Phosphorescent ?C* Cyclometalated PtII Dibenzofuranyl-NHC Complexes - An Auxiliary Ligand Study

Article abstract of DOI:10.1002/ejic.201301398

Neutral ?C* cyclometalated Pt^II NHC complexes have recently emerged as a new class of phosphorescent emitters with high quantum efficiencies, short decay lifetimes and high thermal stability, which makes them promising candidates for OLED applications. Herein, we report investigations on the photophysical properties of seven new Pt^II complexes containing a chelating NHC dibenzofuranyl ligand (3-methyl-1-dibenzo[b,d]furan-4- ylimidazole) and a bidentate monoanionic auxiliary ligand. All complexes have been fully characterized including extensive NMR studies (COSY, HSQC, HMBC, NOESY, ¹⁹⁵Pt NMR), three of them also by solid-state structures. The extraordinary influence of the auxiliary ligands on the photoluminescence properties is demonstrated by quantum yields ranging from 0 % to 91 % in amorphous PMMA films at room temperature. DFT calculations were performed in order to investigate the nature of the emissive states in more detail. Copyright

Full text of DOI:10.1002/ejic.201301398

FULL PAPER
DOI:10.1002/ejic.201301398
II
∧
Phosphorescent C C* Cyclometalated Pt Dibenzo-
furanyl-NHC Complexes – An Auxiliary Ligand Study
Alexander Tronnier,[a] Nicole Nischan,[a] Stefan Metz,[b]
Gerhard Wagenblast,[b] Ingo Münster,[b] and Thomas Strassner*[a]
Keywords: NHC ligands / Platinum / Organometallic complexes / Luminescence / X-ray diffraction
∧
Neutral C C* cyclometalated PtII NHC complexes have re- been fully characterized including extensive NMR studies
cently emerged as a new class of phosphorescent emitters
with high quantum efficiencies, short decay lifetimes and
high thermal stability, which makes them promising candi-
dates for OLED applications. Herein, we report investi-
gations on the photophysical properties of seven new PtII
complexes containing a chelating NHC dibenzofuranyl li-
gand (3-methyl-1-dibenzo[b,d]furan-4-ylimidazole) and a bi-
dentate monoanionic auxiliary ligand. All complexes have
(COSY, HSQC, HMBC, NOESY, 195Pt NMR), three of them
also by solid-state structures. The extraordinary influence of
the auxiliary ligands on the photoluminescence properties is
demonstrated by quantum yields ranging from 0% to 91%
in amorphous PMMA films at room temperature. DFT calcu-
lations were performed in order to investigate the nature of
the emissive states in more detail.
with a heterocyclic extension of the π-system in the cyclo-
metalating ligand, as demonstrated by dibenzofuran (DBF,
type A, Scheme 1). Complexes of this type exhibit good
quantum yields (up to 43% for R = tBu), albeit in the green
region of the visible spectrum (CIE: 0.38;0.58).[11] In 2010,
Unger et al.[12] presented a new system (type B) in which
the pyridine ring is replaced by a 3-methylimidazolylidene,
which thus increases the quantum yield significantly (90%)
and shifts the emission wavelength to the blue–green region
(CIE: 0.16;0.31). First device tests showed EQEs as high as
Introduction
Since the invention of modern luminescent organic de-
vices in 1993 by Kido et al.[1] and the pioneering work of
Thompson and Forrest on phosphorescent devices,[2] a lot
of research efforts were directed towards phosphorescent
organic light-emitting device (PhOLED) technology in aca-
demia as well as in industry.[3] Today, transition-metal com-
plexes are well known for their exceptional photolumines-
cence properties arising from spin-orbit coupling (SOC)
and triplet harvesting, which allows for theoretical quan-
tum efficiencies of 100% due to an increased phosphores-
cence rate of the normally spin-forbidden T1–S0 transi-
tion.[4]
6.2% at 300 cdm–2 and
6750 cdm–2.
a maximum luminance of
Especially neutral iridium(III)[5] and platinum(II)[6] com-
pounds with cyclometalated ligands featuring extended π-
systems in the ligand backbone have been found to show
promising luminescence properties.
Since the introduction of different classes of cyclomet-
alated PtII emitters,[7] bidentate C N cyclometalating li-
∧
Scheme 1. Examples of cyclometalated PtII dibenzofuranyl com-
plexes (R = tBu, 3,4-dibutoxyphenyl).
gands,[8] tridentate systems[9] and various tetradentate[10]
motives have been investigated. For complexes with a bi-
dentate ligand, the common acetylacetonate and derivatives
thereof are often used as monoanionic auxiliary ligands. A
very promising class of PtII emitters comprises complexes
However, the system showed comparatively long decay
times and tended to form excimers at higher concentrations.
Since the photophysical properties of this complex are
∧
dominated by the C C* cyclometalating ligand, we herein
[a] Physical Organic Chemistry, Technische Universität Dresden,
Bergstrasse 66, 01069 Dresden, Germany
E-mail: thomas.strassner@chemie.tu-dresden.de
http://www.chm.tu-dresden.de/oc3/
report a series of different auxiliary ligands and their effects
on the emission behaviour. The emission wavelengths of
these complexes were predicted a priori by using a recently
developed method[13] to create a set of compounds with
emission maxima ranging from the blue to green region of
the visible spectrum.
[b] BASF SE,
67056 Ludwigshafen, Germany
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201301398.
Eur. J. Inorg. Chem. 2014, 256–264
256
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
Scheme 2. Preparation of the ligand precursor 1.[12]
at elevated temperature followed by the reaction with the
auxiliary ligand in the presence of potassium tert-buta-
nolate as a base.
Results and Discussion
Synthesis
The compounds were obtained in yields of 3% to 48%.
Because of the formation of two isomers during the synthe-
sis and the more challenging workup, especially complexes
3e–3g could only be obtained in low yields. Indeed, from
the reaction with 4,4,4-trifluoro-1-(thiophen-2-yl)butane-
1,3-dione, only 3e could be obtained as a pure compound
by slow crystallization from a mixture with the isomeric
complexes in a 1:1 ratio. Compounds 3f and 3g could be
separated by flash chromatography and individually charac-
terized.
The synthesis of the ligand precursor 3-methyl-1-di-
benzo[b,d]-furan-4-ylimidazolium iodide (1) was previously
reported (Scheme 2).[12] It starts with the selective lithiation
and subsequent bromination of the commercially available
dibenzofuran, followed by an Ullmann-type coupling with
imidazole. In the final step the imidazolium salt is generated
by methylation at the N2 nitrogen atom in refluxing THF.
We selected six auxiliary ligands with diverse steric and
electronic properties for our study, all derived from the acet-
ylacetonato ligand. Substituents at the C1/C5 carbon atoms
include electron-donating (tBu) and -withdrawing (CF3)
groups, as well as different aryl substituents. Two unsym-
metric ligands were included to probe for the possible for-
mation of isomers and different photophysical properties
Characterization
All complexes were characterized by standard tech-
arising from the binding mode. Most of these auxiliary li- niques. The formation of an NHC-bound cyclometalated
gands are commercially available, dimesitoylmethane and species was verified by the disappearance of the imid-
the β-ketoimine ligand (Z)-3-amino-1-phenylbut-2-en-1-one azolium proton and the formation of a different coupling
1
(2) have been synthesized.
pattern for the cyclometalated ring in the H NMR spec-
The complexes (Scheme 3) were prepared in a one-pot trum. 2D NMR measurements reveal the carbene carbon
synthesis according to our established route: deprotonation signal at about 150 ppm and proton coupling patterns be-
of the imidazolium salt with silver(I) oxide and subsequent tween hydrogen atoms from the NHC and the auxiliary li-
formation of a silver(I) NHC complex, transmetalation to gands. The exact binding mode for 3f and 3g was verified
dichloro(1,5-cyclooctadiene)platinum(II), cyclometalation by 2D NMR spectra. In the NOESY/ROESY experiments,
Scheme 3. Synthesized complexes 3a–3g.
Eur. J. Inorg. Chem. 2014, 256–264
257
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
a long-range coupling between the proton at the ketoimine
Figure 2 shows complex 3c with the most-bulky dimesit-
nitrogen atom and a proton from the NHC ligand was oylmethanato ligand. The steric demand of the mesityl
found. The distinguished patterns (see Supporting Infor- groups shields the NHC moiety and metal centre in such a
mation, Figures S1–S13) show either an interaction with the way that the molecules are forced apart and are barely able
imidazole-bound methyl group (3g) or the dibenzofuranyl to form pairs (see Supporting Information, Figure S15).
moiety (3f). The 195Pt NMR experiments show signals typi-
cal for PtII complexes of this class in the range of
–3332 ppm to –3398 ppm.
Generally, the DBF complexes are characterized by their
high melting points (over 300 °C), only those with fluorine
substituents show lower melting points (274 °C for 3e) and
even fast decomposition above 220 °C (3a).
Single-crystals suitable for X-ray diffraction measure-
ments could be obtained for 3a, 3c and 3e by slow evapora-
tion of saturated dichloromethane solutions. The solid-state
structures reveal a square-planar coordination of the cen-
tral PtII atom in which both ligands lie in one plane. While
the O2–Pt1–O3 angle shows the nearly perfect 90° angle
for square-planar coordination, the C1–Pt1–C5 angles are
significantly smaller (79.8–80.7°). Both carbon–platinum
bonds are shorter than the oxygen–platinum contacts, and
the carbene carbon–platinum bond is the shortest (1.933–
1.942 Å). Both oxygen-–platinum bond lengths differ only
slightly (2.051–2.114 Å).
Figure 2. Solid-state structure of 3c. Thermal ellipsoids are drawn
at 50% probability. Selected bond lengths [Å] and angles [°]: Pt1–
Complex 3a crystallizes in an orthorhombic crystal sys-
C1 1.942(10); Pt1–C5 2.009(10); Pt1–O2 2.067(7); Pt1–O3 2.064(7);
tem (Figure 1) with pairs of complexes forming a zig-zag
layer throughout the crystal (see Supporting Information,
Figure S14). In each pair, the molecules lie directly above
each other (distance 3.51 Å) with a Pt–Pt distance of 4.09 Å
and the NHC ligands in a face-to-face arrangement. This
distance is well above the sum of the van der Waals radii
for platinum, therefore no interaction between the two
metal atoms is expected. Both complexes are rotated in
their respective planes because of the steric hindrance in-
duced by the bulky CF3 groups.
C1–Pt1–C5 80.3(4); O2–Pt1–O3 90.1(3); Pt1–C1–N1–C4 –1.3(11);
N1–C1–Pt1–O2 174.7(8).
Nonetheless, the perpendicular distance between two
molecules is only 3.21 Å, albeit the NHC moieties are only
partly overlapping and the shortest Pt–Pt distance is 7.70 Å.
The dihedral angle S1–C20–C21–O2 is found to be only
5.2° in the solid-state structure of 3e, which puts the thienyl
moiety in the same plane with the other ligands (Figure 3).
The thienyl heterocycle is held in place by two hydrogen
bonds to neighbouring molecules (H–O 2.61 Å, H–F
2.62 Å) and by π–π interaction with the second molecule of
Figure 1. Solid-state structure of 3a. Thermal ellipsoids are drawn
at 50% probability. Selected bond lengths [Å] and angles [°]: Pt1–
Figure 3. Solid-state structure of 3e. Thermal ellipsoids are drawn
at 50% probability. Selected bond lengths [Å] and angles [°]: Pt1–
C1 1.933(16); Pt1–C5 1.995(15); Pt1–O2 2.114(11); Pt1–O3 C1 1.933(4); Pt1–C5 1.990(4); Pt1–O2 2.094(3); Pt1–O3 2.051(3);
2.071(11); C1–Pt1–C5 79.8(7); O2–Pt1–O3 88.9(4); Pt1–C1–N1–C4
–0.5(18); N1–C1–Pt1–O2 177.2(12).
C1–Pt1–C5 80.66(18); O2–Pt1–O3 89.42(12); Pt1–C1–N1–C4
–3.2(5); N1–C1–Pt1–O2 175.1(3); S1–C20–C21–O2 5.2(5).
Eur. J. Inorg. Chem. 2014, 256–264
258
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
the pair (see Supporting Information, Figure S16). In these
pairs, the platinum atoms are nearly on top of each other
(3.42 Å) with an intermolecular distance of 3.40 Å. Both
molecules are rotated by about 180° in opposite directions
to each other, so that an acac moiety faces the opposite
NHC ligand. Furthermore, the pairs are arranged in a
nearly perfect 90° angle to each other.
All data obtained from the X-ray diffraction experiments
(see Supporting Information, Table S1) are in good agree-
ment with previously published structures, which show sim-
ilar bond lengths and angles but longer Pt–Pt dis-
tances.[6m,6n,14] The steric shielding induced by different
groups at the auxiliary ligands (especially mesityl) should
indeed be a useful tool to quench excimer formation in con-
centrated emitter films (vide infra).
Figure 4. Absorption spectra of complexes 3a–3g at room tempera-
ture (2 wt.-% in PMMA).
Photophysical Properties
To investigate the photophysical properties of the com-
plexes, the absorption (Figure 4) and emission spectra (Fig-
ure 5) were measured in amorphous poly(methyl methacry-
late) films (PMMA) at room temperature with 2 wt.-%
emitter concentration, so that no dimer formation should
take place. Additionally, the complexes were investigated as
pure amorphous emitter films (see Supporting Information,
Figure S17).
All complexes show a strong absorption below 270 nm,
1
which arises from a π–π* transition, centred on the NHC
∧
ligand. Compared to similar C C* cyclometalated systems,
Figure 5. Emission spectra of complexes 3b–3g at room tempera-
ture (2 wt.-% in PMMA).
this absorption is somewhat red-shifted because of the size
of the π-system of the DBF ligand and the therefore smaller
HOMO–LUMO gap. Further transitions at lower energies
can be ascribed to d-π* metal-to-ligand charge transfers emission spectra with the first peak at 464 nm and two ad-
(MLCTs) and spin-forbidden transitions. ditional bands at 495 and 530 nm. All other complexes,
Depending on the auxiliary ligand, the complexes show with the common feature that the auxiliary ligand carries
emission from the deep blue to the orange–red region of an aryl substituent, show only one broad band at around
the visible spectrum. We found that (like in related cases) 550 nm.
the hexafluoroacetylacetonato-substituted complex 3a
DFT calculations show that, upon excitation and conver-
shows no emission above the detection limit. For the other sion to the triplet state, the additional aryl rings at the acet-
complexes, two generally different emission profiles become ylacetonate ligand rotate into the ligand plane to form an
obvious (Figure 5). Only complexes 3b and 3c show similar extended π-system. This stabilization leads to a relocation
Table 1. Photoluminescence data (2 wt.-% in PMMA, room temperature) of cyclometalated complexes 3b–3g.
#
λexc [nm][a]
CIE: x;y[b]
λem [nm][c]
Φ[e]
τo [μs][f]
kr [103 s–1][g]
knr [103 s–1][h]
3b
355
0.160;0.318
465
83
27.4
36.5
7.4
465[d]
466
3c
3d
3e
3f
335
370
370
370
370
0.165;0.333
0.336;0.565
0.414;0.543
0.384;0.542
0.416;0.516
91
51
23
19
10
18.9
4.7
9.4
18.6
–
52.9
214.7
106.0
53.6
–
5.3
467[d]
530
205.5
352.7
236.2
–
534[d]
548
521[d]
547
538[d]
559
3g
548[d]
[a] Excitation wavelength. [b] CIE coordinates at room temperature. [c] Emission wavelength. [d] Predicted wavelength (see DFT Section).
[e] Quantum yield in % at λexc, N2 atmosphere. [f] Decay lifetimes [excited by laser pulses (355 nm, 1 ns)] given as τo = τv/f. [g] kr = f/τv.
[h] knr = (1 – f)/τv.
Eur. J. Inorg. Chem. 2014, 256–264
259
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
of the emissive π*-orbital from the NHC to the auxiliary isomer (see Supporting Information, Figure S19). For the
ligand, which facilitates a ligand-to-ligand charge transfer β-ketoiminato complexes, 3f is favoured by 20.2 kcalmol–1,
(LLCT) instead of an intraligand charge transfer (ILCT). which is in good agreement with the significantly lower
This process (LUMO relocation and stabilization) consider- yield of 3g and the results presented in the literature.[16]
ably red-shifts the emission, but in a slightly different degree
To gain further insight into the photophysical properties
depending on the ligand (see DFT Section). This effect is of the complexes, frontier molecular orbitals (FMOs) and
not observed for 3c, where the ortho methyl substituents in spin densities were computed on the optimized geometries
the mesityl group effectively block any rotation and planar- of the complexes (based on Kohn–Sham orbitals). The
ization.
qualitative analysis of the FMO composition (see Support-
For complexes 3d–3g, we observe only one broad emis- ing Information, Figures S20–S21) is in good agreement
sion band along with moderate quantum yields (Table 1). with the results obtained from the photophysical measure-
For these, the DFT calculations show a strong influence of ments. For all complexes, the HOMO is based on the NHC
the auxiliary ligand. This is not the case for complexes 3b ligand with the major contribution coming from the di-
and 3c, which retain the emission from the cyclometalated benzofuranyl unit. Participation of platinum-centred orbit-
NHC ligand with vibronic coupling. They show very prom- als is also found in all cases.
ising photophysical properties with blue emission colour
and very high quantum yields (Ͼ83%).
The spin densities (see Supporting Information, Fig-
ure S22) add credibility to the conclusions drawn from the
Remarkably, these complexes with a strong vibronic cou- frontier molecular orbitals analysis. For complexes with the
pling in the emission spectrum show the longest decay life- highest quantum yields and a blue emission colour (3b and
times and lowest radiative rate constants. These values are 3c), the spin densities are found on the NHC ligand. Com-
similar to the ones obtained for the previously presented plex 3d, which has a green emission colour (530 nm), an
dibenzofuranyl PtII complex with an acetylacetonato ligand only moderate quantum yield (51%), and an untypical
(23 μs, 90%, CIE: 0.162;0.314).[12]
short decay lifetime (4.7 μs), shows the spin density on the
Complex 3c, with 91% quantum yield, is one of the most auxiliary ligand.
effective PtII emitters so far and in the same league with the
few outstanding systems presented by other groups.[6k,6m,15]
Conclusions
We synthesized seven new complexes of the rapidly
evolving class of C C* cyclometalated platinum(II) NHC
∧
DFT Calculations
compounds. All complexes were extensively characterized
with an emphasis on their photophysical properties in view
of a potential application as phosphorescent emitters in
OLEDs. Solid-state structures for three complexes could be
obtained, which reveal the effect of the steric demand of the
auxiliary ligands and their potential impact on the stacking
behaviour in concentrated emitter films. On the basis of the
promising 1-dibenzofuranyl-3-methylimidazole fragment as
NHC ligand, the influence of different auxiliary ligands was
studied in detail. Thus, the emission colour shifted from the
blue (465 nm) to the green (559 nm) region of the visible
spectrum. Very high quantum yields of up to 91% underline
the effectiveness of cyclometalated platinum(II) emitters.
Compared to the previously reported dibenzofuranyl
complex,[12] the substitution of acetylacetone by dimesitoyl-
methane shortened the decay lifetime, while the blue emis-
sion colour and very high quantum yield are retained.
For all complexes, the optimized geometries for the
singlet- and triplet states have been calculated by DFT
methods [B3LYP/6-31G(d) level with a Hay–Wadt-ECP for
platinum]. The results obtained by these calculations agree
well with the structural data gathered from the X-ray dif-
fraction experiments (see Supporting Information,
Tables S2–S4, Figure S18). The calculations confirm that
the change in multiplicity leads to significant changes in
the optimized geometries. Apart from slightly altered bond
lengths around the metal centre, for 3a and 3d, a moderate
twist of the auxiliary ligand out of the central plane is ob-
served. Furthermore, the dihedral angles between the plane
of the metallacycle and the aryl substituents on the auxil-
iary ligand are on average 14.5° smaller in the triplet state
compared to those in the singlet geometries. This is in
agreement with our interpretation of the observed
photophysics.
A recently developed method, utilizing the BP86 func-
tional to reliably compute the emission wavelengths of tran-
sition-metal complexes, allowed us to predict the wave-
length maxima quite well (see Supporting Information,
Table S5). The maximum difference is 27 nm for 3e. For the
other complexes, especially 3b and 3c with high quantum
yields and a blue emission colour, the differences are as
small as 1 nm. In the calculations regarding the isomers of
Experimental Section
General Considerations: Solvents of at least 99.5% purity were used
throughout this study. 1,4-Dioxane and DMF were dried by using
standard techniques and stored under an argon atmosphere over
molecular sieves (4 Å). Dichloro(1,5-cyclooctadiene)platinum(II)
[Pt(COD)Cl2][17] was prepared following a modified literature pro-
cedure.[12] Dimesitoylmethane[18] and 1-(dibenzo[b,d]furan-4-yl)-3-
methyl-1H-imidazol-3-ium iodide (1)[12] were prepared according
to literature procedures. (Z)-3-amino-1-phenylbut-2-en-1-one (2)[19]
the
4,4,4-trifluoro-1-(thiophen-2-yl)butane-1,3-dionato
complexes, only a small energy difference of 0.5 kcalmol–1
was found, and 3e is the thermodynamically more favoured was prepared by a modified literature procedure. Potassium tetra-
260
Eur. J. Inorg. Chem. 2014, 256–264
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
1
chloroplatinate(II) was obtained from Pressure Chemicals Co. All
other chemicals were obtained from common suppliers and used
dec. Ͼ270 °C. H NMR (300 MHz, CDCl3, 25 °C): δ = 7.91 (d, J
= 2.0 Hz, 1 H, NCH), 7.83 (d, J = 7.5 Hz, 1 H, CHarom), 7.77 (d,
J = 7.8 Hz, 1 H, CHarom), 7.54 (d, J = 7.8 Hz, 1 H, CHarom), 7.45
(d, J = 8.1 Hz, 1 H, CHarom), 7.32 (t, J = 6.8 Hz, 1 H, CHarom),
7.23 (t, J = 7.5 Hz, 1 H, CHarom), 6.79 (d, J = 2.0 Hz, 1 H, NCH),
5.80 (s, 1 H, CH), 4.08 (s, 3 H, NCH3), 1.26 (s, 9 H, CCH3), 1.16
(s, 9 H, CCH3) ppm. 13C NMR (75 MHz, CDCl3, 25 °C): δ = 194.6
(CO), 194.5 (CO), 155.7 (Ci), 150.4 (Ci), 142.4 (Ci), 130.6 (Ci),
126.1 (CHarom), 125.9 (CHarom), 125.6 (Ci), 125.1 (Ci), 122.8
(CHarom), 122.2 (Ci), 120.5 (CHarom), 120.2 (CHarom), 117.8
(CHarom), 115.4 (CHarom), 111.2 (CHarom), 92.8 (CH), 42.0 (CCH3),
41.4 (CCH3), 35.1 (NCH3), 28.7 (2 ϫ CCH3) ppm. 195Pt NMR
(64 MHz, CDCl3, 25 °C): δ = –3376.0 ppm. C27H30N2O3Pt
(625.64): calcd. C 51.83, H 4.83, N 4.48; found C 51.69, H 4.82, N
4.39.
1
without further purification. H, 13C, 19F and 195Pt NMR spectra
1
were recorded on a Bruker NMR spectrometer. H and 13C NMR
spectra were referenced internally by using the resonances of the
solvent (1H: 7.26, 13C: 77.0 for CDCl3; 1H: 2.50, 13C: 39.43 for
[D6]DMSO). 19F NMR spectra were referenced externally against
trifluoromethylbenzene (F3C–C6H5). 195Pt NMR spectra were ref-
erenced externally by using potassium tetrachloroplatinate(II) in
D2O [–1617.2 (PtCl42–), –2654.1 (PtCl2)]. Shifts are given in ppm,
coupling constants J in Hz. Elemental analyses were performed
by the microanalytical laboratory of our institute on a Hekatech
elemental analyser. Melting points have been determined by using
a Wagner and Munz Poly Therm A system and are not corrected.
The emitter films were prepared by doctor blading a solution of
emitter (2 mgmL–1) in a 10 wt.-% PMMA solution in dichloro-
methane on a substrate with a 60 μm doctor blade.
[1-(Dibenzo[b,d]furan-4-yl)-3-methyl-1H-imidazol-2-ylidene-
κC2,κC3Ј]-platinum(II)bismesitoylmethanato (3c): The synthesis
followed the general procedure. Dimesitoylmethane (987 mg) was
used. Yield: 290 mg, 48.3%. M.p. 304–306 °C. 1H NMR (500 MHz,
CDCl3, 25 °C): δ = 8.01 (d, J = 2.0 Hz, 1 H, NCH), 7.89 (d, J =
7.0 Hz, 1 H, CHarom), 7.70 (d, J = 7.8 Hz, 1 H, CHarom), 7.52 (m,
2 H, CHarom), 7.40 (m, 1 H, CHarom), 7.31 (dt, J = 0.8, J = 7.6 Hz,
1 H, CHarom), 6.89 (s, 2 H, CHarom), 6.87 (d, J = 2.0 Hz, 1 H,
NCH), 6.84 (s, 2 H, CHarom), 5.71 (s, 1 H, CH), 3.99 (s, 3 H,
NCH3), 2.38 (s, 6 H, CH3), 2.34 (s, 6 H, CH3), 2.32 (s, 3 H, CH3),
2.30 (s, 3 H, CH3) ppm. 13C NMR (125 MHz, CDCl3, 25 °C): δ =
184.8 (CO), 184.5 (CO), 155.7 (Ci), 149.2 (Ci), 142.4 (Ci), 139.6
(Ci), 139.2 (Ci), 137.7 (Ci), 137.4 (Ci), 134.2 (Ci), 133.7 (Ci), 130.6
(Ci), 128.2 (CHarom), 128.1 (CHarom), 126.2 (2ϫCHarom), 125.0
(Ci), 124.5 (Ci), 122.8 (Ci), 122.5 (CHarom), 120.8 (CHarom), 120.3
(CHarom), 117.9 (CHarom), 115.6 (CHarom), 111.2 (CHarom), 107.1
(CH), 34.8 (NCH3), 21.2 (CH3), 21.1 (CH3), 20.0 (CH3), 19.6 (CH3)
ppm. 195Pt NMR (64 MHz, CDCl3, 25 °C): δ = –3340.9 ppm.
C37H34N2O3Pt (749.78): calcd. C 59.27, H 4.57, N 3.74; found C
59.06, H 4.41, N 3.73.
(Z)-3-Amino-1-phenylbut-2-en-1-one (2): To methanol (10 mL) were
added 1-benzoylacetone (1.62 g, 10 mmol) and ammonium carb-
amate (0.78 g, 10 mmol), and the suspension was stirred for 24 h
at room temperature. The solvent was removed in vacuo, and the
residue washed with diethyl ether to give the product as a white
solid (1.21 g, 75%). M.p. 132–134 °C. 1H NMR (300 MHz, CDCl3,
25 °C): δ = 10.23 (s, 1 H, O-HNH), 7.88 (dd, J = 1.8, J = 7.8 Hz,
2 H, CHarom), 7.42 (m, 3 H, CHarom), 5.74 (s, 1 H, CH), 5.24 (s, 1
H, O-HNH), 2.06 (s, 3 H, NCCH3) ppm. 13C NMR (75 MHz,
CDCl3, 25 °C): δ = 189.5 (PhCO), 162.8 (CH3CNH2), 104.2
(CaromCO), 130.8 (CHarom), 128.2 (CHarom), 127.1 (CHarom), 92.3
(CH), 22.9 (NCCH3) ppm. C10H11NO (161.20): calcd. C 74.51, H
6.88, N 8.69; found C 74.36, H 7.22, N 8.65.
Syntheses of Complexes: The established synthetic route for the syn-
thesis of the platinum(II) complexes 3a–3g used silver(I) oxide
(93 mg, 0.4 mmol) and 1-(dibenzo[b,d]furan-4-yl)-3-methyl-1H-
imidazol-3-ium iodide 1 (301 mg, 0.8 mmol) in dry 1,4-dioxane
(20 mL) at room temperature under argon. Pt(COD)Cl2 (299 mg,
0.8 mmol) and 2-butanone (10 mL) were added to the reaction mix-
ture. The mixture was then refluxed for 21 h, and all volatile com-
pounds removed in vacuo. Afterwards, potassium tert-butanolate
(357 mg, 3.2 mmol), the corresponding auxiliary ligand (3.2 mmol)
and DMF (20 mL) were added to the crude reaction mixture. In
the last reaction step, the solution was stirred for 21 h at room
temperature and 6 h at 100 °C. Upon completion, all volatiles were
removed in vacuo, the remaining solid washed with water and dried
and the complexes isolated by flash chromatography with dichloro-
methane/isohexane as the eluent.
[1-(Dibenzo[b,d]furan-4-yl)-3-methyl-1H-imidazol-2-ylidene-
κC2,κC3Ј]-platinum(II)bisphenylacetylacetonato (3d): The synthesis
followed the general procedure. Dibenzoylmethane (732 mg) was
used. Yield: 159 mg, 29.9%. M.p. 323–325 °C. 1H NMR (300 MHz,
CDCl3, 25 °C): δ = 8.16 (m, 2 H, CHarom), 8.03 (d, J = 2.0 Hz, 1
H, NCH), 7.94 (m, 4 H, CHarom), 7.68 (d, J = 7.8 Hz, 1 H,
CHarom), 7.48 (m, 8 H, CHarom), 7.33 (dt, J = 1.0, J = 7.4 Hz, 1
H, CHarom), 6.92 (d, J = 2.0 Hz, 1 H, NCH), 6.80 (s, 1H. CH), 4.24
(s, 3 H, CH3) ppm. 13C NMR (75 MHz, CDCl3, 25 °C): δ = 180.5
(CO), 179.5 (CO), 155.8 (Ci), 149.3 (Ci), 141.2 (Ci), 140.0 (Ci),
135.4 (Ci), 132.4 (Ci), 130.8 (CHarom), 130.6 (CHarom), 128.6
(CHarom), 128.5 (CHarom), 127.3 (CHarom), 126.9 (CHarom), 126.2
(CHarom), 125.9 (CHarom), 125.0 (Ci), 124.7 (Ci), 122.8 (CHarom),
122.5 (Ci), 120.7 (CHarom), 120.3 (CHarom), 117.9 (CHarom), 115.6
(CHarom), 111.3 (CHarom), 97.4 (CH), 35.2 (NCH3) ppm. 195Pt
NMR (64 MHz, CDCl3, 25 °C): δ = –3331.7 ppm. C31H22N2O3Pt
(665.62): calcd. C 55.94, H 3.33, N 4.21; found C 55.85, H 3.30, N
4.20.
[1-(Dibenzo[b,d]furan-4-yl)-3-methyl-1H-imidazol-2-ylidene-
κC2,κC3Ј]-platinum(II)bistrifluoromethylacetylacetonato (3a): The
synthesis followed the general procedure. Hexafluoroacetylacetone
(666 mg, 0.45 mL) was used. Yield: 165 mg, 31.7 %. M.p. dec.
Ͼ220 °C. 1H NMR (300 MHz, CDCl3, 25 °C): δ = 7.83–7.86 (m, 2
H, CHarom), 7.25–7.51 (m, 5 H, CHarom), 6.80 (s, 1 H, CHarom),
6.19 (s, 1 H, CH), 3.88 (s, 3 H, NCH3) ppm. 13C NMR (125 MHz,
CDCl3, 25 °C): δ = 155.9 (Ci), 126.7 (CHarom), 125.7 (CHarom),
124.5 (Ci), 123.5 (Ci), 123.0 (CHarom), 121.2 (CHarom), 120.5
(CHarom), 118.0 (CHarom), 115.8 (CHarom), 111.3 (CHarom), 35.0
(NCH3) ppm. 19F NMR (282 MHz, CDCl3, 25 °C): δ = –75.1,
–75.4 ppm. C21H12F6N2O3Pt (649.42): calcd. C 38.84, H 1.86, N
4.31; found C 38.72, H 1.76, N 4.22.
(SP-4–4)[1-(Dibenzo[b,d]furan-4-yl)-3-methyl-1H-imidazol-2-yl-
idene-κC2,κC3Ј][4,4,4-trifluoro-1-(thiophen-2-yl)butane-1,3-di-
onato-κO,κO]platinum(II) (3e): The synthesis followed the general
procedure. 4,4,4-Trifluoro-1-(thiophen-2-yl)butane-1,3-dione
(718 mg) was used. The product was obtained as a mixture (1:1)
with the corresponding isomer after flash chromatography. The
complex was then obtained by slow crystallization from a dichloro-
methane solution of the above-mentioned mixture. Yield: 13 mg,
[1-(Dibenzo[b,d]furan-4-yl)-3-methyl-1H-imidazol-2-ylidene-
κC2,κC3Ј]-platinum(II)bistrimethylacetylacetonato (3b): The syn-
thesis followed the general procedure. 2,2,6,6-Tetramethyl-3,5-hept-
anedione (602 mg, 0.68 mL) was used. Yield: 218 mg, 43.6%. M.p.
1
2.5%. M.p. 273–275 °C. H NMR (600 MHz, CDCl3, 25 °C): δ =
Eur. J. Inorg. Chem. 2014, 256–264
261
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
8.02 (d, J = 2.0 Hz, 1 H, NCH), 7.92 (d, J = 7.5 Hz, 1 H, CHarom),
7.80 (d, J = 2.9 Hz, 1 H, CHarom), 7.70 (d, J = 4.5 Hz, 1 H,
CHarom), 7.67 (d, J = 7.8 Hz, 1 H, CHarom), 7.61 (d, J = 7.8 Hz, 1
H, CHarom), 7.54 (d, J = 8.1 Hz, 1 H, CHarom), 7.41 (d, J = 7.1 Hz,
1 H, CHarom), 7.34 (t, J = 7.1 Hz, 1 H, CHarom), 7.15 (t, J = 4.5 Hz,
1 H, CHarom), 6.95 (d, J = 2.0 Hz, 1 H, NCH), 6.51 (CH), 4.22
(NCH3) ppm. C24H15F3N2O3PtS (663.54): calcd. C 43.44, H 2.28,
N 4.22, S 4.83; found C 43.24, H 2.21, N 4.31, S 4.64.
p = 1 atm), using unscaled frequencies. For visualization,
GaussView[25] and CYLview[26] were used.
X-ray Crystallography: Preliminary examination and data collec-
tion were carried out on an area detecting system (Kappa-CCD;
Nonius, FR590) by using graphite monochromated Mo-Kα radia-
tion (λ = 0.71073 Å) with an Oxford Cryosystems cooling system
at the window of a sealed fine-focus X-ray tube. The reflections
were integrated. Raw data were corrected for Lorentz, polarization,
decay and absorption effects. The absorption correction was ap-
plied by using SADABS.[27] After merging the independent reflec-
tions were used for all calculations. The structure was solved by a
combination of direct methods[28] and difference Fourier synthe-
ses.[29] All non-hydrogen atom positions were refined with aniso-
tropic displacement parameters. Hydrogen atoms were placed in
(SP-4–4)(3-Amino-1-phenylbut-2-en-1-one-κN,κO)[1-(dibenzo-
[b,d]furan-4-yl)-3-methyl-1H-imidazol-2-ylidene-κC2,κC3Ј]-
platinum(II) (3f): The synthesis followed the general procedure. (Z)-
3-Amino-1-phenylbut-2-en-1-one (2) (516 mg) was used. After
flash chromatography, the pure isomer was obtained. Yield:
154 mg, 32%. M.p. dec. Ͼ305 °C. 1H NMR (600 MHz, CDCl3,
25 °C): δ = 8.10 (d, J = 2.0 Hz, 1 H, NCH), 7.92 (d, J = 6.9 Hz, 2
H, CHarom), 7.86 (dd, J = 1.2, J = 8.1 Hz, 2 H, CHarom), 7.61 (d,
J = 7.8 Hz, 1 H, CHarom), 7.55 (d, J = 8.1 Hz, 1 H, CHarom), 7.44–
7.35 (m, 4 H, CHarom), 7.35–7.31 (m, 2 H, CHarom), 6.92 (d, J =
2.0 Hz, 1 H, NCH), 5.72 (d, J = 2.2 Hz, 1 H, CH), 4.30 (s, 3 H,
NCH3), 2.22 (s, 3 H, CH3) ppm. 13C NMR (150 MHz, CDCl3,
25 °C): δ = 173.8 (CO), 163.9 (HNC), 161.6 (NCN), 157.0 (Ci),
143.2 (Ci), 142.1 (Ci), 131.6 (Ci), 129.1 (CHarom), 128.2 (CHarom),
126.6 (CHarom), 126.3 (CHarom), 124.8 (Ci), 123.6 (CHarom), 123.1
(CHarom), 122.8 (CHarom), 122.1 (Ci), 121.0 (CHarom), 120.3 (Ci),
117.7 (CHarom), 115.3 (CHarom), 111.3 (CHarom), 97.3 (CH), 35.1
(NCH3), 28.9 (CH3) ppm. 195Pt NMR (128 MHz, CDCl3, 25 °C):
δ = –3379.4 ppm. C26H21N3O2Pt (602.56): calcd. C 51.83, H 3.51,
N 6.97; found C 51.56, H 3.66, N 6.73.
ideal positions by using the SHELXL riding model. Full-matrix
2
least-squares refinements were carried out by minimizing Σw(Fo
–
2 2
Fc ) with the SHELXL-97 weighting scheme and stopped at shift/
err Ͻ 0.001. Details of the structure determinations are given in
the Supporting Information. Neutral-atom scattering factors for all
atoms and anomalous dispersion corrections for the non-hydrogen
atoms were taken from International Tables for Crystallography.[30]
All calculations were performed with the programs COLLECT,[31]
DIRAX,[32] EVALCCD,[33] SIR92,[28] SADABS,[27] PLATON[34]
and the SHELXL-97 package.[29,35] For visualization, Mercury[36]
and ORTEP-III[37] were used.
CCDC-948925 (3a), -948926 (3c) and -948927 (3e) contain the sup-
plementary 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.
(SP-4–3)(3-Amino-1-phenylbut-2-en-1-one-κN,κO)[1-(dibenzo-
[b,d]furan-4-yl)-3-methyl-1H-imidazol-2-ylidene-κC2,κC3Ј]-
platinum(II) (3g): The synthesis followed the general procedure.
(Z)-3-Amino-1-phenylbut-2-en-1-one (2) (516 mg) was used. After
flash chromatography, the pure isomer was obtained. Yield: 26 mg,
Supporting Information (see footnote on the first page of this arti-
cle): Experimental details and characterization data, details of the
photophysical measurements, 2D NMR spectra as well as Car-
tesian coordinates for the optimized structures are presented.
1
5%. M.p. dec. Ͼ242 °C. H NMR (600 MHz, [D6]DMSO, 25 °C):
δ = 8.78 (s, 1 H, NH), 8.09 (d, J = 2.0 Hz, 1 H, NCH), 8.05 (m, 3
H, CHarom), 7.99 (d, J = 7.7 Hz, 1 H, CHarom), 7.78 (d, J = 7.7 Hz,
1 H, CHarom), 7.70 (d, J = 8.1 Hz, 1 H, CHarom), 7.52–7.47 (m, 5
H, CHarom), 7.38 (t, J = 7.2 Hz, 1 H, CHarom), 5.91 (d, J = 2.0 Hz,
1 H, NCH), 4.03 (s, 3 H, NCH3), 2.17 (s, 3 H, CH3) ppm. 13C
NMR (150 MHz, [D6]DMSO, 25 °C): δ = 168.9 (CO), 164.6
(HNC), 154.9 (Ci), 149.3 (NCN), 141.7 (Ci), 139.9 (Ci), 138.2 (Ci),
130.1 (Ci), 129.4 (CHarom), 128.5 (CHarom), 126.4 (CHarom), 126.2
(CHarom), 125.8 (CHarom), 124.3 (Ci), 123.2 (CHarom), 123.1
(CHarom), 120.9 (Ci), 120.3 (CHarom), 116.6 (CHarom), 115.6
(CHarom), 111.5 (CHarom), 96.4 (CH), 35.8 (NCH3), 27.9 (CH3)
ppm. 195Pt NMR (128 MHz, [D6]DMSO, 25 °C): δ = –3398.1 ppm.
C26H21N3O2Pt (602.56): calcd. C 51.83, H 3.51, N 6.97; found C
51.57, H 3.45, N 6.90.
Acknowledgments
We are grateful to Dr. Fuchs (BASF), Dr. Heinemeyer (BASF) and
Dr. Lennartz (BASF) for helpful discussions. We also thank the
ZIH for computation time on their high-performance computing
facility and the Bundesministeriums für Bildung und Forschung
(BMBF) (FKZ: 13N10477) for funding.
[1] J. Kido, M. Kimura, K. Nagai, Science 1995, 267, 1332–1334.
[2] M. A. Baldo, D. F. O’Brien, Y. You, A. Shoustikov, S. Sibley,
M. E. Thompson, S. R. Forrest, Nature 1998, 395, 151–154.
[3] a) R. Meerheim, K. Walzer, G. He, M. Pfeiffer, K. Leo, Proc.
SPIE-Int. Soc. Opt. Eng. 2006, 6192, 61920P/61921–61920P/
61916; b) S. Krishnamurthy, T. K. Hatwar, J. Spindler, J. R.
Vargas, C. T. Brown, M. J. Helber, M. Ricks, W. Begley, L. Co-
simbescu, Proc. SPIE-Int. Soc. Opt. Eng. 2005, 5937, 59370N/
59371–59370N/59310; c) C.-H. Yang, Y.-M. Cheng, Y. Chi, C.-
J. Hsu, F.-C. Fang, K.-T. Wong, P.-T. Chou, C.-H. Chang, M.-
H. Tsai, C.-C. Wu, Angew. Chem. 2007, 119, 2470; Angew.
Chem. Int. Ed. 2007, 46, 2418–2421; d) C.-F. Chang, Y.-M.
Cheng, Y. Chi, Y.-C. Chiu, C.-C. Lin, G.-H. Lee, P.-T. Chou,
C.-C. Chen, C.-H. Chang, C.-C. Wu, Angew. Chem. 2008, 120,
4618; Angew. Chem. Int. Ed. 2008, 47, 4542–4545; e) K. S.
Yook, J. Y. Lee, Adv. Mater. 2012, 24, 3169–3190; f) H. Sasabe,
J. Kido, J. Mater. Chem. C 2013, 1, 1699–1707.
Computational Details: All calculations were performed with the
Gaussian09 package.[20] The density functional hybrid model
B3LYP[21] and the gradient-corrected density functional BP86[22]
were used together with the 6-31G(d)[23] basis set. No symmetry or
internal coordinate constraints were applied during optimizations.
All reported structures were verified as true minima by the absence
of negative eigenvalues in the vibrational frequency analysis. In all
cases, platinum was described by using a decontracted Hay–
Wadt(n+1) ECP and basis set.[24] Approximate free energies were
obtained through thermochemical analysis, by using the thermal
correction to the Gibbs free energy as reported by Gaussian09. This
takes into account zero-point effects, thermal enthalpy corrections
and entropy. All energies reported in this paper, unless otherwise
noted, are Gibbs free energies at standard conditions (T = 298 K,
[4] a) Y. Chi, P.-T. Chou, Chem. Soc. Rev. 2010, 39, 638–655; b)
R. C. Kwong, S. Lamansky, M. E. Thompson, Adv. Mater.
2000, 12, 1134–1138; c) H. Yersin, Top. Curr. Chem. 2004, 241,
1–26; d) H. Yersin, Highly Efficient OLEDs with Phosphores-
Eur. J. Inorg. Chem. 2014, 256–264
262
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
cent Materials, Wiley-VCH, Weinheim, Germany, 2008; e) P.-
T. Chou, Y. Chi, Chem. Eur. J. 2007, 13, 380–395.
[11]
[12]
T. Shigehiro, S. Yagi, T. Maeda, H. Nakazumi, H. Fujiwara,
Y. Sakurai, J. Phys. Chem. C 2013, 117, 532–542.
[5]
[6]
a) T. Sajoto, P. I. Djurovich, A. B. Tamayo, J. Oxgaard, W. A.
Goddard, M. E. Thompson, J. Am. Chem. Soc. 2009, 131,
9813–9822; b) T. Sajoto, P. I. Djurovich, A. Tamayo, M. Yousu-
fuddin, R. Bau, M. E. Thompson, R. J. Holmes, S. R. Forrest,
Inorg. Chem. 2005, 44, 7992–8003; c) S. Lamansky, P. Djurov-
ich, D. Murphy, F. Abdel-Razzaq, H.-E. Lee, C. Adachi, P. E.
Burrows, S. R. Forrest, M. E. Thompson, J. Am. Chem. Soc.
2001, 123, 4304–4312.
Y. Unger, D. Meyer, O. Molt, C. Schildknecht, I. Muenster, G.
Wagenblast, T. Strassner, Angew. Chem. 2010, 122, 10412; An-
gew. Chem. Int. Ed. 2010, 49, 10214–10216.
Y. Unger, T. Strassner, C. Lennartz, J. Organomet. Chem. 2013,
748, 63–67.
a) A. Tronnier, N. Nischan, T. Strassner, J. Organomet. Chem.
2013, 730, 37–43; b) M. Tenne, Y. Unger, T. Strassner, Acta
Crystallogr., Sect. C 2012, 68, m203–m205.
[13]
[14]
a) T. Strassner, Y. Unger, D. Meyer, O. Molt, I. Muenster, G.
Wagenblast, Inorg. Chem. Commun. 2013, 30, 39–41; b) A. F.
Rausch, L. Murphy, J. A. G. Williams, H. Yersin, Inorg. Chem.
2012, 51, 312–319; c) E. Rossi, A. Colombo, C. Dragonetti, D.
Roberto, R. Ugo, A. Valore, L. Falciola, P. Brulatti, M. Cocchi,
J. A. G. Williams, J. Mater. Chem. 2012, 22, 10650–10655; d)
J. A. G. Williams, Top. Curr. Chem. 2007, 281, 205–268; e) J.
Kalinowski, V. Fattori, M. Cocchi, J. A. G. Williams, Coord.
Chem. Rev. 2011, 255, 2401–2425; f) I. E. Pomestchenko, C. R.
Luman, M. Hissler, R. Ziessel, F. N. Castellano, Inorg. Chem.
2003, 42, 1394–1396; g) M. Hissler, W. B. Connick, D. K. Gei-
ger, J. E. McGarrah, D. Lipa, R. J. Lachicotte, R. Eisenberg,
Inorg. Chem. 2000, 39, 447–457; h) S.-C. Chan, M. C. W. Chan,
Y. Wang, C.-M. Che, K.-K. Cheung, N. Zhu, Chem. Eur. J.
2001, 7, 4180–4190; i) V. Adamovich, J. Brooks, A. Tamayo,
A. M. Alexander, P. I. Djurovich, B. W. DЈAndrade, C. Adachi,
S. R. Forrest, M. E. Thompson, New J. Chem. 2002, 26, 1171–
1178; j) Z. M. Hudson, C. Sun, M. G. Helander, H. Amarne,
Z.-H. Lu, S. Wang, Adv. Funct. Mater. 2010, 20, 3426–3439; k)
G. Zhou, Q. Wang, X. Wang, C.-L. Ho, W.-Y. Wong, D. Ma,
L. Wang, Z. Lin, J. Mater. Chem. 2010, 20, 7472–7484; l) Z. M.
Hudson, M. G. Helander, Z.-H. Lu, S. Wang, Chem. Commun.
2011, 47, 755–757; m) Z. M. Hudson, C. Sun, M. G. Helander,
Y.-L. Chang, Z.-H. Lu, S. Wang, J. Am. Chem. Soc. 2012, 134,
13930–13933; n) A. Tronnier, A. Risler, N. Langer, G. Wagen-
blast, I. Münster, T. Strassner, Organometallics 2012, 31, 7447–
7452.
a) M. Maestri, D. Sandrini, V. Balzani, L. Chassot, P. Jolliet,
A. von Zelewsky, Chem. Phys. Lett. 1985, 122, 375–379; b) D.
Sandrini, M. Maestri, M. Ciano, V. Balzani, R. Lueoend, C.
Deuschel-Cornioley, L. Chassot, A. von Zelewsky, Gazz. Chim.
Ital. 1988, 118, 661–665; c) F. Barigelletti, D. Sandrini, M. Ma-
estri, V. Balzani, A. von Zelewsky, L. Chassot, P. Jolliet, U.
Maeder, Inorg. Chem. 1988, 27, 3644–3647; d) C. M. Che, K. T.
Wan, L. Y. He, C. K. Poon, V. W. W. Yam, J. Chem. Soc.,
Chem. Commun. 1989, 943–944; e) M. Maestri, C. Deuschel-
Cornioley, A. von Zelewsky, Coord. Chem. Rev. 1991, 111, 117–
123; f) H. Yersin, W. Humbs, J. Strasser, Top. Curr. Chem. 1997,
191, 153–249; g) J. Brooks, Y. Babayan, S. Lamansky, P. I. Dju-
rovich, I. Tsyba, R. Bau, M. E. Thompson, Inorg. Chem. 2002,
41, 3055–3066.
[15]
a) S. C. F. Kui, P. K. Chow, G. Cheng, C.-C. Kwok, C. L.
Kwong, K.-H. Low, C.-M. Che, Chem. Commun. 2013, 49,
1497–1499; b) S. C. F. Kui, P. K. Chow, G. S. M. Tong, S.-L.
Lai, G. Cheng, C.-C. Kwok, K.-H. Low, M. Y. Ko, C.-M. Che,
Chem. Eur. J. 2013, 19, 69–73; c) E. Rossi, L. Murphy, P. L.
Brothwood, A. Colombo, C. Dragonetti, D. Roberto, R. Ugo,
M. Cocchi, J. A. G. Williams, J. Mater. Chem. 2011, 21, 15501–
15510.
A. Tronnier, A. Pöthig, E. Herdtweck, T. Strassner, submitted.
D. Drew, J. R. Doyle, Inorg. Synth. 1990, 28, 346–349.
C. Zhang, P. Yang, Y. Yang, X. Huang, X.-J. Yang, B. Wu,
Synth. Commun. 2008, 38, 2349–2356.
[16]
[17]
[18]
[19]
[20]
C. E. Rehberg, H. R. Henze, J. Am. Chem. Soc. 1941, 63, 2785–
2789.
M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone, B.
Mennucci, G. A. Petersson, H. Nakatsuji, M. Caricato, X. Li,
H. P. Hratchian, A. F. Izmaylov, J. Bloino, G. Zheng, J. L. Son-
nenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hase-
gawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai,
T. Vreven, J. A. Montgomery Jr., J. E. Peralta, F. Ogliaro, M.
Bearpark, J. J. Heyd, E. Brothers, K. N. Kudin, V. N. Starov-
erov, R. Kobayashi, J. Normand, K. Raghavachari, A. Rendell,
J. C. Burant, S. S. Iyengar, J. Tomasi, M. Cossi, N. Rega, J. M.
Millam, M. Klene, J. E. Knox, J. B. Cross, V. Bakken, C. Ad-
amo, J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev,
A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, R. L. Mar-
tin, K. Morokuma, V. G. Zakrzewski, G. A. Voth, P. Salvador,
J. J. Dannenberg, S. Dapprich, A. D. Daniels, Ö. Farkas, J. B.
Foresman, J. V. Ortiz, J. Cioslowski, D. J. Fox, Rev. B 0.1 ed.,
Gaussian, Inc., Wallingford CT, 2009.
a) A. D. Becke, J. Chem. Phys. 1993, 98, 5648–5652; b) C. Lee,
W. Yang, R. G. Parr, Phys. Rev. B 1988, 37, 785–789; c) B.
Miehlich, A. Savin, H. Stoll, H. Preuss, Chem. Phys. Lett. 1989,
157, 200–206; d) S. H. Vosko, L. Wilk, M. Nusair, Can. J. Phys.
1980, 58, 1200–1211; e) P. J. Stephens, F. J. Devlin, C. F. Chaba-
lowski, M. J. Frisch, J. Phys. Chem. 1994, 98, 11623–11627.
a) A. D. Becke, Phys. Rev. A 1988, 38, 3098–3100; b) J. P. Per-
dew, Phys. Rev. B 1986, 33, 8822–8824; c) J. P. Perdew, Phys.
Rev. B 1986, 34, 7406–7406.
a) R. Ditchfield, W. J. Hehre, J. A. Pople, J. Chem. Phys. 1971,
54, 724–728; b) W. J. Hehre, R. Ditchfield, J. A. Pople, J. Chem.
Phys. 1972, 56, 2257–2261; c) P. C. Hariharan, J. A. Pople,
Chem. Phys. Lett. 1972, 16, 217–219; d) P. C. Hariharan, J. A.
Pople, Theor. Chim. Acta 1973, 28, 213–222; e) P. C. Hariharan,
J. A. Pople, Mol. Phys. 1974, 27, 209–214; f) V. A. Rassolov,
J. A. Pople, M. A. Ratner, T. L. Windus, J. Chem. Phys. 1998,
109, 1223–1229; g) V. A. Rassolov, M. A. Ratner, J. A. Pople,
P. C. Redfern, L. A. Curtiss, J. Comput. Chem. 2001, 22, 976–
984.
a) P. J. Hay, W. R. Wadt, J. Chem. Phys. 1985, 82, 299–310; b)
P. J. Hay, W. R. Wadt, J. Chem. Phys. 1985, 82, 270–283; c)
W. R. Wadt, P. J. Hay, J. Chem. Phys. 1985, 82, 284–298.
R. Dennington II, T. Keith, J. Millam, K. Eppinnett, W. L.
Hovell, R. Gilliland, Semichem, Inc., Shawnee Mission, 2003.
[7]
[21]
[22]
[23]
[8]
J. A. G. Williams, S. Develay, D. L. Rochester, L. Murphy, Co-
ord. Chem. Rev. 2008, 252, 2596–2611.
J. A. G. Williams, A. Beeby, E. S. Davies, J. A. Weinstein, C.
[9]
Wilson, Inorg. Chem. 2003, 42, 8609–8611.
[10]
a) S. Huo, C. F. Harris, D. A. K. Vezzu, J. P. Gagnier, M. E.
Smith, R. D. Pike, Y. Li, Polyhedron 2013, 52, 1030–1040; b)
D. A. K. Vezzu, J. C. Deaton, J. S. Jones, L. Bartolotti, C. F.
Harris, A. P. Marchetti, M. Kondakova, R. D. Pike, S. Huo,
Inorg. Chem. 2010, 49, 5107–5119; c) Y.-Y. Lin, S.-C. Chan,
M. C. W. Chan, Y.-J. Hou, N. Zhu, C.-M. Che, Y. Liu, Y.
Wang, Chem. Eur. J. 2003, 9, 1263–1272; d) K. Li, X. Guan,
C.-W. Ma, W. Lu, Y. Chen, C.-M. Che, Chem. Commun. 2011,
47, 9075–9077; e) K. Li, G. Cheng, C. Ma, X. Guan, W.-M.
Kwok, Y. Chen, W. Lu, C.-M. Che, Chem. Sci. 2013, 4, 2630–
2644; f) C.-M. Che, S.-C. Chan, H.-F. Xiang, M. C. W. Chan,
Y. Liu, Y. Wang, Chem. Commun. 2004, 1484–1485; g) Y. Un-
ger, A. Zeller, S. Ahrens, T. Strassner, Chem. Commun. 2008,
3263–3265; h) X.-C. Hang, T. Fleetham, E. Turner, J. Brooks,
J. Li, Angew. Chem. Int. Ed. 2013, 52, 6753–6756.
[24]
[25]
[26]
[27]
C. Y. Legault, 1.0b ed., Université de Sherbrooke, 2009.
G. M. Sheldrick, Version 2.10 ed., University of Göttingen,
Göttingen, Germany, 2002.
Eur. J. Inorg. Chem. 2014, 256–264
263
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
[28] A. Altomare, G. Cascarano, C. Giacovazzo, A. Guagliardi,
M. C. Burla, G. Polidori, M. Camalli, J. Appl. Crystallogr.
1994, 27, 435.
[29] G. M. Sheldrick, Acta Crystallogr., Sect. A 2008, 64, 112–122.
[30] A. J. C. Wilson, Editor, International Tables for Crystallogra-
phy, Vol. C; Mathematical, Physical and Chemical Tables,
Kluwer, 1992.
[35]
[36]
G. M. Sheldrick, University of Göttingen, Göttingen, Ger-
many, 1997.
C. F. Macrae, I. J. Bruno, J. A. Chisholm, P. R. Edgington, P.
McCabe, E. Pidcock, L. Rodriguez-Monge, R. Taylor, J.
van de Streek, P. A. Wood, J. Appl. Crystallogr. 2008, 41, 466–
470.
[37] a) L. J. Farrugia, J. Appl. Crystallogr. 1997, 30, 565; b) M. N.
Burnett, C. K. Johnson, Oak Ridge National Laboratory, Oak
Ridge, TN, USA, 2000.
[31] R. W. W. Hooft, Nonius B. V., Delft, The Netherlands, 1999.
[32] A. J. M. Duisenberg, J. Appl. Crystallogr. 1992, 25, 92–96.
[33] A. J. M. Duisenberg, L. M. J. Kroon-Batenburg, A. M. M.
Schreurs, J. Appl. Crystallogr. 2003, 36, 220–229.
Received: October 31, 2013
Published Online: December 5, 2013
[34] A. L. Spek, Acta Crystallogr., Sect. D 2009, 65, 148–155.
Eur. J. Inorg. Chem. 2014, 256–264
264
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim