C NMR (75.5 MHz, CDCl3): δ
162.82, 150.06, 146.82, 141.81, 136.20, 134.12, 131.78, 131.42,
131.07, 129.40, 127.50, 94.65. 19F NMR (188.2 MHz, CDCl3): δ
-110.42 (q, J ) 9.2 Hz, 1F), -112.75 (t, J ) 6.7 Hz, 1F). 31P
NMR (81 MHz, CDCl3): δ 9.02 (s). IR (KBr, cm-1): 2155 (m,
Experimental Section
1H, 13C, 19F, and 31P NMR spectra were recorded on a Varian
200 or 300 MHz spectrometer. Nicolet 205 instrument was used
to measure infrared spectra. Absorption spectra measured on an
Agilent 8453 UV-vis spectrophotometer. Steady-state emission
spectra were measured on a JY Horiba Fluorolog-3 spectrofluo-
rimeter. Quantum efficiency was calculated using fac-Ir(ppy)3 as
the reference in toluene (ΦPL ) 0.40).8 Elemental analysis was
carried out using a Carlo Erba EA1180 at the Organic Chemistry
Research Center, Sogang University. Color coordinates of lumi-
nescence were measured with a Minolta CS-200 chromameter.
X-ray Crystallography. X-ray intensity data were obtained using
a Bruker SMART APEX-II CCD diffractometer equipped with
graphite-monochromated Mo KR radiation (λ ) 0.71073 Å) at 173
and 295 K for 1aPPh2Me and 2b, respectively. Initial unit-cell
parameters were obtained from SMART software.9 Data integration,
correction for Lorentz and polarization effects, and final cell
refinement were performed by SAINTPLUS.10 An empirical absorp-
tion correction based on the multiple measurement of equivalent
reflections was applied using the program SADABS.11 Structures
νIr-H). Anal. Calcd for IrC47NH37F2ClP2: C, 59.84; H, 3.95; N, 1.48.
Found: C, 59.80; H, 3.92; N, 1.50.
1
Ir(F2Meppy)(H)(Cl)(PPh3)2 (1aF2Me). H NMR (300 MHz;
CDCl3): δ 8.85 (d, J ) 5.4 Hz, 1H), 7.67 (s, 1H), 7.43-7.37 (m,
12H), 7.22 (t, J ) 7.2 Hz, 6H), 7.16-7.11 (m, 12H), 6.55 (d, J )
5.4 Hz, 1H), 6.04-5.96 (m, 1H), 5.77(d, J ) 9.3 Hz, 1H), 2.32 (s,
3H), -16.79 (t, J ) 16.5 Hz, 1H). 13C NMR (75.5 MHz, CDCl3):
δ 161.89, 154.93, 149.36, 147.63, 149.36, 147.63, 134.13, 131.55,
129.32, 127.43, 125.33, 122.62, 121.87, 95.22, 21.32. 19F NMR
(188.2 MHz, CDCl3): δ -110.90 (q, J ) 10.0 Hz, 1F), -112.89
(t, J ) 11.5 Hz, 1F). 31P NMR (81 MHz, CDCl3): δ 8.87 (s). IR
(KBr, cm-1): 2127 (m, νIr-H). Anal. Calcd for IrC48NH39F2ClP2:
C, 60.21; H, 4.11; N, 1.46. Found: C, 60.25; H, 4.16; N, 1.47.
(5) (a) Neve, F.; Ghedini, M.; De Munno, G.; Crispini, A. Organometallics
1991, 10, 1143–1148. (b) Crabtree, R. H.; Lavin, M.; Bonneviot, L.
J. Am. Chem. Soc. 1986, 108, 4032–4037. (c) Albe´niz, A. C.; Schulte,
G.; Crabtree, R. H. Organometallics 1992, 11, 242–249.
(6) (a) Hsu, F.-C.; Tung, Y.-L.; Chi, Y.; Hsu, C.-C.; Cheng, Y.-M.; Ho,
M.-L.; Chou, P.-T.; Peng, S.-M. Inorg. Chem. 2006, 45, 10188–10196.
(b) Chi, Y.; Chou, P.-T. Chem. Soc. ReV. 2007, 36, 1421–1431.
(7) Chin, C. S.; Eum, M.-S.; Kim, S. y.; Kim, C.; Kang, S. K. Eur. J. Inorg.
Chem. 2007, 372–375.
(8) King, K. A.; Spellane, P. J.; Watts, R. J. J. Am. Chem. Soc. 1985,
107, 1431.
(9) SMART, V 5.05 Software for the CCD Detector System; Bruker
Analytical X-ray Systems, Inc.: Madison, WI, 1998.
(12) Sheldrick, G. M. SHELXTL, V 6.1; Bruker Analytical X-ray Systems,
Inc.: Madison, WI, 1997.
(10) SAINTPLUS, V 5.00 Software for the CCD Detector System; Bruker
Analytical X-ray Systems, Inc.: Madison, WI, 1998.
(13) Lohse, O.; Thevenin, P.; Waldvogel, E. Synlett 1999, 1, 45.
(14) Chin, C. S.; Eum, M.-S.; Kim, S. y.; Kim, C.; Kang, S. K. Eur. J. Inorg.
Chem. 2006, 4979.
(11) SADABS, Program for absorption correction using SMART CCD based
on the method of Blessing, R. H. Acta Crystallogr. 1995, A51, 33.
(15) Herde, J. L.; Lambert, J. C.; Senoff, C. V. Inorg. Synth. 1974, 15, 18.
6290 Inorganic Chemistry, Vol. 47, No. 14, 2008

Mono(2-phenylpyridinato)iridium(III) Complexes
Table 1. Details of Crystallographic Data Collection for 1aPPh2Me and 2b
a
1aPPh2Me·CHCl3
2b·CHCl3
chemical formula
chemical fw
T, K
IrC38H36Cl4NP2
902.62
173(2)
IrC51H42Cl4F3N2O3P2S
1215.87
295(2)
cryst dimensions, mm3
cryst syst
space group
color of crystal
a, Å
0.10 × 0.08 × 0.07
monoclinic
P2(1)/n
pale yellow
13.4805(2)
18.7541(3)
14.7961(2)
90
103.0790(10)
90
3643.63(9)
4
0.08 × 0.05 × 0.04
monoclinic
P2(1)/c
pale yellow
10.4325(8)
22.5809(16)
21.5244(16)
90
91.132(2)
90
5069.6(6)
4
b, Å
c, Å
R, deg
ꢀ, deg
γ, deg
V, Å3
Z
F
calcd, g·cm-1
1.645
4.074
1784
1.593
3.004
2416
µ, mm-1
F(000)
θ range, deg
1.78 to 28.29
-17 e h e 17
-22 e k e 25
-16 e l e 19
38 680
1.31 to 26.00
-12 e h e 12
-27 e k e 27
-26 e l e 26
64 298
hkl range
no. of reflns
no. of unique data
completeness to theta
no. of data/restraints/params
refinements method
R1
9028
9955
99.8% at 28.29 deg
9028/0/419
99.9% at 26.00 deg
9955/0/590
full-matrix least-squares on F2
0.0527
0.1242
1.033
full-matrix least-squares on F2
0.0278
0.0513
1.016
wR2
GOF
a R1 ) [∑|Fo| - |Fc|/|Fo|], wR2 ) [∑w(Fo - Fc )2/∑w(Fo )2]0.5; w ) 1/[σ2(Fo ) + (0.0388P)2 + 1.8667P], where P ) (Fo + 2Fc )/3.
2
2
2
2
2
2
1
Ir(ppy)(H)(Cl)(PPh2Me)2 (1aPPh2Me). H NMR (300 MHz;
CDCl3): δ 8.59 (d, J ) 5.4 Hz, 1H), 7.43-7.32 (m, 6H), 7.27-7.04
(m, 18H), 6.75 (d, J ) 7.4 Hz, 1H), 6.61-6.50 (m, 2H), 1.60 (t, J
) 3.8 Hz, 6H), -16.74 (t, J ) 15.6 Hz, 1H). 31P NMR (81 MHz,
CDCl3): δ -3.29. (s). IR (KBr, cm-1): 2156 (m, νIr-H). Anal. Calcd
for IrC37NH35ClP2: C, 56.73; H, 4.50; N, 1.79. Found: C, 56.71;
H, 4.53; N, 1.79.
IrC49NH37F5O4SP2: C, 54.24; H, 3.44; N, 1.29. Found: C, 54.29;
H, 3.49; N, 1.30.
[Ir(F2Meppy)(H)(CO)(PPh3)2](OTf) (1cF2Me). 1H NMR (300
MHz; CD2Cl2): δ 8.89 (d, J ) 5.7 Hz, 1H), 7.44 (t, J ) 7.2 Hz,
6H), 7.33 (t, J ) 7.5 Hz, 12H), 7.24-7.18 (m, 13H), 7.10 (d, J )
5.7 Hz, 1H), 6.56 (d, J ) 8.1 Hz, 1H), 6.41 (t, J ) 10.2 Hz, 1H),
2.32 (s, 3H), -15.46 (t, J ) 12.3 Hz, 1H). 13C NMR (75.5 MHz,
CD2Cl2): δ 173.88, 160.50, 153.34, 151.62, 133.75, 131.91, 128.99,
127.53, 125.82, 125.38, 124.89, 100.62, 21.37. 19F NMR (188.2
MHz, CD2Cl2): δ -107.41 (t, J ) 10.7 Hz, 1F), -108.29 (q, J )
9.0 Hz, 1F). 31P NMR (81 MHz, CD2Cl2): δ 6.12. (s). IR (KBr,
cm-1): 2184 (m, νIr-H), 2052 (s, νC′O), 1261, 1151 and 1031 (s,
OTf-). Anal. Calcd for IrC50NH39F5O4SP2: C, 54.64; H, 3.58; N,
1.27. Found: C, 54.68; H, 3.60; N, 1.24.
1c, 1cF2, and 1cF2Me have been prepared practically by the same
method described below for 1c.
Synthesis of [Ir(ppy)(H)(CO)(PPh3)2](OTf) (1c). A 0.1 g (0.09
mmol) of 1b in CH2Cl2 (10 mL) was stirred under CO (1 atm) at
25 °C for 12 h before n-pentane (30 mL) was added to precipitate
white microcrystals, which were isolated by filtration, washed with
n-pentane (3 × 10 mL), and dried under vacuum. The yield was
1
90 mg and 92% based on 1c. H NMR (300 MHz; CD2Cl2): δ
1d, 1dF2, and 1dF2Me have been prepared practically by the
same method described below for 1d.
8.89 (d, J ) 5.4 Hz, 1H), 7.57 (t, J ) 7.8 Hz, 1H), 7.38-7.02 (m,
35H), 6.65 (t, J ) 6.6 Hz, 1H), -15.38 (t, J ) 12.3 Hz, 1H). 13C
NMR (75.5 MHz, CD2Cl2): δ 173.99, 169.98, 163.98, 153.46,
152.84, 147.10, 142.86, 138.45, 133.50, 131.33, 130.05, 128.60,
127.74, 125.91, 124.85, 122.83, 120.67, 118.56. 31P NMR (81 MHz,
CDCl3): δ 6.15. (s). IR (KBr, cm-1): 2195 (m, νIr-H), 2042 (s, νC′O),
1270, 1153 and 1031 (s, OTf-). Anal. Calcd for IrC49NH39F3O4SP2:
C, 56.10; H, 3.75; N, 1.34. Found: C, 56.16; H, 3.78; N, 1.32.
[Ir(F2ppy)(H)(CO)(PPh3)2](OTf) (1cF2). 1H NMR (300 MHz;
CD2Cl2): δ 9.04 (d, J ) 5.4 Hz, 1H), 7.56 (t, J ) 7.8 Hz, 1H),
7.42 (t, J ) 6.9 Hz, 6H), 7.34-7.29 (m, 12H), 7.24-7.15 (m, 14H),
6.53 (t, J ) 8.1 Hz, 1H), 6.43-6.37 (m, 1H), -15.50 (t, J ) 12.0
Hz, 1H). 13C NMR (75.5 MHz, CDCl3): δ 173.92, 161.06, 154.17,
139.20, 133.71, 132.01, 129.07, 127.41, 124.95, 124.86, 124.78,
124.45, 100.71. 19F NMR (188.2 MHz, CD2Cl2): δ -107.31 (t, J
) 11.5 Hz, 1F), -107.82 (q, J ) 9.2 Hz, 1F). 31P NMR (81 MHz,
CD2Cl2): δ 6.17. (s). IR (KBr, cm-1): 2194 (m, νIr-H), 2052 (s,
Synthesis of Ir(ppy)(H)(CN)(PPh3)2 (1d). A reaction mixture
of [Ir(ppy)(H)(NCMe)(PPh3)2](OTf) (1b, 0.10 g, 0.09 mmol) and
tetrabutylammonium cyanide (27 mg, 0.10 mmol) in CH2Cl2 (10
mL) was stirred under N2 (1 atm) at 25 °C for three hours until the
pale-yellow solution turned bright yellow. Addition of n-pentane
(30 mL) to the resulting solution yielded yellow microcrystals,
which were isolated by filtration, washed with methanol (3 × 10
mL), and dried under vacuum. The yield was 78 mg and 92% based
1
on 1d. H NMR (300 MHz; CDCl3): δ 8.83 (d, J ) 5.1 Hz, 1H),
7.40-7.34 (m, 12H), 7.24-7.09 (m, 21H), 6.67 (t, J ) 8.1 Hz,
2H), 6.45 (td, J ) 7.8, 1.8 Hz, 1H), 6.18 (t, J ) 7.2 Hz, 1H), -17.45
(t, J ) 15.6 Hz, 1H). 13C NMR (75.5 MHz, CDCl3): δ 166.20,
159.24, 152.50, 145.73, 144.85, 135.26, 133.95, 131.92, 129.54,
129.28, 127.52, 123.10, 121.16, 120.52, 118.09. 31P NMR (81 MHz,
CDCl3): δ 12.85. (s). IR (KBr, cm-1): 2130 (m, νIr-H), 2101 (s,
ν
CN). Anal. Calcd for IrC48N2H39P2: C, 64.20; H, 4.38; N, 3.12.
ν
C′o), 1265, 1153 and 1031 (s, OTf-). Anal. Calcd for
Found: C, 64.26; H, 4.34; N, 3.15.
Inorganic Chemistry, Vol. 47, No. 14, 2008 6291

Eum et al.
Ir(F2ppy)(H)(CN)(PPh3)2 (1dF2). 1H NMR (300 MHz; CDCl3):
δ 8.91 (d, J ) 5.4 Hz, 1H), 7.75 (d, J ) 8.4 Hz, 1H), 7.43-7.34
(m, 12H), 7.27-7.15 (m, 19H), 6.53 (t, J ) 6.9 Hz, 1H), 6.12-6.04
(m, 1H), 6.02 (t, J ) 9.0 Hz, 1H), -17.62 (t, J ) 15.9 Hz, 1H).
13C NMR (75.5 MHz, CDCl3): δ 162.85, 152.91, 136.06, 133.88,
131.40, 129.63, 127.67, 125.86, 122.46, 122.16, 121.39, 100.11,
96.45. 19F NMR (188.2 MHz, CDCl3): δ -113.33 (q, J ) 9.0 Hz,
1F), -114.73 (t, J ) 6.7 Hz, 1F). 31P NMR (81 MHz, CDCl3): δ
9.33 (s). IR (KBr, cm-1): 2147 (m, νIr-H), 2106 (s, νCN). Anal.
Calcd for IrC48N2H37F2P2: C, 61.73; H, 3.99; N, 3.00. Found: C,
61.77; H, 4.02; N, 2.98.
130.41, 128.68, 128.17, 127.08, 126.69, 126.30, 126.13, 126.03,
124.15, 120.77. 31P NMR (81 MHz, CDCl3): δ -13.01 (s). IR (KBr,
cm-1): 2056 (s, νC’O), 1271, 1152 and 1031 (s, OTf-). Anal. Calcd
for IrC49NH38ClF3O4SP2: C, 54.32; H, 3.53; N, 1.29. Found: C,
54.36; H, 3.50; N, 1.28.
Synthesis of Ir(ppy)(Cl)(CN)(PPh3)2 (2d). A reaction mixture
of [Ir(ppy)(Cl)(NCMe)(PPh3)2](OTf) (2b, 0.10 g, 0.09 mmol) and
tetrabutylammonium cyanide (27 mg, 0.10 mmol) in CH2Cl2 (10
mL) was stirred under N2 (1 atm) at 25 °C for three hours before
the pale-yellow solution turned bright yellow. Addition of n-pentane
(30 mL) to the resulting solution yielded yellow microcrystals,
which were isolated by filtration, washed with methanol (3 × 10
mL), and dried under vacuum. The yield was 80 mg and 94% based
on 2d. 1H NMR (300 MHz; CD2Cl2): δ 8.30 (d, J ) 6.0 Hz, 1H),
7.43-7.37 (m, 13H), 7.32-7.20 (m, 8H), 7.13-7.08 (m, 13H), 6.89
(t, J ) 7.5 Hz, 1H), 6.60 (t, J ) 7.5 Hz, 1H), 5.99 (t, J ) 7.5 Hz,
1H). 13C NMR (75.5 MHz, CD2Cl2): δ 167.92, 155.46, 153.75,
145.09, 137.98, 136.37, 134.80, 130.59, 130.24, 129.93, 127.72,
122.88, 122.63, 122.55, 118.17. 31P NMR (81 MHz, CD2Cl2): δ
-12.58 (s). IR (KBr, cm-1): 2103 (s, νCN). Anal. Calcd for
IrC48N2H38ClP2: C, 61.83; H, 4.11; N, 3.00. Found: C, 61.856; H,
4.13; N, 3.02.
1
Ir(F2Meppy)(H)(CN)(PPh3)2 (1dF2Me). H NMR (300 MHz;
CDCl3): δ 8.73 (d, J ) 5.1 Hz, 1H), 7.55 (s, 1H), 7.39-7.36 (m,
12H), 7.22-7.14 (m, 18H), 6.38 (d, J ) 4.8 Hz, 1H), 6.09-6.01
(m, 1H), 5.99 (d, J ) 9.6 Hz, 1H), 2.26 (s, 3H), -17.67 (t, J )
15.3 Hz, 1H). 13C NMR (75.5 MHz, CDCl3): δ 162.44, 152.29,
147.67, 133.95, 131.55, 129.60, 127.64, 125.92, 123.48, 122.55,
100.14, 96.42, 21.29. 19F NMR (188.2 MHz, CDCl3): δ -113.73
(q, J ) 5.8 Hz, 1F), -114.79 (t, J ) 6.7 Hz, 1F). 31P NMR (81
MHz, CDCl3): δ 9.16 (s). IR (KBr, cm-1): 2140 (m, νIr-H), 2104
(s, νCN). Anal. Calcd for IrC49N2H39F2P2: C, 62.08; H, 4.15; N,
2.95. Found: C, 62.02; H, 4.17; N, 2.97.
Synthesis of Ir(ppy)(Cl)2(PPh3)2 (2a). A reaction mixture of
IrCl3 ·xH2O (0.1 g, 0.33 mmol), PPh3 (0.26 g, 1 mmol), and ppyH
(0.16 g, 1 mmol) in 2-ethoxyethanol (30 mL) and water (10 mL)
was refluxed under N2 (1 atm) for 12 h. After cooling down to 25
°C, the yellow precipitate was filtered off and washed with methanol
(10 mL) and dichloromethane (60 mL) and dried under vacuum.
Results and Discussion
Synthesis and Charaterizations. New cationic and neutral
monocyclometalated iridium(III) complexes, [Ir(C^N)-
(PR3)2LL′]0,+ (1 and 2) have been prepared according to
procedures depicted by Schemes 1 and 2, characterized by
detailed NMR (1H, 13C, 19F, 31P), IR, and elemental analysis
data, and also by X-ray diffraction data analysis for the
crystals of Ir(ppy)(PPh2Me)2(H)(Cl) (1aPPh2Me) and
[Ir(ppy)(PPh3)2(Cl)(NCMe)]+ (2b). The crystal structure of
1aPPh2Me (Figure 2) unambiguously shows the Cl ligand
being trans to the carbon atom of the phenyl ring of the ppy
ligand, whereas Figure 3 shows the chlorine ligand being
trans to the nitrogen of pyridyl ring in 2b. The Ir-Cl distance
is significantly shorter in 2b (2.3882 Å) than in 1aPPh2Me
(2.4943 Å), probably due to the higher trans effect of the
carbon ligand in 1aPPh2Me, whereas the Ir-P distance is
longer for 2b (2.390 Å) than in 1aPPh2Me (2.305 Å), which
may be understood by PPh2Me being less bulky and more
basic than is PPh3.
Luminescence Properties. Ancillary Ligand (L and
L′) Effects. Knowing that d orbitals of iridium are involved
in the HOMO of ppy complexes such as Ir(ppy)3 and
Ir(ppy)2LL′,16 one could expect the HOMO energy level
being lowered by strong field ligands more than by weak
field ligands. Table 2 summarizes photoluminescence data
for 1 and 2. Significantly longer wavelength emission λmax
are measured for the two complexes 1a and 2a that contain
a chlorine ligand trans to the carbon of the ppy ligand,
whereas the emission λmax is measured at much shorter
wavelengths for all other complexes 1b-d without the
chlorine ligand and 2b-d that contain a chlorine ligand trans
to the nitrogen of the ppy ligand (Table 2). The weak field
ligand chlorine does not seem to play a role of lowering d
orbitals of iridium when it is in trans position to the strong
field ligand atom carbon of ppy as in 1a and 2a, whereas no
1
The yield was 0.19 g and 61% based on 2a. H NMR (300 MHz;
CD2Cl2): δ 8.57 (d, J ) 5.7 Hz, 1H), 7.43-7.37 (m, 13H),
7.30-7.17 (m, 8H), 7.14-7.04 (m, 13H), 6.79 (t, J ) 7.5 Hz, 1H),
6.43 (t, J ) 7.5 Hz, 1H), 6.08 (t, J ) 7.5 Hz, 1H). 31P NMR (81
MHz, CD2Cl2): δ -15.28 (s).
Synthesis of [Ir(ppy)(Cl)(NCMe)(PPh3)2](OTf) (2b). A reaction
mixture of Ir(ppy)(Cl)2(PPh3)2 (2a, 0.10 g, 0.10 mmol) and AgOTf
(26 mg, 0.10 mmol) in CHCl3 (10 mL) in the presence of MeCN
(1.0 mL) was stirred under nitrogen at 25 °C for two hours, and
the white precipitate (AgCl) was removed by filtration. A 1.0 mL
of MeCN was added into the filtrate solution, and the resulting
solution was stirred further for two hours under N2 before n-pentane
(30 mL) was added to yield pale-yellow microcrystals, which were
collected by filtration, washed with n-pentane (3 × 10 mL), and
dried under vacuum. The yield was 0.11 g or 95% based on 2b. 1H
NMR (300 MHz; CDCl3): δ 8.66 (d, J ) 5.7 Hz, 1H), 7.47 (d, J
) 7.8 Hz, 1H), 7.30-7.22 (m, 18H), 7.18-7.13 (m, 13H),
7.10-6.96 (m, 3H), 6.85-6.76 (m, 2H), 2.16 (s, 3H). 13C NMR
(75.5 MHz, CDCl3): δ 165.51, 153.08, 145.02, 138.10, 137.57,
137.19, 134.36, 133.82, 128.09, 127.27, 125.07, 123.74, 123.54,
123.06, 118.99, 118.18, 4.10. 31P NMR (81 MHz, CDCl3): δ -14.77
(s). IR (KBr, cm-1): 2286 (m, νN′C ), 1277, 1150 and 1031 (s,
Me
OTf-). Anal. Calcd for IrC50N2H41ClF3O3SP2: C, 54.77; H, 3.77;
N, 2.55. Found: C, 54.78; H, 3.80; N, 2.58.
Synthesis of [Ir(ppy)(Cl)(CO)(PPh3)2](OTf) (2c). A 0.1 g (0.09
mmol) of 2b in CH2Cl2 (10 mL) was stirred under CO (1 atm) at
25 °C for 12 h before n-pentane (30 mL) was added to precipitate
white microcrystals, which were isolated by filtration, washed with
n-pentane (3 × 10 mL), and dried under vacuum. The yield was
94 mg and 95% based on 2c. 1H NMR (300 MHz; CDCl3): δ 7.51
(d, J ) 6.0 Hz, 1H), 7.22 (t, J ) 7.5 Hz, 1H), 7.09 (d, J ) 7.8 Hz,
1H), 7.02-6.97 (m, 6H), 6.89-6.77 (m, 26H), 6.61 (d, J ) 7.8
Hz, 1H), 6.41 (t, J ) 7.8 Hz, 1H), 6.30 (t, J ) 6.0 Hz, 1H). 13C
NMR (75.5 MHz, CDCl3): δ 173.23, 165.16, 153.38, 150.91,
144.67, 139.71, 136.56, 134.32, 134.00, 133.56, 132.05, 131.56,
(16) Hay, P. J. J. Phys. Chem. A 2002, 106, 1634–1641.
6292 Inorganic Chemistry, Vol. 47, No. 14, 2008

Mono(2-phenylpyridinato)iridium(III) Complexes
Scheme 1. Synthesis of [Ir(ppy)(H)(L)(PPh3)2]+,0 (1a-d)
Scheme 2. Synthesis of [Ir(ppy)(Cl)(L)(PPh3)2]+,0 (2a-d)
such different effect has been measured between weak field
ligand chlorine (2b-2d) and strong field ligand hydrogen
(1b-1d) when chlorine and hydrogen are trans to the
medium ligand atom nitrogen of ppy. It may now be said
that blue color photoemission could be obtained by introduc-
ing a strong field ligand in the trans position to the carbon
atom of the ppy ligand.
complexes having chlorine.18 Very low ΦPL are also mea-
sured in this study for complexes having two chlorine
ligands. It is also noticed that 1 and 2 show lower quantum
2
yields than the other types of complexes, Ir(ppy)3 and
Ir(ppy)2LL′.3
Axial and Trans Ligand (PR3) Effects. PPh2Me is more
basic and less bulky than is PPh3 and makes a stronger bond
with metal as seen in crystal structures of 1aPPh2Me (Ir-P:
2.30 Å, Figure 2) and 2b (Ir-P: 2.39 Å, Figure 3). No
significant change in photoluminescent characteristics has
been observed between 1a (emission λmax at 468, 495 nm;
The quantum yield is known to decrease with shifting
emission λmax to shorter wavelength17 and to be low for
(17) Li, J.; Djurovich, P. I.; Alleyne, B. D.; Yousufuddin, M.; Ho., N. N.;
Thomas, J. C.; Peters, J. C.; Bau, R.; Thompson, M. E. Inorg. Chem.
2005, 44, 1713–1727.
(18) Williams, J. A. G. Top. Curr. Chem. 2007, 281, 205–268.
Inorganic Chemistry, Vol. 47, No. 14, 2008 6293

Eum et al.
Table 2. Emission Spectral Data for [Ir(ppy)(PPh3)2(H)(L)]0,+ (1) and
0, +
3
[Ir(ppy)(PPh )2(Cl)(L)]
compound number
(2) in Degassed CH2Cl2 at 25 °C
L
λmax (nm)
ΦPL
CIE (x, y)
1a
1b
1c
1d
2a
2b
2c
2d
Cl
NCMe
CO
CN
Cl
NCMe
CO
CN
468, 495
456, 487
452, 483
457, 487
468, 494
455, 486
452, 482
457, 487
0.110
0.075
0.140
0.170
0.008
0.066
0.066
0.028
0.18, 0.39
0.18, 0.32
0.18, 0.30
0.17, 0.27
0.18, 0.39
0.18, 0.32
0.18, 0.30
0.17, 0.27
Table 3. Emission Spectral Data for [Ir(C∧N)(PPh3)2(H)(L)]0,+ in
Degassed CH2Cl2 at 25 °C
compound
number
C^N
ppy
F2ppy
F2Meppy
ppy
F2ppy
F2Meppy
ppy
F2ppy
F2Meppy
ppy
L
λmax (nm)
ΦPL
CIE (x, y)
1a
Cl
Cl
Cl
468, 495
448, 475
446, 473
456, 487
441, 470
439, 467
452, 483
441, 469
439, 465
457, 487
441, 467
439, 465
0.110
0.057
0.053
0.075
0.220
0.140
0.140
0.200
0.170
0.170
0.500
0.430
0.18, 0.39
0.16, 0.20
0.16, 0.19
0.18, 0.32
0.16, 0.21
0.16, 0.20
0.18, 0.30
0.16, 0.20
0.16, 0.19
0.17, 0.27
0.16, 0.19
0.16, 0.18
1aF2
1aF2Me
1b
1bF2
1bF2Me
1c
1cF2
1cF2Me
1d
MeCN
MeCN
MeCN
CO
CO
CO
CN
CN
CN
1dF2
1dF2Me
F2ppy
F2Meppy
1a with PPh2Me. This result may be understood by that the
trans and axial ligand PR3 is not involved in the HOMO of
1, which is predicted by DFT calculations19 and also by a
theoretical study on [trans-Ir(C^N)2(PH3)2]+, showing that
the axial ligand PH3 barely affects the occupied MOs.4b
Effects of Modification of ppy. According to DFT
calculations, the HOMO is an admixture of π-orbitals of
phenyl ring of ppy and d-orbitals of metal and the LUMO
is primarily π-orbitals of pyridyl ring of ppy ligand. Electron
withdrawing groups on the phenyl ring, therefore, would
lower the HOMO energy level, whereas electron donation
groups on the pyridyl ring would raise the LUMO energy
level.20
Figure 2. ORTEP of Ir(ppy)(PPh2Me)2(H)(Cl) (1aPPh2Me) with 30%
thermal ellipsoids probability. Bond distances (Å): Ir-N(1), 2.140(2);
Ir-C(12), 2.013(3); Ir-H(1), 1.41(3); Ir-Cl(1), 2.4943(7); Ir-P(13),
2.3053(8); Ir-P(27), 2.3053(8). Bond angle (deg): N(1)-Ir-H(1), 173.8(11);
C1(2)-Ir-Cl(1), 174.09 (8); P(13)-Ir-P(27), 177.31(3).
Table 3 summarizes photoemission characteristics of 1
with modified ppy ligands. Modification of the ppy ligand
seems to be an efficient method to make emission λmax of 1
shifted to shorter wavelength. Well-studied ppy derivatives
such as F2ppy and F2Meppy are good enough to make
significant blue-shifts for complexes of F2ppy and F2Meppy
to display blue color emission.
Figure 4 shows both of the two emission peaks blue shifted
by modification of ppy to F2ppy and F2Meppy. Those two
emission peaks for F2ppy and F2Meppy complexes in the
ranges of 439-448 and 465-475 nm make their CIE
coordinates to be x ) 0.16 and y ) 0.18-0.21, representing
deep and sky blue color (Table 3 and Figure 5).
It is striking to see such large decreases in CIE coordinates
especially for y values from 0.27-0.39 down to 0.18-0.21
by modification of ppy to F2ppy and F2Meppy, whereas
the x value shows only slight decreases from 0.17-0.18
down to 0.16-0.17 for all complexes of F2ppy and
Figure 3. ORTEP of [Ir(ppy)(PPh3)2(Cl)(NCMe)]+ (2b) with 30% thermal
ellipsoids probability. Bond distances (Å): Ir-N(1), 2.051(6); Ir-C(12),
2.018(8); Ir-Cl(54), 2.3882(19); Ir-N(13), 2.129(7); Ir-P(16), 2.389(2);
Ir-P(35), 2.391(2). Bond angle (deg): N(1)-Ir-Cl(54), 176.00(19); C(12)-
Ir-N(13), 174.6(3); P(16)-Ir-P(35), 178.70(7).
(19) Kim, C. Ph.D. Thesis, Sogang University, 2007.
(20) Di Censo, D.; Fantacci, S.; De Angelis, F.; Klein, C.; Evans, N.;
Kalyanasundaram, K.; Bolink, H. J.; Gra¨tzel, M.; Nazeeruddin, M. K.
Inorg. Chem. 2008, 47, 980–989.
ΦPL ) 0.11) and 1aPPh2Me (emission λmax at 467, 494 nm;
ΦPL ) 0.10) prepared by replacing the axial ligand PPh3 of
6294 Inorganic Chemistry, Vol. 47, No. 14, 2008

Mono(2-phenylpyridinato)iridium(III) Complexes
We also mention here that our preliminary experimental
data (Supporting Information) obtained from the OLED
device fabricated with 1aF2 show the electro emission λmax
at quite a short wavelength (439 nm), whereas 1aF2 emits
the photo emission at 448 and 475 nm in Table 2.
Summary
Significant blue-shifts of emission λmax have been obtained
by replacing the weak-field ligand chlorine of
Ir(ppy)(PPh3)2(H)(Cl) (where hydrogen is trans to the
nitrogen of ppy) with stronger field ligands L′ to produce
[Ir(ppy)(PPh3)2(H)(L′)]0,+ (L′ ) CO, CN-, MeCN), which
emit blue color. Blue light emission (λmax ) 452-457,
482-487 nm) is also obtained by replacing only one chlorine
ligand that is trans to the carbon of ppy in the dichloro
complex Ir(ppy)(PPh3)2(Cl)2 and introducing ancillary field
ligands L to produce [Ir(ppy)(PPh3)2(Cl)(L)]0,+ (L ) MeCN,
CO, CN-). Further blue shifts (13-22 nm) of the emission
λmax are measured by modification of the ppy ligand for
F2ppy and F2Meppy complexes to display deep and sky-
blue color with CIE coordinates of (x ) 0.16, y )
0.18-0.21).
Figure 4. Normalized emission spectra of Ir(ppy)(PPh3)2(H)(Cl) (1a) (-9-
9-), Ir(F2ppy)(PPh3)2(H)(Cl) (1aF2) (-b-b-), and Ir(F2Meppy)(PPh3)2(H)(Cl)
(1aF2Me) (-2-2-) in degassed CH2Cl2 at 25 °C.
Acknowledgement. The authors wish to thank the Korea
Research Foundation for their financial support of this study
through the Basic Research Institute Program (Grant 2005-
015-C00222), the second stage Brain Korea 21 Program, the
Interdisciplinary Program of Integrated Biotechnology, Prof.
K. B. Yoon, Chemistry Department, at Sogang University,
and the KOSEF grant funded by MOST in Korea (Grant
ROA-2007-000-20088-0).
Figure 5. (a) From left, photoemission cells containing Ir(ppy)(PPh3)2-
(H)(CN) (1d), Ir(F2ppy)(PPh3)2(H)(CN) (1dF2), and Ir(F2Meppy)(PPh3)2-
(H)(CN) (1dF2Me) in CH2Cl2. (b) CIE coordinates for 1d and 1dF2 (1dF2Me
is not shown as it is practically the same with 1dF2).
Supporting Information Available: X-ray crystallographic data
1
in CIF format and H and 13C NMR spectra and OLED studies.
F2Meppy. Such low values in both x (0.16-0.17) and y
(0.18-0.21) of CIE coordinates obtained in this study are,
to the best our knowledge, unprecedented for Ir-ppy
complexes, whereas some bis-ppy iridium and related
complexes show relatively low CIE coordinates at x )
0.16-0.17 and y ) 0.26-0.32.21
This material is available free of charge via the Internet at
http://pubs.acs.org.
IC800376E
(21) Yeh, S.-J.; Wu, M.-F.; Chen, C.-T.; Song, Y.-H.; Chi, Y.; Ho, M.-H.;
Hsu, S.-F.; Chen, C. H. AdV. Mater. 2005, 17, 285–289.
Inorganic Chemistry, Vol. 47, No. 14, 2008 6295