Coordination Complexes of P-Containing Polycyclic Aromatic Hydrocarbons: Optical Properties and Solid-State Supramolecular Assembly

Article abstract of DOI:10.1021/acs.organomet.6b00715

A series of complexes including σ³,λ³-P-modified polycyclic aromatic hydrocarbon (PAH) as a ligand have been prepared showing that the ligand possesses a classical "phosphine-like" reactivity. The use of different metals (Pd(II), Cu(I), Re(I), Au(I)) having different coordination number allows tuning the optical properties of the complexes, which is dominated basically by the electronic transitions of the ligand itself. The study of the solid-state properties by mean of X-ray diffraction also shows that the combination of coordination chemistry and π-stacking interactions between the PAH ligand allows obtaining a great diversity of solid-state structures.

Full text of DOI:10.1021/acs.organomet.6b00715

Article
pubs.acs.org/Organometallics
Coordination Complexes of P‑Containing Polycyclic Aromatic
Hydrocarbons: Optical Properties and Solid-State Supramolecular
Assembly
Franco
Pierre-Antoine Bouit,*,† and Muriel Hissler*,†
̧
is Riobe,† Rozsa Szucs,†,‡ Christophe Lescop,† Regis Reau,† Laszlo Nyulaszi,*,‡
́ ́ ̋ ́ ́ ́ ́ ́
†Institut des Sciences Chimiques de Rennes UMR 6226 CNRS - Universite
General Leclerc, 35042 Rennes, France
́
de Rennes 1, Campus de Beaulieu, 263 Avenue du
́
́
‡Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, Szt. Gellert ter 4, H-1111
Budapest, Hungary
S
* Supporting Information
ABSTRACT: A series of complexes including σ3,λ3-P-
modified polycyclic aromatic hydrocarbon (PAH) as a ligand
have been prepared showing that the ligand possesses a
classical “phosphine-like” reactivity. The use of different metals
(Pd(II), Cu(I), Re(I), Au(I)) having different coordination
number allows tuning the optical properties of the complexes,
which is dominated basically by the electronic transitions of
the ligand itself. The study of the solid-state properties by
mean of X-ray diffraction also shows that the combination of
coordination chemistry and π-stacking interactions between
the PAH ligand allows obtaining a great diversity of solid-state
structures.
ligands.8a This study nicely showed how the presence of the
metal ion allows the modification of the solid-state structure of
PAHs. All these strategies use the π-surface of the PAH to
coordinate to the metal fragment. Another approach consists of
INTRODUCTION
■
Polycyclic aromatic hydrocarbons (PAHs) attract considerable
attention due to their unique electronic properties, making
them appealing for applications in molecular electronics such as
organic solar cells and field-effect transistors.1−3 Their unique
grafting the metal fragment to the PAH through a σ-bond. This
approach was used to link PAHs to Pt-acetylide (C, Figure 1),
properties stemming from the extended π-conjugation within
ferrocenyl, Ir-carbenes, Au-aryl fragments, or bipyridine
planar or curved backbones are affected by the geometries
(sizes, symmetries, boundaries, and cores) and the electronics.
rhenium tricarbonyl.9 This strategy allowed obtaining new
redox and photophysical properties linked to the presence of
the metal such as phosphorescence. These strategies are based
on the organometallic chemistry of PAHs. Recently, new
synthetic methods allowed preparing heteroatom-containing
PAHs10 such as N,11 B,12 S,13 O,14 or P.15 In the case of N- or
P-containing PAHs, the heteroatom has a crucial importance
because it allows the use of its coordination ability to prepare
new coordination complexes. In this field, the first step was
made by Draper et al., who prepared Ru(II) (D, Figure 1) and
Pd(II) complexes using their unprecedented N-containing
heterosuperbenzene as a ligand.16 The authors showed that the
presence of the metal allows new optical transitions (MLCT
based) as well as new redox properties compared to the parent
Furthermore, the π-stacking ability of these compounds allows
an efficient charge transport between the molecules.4 An
original approach to tune the properties of the PAHs or to
organize them in the solid state is to use them as ligands toward
metal complexes and benefit both electronic and structural
properties of the transition metals and the large organic π-
system. In this regard, the first examples used the concepts of π-
coordination of arene ligands toward transition metals.5 For
example, the η6-coordination of [η5-C5Me5)Fe(II)] (A, Figure
1), Cr(CO)3, Ru(p-cymene), or Rh(I)(iBu3P)2 to PAHs of
various size up to the hexa-peri-hexabenzocoronene was
developed.6 This method allowed introducing new redox
properties directly linked to the nature of the metal. This
strategy has also been successfully extended to graphene layers
and curved PAHs such as corannulene.7 The η2-coordination of
Ag(I) was also found to be an interesting approach to tune the
properties of the PAHs.8 The crystallographic structure of the
triple-decker complex B (Figure 1) revealed both inter- and
intramolecular π-stacking interactions between the PAH
Special Issue: Tailoring the Optoelectronic Properties of Organo-
metallic Compounds with Main Group Elements
Received: September 9, 2016
© XXXX American Chemical Society
A
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Figure 1. Examples of organometallic (A, B, C) and coordination complexes (D, E) using PAHs as ligands (counterions have been omitted for
clarity).
PAH.16b,17 Finally, a last method to prepare metal-containing
PAHs relies on the extension of the C-sp2 backbone around a
metalloporphyrin18 or a metallophthalocyanine unit.19 For
example, compound E (Figure 1) displays intense visible and
near-IR absorption and a very low HOMO−LUMO gap.
However, the exceptional electronic properties of the
compound come more from the presence of the porphyrinic
cycle than the presence of the metal.
We recently synthesized a P-containing PAH (L1 and L2,
Scheme 1) that showed a tunable HOMO−LUMO gap using
P-modification.15 For example, the corresponding (thio)-
oxidized derivative SL1 (Scheme 1) appeared to be an efficient
emitter in the active layer of a white-emitting OLED.20 In the
present article, we extend our strategy based on the use of P-
containing ligands as two-electron donors toward transition
metals.21 We show that the insertion of different metals
(Pd(II), Cu(I), Re(I), Au(I)) having different coordination
numbers allows tuning the optical properties of the complexes,
as has been evidenced by combined experimental and
theoretical approaches. The study of the solid-state properties
by means of X-ray diffraction also shows that the metal has a
huge impact on the supramolecular organization. These results
show how the insertion of a P atom into the PAH backbone
allows tuning both optical and supramolecular assembly using
the coordination ability of the P-ligand.
chemical property of these σ3,λ3-P-derivatives is their reactivity
toward metal ions. Reaction of L1 with one equivalent of AuCl
afforded complex AuL1 (31P NMR = +26.5 ppm) in good yield
(Scheme 1).15 The reaction of AuL1 with one equivalent of
AgOTf, then with another equivalent of σ3,λ3-P-ligand L1, led
to the formation of the complex Au(L1)2 (31P NMR = +40.8
ppm), composed of two PAHs assembled around a Au(I) metal
center (Scheme 1). The two gold complexes AuL1 and
Au(L1)2 were characterized by MS and X-ray diffraction. The
coordination chemistry of this novel family of ligands is not
limited to Au(I) chemistry. Indeed, we chose to investigate the
coordination chemistry of these ligands toward Pd(II), Cu(I),
and Re(I) ions since these metal ions exhibit different
coordination geometries (square planar, tetrahedral, and
octahedral geometries, respectively) and can accommodate
different numbers of PAH ligands in the coordination sphere.
The reaction of L1 and L2 with Cu(I), Pd(II), or Re(I)
precursors led to the formation of cationic complex Cu(L1)2
(31P NMR = −2.9 ppm) and neutral complexes Pd(L2)2 (31P
NMR = +28.6 ppm) and ReL1 (31P NMR = +3.4 ppm)
(Scheme 1). The formation of the cationic complex Cu(L1)2
and the neutral complex Pd(L2)2 results in the substitution of
two acetonitrile ligands of [Cu(CH3CN)4]PF6 and
[PdCl2(CH3CN)2] precursors by two ligands L, respectively.
For the complex Pd(L2)2, the 31P NMR spectrum revealed the
presence of only one isomer. By comparison with the related
bis-phosphole palladium complexes,22 the chemical shift at
+28.6 ppm can be attributed to a cis-configured complex.23 In
the case of Cu(L1)2, two acetonitrile ligands remain
coordinated on the Cu(I) ion, at least in the solid state. The
RESULTS AND DISCUSSION
■
Synthesis and Characterization. P-containing PAHs L1
and L2 (Scheme 1) were synthesized according to our
previously reported synthetic method.15,20 An appealing
B
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Scheme 1. Synthesis of Coordination Complexes Using P-Containing PAHs L1 and L2 as Ligands
Table 1. Selected Bond Distances (Å) and Angles (deg) for AuL1, ReL1, Au(L1)2, and Cu(L1)2 and the Reference Compound
SL1 with Estimated Standard Deviations in Parentheses
b
b
AuL1
ReL1
Au(L1)2
Cu(L1)2
SL1
a
P−C2
P−C5
C2−C3
C3−C4
C4−C5
P−Cexo
P-M
1.810(9)
1.823(9)
1.376(12)
1.452(11)
1.379(12)
1.829(10)
2.222(2)
92.5(4)
1.829(5)
1.832(6)
1.365(8)
1.447(8))
1.359(7)
1.808(6)
2.4999(16)
91.1(3)
1.805(3)
1.825(3)
1.367(4)
1.450(4)
1.361(4)
1.815(3)
1.821(3)/1.828(3)
1.830(3)/1.816(3)
1.370(4)/1.355(5)
1.445(5)/1.447(4)
1.365(5)/1.359(5)
1.808(4)
1.815(4)
1.366(6)
1.452(6)
1.351(6)
1.817(5)
1.838(3)/ 1.828(3)
2.3037(11)
92.62(13)
107.9(4)
2.2524(11)/ 2.2569(11)
91.22(15)/90.91(15)
105.50(15)/108.57(14)
C2−P−-C5
C2−P−Cexo
C5−P−Cexo
92.2(2)
105.1(4)
103.4(4)
105.6(2)
108.5(3)
103.6(2)
110.8(2)
108.6(3)
107.07(14)/105.47(15)
a
b
The second value corresponds to the second P-PAH ligand in the coordination sphere of the metal. See ref 15.
steric hindrance at the metal center probably forbids the
additional substitution of another acetonitrile ligand by the
bulky PAH L1. The complex ReL1 was prepared by reacting
the ligand L1 with ReCl(CO)5 in toluene at 80 °C under
argon.24 After purification, all these complexes were isolated
with moderate yields (55−60%) and were characterized by
NMR, MS, and X-ray diffraction.
The aromatic systems and the phosphole ring possess a
tremendous variety of complexing modes (σ- and/or η-
complexes),5−16,25 but here we have shown that σ3,λ3-P-
containing PAHs L1 and L2 display the classical “phosphine-
like” reactivity not only toward (thio)-oxidation and alkylation
but also toward different metal centers, allowing the
straightforward formation of unprecedented structures.
X-ray Crystal Structure. The chemical structures of
complexes ReL1, AuL1, Au(L1)2, and Cu(L1)2 were
confirmed by X-ray diffraction studies performed on single
crystals obtained by slow vapor diffusion of pentane into
dichloromethane solutions. The crystal data and the exper-
imental details are given in the Supporting Information.
C
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Figure 2. X-ray crystallographic structure of AuL1 with the view of the discrete dimers observed in the packing.
Figure 3. X-ray crystallographic structure of ReL1 with the view of the discrete dimers observed in the packing.
Figure 4. View of the infinite columns observed in the packing for complexes AuL1, ReL1, Au(L1)2, and Cu(L1)2.
Selected bonding parameters and angles of these complexes are
summarized in Table 1.
PAH fragment (including the P-center) is almost planar. The
difference lies in the solid-state organization of these complexes
since they do not crystallize in the same space group.
The Au(I) complex AuL1 crystallizes in the C2/c space
group of the monoclinic system (Tables 1 and S1). The
asymmetric unit contains the neutral complex AuL1 (Figure 2)
and is completed by one CH2Cl2 solvent molecule that does
not show short contact interactions with the complex AuL1. In
this derivative, the P-center of the ligand L acts as expected, as a
two-electron donor toward the Au(I) metal center (d(P−Au),
The complexes ReL1 and AuL1, having one ligand L1 in
their coordination sphere, present similar metric data for the
ligand L1, which remain basically unchanged compared to
those observed in the solid-state structure of the purely organic
compound.15 Effectively, the coordinated P-center, lying in the
sp2-C plane, has a pyramidal shape with usual valence angles,
and the C−P and C−C bond lengths are similar to those
reported for P-based PAHs (see Table 1).20 Furthermore, the
D
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Figure 5. X-ray crystallographic structure of Au(L1)2 with the view of the discrete dimers observed in the packing.
Figure 6. X-ray crystallographic structure of Cu(L1)2 with the view of the discrete dimers observed in the packing.
2.222(2) Å), and the P−Au−Cl fragment is almost linear (P−
Au−Cl, 173.07(12)°). The coordinated P-center has a distorted
tetrahedral geometry (angles are ca. 92.5° for the endocyclic
C−P−C angle), and the PAH fragment (including the P-
center) is almost planar (maximum deviation for the mean
plane, ca. 0.15 Å).
fragment hindering an efficient stacking between PAH ligands.
Nevertheless, ReL1 complex dimers, in turn, stack on each
other via weaker π−π contacts, affording, once again, an infinite
π-stacked columnar structure (Figure 4). Note that no Au−Au
interactions are observed in the case of AuL1.
The complexes Au(L1)2, Pd(L2)2,23 and Cu(L1)2, having
two PAH ligands in the coordination sphere, crystallize in the
Derivative ReL1 crystallizes in the P1 space group of the
̅
triclinic system (Tables 1 and S1). The asymmetric unit
contains a neutral complex ReL1 (Figure 3) and included 1.5
CH2Cl2 solvent molecules to complete the asymmetric unit and
do not show any short contact interaction with the complex
ReL1. The coordination sphere of the Re(I) metal center is
distorted octahedral with the coordinated chloride and
phosphorus atoms in cis-positions. The P−Re bond length is
classical for a σ3-P-center acting as a two-electron donor on a
Re(I) ion (d(P−Re), 2.4999(16) Å), and the polyaromatic
fragment (including the P-center) presents a slight deviation to
the planarity (maximum deviation for the mean plane including
the P-center, ca. 0.37 Å) and a dihedral angle of ca. 7.1°
between the mean planes of the two lateral phenanthryl
subunits.
same space group P1. Nevertheless, the different coordination
̅
sphere and coordination number of the metal ions allow
different organization of the two ligands around the metal
center and different solid-state organization.
As previously reported, derivative Au(L1)2 crystallizes in the
P1 space group of the triclinic system (Tables 1 and S1). The
̅
asymmetric unit contains complex Au(L1)2 resulting from the
coordination of two ligands L1 on a Au(I) metal center (Figure
5). One CF3SO3− triflate counterion and three CH2Cl2 solvent
molecules that do not show short contact interactions with the
complex Au(L1)2 complete the asymmetric unit. The Au(I)
metal ion is located on the inversion center related with the P1
space group, and therefore its coordination geometry is strictly
linear in this solid-state structure. The two ligands L1 are
symmetrically equivalent and form with the Au(I) metal center
a stair-like structure, avoiding intramolecular π−π interactions.
The P−Au distance (d(P−Au), 2.3037(11) Å) is slightly longer
in the derivative Au(L1)2 compared to the derivative AuL1,
which could be anticipated as a consequence of the formal
replacement of the negatively charged Cl− ligand by a second
equivalent of neutral ligand L1. As observed for the complex
AuL1, metric parameters centered on the ligands L1 are mostly
comparable with those of the P-ligand (maximum deviation for
̅
The crystal packing of complexes AuL1 and ReL1 shows that
the complexes form infinite columns (Figure 4) due to π−π
intermolecular interactions, evidenced by a close packing (short
contact distances ca. 3.4−3.5 Å) between the two planar
polyaromatic fragments. Within these columns, head-to-tail
dimers are observed with a large overlay of the two interacting
polyaromatic fragments (Figures 2 and 3). It can be noticed
that these π−π interactions are less efficient in the case of the
ReL1 complex due to the presence of a large Re(CO)4Cl
E
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a
Table 2. Experimental and Calculated UV−Vis Absorption Data
compound
ReL1
L1
L2
AuL1
Au(L1)2
Cu(L1)2
Pd(L2)2
λmax (nm)
472
472
509
494
516
502
510
578sh
fwhm (cm−1
)
3790
479
3800
3780
512
3533
482
5135
529
5390
534
λvert (nm)
527
578, 573
537
λvert (PCM) (nm)
486
521
486
523
507
611, 555
a
λmax and λvert (in nm) refer to the measured maximum and the B3LYP/def2-TZVP-calculated first vertical excitation energy, respectively.
λvert(PCM) are B3LYP/def2-TZVP data with dichloromethane solvent using the PCM solvent model.
Figure 7. Absorption spectra of compounds L1 (red), AuL1 (blue), ReL1 (light blue), Au(L1)2 (orange), Cu(L1)2 (green), and Pd(L2)2 (violet) in
CH2Cl2 (10−5 M). The TD-DFT-computed vertical excitation energies are presented above the experimental spectra. The size of the peaks
representing the excitation energies is proportional to the calculated oscillator strength.
the mean plane including the P-center, ca. 0.08 Å). The
coordinated P-centers bear a distorted tetrahedral geometry
(angles are ca. 92.6° for the endocyclic C−P−C). Finally, in the
crystal packing, infinite columns of molecules are observed due
to intermolecular π−π interactions (intermolecular contacts, ca.
3.5 Å) involving the peripheral unsaturated rings of the PAH
core of the ligands L1 (Figures 4 and 5). Note that as no
intramolecular π−π interactions occur between the two ligands
L1 within the molecular structure of Au(L1)2 (Figure 5),
likewise no infinite network of pure π−π interactions is formed
along such columnar stacked arrays. Again, no Au−Au
interactions are observed similarly to the case of AuL1. This
supramolecular structure represents, however, a nice example of
the combination of coordination chemistry and π−π inter-
actions to afford organized structures.
for the P−Cu−P angle). The P−Cu bond lengths are classical
for a phosphine σ3-P-center acting as two-electron donor on a
Cu(I) metal center (d(P−Cu), 2.2524(11) and 2.2569(11) Å).
Metric parameters observed for the two equivalents of the
ligand L1 coordinated on the Cu(I) ion are mostly similar to
those of the free ligand. This indicates that, as observed for the
coordination on the Au(I) center, coordination of the P-center
on Cu(I) does not induce a noticeable modification of the
structure of the ligand L1. The coordinated P-centers in this
complex have a distorted tetrahedral geometry. The π-surface
of one of the PAH L1 is almost planar (maximum deviation for
the mean plane including the P-center, ca. 0.09 Å), but the
second ligand bears a larger deviation of planarity (maximum
deviation for the mean plane including the P-center, ca. 0.65 Å)
with a dihedral angle of ca. 5.4° between the mean planes of the
two lateral phenanthryl subunits of the PAH core. The
orientation of the two ligands L1 coordinated on the distorted
tetrahedral metal center (angle of 47°) results in the location of
the π-surfaces of these ligands in close proximity (Figure 6).
Short contact interactions (ca. 3.2−3.3 Å) revealing intra-
molecular π−π interactions are observed along large portions of
the π-surfaces, while the mean planes of the polyaromatic cores
Derivative Cu(L1) crystallizes in the P1 space group of the
̅
2
triclinic system (Table 1). The asymmetric unit contains the
monocationic complex Cu(L1)2 (Figure 6), a BF4− counterion,
and four CH2Cl2 solvent molecules, which do not show short
contact interactions with the complex Cu(L1)2. The Cu(I)
metal center has a distorted tetrahedral geometry (angles range
between 95.97(11)° for the N−Cu−N angle and 113.87(4)°
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of each PAH L1 are almost parallel (interplanar angle, ca. 5.3°).
As a consequence, the exocylic P-Ph moieties of each of the
ligands are oriented outward from the central Cu(I) metal
center. As observed in the case of the complex Pd(L2)2, the
coordination of two PAH L1/2 on a metal center allows
organizing two PAHs involved in intramolecular π−π
interactions. In the crystal packing, complexes Cu(L1)2 stack
on each other with strong intermolecular π−π interaction
involving large portions of the π-surfaces. As a result, infinite
columnar π-stacked networks are formed (Figure 4).
These examples show how coordination chemistry allows
tuning supramolecular interactions between PAHs in the solid
state. These interactions can be intramolecular, in the
coordination sphere of the metal (compounds Cu(L1)2 and
Pd(L2)2). Nevertheless, intermolecular interactions can also
take place due to the π-stacking ability of the PAH ligand
(compounds AuL1, ReL2, Au(L1)2, and Cu(L1)2). This
property is very appealing considering the potential of this
family of compounds for optoelectronic applications. Hence,
using the same PAH -based ligand, a great diversity of solid-
state structures can be obtained only by modification of the
metallic ion. This unique property validates the strategy of
inserting a coordinating atom such as P into a PAH.
Electronic Absorption Spectra and Computations. To
evaluate the effect of the metal on the electronic properties of
the compounds, the optical properties of complexes AuL1,
ReL1, Au(L1)2, Cu(L1)2, and Pd(L2)2 were investigated by
UV−vis absorption in diluted CH2Cl2 solution. As previously
reported, the UV−vis absorption spectrum of L1 displays a
π−π* transition with classical PAH vibrational fine structures in
the visible range (λmax = 472 nm, see Table 2, Figure 7).15 For
the AuL1 and ReL1 complexes, this absorption band with
similar shape is red-shifted (Δλ = 20−40 nm) due to the Lewis
acid character of the metal ions. This trend is similar to the
effect of oxidation (or thio-oxidation) of the P-center that was
previously observed for both P-containing PAHs and phosp-
hole oligomers.15,26 This effect stabilizes the LUMO to a larger
extent than the HOMO for the gold derivative (Figure 8), the
latter having a nodal plane right at the phosphorus atom bound
to the metal center.15 In the case of the ReL1 complex, the
HOMO−LUMO difference remains virtually unaltered (note
that the HOMO contains some Re d orbital participation as
shown in Figure 8). Nevertheless, the frontier MOs of each
complexes are located basically at the ligand, and the orbitals of
the metal atoms have mainly some perturbing effect. Our TD-
DFT calculations revealed that the lowest energy transitions of
AuL1 and ReL1 are indeed basically the HOMO−LUMO
excitations (see Supporting Information). Furthermore, these
transitions are energetically well separated from the rest of the
excitations. The B3LYP/def2-TZVP-calculated vertical excita-
tion energies match favorably with the observed band maxima
positions, showing a smaller bathochromic shift for the Re than
for the Au complex (Figures 7 and 8).27
Likewise, the orbitals of the ML2-type complexes behave
similarly: HOMO, HOMO−1 and LUMO, LUMO+1 (Figure
S8 in the Supporting Information) are composed from the
HOMOs and LUMOs of the two ligands, giving rise altogether
to a pair of occupied and a pair of unoccupied orbitals. The
absorption of the ML2-type complexes is shifted somewhat in
the bathochromic direction in comparison with ML-type
complexes (Figure 7). The PAH vibronic fine structure can
also be recognized; however, this feature is more diffuse and the
bands are also getting broader, especially in the case of the Pd
derivative, where even a new shoulder emerges at the low-
energy side. The TD-DFT calculations predict four close-lying
transitions, which involve the admixture of the excitations from
the HOMO−1 and HOMO to the LUMO and LUMO+1
orbitals (shown in Figure S8 of the Supporting Information).
The numerical agreement between the calculated and the
experimental results is the best in the case of Pd(L2)2. Since
the X-ray structure of Pd(L2)2 was of poor quality, we have
optimized the structure of Pd(L1)2 at the M06-2X/LANL2DZ
and ωB97X-D/LANL2DZ levels since these functionals
account for dispersion effects, which is of high importance
for π-stacked systems. The optimized structure was basically
identical to that obtained by X-ray crystallography.28 Thus, we
have decided to use for the TD-DFT calculations the geometry
obtained by X-ray crystallography, but using the smaller L1
ligand instead of the experimentally investigated L2. Since L1
and L2 have the same absorption band maxima (see Table 2),
this simplification has only a minor effect. As an apparent
consequence of the rather strong intramolecular π-stacking
between the ligands of Pd(L2)2, the four excitations are split in
this case significantly, and accordingly the TD-DFT calculations
predict two low-energy and medium-intensity transitions at 578
and 573 nm, in accordance with the shoulder at 578 nm on the
low-energy side of the broad band with a maximum at 510 nm,
which in turn is in reasonable agreement with the most intense
transition for Pd(L2)2 predicted at 527 nm. Complexes
Au(L1)2 and Cu(L1)2 neither exhibit the low-energy spectral
feature nor have a low-energy predicted transition energy. In
these complexes, the two ligands are rotated away from each
other, allowing weaker interactions between the two ligands. In
order to test if the π-stacking is responsible for the low-energy
feature in the spectrum, we have carried out TD-DFT
calculations on Cu(L1)2 with the two L1 ligands optimized
at “cis” and “trans” position (neglecting the two acetonitriles),
two extreme positions allowing strong or very weak interactions
between the two ligands, respectively (the optimized geo-
metries are presented in the Supporting Information). With the
ligands in trans position the B3LYP/def2-tZVP//B3LYP/6-
31G* calculations predict the four transition energies at 541,
530, 510, and 509 nm; in the case of the “cis” structure the
vertical excitation energies are at 596, 578, 501, and 500 nm,
showing that the splitting of the excitation energies is related to
the π-stacked “cis” arrangement of the two ligands. This finding
Figure 8. B3LYP/def2-tZVP//X-ray frontier MOs for ReL1 and AuL1
(L: B3LYP/def2-tZVP//B3LYP/6-31+G*).
G
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O−CH2−); 6.39 (d, 4H, 4J(H,H) = 2 Hz, Haryl); 6.89 (m, 4H, Hmeta);
gives further support to the X-ray structural arrangement of
Pd(L2)2. Since the two ligands L1 in the Cu(L1)2 complex
have a parallel displaced arrangement due to the distorted
tetrahedral geometry of the copper center (angle of 47°), the
interactions between the two ligands are not maximized,
leading to absorption properties (Table 2) close to those
calculated for the trans Cu(L1)2 complex. Altogether, these
tunable optical properties depending on the nature of the metal
show the pertinence of introducing a P atom in a PAH
backbone in order to take advantage of its coordination ability
to modify its electronic properties.
3
3
7.07 (dt, 2H, J(H,H) = 8 Hz, Hpara); 7.42 (dd, 4H, J(H,H) = 8 Hz,
Haryl); 7.48−7.62 (m, 8H, Hortho+ Haryl); 7.77 (d, 4H, 3J(H,H) = 8 Hz,
3
Haryl); 9.07 (d, 4H, J(H,H) = 8 Hz, Haryl). 31P NMR (162 MHz,
CDCl3): δ +28.6 (s). Due to solubility issues, no 13C spectrum could
be recorded. HRMS (ESI): [M − Cl]+ calcd for C116H134O8P2PdCl
1857.8272, found 1857.8211.
ReL1. L1 (30 mg, 0.04 mmol, 1 equiv) was refluxed in 10 mL of
toluene with Re(CO)5Cl (1 equiv) for 1 h. The crude solution was
evaporated, and the solid was washed with pentane to afford 10 as a
red solid (60%). 1H NMR (400 MHz, CDCl3): δ 3.80 (s, 6H, OCH3);
4.11 (s, 6H, OCH3); 6.74 (m, 2H, Haryl); 7.00 (m, 2H, Haryl); 7.15−
3
3
7.50 (m, 3H, Hmeta+para); 7.81 (dd, 2H, J(H,H) = 8 Hz, J(H,H) = 8
Hz, Haryl); 8.02 (m, 2H, Hortho); 8.41 (d, 2H, 3J(H,H) = 8 Hz, Haryl) ;
9.51 (d, 2H, 3J(H,H) = 8 Hz, Haryl). 31P NMR (162 MHz, CDCl3): δ +
3.4 (s). Due to solubility issues, no 13C spectrum could be recorded.
HRMS (ESI): [M]+ calcd for C42H27O8PClRe 912.0684, found
912.0680.
CONCLUSION
■
In conclusion, we demonstrated that σ3,λ3-P-modified PAHs
possess the classical “phosphine-like” reactivity toward different
metal centers, allowing the preparation of five new complexes
having specific absorption properties. The combination of
coordination chemistry and π-stacking interactions allows
obtaining a great diversity of solid-state structures, as evidenced
by the X-ray diffraction studies. In some cases, infinite π-stacked
columns were observed. Furthermore, new solid-state organ-
ization of phosphole-based PAHs can be envisaged since the
phosphole ring possesses a tremendous variety of complexing
modes (σ- and η-coordination modes).25 This property is
unusual for PAH compounds and is directly linked to the
presence of the heteroatom in the 2D π-conjugated system.
Considering the potential of P-containing PAHs for optoelec-
tronic applications, this molecular engineering based on
coordination chemistry might lead to new promising
applications in this field.29
Crystal Structure Determination. X-ray crystallographic data for
Au(L1)2 (CCDC 861179) were previously reported.15 Single crystals
of ReL1, AuL1, and Cu(L1)2 suitable for X-ray crystal analyses were
obtained by slow vapor diffusion of pentane into dichloromethane
solutions. Single-crystal data collections were performed at 150 K with
́ ́
an APEX II Bruker-AXS (Centre de Diffractometrie, Universite de
Rennes 1, France) with Mo Kα radiation (λ = 0.710 73 Å). Reflections
were indexed and Lorentz−polarization corrected and integrated by
the DENZO program of the KappaCCD software package. The data
merging process was performed using the SCALEPACK program.30
Structure determinations were performed by direct methods with the
solving program SIR97,31 which revealed all the non-hydrogen atoms.
The SHELXL program32 was used to refine the structures by full-
matrix least-squares based on F2. All non-hydrogen atoms were refined
with anisotropic displacement parameters. Hydrogen atoms were
included in idealized positions and refined with isotropic displacement
parameters.
EXPERIMENTAL SECTION/CALCULATIONS
Single crystals of all these derivatives were always coated in
Paratone oil once removed from the mother solution and mounted at
low temperature on the diffractometer goniometer, and X-ray data
collection was performed at low temperature. Atomic scattering factors
for all atoms were taken from International Tables for X-ray
Crystallography.33 1487424, 1487422, 1487421, 1487423, and
861179 contain the supplementary crystallographic data for derivatives
ReL1, AuL1, Cu(L1)2, and Au(L1)2, respectively. These data can be
obtained free of charge from the Cambridge Crystallographic Data
Center, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (internat.)
+44-1223-336-033; e-mail: deposit@ccdc.cam.ac.uk].
■
Chemicals and Instrumentations. All experiments were
performed under an atmosphere of dry argon using standard Schlenk
techniques. Commercially available reagents were used as received
without further purification. Solvents were freshly purified using
1
13
MBraun SPS-800 drying columns. H,
C, and 31P NMR spectra
were recorded on a Bruker AM300 or AM400. H and 13C NMR
chemical shifts were reported in parts per million (ppm) relative to
Me4Si as external standard. High-resolution mass spectra were
obtained on a Varian MAT 311 or ZabSpec TOF Micromass
instrument at CRMPO, University of Rennes 1. Compounds L1/2,
AuL1, and Au(L1)2 were synthesized according to a published
procedure.15,20 UV−visible spectra were recorded at room temper-
ature on a Varian Cary 5000 spectrophotometer.
1
Density Functional Calculations. B3LYP/def2-TZVP34 and
CAM-B3LYP/def2-TZVP35 TD-DFT calculations of the complexes
were carried out at the experimentally obtained geometries (in the case
of the Pd complex using ligand L1 instead of L2), with the Gaussian
09 suite of programs.36 Geometry optimizations were carried out at
the M06-2X/LANL2DZ37 and at the ωB97X-D/LANL2DZ38 levels
for the Pd(L1)2 complex and at the B3LYP/6-31G* level for the
Cu(L1)2′ complex. In the latter case the complex with the cis and
trans-arranged L1 ligands was optimized. For the visualization of the
Kohn−Sham MOs the VMD program39 was used.
Synthesis. Cu(L1)2. L1 (23 mg, 0.04 mmol, 1 equiv) was dissolved
in 20 mL of dichloromethane. Cu(CH3CN)2BF4 (0.04 mmol, 0.5
equiv) was then added. The solution was stirred at RT for 15 min;
then the solvent was evaporated and the crude product was washed
1
with pentane to afford Cu(L1)2 as a red solid (50%). H NMR (400
MHz, CD2Cl2): δ 2.33 (s, 6H, CH3CN), 3.61 (s, 12H, OCH3); 4.03
4
(s, 12H, OCH3); 6.32 (d, 4H, J = 2 Hz, Haryl); 6.58 (m, 4H, Haryl);
7.14 (m, 4H, Hmeta); 7.27 (m, 2H, Hpara); 7.43 (m, 4H, Hortho); 7.57
(dd, 4H, 3J(H,H) = 8 Hz, 3J(H,H) = 8 Hz, Haryl); 8.00 (d, 4H,
3J(H,H) = 8 Hz, Haryl) ; 9.03 (d, 4H, 3J(H,H) = 8 Hz, Haryl). 31P NMR
(160 MHz, CD2Cl2): δ −3.1 (brs). Due to solubility issues, no 13C
spectrum could be recorded. HRMS (ESI): [M − 2CH3CN]+ calcd for
C76H54O8P2Cu 1219.2584, found 1219.2523.
ASSOCIATED CONTENT
■
S
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.6b00715.
Pd(L2)2. L2 (29 mg, 0.04 mmol, 1 equiv) was dissolved in 20 mL of
dichloromethane. PdCl2(CH3CN)2 (0.04 mmol, 0.5 equiv) was then
added. The solution was stirred at RT for 15 min; then the solvent was
evaporated and the crude product was washed with pentane to afford
Pd(L2)2 as a red solid (75%). 1H NMR (300 MHz, CDCl3): δ 0.95 (t,
Additional information (PDF)
AUTHOR INFORMATION
3
3
■
12H, J(H,H) = 6 Hz, −CH3); 0.95 (t, 6H, J(H,H) = 6 Hz, −CH3);
3
Corresponding Author
*E-mail: muriel.hissler@univ-rennes1.fr.
1.03 (t, 6H, J(H,H) = 6 Hz, −CH3) 1.23−1.52 (m, 40H, −CH2−);
1.74 (m, 16H, −CH2−); 2.08 (m, 8H, −CH2−); 3.92−4.31 (m, 16H,
H
DOI: 10.1021/acs.organomet.6b00715
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
S.; Girovsky, J.; Nijs, T.; Martens, S. C.; Kleibert, A.; Stohr, M.; Ballav,
̈
ORCID
N.; Jung, T. A.; Gade, L. H. J. Am. Chem. Soc. 2014, 136, 9355.
Muriel Hissler: 0000-0003-1992-1814
Author Contributions
The manuscript was written through contributions of all
authors. All authors have given approval to the final version of
the manuscript.
̇
́ ́
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Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work is supported by the Minister
l’Enseignement Super
̀
e de la Recherche et de
́
ieur, the CNRS, the Region Bretagne,
́
China-French associated international laboratory in “Functional
Organophosphorus Materials”, Balaton PHC (830386K) -
FR_12_TET_A044DF3B, the French National Research
Agency (ANR)/Research Grants Council (RGC) Joint
Research Scheme (ANR MOLMAT), OTKA K 105417, and
COST CM10302 (SIPS).
Mullen, K. J. Am. Chem. Soc. 2012, 134, 17869. (b) Martin, C. J.; Gil,
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B.; Perera, S. D.; Draper, S. M. Chem. Commun. 2011, 47, 3616.
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Jia, Z.; Sattler, W.; Kymissis, I.; Steigerwald, M.; Nuckolls, C. Angew.
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