Easy separation of Δ and Λ isomers of highly luminescent [IrIII]-cyclometalated complexes based on chiral phenol-oxazoline ancillary ligands

Article abstract of DOI:10.1002/chem.201200709

A new class of neutral cyclometalated iridium(III) complexes with enantiomerically pure C₁-symmetric phenol-oxazolines (3 a,b) have been synthetized in high yields and fully characterized. Resolution of the corresponding Δ_R and Λ_R or Δ_S and Λ_S isomers was easily achieved by conventional flash chromatography. The corresponding Δ and Λ helicities have been confirmed by CD spectroscopy and X-ray crystallography. Regarding the absorption and luminescence properties with unpolarized light, no significant difference between Δ and Λ isomers has been observed. A strong blue luminescence is observed for deaerated solutions of complexes 5 a and 5 b in CH₃CN. Copyright

Full text of DOI:10.1002/chem.201200709

FULL PAPER
DOI: 10.1002/chem.201200709
Easy Separation of D and L Isomers of Highly Luminescent [IrIII]-
Cyclometalated Complexes Based on Chiral Phenol-Oxazoline Ancillary
Ligands
Enrico Marchi, Riccardo Sinisi, Giacomo Bergamini, Michele Tragni, Magda Monari,*
Marco Bandini,* and Paola Ceroni*[a]
Abstract: A new class of neutral cyclo-
metalated iridium(III) complexes with
tional flash chromatography. The corre-
sponding D and L helicities have been
confirmed by CD spectroscopy and X-
ray crystallography. Regarding the ab-
sorption and luminescence properties
with unpolarized light, no significant
difference between D and L isomers
has been observed. A strong blue lumi-
nescence is observed for deaerated sol-
utions of complexes 5a and 5b in
CH3CN.
ACHTUNGTRENNUNG
enantiomerically pure C1-symmetric
phenol-oxazolines (3a,b) have been
synthetized in high yields and fully
characterized. Resolution of the corre-
sponding DR and LR or DS and LS iso-
mers was easily achieved by conven-
Keywords: circular dichroism · chi-
ral ligands · iridium · phosphores-
cence
Introduction
ligand charge-transfer (MLCT) state with the introduction
of a third ligand that is easy to reduce (lower LUMO), or
by using a third ligand with a low-energy ligand-centered
(LC) triplet.[12,13] Despite much effort, however, tuning of
the emission of complexes of general formula [Ir-
Cyclometalated [IrIII] complexes have attracted increasing
interest over the last decade because of their phosphores-
cent properties:[1] band maximum tunable across the visible
region, an emission quantum yield that approaches the theo-
retical limit of 1 under proper experimental conditions, and
a relatively short lifetime of the lowest triplet excited state
(t=1–10 ms).[2] These photophysical properties are ideal in
view of application of these complexes as 1) sensors of tem-
perature,[3] oxygen,[4] and metal ions;[5] 2) biological
probes;[6] 3) electrochemiluminescent markers;[7] 4) light-
emitting electrochemical cells;[8] 5) hydrogen generators[9]
and emitters in organic light-emitting diodes (OLEDs and
WOLEDs).[10]
AHCTUNGTRENNUNG
(F2ppy)2(LL)][14] (LL=an ancillary ligand) towards energies
higher than about l=450 nm has been unsuccessful. This is
3
probably due to the fact that the lowest LC of the F2ppy
ligand lies in this spectral region and cannot be substantially
perturbed by the nature of the third ligand, the presence of
a larger number of F substituents, or the presence of elec-
tron-donating groups on the pyridine moiety of the ppy-type
ligand.
Focusing on the developments in the area of functional-
ized cyclometalated [IrIII] complexes, efforts have recently
been made towards the isolation of stereochemically defined
cyclometalated iridium complexes as emitters of circularly
polarized luminescence.[15] This interest is also founded on
the possibility of accomplishing “…propagation of chiral in-
formation…in materials or supramolecular assemblies…”,[16]
based on chiral transfer in coordination complexes.
Of these applications, the last is the most extensively in-
vestigated for neutral complexes, and much effort has been
devoted to obtaining sky-blue and stable [IrIII] phosphores-
cent complexes. The archetype complex is [Ir
(ppy=2-phenyl pyridyl), which displays a green phosphores-
cence. Modification of the [Ir(ppy)3] complex to move the
(ppy)3][11]
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
emission band to lower energies is not difficult and can be
achieved by either lowering the energy of the metal-to-
Despite this growing interest, the synthesis and characteri-
zation of enantiomerically pure phosphorescent organome-
tallic complexes have not been fully developed. Resolution
of stereoisomeric mixtures of [IrIII] complexes into the cor-
responding L and D isomers is still an open task and elegant
solutions in this direction have been accomplished by 1) co-
crystallization of cationic complexes with a proper chiral
counterion;[17] 2) liquid chromatography with a chiral sta-
tionary phase;[15,18] and 3) synthetic predetermination of the
helicity about the metal center, as demonstrated for chiral
pinene-phenyl pyridine ligands.[19]
[a] Dr. E. Marchi, Dr. R. Sinisi, Dr. G. Bergamini, Dr. M. Tragni,
Prof. Dr. M. Monari, Prof. Dr. M. Bandini, Prof. Dr. P. Ceroni
Dipartimento di Chimica “G. Ciamician”
Alma Mater Studiorum, Universitꢀ di Bologna
via Selmi 2, 40126 Bologna 40126 (Italy)
Fax : (+39)051-2099456
E-mail: magda.monari@unibo.it
marco.bandini@unibo.it
paola.ceroni@unibo.it
Herein, we report on the synthesis and easy separation of
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201200709.
diastereomerically pure D and L cyclometalated [IrIII] iso-
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mers by simply introducing enantiomerically pure ancillary
ligands. In detail, our approach consists of the condensation
of chloro-bridged iridiumACTHNUTRGENUGN(III) complexes with chiral
phenol–oxazolines (hereafter abbreviated as phox li-
gands),[20] which results in the formation of diastereoisomer-
ic DRLR or DSLS mixtures depending on the absolute config-
uration of the phox ligand.[21]
Scheme 1. Synthesis of chiral ancillary phox ligands 3a,b.
Phenol–oxazolines 3 were chosen as the ancillary ligands
based on their ready synthetic availability in enantiomeri-
cally pure form, chelating nature, and strong affinity for
hard transition metal salts. Last but not least, phox ligands
can be subjected to further chemical manipulations with
a view to potential applications of these complexes as lumi-
nescent sensors to discriminate enantiomers and biological
markers.
lating ligands in an ethoxyethanol/water mixture (3:1) at
reflux.[24] Dimers 4a and 4b were then efficiently coupled
with phox ligands 3a,b in good yields. In particular, when
complexes 4a and 4b were treated with a slight excess of
oxazoline ligands in the presence of Na2CO3, complexes 5a–
d were isolated as bright-yellow solids in good yields (61–
78%, Scheme 2). Interestingly, the isomers proved to be
As a proof of concept, four neutral complexes with the
general formula [IrACHTUNGTRENNUNG(C^N)2HCATUNGTRENN(UGN O^N)], in which C^N (cyclome-
talating ligand) is ppy or F2ppy and O^N (ancillary ligand)
is phox ((S)-3a) or the corresponding fluoro derivative
Fphox ((R)-3b), have been synthesized. Each complex was
separated by conventional flash chromatography into the
corresponding D and L isomers and unambiguously charac-
terized by using single-crystal X ray crystallography and cir-
cular dichroism. Moreover, we report here on the photo-
physical and electrochemical properties of these complexes
Scheme 2. Collection of neutral cyclometalated [IrIII] complexes 5a–d.
(dr=diastereomeric ratio, determined by HPLC on the crude reaction
products). Yields refer to the sum of the diastereoisomers.
as compared with the known complex [IrACTHUNTRGENN(UG F2ppy)2ACHTUNGTERN(NUGN acac)]
(acac=acetylacetonate).[22]
Results and Discussion
isolable in diastereoisomerically pure form through conven-
tional flash chromatography on silica gel (see the Experi-
mental Section). The stereochemical combinations DR and
LS were the more polar isomers within each pair of iridium
complexes, and were eluted first from the flash chromatog-
raphy columns on silica gel (see below for structural deter-
mination). This experimental evidence could constitute a val-
uable preliminary working model to predict the absolute ste-
reochemistry of the Ir center within this class of chiral cyclo-
metalated transition-metal complex.
Synthesis: Enantiomerically pure phox ligands (S)-3a and
(R)-3b were readily obtained by following known methodol-
ogies.[23] In particular, condensation of commercially avail-
able 2-hydroxybenzonitrile (1a) or 3-fluoro-2-hydroxyben-
zonitrile (1b) with enantiomerically pure (S or R)-phenyl
glycinol (2), in the presence of a catalytic amount of anhy-
drous ZnCl2 (2.5 mol%), gave the desired phox (3a) and
Fphox (3b) in 68 and 40% yield, respectively (Scheme 1).
The dimeric chloro-bridged iridiumACHTUNGTREN(NUNG III) complexes
[(C^N)2Ir(m-Cl)2Ir(C^N)2] (C^N=ppy (4a), C^N=F2ppy
(4b)) were synthesized by following the known procedure,
through the condensation of IrCl3·3H2O with the cyclometa-
G
E
X-ray crystallography: The molecular structures of one of
the two isomers of 5a, 5b, and 5d are shown in Figure 1,
and selected bond lengths and angles are reported in
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Highly Luminescent [IrIII]-Cyclometalated Complexes
FULL PAPER
Table S1 in the Supporting Information. Two independent
molecules are present in the asymmetric units of 5a and 5b.
In the three cyclometalated complexes, the [IrIII] center
shows a distorted octahedral environment that is coordinat-
ed by two identical ppy or F2ppy ligands and by a third bi-
dentate ligand, which is the enantiomerically pure phenol
oxazoline (phox or Fphox).
The absolute configuration at the metal centers has been
unambiguously determined by X-ray crystallography as D
for 5a and L for 5b and 5d, respectively. Taking into ac-
count the enantiomer of the phenol-oxazoline ligand, the
configurations of the complexes are DR, LS, and LS, for the
investigated isomers of 5a, 5b, and 5d, respectively. The ppy
or F2ppy ligands are arranged with the pyridine N atoms
lying in a trans position to each other whereas the s-bound
C atom is trans to the N atom of the oxazoline ring. A simi-
lar ligand disposition has been found, for example, in [Ir-
A
(pic)] (pic=2-pyridinecarboxylato).[25] In all three
2ACHTUNGTRENNUNG
ꢀ
AHCTUNGTRENGN(UN pyridine) bonds are very close to
each other in length (range 1.99–2.04 ꢂ) and shorter than
ꢀ
the Ir N(oxazoline) bond (range 2.09–2.17 ꢂ). This trend,
which has been already observed in the aforementioned [Ir-
(pic)] complex and related complexes,[25] is ascribed to
ACHUTNRGEN(NUG ppy)2ACHTUNGTRENNUGN
the trans influence of the C atom belonging to the phenyl
unit of ppy or F2ppy.
The oxazoline ring at the asymmetric 5-position features
a phenyl group that is aligned almost parallel to one of the
ppy or F2ppy ligands. This orientation of the phenyl ring
both alleviates the high steric crowding around the Ir cen-
ters and establishes intramolecular p–p interactions. This
feature has been observed in trischelate complexes with sub-
stituted polypyridyl ligands.[26] In the crystal packing of 5a,
intermolecular p–p interactions involving aromatic rings al-
ready engaged in intramolecular p–p interactions generate
stacks of molecules running along the b axis, together with
clathrated molecules of CH2Cl2 solvent (Figure S1 in the
Supporting Information). Interestingly, these stacks of mole-
cules are formed by only one of the two conformers of 5a;
therefore, half of the columns are formed by one conformer
and half are formed by the second conformer (Figure S2 in
the Supporting Information). A similar arrangement of mol-
ecules in columns held together by intermolecular p–p inter-
actions is also observed in the crystal packing of 5d (Fig-
ures S3 and S4 in the Supporting Information), in which
there is one independent molecule and no solvent. In fact,
in addition to the aforementioned p–p stacking in 5d, there
ꢀ
are also C H···p interactions between one methylenic hy-
drogen of the oxazoline ring and a phenyl unit of the ppy
ligand that is not involved in p–p interactions, which
strengthens the intermolecular interactions along the col-
ꢀ
umns of 5d, and C H···p interactions connecting columns of
molecules. The crystal packing of 5b (Figure S6 in the Sup-
porting Information) does not resemble that of 5a or 5d be-
cause similar intermolecular p–p stacks are not present. The
two independent molecules of 5b form p–p interactions that
involve the pyridine ring of the F2ppy ligand already engag-
ed in a intramolecular p–p interaction and the F2ppy ligand
Figure 1. Molecular structure of a) DR-5a, b) LS-5b, and c) LS-5d.
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P. Ceroni, M. Monari, M. Bandini et al.
Table 1. Absorption and emission properties in deaerated and air-equilibrated (given in brackets) CH3CN at 298 K and in CH2Cl2/CHCl3 (1:1 v/v) rigid
matrix at 77 K for the investigated [IrIII] complexes 5a–d (mixture of isomers) compared with [Ir
kq is the quenching constant by dioxygen at 298 K.
ACHUTGTNERNNUG(F2ppy)ACHTUNTGREN(NUNG acac)] under the same experimental conditions.
Absorption
eꢃ103 [mꢀ1 cmꢀ1
Emission
Rate
298 K
l [nm]
298 K
l [nm]
77 K
l [nm]
constants
]
t [ms]
Fem
t [ms]
kq ꢃ1010 [mꢀ1 sꢀ1
]
5a
5b
5c
5d
232
43.7
7.3
5
42.1
6.9
6
497
504
520
1.8 (3.1ꢃ10ꢀ2
)
)
)
)
0.81 (0.01)
468
468
494
2.7
1.6
1.6
2.0
332[a]
385[a]
227
2.1 (3.1ꢃ10ꢀ2
1.9 (2.5ꢃ10ꢀ2
1.9 (2.6ꢃ10ꢀ2
0.80 (0.01)
2.7
3.4
332
377
235[a]
283[a]
344
37.7
22
0.51 (0.008)
6.5
32.8
6.8
43.5
10.8
4.9
257
347
524
487
0.52 (0.008)
0.50 (0.016)
494
469
3.4
2.8
1.9
1.6
[Ir
(F2ppy)
(acac)]
248
0.86 (3.1ꢃ10ꢀ2
)
325[a]
383
[a] Shoulder of the absorption band.
of the other conformer (Figure S5 in the Supporting Infor-
mation). The crystal packing is also reinforced by slipped
ꢀ
p–p interactions of a different type and by C H···p interac-
tions.
Photophysical properties: The absorption and emission
spectra (Table 1, Figures 2 and 3) were initially recorded for
the diasteroisomeric mixture indicated in Scheme 2. For
Figure 2. Absorption spectra of 5a (c) and 5c (a) in CH3CN solu-
tion at 298 K.
Figure 3. Emission spectra of a) 5a and b) 5c in CH3CN at 298 K (c),
and in CH2Cl2/CHCl3 (1:1 v/v) at 298 K (d) and 77 K (a). lex
=
290 nm (the equimolar mixture of diastereoisomers was analyzed in each
case).
a discussion of the properties of each diastereoisomer, see
below. The absorption spectra of 5a and 5c in CH3CN
(Figure 2) show broad bands, quite similar to those of the
The lowest energy, very weak band is probably due to a tran-
sition from the ground state to the lowest MLCT state. Ac-
3
corresponding homoleptic complexes [Ir(F2ppy)3] and [Ir-
G
A
cording to literature reports,[12] in complexes containing
phenyl-pyridyl ligands, the highest occupied molecular orbi-
tal (HOMO) is mainly located on the metal, with a contribu-
tion from the anionic phenyl ring of the ligand. Conversely,
the lowest unoccupied molecular orbital (LUMO) is mostly
to spin-allowed LC transitions of the phenyl-pyridyl ligands,
which partially overlap with spin-allowed LC transition of
the ancillary ligand, whereas the less intense bands above
300 nm are probably due to spin-allowed MLCT transitions.
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Highly Luminescent [IrIII]-Cyclometalated Complexes
FULL PAPER
located on the pyridyl ring of the ligand. However, it is
worth remembering that in [IrIII] cyclometalated complexes
both the localized molecular orbital and the spin-labeling
descriptions lose part of their meaning because of the sub-
ꢀ
stantial covalency of Ir C bonds and the presence of
a heavy metal, which causes a strong spin-orbit coupling.[27c]
The absorption bands displayed by 5c are slightly red-
shifted compared with those of 5a. The other two com-
pounds, 5b and 5d, showed absorption spectra that were
almost coincident with those of the corresponding com-
pounds containing the Fphox ancillary ligand. Indeed, the
ancillary ligand does not strongly influence the lowest elec-
tronic transition. The emission spectrum of 5a in CH3CN at
298 K shows a broad band centered at 497 nm, which is
blueshifted upon decreasing solvent polarity (see spectra in
CH2Cl2/CH3Cl in Figure 3a). In the case of 5c, an emission
spectrum with a maximum at 520 nm is observed and is
practically unchanged if the polarity changes (Figure 3b).
The excited-state lifetime is close to 2 ms for all investigated
complexes in deaerated CH3CN at 298 K, which proves that
the corresponding transition is spin forbidden. The emission
quantum yield is very high (Fem =0.80) for 5a and lower for
complexes containing the ppy ligand. The emission is strong-
ly quenched (ca. 70 times) by dioxygen, with a rate constant
close to the diffusion limit (kq ꢁ2ꢃ1010 mꢀ1 sꢀ1) in agreement
with previously reported examples.[28] Moreover, complexes
5b and 5d showed photophysical properties (emission spec-
tra, excited state lifetime, and emission quantum yields) sim-
ilar to those of the analogous complexes that contain the
Fphox ligand.
In comparison with other heteroleptic complexes that
contain two ppy or F2ppy ligands and a third ancillary
ligand,[29] complexes 5a and 5c show one of the “bluest”
and brightest luminescence. For example, the known [Ir-
Figure 4. CD spectra of a) DR-5a (c) and LS-5b (b) and b) the cor-
responding LR-5a (c) and DS-5b (b) isomers in air-equilibrated
CH3CN at 298 K.
ACHTUNGTRENNUNG(F2ppy)2ACHTUNGTRENNUNG(acac)] shows a very similar emission band maxi-
mum in solution in CH3CN and in a CH2Cl2/CH3Cl (1:1 v/v)
rigid matrix, but a lower emission quantum yield (ca. 50%,
see Table 1).
show different CD spectra, as do the two isomers of com-
plex 5b (Figure 4a and b, b). The most striking feature is
that the spectra of the DR isomer of 5a and the LS isomer of
5b are mirrored (Figure 4a) across the entire investigated
spectral region, as are the corresponding LR and DS isomers
(Figure 4b). This result demonstrates that the stereogenic
center on the ancillary ligand greatly influences the overall
CD response, although the investigated electronic transi-
tions are not predominantly centered on the ancillary
ligand. As evident from the crystal structures, the phenyl
ring can give rise to a more favorable p–p interaction with
the F2ppy ligand in one of the two isomers, so that it influen-
ces the helicity of the complex. The two isomers with
mirror-like behavior are neither enantiomers nor diaster-
oisomers because they differ at the F substituent on the an-
cillary ligand. A closer look at the CD spectra of Figure 4
shows that the band with a maximum of about 285 nm is the
only one that is identical in position and shape, but not in
sign, for the four isomers. For example, the spectrum for
(DR)-5a in Figure 4a is superimposed on the spectrum of
(DS)-5b in Figure 4b so that it can be assigned to the F2ppy
ligands, and the sign depends on the helicity of the complex.
Analogous investigations were carried out on the diaste-
reomerically pure Ir complexes after chromatographic sepa-
ration. The absorption and emission properties are very sim-
ilar for the two diastereoisomers of each complex (5a–d)
upon excitation with unpolarized light. For example, LR-
and DR-5a complexes exhibit small changes in the absorp-
tion band (Figure S7a in the Supporting Information),
a small shift in the emission band maximum (Figure S7b in
the Supporting Information), and slight differences in the
emission quantum yields and lifetime of the emitting excited
state (Table S2 in the Supporting Information), both in air-
equilibrated CH3CN and CH2Cl2. This result is not surpris-
ing; the two diastereoisomers differ only in the helicity on
the metal center.
On the other hand, upon excitation with circularly polar-
ized light, each diastereoisomer exhibits a peculiar and dis-
tinguishable CD absorption spectrum. Figure 4 shows the
CD spectra of the four isomers of 5a and 5b. The two iso-
mers of compound 5a, DR and LR, (Figure 4a and b, c)
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P. Ceroni, M. Monari, M. Bandini et al.
However, in the investigated spectral region no electronic
transition can be assigned as centered only on the ancillary
ligand because it would have appeared the same in the CD
spectra of LR- and DR-5a or LS- and DS-5b. Similar results
have been obtained for the other four isomers of 5c and 5d
(Figure S8 in the Supporting Information). The CD spec-
trum enables us to clearly distinguish the electronic transi-
tions centered on the F2ppy ligand or involving the ancillary
ligand.
substituent on the ancillary ligand, which makes the IrIII oxi-
dation more difficult. On the other hand, the phenyl pyrid-
yl-based reduction is practically unaffected, as expected.
The same trend is registered for the two complexes that
contain two F2ppy ligands, although the reported oxidation
process is not chemically reversible at scan rates up to
5 Vsꢀ1. Compared with the ppy-based complexes, the F2ppy-
based complexes present oxidation and reduction processes
that are substantially positively shifted, as expected due to
the presence of the fluorine substituents on the cyclometa-
lating ligands. The reduction located on one of the F2ppy li-
Electrochemical properties: The complexes have been inves-
tigated as diastereoisomeric mixtures in CH3CN that con-
tained tetraethylammonium hexafluorophosphate (TEAPF6)
as the supporting electrolyte at 298 K. In the investigated
potential region, all the complexes showed a one-electron
oxidation and a one-electron reduction process (Table 2).
gands occurs at the same potential as the model [Ir
ACHTUNGTRENNUNG(F2ppy)2-
AHCTUNGTRENNUNG
made for the oxidation process because of the chemical irre-
versibility associated with the 5a and 5b complexes investi-
gated herein.
Thanks to the chemical and electrochemical reversibility
of the first oxidation and reduction process observed for 5d,
we have recorded the electrochemiluminescence (ECL)
spectrum in CH3CN/TEAPF6 (Figure S9 in the Supporting
Information). This result is important in view of the applica-
tions of these complexes in ECL sensors or LEDs.
Table 2. Half-wave potentials (E1/2 [V] vs. SCE), unless otherwise noted,
of the investigated [IrIII] complexes compared with [Ir
ACTHNUTRGENNUG(F2ppy)HCATUNGTERUNGN(N acac)] in
CH3CN/TEAPF6 solution at 298 K. Working electrode: glassy carbon.
E1/2 [V]
5a
5b
5c
5d
+1.04[a]
+0.96[a]
+0.76
+0.73
+1.13
ꢀ2.08
ꢀ2.09
ꢀ2.21
ꢀ2.20
ꢀ2.06
Conclusion
[Ir
N
(acac)]
[a] Anodic peak, Epa at a scan rate of 1 Vsꢀ1
.
Novel cyclometalated [IrIII] complexes that contain two ppy
or F2ppy ligands and an ancillary ligand consisting of
a phenol-oxazoline (phox and Fphox), have been prepared
and characterized from a structural, photophysical, and elec-
trochemical viewpoint.
Complexes 5a and 5b show blue luminescence with
a very high quantum yield in deaerated CH3CN. A metal-
centered oxidation process and a reduction process located
on the ppy ligand have been reported for all the investigated
complexes. The reported photophysical and electrochemical
data suggest that, as expected, the presence of a fluorine
substituent on the phenol ring of the ancillary ligand does
not influence the properties of the resulting complexes.
Therefore, this position can be exploited to insert other
functional groups, that is, a metal-coordinating unit, such as
terpyridine, to construct a supramolecular device.
Figure 5 shows the cyclic voltammogram of 5d, which in-
dicates that both the reduction and the oxidation processes
are chemically and electrochemically reversible under the
investigated experimental conditions. The observed oxida-
tion and reduction processes can be assigned to the metal
center and the phenyl pyridyl ligand, respectively, on the
basis of close proximity to those reported for [IrACTHNUTRGNEUNG
(ppy)3].[27c]
The modest positive shift of the oxidation process on going
from 5d to 5c can be related to the electron-withdrawing
Most importantly, the presence of an enantiomerically
pure chiral ancillary ligand enables the facile separation of
L and D isomers by conventional flash chromatography,
which gives the corresponding LR and DR or LS and DS
diastereoACTHNUTRGENUGiN somers in excellent yield and high stereochemical
purity. The two diastereoisomers of each IrIII complex exhib-
it very similar photophysical properties upon excitation with
unpolarized light, whereas they are clearly distinguishable
by CD spectroscopy according to their helicity. This result is
very promising in view of using these complexes as lumines-
cent sensors of chiral molecules after proper functionaliza-
tion of the ancillary ligand.
Figure 5. Cyclic voltammogram of a 1 mm solution of 5d in CH3CN/
TEAPF6 at 298 K. Scan rate: 1 Vsꢀ1 for the anodic scan and 5 Vsꢀ1 for
the cathodic scan. Working electrode: glassy carbon.
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Highly Luminescent [IrIII]-Cyclometalated Complexes
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low pressure distillation. The crude was purified by flash chromatography
to give diastereomerically pure DR(S)-5 and LR(S)-5 in nearly 1:1 ratio.
Experimental Section
1
Data for (DR +LR)-5a: Yellow solid. Yield=70% (d.r.=59:41). Flash
chromatography (cHex/EtOAc=90:10).
General: H NMR spectra were recorded by using Varian 200 (200 MHz)
and Varian 400 (400 MHz) spectrometers. Chemical shifts are reported in
ppm referenced to TMS, with the solvent resonance as the internal stan-
dard (CDCl3, d=7.27 ppm). Data are reported as follows: chemical shift,
multiplicity (s=singlet, d=doublet, pd=pseudo-doublet, t=triplet, pt=
pseudo-triplet, q=quartet, pq=pseudo-quartet, m=multiplet, coupling
constants (Hz). 13C NMR spectra were recorded by using Varian 200
(50 MHz) and Varian 400 (100 MHz) spectrometers with complete
proton decoupling. Chemical shifts are reported in ppm referenced to
TMS with the solvent as the internal standard (CDCl3, d=77.0 ppm).
19F NMR spectra were recorded by using a Varian 400 (376.99 MHz)
spectrometer with BF3·Et2O in CDCl3 as the external standard (d=
ꢀ131.3 ppm). GC-MS spectra were recorded by EI ionization at 70 eV by
using a Hewlett–Packard 5971 with GC injection. Spectra are reported as
m/z (rel. intensity). LC-ESI mass spectra were obtained by using an Agi-
lent Technologies MSD1100 single-quadrupole mass spectrometer. Chro-
matographic purification was performed by using 240–400 mesh silica gel.
Elemental analyses were carried out by using an EACE 1110 CHNOS
analyzer. Optical rotations were determined in a 1 mL cell with a path
length of 10 mm (Na D line). Melting points were determined by using
a Bibby Stuart Scientific Melting Point Apparatus SMP 3 and are not cor-
rected (decomp.: decomposition). All anhydrous solvents were supplied
by Fluka in Sureseal bottles and used as received. 2-Ethoxyethanol was
distilled from MgSO4. IrCl3·3H2O was supplied by Strem. ppy and F2ppy
ligands were procured from commercial sources and used without further
purification.
(DR)-5a (first eluted isomer): M.p. decomp; [a]D =ꢀ408 (c=1.0, CHCl3);
1H NMR (400 MHz, CDCl3): d=4.19 (dd, J=4.2, 8.8 Hz, 1H), 4.72 (t,
J=8.8 Hz, 1H), 4.90 (dd, J=4.2, 8.8 Hz, 1H), 5.25 (dd, J=2.4, 9.2 Hz,
1H), 5.80 (dd, J=2.4, 9.2 Hz, 1H), 6.12 (dd, J=8.0, 13.2 Hz, 1H), 6.28–
6.35 (m, 4H), 6.46 (d, J=8.4 Hz, 1H), 6.82 (t, J=7.2 Hz, 2H), 6.98 (t, J=
7.2 Hz, 1H), 7.05–7.15 (m, 2H), 7.17 (t, J=7.2 Hz, 1H), 7.45 (t, J=
9.2 Hz, 1H), 7.54 (d, J=8.4 Hz, 1H), 7.75 (t, J=8.0 Hz, 1H), 8.25 (d, J=
8.4 Hz, 1H), 8.50 (d, J=5.6 Hz, 1H), 8.81 ppm (d, J=6.0 Hz, 1H);
13C NMR (100 MHz, CDCl3): d=69.7, 75.6, 96.6 (pt, 2J
1C), 97.6 (pt, 2J(C,F)=26.3 Hz, 1C), 100.3 (d, 2J
(C,F)=24.0 Hz, 2C),
113.3 (d, 2J(C,F)=17.0 Hz, 1C), 114.0 (d, 2J
(C,F)=17.0 Hz, 1C), 120.9,
121.4, 121.8, 122.6 (d, 2J(C,F)=20.1 Hz, 1C), 123.1 (d, 2J
(C,F)=20.1 Hz,
1C), 125.3 (2C), 127.5 (2C), 128.1 (4C), 133.1, 133.3, 137.1, 137.7, 139.9,
147.6, 147.8, 152.1, 152.2, 161.5, 162.6 (d, 1J
(C,F)=180.0 Hz, 1C), 165.1
(d, 1J(C,F)=194.7 Hz, 4C), 171.7 ppm; 19F NMR (376.99 MHz): d=
ACHTUNGTREN(NUNG C,F)=26.3 Hz,
A
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
ꢀ88.99 (t, J=12.4 Hz, 1F), ꢀ88.75 (t, J=10.9 Hz, 1F), ꢀ87.15 (q, J=
9.8 Hz, 1F), ꢀ86.5 (q, J=9.4 Hz, 1F), ꢀ83.22 ppm (dd, J=6.8, 12.4 Hz,
1F); ESI-MS: m/z: 830 [M+1], 1683 [2M+Na]; elemental analysis calcd
(%) for C37H23F5IrN3O2 (829.13): C 53.62, H 2.80, N 5.07; found: C 53.58,
H 2.82, N 5.02.
(LR)-5a (second eluted isomer): M.p. decomp; [a]D =ꢀ180 (c=1.0,
CHCl3); 1H NMR (400 MHz, CDCl3): d=4.04 (dd, J=5.4, 9.2 Hz, 1H),
4.35 (t, J=9.2 Hz, 1H), 4.43 (dd, J=5.4, 9.2 Hz, 1H), 5.07 (dd, J=2.4,
9.0 Hz, 1H), 5.49 (dd, J=2.4, 9.0 Hz, 1H), 6.17 (dd, J=7.4, 11.2 Hz, 1H),
6.24 (d, J=8.0 Hz, 2H), 6.26–6.34 (m, 1H), 6.70 (d, J=8.0 Hz, 2H), 6.85
(t, J=7.4 Hz, 1H), 6.96 (q, J=8.0 Hz, 1H), 6.99–7.17 (m, 3H), 7.30 (t,
J=5.8 Hz, 1H), 7.60 (t, J=8.0 Hz, 1H), 7.91 (t, J=8.0 Hz, 1H), 8.10 (d,
J=8.8 Hz, 1H), 8.37 (d, J=8.8 Hz, 1H), 8.43 (d, J=4.8 Hz, 1H),
9.10 ppm (d, J=6.0 Hz, 1H); 13C NMR (100 MHz, CDCl3): d=68.4, 75.9,
Typical procedure for the synthesis of phox ligands (3a,b): Dry toluene
(8 mL), dried ZnCl2 (2.5 mol%), phenol (3.1 mmol, 1 equiv), and (S or
R)-2 (1.2 equiv) were placed in a flamed two-necked flask equipped with
a condenser. The mixture was heated at reflux overnight, then the vola-
tile components were removed under reduced pressure and EtOAc
(10 mL) was added. After stirring for 10 min, the insoluble materials
were removed by filtration and the filtrate concentrated under reduced
pressure. phox ligands 3 were obtained by purification by using flash
chromatography (eluent: cHex/AcOEt/TEA 90:10:1!70:30:1).
96.5 (pt, 2J
2J(C,F)=22.4 Hz, 2C), 113.9 (d, 2J
(C,F)=19.3 Hz, 1C), 119.6, 120.4, 120.9, 121.8, 122.2 (d, 2J
1C), 122.4 (d, 2J
(C,F)=8.9 Hz, 1C), 126.5 (2C), 128.1, 128.4 (3C), 133.0,
133.1, 134.1, 137.4, 138.1, 140.1, 148.8, 149.9, 153.1, 155.0, 159.4, 162.6 (d,
1J(C,F)=185.1 Hz, 1C), 165.1 (d, 1J
(C,F)=197.5 Hz, 4C), 172.3 ppm;
A
ACHTUNGTNER(NUNG C,F)=27.8 Hz, 1C), 100.4 (d,
A
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
A
ACHTUNGTRENNUNG
Data for (S)-3a: White wax (yield=68%). [a]D = +34 (c=0.85,
19F NMR (376.99 MHz): d=ꢀ89.42 (t, J=12.1 Hz, 1F), ꢀ89.35 (t, J=
9.4 Hz, 1F), ꢀ87.47 (q, J=9.4 Hz, 1F), ꢀ86.54 (q, J=9.4 Hz, 1F),
ꢀ86.30 ppm (dd, J=8.3, 12.4 Hz, 1F); ESI-MS: m/z: 830 [M+1], 1683
[2M+Na]; elemental analysis calcd for C37H23F5IrN3O2 (829.13): C 53.62,
H 2.80, N 5.07; found: C 53.60, H 2.77, N 5.05.
1
CH2Cl2); H NMR (200 MHz, CDCl3): d=4.27 (t, J=8.0 Hz, 1H), 4.83 (t,
J=9.2 Hz, 1H), 5.50 (t, J=9.6 Hz, 1H), 9.93 (t, J=7.4 Hz, 1H), 7.06 (d,
J=8.4 Hz, 1H), 7.28–7.43 (m, 6H), 7.74 (d, J=7.2 Hz), 12.2 ppm (s, 1H);
13C NMR (50 MHz, CDCl3): d=68.9, 74.2, 110.6, 117.0, 118.9, 126.6 (2C),
128.0, 128.4, 129.0 (2C), 133.8, 141.7, 160.2, 166.5 ppm; ESI-MS: m/z: 240
[M+1]; elemental analysis calcd (%) for C15H13NO2 (239.09): C 75.30, H
5.48, N 5.85; found: C 75.23, H 5.40, N 5.88.
Data for (DS +LS)-5b: Yellow solid. Yield=61% (d.r.=51:49). Flash
chromatography (cHex/EtOAc=85:15).
(LS)-5b (first eluted isomer): M.p. decomp; [a]D = +465 (c=1.1, CHCl3);
1H NMR (400 MHz, CDCl3): d=4.16 (dd, J=3.6, 9.2 Hz, 1H), 4.67 (t,
J=9.2 Hz, 1H), 4.97 (dd, J=3.6, 9.2 Hz, 1H), 5.32 (d, J=6.4 Hz, 1H),
5.81 (d, J=9.2 Hz, 1H), 6.25 (d, J=6.8 Hz, 1H), 6.29–6.34 (m, 3H), 6.44
(t, J=7.2 Hz, 1H), 6.73 (d, J=8.0 Hz, 1H), 6.80 (t, J=7.6 Hz, 2H), 6.98
(t, J=7.2 Hz, 1H), 7.07 (t, J=7.2 Hz, 1H), 7.12 (t, J=7.6 Hz, 1H), 7.21
(t, J=6.8 Hz, 1H), 7.44 (t, J=8.8 Hz, 1H), 7.52 (d, J=8.4 Hz, 1H), 7.73
(t, J=7.6 Hz, 1H), 7.79 (d, J=8.0 Hz, 1H), 8.25 (d, J=8.4 Hz, 1H), 8.47
(d, J=6.0 Hz, 1H), 8.84 ppm (d, J=5.6 Hz, 1H); 13C NMR (100 MHz,
Data for (R)-3b: White solid (yield=40%). M.p. 57–608C; [a]D =ꢀ20.7
(c=0.6, CH2Cl2); 1H NMR (200 MHz, CDCl3): d=4.34 (t, J=8.4 Hz,
1H), 4.89 (dd, J=1.4, 10.2 Hz, 1H), 5.45 (dd, J=1.4, 8.4 Hz, 1H), 6.63
(dd, J=1.0, 8.0 Hz, 1H), 6.90 (dd, J=1.2, 8.4 Hz, 1H), 7.29–7.47 ppm (m,
6H); 13C NMR (50 MHz, CDCl3): d=67.2, 74.4, 100.1 (d, J=12.9 Hz,
1C), 106.0 (d, J=22.0 Hz, 1C), 112.8 (d, J=3.1 Hz, 1C), 126.4 (2C),
127.9, 128.8 (2C), 133.4 (d, J=11.8 Hz, 1C), 114.1, 161.1 (d, J=256.0 Hz,
1C), 161.8 (d, J=4.6 Hz, 1C), 165.3 ppm (d, J=2.5 Hz, 1C); ESI-MS: m/
z: 258 [M+1]; elemental analysis calcd for C15H12FNO2 (257.09): C
70.03, H 4.70, N 5.44; found: C 69.97, H 4.72, N 5.41.
(III) complexes 4:[24]
Synthesis of the dimeric cyclometalated iridiumACTHNUTRGNEUNG
IrCl3·3H2O (100 mg, 0.28 mmol) and the desired cyclometalating ligand
(ppy or F2ppy; 0.70 mmol, 2.5 equiv) were added to degassed ethoxyetha-
nol/water (3:1, 4 mL). The mixture was heated at reflux overnight
CDCl3): d=70.8, 75.1, 96.5 (pt, 2J
27.1 Hz, 1C), 109.2, 113.2, 113.4 (d, 2J
(C,F)=13.1 Hz, 1C), 121.3, 121.8, 122.5 (d, 2J
(d, 2J
(C,F)=20.1 Hz, 1C), 125.1, 125.2 (4C), 127.4, 128.0 (4C), 133.9,
137.0, 137.5, 140.1, 147.6, 147.7, 152.5, 152.6, 157.3, 157.4, 162.8, 165.2 (d,
1J
A
ACHTUNGTRENNUNG(C,F)=
AHCTUNGTRENNUNG
A
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
A
(t, J=12.4 Hz, 1F), ꢀ89.74 (t, J=10.9 Hz, 1F), ꢀ87.30 (q, J=9.8 Hz,
1H), ꢀ86.42 ppm (q, J=9.4 Hz, 1F); ESI-MS: m/z: 812 [M+1], 1645
[2M+Na]; elemental analysis calcd (%) for C37H24F4IrN3O2 (811.14): C
54.81, H 2.98, N 5.18; found: C 54.77, H 2.94, N 5.21.
yellow solid was collected by filtration.
Synthesis of the phox cyclometalated iridiumACTHNUTRGENUG(N III) complexes 5: The de-
sired dimeric cyclometalated iridiumACTHNUGTRNEUNG(III) complex (4a or 4b; 0.08 mmol)
was added to a mixture of phox ((S)-3a or (R)-3b; 0.22 mmol) and
Na2CO3 (0.8 mmol) in ethoxyethanol (3 mL). The mixture was heated at
reflux overnight (ꢁ16 h), then cooled to RT and the solvent removed by
(DS)-5b (second eluted isomer): M.p. decomp; [a]D = +159 (c=1.0,
CHCl3); 1H NMR (400 MHz, CDCl3): d=4.21 (dd, J=3.6, 9.2 Hz, 1H),
4.26 (t, J=9.2 Hz, 1H), 4.36 (dd, J=3.6, 9.2 Hz, 1H), 5.11 (d, J=6.6 Hz,
Chem. Eur. J. 2012, 00, 0 – 0
ꢁ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
&
7
&
ÞÞ
These are not the final page numbers!

P. Ceroni, M. Monari, M. Bandini et al.
1H), 5.52 (d, J=6.6 Hz, 1H), 6.28–6.35 (m, 2H), 6.45 (t, J=7.2 Hz, 1H),
6.61 (d, J=8.4 Hz, 1H), 6.71–6.75 (m, 3H), 7.13–7.24 (m, 5H), 7.59 (t,
J=8.4 Hz, 1H), 7.72 (d, J=9.6 Hz, 1H), 7.85 (t, J=8.4 Hz, 1H), 8.12 (d,
J=8.4 Hz, 1H), 8.27 (d, J=6.0 Hz, 1H), 8.33 (d, J=8.4 Hz, 1H),
8.89 ppm (d, J=6.0 Hz, 1H); 13C NMR (100 MHz, CDCl3): d=69.7, 75.0,
1H), 6.16 (d, J=7.6 Hz, 1H), 6.41 (t, J=6.8 Hz, 1H), 6.47 (t, J=6.8 Hz,
1H), 6.55 (t, J=6.0 Hz, 1H), 6.64–6.71 (m, 4H), 6.79 (t, J=6.8 Hz, 1H),
6.85 (t, J=6.8 Hz, 1H), 7.12–7.20 (m, 5H), 7.50 (t, J=7.0 Hz, 2H), 7.64
(d, J=8.0 Hz, 1H), 7.70 (d, J=8.4 Hz, 1H), 7.73–7.78 (m, 2H), 7.91 (d,
J=8.0 Hz, 1H), 8.06 (d, J=6.0 Hz, 1H), 8.86 ppm (d, J=5.6 Hz, 1H);
13C NMR (100 MHz, CDCl3): d=69.2, 74.8, 110.4, 112.5, 117.8, 118.1,
120.2, 120.7, 120.9, 121.8, 123.6, 123.9, 125.2, 126.5, 127.6, 128.0, 128.3,
128.8, 129.0, 129.2, 129.4, 132.1, 133.2, 135.0, 136.1, 136.7, 141.2, 143.9,
144.7, 149.3, 149.9, 150.5, 151.9, 162.5, 168.3, 168.4, 169.5 ppm; ESI-MS:
m/z: 740 [M+1], 1501 [2M+Na]; elemental analysis calcd (%) for
C37H28IrN3O2 (739.18): C 60.15, H 3.82, N 5.69; found: C 60.12, H 3.80, N
5.64.
96.5 (pt, 2J
113.2, 113.9 (d, 2J
120.8, 122.2 (pt, 2J
(4C), 129.4, 133.7, 137.2, 137.8, 140.6, 149.2, 150.3, 154.1, 155.6, 161.4,
163.0, 165.1 (d, 1J(C,F)=150.1 Hz, 4C), 169.5 ppm; 19F NMR
A
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
(376.99 MHz): d=ꢀ89.40, ꢀ89.29 (m, 2F), ꢀ87.43 (q, J=9.4 Hz, 1F),
ꢀ86.84 ppm (q, J=9.4 Hz, 1F); ESI-MS: m/z: 812 [M+1]; elemental
analysis calcd (%) for C37H24F4IrN3O2 (811.14): C 54.81, H 2.98, N 5.18;
found: C 54.78, H 2.99, N 5.15.
X-ray crystallography: The diffraction experiments for 5a, 5b, and 5d
were carried out at RT by using a Bruker SMART Apex II CCD-based
diffractometer with graphite-monochromated MoKa radiation (l=
0.71073 ꢂ). Intensity data were measured over the full diffraction sphere
by using w scans with a width of 0.38. The software SMART[30] was used
for collecting frames of data, indexing reflections, and determining the
lattice parameters. The collected frames were then processed for integra-
tion by using the software SAINT,[30] and an empirical absorption correc-
tion was applied by using SADABS.[31] The structures were solved by
direct methods (SIR97)[32] and subsequent Fourier syntheses, and were
refined by full-matrix least-squares calculations on F2 (SHELXTL),[33]
which attributed anisotropic thermal parameters to all non-hydrogen
atoms. The hydrogen atoms that were located in the Fourier difference
map were placed in calculated positions and refined with idealized geom-
etry by using Uiso(H)=1.2Ueq(C). Both 5a and 5b show two independent
molecules in the asymmetric unit. Complex 5a crystallizes with two
CH2Cl2 solvent molecules in the asymmetric unit, whereas in 5b the dis-
ordered lattice solvent molecules (CH2Cl2) could not be modeled reason-
ably, so the SQUEEZE routine in PLATON[34] was used to generate re-
flection data that do not include a contribution from the diffuse solvent.
The structure of 5b also showed some degree of twinning. Crystal data
and experimental details are reported in Table S1 in the Supporting In-
formation. CCDC-845832, CCDC-845833, and CCDC-845834 contain the
supplementary crystallographic data for this paper. These data can be ob-
tained free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif.
Data for (DR +LR)-5c: Yellow solid. Yield=78% (d.r.=51:49). Flash
chromatography (cHex/EtOAc=80:20).
(DR)-5c (first eluted isomer): M.p. decomp; [a]D =ꢀ313 (c=1.0, CHCl3);
1H NMR (400 MHz, CDCl3): d=4.13 (dd, J=3.6, 9.2 Hz, 1H), 4.66 (t,
J=9.2 Hz, 1H), 4.86 (dd, J=3.6, 9.2 Hz, 1H), 5.91 (d, J=6.8 Hz, 1H),
6.10 (dd, J=8.0, 11.6 Hz, 1H), 6.24 (d, J=6.8 Hz, 2H), 6.38 (d, J=
7.6 Hz, 1H), 6.44 (d, J=8.4 Hz, 1H), 6.65–6.81 (m, 6H), 6.92 (t, J=
7.2 Hz, 1H), 6.99–7.14 (m, 4H), 7.34–7.39 (m, 2H), 7.50 (d, J=7.6 Hz,
1H), 7.68 (t, J=7.6 Hz, 1H), 7.82 (d, J=8.0 Hz, 1H), 8.56 (d, J=6.0 Hz,
1H), 8.86 ppm (d, J=6.0 Hz, 1H); 13C NMR (100 MHz, CDCl3): d=75.4,
77.4, 99.7 (pt, 2J
ACHTUNGTRENNUNG(C,F)=14.7 Hz, 2C), 118.1, 118.9, 120.1, 121.0, 121.1,
121.5, 123.7, 124.2, 125.6, 126.5, 127.0, 127.8, 128.0, 128.9, 129.0, 129.2,
131.3, 132.1, 132.6, 132.8, 136.1, 136.6, 140.2, 144.3, 145.4, 147.7, 147.9,
153.3, 161.7, 162.9 (d, 1J
ACTHNUGRTENUNG(C,F)=255.7 Hz, 1C), 164.1, 167.9, 169.3 ppm;
19F NMR (376.99 MHz): d=ꢀ83.61 ppm (dd, J=6.8, 13.6 Hz, 1F); ESI-
MS: m/z: 758 [M+1], 1537 [2M+Na]; elemental analysis calcd (%) for
C37H27FIrN3O2 (757.17): C 58.72, H 3.60, N 5.55; found: C 58.70, H 3.57,
N 5.53.
(LR)-5c (second eluted isomer): M.p. decomp; [a]D =ꢀ328 (c=1.0,
CHCl3); 1H NMR (400 MHz, CDCl3): d=4.06 (dd, J=3.6, 9.2 Hz, 1H),
4.21 (t, J=9.2 Hz, 1H), 4.42 (dd, J=3.6, 9.2 Hz, 1H), 5.71 (d, J=7.6 Hz,
1H), 6.10 (d, J=7.2 Hz, 1H), 6.12 (d, J=7.2 Hz, 1H), 6.28 (pq, J=
8.8 Hz, 2H), 6.61 (d, J=8.0 Hz, 2H), 6.70 (pqt, J=7.6 Hz, 2H), 6.79 (t,
J=8.0 Hz, 2H), 6.94 (q, J=7.6 Hz, 1H), 7.06–7.12 (m, 3H), 7.23 (t, J=
7.6 Hz, 1H), 7.47 (d, J=7.6 Hz, 1H), 7.52 (t, J=7.6 Hz, 1H), 7.64 (d, J=
8.0 Hz, 1H), 7.69 (d, J=8.0 Hz, 1H), 7.83 (t, J=8.0 Hz, 1H), 7.97 (d, J=
8.4 Hz, 1H), 8.29 (d, J=6.0 Hz, 1H), 9.07 ppm (d, J=5.6 Hz, 1H);
Photophysics: The experiments were carried out in CH3CN at RT. UV/
Vis absorption spectra were recorded by using a Perkin–Elmer l650 spec-
trophotometer. Fluorescence spectra were obtained for air-equilibrated
solutions by using a Varian Cary Eclipse spectrofluorimeter equipped
with a Hamamatsu R928 phototube. Fluorescence quantum yields were
measured by following the method of Demas and Crosby[35] (standard
13C NMR (100 MHz, CDCl3): d=69.8, 75.7, 99.6 (d, 2J
1C), 101.8 (d, 2J
(C,F)=70.0 Hz, 1C), 102.1, 117.9, 118.2, 119.9, 120.0,
ACHTUNGTREN(NUNG C,F)=22.4 Hz,
ACHTUNGTRENNUNG
120.1, 120.7, 121.1, 121.6, 123.5, 124.0, 126.8, 127.7, 128.3, 129.1, 129.3,
131.9, 132.3, 132.4, 134.4, 136.2, 136.9, 140.7, 143.4, 144.5, 148.8, 149.2,
150.0, 151.5, 161.5, 162.2 (d, 1J
ACTHUNTGRENNG(U C,F)=253.4 Hz, 1C), 168.3, 168.5 ppm;
19F NMR (376.99 MHz): d=ꢀ86.29 ppm (dd, J=6.8, 12.4 Hz, 1F); ESI-
MS: m/z: 758 [M+1], 1537 [2M+Na] elemental analysis calcd (%) for
C37H27FIrN3O2 (757.17): C 58.72, H 3.60, N 5.55; found: C 58.59, H 3.62,
N 5.47.
used: [IrACHTUNRGTENN(UG F2ppy)ACHTUNGTNERN(UNG acac)], acac=acetylacetonate, Fem =0.64 in deaerated
CH2Cl2).[28] Degassing was performed by four cycles of freeze-pump-
thaw, reaching a pressure of 1ꢃ10ꢀ5 mbar. Fluorescence lifetime meas-
urements were performed by using an Edinburgh FLS920 spectrofluore-
meter equipped with a TCC900 card for data acquisition in time-correlat-
ed single-photon counting experiments (0.5 ns time resolution) with a D2
lamp and a LDH-P-C-405 pulsed-diode laser. The estimated experimen-
tal errors are 2 nm on the band maximum, 5% on the molar absorption
coefficient and fluorescence lifetime, and 15% on the fluorescence quan-
tum yield.
Data for (DS +LS)-5d: Yellow solid. Yield=59% (d.r.=52:48). Flash
chromatography (cHex/EtOAc=70:30).
(LS)-5d (first eluted isomer): M.p. decomp; [a]D = +290 (c=1.0, CHCl3);
1H NMR (400 MHz, CDCl3): d=4.11 (dd, J=3.6, 8.8 Hz 1H), 4.61 (t, J=
8.8 Hz, 1H), 4.95 (dd, J=3.6, 8.8 Hz 1H), 5.98 (d, J=6.8 Hz, 1H), 6.17
(d, J=7.2 Hz, 2H), 6.36–6.41 (m, 2H), 6.66–6.81 (m, 7H), 6.91 (t, J=
7.6 Hz, 1H), 6.99–7.11 (m, 4H), 7.18 (t, J=7.2 Hz, 1H), 7.36 (t, J=
6.4 Hz, 1H), 7.51 (d, J=6.8 Hz, 1H), 7.66 (t, J=7.6 Hz, 1H), 7.78–7.83
(m, 2H), 8.52 (d, J=5.6 Hz, 1H), 8.88 ppm (d, J=4.8 Hz, 1H); 13C NMR
(100 MHz, CDCl3): d=70.7, 74.9, 109.5, 112.5, 118.0, 118.9, 119.9, 120.9,
121.1, 121.6, 123.7, 124.1, 125.4, 125.5, 126.9, 127.7 (3C), 128.9, 129.3,
129.9, 131.3, 132.1, 133.4, 135.9, 136.4, 140.5, 144.3, 145.5, 147.7, 148.1
(2C), 153.8, 162.5, 167.9, 169.4, 169.9 ppm; ESI-MS: m/z: 740 [M+1],
1501 [2M+Na]; elemental analysis calcd (%) for C37H28IrN3O2 (739.18):
C 60.15, H 3.82, N 5.69; found: C 60.09, H 3.84, N 5.61.
Electrochemistry: The electrochemical experiments were carried out in
argon-purged CH3CN solution at 298 K. For the cyclic voltammetry, the
working electrode was a glassy carbon electrode (0.08 cm2), the counter
electrode was a Pt spiral, and a silver wire was used as a quasi-reference
electrode (AgQRE). The potentials reported are referenced to SCE by
measuring the AgQRE potential with respect to ferrocene (E1/2 =0.395 V
vs. SCE for Fc+/Fc). The concentration of the compounds examined was
of the order of 1ꢃ10ꢀ3 m; 0.1m tetraethylammonium hexafluorophosphate
(TEAPF6) was added as the supporting electrolytes. Cyclic voltammo-
grams were obtained with scan rates in the range 0.05–5 Vsꢀ1. The esti-
mated experimental error on the E1/2 value is ꢂ10 mV.
(DS)-5d (second eluted isomer): M.p. decomp; [a]D = +212 (c=1.0,
CHCl3); 1H NMR (400 MHz, CDCl3): d=4.12 (t, J=9.2 Hz, 1H), 4.22
(dd, J=3.6, 9.2 Hz, 1H), 4.35 (dd, J=3.6, 9.2 Hz, 1H), 5.85 (d, J=7.6 Hz,
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Highly Luminescent [IrIII]-Cyclometalated Complexes
FULL PAPER
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Received: March 2, 2012
Published online: && &&, 0000
Chem. Eur. J. 2012, 00, 0 – 0
ꢁ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
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ÞÞ
These are not the final page numbers!

P. Ceroni, M. Monari, M. Bandini et al.
Phox and hounds: D and L isomers of
IrIII complexes based on 2-phenyl-pyr-
idyl (ppy) cyclometalating ligands and
chiral phenol-oxazoline ancillary
ligands (see figure) are readily avail-
able through simple separation on an
achiral stationary phase. Blue lumines-
cence, combined with an excellent
emission quantum yield (Fem =0.80), is
recorded for complexes with F2ppy
ligands.
Iridium Phosphor
E. Marchi, R. Sinisi, G. Bergamini,
M. Tragni, M. Monari,* M. Bandini,*
P. Ceroni* ..................... &&&& — &&&&
Easy Separation of D and L Isomers
of Highly Luminescent [IrIII]-Cyclome-
talated Complexes Based on Chiral
Phenol-Oxazoline Ancillary Ligands
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ÝÝ
These are not the final page numbers!