J Fluoresc
diluted carefully with boiling water and extracted with chlo-
roform. The aqueous solutions were combined and acidified
to pH 4 with concentrated HCl. The precipitate was filtered
off, washed with water, and recrystallized in ethanol to give
Ir(pcl)2(fpic) (fpic=5-fluoro-2-picolinic acid)
Complex Ir(pcl)2(fpic) was synthesized with the similar
method using 5-fluoro-2-picolinic acid in place of picolinic
acid as ancillary ligand, the yield of 60 % with brown
powder. FT-IR (KBr pellet, cm−1): 1,633, 1,588, 1,332,
1,258, 1,230, 1,100, 1,038, 798. 1H-NMR (CDCl3,
400 MHz) δ 8.46 (d, J=8.4 Hz, 1H, fpic ring), 8.36
(d, J=15.2 Hz, 2H, cinnoline ring), 8.28 (d, J=3.2 Hz, 1H,
fpic ring), 7.90 (d, J=6.8 Hz, 3H, cinnoline ring and fpic
ring), 7.71–7.77 (m, 3H, cinnoline ring), 7.63–7.68 (m, 3H,
cinnoline ring), 7.52 (t, J=16 Hz, 2H, phenyl), 6.98
(t, J=12 Hz, 1H, phenyl), 6.87 (t, J=16 Hz, 1H, phenyl),
6.77 (t, J=16 Hz, 1H, phenyl), 6.69 (t, J=16 Hz, 1H, phenyl),
6.22 (d, J=7.6 Hz, 1H, phenyl), 6.08 (d, J=7.6 Hz, 1H,
phenyl). MALDI-TOF MS m/z 766.639 ([Ir(pcl)2(fpic)+Na]+).
1
a yellow prism (4.32 g, 86 %). m.p. 233–234 °C. H-NMR
(CDCl3, 400 MHz) δ 14.57 (br, 1H, -COOH), 8.61
(d, J=7.6 Hz, 1H, cinnoline ring), 8.01–8.06 (m, 3H, cinnoline
ring), 7.84 (d, J=8 Hz, 2H, phenyl), 7.56–7.62 (m, 3H, phenyl).
3-phenylcinnoline (pcl) (4)
A mixture of 3 (3 g, 12 mmol), NaCl (5 g, 85.6 mmol),
DMSO (50 mL), and H2O (5 mL) was stirred at 120 °C for
6 h. After cooling, the mixture was poured into cold water
and extracted with ethyl acetate. The organic layer was
washed with saturated NaCl solution, dried over Na2SO4,
and evaporated to dryness. The residue was purified by
column chromatography on silica gel with trichloromethane
as eluent to give 4 as a yellow needle (1.98 g, 80 %). m.p.
112–113 °C. FT-IR (KBr pellet, cm−1): 1,588, 1,439, 1,326,
Results and Discussion
1
1,094, 906, 748, 702. H-NMR (CDCl3, 400 MHz) δ 8.58
Synthesis and Characterization
(d, J=8.4 Hz, 1H, cinnoline ring), 8.21–8.25 (m, 3H,
cinnoline ring), 7.88 (d, J=8 Hz, 1H, cinnoline ring), 7.81
(t, J=15.2 Hz, 1H, phenyl), 7.74 (t, J=14.8 Hz, 1H, phenyl),
7.55 (t, J=14.8 Hz, 2H, phenyl), 7.48 (t, J=14.4 Hz, 1H,
phenyl).
Scheme 1 represents a general synthetic route to prepare the
ligand and the corresponding complexes. The formation of
Ir-complexes are reasonably proved by FTIR spectra of
Ir(pcl)2(pic) and Ir(pcl)2(fpic), as shown in Fig. S1 in
ESI, in which not only the vibration absorptions at 1,588
and 1,094 cm−1 attributed to C=N and C=C in
cyclometalating ligand are recognized, but also the char-
acteristic absorption peaks at 1,633 and 1,038 cm−1 orig-
inating from C=N and C=C in ancillary ligand are
recognized. The absorptions at 1,718 and 1,263 cm−1 in
the IR spectra of complexes may be attributed to C=O
and C-O stretching vibrations of the carboxyl groups in
ancillary ligands. In addition, the broad and strong ab-
sorption peak at 3,000~2,500 cm−1 associated with O-H
stretching vibrations of the carboxyl groups in ancillary
ligands is not observed. All of the data suggested that
both cyclometalating ligands and ancillary ligands were
excellently coordinated with the metal iridium(III).
Ir(pcl)2(pic) (pic=picolinic acid)
To a round-bottomed flask (50 mL), compound 4 (0.33 g,
1.6 mmol), IrCl3·3H2O (0.2 g, 0.63 mmol), 2-ethoxyethanol
(15 mL) and H2O (5 mL) were added sequentially. The
mixture was stirred under nitrogen at 120 °C for 24 h and
cooled to room temperature. The precipitate was filtered off,
washed with ethanol and acetone and dried in vacuum to
give 5 as a dark red solid (0.2 g, 53 %). In a round-bottomed
flask (50 mL), a mixture of compound 5 (0.1 g, 0.17 mmol),
picolinic acid (0.042 g, 0.34 mmol), triethylamine (1 mL)
and dichloromethane (30 mL) was stirred at room tempera-
ture for 12 h. The solvent was evaporated, and the product
was purified by column chromatography (silica gel, eluent
dichloromethane/methanol, 20:1, v/v) to give Ir(pcl)2(pic) as
a dark red solid (0.057 g, 65 %). FT-IR (KBr pellet, cm−1):
As shown in Fig. 1, in 1H NMR spectroscopy, the
protons such as H1, H2 and H3 which localize in the
two same cyclometalating ligands respectively show dif-
ferent chemical shift, and this phenomenon can be under-
stood that the protons have different environment by
coordinating with the iridium(III) ion. On the other hand,
the protons of pcl in iridium(III) complexes show an
upfield shift compared with the same ones in free ligands.
For example, this phenomenon is observed for the proton
9 as well as the proton 1 adjacent to the metalated carbon
of the cyclometalating ligand. This can be rationalized in
terms of the reduction in electron density in the aromatic
ring that accompanies cyclometalation. Additionally, the
1
1,628, 1,588, 1,360, 1,332, 1,258, 1,095, 1,038, 798. H-
NMR (CDCl3, 400 MHz) δ 8.47 (d, J=8 Hz, 1H, pic ring),
8.35 (d, J=12 Hz, 2H, cinnoline ring), 8.25 (d, J=8 Hz, 1H,
pic ring), 7.86–7.90 (m, 3H, cinnoline ring and pic ring),
7.80 (t, J=16 Hz, 1H, pic ring), 7.71–7.75 (m, 3H, cinnoline
ring), 7.66 (d, J=4 Hz, 3H, cinnoline ring), 7.60 (d, J=8 Hz, 2H,
phenyl), 6.96 (t, J=16 Hz, 1H, phenyl), 6.87 (t, J=12 Hz, 1H,
phenyl), 6.76 (t, J=16 Hz, 1H, phenyl), 6.69 (t, J=12 Hz, 1H,
phenyl), 6.24 (d, J=8 Hz, 1H, phenyl), 6.11 (d, J=8 Hz, 1H,
phenyl). MALDI-TOF MS m/z 748.644 ([Ir(pcl)2(pic)+Na]+).