Unprecedented combination of regioselective hydrodefluorination and ligand exchange reaction during the syntheses of tris-cyclometalated iridium(iii) complexes

Article abstract of DOI:10.1039/c2dt32071a

The first reported combination of regioselective hydro-defluorination and a ligand exchange reaction during the syntheses of neutral iridium(iii) complexes is presented. Surprisingly, loss of one fluorine atom per ligand combined with a complete ligand exchange reaction on the transition metal were jointly observed during a bridge-splitting and substitution reaction of two different dimeric iridium(iii) precursor complexes with two different ancillary ligands. The regioselectivity of defluorination was evidenced in both cases. The reaction time was identified as a factor strongly impacting the kinetics of the thermally induced reaction. The Royal Society of Chemistry 2013.

Full text of DOI:10.1039/c2dt32071a

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PAPER
Unprecedented Combination of Regioselective Hydrodefluorination and
Ligand Exchange Reaction during the Syntheses of Tris Cyclometalated
Iridium (III) Complexes
Marc Lepeltier,a Frédéric Dumur,b,* Jérôme Marrot,a Emmanuel Contal,b Denis Bertin,b Didier Gigmesb
5
and Cédric R. Mayerc,*
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
DOI: 10.1039/b000000x
The first reported combination of regioselective hydroꢀdefluorination and a ligand exchange reaction
during the syntheses of neutral iridium (III) complexes is presented. Surprisingly, loss of one fluorine
10 atom per ligand combined with a complete ligand exchange reaction on the transition metal were jointly
observed during a bridgeꢀsplitting and substitution reaction of two different dimeric iridium (III)
precursor complexes with two different ancillary ligands. The regioselectivity of defluorination was
evidenced in both cases. The reaction time was identified as a factor strongly impacting the kinetic of the
thermally induced reaction.
heteroleptic iridium complex during both the device preparation
15 Introduction
and operation. Defluorination was assigned to a degradation of
the complex during vacuum sublimation.[5] However, a careful
50 insight of the authors also evidenced that a sideꢀproduct
presenting the loss of one fluorine atom was already detectable in
the nonꢀsublimed materials. If the loss of one fluorine atom was
clearly demonstrated, the regioselectivity of defluorination was
not so clearly established. More recently, an unprecedented
55 regiospecific monohydrodefluorination and decoordination of a
cinchonineꢀderived ligand during the synthesis of two
heteroleptic complexes was reported.[6] Defluorinatation of the
cinchocineꢀbased ligand was obtained for both as a side product
during the bridge splitting and substitution reactions of the
60 cinchocineꢀbased iridium dimer using acetylacetone and
dibenzoylmethane as the ancillary ligands. Surprisingly, if
defluorination and liberation of the ligand was evidenced during
the two syntheses, expected complexes were however obtained.
Since the evidence of induced hydrogen transfer from chlorinated
65 bridged iridium (III) dimer has been demonstrated,[7] a similar
and adapted approach was suggested. Formation of an
intermediate hydrido iridium complex from the solvent and
further iridium insertion into the CꢀF bond was suggested as a
possible mechanism to explain the regioselectivity of the fluorine
70 atom elimination.
During the past decade, intense research efforts have been
devoted to develop highly emissive lightꢀemitting devices using
heavyꢀmetal complexes and notably iridium (III) complexes.
Through the strong spin orbit coupling existing within all the
20 thirdꢀrow transition metal complexes, both singlet and triplet
excitons can be advantageously used to harvest light emission.[1]
The ongoing race towards lightꢀemitting devices of ever
improved performances requires the search for new emitters
combining enhanced light emission efficiencies and a wider range
25 of emission colors. Emission color can be finely tuned for a given
metal by varying the ligands and that substitution pattern.
Notably, destabilization of the LUMO level of neutral iridium
(III) complexes and blueꢀshifting color emission through the
introduction of electronꢀwithdrawing fluorine substituents is wellꢀ
30 described.[2] Synthesis of neutral trisꢀcyclometalated iridium
complexes often requires harsh reaction conditions to proceed so
that, through the years, several experimental procedures have
been developed.[3] These different synthetic routes have been
indifferently employed with both fluorinated and nonꢀfluorinated
35 ligands. The unique difference is iridium (III) precursor, IrCl3,
Ir(acac)3 or the chlorinated bridged dimer. Recently, thermallyꢀ
induced defluorination of a homoleptic iridium (III) complex
during
a
mer to fac isomerization has been reported.[4]
The three aforeꢀmentioned examples prompt us to report for the
first time an unprecedented combination of regioselective ligand
hydrodefluorination associated with a ligand exchange reaction
during the synthesis of a homoleptic and heteroleptic trisꢀ
75 cyclometalated iridium (III) complexes. Interestingly, this ligand
exchange reaction took place with the dichlorideꢀbridged iridium
Interestingly, upon heating at 290°C for 72 hours in glycerol, a
40 regioselective loss of fluorine on each of the ligands was
evidenced and the initial merꢀcomplex displaying six fluorine
atoms was isomerized to a new homoleptic facꢀcomplex where
only three fluorine atoms remained (see scheme 1). Removal of
all the fluorine atoms in ortho position of pyridine was observed.
45 Prior to that report, another regioselective thermal cleavage of a
fluorine group from one of the ligands was also observed on a
dimer [Ir2Cl2(piq)4] (piq
: 1ꢀphenylisoquinoline) and was
observed with two different fluorinated ligands : dfpiq (1ꢀ(2,4ꢀ
difluorophenyl)isoquinoline) and dfppy (1ꢀ(2,4ꢀdifluorophenyl)
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pyridine).
Ir(piq)2(dfppy) and Ir(piq)2(dfpiq) under the previous conditions
(heating at 210°C for 48 hours, glycerol as solvent). To our
35 surprise, completely different complexes from the expected ones
were isolated and the targeted heteroleptic complexes
Ir(piq)2(dfppy) and Ir(piq)2(dfpiq) were replaced by two
homoleptic complex whose structure was later identified as being
the complexes 1 and 2 in its facꢀform (see scheme 2).
Results and discussion
Firstly an unexpected reaction was observed during the synthesis
of the homoleptic complex Ir(dfpiq)3 which was attempted by
reacting 2,4ꢀdifluoroꢀphenylisoquinoline and [Ir2Cl2(dfpiq)4]
using the synthetic procedure reported by Thompson and coꢀ
workers.[3] Surprisingly, after heating the reaction mixture at
210°C for 48 hours, the targeted complex Ir(dfpiq)3 was not
obtained and a new complex 1 possessing only one fluorine atom
5
10 per ligand was isolated in 68% yield (see scheme 1).
Scheme 1 Complex 1 obtained during the defluorination process.
The presence of only one fluorine atom per ligand and its
1
replacement by one hydrogen atom was verified by H and 19F
40
15 NMR experiments (see Figure 1).
Scheme 2 Complexes 1 and 2 obtained during the defluorination process
and ligands exchange reaction.
The unusual character of this reaction was 2ꢀfold: firstly, a
45 complete ligand exchange occurred during heating and only the
presence of the incoming ligand used during the reaction was
observed in the final complex. Secondly, a regioselective
defluorination of the wellꢀknown dfppy or dfpiq was evidenced.
To the best of our knowledge, no defluorination or regioselective
50 defluorination of dfppy during synthesis has previously been
reported in the literature. In the two cases, formation of 1 and 2
results from a regioselective hydrodefluorination attributable to
the strong electronꢀwithdrawing effect exerted by the pyridine
100
80
60
40
chemical shift (ppm)
group upon complexation, therefore inducing
a
strong
9.0
8.5
8.0
7.5
7.0
6.5
55 polarization of the carbonꢀfluorine bond and weakening its
strength. The mechanisms of the ligand substitution reaction as
well as the CꢀF cleavage are still unclear. However, in light of the
previously suggested mechanism, the regioselectivity of the
Ir(III)ꢀmediated defluorination is only attributable to an iridium
60 insertion into the CꢀF bond of the cyclometalated ligand.
However, liberation of the defluorinated ligand was not observed
in our case.[6] Furthermore, Thompson described the synthesis of
the Ir(dfppy)3 starting from the dimer [Ir2Cl2(dfppy)4] and
dfppy.[3] The main product was the merꢀisomer, while the
65 monofluorinated Ir(fppy)3 was only isolated on its facꢀform. The
hydrodefluorination may have an important role in the mer to fac
isomerization process, but it still not clear if it isomerizes after
the CꢀF cleavage.
chemical shift (ppm)
1
Fig. 1 400 MHz H NMR spectrum in acetone d6 at 25 °C of complex 1.
inset : 19F NMR spectrum of 1 in acetone d6
1
Three additional protons were detected by H NMR whilst the
20 simplicity of the NMR spectrum also demonstrated that only the
fac isomer formed during the reaction. The presence of two sets
of doublets at 7.45 and 7.56 ppm respectively was consistent with
a selective defluorination of the aromatic ring in ortho position to
the pyridine ring. The detection of a singlet at 64.7 ppm in the 19
F
25 NMR spectrum undoubtedly evidenced the presence of a single
fluorine atom per ligand. The regioselectivity of defluorination
was verified by synthesizing 1ꢀ(4ꢀfluorophenyl)isoquinoline and
preparing the corresponding trisꢀcyclometalated complex. The
chemical shift of the singlet obtained by 19F NMR confirmed the
30 structure of the complex formed during defluorination. Intrigued
by these results, two new reactions were devoted this time to the
synthesis of two heteroleptic iridium (III) complexes
To study the substitution mechanism, the reaction time was
70 investigated as a parameter potentially influencing the structure
of the final complex (see Scheme 3). Interestingly, when heating
the dimer [Ir2Cl2(piq)4] with dfppy under different reaction times,
complexes corresponding to the progressive substitution of one
2
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initial piq ligand by an incoming one was evidenced. After 6 35 4). As anticipated, 1ꢀ(4ꢀfluorophenyl)isoquinoline provided the
hours, formation of the complex Ir(piq)2(fppy) was clearly shown
by mass spectroscopy.
targeted trifluorinated complex 1.
N
N
F
N
N
N
N
N
N
N
N
Cl
Cl
Ir
3
Ir
Ir
Ir
3
+
+
H
H
F
H
Ir
2
Ir
[Ir2Cl2(piq)4
]
F
K2CO3 glycerol,
210°C
K2CO3 glycerol,
210°C
12% yield
F
F
F
2
2
Ir(piq)2(fppy)
fac-2
f ac-3
2
formation shown by
Mass Spectroscopy
F
F
F
reaction time : 6 hours
24 hours
0
trace amount
18 %
fac-1
7.2 %
36 %
trace amount
0
48 hours
trace amount
N
5
Scheme 3 Kinetic investigations of the ligand exchange reaction.
F
N
N
N
Cl
Cl
The third ligand has been well introduced to the complex
structure and the orthoꢀfluorine has been removed. After 24 hours
two ligands are exchanged, furnishing the complex Ir(piq)(fppy)2
3 (see Fig. 2 and 3) with a trace amount of 2 and finally three
Ir
3
Ir
2
Ir
F
F
H
K2CO3 glycerol,
210°C
44% yield
2
10 ligands after 48 hours. Kinetic investigations therefore prove the
reaction time as being a determining factor on the number of
exchanged ligands without altering the defluorination process.
fac-4
Scheme 4 Thermal syntheses of complexes 1 and 4.
40 Unexpectedly however, fluorine was not detected in the final
complex Ir(piq)3 when starting from 1ꢀ(2ꢀ
4
fluorophenyl)isoquinoline (see Fig. 4).8 More importantly, the
presence of two fluorine atoms on the ligand is not required as
defluorination is also observed for monoꢀfluorinated ligand. The
45 determining factor of the reaction is the presence of the fluorine
atom in orthoꢀposition of the pyridine ring, therefore
demonstrating the regiospecificity of the defluorination process.
This last result paves the avenue for further investigations on all
the orthoꢀfluorinated ligands.
15
20
Fig. 2 XꢀRay crystal structures of facꢀ3 with thermal ellipsoids drawn at
25 the 30% probability level. Hydrogen atoms have been omitted for clarity.
-100
-75
-50
-25
0
25
chemical shift (ppm)
9.0
8.5
8.0
7.5
7.0
6.5
chemical shift (ppm)
50
Fig. 4 400 MHz 1H NMR spectrum in DMSO d6 at 25 °C of complex 4.
inset : 19F NMR spectrum of 4 in acetone d6
9.0
8.5
8.0
7.5
7.0
6.5
6.0
To summarize, during the course of our study, an unprecedented
chemical shift (ppm)
Fig. 3 300 MHz 1H NMR spectrum in CDCl3 at 25 °C of Ir(piq)(fppy)2 3
obtained after 24 hours of reaction
synthesis of the homoleptic trisꢀcyclometalated iridium(III)
55 complex 1 starting from three different dimer precursors was
developed : the first one consisted in the synthesis of the
complex using the conventional bridgeꢀsplitting and substitution
reaction of the dimer [Ir2Cl2(4fꢀpiq)4] with two equivalents of 4ꢀ
fpiq (see the scheme 5). The second one was based on the
60 hydrodefluorination process occurring during the bridgeꢀsplitting
and substitution reaction involving the dimer [Ir2Cl2(dfpiq)4] and
the ligand dfpiq. As the final procedure, the hydroꢀdefluorination
.
Finally, to determine the possible influence of the second fluorine
30 atom in metaꢀposition of the first one as well as to verify the
regioselectivity of the defluorination process, two monoꢀ
fluorinated ligands i.e. 1ꢀ(2ꢀfluorophenyl)isoquinoline (2fꢀpiq)
and 1ꢀ(4ꢀfluorophenyl)isoquinoline (4fꢀpiq) were synthesized and
complexed in the same conditions as previously used (see scheme
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35 Aesar and used as supplied commercially. 1ꢀphenylisoquinoline
was prepared according o a procedure previously reported in the
and ligand exchange reaction of [Ir2Cl2(piq)4] and dfpiq furnished
the complex 1.
litterature.[9]
1ꢀ(4ꢀfluorophenyl)isoquinoline[10]
and
1ꢀ(2ꢀ
fluorophenyl)isoquinoꢀline[11] were prepared by using
a
modification of literature procedures. All cyclometalated Ir(III)ꢀ
40 chloroꢀbridged [Ir2Cl2(L)4] (with L : ligand) were synthesized
according to the Nonoyama route, by refluxing IrCl3.3H2O with
2.2 equiv. of the targeted ligand in a 3:1 mixture of 2ꢀ
ethoxyethanol and water.[12] Iridium (III) dimer of 1ꢀ
phenylisoquinoline (piq) was prepared according to a reported
45 procedure.[13]
2. X-ray structure determination.
A single crystal of facꢀ3 was carefully selected, mounted onto a
cryoloop with the viscous oilꢀdrop method for the structure
determination by Xꢀray diffraction. Xꢀray intensity data were
50 collected on a Bruker X8ꢀAPEXꢀII CCD diffractometer by
monochromatized MoKα radiation (λ = 0.71073 Å) at 100(2)K. A
semiꢀempirical absorption was applied (ꢁ = 4.85 mmꢀ1, Tmin
=
0.511, Tmax = 0.953); a total of 30666 measured reflections in the
range h = ꢀ19 to 19, k = ꢀ18 to 22, l = ꢀ21 to 20 (θmax= 25.0°),
55 from which 2546 were unique (Rint = 0.055) and 2141 observed
according to the I > 2σ(I) criterion. Cell parameters were
calculated from 9415 reflections (θ = 2.2ꢀ25.0°). The structure
was solved by direct methods (SHELXS) and refined by
fullꢀmatrix least squares based on F2 (SHELXL97).[14] Hydrogen
60 atoms were fixed into idealized positions (riding model) and
assigned temperature factors Hiso(H) = 1.2 Ueq (pivot atom). The
refinement converged (ꢁ/σmax = 0.002) to R = 0.0305 for
observed reflections and wR(F2) = 0.0760, GOF = 1.04 for 265
parameters and all 2546 reflections. The final difference map
65 displayed no peaks of chemical significance (ꢁρmax = 1.88, ꢁρmin
= ꢀ1.66 e.Åꢀ3). CCDC 876293.
Conclusions
5
Three examples of cyclometalated iridium (III) complexes
prepared from defluorination reaction have been presented. If the
substitution of ligands has been clearly established during the
attempted synthesis of the heteroleptic complex, somewhat less
clear but equally intriguing is the mechanism enabling the
10 regioselective loss of the fluorine atoms. Defluorination can
however be assigned to a weakened carbonꢀfluorine bond arising
from the strong electronꢀwithdrawing effect exerted by the
complexed pyridine in the close proximity of the eliminated
fluorine atom. Defluorination process is observed on mono and
15 difluorinated ligands. These observations merit further
investigations into polyfluorinated iridium complexes as it
constitutes a major drawback for the generally adopted strategy
consisting to incorporate fluorine atoms on the cyclometalating
rings to blueꢀshift the emission of complexes. The synthesis of
20 complexes with orthoꢀfluorinated ligands has to be revisited.
3. Synthesis of ligands
3.1. 1-(4-fluorophenyl)isoquinoline (L1)
70 Tetrakis(triphenylphosphine)palladium (0) (0.43 g, 0.372 mmol)
was added to a mixture of 1ꢀchloroisoquinoline (1 g, 6.11 mmol),
4ꢀfluorobenzeneboronic acid (0.87 g, 6.20 mmol), toluene (27
mL), ethanol (13 mL) and an aqueous potassium carbonate
solution (2 M, 6.91 g in 25 mL water, 13 mL) under vigorous
75 stirring. The mixture was stirred at 80 °C for 48 h under a
nitrogen atmosphere. After cooling to room temperature, the
reaction mixture was poured into water and extracted with ethyl
acetate. The organic layer was washed with brine several times,
and the solvent was then evaporated. Addition of DCM followed
80 by pentane precipitated a white solid which was filtered off. The
residue was purified by column chromatography (SiO2,
pentane/DCM : 1/1 and pure DCM) and isolated as a white solid
Experimental
1. General Information.
Mass spectroscopy was performed by the Spectropole of Aixꢀ
Marseille University (Marseille). ESI mass spectral analyses were
25 recorded with a 3200 QTRAP (Applied Biosystems SCIEX) mass
spectrometer. The HRMS mass spectral analysis was performed
1
(1.25 g, 92 % yield). H NMR (400 MHz, CDCl3): δ 7.24ꢀ7.30
(m, 2H), 7.58 (td, 1H, J = 1.2 Hz, J = 9.7 Hz), 7.68ꢀ7.74 (m, 4H),
85 7.92 (d, 1H, J = 8.2 Hz), 8.10 (dd, 1H, J = 8.5 Hz, J = 0.6 Hz),
8.63 (d, 1H, J = 5.5 Hz) 13C NMR (100 MHz, CDCl3): δ 114.9 (d,
J = 21.5 Hz), 119.6, 126.1, 126.6, 126.7, 126.9, 129.6, 131.3 (d, J
= 8.2 Hz), 135.3 (d, J = 3.3 Hz), 136.4, 141.7, 159.1, 162.6 (d, J
= 248.0 Hz) 19F NMR (CDCl3): δ ꢀ113.1 HRMS (ESI MS) m/z:
90 theor: 224.0870 exp: 224.0870 ([M+H]+ detected)
with
a QStar Elite (Applied Biosystems SCIEX) mass
spectrometer. 1H and 13C NMR spectra were determined at room
temperature in 5 mm o.d. tubes on a Bruker Avance 400
30 spectrometer of the Spectropole : H (400 MHz) and 13C (100
1
1
MHz). The H chemical shifts were referenced to the solvent
peak: CDCl3 (7.26 ppm), and the 13C chemical shifts were
referenced to the solvent peak: CDCl3 (77.0 ppm). All starting
materials and solvents were purchased from Aldrich and Alfa
4
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3.2. 1-(2-fluorophenyl)isoquinoline (L2)
the mixture was then heated at reflux for 48 h under argon. The
60 solution was allowed to cool to room temperature, and the deep
red precipitate was collected on a glass filter frit. The precipitate
was washed with water and a mixture of pentane/ether : 4/1. The
red powder was dried under vacuum and used directly for the
next step without purification (712 mg, 89% yield). 1H NMR (400
65 MHz, DMSO d6): δ 5.16 (dd, 2H, J = 2.3 Hz, J = 9.6 Hz), 5.96
(dd, 2H, J = 2.3 Hz, J = 9.1 Hz), 6.77 (td, 2H, J = 1.4 Hz, J = 8.7
Hz), 6.89 (td, 2H, J = 2.4 Hz, J = 8.7 Hz), 7.55 (t, 2H, J = 8.8
Hz), 7.84ꢀ8.02 (m, 8H), 8.07ꢀ8.13 (m, 2H), 8.22ꢀ8.36 (m, 6H),
8.66 (d, 2H, J = 6.2 Hz), 8.84 (d, 2H, J = 8.5 Hz), 8.92 (d, 2H, J =
70 8.6 Hz), 9.51 (d, 2H, J = 6.5 Hz), 9.67 (d, 2H, J = 6.5 Hz) 19F
NMR (DMSO d6): δ ꢀ110.0, ꢀ108.9 HRMS (ESI MS) m/z: theor:
695.0648 exp: 695.0653 ([M+Na]+ detected)
Tetrakis(triphenylphosphine)palladium (0) (0.43 g, 0.372 mmol)
was added to a mixture of 1ꢀchloroisoquinoline (1 g, 6.11 mmol),
2ꢀfluorobenzeneboronic acid (0.87 g, 6.20 mmol), toluene (27
mL), ethanol (13 mL) and an aqueous potassium carbonate
solution (2 M, 6.91 g in 25 mL water, 13 mL) under vigorous
stirring. The mixture was stirred at 80 °C for 48 h under a
nitrogen atmosphere. After cooling to room temperature, the
10 reaction mixture was poured into water and extracted with ethyl
acetate. The organic layer was washed with brine several times,
and the solvent was then evaporated. Addition of DCM followed
by pentane precipitated a white solid which was filtered off. The
residue was purified by column chromatography (SiO2,
15 pentane/DCM : 1/1 and pure DCM) and isolated as a white solid
(1.06 g, 78% yield). 1H NMR (400 MHz, CDCl3): δ 7.21ꢀ7.26 (m,
1H), 7.32 (td, 1H, J = 1.1 Hz, J = 7.5 Hz), 7.46ꢀ7.57 (m, 3H),
7.67ꢀ7.71 (m, 2H), 7.80ꢀ7.83 (m, 1H), 7.89 (d, 1H, J = 8.2 Hz),
8.64 (d, 1H, J = 5.7 Hz) 13C NMR (100 MHz, CDCl3): δ 115.2 (d,
20 J = 21.8 Hz), 120.1, 123.8 (d, J = 3.5 Hz), 126.3, 126.5 (d, J = 2.0
Hz), 126.8 (d, J = 15.7 Hz), 126.81 (d, J = 2.0 Hz), 126.85, 129.6,
5
4.2. [Ir2Cl2(L2)4]
75
Iridium trichloride hydrate (0.42 g, 1.19 mmol) and 1ꢀ(2ꢀ
fluorophenyl)isoquinoline L2 (1.18 g, 5.31 mmol) were dissolved
in a mixture of 2ꢀethoxyethanol (10 mL) and water (2.5 mL), and
the mixture was then heated at reflux for 48 h under argon. The
130.1 (d, J = 8.0 Hz), 131.4 (d, J = 5.0 Hz), 135.7, 141.8, 155.4, 80 solution was allowed to cool to room temperature, and the deep
159.4 (d, J = 47.9 Hz) 19F NMR (CDCl3): δ ꢀ114.2 HRMS (ESI
MS) m/z: theor: 224.0870 exp: 224.0871 ([M+H]+ detected)
red precipitate was collected on a glass filter frit. The precipitate
was washed with water and a mixture of pentane/ether : 4/1. The
red powder was dried under vacuum and used directly for the
25
1
3.3. 1-(2,4-difluorophenyl)isoquinoline (L3)
next step without purification (504 mg, 63 % yield). H NMR
85 (400 MHz, DMSO d6): δ 5.02 (m, 2H), 5.91 (d, 2H, J = 7.4 Hz),
6.70ꢀ6.93 (m, 8H), 7.75 (t, 2H, J = 7.5 Hz), 7.80 (t, 2H, J = 7.8
Hz), 7.91 (t, 2H, J = 7.7 Hz), 7.95 (t, 2H, J = 7.2 Hz), 8.03 (d,
2H, J = 6.4 Hz), 8.15ꢀ8.28 (m, 10H), 9.50 (d, 2H, J = 6.4 Hz),
9.76 (d, 2H, J = 6.4 Hz) 19F NMR (DMSO d6): δ ꢀ97.9, ꢀ99.5
90 HRMS (ESI MS) m/z: theor: 695.0648 exp: 695.0650 ([M+Na]+
detected)
Tetrakis(triphenylphosphine)palladium (0) (0.43 g, 0.372 mmol)
was added to a mixture of 1ꢀchloroisoquinoline (1 g, 6.11 mmol),
30 2,4ꢀdifluorobenzeneboronic acid (0.98 g, 6.20 mmol), toluene (27
mL), ethanol (13 mL) and an aqueous potassium carbonate
solution (2 M, 6.91 g in 25 mL water, 13 mL) under vigorous
stirring. The mixture was stirred at 80 °C for 48 h under a
nitrogen atmosphere. After cooling to room temperature, the
35 reaction mixture was poured into water and extracted with ethyl
acetate. The organic layer was washed with brine several times,
4.3. [Ir2Cl2(L3)4]
and the solvent was then evaporated. Addition of DCM followed 95 IrCl3.3H2O (0.38 g, 1.077 mmol) and water (2.5 mL) were added
by pentane precipitated a white solid which was filtered off. The
residue was purified by column chromatography (SiO2,
40 pentane/DCM : 1/1 and pure DCM) and isolated as a white solid
(1.27 g, 86% yield). 1H NMR (400 MHz, CDCl3): δ 7.00 (td, 1H,
to a solution of 1ꢀ(2,4ꢀdifluorophenyl)isoquinoline L3 (1.16 g,
4.81 mmol) in 10 mL of 2ꢀethoxyethanol. The mixture was
refluxed at 120°C for a night. After cooling, the brown red
precipitated was filtered off, washed with water and dried in
J = 2.3 Hz, J = 9.6 Hz), 7.08 (td, 1H, J = 2.2 Hz, J = 8.4 Hz), 100 vacuum. It was used without any further purification (641 mg, 84
7.53ꢀ7.59 (m, 2H), 7.69ꢀ7.72 (m, 2H), 7.78 (dd, 1H, J = 2.9 Hz, J
= 8.5 Hz), 7.89 (d, 1H, J = 8.2 Hz), 8.63 (d, 1H, J = 5.7 Hz) 13C
45 NMR (100 MHz, CDCl3): δ 103.89 (t, J = 25.6 Hz), 111.5 (dd, J
= 3.7 Hz, J = 21.3 Hz), 120.5, 123.4 (dd, J = 3.9 Hz, J = 16.0
% yield). 1H NMR (400 MHz, DMSO d6): δ 4.67 (dd, 2H, J = 2.3
Hz, J = 8.8 Hz), 5.60 (dd, 2H, J = 2.5 Hz, J = 8.2 Hz), 6.81 (td,
2H, J = 2.3 Hz, J = 9.3 Hz), 6.93 (td, 2H, J = 9.3 Hz, J = 2.3 Hz),
7.75ꢀ7.85 (m, 5H), 7.92ꢀ8.00 (m, 5H), 8.07ꢀ8.10 (m, 3H), 8.16ꢀ
Hz), 126.6 (d, J = 2.4 Hz), 127.1, 127.3, 130.0, 132.57ꢀ132.77 105 8.30 (m, 11H), 9.43 (d, 2H, J = 6.5 Hz), 9.68 (d, 2H, J = 6.3 Hz)
(dd, J = 5.0 Hz, J = 10.7 Hz), 136.1, 142.1, 154.8, 160.0 (dd, J =
19F NMR (400 MHz, DMSO d6): δ ꢀ106.31 (dd, 4F, J = 12.3 Hz,
J = 442.8 Hz), ꢀ94.68 (dd, 4F, J = 12.3 Hz, J = 581.7 Hz) HRMS
(ESI MS) m/z: theor: 731.0459 exp: 733.0451 ([M+Na]+
detected)
11.9 Hz, J = 250.7 Hz), 163.2 (dd, J = 11.3 Hz, J = 250.0 Hz) 19
50 NMR (CDCl3): δ ꢀ109.5 (d, J = 8.3 Hz), ꢀ108.8 (d, J = 8.2 Hz)
F
HRMS (ESI MS) m/z: theor: 242.0776 exp: 242.0775 ([M+H]+
detected)
110
4.4. [Ir2Cl2(piq)4]
4. Synthesis of iridium (III) dimers
4.1. [Ir2Cl2(L1)4]
To a suspension of 1ꢀphenylisoquinoline (0.5 g, 2.44 mmol) in 2ꢀ
ethoxyethanol / water (75 : 25, 40 mL) was added IrCl3.3H2O
55
Iridium trichloride hydrate (0.42 g, 1.19 mmol) and 1ꢀ(4ꢀ
fluorophenyl)isoquinoline L1 (1.18 g, 5.31 mmol) were dissolved
in a mixture of 2ꢀethoxyethanol (10 mL) and water (2.5 mL), and
115 (0.24 g, 0.7 mmol). The reaction mixture was stirred at reflux for
24h. Then, water (50 mL) was added and the product was filtered,
washed, with ethanol and diethyl ether. The product was then
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= 2.8 Hz, J = 8.8 Hz), 7.12 (d, 3H, J = 6.3 Hz), 7.30 (d, 3H, J =
consistent with those previously reported in the reference 13. H 60 6.3 Hz), 7.64ꢀ7.68 (m, 6H),7.72ꢀ7.75 (m, 3H), 8.17 (dd, 3H, J =
isolated as a red powder (0.425 g, 96 % yield). NMR data are
1
3
NMR (300 MHz, CDCl3): δ 6.05 (d, 4H, J = 7.2 Hz), 6.52 (d,
4H, 3J = 6.9 Hz), 6.57 (d, 4H, 3J = 6.6 Hz), 6.83 (t, 4H, 3J = 8.1
Hz), 7.78 (m, 4H), 7.86 (m, 8H), 8.14 (d, 4H, 3J = 7.8 Hz), 8.99
(d, 4H, 3J = 8.4 Hz), 9.06 (d, 4H, 3J = 6.3 Hz)
5.2 Hz, J = 8.8 Hz), 8.87ꢀ8.89 (m, 3H) 13C NMR (400 MHz,
CDCl3): δ 107.2 (d, J = 23.5 Hz), 120.2, 122.4 (d, J = 16.1 Hz),
126.2, 127.0, 127.2, 130.3, 131.7 (d, J = 8.8 Hz), 136.6, 139.4,
141.4, 162.6, 165.1, 166.3, 167.2, 167.3 19F NMR (CDCl3): δ ꢀ
5
1
65 110.73 (s) H NMR (400 MHz, acetone d6): δ 6.59 (dd, 3H, J =
2.8 Hz, J = 10.4 Hz), 6.71 (td, 3H, J = 2.8 Hz, J = 8.9 Hz), 7.43
(d, 3H, J = 6.4 Hz), 7.54 (d, 3H, J = 6.0 Hz), 7.76ꢀ7.84 (m,
6H),7.91ꢀ7.95 (m, 3H), 8.31 (dd, 3H, J = 5.2 Hz, J = 8.8 Hz),
8.96ꢀ9.00 (m, 3H) 19F NMR (acetone d6): δ 64.68 (s) HRMS (ESI
70 MS) m/z: theor: 860.1859 exp: 860.1858 ([M+H]+ detected) )
UV/vis absorption (CH2Cl2): λmax = 284, 316, 348 (sh), 403, 448
nm, PL (CHCl3): λmax = 599 nm (λexc = 380 nm).
5. Synthesis of tris-cyclometalated iridium (III) complexes
5.1.1. Direct synthesis of tris(1-(4-fluorophenyl)isoquino-
10 linato-C2,N)iridium (III) (1)
A mixture of iridium dimer [Ir2Cl2(L1)4] (0.418 g, 0.311 mmol),
1ꢀ(4ꢀfluoroꢀphenyl)isoquinoline L1 (0.174 g, 0.777 mmol) and
K2CO3 (0.258 g, 1.86 mmol) were heated to 210 °C under inert
15 atmosphere in 6 mL of glycerol for 48 h. After the mixture was
cooled to room temperature, 20 mL of deionized water was
added, and the resulting precipitate was filtered off, washed with
two portions of deionized water and airꢀdried. The solid was
chromatographied on silica gel using DCM as the eluent and
20 eluted as the first band. After evaporation of the volatiles,
addition of a minimum of DCM and addition of pentane
precipitated a light red solid which was filtered off and dried
under vacuum. For a higher purity, a second chromatography
(SiO2, pentane: DCM : 1/1) was carried out. The product 1 was
25 isolated as a redꢀorange powder (64 mg, 12 % yield).
5.2. Synthesis of tris(2-(4-fluorophenyl)pyridinato)iridium
75 (III) (2) by defluorination
To a suspension of the dimer [Ir2Cl2(piq)4] (100 mg, 0.0786
mmol) in glycerol (30 mL) was added 2ꢀ(2,4ꢀ
difluorophenyl)pyridine (45 mg, 0.236 mmol) and sodium
80 carbonate (0.100 g, 0.943 mmol). The reaction mixture was
stirred at reflux for 24h. Then, water (50 mL) was added and the
product was filtered, and purified by column chromatography on
silica gel eluting with
a
gradient of ethyl acetate
/
dichloromethane / petroleum ether (from 0:1:4 to 2:1:2) to afford
85 2 identified fractions : facꢀIr(piq)(fppy)2 fac-3 (red powder, 21
mg, 18 %) and facꢀIr(fppy)3 fac-2 (yellowish powder, 8 mg, 7.2
%).
5.1.2. Synthesis of tris(1-(4-fluorophenyl)isoquinolinato-
C2,N)iridium (III) (1) by defluorination
1
fac-Ir(fppy)3 (fac-2): H NMR (300 MHz, CDCl3): δ 6.46 (dd,
30 A mixture of iridium dimer [Ir2Cl2(L3)4] (0.44 g, 0.311 mmol), 1ꢀ
(2,4ꢀdifluoroꢀphenyl)isoquinoline L3 (187 mg, 0.777 mmol) and
K2CO3 (0.258 g, 1.86 mmol) were heated to 210 °C under inert
atmosphere in 6 mL of glycerol for 48 h. After the mixture was
cooled to room temperature, 20 mL of deionized water was
35 added, and the resulting precipitate was filtered off, washed with
two portions of deionized water and airꢀdried. The solid was
chromatographied on silica gel using DCM as the eluent and
eluted as the first band. After evaporation of the volatiles,
addition of a minimum of DCM and addition of pentane
40 precipitated a light red solid which was filtered off and dried
under vacuum (152 mg, 68 % yield).
3H, 3J = 10.5 Hz, 4J = 2.7 Hz), 6.62 (dt, 3H, 3J = 8.4 Hz, 4J = 2.7
90 Hz), 6.89 (t, 3H, 3J = 6.3 Hz), 7.48 (d, 3H, 3J = 5.1 Hz), 7.62 (m,
6H), 7.86 (d, 3H, 3J = 8.4 Hz), HRMS (ESI MS) m/z:
theor: 709.1317 exp: 709.1337 ([M]+. detected). UV/vis
absorption (CH2Cl2): λmax = 278, 353, 392 (sh) nm, PL (CHCl3):
λmax = 483 nm (λexc = 380 nm).
95
1
fac-Ir(piq)(fppy)2 (fac-3): H NMR (300 MHz, CDCl3): δ 6.36
(dd, 1H, 3J = 10.5 Hz, 4J = 3.0 Hz), 6.50 (dd, 1H, 3J = 10.5 Hz, 4J
= 2.7 Hz), 6.61 (m, 2H), 6.78 (m, 1H), 6.93 (m, 2H), 7.04 (m,
2H), 7.21 (d, 1H, 3J = 6.3 Hz), 7.33 (d, 1H, 3J = 5.4 Hz), 7.42 (d,
100 1H, 3J = 6.0 Hz), 7.49 (d, 1H, 3J = 5.4 Hz), 7.62 (m, 6H), 7.82 (m,
3H), 8.21 (d, 1H, 3J = 8.1 Hz), 8.98 (m, 1H). HRMS (ESI MS)
m/z: theor: 741.1568 exp: 741.1603 ([M]+. detected). UV/vis
absorption (CH2Cl2): λmax = 281, 322, 350, 399, 457 nm, PL
(CHCl3): λmax = 609 nm (λexc = 380 nm).
45 5.1.3. Synthesis of tris(1-(4-fluorophenyl)isoquinolinato-
C2,N)iridium (III) (1) by defluorination and ligand exchange
105
fac-Ir(piq)2(fppy): HRMS (ESI MS) m/z: theor: 773.1818 exp:
773.1830 ([M]+. detected).
By changing the time of reaction to 48 h, the main identified
compounds were obtained: facꢀIr(piq)(fppy)2 (fac-3) (traces) and
110 facꢀIr(fppy)3 (fac-2) (yellowish powder, 40 mg, 36 %)
A mixture of iridium dimer [Ir2Cl2(piq)4] (0.100 g, 0.0786 mmol),
1ꢀ(4ꢀfluoroꢀphenyl)isoquinoline L1 (47 mg, 0.196 mmol) and
50 K2CO3 (0.108 g, 0.786 mmol) were heated to 210 °C under inert
atmosphere in 10 mL of glycerol for 72 h. After the mixture was
cooled to room temperature, 20 mL of water was added, and the
resulting precipitate was filtered off, washed with two portions of
deionized water and airꢀdried. The solid was then purified by
55 column chromatography on silica gel eluting with a gradient of
dichloromethane / petroleum ether (from 0:1 to 1:1). The product
was isolated as a red powder (16 mg, 29 %).1H NMR (400 MHz,
CDCl3): δ 7.60 (dd, 3H, J = 2.8 Hz, J = 10.0 Hz), 7.68 (td, 3H, J
5.3.1. Direct synthesis of tris(1-phenylisoquinolinato-C2,N)
iridium (III) (4)
115 A mixture of iridium dimer [Ir2Cl2(piq)4] with piq : 1ꢀphenylꢀ
isoquinoline (0.71 g, 0.558 mmol), 1ꢀphenylisoquinoline (300
mg, 1.462 mmol) and K2CO3 (0.60 g, 4.34 mmol) were heated to
6
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65
70
5
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Synthesis
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tris(1-phenylisoquinolinato-C2,N)
iridium (III) (4) by defluorination
80
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20 K2CO3 (0.258 g, 1.86 mmol) were heated to 210 °C under inert
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85
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1
reported in references 8 and 15. H NMR (400 MHz, CDCl3): δ
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100
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Notes and references
a Institut Lavoisier de Versailles ILV – UMR CNRS 8180, Université de
Versailles SaintꢀQuentin en Yvelines, 45 avenue des Etats Unis, Fꢀ78035
40 Versailles, France.
b AixꢀMarseille Université, CNRS, Institut de Chimie Radicalaire ICR –
UMR 7273, Fꢀ 13397 Marseille Cedex 20 – France. Fax: (+33) 4 91 28
87 58; Tel: (+33) 4 91 28 27 48; Eꢀmail: frederic.dumur@univꢀamu.fr
c Laboratoire d’Ingénierie des Systèmes de Versailles LISV – EA 4048,
45 Université de Versailles Saint Quentin en Yvelines, 10/12 avenue de
l’Europe, Fꢀ78140 Vélizy – France. Tel: (+33) 1 39 25 43 78; Eꢀmail:
cedric.mayer@lisv.uvsq.fr
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