Sulfonyl-Substituted Heteroleptic Cyclometalated Iridium(III) Complexes as Blue Emitters for Solution-Processable Phosphorescent Organic Light-Emitting Diodes

Article abstract of DOI:10.1021/acs.inorgchem.6b01179

The synthesis is reported of a series of blue-emitting heteroleptic iridium complexes with phenylpyridine (ppy) ligands substituted with sulfonyl, fluorine, and/or methoxy substituents on the phenyl ring and a picolinate (pic) ancillary ligand. Some deriv

Full text of DOI:10.1021/acs.inorgchem.6b01179

Article
pubs.acs.org/IC
Sulfonyl-Substituted Heteroleptic Cyclometalated Iridium(III)
Complexes as Blue Emitters for Solution-Processable
Phosphorescent Organic Light-Emitting Diodes
Helen Benjamin,† Yonghao Zheng,† Andrei S. Batsanov,† Mark A. Fox,† Hameed A. Al-Attar,‡
Andrew P. Monkman,‡ and Martin R. Bryce*,†
‡
†Department of Chemistry and Department of Physics, Durham University, Durham DH1 3LE, U.K.
S
* Supporting Information
ABSTRACT: The synthesis is reported of a series of blue-emitting
heteroleptic iridium complexes with phenylpyridine (ppy) ligands
substituted with sulfonyl, fluorine, and/or methoxy substituents on
the phenyl ring and a picolinate (pic) ancillary ligand. Some
derivatives are additionally substituted with a mesityl substituent on
the pyridyl ring of ppy to increase solubility. Analogues with two
ppy and one 2-(2′-oxyphenyl)pyridyl (oppy) ancillary ligand were
obtained by an unusual in situ nucleophilic displacement of a
fluorine substituent on one of the ppy ligands by water followed by
N^O chelation to iridium. The X-ray crystal structures of seven of the complexes are reported. The photophysical and
electrochemical properties of the complexes are supported by density functional theory (DFT) and time-dependent DFT
calculations. Efficient blue phosphorescent organic light-emitting devices (PhOLEDs) were fabricated using a selection of the
complexes in a simple device architecture using a solution-processed single-emitting layer in the configuration ITO/
PEDOT:PSS/PVK:OXD-7(35%):Ir complex(15%)/TPBi/LiF/Al. The addition of a sulfonyl substituent blue-shifts the
EL
electroluminescence by ca. 12 nm to λ 463 nm with CIEx,y coordinates (0.19, 0.29), compared to the benchmark complex
max
EL
max
FIrpic (λ 475 nm, 0.19, 0.38) in directly comparable devices, confirming the potential of the new complexes to serve as
effective blue dopants in PhOLEDs. Replacing a fluorine by a methoxy group in these complexes red shifts the PL and EL λmax by
ca. 4−6 nm. The efficiency of the blue PhOLEDs of the sulfonyl-substituted complexes is, in most cases, significantly enhanced
by the presence of a mesityl substituent on the pyridyl ring of the ppy ligands.
ligands to blue-shift the emission by lowering the HOMO
energy without significantly changing the LUMO energy.15,16
For heteroleptic complexes [Ir(C^N)2L] the ancillary ligand L
can also be used to tune the emission color. The complex
iridium(III) bis[4,6-(difluorophenyl)pyridinato-N,C-2′]-
picolinate (FIrpic 1; Figure 1) is the benchmark sky-blue
emitter for phosphorescent OLEDs (PhOLEDs).17−22 Other
structural modifications that give blue emission involve
different ancillary ligands such as N-heterocyclic carbenes,23
INTRODUCTION
■
Luminescent transition metal complexes are widely exploited in
many areas,1 such as biological labeling probes, ion sensors,
water splitting, solar cells, and phosphorescent emitters for
organic light-emitting diodes (OLEDs)2−8 and for solid-state
lighting.9,10 In the OLED and lighting field cyclometalated
iridium(III) complexes have received special attention because
they can harvest both singlet and triplet excitons, leading to
internal quantum efficiencies approaching 100%.11−13 Key
features of the complexes include their synthetic versatility,
good color tuneability, generally good chemical and photo-
chemical stability, relatively short excited-state lifetimes on the
microsecond time scale, and highly efficient emission from a
mixture of triplet metal-to-ligand charge-transfer (MLCT)
states and π−π* transitions of the ligands.14 Tris-homoleptic
complexes [Ir(C^N)3], where C^N is a monoanionic bidentate
ligand, have been extensively studied, for example, the
prototype green emitter fac-Ir(ppy)3 (ppy = 2-phenylpyr-
idine).2 The highest occupied molecular orbital (HOMO) is
primarily localized on the phenyl π and iridium d orbitals, while
the lowest unoccupied molecular orbital (LUMO) resides
mainly on the pyridine ring. Electron-withdrawing substituents,
typically fluorine, are attached to the phenyl ring of the ppy
Figure 1. Structure of FIrpic 1.
Received: May 16, 2016
© XXXX American Chemical Society
A
DOI: 10.1021/acs.inorgchem.6b01179
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a
Scheme 1. Synthesis of Complexes 10−15
a
Reagents and conditions: (i) LDA, THF, −78 °C, I2, THF, 20 °C; (ii) NaMeSO2 or Nap-TolSO2, CuI, DMF, 110 °C; (iii) NaMeSO2, CuI, I2,
DMF, 110 °C; (iv) IrCl3·3H2O, 2-ethoxyethanol, 130 °C, followed by picolinic acid, 130 °C; (v) IrCl3·3H2O, 2-ethoxyethanol, 130 °C, followed by
ligand 6 or 7, NEt3, acetylacetone, ethylene glycol, 190 °C.
pyridylazolate derivatives,24 fluorine-substituted bipyridine
chelates,25 and dicyclometalated phosphate tripod ligands.26
The motivation for the present work was provided by the high
level of ongoing research to develop new blue-emitting
phosphors.27,28
incorporated as substituents on C^N cyclometallating ligands in
either neutral35 or ionic36 complexes. With the exception of
complex 11, which has been reported previously by Fan et al.
using a different method to introduce the p-toluenesulfonyl
substituent,35e to our knowledge the sulfone-containing
complexes studied in this work have not been synthesized
previously. The synthetic routes to complexes 10−15, 23−25,
and 31 are shown in Schemes 1−3. All the complexes are
characterized by NMR spectroscopy, mass spectrometry, and
elemental analysis, with additional single-crystal X-ray crystallo-
graphic data for seven of the complexes.
The key step to introduce the sulfone substituent involves
lithiation of 2-(2,4-difluorophenyl)pyridine 237 or the mesityl
analogue 3 with lithium diisopropylamide (LDA), followed by
iodination to yield 4 and 5 and then reaction with either
sodium p-toluenesulfinate or sodium methylsulfinate in the
presence of stoichiometric copper(I) iodide, to afford ligands
6−8 in 15−26% yields (Scheme 1). These yields were highly
reproducible in several reactions and could not be improved by
ultilising a copper(II) bis(arylsulfinate) reagent,38 a CuI/L-
proline system,39 or ionic liquid additives.40 On one occasion,
when using a batch of 4 that had not been rigorously purified
(and was probably contaminated with iodine from the previous
reaction) the di(methanesulfonyl) derivative 9 was also isolated
in 11% yield alongside product 6. When the reaction was
repeated with rigorously purified 4 and the addition of a trace
of iodine, compound 9 was again obtained in very low yield.
Exploring the mechanism of this reaction is outside the scope of
this work. However, it can be postulated: (i) that iodine
coordinates to the pyridyl N atom of ligand 4 or 6 to form a
more electron-withdrawing pyridinium unit, thereby further
increasing the reactivity (by increased electron deficiency) of
the phenyl ring, or (ii) that a fluorine in ligand 4 or 6 is
This article describes the synthesis and X-ray structural and
optoelectronic characterization of a systematic series of
analogues of FIrpic 1 in which the phenyl ring bears a sulfonyl
substituent at the C3 position to further lower the HOMO
energy and blue-shift the emission. Additionally, we report
derivatives with one or both of the fluorine atoms at C2 and C4
replaced by a methoxy group. The rationale here is that
substituting one fluorine with an alkoxy group is known to have
a minimal effect on the emission color while increasing the
chemical stability of the complex to unwanted nucleophilic
substitution reactions29,30 during, or after, complex formation.31
It is also known that di/multifluorinated ligands can degrade
during OLED operation.32 In some of the complexes a mesityl
substituent is attached to C4 of the pyridyl ring, as it has been
reported that this functionalization leads to enhanced PhOLED
efficiency,33 which is also the case for several complexes in the
present work. The experimental photophysical and electro-
chemical data are supported by time-dependent density
functional theory (TD-DFT) calculations. Blue PhOLEDs
were fabricated with selected complexes as the emitter.
RESULTS AND DISCUSSION
■
It has been established previously that functionalizing the
phenyl ring of FIrpic 1 with an electron-withdrawing group at
C3 (i.e., between the two F atoms) induces a blue shift in
emission: examples are cyano,34 sulfonyl,35e phosphoryl,35e and
perfluoroalkyl carbonyl substituents.24b The present work
focuses on sulfonyl groups, which have only rarely been
B
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a
Scheme 2. Synthesis of Complexes 23−25
a
Reagents and conditions: (i) LDA, THF, −78 °C, I2, THF, 20 °C; (ii) NaMeSO2 or Nap-TolSO2, CuI, DMF, 110 °C; (iii) IrCl3·3H2O, 2-
ethoxyethanol, 130 °C, followed by picolinic acid, 130 °C.
a
Scheme 3. Synthesis of Complex 31
a
Reagents and conditions: (i) n-BuLi, hexane, THF, −78 °C, triisopropyl borate, −78 to 20 °C, dilute HCl; (ii) 2-chloro-4-mesitylpyridine, PPh3,
DME, Na2CO3, Pd(OAc)2, reflux; (iii) HCl, DCM/MeOH, RT; (iv) mcpba, DCM, 20 °C, NaHSO3; (v) [Ir(cod)Cl]2, 2-ethoxyethanol, 130 °C,
followed by picolinic acid, 130 °C.
replaced by iodine prior to the reaction with the methylsulfinate
anion. There is precedent for a combination of fluoro and iodo
substituents on a phenyl ring facilitating SNAr reactions at a C−
F bond.41
the dimethoxy ligand 30, a different synthetic approach was
used starting from the known compound 2642 (Scheme 3). In
this case, the sulfone functionality was obtained by oxidation of
the methylthio group of 29 with meta-chloroperbenzoic acid in
83% yield.
To obtain the picolinate complexes 10−13, 23−25, and 31
standard conditions were employed,43 namely, reaction of the
ligand with IrCl3·3H2O (or [Ir(cod)Cl]2 for 31) in 2-
ethoxyethanol to give a presumed bridged μ-dichloro diiridium
species [Ir(L)2Cl]2, which was reacted in situ with picolinic
acid. Attempts to isolate the intermediate dimer species were
unsuccessful in most cases and usually led only to unidentified
decomposed products. The attempted synthesis of 31 using
IrCl3·3H2O failed to yield any product, and the ligand 30 could
not be recovered. Difficulties in the cyclometalation of ligands
The synthesis of methoxy analogues 23−25 followed a
similar protocol starting from phenylpyridine derivatives 16 and
17, which were readily obtained by standard Suzuki reactions of
the commercially available 2-fluoro-4-methoxyphenylboronic
acid (Scheme 2). Notably, the conversions of 18 and 19 to
yield methanesulfonyl derivatives 20 and 21 proceeded in
significantly higher yields (45 and 53%, respectively) than the
comparable reactions of the difluoro analogues 4 and 5 in
Scheme 1. However, the yield of p-tolyl derivative 22 is still low
(21%).
To explore the effect of replacing both fluorine atoms with
methoxy substituents, complex 31 was synthesized. To obtain
C
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Figure 2. (a). X-ray molecular structures of 11−13 and 15. Minor disorder components, solvent of crystallization, and all H atoms are omitted;
thermal ellipsoids are drawn at the 50% probability level.
Table 1. Selected Bond Distances (Å)
10
11
12
13
15
23
31
Ir−N(1)
Ir−N(2)
Ir−N(3)
Ir−O(1)
Ir−C(7)
Ir−C(18)
2.137(3)
2.027(3)
2.046(3)
2.146(2)
1.974(3)
1.991(4)
2.134(3)
2.048(3)
2.029(3)
2.158(2)
1.985(3)
1.989(3)
2.140(5)
2.033(5)
2.033(5)
2.133(4)
1.986(6)
2.000(6)
2.128(3)
2.048(4)
2.040(4)
2.148(3)
1.994(4)
1.979(5)
2.161(4)
2.032(4)
2.037(4)
2.151(3)
1.982(5)
1.989(5)
2.129(4)
2.035(4)
2.041(4)
2.142(3)
1.987(4)
1.990(4)
2.120(4)
2.031(4)
2.037(4)
2.145(4)
1.993(5)
1.998(4)
a
a
a
Weighted average for the disordered ligands.
containing methoxy substituents using IrCl3·3H2O have been
reported previously.30b
spectra that established that a fluorine ortho to a pyridyl group
had been replaced on one of the ligands. The structures were
subsequently unambiguously confirmed by X-ray crystallog-
raphy of 15 (see below). The phenyl ring of ligands 6 and 7 is
highly electron-deficient due to the presence of pyridyl,
fluorine, and sulfone substituents; therefore, an SNAr reaction
at a C−F bond is entirely reasonable, for example, reaction with
residual water in the ethylene glycol sovent, with subsequent
N^O chelation as a 2-(2′-oxyphenyl)pyridyl (oppy) ancillary
ligand. We are not aware of a previous example of an Ir
complex of an oxyphenylpyridyl ligand. Indeed, six-membered
ring chelation to Ir with a bidentate N^O ancillary ring appears
Attempts to form the corresponding tris-cyclometalated
homoleptic [Ir(C^N)3] complexes from 6 and 7 using
established conditions,31d by adding more C^N chelate to the
[Ir(L)2Cl]2 species, gave the unexpected and unusual [Ir-
(C^N)2(N^O)] complexes 14 and 15 in 29% and 23% yields,
respectively. There was no sign of the homoleptic complexes
after purification of the product mixture. The structures of 14
and 15 were tentatively assigned based on mass spectra
combined with 19F NMR spectra, which showed the presence
1
of only five fluorine atoms, together with H NMR and COSY
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Figure 3. Normalized absorption (in dichloromethane, left) and emission (in degassed dichloromethane, right) solution-state spectra of complexes
1, 10, 13, 14, and 23.
Table 2. Photophysical Data of the Iridium Complexes
c
be
,
Stokes shift,
cm−1
PLQY,
bd
τP,
μs
a
b
(ε), nm (1 × 103 M−1cm−1
)
λ
,
nm
ΦPL
0.67
abs
max
em
max
,
complex
λ
1 FIrpic 277 (50.1), 301 (34.2), 304 (32.6), 337 (13.8, sh), 357 (8.9, sh), 400 (6.2), 454 (0.8) 468, 496, 531 (sh)
800
660
1.72
2.19
2.09
1.49
3.53
2.90
10
11
12
13
14
255 (88.6), 282 (67.2), 292 (61.7), 371 (9.4), 401 (sh, 3.8), 443 (0.6)
455, 482, 511 (sh)
0.64
0.68
0.68
0.48
0.44
252 (123.7), 286 (90.4), 300 (83.0), 331 (sh, 23.4), 373 (11.3), 407 (sh, 4.7), 444 (0.8) 457, 483, 515 (sh)
700
260 (100.4), 283 (76.4), 321 (sh, 30.9), 374 (13.1), 401 (sh, 5.0), 444 (0.9)
261 (89.1), 284 (80.2), 306 (b, 52.8), 399 (8.2), 452 (4.9), 490 (0.6)
457, 485, 517 (sh)
516, 536
700
1450
870
264 (95.5), 278 (85.1), 302 (sh, 58.1), 364 (19.4), 382 (sh, 15.9), 421 (sh, 4.3),
447 (1.3)
466, 491, 530 (sh)
15
250 (sh, 143.2), 266 (sh, 98.7), 290 (83.4), 312 (56.5), 368 (19.6), 414 (sh, 6.7),
449 (1.4)
469, 494, 534 (sh)
910
0.38
2.85
23
24
25
253 (89.0), 264 (97.7), 290 (87.0), 319 (sh, 35.6), 372 (10.2), 406 (sh, 4.5), 449 (0.6) 460, 489, 522 (sh)
255 (99.0), 269 (118.1), 291 (110.6), 336 (sh, 27.6), 376 (15.9), 402 (sh, 6.8), 450 (0.9) 461, 489, 523 (sh)
530
530
670
0.55
0.58
0.58
2.67
1.79
1.78
258 (sh, 108.5), 271 (128.6), 297 (123.4), 307 (sh, 112.5), 339 (sh, 29.2), 379 (15.7), 464, 490, 524 (sh)
450 (1.0)
31
275 (104.4), 291 (101.9), 324 (sh, 47.8), 381 (14.5), 405 (sh, 7.9), 456 (0.9)
474, 500, 536 (sh)
830
0.50
2.13
a
b
Data obtained in less than 10 μM dichloromethane solutions at 20 °C. Data obtained in degassed dichloromethane solution with excitation
c
d
wavelength at 380 nm. Energy difference between lowest energy excitation maxima and highest energy excitation maxima. Measured relative to
Ir(ppy)3 ΦPL = 0.46 in degassed dichloromethane at 20 °C; estimated error 5%. Estimated error 5%.
e
to be very rare:14b related examples include [Ir(C^N)2(N^O)]
structures with two ppy ligands and 2-(2′-oxyphenyl)oxazole44
or 2-(2′-oxyphenyl)oxazoline45 as the ancillary N^O ligand.
X-ray Crystal Structures. Single-crystal X-ray structures
were obtained for 10, 11·3CH2Cl2, 12·2.75CH2Cl2, 13·MeCN,
15·2CH2Cl2·0.85MeOH, 23·CH2Cl2, and 31·4CH2Cl2 (Figures
2 and S1−S6 and Table S1). A different polymorph of 11·
3CH2Cl2 with essentially the same molecular geometry has
been reported previously by Fan et al.35e In all the complexes,
the Ir atom has a slightly distorted octahedral coordination.
Table 1 lists bond lengths of all the structures with two C^N
ligands and one N^O picolinate ligand.
The N atoms of the two C^N ligands are coordinated trans
to each other. The picolinate ligand, as well as oppy ligand in
15, forms a longer Ir−N bond, due to trans-effect of the σ-
bonded C atom. In molecule 12, the methylsulfonyl and mesityl
groups of one C^N ligand are both disordered between two
orientations in a 0.55:0.45 ratio (the Mes by a flipping motion).
The Mes groups are nearly perpendicular to the adjacent Py
rings, the dihedral angles being 86° for the ordered Mes group,
82° and 73° for the disordered Mes groups. In structure 13,
one whole C^N ligand is disordered between two orientations
differing by a ca. 10° libration around the Ir atom, with
occupancies refined to 0.684(5) and 0.316(5), respectively. All
the chelating ligands show small but significant nonplanarity. In
the picolinato ligand, the dihedral angle between the Py and
carboxylate planes varies from 0.9° in 13 to 10.6° in 12. In the
C^N ligands, the twists between the phenyl and pyridine rings
are the highest in complex 23 (12.7° and 14.7°), in other
complexes they vary from 2° to 11°. The oxyphenyl-pyridine
moiety in 15 is much more twisted with the two aromatic rings
forming an angle of 37°.
Thermal, Photophysical, and Electrochemical Proper-
ties. The absorption and emission spectra of the complexes in
dichloromethane solution are shown in Figures 3 and S7−S10,
and the data are listed in Table 2. The complexes show strong
absorption bands in the 250−300 nm region derived from
ligand-centered π−π* transitions.17 Absorption bands in the
range of 350-450 nm with lower extinction coefficients are
ascribed to singlet and triplet metal-to-ligand charge-transfer
17
3
(1MLCT and MLCT) states, following literature precedents
and the calculations of Hay.46 Emission of the complexes is in
the blue or blue-green region. The following trends in this
series of complexes can be seen.
(i) Addition of the sulfone moiety results in a blue shift in
emission λmax relative to FIrpic of ∼10 nm. The identity
of the R group in −SO2R (tolyl or methyl) has little
effect on the optoelectronic properties.
(ii) Exchanging a fluoro for a methoxy substituent results in a
red shift of ∼5 nm. Therefore, all of the monofluoro−
monomethoxy complexes (23−25) have bluer emission
than FIrpic, while the dimethoxy−sulfone complex 31
has a λmax and emission profile comparable to FIrpic.
(iii) Addition of a mesityl group results in little change to
λmax, as observed previously.33
E
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Table 3. Electrochemical and Computed Molecular Orbital Energy Data of Iridium Complexes
a
ox
1/2
complex
E
,
V
obs HOMO, V
complex
calcd HOMO, eV
calcd LUMO, eV
calcd HLG eV
1 FIrpic
10
0.89[0.92 ref16]
−5.69
−5.99
−5.96
−5.95
−6.05
−5.73
−5.74
−5.82
−5.82
−5.81
−5.69
1′
−5.49
−6.09
−5.97
−6.01
−6.15
−5.80
−5.61
−5.82
−5.74
−5.64
−5.53
−1.87
−2.23
−2.15
−2.15
−2.46
−2.20
−2.04
−2.06
−2.00
−1.94
−1.89
3.62
3.86
3.82
3.86
3.69
3.60
3.57
3.76
3.74
3.70
3.64
1.19
10′
11′
12′
13′
14′
15′
23′
24′
25′
31′
11
1.16[1.21 ref35e]
12
1.15
13
1.25
b
b
14
0.93 (irr), 1.62 (irr)
15
0.94 (irr), 1.63 (irr)
23
1.02
1.02
1.01
0.89
24
25
31
Redox data were obtained in 0.1 M NBu4PF6 acetonitrile solutions and are reported vs FcH/FcH+.48 The values reported are the cathodic peak
a
b
potentials observed on the first scan.
an increase in oxidation potential of ∼0.28 V relative to that of
FIrpic, indicating the sulfone group is effective at lowering the
HOMO. Exchanging a fluorine for a methoxy group (23−25)
results in a smaller increase in oxidation potential of ∼0.13 V
relative to FIrpic, and the dimethoxy−sulfone complex 31 has
an oxidation potential comparable to that of FIrpic. If the
LUMO energies are assumed to be very similar in these
complexes, the relative HOMO energies from their CV data are
consistent with the λmax values obtained from the emission
spectra. The oxidation potential of 13 is +1.25 V, suggesting
that addition of the second sulfone moiety lowers the HOMO;
however, it must also lower the LUMO significantly, as the
emission spectrum is strongly red-shifted. Complexes 14 and
15 both show two irreversible oxidation waves; if the scan is
reversed before the second oxidation is reached the first
oxidation wave is still irreversible. This suggests a chemical
reaction takes place upon oxidation and could be attributed to
the unusual connectivity around the Ir center. No additional
ligand-centered oxidation waves were detected on scanning to
+2.0 V for the pic complexes, and no reduction waves were
observed on scanning between 0.0 and −2.0 V.
Density Functional Theory Calculations. Electronic
structure calculations were performed on the 11 iridium
complexes studied here (including FIrpic 1) to explore the
frontier orbitals and understand the nature of the transitions
involved in the absorption and emission bands observed
(Tables S3−S13). The full geometries of the iridium complexes
were optimized at B3LYP/LANL2DZ:3-21G*, and the
optimized geometries are denoted as 1′, 10′−15′, 23′−25′,
and 31′ to identify them as computed models and distinguish
the predicted data from experimental data. Comparison
between optimized and X-ray determined geometries reveal
good agreement for the seven Ir bond distances with differences
below 0.04 Å (Table S14). The complexes 10′−12′, 23′−25′,
and 31′ have orbital contributions broadly similar to FIrpic 1′
with the HOMO on iridium and phenyl (ppy) and the LUMO
on the pyridyl of the picolinate ligand (Figure 5).
(iv) Introducing a second sulfone group (complex 13) results
in a red shift in emission of 50 nm and a change in
spectral profile, compared to FIrpic. There is literature
precedent for a sulfone group inducing a red shift when
introduced at the 4-position of the phenyl ring of ppy in
a neutral iridium complex.35b
(v) Emission from the N^O bonded complexes 14 and 15 is
red-shifted by ca. 10 nm relative to their pic analogues
(10 and 11).
The photoluminescence quantum yield (PLQY) and lifetime
data are stated in Table 2. The observed lifetimes (τP = 1.49−
3.53 μs) and the spectral profiles are indicative of
phosphorescence from a mixture of ligand-centered and
MLCT excited states.17,47 The PL spectra of representative
complex 24 obtained at 80, 120, 160, 200, and 240 K in
degassed 2-MeTHF (Figure S11) show the expected
sharpening of the emission bands and a blue shift on cooling
due to reduction in vibrations. This is consistent with a
47
3
significant LC contribution to the excited state.
The thermal stabilities of the iridium complexes were
evaluated using thermogravimetric analysis under a nitrogen
atmosphere. The 5% weight loss temperatures (Td), are above
360 °C for all complexes and are comparable to FIrpic (370
°C), suggesting the complexes should be thermally stable under
device operation (Table S2).
The electrochemical properties of the complexes were
examined by cyclic voltammetry (CV) in a 0.1 M NBu4PF6
acetonitrile solution. The observed reversible oxidation waves
are assigned to the Ir(III)/Ir(IV) couple (Table 3, Figures 4
and S12). All difluoro−sulfone pic complexes (10−12) show
The lower HOMO energies on the complexes containing the
sulfonyl groups, compared to FIrpic, reflect the electron-
withdrawing properties of the former. Frontier orbital energies
are listed in Table 3 for direct comparison with observed CV
data. The observed and computed HOMO energies are in very
good agreement. The electron-donating methoxy groups in
23′−25′ increase the HOMO energies in 23′−25′ relative to
10′−12′. The electron-donating effect of the four methoxy
groups in 31′ cancels the electron-withdrawing effect of the two
Figure 4. Cyclic voltammograms for representative complexes 1, 12−
14, 24, and 31.
F
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Figure 5. Frontier molecular orbitals for 10′, 13′, and 14′. All contours are plotted at 0.05 (e/bohr3)1/2. Ir/pic or oppy/ppy % orbital contribution
ratio listed for each orbital.
sulfonyl groups; thus, 31′ has remarkably similar orbital
energies and distributions to FIrpic.
state S1, which in the presence of the iridium results in
intersystem crossing (ISC) to form the triplet excited state T1,
and phosphorescence is observed from the S0←T1 process. The
small Stokes shifts observed for most complexes suggest that
the T1 geometry is similar to the corresponding S0 geometry.
The reverse process S0←T1 is thus considered to have the same
nature as the computed S0→T1 process with the predicted
emission wavelength adjusted to take into account the Stokes
shift.
Table 4 compares the predicted S0←T1 wavelengths with
observed emission wavelengths for all iridium complexes, where
the agreement is excellent except for complexes 13′−15′. The
emissions of complexes 13−15 are likely to be from different
triplet excited-state geometries as shown in their subtly lower
PLQYs and longer lifetimes than the other iridium complexes,
The LUMOs in 10′−12′, however, do have substantial
contributions from the pyridyl groups of the ppy ligands, which
lower their orbital energies compared to FIrpic. Nevertheless,
the effect of the sulfonyl groups on the HOMO energies is
larger than on the LUMO energies in complexes 10′−12′ and
23′−25′ compared to the FIrpic frontier orbitals. Therefore,
the HOMO−LUMO energy gaps (HLGs) in these complexes
are larger than the HLG in FIrpic, and their emissions would be
more blue-shifted than FIrpic as observed experimentally.
Compound 13′ with four sulfonyl groups has a similar
HOMO as the other iridium complexes discussed above, but its
LUMO is located on the ppy ligand(s) not on the picolinate
ligand. The different LUMO is due to the four electron-
withdrawing sulfonyl groups on the ppy ligands, which would
be more easily reduced than the picolinate ligand. In 13′, the
effect of the sulfonyl groups on the LUMO energy increases;
thus, its HLG energy is closer to that of FIrpic than that of
complexes 10′−12′. While the HOMO−LUMO gap for 13 is
larger than expected, the TD-DFT prediction for 13′ (see
below) is 490 nm compared to 1′ at 471 nm. Thus, this
supports the experimental observation that the low-energy
absorption of 13 is red-shifted compared to 1.
Table 4. Iridium Atom Contributions in HOMOs and
Predicted Emission Wavelengths of Iridium Complexes
a
a
%Ir
% Ir
S0←T1, S0←T2,
observed
b
em
complex HOMO HOMO-1
nm
nm
complex
λ
, nm
max
1′
44
44
42
44
44
20
21
40
41
39
40
471
456
458
460
490
1
471
455
457
457
516
465
468
460
461
464
474
10′
11′
12′
13′
14′
15′
23′
24′
25′
31′
10
11
12
13
14
15
23
24
25
31
The HOMOs for the oppy-containing complexes, 14′ and
15′, are located at the oppy group bonded to iridium rather
than on iridium and phenyl (ppy), as is the case for the
HOMOs of the other complexes here. The different HOMOs
result in higher HOMO energies compared to 10′−12′, and
therefore 14′ and 15′ have the smallest HLG energies of all
iridium complexes calculated here. The relatively high HOMO
energies of 14′ and 15′ and different HOMOs to the other
iridium complexes are reflected in the irreversible CV waves
observed at lower oxidation potentials here. The LUMOs for
14′ and 15′ are on the ppy ligands.
c
c
c
45
38
500
503
463
467
467
473
474
472
c
a
Values from TD-DFT data on S0-optimized geometries with scaling
b
energy factor of 0.945 based on dichloromethane at 298 K. Observed
highest-energy band from emission spectra (Table 2). Observed
c
TD-DFT computations were performed on the S0-optimized
geometries of 1′, 10′−15′, 23′−25′, and 31′ to predict
emission wavelengths of these iridium complexes. The initial
excitation is assumed to give the lowest-energy singlet excited-
emission is unlikely via ISC from S1 to T1, as this ISC pathway may
not be promoted due to a smaller iridium contribution in the HOMO.
Different triplet states with higher energies are assumed to be
responsible for emissions of 14 and 15.
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Table 5. Summary of Device Luminescence and Efficiency Data
a
b
complex
λELmax, nm
brightness, cd/m2
turn-on voltage,
V
EQE, %
current efficiency, cd/A
power efficiency, lm/W
CIE coordinates, (x,y)
1
475
463
463
465
469
469
470
7340
776
6.2
6.8
8.0
8.0
8.1
6.0
8.5
5.4
3.0
3.9
4.0
3.0
3.9
3.5
12.2
2.0
8.2
7.8
5.9
7.6
6.1
5.1
0.8
2.9
2.0
2.1
3.3
1.9
(0.19, 0.38)
(0.19, 0.29)
(0.20, 0.36)
(0.18, 0.30)
(0.17, 0.33)
(0.17, 0.32)
(0.16, 0.30)
10
11
12
23
24
25
2464
2368
1772
2851
2072
a
b
Measured at a brightness of 10 cd/m2. Measured at 12 V.
Figure 6. Electroluminescence device data. Device architecture: ITO/PEDOT:PSS (45 nm)/PVK:OXD-7(35%)/Ir complex(15%)(60 nm)/TPBi
(30 nm)/LiF/Al.
1, 10−12, 23−25, and 31. In the case of 13, the larger Stokes
shift observed suggests substantial rearrangement of the
geometry in the T1 excited state. The emissions from 14 and
15 may be from different triplet excited states of higher energies
via ISC, as the HOMOs of 14′ and 15′ contain less iridium
character (Table 4), and their S1 excited states may not result in
ISC to the predicted T1 excited states.
The emission intensities for FIrpic and 15 were recorded at
different excitation wavelengths (10 nm intervals between 380
and 430 nm, Figures S8 and S9) to examine why the predicted
T1 excited-state energies for 14 and 15 differ from the observed
emission data. These measurements reveal a significant
decrease in the emission intensities for 15 compared to those
for FIrpic as the excitation wavelengths lengthen. The observed
decrease implies a different ISC pathway in 15 compared to
FIrpic and thus a different triplet excited state in 15 to the
predicted T1 state.
Optimized geometries at the T1 excited state for 10′, 13′, and
14′ were performed to examine the differences in the T1
geometries compared to their corresponding optimized S0
geometries. From T1 vertical energies on both S0 and T1
geometries, the energy differences are 0.27, 0.30, and 0.28 eV
H
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for 10′, 13′, and 14′, respectively, meaning that the T1
geometry differs (i.e., rearranges) from its S0 geometry in 13′
more than in 10′ and 14′. These energy values support the
larger Stokes shift energy observed (Table 2) for 13 compared
to the measured Stokes shift energies for all other iridium
complexes.
The spin densities at the iridium atom in the optimized T1
geometries for 10′, 13′, and 14′ are 0.36, 0.46, and 0.13,
respectively. The low spin-density value of 0.13 for 14′ suggests
that a different triplet excited state with higher energy is
responsible for the phosphorescence in 14 and, by implication,
15. The emission wavelengths in 14 and 15 would therefore be
shorter than the predicted S0←T1 emission wavelengths, as
observed experimentally. The higher spin density at the iridium
atom in the optimized T1 geometry for 13′ compared to that
for 10′ may explain the less vibronic structure emission
observed in 13 compared to that in 10. An increased vibronic
structure in the observed emission usually means an increased
ligand contribution (and decreased metal character) to the
excited state.
Phosphorescent Organic Light-Emitting Devices.
PhOLEDs were fabricated using FIrpic 1 and complexes 10−
12 and 23−25 as the dopant phosphor. Complexes 13−15 and
31 were not studied in devices as their PL spectra are red-
shifted compared to the other analogues, and our focus is on
obtaining blue devices. The device architecture comprised a
simple single-emissive-layer, which was a blend of poly-
(vinylcarbazole) (PVK) as the host material, OXD-7 (an
electron-transporting material), and the Ir complex to give the
architecture: ITO/PEDOT:PSS (45 nm)/PVK:OXD-7(35%)/
Ir complex(15%)(60 nm)/TPBi (30 nm)/LiF/Al. The emissive
layer was spin-coated from chlorobenzene solution to avoid
potential degradation of the complexes that can occur during
thermal evaporation, especially for complexes with fluorinated
ligands.32 An additional electron-transporting layer of TPBi was
incorporated adjacent to the cathode to optimize charge
balance and confine excitons in the emitter layer.49 The
efficiency and luminance data of the devices are summarized in
Table 5. The electroluminescence (EL) spectra for FIrpic 1 and
complexes 10−12 and 23−25 are shown in Figure 6a. Several
trends are apparent.
trapping. The lower efficiency for 10−12 and 23−25 is
also consistent with the known trend that a rapid decline
in efficiency is induced upon blue-shifting the emission
color.50
(4) We also note that the extent of the efficiency roll-off is
directly proportional to the current density and bright-
ness for most of the devices. Efficiency roll-off in OLED
devices has been comprehensively discussed.51
The higher efficiency, which is reproducible for complex 11
at ca. 1 mA/cm2 (Figure 5d), is typical of some OLEDs at the
device turn-on due to a slight change in material morphological
defects caused by the initial current passing through the
device.52
CONCLUSIONS
■
In summary, a series of heteroleptic Ir complexes [Ir-
(ppy)2(pic)] has been synthesized with sulfonyl substituents
attached to C3 of the phenyl ring of the ppy ligands. Compared
to the benchmark sky-blue emitter FIrpic, the additional
electron-withdrawing sulfonyl substituent results in a blue shift
of the λmax of PL and EL by up to ca. 12 nm as a result of the
increased HOMO−LUMO gap. Replacing a fluorine atom by a
methoxy group red shifts the λmax of PL and EL by ca. 4−6 nm.
Two complexes with an unusual 2-(2′-oxyphenyl)pyridyl
ancillary ligand have been obtained by an in situ nucleophilic
displacement of a fluorine substituent on a ppy ligand. (TD-
)DFT calculations are in excellent agreement with the observed
photophysical and electrochemical properties of the complexes.
PhOLEDs have been fabricated using a selection of the
complexes in a simple device architecture with a solution-
processed single-emitting layer in the configuration ITO/
PEDOT:PSS/PVK:OXD-7(35%)/Ir complex(15%)/TPBi/
LiF/Al. The EL data confirm the potential of the new
complexes to serve as blue dopants in functional devices with
a notably lower CIE Cy coordinate compared to FIrpic. The
work provides further examples where the efficiency of blue
PhOLEDs is enhanced by the presence of a mesityl substituent
on the pyridyl ring of the ppy ligands.
EXPERIMENTAL SECTION
■
(1) For all the complexes the EL and PL spectra are similar,
indicating good exciton confinement on the emissive
molecules.
Materials, Synthesis, and Characterization. All commercially
available chemicals were used without further purification. Reactions
requiring an inert atmosphere were performed under a blanket of
argon gas, which was dried over a phosphorus pentoxide column.
Anhydrous solvents were dried through an HPLC column on an
Innovative Technology Inc. solvent-purification system. Column
chromatography was performed using 40−60 μm mesh silica gel.
Analytical thin-layer chromatography (TLC) was performed on plates
precoated with silica gel (Merck, silica gel 60F254) and visualized using
UV light (254, 315, 365 nm). NMR spectra (Figures S13−S34) were
recorded on Bruker Avance 400 MHz, Varian Mercury 200 and 400
MHz, Varian Inova 500 MHz, or Varian VNMRS 600 and 700 MHz
spectrometers. Chemical shifts are referenced to tetramethylsilane
[Si(CH3)4] at 0.00 ppm. Melting points were determined in open-
ended capillaries using a Stuart Scientific SMP3 melting point
apparatus at a ramping rate of 1 °C/min. They are recorded to the
nearest 0.1 °C. Electrospray ionization (ESI) and matrix-assisted laser
desorption/ionization mass spectra were recorded on a Thermo-
Finnigan LTQ FT (7.0 T magnet) spectrometer. Atmospheric solids
analysis probe mass spectra were recorded on a Waters Xevo QTOF
spectrometer. Gas chromatography mass spectrometry (GCMS)
spectra were recorded on a Thermo-Finnigan Trace GCMS (EI and
CI ion sources). Elemental analyses were obtained on an Exeter
Analytical Inc. CE-440 elemental analyzer. HPLC was performed on
(2) The devices of 11, 12, 24, and 25 performed better than
those of 10 and 23 both in terms of external quantum
efficiency (EQE) and brightness (Figure 6c,e). For 12,
24, and 25 this can be attributed to the presence of the
mesityl group on the ppy ligands, which has been shown
previously to enhance device performance.33 The
increased solubility of 11 (p-tolylsulfonyl substituent)
compared to 10 (methylsulfonyl analogue) gave rise to
better film quality for 11, which could explain its
enhanced performance.
(3) The FIrpic devices are the most efficient in this series.
This can be explained by a superior trapping efficiency
for the FIrpic device compared to the other complexes;
the HOMO level of the PVK host is −5.8 eV, which
aligns well with FIrpic (−5.69 eV, observed; −5.49 eV,
calculated: Table 3). However, the HOMO levels of
complexes 10−12 and 23−25 are equal to that of PVK
or lower (Table 3), resulting in less efficient hole
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an analytical/semiprep Varian LC system equipped with UV−vis and
ES+ mass detectors.
Poly(3,4-ethylenedioxythiophene) doped with high work function hole
injection layer poly(styrenesulfonic acid) (PEDOT:PSS) (HIL1.3),
from CLEVIOS, was spin-coated at 2500 rpm for 60 s to produce an
∼50 nm thick hole-injecting/transporting layer (HTL). The
PEDOT:PSS layer was annealed at ca. 200 °C for 5 min to remove
any residual water. A chlorobenzene solution of 25 mg/mL of
poly(vinylcarbazole) (PVK; Mw = 90 000) was doped with 30% w/w
of (1,3-phenylene)bis[5-(4-tert-butylphenyl)-1,3,4-oxadiazole] (OXD-
7). Blended devices were made by mixing 15% w/w of the Ir
complexes. The prepared mixtures were filtered with a 0.45 μm pore
filter and spin-coated at 2500 rpm for 1 min on the top of the
PEDOT:PSS layer and baked for 10 min at 120 °C. Each sample was
shadow masked to produce four identical devices of area 4 × 5 mm;
the samples were then introduced into a nitrogen glovebox, where 30
nm of 2,2′,2″-(1,3,5-benzenetriyl)tris-[1-phenyl-1H-benzimidazole]
(TPBi) was evaporated as an electron injection/hole blocking layer
at a rate of ∼1 Å/s under vacuum at a pressure of ca. 1 × 10−6 Torr,
followed by 0.8 nm LiF and a 100 nm capping layer of aluminum
under the same evaporation conditions. Therefore, the device
configuration for all complexes was: ITO/PEDOT:PSS (50 nm)/
PVK:OXD-7 (35%)/Ir complex (15%)/TPBi (30 nm)/LiF(0.8 nm)/
Al(100 nm). All samples were encapsulated inside a glovebox using
DELO UV cured epoxy (KATIOBOND) and capped with a 1.2 × 1.2
cm microscope glass slide then exposed to UV light for 3 min.
Current−voltage data, device efficiency, brightness, and electro-
luminescence spectra were measured in a calibrated Labsphere LMS-
100 integrating sphere. A home-written NI LabVIEW program was
used to control an Agilent 6632B DC power supply, and the emission
properties of the device were measured using an Ocean Optics
USB4000 CCD fiber optic spectrometer. Thicknesses of the various
layers in the device were measured with a J. A. Woolam VASE
Ellipsometer using thin films that had been spin-coated on Si/SiO2
substrates under the same conditions as the device films.
Solution Electrochemistry and Photophysics. Cyclic voltam-
metry experiments were recorded using a BAS CV50W electro-
chemical analyzer fitted with a three-electrode system consisting of a
Pt disk (Ø = 1.8 mm) as the working electrode, a Pt wire as an
auxiliary electrode, and a Ag/AgNO3 (0.1 M[NEt4][ClO4] in
CH3CN) system as the reference electrode. Experiments were
conducted in dry acetonitrile solution with n-Bu4NPF6 (0.1 M) as
the supporting electrolyte at a scan rate of 100 mV/s. The reference
electrode was assumed to be stable and was referenced externally to
ferrocene (Cp2Fe) and decamethylferrocene (Cp*2Fe), which
displayed potentials (E1/2) of −0.41 V and +0.10 V, respectively,
versus Ag/AgNO3 under these conditions. It was not possible to use
Cp2Fe or Cp*2Fe as an internal reference because their addition to the
solutions of the complexes resulted in a distortion of the redox waves
of the complexes.
Solution-state photophysical data were obtained using freshly
prepared solutions of the complexes in dichloromethane (DCM).
Emission and lifetime measurements used thoroughly degassed
solutions achieved by three freeze−pump−thaw cycles and quartz
cuvettes with a path length of 1 cm. The solutions had absorbance
below 0.10 to minimize inner filter effects. UV−vis absorption
measurements were recorded using a Unicam UV2−100 spectrometer
operated with Unicam Vision(ver. 3.50) software. Baseline correction
was achieved by reference to pure solvent in the same cuvette.
Absorption measurements were obtained using quartz cuvettes with a
path length of 2 cm.
Excitation and emission spectra were recorded on a Jobin−Yvon−
Horiba SpexFluoromax 3 Spectrometer. Solutions of the complexes in
degassed DCM [<1 × 10−5 M] were used for decay measurements.
Samples were excited with a pulsed nitrogen laser emitting at 337.1
nm. Emission was focused onto a spectrograph and detected on a
sensitive gated iCCD camera (Stanford Computer Optics) with sub-
nanosecond resolution. Solution PLQYs were recorded in degassed
solvent and determined using the relative method, with Ir(ppy)3 (ΦPL
General Procedure for ortho Lithation Followed by Iodination.
nBuLi (1.2 equiv) was added to a stirred solution of N,N-
diisopropylamine (DIPA; 1.3 equiv) in dry tetrahydrofuran (THF)
at 0 °C, and the solution was stirred for 30 min. The temperature was
then lowered to −78 °C, and a solution of the substrate (1 equiv) in
dry THF was added in portions via cannula; the mixture was stirred for
a further 1 h. A solution of I2 (1.1−1.3 equiv) in dry THF was added
to the flask dropwise. The solution was stirred at −78 °C and allowed
to warm to room temperature (RT) overnight. The solution was then
quenched with an aqueous solution of NaS2O3 to remove unreacted
LDA and I2. The solution was then extracted with DCM (3 × 75 mL),
and the organic phases were combined, dried over MgSO4, and
filtered; the solvent was reduced in vacuo. The residue was passed
through a silica plug (eluent: DCM/ethyl acetate) to remove baseline
impurities revealed by TLC. The solvent was removed, and the crude
product was either triturated with cold hexane or purified by column
chromatography, to remove any unreacted starting material. The
product was then dried on a high vacuum line to leave the pure
product.
General Procedure for Sulfone Synthesis. The iodo compound (1
equiv), the sodium sulfinate derivative (1.6 equiv) and CuI (1.5 equiv)
were dissolved in dry dimethylformamide (DMF) and stirred under
argon. The mixture was heated at 110 °C overnight. The mixture was
cooled to RT, and water (20 mL) and DCM (20 mL) were added.
The solid was filtered off and washed with more DCM. The organic
layer was separated and dried over MgSO4, and the solvent was
removed in vacuo. The residue was purified by column chromatog-
raphy to give pure product, unless otherwise specified. This is in
accordance with the method described in the literature.38
= 0.46 in degassed dichloromethane, determined in house, vs ΦPL
=
0.546 in 0.5 M H2SO4) as the reference. The PLQYs were calculated
according to the following equation:
2
⎛
⎝
⎞
⎠
ηx
Gradx
⎜
⎜
⎟
⎟
Φ = Φ
.
x
ref Gradref
η
ref
where subscripts “x” and “ref” denote the material being measured and
the reference, respectively. Φ represents the PLQY, Grad is the
gradient from the plot of integrated fluorescence intensity versus
absorbance, and η is the refractive index of the solvent.
Computational Studies. All calculations were performed with the
Gaussian 09 package.53 All optimized S0 geometries were performed
using B3LYP54 with the pseudopotential (LANL2DZ)55 for iridium
and 3-21G* basis set for all other atoms.56 This model chemistry was
selected on the basis of related computational studies on [Ir-
57
(ppy)2Cl]2 and Ir(ppy)3.58 All S0-optimized geometries of the
most stable conformers were true minima based on no imaginary
frequencies found. Electronic structure and TD-DFT calculations were
also from the optimized geometries at B3LYP/LANL2DZ:3-21G*.
The MO diagrams and orbital contributions were generated with the
aid of Gabedit59 and GaussSum60 packages, respectively. The TD-DFT
method does not include spin−orbit couplings; thus, no oscillation
strengths for the triplet excited states are given and also does not
compute mixed singlet−triplet excited states. Optimized triplet
excited-state (T1) geometries were also performed on 10′, 13′, and
14′ to examine significant changes between their S0 and T1 geometries
to explain the differences in observed and computed emission values
for 13 and 14. Optimized triplet excited-state (T1) geometries by TD-
DFT can be considered unreliable,58 so our interpretations are based
on the assumption that these geometries are accurate.
General Procedure for Synthesis of Iridium pic Complexes.
Method A. IrCl3·3H2O (1 equiv) was added to a stirred solution of the
cyclometalating ligand (2.1−2.2 equiv) in 2-ethoxyethanol. The
mixture was heated to reflux at 130 °C under argon overnight. The
mixture was then left to cool, and the solvent was removed in vacuo.
The yellow solid, presumed to be the intermediate bis(μ-Cl) dimer
complex, was washed with cold hexane to remove any free ligand and
Phosphorescent Organic Light-Emitting Devices. PhOLEDs
were fabricated on indium tin oxide (ITO)-coated glass substrates of
thickness 125 nm and possessing a sheet resistance of 15 Ω/x.
1
dried. Where possible, the bis(μ-Cl) dimer was characterized by H
J
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NMR and mass spectrometry, although attempted purification usually
led to decomposition. The dimer was then suspended in 2-
ethoxyethanol, and picolinic acid (<3 equiv) was added. The mixture
was stirred and heated to reflux (130 °C) under argon overnight. The
mixture was allowed to cool to RT, and the solvent was removed. The
product was then purified by column chromatography to give pure
product, unless otherwise specified.
MHz; CDCl3; Me4Si) 8.77 (1H, d, J 5.0), 8.36 (1H, td, J 8.6 6.0),
7.58−7.64 (1H, m), 7.21 (1H, td, J 9.0, 1.5), 7.13−7.17 (1H, m), 6.96
(2H, d, J 1.1), 3.33 (3H, s), 2.33 (3H, s), 2.03 (6H, s); δC (101 MHz,
CDCl3, Me4Si) 159.81 (dd, J 262.6, 4.0), 157.46 (dd, J 262.0, 4.0),
156.18 (d, J 3.9), 151.00 (d, J 2.1), 150.59 (s), 150.25 (s), 137.83 (s),
137.31 (dd, J 10.8, 5.7), 135.79 (s), 135.03 (s), 128.47 (s), 125.96−
125.56 (m), 124.43 (s), 118.54 (dd, J 17.6, 15.5), 113.77 (dd, J 23.1,
3.9), 45.79 (t, J 2.4), 21.09 (s), 20.64 (s); δF (376 MHz, CDCl3,
Me4Si) −106.14 (1F, dd, J 10.2, 8.6), −111.40 (1F, d, J 11.0); HRMS
(FTMS+ESI): calcd for [C21H19F2NO2S+H]+: 388.1183. Found:
388.1170.
Method B. The reaction was conducted via a one-pot method, and
the intermediate bis(μ-Cl) dimer was not isolated.
Synthesis of Ligands and Complexes. 2-(2,4-Difluoro-3-
iodophenyl)-4-(2,4,6-trimethylphenyl)pyridine (5). The reaction
n
followed the general procedure for lithiation/iodination using BuLi
2-(2-Fluoro-3,4-di[methanesulfonyl]phenyl)pyridine (9). The re-
action followed the general procedure for sulfone synthesis using 2-
(2,4-difluoro-3-iodophenyl)pyridine 4 (which had not been rigorously
purified and was presumed to be contaminated with iodine; 1.00 g,
3.15 mmol), sodium methanesulfinate (0.515 g, 5.05 mmol), CuI
(0.90 g, 4.73 mmol), and DMF (3 mL). The reaction was worked up
as described in the general procedure, and the crude product mixture
was subjected to column chromatography (1:2 EtOAc in DCM,
(3.69 mL, 2.5 M), DIPA (1.40 mL, 9.99 mmol), 2-(2,4-
difluorophenyl)-4-(2,4,6-trimethylphenyl)pyridine 333a (2.38 g, 7.68
mmol), I2 (2.14 g, 8.43 mmol), and THF (45 mL). The mixture was
purified using a Biotage Isolera One purification system to give 5 as a
white semisolid (2.50 g, 75%); δH (400 MHz, CDCl3, Me4Si) 8.77
(1H, dd, J 5.0 0.9), 8.07 (1H, td, J 8.7 6.4), 7.59 (1H, dt, J 2.4 1.3),
7.12 (1H, dd, J 4.9 1.5), 7.05 (1H, ddd, J 8.6 6.9 1.5), 6.98 (2H, s),
2.35 (3H, s), 2.06 (6H, s); δF (376 MHz, CDCl3, Me4Si) −90.98 (1F,
q, J 5.7), −93.59, −93.67 (1F, m); δC (101 MHz, CDCl3, Me4Si) δC
(101 MHz, CDCl3, Me4Si) 161.85 (dd, J 249.4 5.4), 158.83 (dd, J
250.2, 5.9), 152.15 (d, J 3.4), 150.31, 150.07, 137.75, 136.13, 135.20,
132.31 (dd, J 9.2, 4.2), 128.50, 125.50 (d, J 9.4), 124.46 (dd, J 14.4,
3.7), 123.96, 111.94 (d, J 3.7), 111.71 (d, J 3.7), 72.01 (dd, J 30.9,
29.3), 21.16, 20.71; HRMS (FTMS+ESI): calcd for [C20H16NF2I
+H]+: 436.0374. Found: 436.0378.
2-[2,4-Difluoro-3-(methanesulfonyl)phenyl]pyridine (6). Using
the general procedure for sulfone synthesis the following reagents
were used: 2-(2,4-difluoro-3-iodophenyl)pyridine 435e (1.00 g, 3.15
mmol), sodium methanesulfinate (0.515 g, 5.05 mmol), copper iodide
(0.90 g, 4.73 mmol), and DMF (3 mL). Purification by column
chromatography (4% EtOAc in DCM, increased to 20% EtOAc in
DCM) gave a product that was recrystallized from a mixture of hexane
and DCM to give 6 as a white solid (0.133, 15%); mp 95.2−97.0 °C;
δH (400 MHz; CDCl3; Me4Si) 8.72 (1H, dt, J 4.8 1.4), 8.27 (1H, td,
8.6 6.0), 7.71−7.87 (2H, m), 7.32 (1H, ddd, J 6.7 4.8 2.1), 7.18 (1H,
td, 9.2 1.6), 3.34 (3H, s); δF (376 MHz, CDCl3, Me4Si) −106.14 (1F,
dd, J 9.3 6.2), −111.50 (1F, d, J 8.3); δC (101 MHz, CDCl3, Me4Si)
159.86 (dd, J 262.6 4.0), 157.50 (dd, J 262.6 3.9), 150.89, 150.18,
137.32 (dd, J 10.9 5.8), 136.90, 125.80 (dd, J 13.7 4.1), 124.63 (d, J
9.5), 123.42, 118.55 (dd, J 17.3 15.5), 113.80 (dd, J 23.1 4.0), 45.88 (t,
J 2.4); HRMS (FTMS+ESI): calcd for [C12H9F2NO2S+H]+:
270.03948. Found: 270.03938.
1
increased to 1:1 v/v to elute the final fraction). H NMR analysis
revealed a mixture of products. The mixture was columned for a
second time (10% EtOAc in DCM) to give two white solid products,
2-(2,4-difluoro-3-[methanesulfonyl]phenyl)pyridine 6 (135 mg, 16%;
identical with the sample above) and 2-(2-fluoro-3,4-di-
[methanesulfonyl]phenyl)pyridine 9 (115 mg, 11%); mp 194.0−
198.1 °C; δH (400 MHz; CDCl3; Me4Si) 8.78 (1H, d, J 4.7), 8.46 (1H,
dd, J 8.4 6.9), 8.28 (1H, dd, J 8.3 1.1), 7.83−7.91 (2H, m), 7.39 (1H,
td, J 4.8, 2.4), 3.58 (3H, s), 3.49 (3H, s); δF (376 MHz, CDCl3, Me4Si)
−106.57 (1F, d, J 6.9); δc (101 MHz, CDCl3, Me4Si) 159.10 (d, J
265.4), 150.49, 150.13 (d, J 1.8), 143.03, 137.01, 136.64 (d, J 5.2),
135.16 (d, J 15.3), 129.59 (d, J 14.7), 128.15 (d, J 3.5), 125.20 (d, J
9.8), 124.34, 46.27, 45.28; HRMS (FTMS+ESI): calcd for
[C13H12FNO4S2+H]+: 330.0270. Found: 330.0273.
Iridium Complex 10. The reaction followed the general procedure
for the synthesis of iridium pic complexes, Method A, using IrCl3·
2-(2,4-Difluoro-3-[(4-methylbenzene)sulfonyl]phenyl)pyridine
(7). 2-(2,4-Difluoro-3-iodophenyl)pyridine 4 (2.17 g, 6.84 mmol),
sodium p-toluenesulfinate (1.95 g, 10.94 mmol), and copper iodide
(1.95 g, 10.23 mmol) were dissolved in DMF (10 mL) and stirred
under argon. The mixture was heated at 110 °C overnight. Column
chromatography (4% EtOAc in DCM) gave a product that was
recrystallized from a hexane/DCM mixture to give 7 as white crystals
(0.62 g, 26%); 99.5−100.9 °C; δH (400 MHz; CDCl3; Me4Si) 8.67−
8.71 (1H, m), 8.18 (1H, td, J 8.6, 6.0), 7.98 (2H, d, J 8.1), 7.70−7.81
(2H, m), 7.34 (2H, d, J 8.1) 7.29 (1H, ddd, J 6.7, 4.8, 2.1), 7.10 (1H,
td, J 9.2, 1.6), 2.42 (3H, s); δF (376 MHz; CDCl3; Me4Si) −106.13
(1F, dd, J 9.3, 6.0), −111.44 (1F, d, J 8.1); δC (176 MHz; CDCl3;
Me4Si) 159.9 (dd, J 263.1, 3.8), 157.4 (dd, J 263.1, 3.5), 151.2, 150.1,
145.4, 139.1, 137.0 (dd, J 10.9, 5.7), 136.8, 130.0, 128.0, 125.6 (dd, J
13.6, 4.3), 124.8, 124.7, 123.3, 119.9 (t, J 15.9), 113.7 (dd, J 23.3, 3.8),
21.8; HRMS (FTMS+ESI): calcd for [C18H13F2NO3S+H]+: 346.0713.
Found: 346.0692. These data are consistent with the literature data for
7 prepared by a different route.35e
2-(2,4-Difluoro-3-[methanesulfonyl]phenyl)-4-(2,4,6-
trimethylphenyl)pyridine (8). The reaction followed the general
procedure for sulfone synthesis using 2-(2,4-difluoro-3-iodophenyl)-4-
(2,4,6-trimethylphenyl)pyridine 5 (657 mg, 1.51 mmol), sodium
methanesulfinate (247 mg, 2.42 mmol), CuI (431 mg, 2.26 mmol),
and DMF (3 mL). The product was purified by column
chromatography (2.5% EtOAc in DCM, increased to 10% v/v) to
give 8 as an off-white solid (130 mg, 22%); mp 74.6−77.5 °C; δH (400
3H2O (107 mg, 0.30 mmol), 2-(2,4-difluoro-3-[methanesulfonyl]-
phenyl)pyridine 6 (180 mg, 0.67 mmol), picolinic acid (154 mg, 1.25
mmol), and 2-ethoxyethanol (10 mL). Attempted purification of a
small portion of the intermediate μ-dichloro dimer resulted in rapid
decomposition under ambient conditions, so no characterization data
were obtained. Purification by column chromatography (DCM/
acetone, 1:1) gave 10 as a yellow solid (190 mg, 85%); Anal. Calcd
for C30H20F4IrN3O6S2: C, 42.35; H, 2.37; N, 4.94. Found: C, 42.17; H,
2.23; N, 4.88%; δH (700 MHz; CDCl3; Me4Si) 8.75 (1H, dt, J 5.8, 1.3,
HD6), 8.39 (1H, d, J 8.4, HB3), 8.35 (1H, d, J 7.8, HA3), 8.34 (1H, d, J
8.8, HD3), 8.04 (1H, td, J 7.8, 1.6, HA4), 7.93 (1H, td, J 6.4, 1.6, HB4),
7.91 (1H, td, J 6.4, 1.7, HD4), 7.75 (1H, dt, J 5.1, 1.4, HA6), 7.54 (1H,
ddd, J 7.8, 5.4, 1.5, HA5), 7.45 (1H, dd, J 5.7, 1.4, HB6), 7.35 (1H, ddd,
J 7.3, 5.8, 1.4, HD5), 7.14 (1H, ddd, J 7.4, 5.8, 1.4, HB5), 5.97 (1H, d, J
10.0, HE6), 5.73 (1H, d, J 10.1, HC6), 3.27 (3H, s, HE7), 3.21 (3H, s,
HC7); δF (376 MHz, CDCl3, Me4Si) −105.12 (1F, d, 9.8), −106.30
(1F, d, 10.0), −109.57 (1F, s), −110.28 (1F, s); δC (176 MHz; CDCl3;
Me4Si) 172.36 (s, CA7), 164.19 (d, J 6.8,CB2), 162.97 (d, J 6.4, CD2),
161.34 (d, J 8.1, CC2), 160.60 (d, J 8.5, CE2), 159.66 (dd, J 268.2, 2.82,
CE5), 159.19 (dd, J 266.4, 3.0, CC5), 157.54 (dd, J 271.1, 3.50, CE3),
157.33 (dd, J 270.0, 4.5, CC3), 151.11 (s, CA2), 148.89 (s, CD6), 148.41
(s, CB6), 148.32 (s, CA6), 139.58 (s, CB/D4), 139.57 (s, CB/D4), 139.46
(s, CA4), 130.10 (m, CC1), 129.92 (m, CE1), 129.18 (s, CA3/5), 129.11
K
DOI: 10.1021/acs.inorgchem.6b01179
Inorg. Chem. XXXX, XXX, XXX−XXX

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(s, CA3/5), 124.49 (d, J 21.8, CB3), 124.21 (s, CD5), 124.14 (s, CB5),
124.00 (d, J 20.6, CD3), 116.64 (d, J 19.3, CE6), 116.45 (d, J 19.1, CC6),
111.83 (t, J 16.6, CC4), 111.22 (t, J 16.5, CE4), 45.94 (s, CC7/E7), 45.90
(s, CC7/E7); HRMS (FTMS+ESI): calcd for [C30H20F4N3O6S2191Ir
+H]+: 850.0414. Found: 850.0439. Crystals for X-ray analysis were
grown by slow evaporation of a DCM solution of 10.
purified by column chromatography (DCM/acetone 1:1 v/v) to give
13 as a yellow solid (208 mg, 80%); Anal. Calcd for
C32H26F2IrN3O10S4: C, 39.58; H, 2.70; N, 4.33. Found: C, 39.42; H,
2.61; N, 4.42%; δH (400 MHz; CDCl3; Me4Si); 8.85 (1H, d, J 5.2),
8.52 (1H, d, J 8.6), 8.48 (1H, d, J 8.6), 8.36 (1H, d, J 7.5), 7.97−8.10
(3H, m), 7.70 (1H, d, J 5.2), 7.62 (1H, d, J 6.0), 7.57 (1H, t, J 6.4),
7.49 (1H, t, J 6.4), 7.29 (1H, t, J 6.6), 7.14 (1H, s), 6.83 (1H, s), 3.43
(3H, s), 3.41 (3H, s), 3.37 (3H, s), 3.36 (3H, s); δF (376 MHz, CDCl3,
Me4Si) −105.51 (1F, s), −106.32 (1F, s); HRMS (FTMS+ESI): calcd
for [C32H26F2N3O10S4191Ir+H]+: 970.0153. Found: 970.0177. Crystals
for X-ray analysis were grown by slow evaporation of a DCM/
acetonitrile solution of 13.
Iridium Complex 11. The reaction followed the general procedure
for synthesis of iridium pic complexes, Method A, using IrCl3·3H2O
(278 mg, 0.79 mmol), 2-(2,4-difluoro-3-[(4-methylbenzene)sulfonyl]-
phenyl)pyridine 7 (600 mg, 1.78 mmol), and 2-ethoxyethanol (20
mL) to give the intermediate μ-dichloro dimer as a yellow solid (700
mg, 96%); δH (400 MHz; CDCl3; Me4Si) 8.91 (4H, dd, J 6.2, 1.4),
8.35 (4H, d, J 8.5), 7.88−7.94 (4H, m), 7.83 (8H, d, J 8.1), 7.24 (8H,
d, J 8.5), 6.87 (4H, ddd, J 7.4, 5.8, 1.4), 5.24 (4H, d, J 10.6), 2.36
(12H, s); δF (376 MHz; CDCl3; Me4Si) −105.27 (4F, d, J 10.4),
−109. 88 (4F, s); HRMS (FTMS+ESI): calcd for
[C72H48Cl2F8191Ir2N4O8S4+Na2]2+: 939.0320. Found: 939.0303. The
reaction proceeded as described in the general Method A using Ir
dimer (500 mg, 0.27 mmol), picolinic acid (336 mg, 2.73 mmol), and
2-ethoxyethanol (10 mL). The reaction was worked up as previously
described, and the product was purified by column chromatography
(THF/DCM, 3:7 v/v), followed by recrystallization from DCM/
hexane to give 11 as a yellow solid (421 mg, 77%). Anal. Calcd for
C42H28F4IrN3O6S2: C 50.29; H 2.81; N 4.19. Found: C 50.03; H 2.96;
N 4.01%; δH (400 MHz; acetone-d6, Me4Si) 8.65 (1H, dt, J 5.7, 1.1),
8.37 (2H, t, J 8.3), 8.19−8.07 (4H, m), 7.94 (1H, d, J 5.2), 7.87 (4H, t,
J 7.6), 7.80 (1H, d, J 5.8), 7.62 (1H, ddd, J 6.6, 5.4, 2.6), 7.55 (1H,
ddd, J 7.4, 5.8, 1.4), 7.43−7.34 (5H, m), 6.01 (1H, d, J 10.7), 5.70 (1H,
d, J 10.6), 2.41 (3H, s), 2.40 (3H, s); δF (376 MHz; acetone-d6;
Me4Si) −107.87 (1F, dd, J 10.7, 4.1), −108.61 (1F, dd, J 10.6, 3.6),
−110.89 (1F, s), −111.59 (1F, s); HRMS (FTMS+ESI): calcd for
[C42H28O6N3F4191IrS2+Na]+: 1026.0883. Found: 1026.0870. These
data are consistent with the literature data for 11 prepared by a
different route.35e Crystals for X-ray analysis were grown by slow
evaporation of a DCM/hexane solution of 11.
Iridium Complex 12. The reaction followed the general procedure
for synthesis of iridium pic complexes, Method A, using IrCl3·3H2O
(40 mg, 0.11 mmol), 2-(2,4-difluoro-3-[methanesulfonyl]phenyl)-4-
(2,4,6-trimethylphenyl)pyridine 8 (90 mg, 0.232 mmol), and 2-
ethoxyethanol (6 mL) to give the intermediate μ-dichloro dimer as a
yellow solid. The NMR spectra were consistent with the dimer
structure: δH (400 MHz; CDCl3; Me4Si) 9.52 (4H, d, J 5.9), 8.23 (4H,
s), 6.97−7.05 (12H, m), 5.34 (4H, d, J 10.8), 3.18 (3H, s), 2.40 (3H,
s), 2.11 (3H, s), 2.07 (3H, s); δF (376 MHz, CDCl3, Me4Si) −105.73
(4F, d, J 12.0), −110.17 (4F, s). The reaction was continued as
described in the general Method A using Ir dimer, picolinic acid (90
mg, 0.731 mmol), and 2-ethoxyethanol (6 mL). The product was
purified by column chromatography (EtOAc/DCM 3:7 v/v) to afford
Ir complex 12 as a yellow solid (105 mg, 85%); Anal. Calcd for
C48H40F4IrN3O6S2·0.5CH2Cl2: C, 51.57; H, 3.66; N, 3.72. Found: C,
51.32; H, 3.62; N, 3.69%; δH (400 MHz; CDCl3; Me4Si) 8.82 (1H, dd,
J 6.0 0.7), 8.40−8.48 (1H, m), 8.21 (1H, t, J 1.7), 8.15 (1H, t, J 1.7),
8.09 (1H, td, J 7.8 1.6), 7.89 (1H, ddd, J 5.4 1.6 0.8), 7.60 (1H, ddd, J
7.8 5.3 1.5), 7.50 (1H, dd, J 6.0 0.7), 7.21 (1H, dd, J 5.9 1.7), 6.95−
7.04 (5H, m), 5.94 (1H, d, J 10.3), 5.73 (1H, d, J 10.4), 3.25 (3H, s),
3.20 (3H, s), 2.35 (6H, s), 2.12 (3H, s), 2.09 (6H, s), 1.96 (3H, s); δF
(376 MHz, CDCl3, Me4Si) −105.58 (1F, dd, J 10.9 3.5), −106.77 (1F,
dd, J 11.4 3.3), −109.82 (1F, d, J 4.1), −110.61; HRMS (FTMS+ESI):
calcd for [C48H40F4N3O6S2191Ir + H]+: 1086.1979. Found: 1086.1978.
Crystals for X-ray analysis were grown by slow evaporation of a DCM/
hexane solution of 12.
Iridium Complex 14. IrCl3·3H2O (69 mg, 0.20 mmol) was added to
a stirred solution of 2-(2,4-difluoro-3-[methanesulfonyl]phenyl)-
pyridine 6 (116 mg, 0.67 mmol) in 2-ethoxyethanol (8 mL). The
mixture was heated to reflux at 130 °C under argon overnight. The
mixture was then left to cool, and the solvent was removed in vacuo to
give a yellow solid, presumed to be the bis(μ-Cl) dimer, which was
used without further purification. The dimer was dissolved in ethylene
glycol (8 mL), and 2-(2,4-difluoro-3-[methanesulfonyl]phenyl)-
pyridine 6 (58 mg, 0.22 mmol), NEt3 (0.1 mL), and acetylacetone
(0.1 mL) were added. The mixture was stirred under argon and heated
to reflux at 190 °C overnight. The mixture was then left to cool. DCM
(25 mL) and water (25 mL) were added, and the organic layer was
separated and washed with water (2 × 60 mL) to remove most of the
ethylene glycol. The solvent was removed in vacuo to leave a brown
liquid residue, which was washed with water (5 mL) to remove any
residual ethylene glycol. The residue was then purified by column
chromatography (DCM/methanol 29:1 followed by DCM/EtOAc 4:1
v/v) to give iridium complex 14 as a yellow solid (56 mg, 29%); δH
(700 MHz; CD2Cl2; Me4Si) 9.03 (1H, ddd, J 5.7, 1.7, 0.8, HA6), 8.49
(1H, d, J 8.5, HA3), 8.27 (1H, d, J 8.5, HC3), 8.10 (1H, ddd, J 5.7, 1.7,
0.8, HC6), 8.00 (1H, td, J 8.0, 7.4, 1.6, HA4), 7.85 (1H, ddd, J 8.2, 7.4,
1.7, HE4), 7.82 (1H, ddd, J 8.4, 7.6, 1.6, HC4), 7.73 (1H, dd, J 8.0, 1.1,
HE3), 7.52 (1H, dd, J 8.8, 6.0, HF3), 7.47 (1H, ddd, J 5.7, 1.7, 0.8, HE6),
7.35 (1H, ddd, J 7.3, 5.7, 1.4, HA5), 6.98 (1H, ddd, J 7.4, 5.8, 1.4, HC5),
6.96 (1H, ddd, J 7.4, 5.8, 1.4, HE5), 6.33 (1H, dd, J 10.6, 8.8, HF4), 5.93
(1H, d, J 10.5, HB6), 5.71 (1H, d, J 10.5, HD6), 3.20 (3H, s, HB/D7),
3.19 (3H, s, HB/D7), 2.74 (3H, s, HF7); δF (376 MHz, CDCl3, Me4Si)
−105.39 (1F, dd, J 10.1, 6.2), −105.70 (1F, dd, J 10.1, 2.8), −106.70
(1F, dd, J 9.9, 2.6), −109.10 (1F, s), −109.94 (1F, s); δC (176 MHz,
CDCl3, Me4Si) 167.68 (CF1), 163.85 (CC2), 162.72 (CA2), 162.45
(CF5), 159.03 (CB5, J 262.5), 158.33 (CD5, J 272.9), 155.38 (CE2),
150.91 (CC6), 150.41 (CE6), 149.08 (CA6), 139.94 (CA4), 139.68
(CC4), 139. 53 (CE4), 136.07 (CF3), 131.78 (CD1), 130.56 (CB1),
125.92 (CE3), 125.71 (CF2), 124.98 (C A3), 124.51 (CC3), 124.26
(CA5), 123.82 (CE5), 123.19 (CC5), 120.95 (CF6), 117.23 (CB6, d, J
18.1), 116.46 (CD6, d, J 17.8), 104.60 (CF4, d, J 24.1), 46.33 (CB+D7),
45.49 (CF7); HRMS (FTMS+ESI): calcd for [C36H25F5N3O7S3191Ir
+H]+: 994.0459. Found: 994.0478.
Iridium Complex 13. The reaction followed the general procedure
for synthesis of iridium pic complexes, Method A, using IrCl3·3H2O
(94 mg, 0.27 mmol), 2-(2-fluoro-3,4-bis(methylsulfonyl)phenyl)-
pyridine 9 (194 mg, 0.59 mmol), and 2-ethoxyethanol (8 mL) to
give an orange-yellow solid presumed to be the bis(μ-Cl) dimer, which
was used without further purification. Because of its very poor
solubility NMR data could not be obtained. The reaction was
continued as described in the general Method A using picolinic acid
(245 mg, 1.99 mmol) and 2-ethoxyethanol (8 mL). The product was
Iridium Complex 15. IrCl3·3H2O (136 mg, 0.39 mmol) was added
to a stirred solution of 2-(2,4-difluoro-3-[(4-methylbenzene)sulfonyl]-
phenyl)pyridine 7 (293 mg, 0.85 mmol) in 2-ethoxyethanol (10 mL).
The mixture was heated to reflux at 130 °C under argon overnight.
The mixture was then left to cool, and the solvent was removed in
vacuo to leave a yellow solid, presumed to be the bis(μ-Cl) dimer,
which was used without further purification. The dimer was dissolved
in ethylene glycol (8 mL), and the 2-(2,4-difluoro-3-[(4-
L
DOI: 10.1021/acs.inorgchem.6b01179
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methylbenzene)sulfonyl]phenyl)pyridine 7 (130 mg, 0.38 mmol),
NEt3 (0.1 mL), and acetylacetone (0.1 mL) were added. The reaction
procedure and workup as described for 14 gave iridium complex 15 as
a yellow solid (110 mg, 23%); Anal. Calcd for C54H37N3F5O7S3Ir: C,
53.11; H, 2.89; N, 3.44. Found: C, 52.64; H, 2.89; N, 3.37%; δH (400
MHz; CDCl3; Me4Si) 8.36 (1H, d, J 8.5), 8.25 (1H, d, J 8.5), 7.93
(3H, dd, J 6.3, 1.8), 7.89−7.78 (4H, m), 7.71 (2H, tdd, J 8.1, 6.2, 1.7),
7.62−7.55 (1H, m), 7.42 (1H, dd, J 8.9, 6.0), 7.36−7.26 (3H, m),
7.15−7.05 (2H, m), 6.99−6.91 (2H, m), 6.91−6.76 (5H, m), 6.28
(1H, dd, J 10.4, 8.8), 5.92 (1H, d, J 10.3), 5.40 (1H, d, J 10.6), 2.41
(3H, s), 2.37 (3H, s), 2.19 (3H, s); δF (376 MHz; CDCl3; Me4Si)
−105.11, −105.21 (2F, m), −108.21 (1F, dd, J 10.7, 3.1), −108.35
(1F, d, J 4.3), −108.90, −108.97 (1F, m); HRMS (FTMS+ESI): calcd
for [C54H37F5N3O7S3191Ir+H]+: 1222.13925. Found: 1222.13928.
Crystals for X-ray analysis were grown by slow evaporation of a
solution of 15 in DCM/hexane/MeOH (1:2:1 v/v) at RT.
1.5), 7.98 (1H, t, J 8.8), 7.71−7.78 (2H, m), 7.19−7.28 (1H, m), 6.76
(1H, dd, J 8.8, 1.2), 3.96 (3H, s); δF (376 MHz; CDCl3; Me4Si)
−93.14 (d, J 10.7); δC (101 MHz; CDCl3 Me4Si) 160.09 (d, J 248.0),
160.33 (d, J 6.1), 152.82 (d, J 3.3), 149.79, 136.62, 131.84 (d, J 4.8),
124.23 (d, J 9.6), 122.33, 121.25 (d, J 14.9), 106.97 (d, J 2.9), 75.06 (d,
J 28.96), 57.02; HRMS (FTMS+ESI): calcd for [C12H9NFOI+H]+:
329.9791. Found: 329.9787.
2-(2-Fluoro-3-iodo-4-methoxyphenyl)-4-(2,4,6-trimethylphenyl)-
pyridine (19). The general procedure for lithiation followed by
n
iodination used BuLi (2.1 mL, 2.5 M), DIPA (0.81 mL, 5.78 mmol),
2-(2-fluoro-4-methoxyphenyl)-4-mesitylpyridine 17 (1.35 g, 4.20
mmol), I2 (1.49 g, 8.09 mmol), and THF (30 mL, dry). The reaction
was worked up as described in the general method, and the product
was then purified by column chromatography (hexane/EtOAc 2:1) to
give an off-white solid, 2-(2-fluoro-3-iodo-4-methoxyphenyl)-4-mesti-
tylpyridine) 19 (1.03 g, 55%); mp 167.4−168.5 °C; δH (400 MHz;
CDCl3; Me4Si) 8.73 (1H, dd, J 5.0, 0.9), 8.05 (1H, t, J 8.8), 7.54−7.61
(1H, m), 7.06 (1H, dd, J 5.0, 1.5), 6.96 (2H, s), 6.78 (1H, dd, J 8.8,
1.1), 3.97 (3H, s), 2.34 (3H, s), 2.05 (6H, s); δF (376 MHz, CDCl3,
Me4Si) −92.81 (d, J 12.6); δC (101 MHz; CDCl3; Me4Si) 159.98 (d, J
248.3), 160.21 (d, J 6.1), 152.81 (d, J 3.3), 150.05, 149.76, 137.55,
136.27, 135.17, 131.73 (d, J 4.9), 128.34, 125.21 (d, J 9.7), 123.27,
121.17 (d, J 14.5), 106.83 (d, J 2.9), 74.96, 56.88, 21.05, 20.62; HRMS
(FTMS+ESI): calcd for [C21H19NFOI+H]+: 448.0574. Found:
448.0565.
2-(2-Fluoro-4-methoxy-3-(methylsulfonyl)phenyl)pyridine (20).
The reaction followed the general procedure for sulfone synthesis
using 2-(2-fluoro-3-iodo-4-methoxyphenyl)-pyridine) 18 (1.02 g, 3.11
mmol), CuI (0.89 g, 4.67 mmol), and MeSO2Na (0.51 g, 4.98 mmol)
in DMF (2.5 mL). The product was purified by column
chromatography (DCM/EtOAc 1:1 v/v) to give 2-(2-fluoro-4-
methoxy-3-(methylsulfonyl)phenyl)pyridine 20 (390 mg, 45%); δH
(400 MHz; CDCl3; Me4Si) 8.70 (1H, dt, J 4.8, 1.4), 8.23 (1H, dd, J
9.0, 8.3), 7.72−7.82 (2H, m), 7.26−7.30 (1H, m), 6.98 (1H, dd, J 8.9,
1.3), 4.03 (3H, s), 3.34 (3H, s); δF (376 MHz; CDCl3; Me4Si)
−113.56 (d, J 9.3); δC (176 MHz; CDCl3; Me4Si) 159.07 (d, J 3.4),
158.4 (d, J 263.2), 151.87 (d, J 1.7), 149.96, 136.87 (d, J 6.1), 136.72,
124.60 (d, J 9.8), 122.80, 122.20 (d, J 14.3), 118.01 (d, J 13.6), 108.66
(d, J 3.5), 57.28, 45.61; HRMS (FTMS+ESI): calcd for
[C13H12NFO3S+H]+: 282.0600. Found: 282.0615.
2-(2-Fluoro-4-methoxy-3-[methylsulfonyl]phenyl)-4-(2,4,6-
trimethylphenyl)pyridine (21). The reaction followed the general
procedure for sulfone synthesis using 2-(2-fluoro-3-iodo-4-methox-
yphenyl)-4-mestitylpyridine) 19 (1.00 g, 2.24 mmol), CuI (0.68 g,
3.58 mmol), MeSO2Na (0.34 g, 3.35 mmol), and DMF (3.5 mL, dry).
The reaction was worked up as described in the general procedure,
and the product was purified by column chromatography (DCM/
EtOAc 1:1) to give 2-(2-fluoro-4-methoxy-3-(methylsulfonyl)phenyl)-
4-mesitylpyridine 21 (470 mg, 53%); mp 169.2−170.8 °C; (400 MHz;
CDCl3; Me4Si) 8.74 (1H, d, J 5.0), 8.30 (1H, t, J 8.6), 7.57−7.63 (1H,
m), 7.10 (1H, dd, J 5.0, 1.5), 7.00 (1H, dd, J 9.0, 1.2), 6.92−6.97 (2H,
m), 4.05 (3H, s), 3.32 (3H, s), 2.33 (3H, s), 2.03 (6H, s); δF (376
MHz; CDCl3; Me4Si) −113.44 (d, J 9.5); δC (176 MHz; CDCl3;
Me4Si) 159.09 (d, J 3.3), 158.49 (d, J 263.0), 152.00, 150.46, 150.07,
137.77, 136.91 (d, J 5.9), 136.11, 135.17, 128.49, 125.72 (d, J 8.9),
123.89, 122.24 (d, J 14.0), 118.06 (d, J 13.3), 108.68 (d, J 3.4), 57.29,
45.61, 21.18, 20.74; HRMS (FTMS+ESI): calcd for [C22H22NFO3S
+H]+: 400.1383. Found: 400.1379.
2-(2-Fluoro-4-methoxy-3-(p-toluenesulfonyl)phenyl)-4-mesityl-
pyridine (22). The reaction followed the general procedure for sulfone
synthesis using 2-(2-fluoro-3-iodo-4-methoxyphenyl)-4-mesitylpyri-
dine 19 (0.81 g, 1.81 mmol), sodium p-tolylsulfinate (0.52 g, 2.90
mmol), CuI (0.52 g, 2.71 mmol), and DMF (3 mL). The product was
purified by column chromatography (5% EtOAc in DCM, increased to
20%) to give 2-(2-fluoro-4-methoxy-3-(p-toluenesulfonyl)phenyl)-4-
mesitylpyridine 22 as an off white solid (0.17 g, 21%); δH (400 MHz;
CDCl3; Me4Si) 8.73 (1H, dd, J 5.0, 0.9), 8.22 (1H, dd, J 8.9, 8.2),
7.88−7.98 (2H, m), 7.56−7.66 (1H, m), 7.26−7.33 (2H, m), 7.08
(1H, dd, J 5.0, 1.5), 6.94−6.99 (2H, m), 6.87 (1H, dd, J 9.0, 1.2), 3.85
(3H, s), 2.41 (3H, s), 2.34 (3H, s) 2.04 (6H, s); δF (376 MHz; CDCl3;
2-(2-Fluoro-4-methoxyphenyl)-pyridine) (16). A solution of 2-
fluoro-4-methoxyphenylboronic acid (1.00 g, 5.88 mmol) and 2-
bromopyridine (0.62 mL, 6.46 mmol) in dioxane (30 mL) was
degassed by bubbling argon for 30 min. An aqueous solution of
Na2CO3 (0.79 g, 7.44 mmol in 4 mL) was added, followed by
Pd(PPh3)4 (70 mg, 0.06 mmol). The mixture was heated to 95 °C
overnight under argon, then allowed to cool, and the solvent was
removed in vacuo. Water and DCM were added, and the organic layer
was separated. The aqueous layer was extracted with more DCM,
dried over MgSO4, and the solvent was removed in vacuo. The crude
oil was purified by distillation using a Kuglerohr apparatus. Residual 2-
bromopyridine distilled first (70−80 °C, 0.75 mbar), followed at 115
°C, 0.75 mbar by 2-(2-fluoro-4-methoxyphenyl)-pyridine) 16 as a pale
yellow oil (1.09 g, 91%); δH (400 MHz; CDCl3; Me4Si) 8.68 (1H,
ddd, J 4.8, 1.8, 1.0), 7.95 (1H, t, J 9.0), 7.67−7.77 (2H, m), 7.18 (1H,
ddd, J 7.0, 4.9, 1.5), 6.81 (1H, ddd, J 8.8, 2.5, 0.7), 6.69 (1H, dd, J 13.2,
2.5), 3.83 (3H,s); δF (376 MHz, CDCl3, Me4Si) −114.74 (1F, t, J
12.3); δC (101 MHz; CDCl3; Me4Si) 161.47 (d, JC−F 11.2), 161.32 (d,
JC−F 249.5), 153.43 (d, JC−F 2.8), 149.68 (s), 136.40 (s), 131.63 (d,
JC−F 4.9), 124.03 (d, JC−F 9.8), 121.85 (s), 120.01 (d, JC−F 11.9),
110.65 (d, JC−F 2.9), 102.00 (d, JC−F 27.0), 55.72 (s); HRMS (FTMS
+ESI): calcd for [C12H10NFO+H]+: 204.0825. Found: 204.0817.
2-(2-Fluoro-4-methoxyphenyl)-4-mesitylpyridine (17). A solution
of 2-chloro-4-(2,4,6-trimethylphenyl)pyridine33a (1.23 g, 5.31 mmol),
2-fluoro-4-methoxyphenylboronic acid (1.00 g, 5.88 mmol),
palladium(II) acetate (73 mg, 0.36 mmol), and triphenylphosphine
(363 mg, 1.52 mmol) in 1,2-dimethoxyethane (DME; 60 mL) was
degassed with argon for 30 min. A 2 M aqueous solution of sodium
carbonate (11 mL, 2.31 g, 24.01 mmol) was degassed for 25 min. The
solutions were combined, and the mixture was heated to reflux (105
°C) under argon for 24 h. The reaction mixture was then cooled to
RT, and the DME was removed in vacuo. DCM (50 mL) was then
added, followed by brine (50 mL). The organic layer was separated
and dried over MgSO4. The solvent was removed in vacuo, and the
residue was purified by column chromatography (EtOAc/hexane 1:5
v/v) to give 2-(2-fluoro-4-methoxyphenyl)-4-mesitylpyridine 17 as a
yellow oil (1.35 g, 78%); δH (400 MHz; CDCl3; Me4Si) 8.73 (1H, dd,
J 4.9, 0.9), 8.02 (1H, t, J 9.0), 7.55−7.61 (1H, m), 7.03 (1H, dd, J 5.0,
1.5), 6.94−6.99 (2H, m), 6.84 (1H, ddd, J 8.8, 2.5, 0.7), 6.69 (1H, dd,
J 13.1, 2.5), 3.85 (3H, s), 2.34 (3H, s), 2.05 (6H, s); δF (376 MHz,
CDCl3, Me4Si) −114.38 (1F, t, J 13.2); δC (101 MHz; CDCl3; Me4Si)
161.28 (d, J 250.1), 161.41 (d, J 11.4), 153.50 (d, J 2.8), 149.79 (s),
149.69 (s), 137.48 (s), 136.51 (s), 135.28 (s), 131.59 (d, J 4.8), 128.33
(s), 125.00 (d, J 9.8), 122.86 (s), 119.95 (d, J 11.6), 110.58 (d, J 3.0),
101.93 (d, J 27.2), 55.67 (s), 21.05 (s), 20.62 (s); HRMS (FTMS
+ESI): calcd for [C21H20FNO+H]+: 322.1607. Found: 322.1608.
2-(2-Fluoro-3-iodo-4-(methoxyphenyl)-pyridine) (18). The reac-
tion used the general procedure for lithiation followed by iodination
n
using BuLi (1.94 mL, 2.5 M), DIPA (0.75 mL, 5.34 mmol), 2-(2-
fluoro-4-methoxyphenyl)-pyridine) 16 (790 mg, 3.89 mmol), I2 (1.38
g, 5.44 mmol), and THF (35 mL). Purification by column
chromatography (hexane/EtOAc 3:2 v/v) gave 2-(2-fluoro-3-iodo-4-
methoxyphenyl)-pyridine) 18 (746 mg, 58%) as an off-white solid; mp
107.2−109.7 °C; δH (400 MHz; CDCl3 Me4Si) 8.69 (1H, dt, J 4.8,
M
DOI: 10.1021/acs.inorgchem.6b01179
Inorg. Chem. XXXX, XXX, XXX−XXX

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Article
Me4Si) −112.69 (1F, d, J 10.9); δC (101 MHz; CDCl3; Me4Si) 158.40
(d, J 263.0), 158.98 (d, J 3.3), 152.10 (d, J 1.8), 150.26, 149.88, 144.17,
139.92, 137.63, 136.68 (d, J 6.1), 136.05, 135.10, 129.26, 128.36,
127.82, 125.62 (d, J 9.9), 123.64, 121.78 (d, J 14.2), 118.64 (d, J 13.4),
108.61 (d, J 3.6), 56.77, 21.65, 21.07, 20.64; HRMS (FTMS+ESI):
calcd for [C28H26NFO3S+H]+: 476.1696. Found: 476.1718.
3H2O (72 mg, 0.20 mmol), 2-(2-fluoro-4-methoxy-3-(p-
toluenesulfonyl)phenyl)-4-mesitylpyridine 22 (184 mg, 0.42 mmol),
picolinic acid (37 mg, 0.30 mmol), and 2-ethoxyethanol (5 mL). The
product was purified initially by column chromatography (EtOAc in
DCM 1:4, increased to 1:3 v/v) to give a yellow solid, which was
further purified by recrystallization from ethanol to give complex 25
(210 mg, 83%); Anal. Calcd for C62H54N3F2O8S2Ir: C, 58.94; H, 4.31;
N, 3.33. Found: C, 58.60; H, 4.26; N, 3.27%; δH (400 MHz; CDCl3;
Me4Si) 8.74 (1H, d, J 5.8), 8.39 (1H, d, J 7.8), 8.15 (1H, s), 8.08 (1H,
s), 8.04 (1H, td, J 7.7, 1.6), 7.85−7.90 (2H, m) 7.77−7.85 (3H, m),
7.56 (1H, ddd, J 7.4, 5.3, 1.1), 7.40 (1H, d, J 5.9), 7.30−7.20 (4H, m),
7.03−6.92 (5H, m), 6.81 (1H, dd, J 5.9, 1.8), 5.71 (1H, s), 5.63 (1H,
s), 3.43 (3H, s), 3.37 (3H, s), 2.38 (6H, s), 2.34 (6H, s), 2.08 (3H, s),
2.00 (3H, s), 1.96 (3H, s), 1.94 (3H, s); δF (376 MHz; CDCl3; Me4Si)
−110.60 (1F, s), −111.33 (1F, s); HRMS (FTMS+ESI): calcd for
[C62H54N3F2O8S2191Ir+H]+: 1262.3005. Found: 1262.3020.
Iridium Complex 23. The reaction followed the general procedure
for the synthesis of iridium pic complexes, Method B, using IrCl3·
(2,4-Dimethoxy-3-(methylthio)phenyl)boronic Acid 27. nBuLi
(11.25 mL, 2.5 M in hexanes) was added dropwise to a stirred
solution of 3-bromo-2,6-dimethoxythioanisole 2642 (6.17 g, 23.45
mmol) in THF (15 mL, dry) at −78 °C. The mixture was stirred at
−78 °C for 1 h. Triisopropylborate (8.11 mL, 35.15 mmol) was slowly
added, and the reaction mixture was stirred at −78 °C for 1 h before
being left to warm to RT overnight. Dilute HCl was added, and the
solution was extracted with EtOAc. The solvent was removed in vacuo
to leave a sticky brown solid, which was redissolved in EtOAc and was
extracted with aqueous KOH (150 mL). The aqueous layer was
acidified to pH 5 with dilute HCl and extracted with EtOAc. The
solvent was removed in vacuo to give a beige solid, (2,4-dimethoxy-3-
(methylthio)phenyl)boronic acid 27 (2.80 g, 52%); δH (400 MHz;
CDCl3; Me4Si) 7.80 (1H, d, J 8.4), 6.79 (1H, d, J 8.4), 5.88 (2H, br s),
3.98 (3H, s), 3.97 (3H, s), 2.42 (3H, s); δB (128 MHz; CDCl3; Me4Si)
28.66 (1B, br s); HRMS (FTMS+ESI): calcd for [C9H13O4S10B+H]+:
228.0742. Found: 228.0732.
2-(2,4-Dimethoxy-3-(methylthio)phenyl)-4-mesitylpyridine 28. 2-
Chloro-4-mesitylpyridine (0.72 g, 3.11 mmol), (2,4-dimethoxy-3-
(methylthio)phenyl)boronic acid 27 (0.85 g, 3.73 mmol), and PPh3
(211 mg, 0.80 mmol) were dissolved in DME (50 mL), and the
solution was degassed for 20 min by bubbling with argon. An aqueous
solution of Na2CO3 (1.34 g, 12.64 mmol in 10 mL) was degassed for
20 min. The solutions were combined, and Pd(OAc)2 (43 mg, 0.19
mmol) was added. The mixture was heated to reflux for 24 h before
being cooled. The solvent was removed under reduced pressure, and
DCM and water were added. The organic layer was separated, and the
aqueous layer was extracted with further DCM. The extracts were
combined, and the solvent was removed. The residue was purified by
column chromatography (DCM/EtOAc 1:1 v/v) to give a white solid,
2-(2,4-dimethoxy-3-(methylthio)phenyl)-4-mesitylpyridine 28 (0.70 g,
60%); mp 133.4−136.2; δH (400 MHz; CD3OD; Me4Si) 8.65 (1H, dd,
J 5.1, 0.9), 7.62 (1H, d, J 8.6), 7.58−7.52 (1H, m), 7.16 (1H, dd, J 5.1,
1.6), 6.97 (2H, s), 6.97 (1H, d, J 8.7), 3.94 (3 H, s), 3.57 (3 H, s), 2.39
(3H, s), 2.31 (3H, s), 2.05 (6H, s); δC 13C NMR (101 MHz, CD3OD;
Me4Si) 161.38, 159.22, 156.10, 150.69, 148.72, 137.40, 136.03, 134.50,
130.81, 127.99, 126.57, 126.07, 123.18, 119.02, 107.31, 99.99, 19.73,
19.34, 16.60; HRMS (FTMS+ESI): calcd for [C23H25NFO2S+H]+:
380.1684. Found: 380.1666.
3H2O (233 mg, 0.66 mmol), 2-(2-fluoro-4-methoxy-3-
(methylsulfonyl)phenyl)pyridine 20 (390 mg, 1.39 mmol), picolinic
acid (284 mg, 2.31 mmol), and 2-ethoxyethanol (12 mL). Purification
by column chromatography (5% MeOH in DCM) gave a yellow solid,
which was suspended in ethanol and heated to reflux. The solution was
filtered to afford complex 23 as a yellow solid (310 mg, 54%); Anal.
Calcd for C32H26N3F2O8S2Ir: C, 43.93; H, 3.00; N, 4.80. Found: C,
44.02; H, 3.26; N, 4.97%; δH (700 MHz; CDCl3; Me4Si) 8.78 (1H,
ddd, J 5.8, 1.7, 0.8, HA6), 8.37 (1H, ddd, J 7.8, 1.5, 0.8, HE3), 8.34 (1H,
d, J 8.5, HB3), 8.27 (1H, d, J 8.5, HA3), 8.02 (1H, td, J 7.8, 1.6, HE4),
7.84 (1H, td, HB4) 7.82 (1H, td, J, HA4), 7.79 (1H, ddd, J, HE6), 7.52
(1H, ddd, J 7.7, 5.4, 1.5, HE5), 7.46 (1H, ddd, J 5.9, 1.6, 0.8, HB6), 7.23
(1H, ddd, J 7.3, 5.8, 1.4, HA5), 7.03 (1H, ddd, J 7.4, 5.8, 1.4, HB5), 5.73
(1H, s, HC6), 5.57 (1H, s, HD6), 3.56 (3H, s, HC8), 3.51 (3H, s, HD8),
3.25 (3H, s, HC7), 3.20 (3H, s, HD7); δF (376 MHz; CDCl3; Me4Si)
−112.10 (1F, s), −112.58 (1F, s); δC (176 MHz; CDCl3; Me4Si)
172.31 (s, CE7), 165.37 (d, J 6.2, CB2), 164.21 (d, J 6.2, CA2), 161.38
(CC/D2), 160.56 (CC/D2), 158.69 (d, J 3.0, CC5), 158.40 (d, J 284.0,
CC3), 158.30 (d, J 284.0, CD3), 158.18 (d, J 2.6, CD5), 151.18 (s, CE2),
148.64 (s, CA6), 148.26 (s, CE6), 148.00 (s, CB6), 138.90(s, CE4),
138.73 (s, CA/B4), 138.70 (s, CA/B4), 128.81 (s, CE3), 128.78 (s, CE5),
126.12 (d, J,CC1), 125.81 (d, CD1), 123.53 (d, J, CB3), 122.96 (d, J,
CA3), 122.41 (s, CB5), 122.35 (s, CA5), 111.28 (d, J 11.4, CD4), 111.01
(CD6), 110.93 (d, J 11.5, CC4), 110.73 (CC6), 56.09 (s, CC8), 55.97 (s,
CD8), 45.29 (s, CC/D7), 45.28 (s, CC/D7); HRMS (FTMS+ESI): calcd
for [C32H26N3F2O8S2191Ir+H]+: 874.0814. Found: 874.0786. Crystals
for X-ray analysis were grown by slow vapor diffusion of pentane into a
solution of 23 in DCM.
Iridium Complex 24. The reaction followed the general procedure
for the synthesis of iridium pic complexes, Method B, using IrCl3·
3H2O (189 mg, 0.54 mmol), 2-(2-fluoro-4-methoxy-3-
(methylsulfonyl)phenyl)-4-mesitylpyridine 21 (450 mg, 1.13 mmol),
picolinic acid (231 mg, 1.88 mmol), and 2-ethoxyethanol (20 mL).
The reaction was worked up as described in the general procedure,
and the residue was purified by column chromatography (5% MeOH
in DCM). The yellow solid was suspended in ethanol and heated to
reflux. The solution was filtered hot to afford Ir complex 24 as a yellow
solid (420 mg, 70%). Anal. Calcd for C50H46N3F2O8S2Ir·CH2Cl2: C,
51.21; H, 4.04; N, 3.51. Found: C, 51.34; H, 3.99; N, 3.55%; δH (400
MHz; CDCl3; Me4Si) 8.80−8.87 (m, 1H), 8.44 (1H, dt, J 7.8, 0.9),
8.19 (1H, s), 8.12 (1H, s), 8.07 (1H, td, J 7.7, 1.5), 7.88 (1H, dt, J 5.1,
1.3), 7.57 (1H, ddd, J 7.6, 5.3, 1.5), 7.45 (1H, d, J 5.9), 7.09 (1H, dd, J
5.9, 1.8), 6.93−7.02 (4H, m), 6.87 (1H, dd, J 5.9, 1.8), 5.83 (1H, s),
5.77 (1H, s), 3.61 (3H, s), 3.58 (3H, s), 3.23 (3H, s), 3.19 (3H, s),
2.34 (6H, s), 2.09 (3H, s), 2.05 (3H, s), 2.00 (3H, s), 1.95 (3H, s); δF
(376 MHz; CDCl3; Me4Si) −111.68 (s), −112.28 (s); HRMS (FTMS
+ESI): calcd for [C50H46N3F2O8S2191Ir+H]+: 1110.2379. Found:
1110.2393.
2-(2,4-Dimethoxy-3-(methylthio)phenyl)-4-mesitylpyridinium
Chloride 29. HCl (0.05 mL, 12 M) was added to a stirred solution of
2-(2,4-dimethoxy-3-(methylthio)phenyl)-4-mesitylpyridine 28 (236
mg, 0.62 mmol) in DCM/MeOH (40 mL, 1:1), and the mixture
was stirred at RT overnight. The solvent was removed in vacuo to
leave the product as a white solid, 2-(2,4-dimethoxy-3-(methylthio)-
phenyl)-4-mesitylpyridinium chloride 29 (259 mg, 100%); mp 177.3−
180.2 °C; δH (400 MHz; CD3OD; Me4Si) 8.84 (1H, d, J 6.1), 8.18−
8.12 (m, 1H), 7.87 (1H, dd, J 6.1, 1.9), 7.74 (1H, dd, J 8.8, 0.9), 7.12
(1H, d, J 8.8), 7.09−7.08 (2H, m), 4.03 (s, 3H), 3.75 (s, 3H), 2.47 (s,
3H), 2.37 (s, 3H), 2.14 (s, 6H); δC (176 MHz, CD3OD; Me4Si)
164.17, 160.76, 159.45, 150.20, 140.89, 139.28, 134.22, 133.75, 130.94,
128.91, 128.51, 126.27, 120.38, 117.78, 109.99, 108.05, 99.79, 60.89,
55.66, 22.77, 19.71, 19.16, 16.28.
Iridium Complex 25. The reaction followed the general procedure
for the synthesis of iridium pic complexes, Method B, using IrCl3·
N
DOI: 10.1021/acs.inorgchem.6b01179
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2-(2,4-Dimethoxy-3-(methylsulfonyl)phenyl)-4-mesitylpyridine
30. m-Chloroperoxybenzoic acid (436 mg, 2.68 mmol) was added to a
stirred solution of 2-(2,4-dimethoxy-3-(methylthio)phenyl)-4-mesityl-
pyridinium chloride 29 (510 mg, 1.22 mmol) in DCM (20 mL). The
solution was stirred at RT overnight. The reaction was quenched with
aqueous NaHSO3, and the organic layer was separated. The aqueous
layer was extracted with additional DCM. The organic layers were then
washed with aqueous NaOH before the solvent was removed in vacuo,
and the residue was purified by reverse-phase column chromatography
(water/MeOH) to give a white solid, 2-(2,4-dimethoxy-3-
(methylsulfonyl)phenyl)-4-mesitylpyridine 30 (420 mg, 83%); mp
155.8−160.8 °C, which started to discolour at 148.7 °C; δH (400
MHz; CDCl3; Me4Si) 8.75 (1H, dd, J 5.0, 0.9), 8.05 (1H, d, J 8.9),
7.70 (1H, dd, J 1.6, 0.9), 7.09 (1H, dd, J 5.0, 1.6), 6.98 (1H, d, J 8.9),
6.96 (2 H, s), 4.00 (3 H, s), 3.61 (3 H, s), 3.33 (3 H, s), 2.33 (3 H, s),
2.03 (6 H, s); δC (101 MHz, CDCl3, Me4Si) 158.95, 158.44, 154.71,
150.38, 149.99, 137.74, 137.21, 136.22, 135.07, 128.45, 128.14, 125.69,
123.55, 123.44, 109.10, 63.42, 56.97, 46.25, 21.16, 20.74; HRMS
(FTMS+ESI): calcd for [C23H25NFO4S+H]+: 412.1583. Found:
412.1564.
Iridium Complex 31. [Ir(cod)Cl]2 (51 mg, 0.19 mmol) was added
to a stirred solution of 2-(2,4-dimethoxy-3-(methylsulfonyl)phenyl)-4-
mesitylpyridine 30 (130 mg, 0.32 mmol) in 2-ethoxyethanol (5 mL).
The solution was heated to 130 °C under argon overnight, picolinic
acid (26 mg, 0.21 mmol) was added, and the solution was heated at
130 °C for 6 h under argon. The solution was cooled, and the solvent
was removed in vacuo. The residue was purified by column
chromatography (DCM/CH3CN 2:1 v/v) to give a yellow solid,
iridium complex 31 (70 mg, 40%); Anal. Calcd for C52H52N3O10S2Ir·
1.5 CH2Cl2: C, 50.89; H, 4.37; N, 3.33. Found: C, 50.43; H, 3.97; N,
3.08%; δH (400 MHz; CDCl3; Me4Si) 8.84 (1H, d, J), 8.50 (1H, dd, J
1.8, 0.7 Hz), 8.45 (1H, d, J 7.7), 8.37 (1H, dd, J 1.8, 0.7), 8.04 (1H, td,
J 7.8, 1.6), 7.84 (1H, d, J 5.3), 7.53 (1H, ddd, J 7.4, 5.4, 1.5), 7.45 (1H,
d, J 5.9), 7.05 (1H, dd, J 5.9, 1.9), 7.04−6.96 (4H, m), 6.81 (1H, dd, J
5.9, 1.9), 5.83 (1H, s), 5.78 (1H, s), 3.92 (3H, s), 3.89 (3H, s), 3.55
(3H, s), 3.54 (3H, s), 3.25 (3H, s), 3.20 (3H, s), 2.35 (6H, s), 2.11
(3H, s), 2.05 (3H, s), 2.00 (3H, s), 1.96 (3H, s); HRMS (FTMS
+ESI): calcd for [C52H52N3O10S2191Ir+H]+: 1134.2778. Found:
1134.2792. Crystals for X-ray analysis were grown by slow evaporation
from a DCM/hexane mixture.
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(b) Lee, S.; Kim, S.-O.; Shin, H.; Yun, H.-J.; Yang, K.; Kwon, S.-K.;
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Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS
■
We thank Durham Univ. for a doctoral scholarship (to H.B.),
EPSRC Grant No. EP/L0261X/1 for funding, and Dr. D. S.
Yufit for solving the X-ray crystal structure of complex 23.
O
DOI: 10.1021/acs.inorgchem.6b01179
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