Facile synthesis and complete characterization of homoleptic and heteroleptic cyclometalated Iridium(III) complexes for photocatalysis

Article abstract of DOI:10.1016/j.jorganchem.2014.10.037

Herein we describe an improved synthesis for homoleptic iridium(III) 2-phenylpyridine based photocatalysts that allows rapid access to these compounds in good to high yields which have recently become a vital component within the field of catalysis. In addition, we synthesized a number of heteroleptic iridium(III) 2-phenylpyridine photocatalysts and report their photophysical and electrochemical properties. The emission energies span the range of 473-560 nm and reduction potentials from -2.27 V to -1.23 V and oxidation potentials ranging from 1.81 V to 0.69 V. Additionally, we provide the calculated excited state properties and comment on the role of these properties in designing catalytic cycles.

Full text of DOI:10.1016/j.jorganchem.2014.10.037

Accepted Manuscript
Facile synthesis and complete characterization of homoleptic and heteroleptic
cyclometalated Iridium(III) complexes for photocatalysis
Anuradha Singh , Kip Teegardin , Megan Kelly , Kariate S. Prasad , Sadagopan
Krishnan , Jimmie D. Weaver
PII:
S0022-328X(14)00520-8
10.1016/j.jorganchem.2014.10.037
JOM 18780
DOI:
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 2 October 2014
Revised Date: 23 October 2014
Accepted Date: 25 October 2014
Please cite this article as: A. Singh, K. Teegardin, M. Kelly, K.S. Prasad, S. Krishnan, J.D. Weaver,
Facile synthesis and complete characterization of homoleptic and heteroleptic cyclometalated
Iridium(III) complexes for photocatalysis, Journal of Organometallic Chemistry (2014), doi: 10.1016/
j.jorganchem.2014.10.037.
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ACCEPTED MANUSCRIPT
The emission energies of the cyclometalated iridium-complexes span the range of 473-560 nm and are
shown pictographically by their corresponding color. This range corresponds to a 9 kcal/mol energy
difference in available triplet state energy.

ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
Facile Synthesis andCompleteCharacterization of Homoleptic and
HeterolepticCyclometalated Iridium(III)Complexesfor Photocatalysis
Anuradha Singh, Kip Teegardin, Megan Kelly, Kariate S. Prasad, Sadagopan Krishnan, Jimmie D.
*
Weaver
Department of Chemistry, Oklahoma State University, 107 Physical Science, Stillwater, OK 74078
Corresponding author JDW:
Email: jimmie.weaver@okstate.edu
Phone: +14057443966
Postal Mail: Oklahoma State University, 107 Physical Science, Stillwater, OK 74078

ACCEPTED MANUSCRIPT
relaxes to its long-lived, triplet state.[28, 29] The triplet
Introduction
state has undergone a metal-to-ligand charge transfer and
by virtue of charge transfer, it can serve as both a potent
oxidant and reductant. By knowing the excited state redox
Cyclometalated iridium(III) complexes constitute an
exceptional class of organometallic complexes that possess
remarkable photophysical and photochemical properties.[1,
+
*
*
-
potentials of E1/2(Ir /Ir ) and E (Ir /Ir ) complexes, one can
1/2
begin to rationally design novel chemical transformations
provided the relevant potentials of substrates are known.
With this goal in mind, we desired to develop a simple and
robust method that would allow us to modulate the redox
potentials and triplet state energies of the iridium
photocatalysts, allowing us to more fully explore possible
synthetic transformations.
2] Consequently, these complexes have been utilized in a
number of applications in diverse fields. They have been
especially important in the fields of organic light emitting
diodes (OLEDs),[3-8] dye sensitized solar cells,[9, 10]
sensing[11-14] and biology.[15-17] More recently, these
complexes have been utilized as photocatalysts in the area
of synthetic organic chemistry to perform unique chemical
transformations that take place by catalytic removal (or
addition) of an electron as well as by serving as
photosensitizers.[18-23] Exploration of these complexes as
photocatalysts is still in its infancy and will likely continue
to expand and give rise to powerful chemical
methodologies. Consequently, substantial quantities of
complexes with a range of properties will be needed.
A survey of the literature revealed that there are a number
of reported synthetic methods that use more expensive
Ir(acac)3[30-33] or alternatively require two steps- forming
the chloro-bridged dimer and then subsequently adding the
third ligand. This is done even in the case of the tris-
homoleptic-cyclometalated complexes, which is less than
ideal since it requires additional chemical steps.
Furthermore, a stoichiometric chloride scavenger like
Despite a rich history of exploration in the properties of
these complexes, syntheses for many the facial homoleptic
variants[1] are scattered, and often lack complete chemical,
photophysical, and electrochemical characterization.
Within our own research, we have also utilized this type of
an iridium photocatalyst. Recently, we have disclosed
several photocatalytic reactions which utilize commercially
available fac-tris-(2-phenylpyridine) iridium (Ir(ppy) ) in
which the substrates are activated directly (or indirectly)
via electron transfer or energy transfer from Ir(ppy) .[24-
AgOTf is often employed.[34, 35]
Konno reported
microwave synthesis of tris-cyclometalated iridium
complexes, but this required a large excess of ligand (50-
1
00 equiv.) which limits the scope of the reaction to readily
available ligands such as 2-phenylpyridine.[36] Therefore,
we set about to develop a general and simple synthesis that
would allow us to acquire the facial homoleptic iridium
complexes in high chemical yield via a simple and
selective one step process.
3
3
2
7] However, we often found our research was restricted
Results and Discussion
by the photophysical and electrochemical properties of the
limited number of commercially available photocatalysts.
Herein, we report a simple synthetic method to access these
complexes readily in sufficient quantities for use within the
laboratory. Furthermore, we also report and discuss the
photophysical and electrochemical properties of the
In our initial attempt, a glass pressure vial was charged
with IrCl3•nH O, 2-phenylpyridine, Na CO and water and
2
2
3
heated at 200 °C for 48 h.[37] Unfortunately, this reaction
resulted in extremely low yield (<8%) of the desired
complex, Ir(ppy)3. However, it was observed that the
reaction was heterogeneous until temperatures reached
nearly 200 °C. Concerned that even higher temperatures
may be needed to ensure homogeneity, reproducibility, and
faster reaction rates the remaining reactions were
performed in Parr reactor for safety purposes, allowing us
synthesized
complexes
within
the
context of
photoredoxcatalysis.
Scheme1. Energy and electron transfer processes in
triscyclometalated iridium complexes
to safely heat H O to 260 °C. Routine optimization
2
(Table1) of this reaction provided improvement in yields on
increasing the equivalents of base from 1.5 to 6, 2-
phenylpyridine from 3.3 to 12, and the temperature from
2
00 to 260 °C. Using optimized conditions (entry 3), the
reaction yielded 79% of Ir(ppy) , 3a, in just 24 h.
3
Table 1. Optimization of Reaction Conditions
1
*
3
IrL represents the higher energy spin allowed excited state
3
3
and *IrL represents the lowest spin forbidden excited state
The iridium complexes are tris-cyclometalated d-6, 18-
electron complexes that are remarkably stable in the ground
state. However, upon absorption of photons of the
appropriate energy-in the blue region of the visible
spectrum, the complexes undergo excitation (Scheme 1).
Initially, an excited singlet state is produced but it rapidly

ACCEPTED MANUSCRIPT
Pleased with this result, we next attempted to investigate
observed for 3d but is likely a result of the effectively
lower concentration of 2d, since only 6 equiv. were used
due to smaller quantities on hand. Using standard
conditions, new complex, 3f, was obtained only in trace
amounts and addition of base did not prove helpful. In
these cases, the major product was the choro-bridged
dimer. However, 3f was finally successfully obtained by
subjecting the chloro-bridging dimer to excess ligand in the
presence of AgOAc.
the scope of the method which required the syntheses of the
requisite 2-phenylpyridine ligands 2b-g (Scheme 2) which
we hoped would lead to catalyst with a range of properties.
The ligands were synthesized quite easily via Suzuki
coupling of 2-chloropyridine (1 equiv.) and the requisite
boronic acid (1.2 equiv.) with only minor modifications to
the literature procedure.[38] Conveniently, the procedure
could be performed outside the glovebox. In all cases, the
Suzuki coupling reaction led to good yields of the desired
phenylpyridine products and in one case (2c) approached
Scheme 3. Synthesis of Facial Homoleptic Tris-
Cyclometalated Iridium Complexes
quantitative yields.
Ligand 2h (4-(tert-butyl)-2-(4-
fluorophenyl)pyridine) was synthesized via Baran’s
procedure.[39]
Scheme 2. Ligand Synthesis
With ligands (2a-h) in hand, we returned to the
cyclometalation reaction (Scheme 3). However, under the
standard reaction conditions, several of the substrates
presented problems. Upon modification of our initial
conditions, yields were improved and substantial quantities
were obtained.
phenylpyridine) (2e) was subjected to the reaction
conditions the expected 3e was not formed. Rather, 3a
For instance, when 2-(3-tert-butyl)
a
2 3
No Na CO used.
While our initial focus was in the syntheses of the
homoleptic iridium complexes, cationic heteroleptic
iridium complexes[2] have also proven to be effective
photocatalysts and we sought to synthesize the cationic
complexes as well. In the cationic complexes, the third 2-
phenylpyridine ligand is replaced with 2,2’-bipyridine type
ligand. Thus, in order to be able to modify the third ligand,
the dichloro-bridged iridium dimer was selectively
synthesized according to Nonoyama’s procedure[42] which
was then subsequently treated with the third, bipyridyl
ligand to afford cationic heteroleptic iridium complexes
Ir(ppy) along with 2-phenylpyridine, 2a, were the primary
3
products recovered which apparently resulted from the
detertbutylation of either (or both) ligand or Ir-complex at
°
°
2
60 C. However, by lowering the temperature to 200 C
we were able to suppress detertbutylation and obtain 3e in
high yield. Moreover, our initial attempts to synthesize 3c
resulted in a mixture of iridium complexes in which partial
hydrolysis of fluorine had occurred. Additionally, we
observed a migration of fluorine on the ring of the ligand
recovered from the reaction mixture.[40] To avoid this
problem, reaction with 2-(4-fluorophenyl) pyridine, 2c,
ligand was performed in the absence of sodium carbonate
and at lower temperatures (200 °C for 48 h). Surprisingly,
using these conditions the reaction proceeded smoothly to
achieve 3c in excellent yield. This experiment suggested
that no base is required to synthesize triscyclometalated
iridium complexes and, to the best of our knowledge, this is
the first report that suggests that the base is not necessary
for the formation of these complexes. Thus, for the
remainder of the fluorinated substrates, the reactions were
carried out with no base which allowed us to acquire 3b-e,
and 3h complexes in moderate to high yields. 3h was
synthesized in 84% yield and was very recently used as a
catalyst for the deacarboxylative arylation of α-amino acids
and α-etheral acids though its synthesis and properties have
never been reported.[41] A more modest yield was
(scheme 4).[43]

ACCEPTED MANUSCRIPT
Scheme 4. Synthesis of Cationic Iridium Complexes
N
N
N
N
Ir
N
C
C
C
N
N
CH
x
C
Cl
Cl
N
5y
3 2
IrCl •nH O
Ir
PF6
Ir
2
C
C
N
N
N
4
xy
+
CF
3
+
CF
3
+
F
CF
3
F
F
F
tBu
tBu
N
N
N
N
N
N
N
N
F
F
F
F
F
F
Ir
Ir
Ir
N
N
N
N
F
F
CF
3
CF
3
CF
3
4gb, 74%, 78%
4
ga, 74%, 91%
4gc, 74%,81%
+
F
F
+
+
tBu
tBu
N
N
N
N
N
N
N
F
F
F
F
F
F
Ir
Ir
Ir
Figure 1. Absorbance Spectra of Facial Homoleptic Iridium
Complexes (3a-f,h) 10 µM in MeCN.
N
N
N
N
N
F
F
4
db, 82%, 57%
4dc, 82%, 88%
4cb 88%, 96%
From a catalysis standpoint, the emission frequency
corresponds to the energy available for energy transfer to
substrates, (i.e., the triplet state energy, TSE). The
complexes were excited in the region of 370-390 nm which
corresponds to the metal-to-ligand charge transfer
tBu
tBu
+
tBu
OMe
+
N
Ir
N
N
N
N
F
F
Ir
N
N
N
tBu
OMe
excitation.[45]
In general, electron-withdrawing
4
cc, 88%,92%
4fd, 60%, 99%
substituents on the phenyl ring such as fluorine lowers the
energy of HOMO resulting in larger HOMO-LUMO gaps
and greater emission energies (more blue shifted).
Whereas electron-donating substituents such as alkyl
groups raise the HOMO energy, resulting in smaller
HOMO-LUMO gaps and lower emission energies (more
red shifted).[46, 47] As expected, in complexes that have
electron-withdrawing groups (3b-d and 3h Figure 3), a 10-
-
Cationic heteroleptic Ir(III) Complexes 4a-h with PF
6
counteranion. First step yield followed by second step.
The cyclometalated iridium(III) chloro-bridged dimer
Ir(ligand) Cl]2 was prepared by following Nonoyama’s
2
procedure[42] in which hydrated iridium(III) chloride was
heated with substituted phenylpyridine ligand in a 2:1
methoxyethanol/H O mixture at only 120 °C. Upon
cooling, the chloro-bridging dimer precipitated and was
carried onto the second step. The catalysts were diversified
by use of several bipyridine ligands. Finally, anion
metathesis was achieved by the addition of aqueous
NH PF . In this manner, complexes 4xy (Scheme 4) were
synthesized. In some cases, complexes were further
purified by recrystallization. This is the first report for
complexes 3f, 4ab, 4cb and 4fd. All synthesized facial
homoleptic and cationic heteroleptic complexes were
[
2
4
0
nm hypsochromic shift is observed whereas
bathochromic shift of 5-10 nm is observed in alkyl
substituted complexes (on the phenyl ring), 3e and 3f, when
compared to that of Ir(ppy)3 (3a). Furthermore, as the
degree of fluorine substitution increases, more blue shifting
was observed (3d vs. 3c). Similar trends were observed in
the case of heteroleptic cationic iridium complexes (Figure
4
6
4
).
1
13
19
31
characterized by H, C, F, P NMR, LCMS, and new
complexes by elemental analysis
.
With iridium complexes in hand, we next turned to the
investigation of the photophysical properties of the facial
homoleptic 3a-f and the heteroleptic 4xy complexes.
Absorbance of the facial homoleptic (Figure 1) and the
heteroleptic (Figure 2) were measured in acetonitrile (10
ꢀM). As depicted in Figure 1 and 2 all the complexes show
intense UV absorption band below 325 nm-characteristic of
spin allowed transition of ligand (π-π⃰ )[44] and weaker,
broad and unresolved absorption band into visible region
from 320-480 nm generally assigned as both allowed and
spin-forbidden metal to ligand charge transfer (MLCT)
transitions.[44]
Figure 2. Absorbance spectra of 3a and cationic
heteroleptic iridium complexes (4xy) 10 µM in MeCN.
Electron withdrawing groups (4ga, gb, gc) resulted in a 42-
4
5 nm blue shift with respect to Ir(ppy) (3a). Complex
3
4
db shows 55 nm bathochromic shift relative to more
fluorinated complexes 4ga, gb, gc. Addition of electron
donating tert-butyl groups on bipyridyl (4de) resulted in a
1
2 nm hypsochromic shift compared to complex 4db. In
the mono-fluoro series, a similar trend was observed (4cb

ACCEPTED MANUSCRIPT
and 4cc). Complexes 4db, 4fcb, 4cc and 4fd depict a 10-
2 nm red shift and 4ga, 4gb, 4gc, 4dc a 2-45 nm blue shift
relative to ferrocenium/ferrocene redox couple as shown in
4
Table 4. The cyclic voltammograms of complexes were
collected at a scan rate of 50 mV/s. As anticipated,
complexes having electron withdrawing fluorine groups
from Ir(ppy) (3a). Furthermore, among these complexes,
3
complex 4fd was found to be the most red shifted (vs. 3a)
with poor emission which could be due to the methoxy
substituents.[48] In most complexes, broad emission
spectra were observed which could be due to significant
degree of charge transfer (CT) whereas structured spectra
in 4ga and 4gc suggest a small CT contribution.[49]
1/2
+
(3b-d. vs 3a) show higher ground state Eox (Ir /Ir) due to
lowering of HOMO energy level. All cationic complexes
1/2
+
show higher ground state Eox (Ir /Ir) when compare to
that of 3a, and among all complexes 4ga and 4gc exhibit
1/2
1/2
the highest ground state Eox
.
Whereas, lower Eox
potentials were observed when an electron donating tBu-
substituent was located on the ligand (3e, 3f vs. 3a) as this
group is expected to raise the HOMO energy level making
it more easily oxidized.[52]
Complexes that have electron withdrawing fluorines on the
ligand make them less reducing (smaller negative ground
1/2
-
state) Ered (Ir/Ir ) as observed in 3b-d and 3h relative to
a. Complexes that have an electron donating alkyl group
3
1/2
-
(
3e vs 3a) possess a more negative Ered (Ir/Ir ) potential-
though 3f is slightly less reducing than 3a. Among cationic
complexes 4fd found to be the most reducing as it contains
electron rich tBu- and methoxy substituent on ligands.
Furthermore, tBu-bipyridine complexes are more reducing
(
4da vs 4dc, 4cb vs 4cc)
Knowing the excited state redox values is a key element in
designing photocatalytic reactions, but the excited state
redox potentials cannot be directly evaluated. However,
they can be calculated from the electrochemically
determined ground state Eox and Ered potentials and the
energy gap (Egap). Egap values were determined from the
CV.
Figure 3 Emission spectra of facial homoleptic iridium
complexes (3a-f,h excited at 385 nm, 372 nm, 380 nm, 378
nm, 390 nm, 383 nm, 385 nm respectively) 5 µM in MeCN
except 3a 10 µM in MeCN.
1/2
1/2
In all complexes emission is from the lowest energy triplet
3
3
1
/2
+
1/2
state which is likely formed by mixing of the MLCT, LC
E
E
(Ir /Ir*) = E
– Egap eV
(eq 1)
(eq 2)
ox
3
and LLCT states.[17, 50, 51] The emission maximum
1/2
-
1/2
(Ir*/Ir ) = E eV + Ered
gap
(
λmax) is the triplet state energy which can be used in
photocatalysis for energy transfer processes (Scheme
).[25-27]
We calculated the redox values of the excited state
1
1/2
+
1/2
-
complexes, E (Ir*/Ir ) and E (Ir*/Ir ) using equations 1
and 2 and the potentials are shown in Table 4. The table is
arranged in descending emission energy values.
Table 4. Photophysical and electrochemical data
for iridium complexes
+
⃰
-
complex λmax TSE kcal/mol
E1/2 oxV
E E1/2 (Ir /I r⃰ ) E1/2 (Ir/Ir )
1/2 red V Egap eV
4
4
4
3
3
gb
ga
gc
d
h
c
473
475
476
476
481
488
507
516
518
525
528
528
540
556
560
60.4
60.2
60.1
60.1
59.4
58.6
56.4
55.4
55.2
54.5
54.2
54.2
53
1.23
1.81
1.77
0.98
0.926
1
1.11
1.63
0.78
0.69
0.7
-1.23
-1.25
-1.35
-1.82
-1.58
-2.13
-2.13
-1.42
-2.2
-2.27
-2.03
-1.32
-1.45
-1.37
-1.5
2.2
-0.97
-0.83
-1
-1.23
-1.274
-1.86
-1.65
-0.93
-1.97
-1.9
-1.59
-0.8
-1.04
-0.89
-1.12
0.97
1.39
1.42
0.39
0.62
0.73
0.63
1.14
0.55
0.32
0.25
1.14
1.07
1.03
0.85
2.64
2.77
2.21
2.2
2.86
2.76
2.56
2.75
2.59
2.28
2.46
2.52
2.4
3
3
b
4dc
3
3
3
a
e
f
4
4
4
4
db
cc
cb
fd
1.66
1.49
1.51
1.17
Figure 4 Emission spectra of 3a and heteroleptic iridium
complexes (4xy, excitation wavelength, concentration in
MeCN) (4ga 376 nm 2.5 µM, 4gb 370 nm 10 µM, 4gc 375
nm 5 µM, 4db 368 nm 10 µM, 4dc 365 nm 10 µM, 4cb
51.4
51.2
2.35
3
80 nm 10 µM, 4cc 370 nm 10 µM, 4fd 390 nm 4h 50
Conclusions
µM).
In conclusion, we have reported simple synthetic
procedures that allow rapid access to an important class of
Having investigated the photophysical properties, we next
turned to the electrochemical properties of the iridium
complexes via cyclic voltammetry (CV) which is reported
iridium photoredox catalysts.
We have successfully
developed a simple and general synthesis that provides

ACCEPTED MANUSCRIPT
efficient access to facial tris-cyclometalated iridium
complexes directly from less expensive IrCl3 nH O. In
was added to the reaction mixture and degassing continued
•
for 15 more minutes and then the outlet was removed. The
reaction mixture was heated to reflux. The progress of
reaction was monitored by TLC (hexane:EtOAc 90:10).
Upon completion (typically 18-24 h), reaction mixture was
cooled to room temperature and then extracted with DCM
(3 x 20 mL). The combined organic portion was washed
with water (3 x 20 mL) and brine (1 x 20 mL), dried over
anhydrous sodium sulfate and then concentrated in vacuo.
The crude material was purified by flash chromatography
to obtain pure ligand.
2
addition, we applied Nonoyama’s method in order to
synthesize a number of cationic heteroleptic iridium
complexes. Importantly, we have provided the chemical,
photophysical and electrochemical characterization
necessary to facilitate catalysis. This should significantly
aid in the design of novel chemical transformations via
photocatalysis by facilitating access to the catalysts and by
providing the relevant photophysical and electrochemical
properties necessary to rationally design new synthetic
methods.
2
b, the general procedure A was followed using 2-
chloropyridine (2.0 g, 17.62 mmol), (4-
trifluoromethyl)phenyl)boronic acid (4.08 g, 21.15 mmol),
General Experimental
(
2
M K CO (6.55 g, 47.52 mmol), PPh (461 mg, 1.760
2
3
3
All reagents were obtained from commercial suppliers
mmol), Pd(OAc)2 (99 mg, 0.4420 mmol) and ethylene
glycol dimethyl ether (20 mL). The crude material was
purified by flash chromatography using hexane: ethyl
acetate (0-5 % EtOAc for 40 cv and ramped to 100 %
EtOAc for 40-70 cv and then held at 100% EtOAc 70-80 cv
on 24 g silica column) to afford 2b in 67% yield (2.60 g,
(
Sigma-Aldrich, Oakwood chemicals, Alfa Aesar, Strem,
and VWR) and used without further purification unless
otherwise noted. NMR spectra were obtained on 400 MHz
Bruker Avance III spectrometer and 400 MHz Unity Inova
1
13
spectrometer.
H, and C, NMR chemical shifts are
reported in ppm relative to the residual solvent peak while
1
1
9
31
11.65 mmol) as a white solid. H NMR matches literature
values.[53]
F and P NMR are set relative to an external standard.
Purifications were carried out using Teledyne Isco
Combiflash Rf 200i flash chromatograph with Redisep Rf
normal phase silica (24 g, 40 g, or 80 g) column with
product detection at 254 and 280 nm and by ELSD
2c, the general procedure A was followed using 2-
chloropyridine (2.0 g, 17.62 mmol), (4-fluorophenyl)
boronic acid (2.96 g, 21.15 mmol), 2 M K
47.52 mmol), PPh (461 mg, 1.760 mmol), Pd(OAc)
mg, 0.4420 mmol) and ethylene glycol dimethyl ether (20
mL). The crude material was purified by flash
CO
(6.55 g,
2
3
(
evaporative light scattering detector). Substrate synthesis
reactions were monitored by thin layer chromatography
TLC) obtained from Sorbent Technology; Silica XHL
3
2
(99
(
TLC Plates, w/UV254, glass backed, 250 µm, and were
visualized with ultraviolet light. Photophysical properties
were studied on Varian Cary Eclipse spectrophotometer
and LCMS was taken on Shimadzu liquid chromatograph
mass spectrometer (LCMS-2010 E). Electrochemical
measurements were performed with CH instruments using
a glassy-carbon electrode as a working electrode with a
Ag/AgCl reference electrode and a platinum wire as
counter electrode. All sample solutions were prepared in
acetonitrile and degassed with nitrogen bubbling for 20
chromatography using hexane:ethyl acetate (0-5 % EtOAc
for 40 cv and ramped to 100 % EtOAc for 40-70 cv and
then held at 100% EtOAc 70-80 cv on 24 g silica column)
to afford 2c in quantitative yield (3.0 g, 17.32 mmol) as a
1
white solid. H NMR matches literature values.[54]
2
d, the general procedure A was followed using 2-
chloropyridine (1.0 g, 8.80 mmol), (2,4-difluorophenyl)
boronic acid (1.67 g, 10.56 mmol), 2 M K CO (3.28 g,
2
3
2
3.76 mmol), PPh (231 mg, 0.8817 mmol), Pd(OAc) (49
3
2
mg, 0.2188 mmol) and ethylene glycol dimethyl ether (10
mL). The crude material was purified by flash
min. prior to voltammetric studies.
Tetra-(n-butyl)-
ammonium hexafluorophosphate (NBu PF , 0.1 M in
4
6
chromatography using hexane:ethyl acetate (0-5 % EtOAc
for 40 cv and ramped to 100 % EtOAc for 40-70 cv and
then held at 100% EtOAc 70-80 cv on 24 g silica column)
to afford 2d in 56% yield (0.94 g, 4.92 mmol) as colorless
acetonitrile) was used as supporting electrolyte. The
HOMO and LUMO energy is calculated from equation eq
3
.
1
E HOMO/LUMO = - ( E onset oxi/red vs Fc +4.8) eV
(eq 3)
oily liquid. H NMR matches literature values.[55]
2
e, the general procedure A was followed using 2-
chloropyridine (2.0 g, 17.62 mmol), (4-(tert-butyl)
phenylboronic acid (3.76 g, 21.15 mmol), 2 M K CO (6.55
General procedure A for the synthesis of ligands (2b-2g)
2
3
g, 47.52 mmol), PPh (461 mg, 1.760 mmol), Pd(OAc) (99
3
2
mg, 0.4442 mmol) and ethylene glycol dimethyl ether (20
mL). The crude material was purified by flash
chromatography using hexane:ethyl acetate (0-5 % EtOAc
for 40 cv and ramped to 100 % EtOAc for 40-70 cv and
then held at 100% EtOAc 70-80 cv on 24 g silica column)
to afford 2e in 79% yield (2.93 g, 13.90 mmol) as colorless
1
To a two necked, 100 mL round bottom flask equipped
with a magnetic stir bar were added 2-chloropyridine (1
equiv), phenylboronic acid (1.2 equiv), triphenylphosphine
oily liquid. H NMR matches literature values.[56]
2
f, the general procedure A was followed using 2-
chloropyridine (2.0 g, 17.62 mmol), (3-(tert-butyl)phenyl)
boronic acid (3.76 g, 21.15 mmol), 2 M K CO (6.55 g,
(0.1 equiv), 2 M potassium carbonate (2.7 equiv) and
2
3
ethylene glycol dimethyl ether (0.9 M). The mixture was
4
7.52 mmol), PPh (461 mg, 1.760 mmol), Pd(OAc) (99
3
2
degased with Ar for 15 min. Then Pd(OAc) (2.5 mol%)
2
mg, 0.4420 mmol) and ethylene glycol dimethyl ether (20

ACCEPTED MANUSCRIPT
mL).
The crude material was purified by flash
chromatography using hexane:ethyl acetate (0-5 % EtOAc
for 40 cv and ramped to 100 % EtOAc for 40-70 cv and
then held at 100% EtOAc 70-80 cv on 24 g silica column)
to afford 2f in 79% yield (2.76 g, 13.09 mmol) as colorless
1
oily liquid. H NMR (Chloroform-d, 400 MHz): δ = 8.75 –
8
7
1
.71 (m, 1H), 8.07 (t, 1H, J=1.8 Hz), 7.83 – 7.71 (m, 3H),
.53 – 7.41 (m, 2H), 7.25 (ddd, 1H, J=6.7, 4.8, 2.1 Hz),
.42 (s, 9H) ppm.
A Parr reactor (1 L model 4533, figure S1) was charged
with iridium (III) chloride (1 equiv), ligand (12 equiv),
sodium carbonate (6 equiv) and DI water (.03 M). The
reaction mixture was pressurized (30 PSI) and
depressurized with Ar (3x) and finally charged again with
Ar before sealing. The reaction mixture was heated at 200
2
g, the general procedure A was followed using 2-chloro-5-
(
trifluoromethyl) pyridine (2.0 g, 11.02 mmol), (2,4-
difluorophenyl) boronic acid (2.09 g, 13.22 mmol), 2 M
K CO (4.11g, 29.75 mmol), PPh (288 mg, 1.099 mmol),
2
3
3
Pd(OAc)2 (62 mg, 0.2881 mmol) and ethylene glycol
dimethyl ether (20 mL). The crude material was purified
by flash chromatography using hexane:ethyl acetate (0-5 %
EtOAc for 40 cv and ramped to 100 % EtOAc for 40-70 cv
and then held at 100% EtOAc 7080 cv on 24 g silica
column) to afford 2g in 79% yield (2.58 g, 9.961 mmol) as
°
C for 24-48 h. After cooling to room temperature, reaction
mixture was extracted with DCM (3 x 20 mL). The
combined organic portion was filtered through celite pad
which was then concentrated to obtain crude product. The
pure compound 3a-3f was obtained by performing flash
chromatography. For most complexes, (3a-3d) crude
samples were dry loaded on silica prior to running the
column due to low solubility of the complex. After elution
of the ligand with hexane/ethylacetate the eluting solvent
was switched to dichloromethane, which faciliated the
elution of the iridium complexes (3a-3f).
1
white solid. H NMR matches literature values.[43]
Procedure for the synthesis of 2h
°
3
a, the general procedure B was followed at 260 C using
iridium (III) chloride (192 mg, 0.64 mmol), 2-
phenylpyridine (1.19 g, 7.7 mmol), Na CO (407 mg, 3.8
2
3
mmol), and DI water (850 mL). The crude material was
purified by flash chromatography (dry loaded) using
hexane:ethyl acetate (0-10 % EtOAc for 40 cv to isolate
ligand and then switched to DCM as well as ramped to 100
A two necked 250 mL round bottom flask was equipped
with a magnetic stir bar, 4-tert-butyl pyridine (1.00 g, 7.41
mmol, 1 equiv) and 40 mL dichloromethane. Then
trifluoroacetic acid (567 uL, 7.41 mmol 1 equiv), 40 mL of
an aqueous silver nitrate solution (0.03 M), 4-
flourophenylbronic acid (1.54 mg, 11.1 mmol, 1.5 equiv),
and potassium persulfate (3.09 g, 22.2 mmol, 3 equiv) were
added. The reaction was stirred vigorously at room
temperature for 6 hours and a second addition of silver
nitrate (252 mg, 1.48 mmol, 0.2 equiv) and potassium
persulfate (3.09 g, 22.2 mmol, 3 equiv) were added. After
%
DCM for 40-70 cv and then held at 100% DCM 70-80
cv) on 24 g silica column to afford 3a in 79% yield (311
mg, 0.47 mmol) as a yellow solid which matched with the
literature.[57] LC/MS (m/z) calculated for C H IrN
33
24
3
6
55.16 found, 654.50.
3
b, the general procedure B was followed except that no
sodium carbonate was used, using iridium (III) chloride
100 mg, 0.33 mmol), 2-(4-(trifluoromethyl) phenyl)
(
1
8 h, another addition of 4-fluorobenzene boronic acid (515
pyridine 2b (896 mg, 4.0 mmol) and DI water (100 mL).
The crude material was purified by flash chromatography
mg, 3.71 mmol, 0.5 mmol) and potassium persulfate (1.03
g, 7.41 mmol, 1 equiv) were added. The progress of
reaction was monitored by TLC (hexane:EtOAc 90:10).
Upon completion, the reaction mixture was diluted with a
(dry loaded) using hexane:DCM (0 % DCM for 16 cv and
ramped to DCM 100 % for 16-20 cv and then held at 100%
DCM for 20-23 cv) on 80 g silica column) to afford 3b in
5
(
% sodium bicarbonate solution and extracted with DCM
3 x 20 mL). The combined organic layer was dried over
anhydrous magnesium sulfate and then concentrated in
vacuo. The crude material was purified by flash
1
7
8 % yield (221 mg, 0.26 mmol) as a yellow solid.
H
NMR(Chloroform-d, 400 MHz): δ = 7.99 (d, 3H, J=8.3
Hz), 7.77 – 7.69 (m, 6H), 7.55 (dd, 6H, J=6.0, 1.3 Hz), 7.20
–
3
7.15 (m, 3H), 7.02 (ddd, 3H, J=7.1, 5.2, 1.1 Hz), 6.96 (b,
chromatography using hexane:ethyl acetate (0-5 % EtOAc
for 40 cv and ramped to 100 % EtOAc for 40-70 cv and
13
H) ppm. C NMR (Methylene Chloride-d , 101 MHz): δ
2
=
165.0, 159.2, 147.5 – 147.4 (m), 147.3, 137.0,132.4 (m),
then held at 100% EtOAc 70-80 cv on 24 g silica column)
1
9
1
130.6, 123.9, 123.4, 120.0, 117.3 – 117.2 (m), 100.0.
F
to afford 2h in 29% (492 mg, 2.15 mmol) as a clear oil.
H
NMR (376 MHz, Chloroform-d) δ -62.76 (s). LC/MS
NMR matches literature values.[39]
(
m/z) calculated for C H F IrN 859.12 found M, 858.70
36 21 9 3
General procedure B for the synthesis of homoleptic fac-
3
c, the general procedure B was followed except that no
Ir (C^N) complexes (3a-3f,h)
3
sodium carbonate was used, using iridium (III) chloride
100 mg, 0.33 mmol), 2-(4-fluorophenyl)pyridine 2c (678
(
mg, 3.9 mmol) and DI water (100 mL). The crude material
was purified by flash chromatography (dry loaded) using
hexane: DCM (0-50 % DCM for 25 cv, held at 50% for 25-
3
5 cv and ramped to 100 % DCM for 35-36 cv and then

ACCEPTED MANUSCRIPT
13
held at 100% DCM 36-41 cv) on 40 g silica column to
6.67 (dd, 3H, J = 7.8, 5.7 Hz), 1.35 (s, 27H). C NMR
afford 3c in 78 % yield (202 mg, 0.29 mmol) as a yellow-
(101 MHz, Methylene Chloride-d ) δ 167.1, 157.3, 147.4,
2
1
green solid. H NMR(Methylene Chloride-d , 400 MHz): δ
143.3, 142.4, 136.4, 136.1, 127.6, 122.0, 120.7, 118.9, 34.2,
31.4. Anal. Calcd for C H IrN : C, 65.66; H, 5.88; N,
2
=
7.88 (d, 3H, J=8.2 Hz), 7.72 – 7.64 (m, 6H), 7.52 (ddd,
45
48
3
3
6
H, J=5.5, 1.6, 0.8 Hz), 6.94 (ddd, 3H, J=7.1, 5.6, 1.3 Hz),
.63 (td, 3H, J=8.7, 2.7 Hz), 6.39 (dd, 3H, J=10.3, 2.7 Hz)
5.11. Found: C, 64.82; H, 4.98; N, 5.57. LC/MS (m/z)
calculated for C H IrN 823.35 found 822.90.
45
48
3
13
ppm.
1
1
C NMR(Methylene Chloride-d , 101 MHz): δ =
2
3h, the general procedure B was followed except that no
sodium carbonate was used, using iridium (III) chloride
65.3 (d, J=5.4 Hz), 163.4 (d, J=5.7 Hz), 162.8, 147.2,
40.2, 136.6, 125.8 (d, J=9.2 Hz), 122.0, 121.8 (d, J=16.4
(25
mg,
0.083
mmol),
4-(tert-butyl)-2-(4-
1
9
Hz), 118.9, 107.4 (d, J=23.6 Hz) ppm.
MHz, Methylene Chloride-d ) δ -112.33 (ddd, J = 10.3, 9.1,
5
7
F NMR (376
fluorophenyl)pyridine 2h (230 mg, 1 mmol) and DI water
(100 mL). The crude material was purified by flash
chromatography (dry loaded) using hexane: DCM (0-50 %
DCM for 25 cv, held at 50% for 25-35 cv and ramped to
100 % DCM for 35-36 cv and then held at 100% DCM 36-
41 cv) on 40 g silica column to afford 3h in 84 % yield (61
2
.7 Hz). ). LC/MS (m/z) calculated for C H F IrN
33 21 3 3
09.13 found, 708.60.
d, the general procedure B was followed except that no
3
sodium carbonate was used, using iridium (III) chloride
1
(50 mg, 0.16 mmol), 2-(2,4-difluorophenyl)pyridine 2d
mg, 0.070 mmol) as a yellowish green solid. H NMR (400
(
184 mg, 0.96 mmol) and DI water (100 mL). The crude
MHz, Chloroform-d) δ 7.73 – 7.69 (m, 3H), 7.56 (dd, 3H, J
= 8.6, 5.7 Hz), 7.28 (d, 3H, J = 5.9 Hz), 6.83 (dd, 3H, J =
5.9, 1.8 Hz), 6.53 (td, 3H, J = 8.7, 2.6 Hz), 6.44 – 6.38 (m,
3H), 1.26 (s, 27H). 13C NMR (101 MHz, Chloroform-d) δ
164.0 , 163.0 (d, J = 251.5 Hz), 163.0 (d, J = 5.6 Hz),
159.1, 145.4, 139.2, 124.2 (d, J = 9.1 Hz), 121.3 (d, J =
16.1 Hz), 118.3, 114.37, 106.1 (d, J = 23.7 Hz), 33.9, 29.5.
19F NMR (376 MHz, Chloroform-d) δ -112.01 (s, 1F).
LC/MS (m/z) calculated for C H F IrN 877.32 found
material was purified by flash chromatography (dry loaded)
using hexane:ethyl acetate (0-40% EtOAc for 30 cv,
changed EtOAc to DCM and ramped to 100 % DCM for
3
0-31 cv and then held at 100% DCM 31-39 cv) on 40 g
silica column to afford 3d in 56 % yield (68 mg, 0.09
mmol) as a pale yellow solid. The NMR specta matched
with the literature.[31] H NMR (400 MHz, DMSO-d ) δ
8
3
1
1
6
.27 (d, 3H, J = 8.6 Hz), 7.95 (t, 3H, J = 7.5 Hz), 7.54 (d,
H J = 5.1 Hz), 7.26 (t, 3H, J = 6.4 Hz), 6.70 (td, 3H, J =
4
5
45
3
3
877.20.
13
0.1, 9.2, 5.0 Hz), 6.06 (dd, 3H, J = 8.7, 2.2 Hz).
C
General Procedure C for the synthesis of cationic
NMR(Methylene Chloride-d , 101 MHz): δ = 162.9 (d,
J=7.5 Hz), 162.5 (d, J=11.5 Hz), 161.3, 147.2, 137.4,
+
-
2
heteroleptic [ Ir (C^N) (bpy)] PF complexes (4xy)
2 6
1
9
23.3 (d, J=20.9 Hz), 122.4, 117.8 (dd, J=16.1, 2.8 Hz),
6.6 (t, J=27.2 Hz) ppm. F NMR (376 MHz, Methylene
1
9
Chloride-d ) δ -109.68 (q, 3F, J = 9.3 Hz), -110.86 (ddd,
2
3
F, J = 12.6, 9.9, 2.3 Hz). LC/MS (m/z) calculated for
C H F IrN 763.10 found 763.00.
33
18
6
3
3
e, the general procedure B was followed using iridium
(
III) chloride (100 mg, 0.33 mmol), 2-(4-(tert-
Heteroleptic iridium 4xy were synthesized in a two-step
procedure.[42, 43] In the first step, chloro-bridged dimer
was synthesized by charging a two-necked reaction flask
with magnetic stir bar, iridium(III) chloride (1 equiv),
butyl)phenyl)pyridine 2e (844 mg, 4.0 mmol), sodium
carbonate (210 mg, 2.0 mmol) and DI water (200 mL). The
crude material was purified by flash chromatography using
hexane:ethyl acetate (0-20 % EtOAc for 40 cv, switched
EtOAc to DCM and ramped to 100 % DCM for 40-60 cv
and then held at 100% DCM 60-65 cv) on 24 g silica
column to afford 3e in 92 % yield (249 mg, 0.30 mmol) as
ligand (2.26 equiv), and
a 2:1 v:v mixture of 2-
methoxyethanol/water. The mixture was degased with Ar
o
(
via Ar bubbling) and heated under reflux at 120 C with
1
constant stirring overnight. The reaction mixture cooled to
room temperature and filtered. The precipitate was washed
with water (3 x 10 mL), dried in air and taken onto the
second step without further purification unless noted. In
the second step, the chloro-bridging dimer (1equiv),
bipyridyl ligand (2.2 equiv) and ethyleneglycol were placed
in a two-necked flask and then flushed with Ar. The
a yellow solid. H NMR (400 MHz, Chloroform-d) δ 7.79
(d, 3H, J = 8.2 Hz), 7.60 – 7.48 (m, 9H), 6.93 – 6.86 (m,
13
6
H), 6.83 (ddd, 3H, J = 7.0, 5.6, 1.1 Hz), 1.10 (s, 27H).
C
NMR (101 MHz, Chloroform-d) δ 167.5, 161.5, 152.4,
1
3
8
47.5, 141.6, 136.0, 134.9, 123.5, 121.8, 118.8, 117.2, 34.8,
1.8. LC/MS (m/z) calculated for C H IrN 823.35 found
4
5
48
3
22.65
o
mixture was heated at 150 C for 15 h and then cooled.
3
f, the general procedure B was followed using iridium
The cooled reaction mixture was washed hexane (3 x 10
o
(
III) chloride (25 mg, 0.083 mmol), 2-(3-(tert-butyl)
phenyl)pyridine 2f (200 mg, 0.95 mmol), and DI water (50
mL). The crude material was purified by flash
chromatography using hexane:EtOAc (0-10 % EtOAc for
2 cv, switched EtOAc to DCM and ramped to 100 %
mL) and mixture was heated to 85 C for 5 min. to remove
residual hexane. Aqueous ammonium hexafluorophosphate
(sat. solution) was added to the reaction mixture causing
the iridium-PF salt to precipitate, which was filtered, dried
6
3
and recrystallized (acetone/ether).
DCM for 32-42 cv and then held at 100% DCM 42-44 cv)
on 24 g silica column to afford 3f in 16 % yield (11 mg,
0
Methylene Chloride-d ) δ 7.99 (dd, 3H, J = 8.3, 5.6 Hz),
7
4
ga, the general procedure C was followed using
1
iridium(III) chloride (178 mg, 0.60 mmol), 2-(2,4-
difluorophenyl)-5-(trifluoromethyl)pyridine pyridine 2g
.013 mmol) as a yellow solid.
H NMR (400 MHz,
2
(352 mg, 1.4 mmol) and
a 2:1 mixture of 2-
.82 – 7.56 (m, 9H), 6.95 (ddd, 6H, J = 10.2, 6.0, 1.8 Hz),
methoxyethanol/water (12 mL) to obtain the dimer in 74%

ACCEPTED MANUSCRIPT
1
3
yield (326 mg, 0.22 mmol) as yellow solid. 4ga was
synthesized using the dimer (50 mg, 0.034 mmol),
phenanthroline (5a, 14 mg, 0.075 mmol) and ethylene
glycol (2 mL). 4ga was obtained in 91% yield (64 mg,
2.3 Hz), 1.45 (s, 18H). C NMR (101 MHz, Acetone-d ) δ
6
167.9 (d, J = 7.5 Hz), 165.4, 164.6 (dd, J = 258.5, 12.7 Hz),
162.5 (dd, J = 261.8, 13.1 Hz), 156.0, 155.8 (d, J = 7.0 Hz),
151.1, 145.7 (q, J = 4.8 Hz), 137.2 (d, J = 3.0 Hz), 126.8
(dd, J = 4.4, 2.5 Hz), 126.0, 125.3 (d, J = 35.3 Hz), 123.9
(d, J = 21.0 Hz), 122.6, 122.2 (d, J = 271.7 Hz), 114.5 (dd,
J = 17.8, 3.0 Hz), 99.3 (apparent t, J = 27.1 Hz), 35.7, 29.5.
0
.062 mmol) as yellow crystals after recrystallization with
1
acetone and hexane. H NMR (400 MHz, Acetone-d ) δ
6
9
.01 (dd, 2H, J = 8.3, 1.4 Hz), 8.68 (dd, 2H, J = 5.1, 1.4
19
Hz), 8.62 (dd, 2H J = 8.8, 2.6 Hz), 8.46 (s, 2H), 8.35 (dd,
F NMR (376 MHz, Acetone-d ) δ -63.69 (s, 6F), -72.68
6
2
7
H, J = 8.8, 1.8 Hz), 8.15 (dd, 2H, J = 8.3, 5.1 Hz), 7.92 –
.83 (m, 2H), 6.92 (ddd, 2H, J = 12.7, 9.3, 2.3 Hz), 6.08
(d, 6F, J = 707.3 Hz), -104.76 (dt, 2F, J = 11.9, 9.0 Hz), -
108.09 (td, 2F, J = 12.4, 2.4 Hz). P NMR (162 MHz,
31
1
3
(dd, 2H, J = 8.5, 2.3 Hz). C NMR (101 MHz, Acetone-
Acetone-d ) δ -131.17 – -157.37 (hept, J = 706.32 Hz).
6
d6) δ 167.7 (d, J = 6.8 Hz), 164.8 (dd, J = 209.3, 13.1 Hz),
LC/MS (m/z) calculated for C H F IrN 977.23 found
42
34 10
4
1
1
1
1
62.2 (dd, J = 212.7, 12.9 Hz), 154.7 (d, J = 7.3 Hz), 152.3,
46.8, 146.4 (q, J = 4.7 Hz), 139.7, 137.2, 131.9, 128.6,
27.4, 127.1 (dd, J = 4.5, 2.6 Hz), 125.2 (d, J = 34.9 Hz),
23.8 (d, J = 20.9 Hz), 114.7 (dd, J = 18.0, 3.0 Hz), 99.4
M+, 977.20.
4
db, the general procedure
C was followed using
iridium(III) chloride (89 mg, 0.30 mmol), 2-(2,4-
difluorophenyl)pyridine 2d (130 mg, 0.68 mmol) and a 2:1
mixture of 2-methoxyethanol/water (6 mL) to obtain the
dimer in 82% yield (150 mg, 0.12 mmol) as yellow solid.
1
9
(apparent t, J = 27.1 Hz). F NMR (376 MHz, Acetone-
d6) δ -63.68 (s, 6F), -72.66 (d, 6F, J = 707.3 Hz), -104.86
(
q, 2F J = 10.3, 9.3 Hz), -108.12 (td, 2F, J = 12.4, 2.7 Hz).
4
db was synthesized using the dimer (5b, 150 mg, 0.12
3
1
P NMR (162 MHz, Acetone-d ) δ -130.00 – -157.36
6
mmol), 2,2’-bipyridyl (34 mg, 0.22 mmol) and ethylene
glycol (6 mL). 4d was obtained in 57% yield (100 mg,
(hept, J = 701.46 Hz). Anal. Calcd for C H F IrN P: C,
3
6
18 16
4
4
1.83; H, 1.76; N, 5.42. Found: C, 41.96; H, 1.89; N, 5.23.
1
0
.11 mmol) as yellow solid. H NMR (400 MHz, Acetone-
LC/MS (m/z) calculated for C H F IrN 889.10 found
M+, 888.60.
3
6
18 10
4
d6) δ 8.89 (d, 2H, J = 8.1 Hz), 8.46 – 8.33 (m, 4H), 8.24
ddd, 2H, J = 5.4, 1.5, 0.6 Hz), 8.11 – 8.05 (m, 2H), 7.94
(
4
gb, the general procedure
C
was followed using
(ddd, 2H, J = 5.8, 1.5, 0.7 Hz), 7.77 (ddd, 2H, J = 7.6, 5.5,
1.2 Hz), 7.27 (ddd, 2H, J = 7.4, 5.9, 1.4 Hz), 6.78 (ddd, 2H,
iridium(III) chloride (178 mg, 0.60 mmol), 2-(2,4-
difluorophenyl)-5-(trifluoromethyl)pyridine 2g (352 mg,
1
3
J = 12.7, 9.3, 2.4 Hz), 5.82 (dd, 2H, J = 8.5, 2.4 Hz).
C
1
1
.4 mmol) and a 2:1 mixture of 2-methoxyethanol/water (
2 mL) to the obtain dimer in 74% yield (326 mg, 0.22
NMR (101 MHz, Acetone-d ) δ 164.8 (d, J = 7.1 Hz),
6
163.5 (dd, J = 39.4, 12.7 Hz), 163.5 (dd, J = 476.4, 12.7
Hz), 156.8, 155.6 (d, J = 6.6 Hz), 152.0, 150.8, 141.2,
140.8, 130.0, 128.9 (dd, J = 4.5, 2.8 Hz), 126.1, 125.2,
124.6 (d, J = 20.2 Hz), 114.7 (dd, J = 17.7, 3.0 Hz), 99.7
mmol) as yellow solid. 4gb was synthesized using the
dimer (100 mg, 0.067 mmol), 2,2’ bipyridyl (5b, 23 mg,
0
.15 mmol) and ethylene glycol (4 mL). 4b was obtained
19
in 78 % yield (105 mg, 0.10 mmol) as yellow-green solid.
(apparent t, J = 27.1 Hz). F NMR (376 MHz, Acetone-
1
H NMR (400 MHz, Acetone-d ) δ 9.01 (d, 2H, J = 7.6
d ) δ -72.67 (d, 6F, J = 707.2 Hz), -107.74 – -107.86 (m,
6
6
31
Hz), 8.64 (dd, 2H, J = 8.8, 2.5 Hz), 8.47 – 8.38 (m, 4H),
2F), -110.00 – -110.13 (m, 2F).
P NMR (162 MHz,
8
.31 (d, 2H, J = 5.3 Hz), 8.00 (s, 2H), 7.81 (t, 2H, J = 8
Acetone-d ) δ -131.16-157.38 (hept, J = 707.94 Hz).
6
Hz), 6.87 (ddd, 2H, J = 12.7, 9.3, 2.3 Hz), 5.98 (dd, 2H, J =
LC/MS (m/z) calculated for C H F IrN 729.13 found
M+, 728.55.
32
20
4
4
13
8
.5, 2.3 Hz). C NMR (101 MHz, Acetone-d ) δ 167.7 (d,
6
J = 6.9 Hz), 164.8 (dd, J = 210.8, 12.9 Hz), 162.2 (dd, J =
14.1, 12.9 Hz), 156.1, 155.2 (d, J = 7.0 Hz), 151.4, 146.2
q, J = 4.7 Hz), 140.7, 137.5 – 137.1 (m), 129.1, 126.9 (dd,
J = 4.3, 2.6 Hz), 125.7, 125.3, 123.9 (d, J = 21.0 Hz), 122.1
4
dc, the general procedure
C was followed using
2
(
iridium(III) chloride (89 mg, 0.29 mmol), 2-(2,4-
difluorophenyl)pyridine 2d (130 mg, 0.68 mmol) and a 2:1
mixture of 2-methoxyethanol/water (6 mL)to obtain the
dimer in 82% yield (150 mg, 0.12 mmol) as yellow solid.
(
d, J = 271.6 Hz), 114.5 (dd, J = 18.0, 3.0 Hz), 99.4
1
9
(apparent t, J = 27.1 Hz). F NMR (376 MHz, Acetone-
4
dc was synthesized using the dimer (126 mg, 0.10 mmol),
d ) δ -63.56 (s, 6F), -72.65 (d, 6F, J = 707.3 Hz), -104.62 –
6
4,4’-di-tbutyl-2,2’-bipyridyl (5c, 59 mg, 0.22 mmol) and
ethylene glycol (6 mL). 4e was obtained in 88% yield (174
mg, 0.18 mmol) as yellow solid. H NMR (400 MHz,
Acetone-d ) δ 8.79 (d, 2H, J = 1.8 Hz), 8.27 (d, 2H, J = 8.4
Hz), 7.98 – 7.90 (m, 4H), 7.76 – 7.72 (m, 2H), 7.62 (dd,
2H, J = 5.9, 2.0 Hz), 7.09 (ddd, 2H, J = 7.4, 5.9, 1.3 Hz),
6.64 (ddd, 2H, J = 12.6, 9.4, 2.4 Hz), 5.65 (dd, 2H, J = 8.6,
31
-
104.81 (m, 2F), -107.74 – -108.15 (m, 2F). P NMR (162
MHz, Acetone-d ) δ -131.24 – -157.38 (hept, J = 707.94
1
6
Hz). LC/MS (m/z) calculated for C H F IrN 865.10
3
4
18 10
4
6
found M+, 864.50.
4
gc, the general procedure
C was followed using
iridium(III) chloride (178 mg, 0.60 mmol), 2-(2,4-
difluorophenyl)-5-(trifluoromethyl)pyridine 2g (352 mg,
13
2.4 Hz), 1.28 (s, 18H). C NMR (101 MHz, Acetone-d ) δ
6
1
.4 mmol) and a 2:1 mixture of 2-methoxyethanol/water
164.6, 165.4 – 163.8 (m), 162.5 (dd, J = 37.2, 12.6 Hz),
160.1 (d, J = 12.8 Hz), 155.7, 155.2 (d, J = 6.2 Hz), 150.5,
149.6, 139.7, 125.8, 124.1, 123.6 (d, J = 20.5 Hz), 122.4,
113.6 (dd, J = 17.6, 2.9 Hz), 98.6 (apparent t, J = 27.2 Hz),
(12 mL) to obtain the dimer in 74% yield (326 mg, 0.22
mmol) as yellow solid. 4gc was synthesized using the
dimer (100 mg, 0.067 mmol), 4,4’-di-tbutyl-2,2’-bipyridyl
19
(
5c, 39 mg, 0.147 mmol) and ethylene glycol (4 mL). 4c
35.6, 29.5. F NMR (376 MHz, Acetone-d ) δ -72.61 (dd,
6
was obtained in 81% yield (121 mg, 0.11 mmol) as yellow
6F, J = 707.2, 8.6 Hz), -107.90 (q, 2F, J = 9.7 Hz), -110.17
1
31
solid. H NMR (400 MHz, Acetone-d ) δ 8.95 (d, 2H, J =
(t, 2F, J = 11.7 Hz). P NMR (162 MHz, Acetone-d ) δ -
6
6
1
8
6
.8 Hz), 8.63 (dd, 2H, J = 8.8, 2.6 Hz), 8.42 (dd, 2H, J =
.8, 1.9 Hz), 8.20 (d, 2H, J = 5.9 Hz), 7.85 – 7.81 (m, 4H),
.88 (ddd, 2H, J = 12.7, 9.3, 2.3 Hz), 5.98 (dd, 2H, J = 8.4,
130.58 – -157.12 (hept, J = 707.94 Hz). LC/MS (m/z)
calculated for C H F IrN 841.25 found M+, 840.60.
40
36
4
4

ACCEPTED MANUSCRIPT
3
1
4
cb, the general procedure
iridium(III) chloride (89 mg, 0.30 mmol), 2-(4-
fluorophenyl)pyridine 2c, and 2:1 mixture of 2-
C
was followed using
123.4, 121.9, 119.9, 114.1, 111.6, 56.6, 34.2, 31.0.
P
NMR (162 MHz, Acetone-d ) δ -130.19 – -157.39 (hept, J
= 707.94 Hz ). Anal. calcd for C H F IrN O P: C, 51.79;
6
a
42
44
6
4
2
methoxyethanol/water (6 mL) to obtain the dimer in 82%
yield (150 mg, 0.12 mmol) as yellow solid. 4f was
synthesized using the dimer (35 mg, 0.031 mmol), 2,2’-
bipyridyl (5b, 10.5 mg, 0.067 mmol) and ethylene glycol (5
H, 4.55; N, 5.75. Found: C, 51.61; H, 4.38; N, 5.94.
LC/MS (m/z) calculated for C H IrN O 829.31 found
M+, 828.70.
4
2
44
4
2
mL). 4cb was obtained in 94% yield (48 mg, 0.070 mmol)
ASSOCIATED CONTENT
Supporting Information
1
as yellow solid. H NMR(Acetone-d , 400 MHz): δ = 8.87
6
(
d, 2H, J=8.2 Hz), 8.33 (td, 2H, J=8.0, 1.6 Hz), 8.24 (d, 2H,
J=8.1 Hz), 8.17 (ddd, 2H, J=5.4, 1.5, 0.7 Hz), 8.05 – 7.95
m, 4H), 7.83 (ddd, 2H, J=5.8, 1.4, 0.7 Hz), 7.75 (ddd, 2H,
J=7.6, 5.5, 1.2 Hz), 7.23 – 7.14 (m, 2H), 6.84 (td, 2H,
Spectra, figures and tables of properties for the compounds.
This material is available free of charge via the Internet at
(
13
J=8.9, 2.6 Hz), 5.95 (dd, 2H, J=9.5, 2.6 Hz) ppm
C
AUTHOR INFORMATION
Corresponding Author
NMR(Acetone-d , 101 MHz): δ = 167.6, 166.0, 157.0,
6
1
1
1
54.5 (d, J=5.9 Hz), 151.9, 150.3, 141.5 (d, J=2.1 Hz),
40.9, 140.1, 129.8, 128.3 (d, J=9.4 Hz), 126.0, 124.7,
* E-mail for JDW: jimmie.weaver@okstate.edu
Notes
19
21.2, 118.4 (d, J=17.9 Hz), 110.7 (d, J=23.3 Hz) ppm
F
NMR(Acetone-d , 376 MHz): δ = -72.63 (d, 6F, J=707.4
The authors declare no competing financial interests.
6
3
1
Hz), -110.75 (s, 2F) ppm P NMR(Chloroform-d, 162
MHz): δ = -129.39 – -148.65 (m) ppm. Anal. calcd for
C H F IrN P: C, 45.88; H, 2.65; N, 6.69. Found: C,
ACKNOWLEDGMENT
32
22
8
4
Halliburton is gratefully acknowledged for its gift of a Parr
4
5.75; H, 7.48; N, 7.08. LC/MS (m/z) calculated for
Reactor.
Oklahoma State University is gratefully
C H F IrN 693.14 found M+, 692.60.
32
22
2
4
acknowledged for startup funds.
4
cc, the general procedure
iridium(III) chloride (89 mg, 0.31 mmol), 2-(4-
fluorophenyl)pyridine 2c, and 2:1 mixture of 2-
C was followed using
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[
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1
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ACCEPTED MANUSCRIPT
TSE kca/mol
Complex
λmax
473
475
476
476
481
488
507
516
518
525
528
528
540
556
560
E1/2Ox
V
E1/2Red
V
Egap eV
2.20
2.64
2.77
2.21
2.20
2.86
2.76
2.56
2.75
2.59
2.28
2.46
2.52
2.40
2.35
E1/2(Ir+/Ir*)
-0.97
-0.83
-1.00
-1.23
-1.27
-1.86
-1.65
-0.93
-1.97
-1.90
-1.59
-0.80
-1.04
-0.89
-1.18
E1/2(Ir*/Ir-)
0.97
1.39
1.42
0.39
0.62
0.73
0.63
1.14
0.55
0.32
0.25
1.14
1.07
1.03
0.85
4
gb
ga
60.4
60.2
60.1
60.1
59.4
58.6
56.4
55.4
55.2
54.5
54.2
54.2
53.0
51.4
51.1
1.23
1.81
1.77
0.98
0.93
1.00
1.11
1.63
0.78
0.69
0.70
1.66
1.49
1.51
1.17
-1.23
-1.25
-1.35
-1.82
-1.58
-2.13
-2.13
-1.42
-2.20
-2.27
-2.03
-1.32
-1.45
-1.37
-1.50
4
4
gc
3
d
h
3
3
c
3
b
4
dc
3
a
e
3
3
f
4
db
cc
cb
fd
4
4
4

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•
•
•
•
Synthesis of iridium photocatalysts directly from IrCl in 1 step and high yields
3
Determination of redox properties
Determination of triplet state energies
Spectral characterization

ACCEPTED MANUSCRIPT
Facile Synthesis and Complete Characterization of Homoleptic and Heteroleptic
Cyclometalated Iridium(III) Complexes for Photocatalysis
Anuradha Singh, Kip A. Teegardin, Kariate S. Prasad, Megan Kelly, Sadagopan Krishnan,
*
Jimmie D. Weaver
Department of Chemistry, Oklahoma State University, Stillwater, Oklahoma 74078
jimmie.weaver@okstate.edu
Supporting Information
Table of contents:-
I.
II.
Image of the Parr reactor system
Electrochemical data and calculations
Cyclic Voltamagrams of 3a-f, 3h and 4
NMR spectra
S2
S2
S3
S4
III.
IV.
S1

ACCEPTED MANUSCRIPT
Figure S1 Parr temperature controller model 4838
Electrochemical Measurements: Ground state redox potential of all complexes were
1
/2
1/2
determined (table S1) by CV. Measured Eox , Ered and Egap (value determined by CV) was
utilized to calculate excited state potentials using equation 2 and 3.
+
*
E Ir /Ir = E – E gap= (eq 2)
1/2 ox
1
/2
*
-
E1/2 Ir /Ir = E gap + E
(eq 3)
1/2 red
Table S1 Data from electrochemical measurements
TSE
E ox E red E gap
E
(Ir /Ir
E
1/2
1
/2
1/2
1/2
+
⃰
-
complex λmax Kcal/mol
V
V
eV
⃰
)
(Ir/Ir )
0.97
1.39
1.42
0.39
0.62
0.73
0.63
1.14
0.55
0.32
0.25
4
4
4
3
3
3
3
4
gb
ga
gc
d
h
c
b
dc
a
473
475
476
476
481
488
507
516
518
525
528
60.4
60.2
60.1
60.1
59.4
58.6
56.4
55.4
55.2
54.5
54.2
1.23
1.81
1.77
0.98
0.93
1.00
1.11
1.63
0.78
0.69
0.70
-1.23
-1.25
-1.35
-1.82
-1.58
-2.13
-2.13
-1.42
-2.20
-2.27
-2.03
2.20
-0.97
-0.83
-1.00
-1.23
-1.27
-1.86
-1.65
-0.93
-1.97
-1.90
-1.59
2.64
2.77
2.21
2.20
2.86
2.76
2.56
2.75
2.59
2.28
3
3
3
e
f
S2

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4
4
4
4
db
cc
cb
fd
528
540
556
560
54.2
53.0
51.4
51.2
1.66
1.49
1.51
1.17
-1.32
-1.45
-1.37
-1.50
2.46
2.52
2.40
2.35
-0.80
-1.04
-0.89
-1.12
1.14
1.07
1.03
0.85
Note: TSE=triplet state energy determined from emission spectra
Figure S2 Cyclic Voltammogram of 3a-3f, 3h (left) and 4ga-4fd (right)
S3

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H NMR spectrum of 3b
S4

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3
CNMR spectrum of 3b
S5

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9
FNMR spectrum of 3b
S6

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H NMR spectrum of 3c
S7

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3
CNMR spectrum of 3c
S8

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FNMR spectrum of 3c
S9

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H NMR spectrum of 3d
S10

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3
CNMR spectrum of 3d
S11

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9
FNMR spectrum of 3d
S12

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H NMR spectrum of 3e
S13