Molecular Tectonics: Design of Enantiopure Luminescent Heterometallic Ir(III)-Cd(II) Coordination Network

Article abstract of DOI:10.1021/acs.inorgchem.5b01910

With the aim of combining luminescence and chirality in heterometallic Ir(III)-Cd(II) coordination networks, synthetic strategies for the formation of new Ir(III)-based chiral metallatectons ([Ir(dFppy)₂(1)][PF₆]), both as a racemic mixture of Δ and Λ enantiomers (rac-[Ir(dFppy)₂(1)][PF₆]) and as enantiopure complexes (Δ-[Ir(dFppy)₂(1)][PF₆] and Λ-[Ir(dFppy)₂(1)][PF₆]), were developed. The final compounds were characterized both in solution and in the crystalline phase. Notably, their crystal structures were determined by single crystal X-ray diffraction, and their photophysical properties in solution and in the solid state were investigated. Combination of the cationic linear metallatecton with Cd²⁺ iodide salt ([CdI₃]^-), behaving as an anionic two-connecting node, leads to the formation of 1D chiral and neutral heterometallic Ir(III)-Cd(II) luminescent coordination networks both as a racemic mixture and as enantiomerically pure infinite architectures. The latter have been structurally studied in the solid state by X-ray diffraction both on single crystals and on microcrystalline powders. The infinite coordination networks display phosphorescence in the solid state at ca. 600 nm upon excitation at 400 nm.

Full text of DOI:10.1021/acs.inorgchem.5b01910

Article
pubs.acs.org/IC
Molecular Tectonics: Design of Enantiopure Luminescent
Heterometallic Ir(III)−Cd(II) Coordination Network
Chaojie Xu, Aurelie Guenet,* Nathalie Kyritsakas, Jean-Marc Planeix,* and Mir Wais Hosseini*
́
Molecular Tectonics Laboratory, UMR UDS-CNRS 7140, icFRC, University of Strasbourg, F-67000 Strasbourg, France
S
* Supporting Information
ABSTRACT: With the aim of combining luminescence and chirality in heterometallic
Ir(III)−Cd(II) coordination networks, synthetic strategies for the formation of new
Ir(III)-based chiral metallatectons ([Ir(dFppy)2(1)][PF6]), both as a racemic mixture
of Δ and Λ enantiomers (rac-[Ir(dFppy)2(1)][PF6]) and as enantiopure complexes
(Δ-[Ir(dFppy)2(1)][PF6] and Λ-[Ir(dFppy)2(1)][PF6]), were developed. The final
compounds were characterized both in solution and in the crystalline phase. Notably,
their crystal structures were determined by single crystal X-ray diffraction, and their
photophysical properties in solution and in the solid state were investigated.
Combination of the cationic linear metallatecton with Cd2+ iodide salt ([CdI3]−),
behaving as an anionic two-connecting node, leads to the formation of 1D chiral and
neutral heterometallic Ir(III)−Cd(II) luminescent coordination networks both as a racemic mixture and as enantiomerically pure
infinite architectures. The latter have been structurally studied in the solid state by X-ray diffraction both on single crystals and on
microcrystalline powders. The infinite coordination networks display phosphorescence in the solid state at ca. 600 nm upon
excitation at 400 nm.
may be achieved, (ii) phosphorescent metal complexes (e.g., Ir,
Ru, Os, Pt) exhibit metal-to-ligand-charge transfer (MLCT)
excited states enabling harvest of triplet excitons. In particular,
iridium(III) complexes are well-known triplet emitters15
possessing interesting photophysical properties, such as high
photoluminescence quantum yields (PLQY), long-lived
emission, good photostability, and emission color tunability.16
The incorporation of cationic or neutral Ir(III) luminescent
complexes into MOF-type materials has been achieved either
by doping,17 encapsulation of the metal complex within the
pores,18 or using them as linkers.10 Besides their luminescent
properties, octahedral iridium complexes bearing at least two
bidentate ligands also exhibit intrinsic metal-centered chirality
of the (Λ, Δ) type. Thus, for a bis-cyclometalated Iridium
complex bearing one neutral ligand such as a 2,2′-bipyridyl
chelate, two stereoisomers may be formed. In order to generate
enantiopure coordination complexes, different strategies19,20
have been explored, even though their asymmetric synthesis
remains a synthetic challenge. A direct approach is the use of
chiral organic ligand to drive the formation of only one
diastereoisomer or to separate the pairs of diastereoisomers
formed.21 In this approach, the chirality of the ligand is
transferred to the metal center. For cationic metal complexes,
the use of chiral anions22 leading to the formation of pairs of
diastereoisomers that can be separated by chromatography or
by solubility differences has been reported.23 Another approach
is based on a two-step procedure starting with the binding of an
auxiliary enantiopure organic ligand such as oxazoline- or
INTRODUCTION
■
Over the past two decades, coordination polymers (CPs) or
coordination networks (CNs), also called metal−organic
frameworks (MOFs), have received growing interest due to
their synthetic versatility as well as their wide spectrum of
applications, ranging from gas storage to biomedical imaging or
drug delivery.1 These infinite periodic architectures in the
crystalline phase are formed, under self-assembly conditions,
upon combination of bridging coordinating tectons2 and metal
centers or complexes as connecting nodes. Among many types
of coordination networks, luminescent MOFs3 are of particular
interest for their applications in chemical sensing or explosive
detection, for example.4 Other appealing applications are
mimicry of photosynthesis5 and photocatalysis.6 Although
most of the luminescent MOFs described so far are based on
conjugated organic linkers and/or lanthanide ions inducing
mainly ligand-centered (LC) emission or sharp lanthanide
emission, some recent examples dealing with heterometallic
luminescent MOFs (or mixed metal−organic frameworks,
M’MOFs) based on combination of metallatectons with
metal centers have been reported.7 Metallatectons (or metal-
loligands),8 coordination complexes, bearing at their periphery
secondary coordinating groups, behave as bridging ligands in
the presence of metal centers or complexes, offering at least two
divergently oriented coordination sites. The luminescent
heterometallic M’MOFs described so far are based on either
Ru(II),9 Os(II),9b−d Ir(III),10 or Pt(II)11 metalloligands as well
as Zn(II) porphyrins,12 dipyrrins,13 and polypyridine com-
plexes.14 The use of transition metal complexes as metal-
latectons offers at least two advantages over purely organic
tectons: (i) light absorption over the entire visible spectrum
Received: August 19, 2015
© XXXX American Chemical Society
A
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Scheme 1. Synthetic Route for the Preparation of the Racemic Complex rac-[Ir(dFppy)2(1)][PF6] (top) and the Enantiopure Ir
a b
,
Complex Δ-[Ir(dFppy)2(1)][PF6] (bottom)
a
The same route was followed to obtain Λ-[Ir(dFppy)2(1)][PF6] except that D-serine was used instead of L-serine. rac corresponds to the racemic
b
mixture of both Δ and Λ enantiomers. Conditions: (i) (1) 5,5′-Dibromo-2,2′-bipyridine (2), CH2Cl2/CH3OH 1/1, 60 °C, (2) KPF6, H2O, 70 °C;
(ii) 4-ethynylpyridine, Pd(PPh3)4, CuI, toluene/CH3CN/iPr2NH 2/0.15/0.8, 70 °C. (iii) (1) L-serine, NaOMe, MeOH, 40 °C, 16 h; (2) 1 M HCl,
MeOH, RT, 10 min.
serine-derivatives to generate and subsequently separate the
two diastereoisomers. The second step is based on the
replacement of the labile chiral ligand by one achiral bidentate
or two achiral monodentate ligands.24 It should be noted that,
compared to other metal centers with octahedral coordination
geometry such as Ru(II) complexes, the decisive advantage of
chiral enantiopure Iridium complexes bearing polypyridyl
bidentate ligands is their configurational inertness, i.e. the
absence of racemization of the enantiopure metal complexes in
solution under usual conditions. Thus, they appear to be ideal
entities for the design of metallatectons, leading to the
formation of enantiopure heterometallic coordination net-
works. While a number of chiral homometallic CPs are
known,25 fewer examples of chiral heterometallic CPs have
been described. The reported architectures are based on the
incorporation of BINAP-, BINOL-, or chiral salen-based linkers
via direct synthesis or postsynthetic transformations and have
been designed mainly for asymmetric catalysis.25e To the best
of our knowledge, their luminescent properties have not been
studied. Furthermore, only two chiral-at-metal complexes have
been used for the formation of homochiral coordination
networks. MacDonnell and co-workers used two substituted
enantiopure ruthenium complexes to generate luminescent
homometallic coordination oligomers through the formation of
C−N covalent bonds.26 However, the oligomers composed of
up to 15 Ru units were only characterized in solution.
Following another approach, Cohen and co-workers used an
enantiopure Co(III) dipyrrin as metallatecton. However, they
failed to obtain homochiral heterometallic architectures.27 It is
also worth noting that all the reported examples of
heterometallic CPs incorporating Ir-based metallatectons have
been obtained as racemic mixtures. The generation of
crystalline homochiral phosphorescent heterometallic coordi-
nation networks remains thus a challenge, in particular when
using enantiopure chiral-at-metal metallatectons. In order to
address this issue, i.e. combining luminescence with metal-
centered chirality, we have designed enantiomerically pure
Ir(III)-based complexes bearing two peripheral coordinating
sites. Enantiopure solid-state porous materials based on an
extended chiral-at-metal architecture may be of interest for
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Figure 1. Portions of the crystal structure of the racemic mixture (rac-[Ir(dFppy)2(1)][PF6]) showing the disposition of the two enantiomers Δ and
Λ in the lattice (ORTEP47 view, 50% probability level) (a) and the alternate packing of enantiomers leading to π−π interactions (b and c). H atoms,
−
PF6 anions, and solvent molecules are omitted for clarity. The C atoms of the organic ligands 1 and dFppy are differentiated by color.
sensing chiral molecules, for separating mixtures of enan-
tiomers, or for chemical transformation in chiral space.
Furthermore, the luminescent nature, resulting from the use
of Ir(III) complexes, of extended architectures formed in the
presence of connecting metallic nodes may be explored for
optical sensing mentioned above. It may also be noted that the
strategy proposed here is more efficient, since the chirality is
centered on the metal and thus does not require tedious
synthesis of enantiopure ancillary ligands.
Herein, we report the synthesis and characterization, both in
solution and in the solid state, of the new luminescent
cyclometalated Ir(III) cationic metallatecton as a racemate (rac-
[Ir(dFppy)2(1)]+) as well as enantiopure species (Δ-[Ir-
(dFppy)2(1)]+ and Λ-[Ir(dFppy)2(1)]+) (Scheme 1) and
their combinations with Cd2+ cation as a connecting node,
leading to the formation of 1D chiral coordination networks.
bis-cyclometalated Ir(III) complexes bearing as a third ligand a
bipyridine unit is based on the reaction between the dichloro-
bridged dimer [Ir(dFppy)2(μ-Cl)2] and the bipyridine
moiety.30 Unfortunately, the fluorinated complex [Ir-
(dFppy)2(1)][PF6] could not be obtained following this
synthetic route. Indeed, this strategy afforded a mixture of
fluorinated Iridium complexes, as evidenced by 19F NMR
spectroscopy. The mixture could not be purified by standard
methods. The desired Ir complex rac-[Ir(dFppy)2(1)][PF6]
was successfully obtained using another strategy based on Pd-
catalyzed Sonogashira31 coupling reactions using Ir(III)
complexes as substrates. It should be noted that such an
approach has been previously developed for Pd-catalyzed
Suzuki coupling reactions in which cationic tris-bidentate28b,32
or bis-tridentate33 cyclometalated Iridium(III) complexes were
used as substrates. This route requires the synthesis of 5,5′-
dibromo-2,2′-bipyridine (2). The latter was prepared in 69%
yield by a Stille coupling reaction using 5-bromo-2-iodopyridine
(Scheme 1 top).34 Using a slightly modified reported
procedure,28c the dibromo Ir complex rac-[Ir(dFppy)2(2)]-
[PF6] was obtained in 60% yield as a 1/1 mixture of both
enantiomers upon reaction of the dichloro-bridged dimer rac-
RESULTS AND DISCUSSION
■
Design of Ir(III)-based luminescent metallatectons.
The design of the organometallic cationic metallatecton is
based on an Ir(III) cyclometalated complex using two 2-(2,4-
difluorophenyl)pyridine (dFppy) units and a third neutral and
achiral 2,2′-bipyridine-type chelate (bpy). The latter is
connected to two 4-ethynylpyridyl moieties at positions 5
and 5′, leading thus to [Ir(dFppy)2(1)]+ complex (Scheme 1).
The ethynyl spacer connecting the two peripheral pyridyl units
to the central bipyridyl moiety was chosen in order to allow
coplanarity between the peripheral and central units and to
further extend the conjugation. The other two bidentate dFppy
ligands completing the coordination sphere of the Ir center
were introduced in order to obtain a luminescent metallatecton.
The rationale behind the introduction of fluorine atoms on the
2-phenylpyridyl (ppy) scaffold was to induce a hypsochromic
shift of the emission28 when compared to its nonfluorinated
analogue [Ir(ppy)2(1)]+,29 thus ensuring emission in the visible
range. This metallatecton [Ir(dFppy)2(1)]+ was designed to
behave as a linear bridging unit.
35
[Ir(dFppy)2(μ-Cl)]2 with the dibromo 2,2′-bipyridine ligand
2 in a mixture of CH2Cl2 and CH3OH followed by
precipitation with an aqueous KPF6 solution (Scheme 1 top).
Finally, a Pd-catalyzed Sonogashira coupling reaction between
rac-[Ir(dFppy)2(2)][PF6] and 4-ethynylpyridine36 afforded the
desired complex rac-[Ir(dFppy)2(1)][PF6] as a mixture of
enantiomers in 46% yield. In addition to classical character-
izations (see Supporting Information), rac-[Ir(dFppy)2(1)]-
[PF6] was also structurally studied in the crystalline phase by X-
ray diffraction on a single crystal (see Supporting Information
for crystallographic data). Crystals of rac-[Ir(dFppy)2(1)][PF6]
were obtained by vapor diffusion of Et2O into a CH3CN
solution of the Ir complex (Figure 1). Owing to the disorder of
solvent molecules, the structure was solved using the
SQUEEZE command.37 rac-[Ir(dFppy)2(1)][PF6] crystallizes
in the triclinic system with P-1 as the space group, and it
exhibits similar geometrical parameters as those reported for
Synthesis and characterization of the Ir complex as a
racemate. The usual method for the formation of heteroleptic
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iridium(III) complexes containing two dFppy ligands and one
unsubstituted bpy38 or 5,5′-substituted bpy39 ligand (average
bond lengths and angles: Ir−Cppy 2.011 Å; Ir−Nppy 2.041 Å;
Ir−Nbpy 2.136 Å; Nppy−Ir−Nppy 171.71°; Nppy−Ir−Cppy 80.65°;
Nbpy−Ir−Nbpy 76.81°). Within the crystal, two crystallo-
graphically nonequivalent Ir complexes are present (Figures
1b and 1c). Both Ir centers adopt a slightly distorted octahedral
coordination geometry with the expected trans-arrangement of
the N donor atoms and cis-arrangement of the C atoms of the
cyclometalated ligand.15a,40 The bipyridyl moiety is almost
planar, and the ethynyl junctions between the central bipyridyl
and terminal pyridyl groups are almost linear (C−C−C angles
in the 174.37−180.00° range). The terminal pyridyl units are
almost coplanar to the central bpy unit (dihedral angles ranging
from −11.84° to 4.92°). Both Δ and Λ enantiomers are present
in the lattice (Figure 1a), leading thus to an achiral space group.
The length of the metallatecton, i.e. the distance between the
two N atoms of the terminal pyridyl units, is ca. 20.6 Å. π−π
interactions between two substituted bpy ligands belonging to
two neighboring Δ (or Λ) enantiomers are observed (shortest
C−C distances of 3.55 and 3.59 Å for the two types of Ir
complexes; Figures 1b and 1c respectively). The purity of the
microcrystalline phase obtained was investigated by powder x-
Ray diffraction (PXRD), which revealed a good match between
the recorded and simulated patterns using the single crystal
data (see Supporting Information).
Synthesis and characterization of the enantiopure
complexes. The strategy used for the synthesis of enantiopure
Δ-[Ir(dFppy)2(1)][PF6] and Λ-[Ir(dFppy)2(1)][PF6] com-
plexes was based on chiral resolution of the iridium dimer
rac-[Ir(dFppy)2(μ-Cl)]2 (Scheme 1 bottom). Using the
procedure reported for the nonfluorinated analogue [Ir-
(ppy)2(μ-Cl)],24a the resolution was achieved using L- or D-
serine as chiral auxiliaries. The treatment of the racemic mixture
with L-serine afforded the diastereoisomers Δ-[Ir(dFppy)2(L-
serine)] and Λ-[Ir(dFppy)2(L-serine)]. The same holds when
D-serine is used. For each couple ([Δ,L-serine], [Λ,L-serine] or
[Δ,D-serine], [Λ,D-serine]), the diastereoisomers were sepa-
rated by column chromatography on silica gel. The acid (HCl)
treatment of [Δ,L-serine] or [Λ,D-serine] afforded the
enantiopure ΔΔ- or ΛΛ-[Ir(dFppy)2(μ-Cl)]2 dimers, respec-
tively, in 40 and 37% overall yields. The latter are slightly lower
than those reported for the nonfluorinated analogue. This may
result from a more tedious chromatographic separation of the
intermediate serine-based diastereomeric complexes. Indeed,
for the [Δ,L-serine], [Λ,L-serine] couple, the first eluting
diastereoisomer [Δ,L-serine] could be obtained analytically
pure, whereas the slower eluting diastereoisomer corresponding
to [Λ,L-serine] was found to be always contaminated with [Δ,L-
serine]. Interestingly, when using D-serine, the first eluting band
which could be isolated as a pure compound was the [Λ,D-
serine] complex. As described above for the racemic mixture of
complexes, the bipyridine ligand 2 was then combined with the
enantiopure dimer (ΔΔ or ΛΛ) to obtain the enantiopure Δ-
or Λ-[Ir(dFppy)2(2)][PF6] complexes in 60% and 55% yield,
respectively. Again, a Sonogashira coupling reaction with 4-
ethynylpyridine afforded the enantiopure Δ- and Λ-[Ir-
(dFppy)2(1)][PF6] complexes in 46% and 45% yield,
respectively. It should be noted that the dibromo intermediate
as well as the final cationic Ir complexes could only be isolated
as their PF6 salts, as purification of their chloride salts was not
possible. All chiral complexes were characterized by standard
techniques (see Supporting Information), including circular
dichroism (CD, Figure 2). As expected, the enantiomers exhibit
mirror image CD spectra. Pairs of enantiomers also show
Figure 2. Circular dichroism spectra of ΔΔ-[Ir(dFppy)2(μ-Cl)]2
(black solid) and ΛΛ-[Ir(dFppy)2(μ-Cl)]2 (black, dashed) in
CH2Cl2 and of Δ-[Ir(dFppy)2(1)][PF6] (blue, solid) and Λ-
[Ir(dFppy)2(1)][PF6] (blue, dashed) in CH3CN at RT.
opposite specific rotation ([α]D, see Supporting Information).
It is important to note that the configuration of the metal
center (Δ or Λ) is retained during the coupling reaction.
Unfortunately, we were not able to grow suitable crystals of
the two enantiomers Δ-[Ir(dFppy)2(1)][PF6] and Λ-[Ir-
(dFppy)2(1)][PF6] for structural studies by X-ray diffraction
on a single crystal. However, the structure of the intermediate
dibromo complex Δ-[Ir(dFppy)2(2)]+ could be determined
(Figure 3). Single crystals were obtained upon slow diffusion of
Figure 3. Crystal structure of the enantiopure complex Δ-[Ir-
(dFppy)2(2)][PF6] (ORTEP47 view, 50% probability level). H
−
atoms and PF6 anions are omitted for clarity.
Et2O into a CH3CN solution containing the complex Δ-
[Ir(dFppy)2(2)][PF6]. Again, owing to the disorder of solvent
molecules, the structure was solved using the SQUEEZE
command.37 As expected, Δ-[Ir(dFppy)2(2)][PF6] crystallizes
in a chiral space group (orthorhombic, C2221). The Ir(III)
center adopts a distorted octahedral coordination geometry and
is surrounded by one bipyridine 2 and two dFppy moieties
displaying the expected cis-arrangement of the C atoms and
trans-arrangement of the N atoms. The average bond lengths
and angles around the Ir center (Ir−Cppy 1.996 Å; Ir−Nppy
2.041 Å; Ir−Nbpy 2.136 Å; Nppy−Ir−Nppy 173.98°; Nppy−Ir−
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Figure 4. Portions of the X-ray structure of rac-[Ir(dFppy)2(1)]·[CdI3] showing the formation of infinite homochiral chains (a for the Δ
enantiomer). Short F−F and F−Cl distances are highlighted with dashed lines. Each plane is composed of homochiral 1D networks (Δ or Λ) packed
in a parallel mode. Consecutive homochiral planes are of opposite chirality, with the packing depicted along the 1D direction (b) and along the c axis
(c). The Δ enantiomers are depicted in blue while the Λ enantiomers are colored in red. The chlorinated solvent molecules are depicted in yellow.
EtOH solvent molecules and H atoms have been omitted for clarity.
Cppy 77.38°; Nbpy−Ir−Nbpy 80.67°) are similar to those
observed for the racemic iridium complex discussed above.
Synthesis of racemic and enantiopure Ir(III)−Cd(II)
heterometallic coordination networks. The formation of
coordination networks was first attempted by combining the
racemic mixture of enantiomers rac-[Ir(dFppy)2(1)][PF6] as
metallatectons with different metallic centers. As a metallic
node, CdI2 salt was chosen because Cd(II) may adopt an
octahedral geometry with the two apical positions occupied by
the two I− anions. Diffusion of an EtOH solution of CdI2
through a EtOH/Cl2CHCHCl2 buffer layer containing two
drops of trifluoroethanol and 4,4,4-trifluorobutanol into a
solution of rac-[Ir(dFppy)2(1)][PF6] in 1,1,2,2-tetrachloro-
ethane led to the formation of orange single crystals within 2
weeks. Although for the combination of rac-[Ir(dFppy)2(1)]+
behaving as a linear bis-monodentate metallatecton with CdI2
one would expect the formation of a 2D grid-type
architecture,13,25j,41 the structural study revealed another type
of architecture. The crystal (space group C2/c) is composed of
the iridium complex [Ir(dFppy)(1)]+, Cd2+ cations, I− anions,
and solvent molecules (EtOH, Cl2CHCHCl2) (Figure 4).
It is worth noticing that solvent molecules were not
distorted octahedral coordination geometry with bond lengths
and angles (Ir−Cppy 2.013(7) Å; Ir−Nppy 2.048(6) Å; Ir−Nbpy
2.130(4) Å; Nppy−Ir-Nppy 175.3(3)°; Nppy−Ir-Cppy 80.8(3)°;
Nbpy−Ir-Nbpy 77.1(2)°) close to those observed for the discrete
metallatecton. While the dFppy ligands are almost planar
(dihedral angle Nppy−Cppy−Cppy−Cppy 2.05°), the two pyridyl
moieties of the bipyridyl units are not coplanar (dihedral angle
Nbpy−Cbpy−Cbpy−Nbpy 8.16°). The ethynyl spacers are not
linear but bent (CC−Cbpy 171.0(8)° and Cpy-CC
176.4(8)°). Consequently, the bpy ligand is slightly curved
and the tilt angle between the terminal and central pyridyl units
of the bpy moiety (dihedral angles ranging from 16.45° to
21.09°) is slightly more pronounced than that for the discrete
metallatecton. Within the coordination network rac-[Ir-
(dFppy)2(1)]·[CdI3], the Cd center adopts a trigonal
bipyramidal coordination geometry with the two terminal
pyridyl moieties of two metallatectons occupying the apical
positions (Cd−N 2.463(5) Å; N−Cd−N 172.0(3)°) and three
iodide atoms located at the trigonal base (Cd−I 2.7635(9) Å
and 2.8114(6) Å; I−Cd−I 117.33(3)° and 121.337(15)°).
Thus, the [CdI3]− complex behaves as a two-connecting node
and bridges two consecutive metallatectons, leading thus to an
infinite 1D network (Figure 4a). The distance between two
consecutive Cd2+ cations is 25.26 Å. The linear chains are
packed in a parallel mode and slightly staggered. A rather short
Cl···F distance of ca. 2.92 Å is observed between the
chlorinated solvent molecules and the F atom in position 4
belonging to the dFppy moieties. Furthermore, two neighbor-
ing dFppy moieties display a short F−F distance (atoms in
position 2) of ca. 2.94 Å (Figure 4a). The packing of 1D chiral
networks leads to homochiral planes (Δ or Λ). Consecutive
planes are of opposite chirality and packed in a parallel fashion,
−
disordered and could all be localized. It appears that the PF6
anion was exchanged with iodide ion during the crystallization
process. This observation is interesting, since one of the
drawbacks when using a cationic metallatecton for the
generation of coordination networks is the presence of the
counterion, often occupying the empty space within the lattice.
It is also worth noting that, even though the two fluorinated
solvents, i.e. pentafluoroethanol and trifluorobutanol, were
found to be indispensable for the formation of crystals, they are
not present in the crystal lattice. The iridium center adopts a
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Figure 5. Portions of the X-ray structure of Λ-[Ir(dFppy)2(1)]·[CdI3] showing: the formation of infinite chains along the b axis and their packing in
two different sheets A (a) and B (b), and the packing of consecutive homochiral A and B sheets along the N−Cd−N axis (c) of the chains and along
the c axis (d), leading to the formation of the chiral crystal. For the sake of clarity, consecutive sheets are differentiated by color (gray for A and red
for B). MeOH solvent molecules and H atoms have been omitted for clarity.
leading thus to the formation of the crystal (Figures 4b and 4c).
The tetrachloroethane solvent molecules occupy the empty
spaces within each sheet. Between consecutive sheets, a rather
short distance of 3.44 Å between F atoms and the dFppy
centroids is observed. Again, the purity of microcrystalline
powder was ascertained by PXRD, which revealed a good
match between patterns simulated from single crystal and
experimental data (see Supporting Information).
cyclometallating unit are almost coplanar (dihedral angle in the
range −2.031 to 1.221°). The ethynyl spacers are also slightly
bent and the terminal pyridyl units tilted with respect to the
bidentate central bpy chelate (dihedral angles ranging from
−21.84° to 20.33°). The geometry around the Cd atom is again
trigonal bipyramidal with three iodine atoms occupying the
trigonal base (Cd−I 2.7734(13) Å; 2.7824(12) Å; 2.7879(8) Å
and 2.8100(8) Å; I−Cd−I 119.80(2)°; 119.58(2)°; 120.41(4)°
and 120.85(4)°) and two nitrogen atoms belonging to the
terminal pyridyl units of two distinct metallatectons in axial
positions (Cd−N 2.485(6) Å and 2.465(6) Å; N−Cd−N
174.0(3)° and 173.1(4)°). The bridging of two consecutive
enantiopure Ir metallatectons by Cd atoms leads to the
formation of infinite chiral chains with a distance of 25.32 Å
between two consecutive Cd(II) metallic nodes (Figures 5a and
5b). The parallel packing of consecutive chains leads to two
different types of sheets A and B differing by the orientation of
the dFppy units with respect to the plane defined by the three
I− anions around the Cd2+ cation and the degree of staggering.
Within sheet A, a short F−F distance of 3.12 Å between the F
atoms at position 2 of the dFppy is detected (Figure 5a and
gray layer on Figures 5c and 5d), whereas for sheet B (Figure
5b and red layer in Figures 5c and 5d), the F−F distance is
substantially larger, precluding thus any F−F interaction. It is
worth noting that, because of the use of the SQUEEZE
command related to the disorder of solvent molecules, in
particular Cl2CHCHCl2 molecules, the latter could not be
localized. Consequently, the presence of possible Cl−F
interactions between chlorinated solvent molecules and
dFppy units, as observed in the case of the rac-[Ir-
(dFppy)2(1)]·[CdI3] coordination network, cannot be ruled
out. The formation of the crystal results from the packing of A
and B sheets in an alternate fashion (see Figures 5c and 5d).
Finally, the experimental PXRD pattern of microcrystalline
Under the same self-assembly conditions, the enantiopure Λ-
[Ir(dFppy)2(1)][PF6] complex was combined with CdI2 salt.
Diffusion of a solution of CdI2 in EtOH through a EtOH/
Cl2CHCHCl2 buffer layer with two drops of trifluoroethanol
and 4,4,4-trifluorobutanol into a solution of the enantiopure Ir
metallatecton in 1,1,2,2-tetrachloroethane afforded also within
2 weeks orange single crystals. The structural investigation by
single crystal X-ray diffraction again revealed the formation of
infinite 1D networks Λ-[Ir(dFppy)2(1)]·[CdI3] (Figure 5). As
in the case of the racemic mixture discussed above, again,
−
during the self-assembly process, the PF6 counterions have
been exchanged with iodide anions. The crystal (chiral space
group C2) contains the enantiopure Λ-[Ir(dFppy)2(1)]+
tectons, [CdI3]− anions, and methanol molecules. It should
be noted that, owing to the disorder of other solvent molecules,
the structure was refined using data generated by the
SQUEEZE algorithm.37 For that reason, one cannot exclude
the presence of halogenated solvent molecules within the
crystal. Within the enantiomerically pure 1D coordination
network, the bond lengths and angles for the Λ-Ir metallatecton
moiety (average distances and angles: Ir−Cppy 2.010 Å; Ir−Nppy
2.065 Å; Ir−Nbpy 2.132 Å; Nppy−Ir−Nppy 176.0°; Nppy−Ir−Cppy
81.4°; Nbpy−Ir-Nbpy 77.1°) are similar to those observed for rac-
[Ir(dFppy)2(1)]·[CdI3] (racemic mixture) discussed above. As
in the latter case, the two central pyridyl rings of the bpy ligand
are not coplanar, exhibiting a dihedral angle of ca. 8.67°, while
the difluorophenyl and pyridyl moieties belonging to the
F
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Inorganic Chemistry
Article
powder matches the simulated pattern, confirming thus the
purity of the phase (see Supporting Information).
Luminescent properties of the discrete Ir complex
and of the two heterometallic coordination polymers.
The photophysical properties of the discrete Ir(III) complex
rac-[Ir(dFppy)2(1)][PF6] as a racemate were studied both in
solution (Figures 6a and 7a) and in the solid state (Figure 6b).
Figure 7. (a) Emission (solid lines, λexc = 360 nm) and excitation
(dotted lines, λem = 607 nm) spectra of rac-[Ir(dFppy)2(1)][PF6] in
aerated (black) and degassed (red) THF solutions at room
temperature. (b) Emission spectrum (λexc = 400 nm) of rac-
[Ir(dFppy)2(1)][PF6] in the solid state.
observed for rac-[Ir(dFppy)2(1)][PF6]. This may be attributed
to delocalization of the bipyridine π system, stabilizing its
LUMO. This is supported by similar behavior in solution
reported for ppy-cyclometalated Ir complexes bearing 2,2′-
bipyridine ligand substituted in positions 5 and 5′ with aryl
rings43 or oligo(arylene ethynylene) units.44 It should also be
noted that, in solution, the emission lifetimes are similar for rac-
[Ir(dFppy)2(1)]+ (τ = 1.97 and 0.49 μs in degassed and aerated
THF, respectively; τ = 1.52 and 0.36 μs in degassed and aerated
CH3CN, respectively) and for [Ir(dFppy)2(bpyH2)]+ (τ = 1.50
μs, degassed CH3CN).28b Finally, at room temperature, the
complex rac-[Ir(dFppy)2(1)][PF6] exhibits in degassed THF
and in the solid state quantum yields (QY) of 19% and 2%,
respectively. As described above for rac-[Ir(dFppy)2(1)][PF6],
the presence of π−π interactions (Figure 1) may account for
the low solid-state QY. It should be noted that the PXRD study
(see Supporting Information) of the sample used for the
luminescence measurements in the solid state showed that the
phase was pure.
The solid-state photophysical properties of the two
heterometallic coordination networks discussed above were
investigated (Figure 8). The absorption properties of both self-
assembled architectures are similar to those observed for the
discrete Ir complex in the solid state. Dealing with the
luminescence of the racemic and the enantiopure coordination
networks, coordination of the Cd2+ cation to the peripheral
pyridyl coordinating sites of the metallatecton 1 does not
quench the Ir-centered luminescence. Indeed, a structured
emission band is observed in both cases with two maxima at ca.
575 and 620 nm. As expected, the emission bands are slightly
red-shifted with respect to the discrete Ir complex (Δλ = 15 nm
for the emission band maximum). This can be explained
assuming that the lowest excited state has a ligand-centered
Figure 6. (a) Absorption spectra of rac-[Ir(dFppy)2(2)][PF6] in
CH3CN (blue), rac-[Ir(dFppy)2(1)][PF6] in CH3CN (solid line,
black) and in THF (dashed dotted line, gray). (b) Diffuse reflectance
spectrum of rac-[Ir(dFppy)2(1)][PF6] (black) in the solid state.
In CH3CN, the mixture of enantiomers exhibits intense
absorption bands between 240 and 400 nm (Figures 6b and
7b). These bands can be attributed to spin-allowed ligand-
centered (LC) transitions involving the dFppy and the bpy
moieties with a weak contribution of MLCT and LLCT
(ligand-to-ligand charge transfer) transitions as described
previously.28b The relatively intense absorption band between
300 and 360 nm is probably due to conjugation over the bpy
moieties, as evidenced by the absence of this band in the
absorption spectrum of rac-[Ir(dFppy)2(2)][PF6] (Figure 6a)
and as previously reported for Ir(III) complexes bearing p-
phenylene substituted bpy ligands.28b In the solid state, a strong
absorption band between 250 and 700 nm, arising from LC,
MLCT, and LLCT transitions, is observed for rac-[Ir-
(dFppy)2(1)][PF6] (Figure 6b).
The emission spectra recorded in degassed THF (Figure 7a)
and in the solid state (Figure 7b) show a structured band with
two maxima at ca. 570 and 605 nm. In both cases, in a first
approximation, the emission could be attributed to a mixture of
42
3
3MLCT (Ir → bpy) and LLCT (ppy → bpy) transitions, as
described for its analogous compound [Ir(dFppy)2(bpyH2)]+
(bpyH2 = unsubstituted 2,2′-bipyridine) (λem = 534 nm, RT,
degassed CH3CN).28b However, for rac-[Ir(dFppy)2(1)][PF6],
owing to the structured emission, an increased ligand-centered
character may be assumed for the lowest excited state. When
compared to [Ir(dFppy)2(bpyH2)]+, a bathochromic shift is
G
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Article
coordination networks, selective recognition of fluorinated
guest molecules within the pores is also foreseen.
EXPERIMENTAL SECTION
■
General. NMR spectra were recorded on Bruker Avance AV300
(300 MHz for 1H, 282 MHz for 19F, 75 MHz for 13C), Bruker Avance
AV400 (400 MHz for 1H, 100 MHz for 13C) or Bruker Avance AV500
(500 MHz for 1H, 125 MHz for 13C) spectrometers at 20 °C.
Chemicals shifts (in ppm) were determined relative to residual
1
undeuterated solvent as internal reference (CDCl3: 7.26 ppm for H
and 77.2 ppm for 13C; CD3CN: 1.94 ppm for H and 118.3 and 1.3
1
ppm for 13C). Spin multiplicities are given with the following
abbreviations: s (singlet), br s (broad singlet), d (doublet), dd
(doublet of doublet), t (triplet), q (quadruplet), m (multiplet) and
1
coupling constants (J) quoted in Hz. H NMR spectra were assigned
by standard methods combined with COSY and NOESY/ROESY
experiments. 13C NMR spectra were assigned by standard methods
combined with DEPT, HMQC and HMBC experiments. Mass
spectrometry was performed at the Service Commun d’Analyses,
́
Universite de Strasbourg. Low and high-resolution mass spectra
(positive and negative mode ESI: Electro Spray Ionization) were
recorded on Thermoquest AQA Navigator with time-of-flight detector.
Elemental analyses were performed on a Thermo Scientific Flash 2000
by the “Service Commun de Microanalyses” of the University of
Strasbourg.
Figure 8. Diffuse reflectance (a) and emission (b) spectra of the
coordination polymers, rac-[Ir(dFppy)2(1)]·[CdI3] (black) and Λ-
[Ir(dFppy)2(1)]·[CdI3] (red) in the solid state. For the two emission
spectra, λexc = 400 nm.
X-ray crystal structure data were collected on a Bruker SMART
CCD diffractometer with Mo−Kα radiation. The structures were
solved and refined using the Bruker SHELXTL Software Package using
SHELXS-97 (Sheldrick, 2014) and refined by full matrix least-squares
on F2 using SHELXL-97 (Sheldrick, 2014) with anisotropic thermal
parameters for all non-hydrogen atoms.48 The hydrogen atoms were
introduced at calculated positions and not refined (riding model).
Powder X-ray diffraction (PXRD) patterns were recorded on a Bruker
D8 AV diffractometer using Cu−Kα radiation (λ = 1.5406 Å)
operating at 40 kV and 40 mA with a scanning range between 3.8 and
50° by a scan step size of 2°/min. For comparison, simulated patterns
were calculated using the Mercury software. CCDC 1413070−
1413073 contains the supplementary crystallographic data for this
paper. These data can be obtained free of charge from the Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/
cif.
UV/vis absorption spectra in solution and in the solid state were
recorded on a PerkinElmer Lambda 650S spectrophotometer (spectra
in the solid state recorded in the reflection mode, using a 150 mm
integrating sphere and Spectralon as light spectral reference for the
reflection corrections). Wavelengths are given in nm and molar
absorption coefficients (ε) are given in M−1.cm−1. Steady-state
emission spectra in solution were recorded on a HORIBA Jobin-
Yvon IBH FL-322 Fluorolog 3 spectrometer equipped with a 450 W
xenon arc lamp, double grating excitation and emission mono-
chromators (2.1 nm mm−1 dispersion; 1200 grooves mm−1) and a
Hamamatsu R928 photomultiplier tube. Steady-state emission spectra
in the solid state were recorded on a PerkinElmer LS55 spectrometer
equipped with a Hamamatsu R928 photomultiplier tube. Emission and
excitation spectra were corrected for source intensity (lamp and
grating) and emission spectral response (detector and grating) by
standard correction curves. Emission quantum yields in solution were
measured using the method of Crosby and Demas45 using [Ru-
(bpy)3][Cl]2 in degassed acetonitrile as the standard (Φ = 0.06).46
Luminescence quantum yields in the solid state were performed by
using an absolute photoluminescence quantum yield spectrometer
Quantaurus C11347-11 (Hamamatsu, Japan) exciting the samples
from 300 to 500 nm. Time-resolved measurements were performed
using the PicoHarp 300 equipped with time correlated single photon
counting (TCSPC) system on the Fluoro Time 300 (PicoQuant),
where a laser source 375 nm (LDH-P-C-375) was applied to excite the
samples. The laser was mounted directly on the sample chamber at 90°
and collected by a PMA-C 192 M single-photon-counting detector.
Signals were collected using EasyTau software, and data analysis was
character. The binding of Cd2+ cation by the pyridyl units
should slightly affect the electronic properties of the bpy ligand,
thus modifying the LUMO energy level of the complex. The
solid-state QY value for both infinite architectures appeared to
be less than 1%, which is lower than the QY measured for the
discrete Ir complex rac-[Ir(dFppy)2(1)][PF6]. Although the
presence of iodide ions might be responsible for this decrease,
the possible reason for the lower QY cannot be discussed
further, since it might originate either from partial quenching of
the emission within the solid-state architecture or from the low
precision of the quantum yield measurements.
CONCLUSIONS
■
In conclusion, synthetic strategies for the formation of
octahedral tris(chelate) Ir(III)-based chiral metallatectons,
both as a racemic mixture of Δ and Λ enantiomers and as
enantiopure complexes bearing only achiral bidentate ligands,
have been developed. Combination of the cationic linear
metallatecton with Cd2+ iodide salt ([CdI3]−) behaving as an
anionic two-connecting node was shown to lead to the
formation of 1D chiral heterometallic Ir(III)−Cd(II) lumines-
cent coordination networks both as a racemic mixture and as
enantiomerically pure infinite architectures. The novelty of the
work presented here lies in the use of an enantiopure chiral-at-
metal Ir(III)-based metallatecton for the formation, under self-
assembly conditions, of homochiral networks in the presence of
[CdI3]− anion. Furthermore, the Ir(III)-based organometallic
metallatecton displays phosphorescence. Interestingly, the
luminescent property is maintained in the presence of Cd2+
cation used as the connecting node for the formation of the
infinite architectures. Efforts toward the formation of porous
crystalline enantiopure and luminescent materials using other
metallic nodes and/or other peripheral coordination sites are
underway. Because of the presence of fluorine atoms within the
H
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Article
performed using the commercially available FluoFit software
(PicoQuant GmbH, Germany). All solvents were spectrometric
grade. Measurements in solution were performed on optically dilute
solutions (Aλexc < 0.10). Deaerated samples were prepared by the
freeze−pump−thaw technique. Circular dichroism was performed on a
JASCO J-810 spectropolarimeter. Data was collected over a wave-
length range of 200−600 nm, at a scan speed of 100 nm/min,
bandwidth of 1 nm and data pitch of 0.1 nm. Samples were measured
at RT (23 °C) and at given concentrations using a 10 mm path length
cuvette (Starna Ltd.). Polarimetric measurements were performed on a
PerkinElmer (model 341) instrument at a wavelength of 589 nm (Na).
The [α]D values are given in 10−1 deg·cm2·g−1 and concentrations are
given in g/100 mL.
Cl)]2 were obtained as yellow solids (30 mg and 28 mg) in 40% and
37% yields, respectively. ΔΔ-[Ir(dFppy)2(μ-Cl)]2: 1H NMR, 13C
NMR and 19F NMR spectra were identical to rac-[Ir(dFppy)2(μ-Cl)]2.
[αD] (20 °C, 0.063 g/100 mL, CH2Cl2): + 205°. UV−visible
(CH2Cl2): λ (nm) (ε ×10−3 (M−1·cm−1)) 254 (73.2), 297 (29.9), 338
(12.7), 382 (6.7). ΛΛ-[Ir(dFppy)2(μ-Cl)]2: 1H NMR, 13C NMR and
19F NMR spectra were identical to rac-[Ir(dFppy)2(μ-Cl)]2. [αD] (20
°C, 0.060 g/100 mL, CH2Cl2): −183°. UV−visible (CH2Cl2): λ (nm)
(ε ×10−3 (M−1·cm−1)) 254 (70.9), 297 (28.7), 338 (12.5), 382 (6.5).
Δ- and Λ-[Ir(dFppy)2(2)][PF6]. Synthesis of the Δ- and Λ-
complexes follow the same procedure as for the parent racemic
complex starting from the enantiopure Iridium dimers (ΔΔ and ΛΛ-
[Ir(dFppy)2(μ-Cl)]2 respectively). Yellow solids (31 mg for Δ-
[Ir(dFppy)2(2)][PF6] and 28 mg for Λ-[Ir(dFppy)2(2)][PF6]) were
obtained by recrystallization from acetonitrile (3 mL) and Et2O (20
mL) in 60% and 55% yield, respectively. Δ-[Ir(dFppy)2(2)][PF6]:
Single crystals of Δ-[Ir(dFppy)2(2)][PF6] suitable for X-ray diffraction
were obtained by slow diffusion of Et2O into a CH3CN solution of the
desired complex. 1H NMR, 19F NMR and 13C NMR were identical to
rac-[Ir(dFppy)2(2)][PF6]. [α]D (20 °C, 0.049 g/100 mL, CH3CN)
−314°. UV−visible (CH3CN): λ (nm) (ε ×10−3 (M−1·cm−1)) 244
(47.6), 266 (47.5), 314 (30.4), 328 (26.4), 364 (7.0). Λ-[Ir-
(dFppy)2(2)][PF6]: 1H NMR, 19F NMR and 13C NMR were identical
to rac-[Ir(dFppy)2(2)][PF6]. [α]D (20 °C, 0.047 g/100 mL, CH3CN)
+ 311° UV−visible (CH3CN): λ (nm) (ε ×10−3 (M−1·cm−1)) 244
(46.3), 266 (47.7), 314 (29.3), 328 (25.1), 364 (7.4).
Synthesis. The synthetic procedures for compounds 2,34
dFppyH,35 rac-[Ir(dFppy)2(μ-Cl)2] and rac-[Ir(dFppy)2(2)][PF6]
are detailed in the Supporting Information. Labeling of H and C
atoms for complex rac-[Ir(dFppy)2(1)][PF6] is given in the
Supporting Information. All air sensitive and anhydrous reactions
were carried out under argon. Light sensitive reactions were protected
from light by covering with aluminum foil. The glassware was oven-
dried at 100 °C and cooled under argon flow. Commercially available
chemicals were used without further purification. 4-ethynylpyridine
was synthesized as previously described.36 Anhydrous di-isopropyl-
amine, toluene, chloroform, dichloromethane and THF were used as
supplied by commercial sources without further purification. Methanol
was dried and distilled with magnesium methoxide under argon.
rac-[Ir(dFppy)2(1)][PF6]. To a solution of rac-[Ir(dFppy)2(2)][PF6]
(0.108 g, 0.096 mmol) in a mixture of toluene/iPr2NH/CH3CN (20
mL/8 mL/1.5 mL) was added 4-ethynylpyridine (0.025 g, 0.24
mmol). After degassing the resulting yellow solution, Pd(PPh3)4 (10
mg, 0.0086 mmol) and CuI (5 mg, 0.026 mmol) were added. The
solution was heated at 70 °C overnight. Then the yellow mixture was
filtrated over Celite, washed with CH2Cl2 (3 × 5 mL) and
concentrated to dryness. The yellow powder was purified by
chromatography (Al2O3, MeOH/CH2Cl2 0% to 2%) and recrystallized
from acetonitrile (2 mL) and diethyl ether (20 mL) to afford the
product rac-[Ir(dFppy)2(1)][PF6] as an orange solid (0.055 g, 46%).
Single crystals were obtained by vapor diffusion of Et2O (15 mL) into
an acetonitrile solution containing the desired product (5 mg in 1
Δ- and Λ-[Ir(dFppy)2(1)][PF6]. The enantiopure Δ- and Λ-
complexes were obtained through a Sonogashira coupling reaction
following the procedure described above for the racemic compound
rac-[Ir(dFppy)2(1)][PF6] starting from Δ- and Λ-[Ir(dFppy)2(2)]-
[PF6] (42 mg, 0.041 mmol and 45 mg, 0.041 mmol respectively) to
afford yellow powders after recrystallization in acetonitrile/Et2O in
1
46% and 45% yield, respectively. Δ-[Ir(dFppy)2(1)][PF6]: H, 13C
and 19F NMR spectra were identical to rac-[Ir(dFppy)2(1)][PF6].
[α]D (20 °C, 0.068 g/100 mL, CH3CN): −209°. UV−visible
(CH3CN): λ (nm) (ε ×10−3 (M−1·cm−1)) 243 (49.8), 303 (40.0),
1
356 (48.2). Λ-[Ir(dFppy)2(1)][PF6]: H, 13C and 19F NMR spectra
were identical to rac-[Ir(dFppy)2(1)][PF6]. [α]D (20 °C, 0.069 g/100
mL, CH3CN): + 213°. UV−visible (CH3CN): λ (nm) (ε ×10−3 (M−1·
cm−1)) 243 (47.6), 303 (39.8), 356 (47.5).
1
3
mL). H NMR (CD3CN, 400 MHz) δ (ppm): 8.62 (dd, 4H, JH−H
=
4.4 Hz, 4JH−H = 1.5 Hz, H3′), 8.59 (d, 2H, 3J = 8.4 Hz, H3), 8.36−8.30
General procedure for the formation of rac-[Ir(dFppy)2(1)]·[CdI3]
or Λ-[Ir(dFppy)2(1)]·[CdI3]. In a test tube, a tetrachloroethane (1 mL)
solution of complex rac-[Ir(dFppy)2(1)][PF6] (or Λ-[Ir(dFppy)2(1)]-
[PF6]) (4 mg) was layered with a EtOH (1 mL) solution of CdI2 (2
mg) separated by a Cl2CHCHCl2/EtOH (1/1, 0.5 mL, containing one
drop of 2,2,2-trifluoroethanol and one drop of 4,4,4-trifluorobutanol)
buffer layer. Orange crystals of rac-[Ir(dFppy)2(1)]·[CdI3] (or Λ-
[Ir(dFppy)2(1)]·[CdI3]) were obtained after 2 weeks.
(m, 4H, H4, Ha/d), 8.11 (d, 2H, 4J = 1.7 Hz, H6), 7.93 (ddd, 2H, 3JH−H
= 8.6 Hz, 3JH−H = 7.3 Hz, 4JH−H = 1.3 Hz, Hb/c), 7.71 (dd, 2H, 3JH−H
=
=
=
=
4
3
4
5.8 Hz, JH−H = 0.9 Hz, Ha/d), 7.41 (dd, 4H, JH−H = 4.4 Hz, JH−H
3
3
4
1.6 Hz, H2′), 7.12 (ddd, 2H, JH−H = 7.5 Hz, JH−H = 5.9 Hz, JH−H
1.3 Hz, Hb/c), 6.71 (ddd, 2H, 3JH−F = 12.6 Hz, 3JH−F = 9.5 Hz, 4JH−H
2.4 Hz, Hh), 5.71 (dd, 2H, JH−F = 8.7 Hz, JH−H = 2.3 Hz, HJ). 19F
3
4
NMR (CD3CN, 282 MHz) δ (ppm): −72.91 (d, 6F, 1JF−F = 706.2 Hz,
PF6), −107.78 (d, 2F, 4JF−F = 10.8 Hz), −109.75 (d, 2F, 4JF−F = 10.28
Hz). 13C NMR (CD3CN, 125 MHz) δ (ppm): 164.4 (dd, JC−F
=
1
ASSOCIATED CONTENT
* Supporting Information
■
3
255.4 Hz, JC−F = 12.5 Hz, Ci), 164.4 (d, JC−F = 6.9 Hz, Ce/f), 162.2
S
1
3
(dd, JC−F = 259.9 Hz, JC−F = 12.7 Hz, Cg), 155.3 (C5), 153.9 (C6),
153.7 (d, JC−F = 6.0 Hz, C2, Ce/f), 151.1 (C3′), 150.9 (Ca/d), 143.2
(C4), 140.6 (Cb/c), 130.0 (C1′), 128.9 (Ck), 126.3 (C2′), 126.2 (C3),
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.inorg-
chem.5b01910.
3
125.1 (C2), 124.9 (Ca/b/c/d), 124.8 (Ca/b/c/d), 114.7 (d, JC−F = 17.8
3
Hz, CJ), 100.1 (d, JC−F = 27.2 Hz, Ch), 94.6 (C8), 88.3 (C7). UV−
Synthetic procedures for compounds 2, dFppyH, rac-
[Ir(dFppy)2(μ-Cl)2], and rac-[Ir(dFppy)2(2)][PF6]; an-
alytical (1H, 19F, 13C NMR spectra, CD spectra, single-
crystal crystallographic data, and PXRD patterns) data
(PDF)
Crystallographic data for rac-[Ir(dFppy)2(1)][PF6], Δ-
[Ir(dFppy)2(2)][PF6], rac-[Ir(dFppy)2(1)]·[CdI3], and
Λ-[Ir(dFppy)2(1)]·[CdI3] (CIF)
visible (CH3CN): λ (nm), (ε ×10−3 (M−1.cm−1)) 243 (49.8), 303
(37.5), 356 (42.4). UV−visible (THF): λ (nm), (ε ×10−3
(M−1.cm−1)) 362 (45.2). MS (ESI+): calcd for [M-PF6]+
C46H26F4Ir1N6 931.1782, found 931.1702.
ΔΔ- and ΛΛ-[Ir(dFppy)2(μ-Cl)]2. The enantiopure iridium dimers
were obtained adapting the procedure described by Lusby and co-
workers24a for their nonfluorinated analogue with slight modifications.
The crude products obtained after reaction of the racemic dimer with
L- or D-serine respectively were purified by column chromatography
(SiO2) using a mixture of CH2Cl2/CH3OH/NEt3 as eluent with a
gradient elution of 99:0:1 to 97:3:1 (instead of CH2Cl2/CH3OH/NEt3
96:3:1 only). Starting from rac-[Ir(dFppy)2(μ-Cl)]2 (150 mg, 0.123
mmol) and L- or D-serine respectively (26 mg, 0.246 mmol), the
enantiopure dimers ΔΔ-[Ir(dFppy)2(μ-Cl)]2 and ΛΛ-[Ir(dFppy)2(μ-
AUTHOR INFORMATION
■
Corresponding Authors
*E-mail: aguenet@unistra.fr.
*E-mail: planeix@unistra.fr.
I
DOI: 10.1021/acs.inorgchem.5b01910
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Inorganic Chemistry
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S. T.; Hupp, J. T. J. Am. Chem. Soc. 2011, 133, 15858−15861. (b) Son,
H.-J.; Jin, S.; Patwardhan, S.; Wezenberg, S. J.; Jeong, N. C.; So, M.;
Wilmer, C. E.; Sarjeant, A. A.; Schatz, G. C.; Snurr, R. Q.; Farha, O. K.;
Wiederrecht, G. P.; Hupp, J. T. J. Am. Chem. Soc. 2013, 135, 862−869.
(c) Williams, D. E.; Rietman, J. A.; Maier, J. M.; Tan, R.; Greytak, A.
B.; Smith, M. D.; Krause, J. A.; Shustova, N. B. J. Am. Chem. Soc. 2014,
136, 11886−11889. (d) Park, J.; Feng, D.; Yuan, S.; Zhou, H.-C.
Angew. Chem., Int. Ed. 2015, 54, 430−435.
*E-mail: hosseini@unistra.fr.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This contribution is part of an international research project,
Chiranet, funded by the European Regional Development Fund
(ERDF) under the INTERREG IV Upper Rhine Programme
and as part of the Science Offensive of the Trinational Upper
Rhine Metropolitan Region. Financial support from the
University of Strasbourg, the International Centre for Frontier
Research in Chemistry (FRC), and the LabEx CSC Strasbourg,
the Institut Universitaire de France, the CNRS, is acknowl-
edged. Elena Longhi is gratefully acknowledged for her help
with luminescence measurements.
́
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