Luminescent cyclometallated platinum(II) complexes with N-benzoyl thiourea derivatives as ancillary ligands

Article abstract of DOI:10.1016/j.poly.2009.08.015

A series of cyclometallated 2-phenylpyridine Pt(II) complexes having N-benzoyl thiourea derivatives as ancillary ligands were prepared and characterised by elemental analysis, IR and UV-Vis spectroscopy, ¹H and ¹³C NMR spectroscopy a

Full text of DOI:10.1016/j.poly.2009.08.015

Polyhedron 28 (2009) 3739–3746
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Polyhedron
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Luminescent cyclometallated platinum(II) complexes with N-benzoyl thiourea
derivatives as ancillary ligands
b
a
c
a
a
Viorel Cîrcu a, , Mihaela Ilie , Monica Ilißs , Florea Dumitraßscu , Ionela Neagoe , Simona Pa˘sculescu
*
a Dept. of Inorganic Chemistry, University of Bucharest, 23 Dumbrava Rosie St., Sector 2, Bucharest 020464, Romania
b Dept. of Toxicology, Faculty of Pharmacy, ‘‘Carol Davila” University of Medicine and Pharmacy, 6 Traian Vuia, Bucharest, Romania
c Centre of Organic Chemistry ‘‘C. D. Nenitzescu”, Romanian Academy, Spl. Independentei 202B, Bucharest 060023, Romania
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of cyclometallated 2-phenylpyridine Pt(II) complexes having N-benzoyl thiourea derivatives as
ancillary ligands were prepared and characterised by elemental analysis, IR and UV–Vis spectroscopy,
1H and 13C NMR spectroscopy as well as by X-ray diffraction on single-crystal. All complexes were
obtained as a single isomer with N atom of the 2-phenylpyridine ligand and S atom of the N-benzoyl thio-
urea derivatives coordinated in trans positions to the platinum metal as evidenced by using X-ray crys-
tallography and NMR spectroscopy. All Pt(II) complexes show good luminescence properties at room
temperature, both in dichloromethane solution and in solid state.
Received 23 July 2009
Accepted 19 August 2009
Available online 22 August 2009
Keywords:
Cyclometallation
Platinum
Phenylpyridine
N-Benzoyl thiourea
Luminescence
Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction
plexes is assigned to either ligand centred (LC) or metal-to-ligand
charge transfer (MLCT) states or a mixed of both. In this study
Cyclometallated platinum(II) complexes represent one of the
most interesting and broadly studied class of complexes because
of their luminescence properties [1] that find applications in opto-
electronic devices [2,3], luminescent probes for biomolecules (bio-
chemistry) [4] and chemical sensors [5]. The most useful strategy
to promote luminescence in platinum(II) complexes is to employ
ligands with a very strong ligand field in order to raise the d–d
state, which can be achieved by using cyclometallating ligands,
mostly with 2-arylpyridine or 2-thienylpyridine derivatives,
resulting both homoleptic [6] or heteroleptic complexes [7].
In the case of the heteroleptic complexes, it has been clearly
demonstrated the influence of the ancillary ligand on the lumines-
cence properties of such complexes besides some advantages like:
preparation, tailoring the solubility, as well as the photophysical
properties. Amongst the ancillary ligands used to prepare mononu-
clear heteroleptic luminescent Pt(II) complexes is worth to men-
tion: bidentate ligands such as neutral diimines (bpy) or
diamines (en) [8] or bidentate anionic ligands such as acetylaceto-
nates (acac) [9] and, more recently, 8-quinolinates [10,11], bis(pyr-
azolyl) borates [12] and aminoacids [4], as well as various
monodentate ligands like Clꢀ, CO [13], RSꢀ [11,14], phosphines
[15]. In some cases the phenylpyridine ligand can be essentially re-
garded as an ancillary ligand [10]. The luminescence of Pt(II) com-
we were interested to study the influence of the N-benzoyl thio-
urea derivatives on the luminescence properties of cyclometallated
phenylpyridine Pt(II) complexes when they are used as ancillary li-
gands. These derivatives possess very strong donor groups (car-
bonyl and thioamide) which make them very attractive for use as
ligands in coordination chemistry and they are readily available
by a two-step synthesis starting from benzoylchloride and corre-
sponding amine providing access to a whole range of these deriv-
atives [16,17]. These ligands react with transition metals, mostly in
monoanionic and bidentate form by deprotonation, forming neu-
tral complexes with S, O-coordination [18]. In this paper a series
of phenylpyridine Pt(II) cyclometallated complexes bearing N-ben-
zoyl thiourea derivatives were prepared and their luminescence
properties were investigated both in solid state and in dichloro-
methane solution.
2. Results and discussion
2.1. Synthesis
The synthesis of the new compounds described here is summa-
rised in Scheme 1.
The preparation of mononuclear ortho-platinated complexes
was carried out by reacting the Pt precursor [Pt(Hppy)(ppy)(Cl)]
[19] with the sodium salts of the N-benzoyl thiourea derivatives
in dichloromethane. The new mononuclear complexes were
* Corresponding author.
E-mail address: viorel_carcu@yahoo.com (V. Cîrcu).
0277-5387/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2009.08.015

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V. Cîrcu et al. / Polyhedron 28 (2009) 3739–3746
4'
3'
2'
5'
NR1R2
N
NaBTU
CH2Cl2
6'
S
1'
Pt
Pt
N
2
3
4
Cl
O
N
N
6
5
1
2 - 13
R1 = R2 =
n-Et
2
3
4
5
6
R1 = H, R2 =
Ph
7
n-Pr
4-MeC6H4
3-MeC6H4
4-FC6H4
8
n-Bu
n-Hex
n-Oct
9
10
11
12
13
4-ClC6H4
4-BrC6H4
4-MeOC6H4
Scheme 1. Synthesis of the new complexes and the N-benzoyl thiourea derivatives used in this study.
obtained in good yields after purification on silica. They are yellow
microcrystalline solid products which are stable under atmo-
spheric conditions. Their structure was confirmed by elemental
analysis, IR spectroscopy as well as 1H and 13C NMR spectroscopy
and single-crystal X-ray diffraction.
about the C–NR1R2 bond, the alkyl groups are magnetically non-
equivalent and therefore they can be seen in the 1H and 13C NMR
spectra as two distinct sets of signals.
2.2. Description of the structures
The coordination of the N-benzoyl thiourea ancillary ligands in
monoanionic deprotonated form to the Pt centre can be easily seen
in the IR spectra. Thus, the N–H stretching frequency located
around 3250 cmꢀ1 and the strong absorption band located in the
m(C@O) frequency in the IR
spectra of free N-benzoyl thiourea derivatives disappear in the IR
Single crystals of complexes 2 and 8 suitable for X-ray diffrac-
tion were obtained by cooling a solution of these compounds in a
mixture of dichloromethane and ethanol (ca. 1/1 v/v) at ꢀ25 °C.
The crystallographic data for these two complexes are collected
in Table 1 and selected bonds and angles are presented in Table 2.
The molecular structure of compound 2 is shown in Fig. 1. Com-
plex 2 crystallised in the monoclinic crystal system, space group
P21/n, with four discrete molecules in the unit cell. The platinum
atom is surrounded by one sulfur atom and one oxygen atom of
the N-benzoyl thiourea ligand, one aromatic carbon atom (metal-
lated phenyl ring) and one nitrogen atom (pyridine ring) in an
approximately square-planar arrangement with the sulfur atom lo-
cated trans to the nitrogen atom of the pyridine ring. Both the met-
allated phenyl ring and the pyridine ring of the cyclometallated
ligand are almost coplanar with respect to the five-membered che-
late ring, the angle between the phenyl and the pyridyl rings of the
cyclometallated phenylpyridine ligand is 3.5°, whilst the phenyl
ring of the benzoyl group from the N,N-diethyl-N0-benzoyl thiourea
ligand is twisted with 29.8° with respect to the core plane.
1650–1690 cmꢀ1 range assigned to
spectra of all complexes as a result of coordination.
The 1H NMR spectroscopy indicated that all Pt(II) complexes
were obtained as single isomer (only one set of signals) which
was tentatively assigned as the isomer having N atom of the
2-phenylpyridine ligand and S atom of the N-benzoyl thiourea
derivatives coordinated in trans positions to the platinum metal,
though it is possible that complexes exist as a mixture of two
isomers. This supposition is further supported by the single-crystal
X-ray diffraction studies. The existence of only one isomer in solu-
tion was reported for other heteroleptic Pt(II) complexes bearing
2-phenylpyridine ligand [10,11].
The complexes can be divided in two groups according to their
characteristic signals presented in the 1H NMR spectra. Thus, one of
the most important features of the 1H NMR spectra is the signal as-
signed to the hydrogen H-6 which appears at 9.28–9.29 ppm in
compounds 2–6 and slightly shielded at 9.15–9.24 ppm in com-
pounds 7–13. Also, the signal assigned to H-6 is accompanied by
the 195Pt satellites with a coupling constant 3JPt–H = 33.0 Hz, similar
to other cyclometallated 2-phenylpyridine Pt(II) complexes, thus
indicating the binding of Pt to the deprotonated phenylpyridine li-
gand. The splitting pattern of the H-3, H-4 and H-5 protons signals
from the pyridine ring is typical for such complexes. The protons
H-40 and H-50 from the phenyl ring of the 2-phenylpyridine ligand
appear shielded at around 7.10 ppm. Moreover, the presence of the
195Pt satellites was evidenced in the 13C NMR spectra accompany-
ing the signals attributed to the carbon atoms of the 2-phenylpyri-
dine ligand.
The shortest Pt–Pt distance between two neighbouring mole-
cules is 8.217 Å, precluding any Pt–Pt interactions. The Pt–C and
Pt–N bond lengths are comparable with the values reported for
similar ortho-platinated complexes with phenylpyridine ligand
[13,19,20]. The Pt–S bond length, 2.239 Å, is comparable with the
two values found for the simple cis complex of Pt(II) with
N,N-diethyl-N0-benzoyl thiourea which are 2.231 and 2.233 Å,
respectively [21] and similar to that found in cis-bis(N,N-di(n-bu-
tyl)-N0-benzoylthioureato)platinum(II), 2.230(2)–2.233(2) Å [22],
the two examples available for comparison. On the other hand
the relatively long Pt–O bond length (2.076 Å) in complex 2 com-
pare
to
cis-bis(N,N-diethyl-N0-benzoylthioureato)platinum(II)
(2.018 and 2.023 Å) [21] is a consequence of the trans influence
of the coordinated carbon atom of cyclometallated 2-phenylpyri-
dine ligand.
In the case of Pt complexes bearing N,N-dialkyl-N0-benzoyl thio-
urea derivatives, complexes 2–6, due to the hindered rotation

V. Cîrcu et al. / Polyhedron 28 (2009) 3739–3746
3741
Table 1
Crystallographic data for compounds 2 and 8.
Compound
2
8
Empirical formula
Formula weight (g molꢀ1
Temperature (K)
Wavelength (Å)
Crystal system
Space group
C23H23N3OPtS
584.59
293(2)
0.71073
monoclinic
P21/n
C26H21N3OPtS
618.61
293(2)
0.71073
monoclinic
C2/c
)
Unit cell dimensions
a (Å)
b (Å)
14.9455(12)
9.7791(6)
15.5698(12)
90.00
108.498(6)
90.00
2158.0(3)
4
1.799
27.8193(15)
9.9384(9)
16.3976(13)
90.00
96.833(4)
90.00
4501.4(6)
8
1.826
c (Å)
a
(°)
b (°)
(°)
V (Å3)
c
Z
Dcalc (Mg mꢀ3
)
l
(mmꢀ1
)
6.618
6.351
F(0 0 0)
1136
2400
Colour
yellow
yellow
Crystal size (mm3)
h Range (°)
0.50 ꢂ 0.25 ꢂ 0.15
2.65–33.47
21 684
0.50 ꢂ 0.40 ꢂ 0.25
2.46–33.56
38 811
Fig. 1. The molecular structure of compound 2.
Reflections collected
Independent reflections (Rint
Data/restraints/parameters
Goodness-of-fit on F2
)
7710 (0.0757)
7710/0/264
0.995
R1 = 0.0553,
wR2 = 0.0692
R1 = 0.1172,
wR2 = 0.0800
1.400 and ꢀ2.913
8682 (0.0658)
8682/0/294
1.098
R1 = 0.0528,
wR2 = 0.1048
R1 = 0.0792,
wR2 = 0.1141
3.383 and ꢀ1.700
entation adopted by the p-tolyl ring of the N-benzoyl thiourea li-
gand with a twist of 65.1° with respect to the core plane, leading
to the formation of weak intermolecular NHꢁ ꢁ ꢁPt interactions
[23] (Hꢁ ꢁ ꢁPt 2.74 Å; N-Hꢁ ꢁ ꢁPt 156.8°) compared to those found in
the salt (NnPr4)2[PtCl4]ꢁ[PtCl2(NH2Me)2] (Fig. 3). In this example
the neutron diffraction studies [24] revealed the presence of short
intermolecular N–Hꢁ ꢁ ꢁPt interactions [Hꢁ ꢁ ꢁPt 2.262(11) Å] as well
as a weaker C–Hꢁ ꢁ ꢁPt interaction [Hꢁ ꢁ ꢁPt 2.768(9) Å; C–Hꢁ ꢁ ꢁPt
Final R indices [F2 > 2
r
(F2)]
R indices (all data)
Largest difference in peak and
hole (e Åꢀ3
)
l64.4(7) Å]. Also, intermolecular aromatic
p–p interactions are
Table 2
present that contribute to the crystalline packing of compound 8.
In this case, the shortest Pt–Pt distance between two neighbouring
molecules is 4.18 Å.
Selected bond lengths and angles for compounds 2 and 8.
2
8
Pt–C
Pt–N
Pt–O
Pt–S
N(R2)–C(S)
N–C(S)
N–C(O)
C–O
1.973(5)
2.045(5)
2.076(3)
2.2389(15)
1.341(7)
1.336(7)
1.325(7)
1.268(6)
1.738(6)
1.489(7)
80.8(2)
1.979(6)
2.035(5)
2.075(4)
2.2447(14)
1.347(8)
1.333(7)
1.325(7)
1.262(7)
1.728(6)
1.485(8)
81.1(2)
For both complexes discussed above, the bond lengths of the
thiocarbonyl [C–S 1.738(6) Å for complex 2 and 1.728(6) Å for
complex 8] and carbonyl [C–O 1.268(6) Å for complex 2 and
1.262(7) Å for complex 8] bonds are longer than the average values
of C@S and C@O bonds, whilst the C–N bonds in the chelate ring
are all shorter than the average for C–N single bonds. The latter
observation indicates extensive delocalization of electrons within
the chelate ring of these two complexes as a consequence of the
coordination of the ligands to platinum centre in the deprotonated
form which leads to the partial double-bond character of the C–N
bonds [21,22].
C–S
C(O)–C(Ph)
C–Pt–N
N–Pt–O
O–Pt–S
S–Pt–C
91.75(16)
93.22(11)
93.22(11)
91.05(17)
92.93(11)
94.93(17)
2.3. Absorption and emission properties
Compound 8 (Fig. 2) crystallised in the monoclinic crystal sys-
tem, group C2/c, with the same square–planar arrangement around
the platinum atom bound to the phenylpyridine ligand in an ortho-
metallated fashion and chelated to N-benzoyl thiourea derivative
and the same coordinated atoms (one aromatic C atom (metallated
ring), one N atom (pyridine ring), one O atom (carbonyl group) and
one S atom (thiocarbonyl group)) as found for compound 2; indeed
bond lengths and angles for the central core are all very similar to
those found in complex 2. The same orientation with respect to the
core plane was found for the two rings of the phenylpyridine li-
gand, which are almost coplanar with the five-membered chelate
ring, the angle between the phenyl and the pyridyl rings of the
cyclometallated phenylpyridine ligand is 3.5°, the same value as
found for complex 2. The phenyl ring of the benzoyl group from
the N-benzoyl thiourea ligand is also twisted in respect to the core
plane by 27.5°, a smaller value compare to that found for complex
2. An interesting feature of the structure of this complex is the ori-
The UV–Vis absorption spectra of compounds 2–13 were re-
corded in solution (about 0.02 mM in dichloromethane) and sev-
eral examples are shown in Fig. 4. The absorption and emission
data are collected in Table 3.
In order to have a better appreciation of the shape of the spectra
and their peak positions, the normalised spectra to the 258 nm
maximum were obtained (Figs. S1–S4). Complexes 2–6 have only
two well-resolved absorption maxima (at 279 nm, with a slight
bathochromic shift for compound 4, and at 375 nm with a slight
bathochromic shift for compounds 2 and 4 compared to the same
series), whilst compounds 7–13 exhibit besides the 282 nm
(hypsochromically shifted for compound 12) and 375 nm peaks,
another maximum at 258 nm (hypsochromically shifted for
compound 12). It is worth to note that for compounds 2–6, an
equivalent of the 258 nm peak can be observed in a shoulder
(254–260 nm), which could not be resolved by the measurements
in dichloromethane solution even using the most favourable

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V. Cîrcu et al. / Polyhedron 28 (2009) 3739–3746
Fig. 2. The molecular structure of compound 8.
Fig. 3. The NHꢁ ꢁ ꢁPt interactions between adjacent molecules of compound 8.
available instrumental conditions. The extinction coefficient, e, for
the absorption maximum at 258 nm is around 40 000 Mꢀ1 cmꢀ1
with a maximum of 46 500 Mꢀ1 cmꢀ1 for complex 8, except for
compound 12, which has an half-value extinction coefficient com-
pared to the other compounds of the series.
The UV–Vis spectra of these complexes do not differ too much
from the one of the homoleptic complex with 2-phenylpyridine li-
gand [Pt(ppy)2] [6] and this is why the same electronic assign-
ments are proposed.
The absorption bands located in the UV range can be assigned to
intraligand n–p* and p–p* transitions (LC) which are perturbed by
complexation to the Pt(II) metal. The free 2-phenylpyridine ligand
show similar absorption bands in same region, at 248 and 276 nm
whilst the free N-benzoyl thiourea derivatives show two absorption
bands located in the range 240–280 nm and around 310 nm, respec-
tively. The moderately intense absorptions around 375 nm for all
prepared complexes 2–13 can be assigned to spin-allowed metal-
to-ligand charge transfer MLCT (dPt
with similar Pt(II) complexes containing 2-phenylpyridine as ligand
[6]. The intensity of these absorption bands (
> 103 Mꢀ1 cmꢀ1) rules
? p*ppy) transition by analogy
Fig. 4. Normalised spectra of 0.02 mM solutions of complexes 2, 5, 8, 10 and 13 in
dichloromethane (normalisation to the 258 nm peak).
e

V. Cîrcu et al. / Polyhedron 28 (2009) 3739–3746
3743
Table 3
Absorption and emission data for complexes 2–13.
Complex
Absorption kmax/nm
Emission
Uem
(e
ꢂ 10ꢀ3/Mꢀ1 cmꢀ1
)
2
3
4
5
6
7
8
9
10
11
12
13
260(sh), 279 (82.5), 378 (14.9)
256(sh), 279 (38.3), 375 (8.5)
257(sh), 282 (38.3), 323(sh), 378 (14.7)
254(sh), 279 (26.7), 375 (9.9)
256(sh), 280 (32.7), 375 (12.5)
258 (41.1), 282 (37.7), 308(sh), 322(sh), 375(18.5)
257 (46.5), 282 (37.5), 310(sh), 322(sh), 375 (21.0)
258 (38.2), 282 (30.9), 309(sh), 324(sh), 375 (17.2)
258 (40.3), 282(35.4), 310(sh), 373 (17.3)
259 (40.4), 281 (34.3), 310(sh), 322(sh), 374 (18.9)
256 (23.7), 278 (20.3), 308(sh), 320(sh), 374 (11.2)
258 (43.2), 282 (32.4), 312(sh), 322(sh), 375 (18.5)
482, 516
483, 515
483, 515
482, 515
483, 515
482, 522
482, 522
482, 522
482, 522
482, 531
482, 531
482, 531
0.006
0.005
0.007
0.009
0.010
0.010
0.010
0.011
0.012
0.007
0.022
0.063
out the possibility of the assignment to a purely d–d transition.
Such an assignment could be further support by the fact that the
position of the MLCT absorption band does not change when differ-
ent N-benzoyl thiourea derivatives are introducedin the molecule as
ancillary ligand.
compare to the second emission band. Moreover, the second emis-
sion band is red shifted and display a broad maximum at 522 nm
for complexes 7–10 and at 531 nm for complexes 11–13 when
compare to complexes 2–6 which exhibit this emission band at
515 nm.
All Pt(II) complexes show luminescence properties both in
dichloromethane solution and in solid state at room temperature.
The emission and excitation spectra in solution are presented in
Figs. 5 and 6 whilst in Fig. 7 two examples of solid-state emission
spectra are shown. The excitation spectra closely matched the
absorption spectra. There is a clear difference between the com-
plexes bearing N,N-dialkyl-N0-benzoyl thiourea derivatives, com-
plexes 2–6, and the complexes with N-aryl-N0-benzoyl thiourea
derivatives, 7–13, in terms of luminescence properties. All pre-
pared Pt(II) complexes show two emission bands in the 450–
550 nm range. The first one has the same position at 482 nm for
all complexes but its intensity in respect to the second one varies
for the two groups of complexes introduced above. For complexes
2–6 the intensity of this band is higher than the one located at
515 nm, whilst for complexes 7–13 this band has lower intensity
If we consider the highest energy feature of the luminescence
emission maxima, there is no significant difference in the position
of the emission maxima for complexes 2–13 compare to the Pt(II)
complexes containing cyclometallated phenylpyridine and differ-
ent ancillary ligands: acetylacetonate complexes exhibit emission
at kmax ꢃ485 nm in 2-methyltetrahydrofuran solution [9]; com-
plexes with phen or bpy [8] exhibit emission in DMF at kmax
ꢃ486 nm and complexes with bis(pyrazolyl)borates [12] as ancil-
lary ligands show the same features with kmax = 488 nm in CHCl3
solution. In fact for these complexes the emission maxima and
quantum yields are similar to those of the homoleptic cis-
[Pt(ppy)2] complexes that display structured ligand-centred
Fig. 5. Excitation and emission spectra of compound 2 in CH2Cl2 at 298 K with
Fig. 6. Excitation and emission spectra of compound 10 in CH2Cl2 at 298 K with
excitation at 375 nm and emission monitored at 482 nm.
excitation at 375 nm and emission monitored at 522 nm.

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V. Cîrcu et al. / Polyhedron 28 (2009) 3739–3746
ware package. The UV–Vis absorption spectra of Pt(II) complexes
2–13 were recorded in dichloromethane using a Cary 100 Bio (Var-
ian Inc.) spectrophotometer. Solid state fluorescence spectra were
recorded using a JASCO FP6500 spectrofluorimeter whilst fluores-
cence spectra in solution were recorded using a Perkin–Elmer LS
50B spectrofluorimeter with the following instrumental parame-
ters: excitation wavelengths 259, 282 and 375 nm, excitation slit
5 nm, emission slit 5 nm, scanning speed 200 nm/min and
290 nm cut-off filter except for the kexc = 375 nm. For each excita-
tion (emission) wavelength a spectrum of the solvent was also re-
corded in the same conditions. Absorption and emission spectra of
a 1 lM quinine sulfate solution in 0.5 M H2SO4 were used for the
determination of the fluorescence quantum yield of the com-
pounds. The quantum yield was computed according to the follow-
ing equation:
IuqstAst
IstquAu
Uu
¼
Ust
Fig. 7. Solid state emission spectra of complexes 2 and 12 (kexc = 380 nm).
where
U
is the quantum yield, I is the integrated area of the emis-
sion spectrum corrected for the solvent signal, q is the photon out-
put of the source at the excitation wavelength (the emission
intensity measured directly on the curve) and A is the absorbance
of the solutions at the excitation wavelengths, whereas indexes u
and st denote the unknown (new) compound and the quinine sul-
fate (standard) solutions [26]. The Pt precursor [Pt(Hppy)(ppy)(Cl)]
used in the preparation of the mononuclear complexes 2–13 was
prepared according to the literature data [9,19]. The N-benzoyl thio-
urea derivatives as well as their sodium salts used in this work were
prepared according to the methods published in the literature
[16,17].
phosphorescence at 450–550 nm [25]. The solid-state emission
spectra displayed in Fig. 7 show compounds 2 and 12 having kmax
at 521 and 514 nm, respectively. These two complexes also exhibit
some structure on the emission bands with high- and low-energy
shoulders at 488 and 552 nm and at 484 and 544 nm, respectively.
Also, complexes 2 and 12 exhibit a slightly red shift in the value of
kmax in going from solution to the solid state. The solid-state emis-
sion spectra are not significantly different from those recorded in
dichloromethane solution which suggests that there is a negligible
Pt–Pt interaction resulted from crystal packing as it is supported by
the X-ray analysis data.
4.1. Synthesis of complexes 2–13
3. Conclusions
The solid sodium salt of N,N-dialkyl-N0-benzoyl thiourea deriv-
ative (0.15 mmol) was added to a solution of the Pt precursor com-
plex (0.10 mmol) in CH2Cl2 (15 ml) and the resulting mixture was
stirred at room temperature for 1 day. The solvent was removed
and the solid was purified on silica using CH2Cl2 as eluant. The
crude yellow solid was recrystallised from a mixture of CH2Cl2/
C2H5OH (1/1) at ꢀ25 °C to give a bright yellow crystalline product.
The yields, elemental analysis results as well as 1H and selected
13C NMR and IR data are presented below:
A series of cyclometallated 2-phenylpyridine (ppy) Pt(II) com-
plexes bearing N-benzoyl thiourea derivatives as ancillary ligands
were prepared and characterised, and their absorption spectra
and luminescence properties were investigated. These complexes
were isolated as single isomers with the sulfur atom in trans posi-
tion versus the nitrogen atom of the ppy ligand as confirmed by X-
ray diffraction studies and NMR spectroscopy. The platinum(II)
complexes show good photoluminescence properties both in
dichloromethane solution and in solid state at room temperature
and their emission maxima are similar to other cyclometallated
2-phenylpyridine Pt(II) complexes with different ancillary ligands,
resulting in a very little influence of the type of N-benzoyl thiourea
derivatives employed.
Compound 2. Yield 83%, yellow crystals, m.p. 187 °C. Anal. Calc.
for C23H24N3OPtS: C, 47.2; H, 4.1; N, 7.2. Found: C, 46.9; H, 4.5; N,
7.0%.
1H NMR (300 MHz, CDCl3) d: 1.30, 1.44 (2t, 6H, J = 7.1 Hz, 2CH3);
3.88, 3.96 (q, 4H, J = 7.1 Hz, 2CH2N); 7.04–7.14 (m, 2H, H-40, H-50);
7.33 (ddd, 1H, J = 1.4, 5.0, 7.4 Hz, H-5); 7.40–7.46 (m, 2H, meta-Ph-
BTU); 7.49–7.60 (m, 3H, H-30, H-60, para-Ph-BTU); 7.74 (dt, 1H,
J = 0.8, 7.5 Hz, H-3); 7.88 (ddd, 1H, J = 1.6, 7.4, 7.5 Hz, H-4); 8.20–
8.23 (m, 2H, ortho-Ph-BTU); 9.29 (ddd, 1H, J = 0.8, 1.6, 5.0 Hz, H-6).
13C NMR (75 MHz, CDCl3) d: 169.3 (C@S), 165.8 (C@O), 145.2
(C-2, ppy), 138.3 (C-4, ppy), 132.9 (C-30, ppy), 131.2 (Ph-BTU),
129.9 (C-40, ppy), 129.4 (Ph-BTU), 128.4 (Ph-BTU), 123.9 (C-60,
ppy), 123.7 (C-50, ppy), 122.1 (C-5, ppy), 118.9 (C-3, ppy), 47.2,
46.1 (CH2), 13.5, 12.9 (CH3).
4. Experimental
Dichloromethane was distilled over phosphorus pentaoxide;
other chemicals were used as supplied. Melting points were mea-
sured using a Linkam THMS600 hot stage and a TMS94 tempera-
ture controller attached to a Nikon 50i Pol microscope. The FT-IR
spectra were recorded in the range 4000–400 cmꢀ1 using a BioRad
FTS-135 instrument. Proton and carbon NMR spectra were re-
corded on a Varian Gemini 300 BB spectrometer operating at
300 MHz, using CDCl3 as solvent. 1H chemical shifts were refer-
enced to the solvent peak position, d 7.26 ppm. X-ray data for crys-
tals 2 and 8 were collected at room temperature on a STOE IPDS II
diffractometer. The structure was solved by direct methods and re-
fined by full-matrix least squares techniques based on F2. The non-
H atoms were refined with anisotropic displacement parameters.
Calculations were performed using SHELX-97 crystallographic soft-
IR (KBr, cmꢀ1): (
1636m, 1608m, 1520s, 1483s, 1420vs, 745m.
mC–H), 2960w, 2930w, 2870w, (mC@N, mC@C),
Compound 3. Yield 82%, yellow crystals, m.p. 148 °C. Anal. Calc.
for C25H28N3OPtS: C, 48.9; H, 4.6; N, 6.8. Found: C, 48.5; H, 4.9; N,
6.5%.
1H NMR (300 MHz, CDCl3) d: 0.96, 1.05 (2t, 6H, J = 7.1 Hz, 2CH3);
1.70–2.00 (m, 4H, 2CH2); 3.75–3.86 (m, 4H, 2CH2N); 7.07–7.11 (m,
2H, H-40, H-50); 7.32 (ddd, 1H, J = 1.4, 5.0, 7.4 Hz, H-5); 7.40–7.45
(m, 2H, meta-Ph-BTU); 7.48–7.53 (m, 3H, H-30, H-60, para-Ph-BTU);

V. Cîrcu et al. / Polyhedron 28 (2009) 3739–3746
3745
7.75 (dt, 1H, J = 0.8, 7.5 Hz, H-3); 7.90 (ddd, 1H, J = 1.6, 7.4, 7.5 Hz,
H-4); 8.19–8.21 (m, 2H, ortho-Ph-BTU); 9.28 (ddd, 1H, J = 0.8, 1.6,
5.0 Hz, H-6).
1H NMR (300 MHz, CDCl3) d: 7.02–7.05 (m, 2H, H-40, H-50); 7.29
(ddd, 1H, J = 1.4, 6.0, 7.1 Hz, H-5); 7.33–7.56 (m, 12H, H-30, H-60,
8H-BTU); 7.71 (m, 1H, H-3); 7.86 (m, 1H, H-4); 8.15–8.17 (m, 2H,
ortho-Ph-BTU); 9.18 (dd, 1H, J = 0.8, 6.0 Hz, H-6).
13C NMR (75 MHz, CDCl3) d: 168.9 (C@S), 165.8 (C@O), 145.1
(C-2, ppy), 138.4 (C-4, ppy), 132.7 (C-30, ppy), 131.3 (Ph-BTU),
130.0 (C-40, ppy), 129.4 (Ph-BTU), 128.5 (Ph-BTU), 124.0 (C-60,
ppy), 123.7 (C-50, ppy), 122.2 (C-5, ppy), 119.0 (C-3, ppy), 54.8,
53.7, 21.6, 21.0 (CH2), 11.9 (CH3).
IR (KBr, cmꢀ1): (
1518s, 1501s, 1485s, 1427vs, 752m.
mN–H), 3054w, (mC@N, mC@C), 1636m, 1608m,
Compound 8. Yield 72%, yellow crystals, m.p. 228 °C dec. Anal.
Calc. for C26H21N3OPtS: C, 50.5; H, 3.4; N, 6.8. Found: C, 50.3; H,
3.7; N, 6.5%.
IR (KBr, cmꢀ1): (
1635m, 1606m, 1514s, 1482s, 1423vs, 746m.
mC–H), 2950w, 2930w, 2870w, (mC@N, mC@C),
1H NMR (300 MHz, CDCl3) d: 2.38 (s, 1H, p-CH3); 7.07–7.10 (m,
H-40, H-50); 7.21 (d, 2H, J = 8.6 Hz, 2H-BTU); 7.35 (ddd, 1H, J = 1.6,
6.0, 7.4 Hz, H-5); 7.41–7.58 (m, 7H, H-30, H-60, 5H-BTU); 7.75–
7.77 (m, 1H, H-3); 7.88–7.93 (m, 1H, H-4); 8.20–8.23 (m, 2H,
ortho-Ph-BTU); 9.23 (dd, 1H, J = 1.6, 6.0 Hz, H-6).
Compound 4. Yield 70%, yellow crystals, m.p. 143 °C. Anal. Calc.
for C27H32N3OPtS: C, 51.8; H, 5.2; N, 6.7. Found: C, 51.9; H, 5.5; N,
6.4%.
1H NMR (300 MHz, CDCl3) d: 0.98, 1.05 (2t, 6H, J = 7.3 Hz, 2CH3);
1.35–1.55 (m, 4H, 2CH2); 1.65–1.95 (m, 4H, 2CH2); 3.80–3.93 (m,
4H, 2CH2N); 7.10 (m, 2H, H-40, H-50); 7.32 (ddd, 1H, J = 1.4, 5.0,
7.4 Hz, H-5); 7.40–7.45 (m, 2H, meta-Ph-BTU); 7.48–7.53 (m, 3H,
H-30, H-60, para-Ph-BTU); 7.75 (dt, 1H, J = 0.8, 7.5 Hz, H-3); 7.90
(ddd, 1H, J = 1.6, 7.4, 7.5 Hz, H-4); 8.20–8.22 (m, 2H, ortho-Ph-
BTU); 9.29 (ddd, 1H, J = 0.8, 1.6, 5.0 Hz, H-6).
IR (KBr, cmꢀ1): (
1518s, 1485s, 1431vs, 754m.
mN–H), 3051w, (mC@N, mC@C), 1636m, 1608m,
9. Yield 83%, yellow crystals, m.p. 150 °C. Anal. Calc. for
C26H21N3OPtS: C, 50.5; H, 3.4; N, 6.8. Found: C, 50.2; H, 3.6; N, 6.5%.
1H NMR (300 MHz, CDCl3) d: 2.40 (s, 1H, m-CH3); 7.01–7.03 (m,
2H, H-40, H-50); 7.23–7.52 (m, 10H, H-5, H-30, H60, 7H-BTU); 7.69 -
7.71 (m, 1H, H-3); 7.82–7.88 (m, 1H, H-4); 8.15–8.18 (m, 2H, ortho-
Ph-BTU); 9.17 (dd, 1H, J = 1.6, 6.0 Hz, H-6).
13C NMR (75 MHz, CDCl3) d: 168.9 (C@S), 165.8 (C@O), 145.2
(C-2, ppy), 138.4 (C-4, ppy), 132.8 (C-30, ppy), 131.3 (Ph-BTU),
130.0 (C-40, ppy), 129.4 (Ph-BTU), 128.5 (Ph-BTU), 124.0 (C-60,
ppy), 123.7 (C-50, ppy), 122.2 (C-5, ppy), 119.0 (C-3, ppy), 52.8,
51.8, 30.4, 29.7, 20.7 (CH2), 14.3 (CH3).
IR (KBr, cmꢀ1): (
1512s, 1485s, 1431vs, 751m.
mN–H), 3047w, (mC@N, mC@C), 1636m, 1607m,
Compound 10. Yield 82%, yellow crystals, m.p. 229 °C dec. Anal.
Calc. for C25H18FN3OPtS: C, 48.2; H, 2.9; N, 6.7. Found: C, 47.9; H,
3.3; N, 6.4%.
IR (KBr, cmꢀ1): (
1634m, 1607m, 1518s, 1494s, 1484s, 1418vs, 745m.
mC–H), 2957m, 2930m, 2870w, (mC@N, mC@C),
Compound 5. Yield 80%, yellow crystals, m.p. 79 °C. Anal. Calc.
for C31H40N3OPtS: C, 53.4; H, 5.8; N, 6.0. Found: C, 53.1; H, 6.0;
N, 5.7%.
1H NMR (300 MHz, CDCl3) d: 7.00–7.08 (m, 4H, H-40, H-50, 2H-
BTU); 7.19–7.52 (m, 8H, H-5, H-30, H-60, 5H-BTU); 7.69–7.72 (m,
1H, H-3); 7.82–7.85 (m, 1H, H-4); 8.10–8.13 (m, 2H, ortho-Ph-
BTU); 9.16 (dd, 1H, J = 1.6, 6.0 Hz, H-6).
1H NMR (300 MHz, CDCl3) d: 0.86, 0.94 (2t, 6H, J = 7.1 Hz, 2CH3);
1.21–1.56 (m, 8H, 4CH2); 1.60–1.78 (m, 4H, 2CH2); 1.80–1.99 (m,
4H, 2CH2); 3.77–3.87 (m, 4H, 2CH2N); 7.06–7.11 (m, 2H, H-40, H-
50); 7.32 (ddd, 1H, J = 1.4, 5.0, 7.4 Hz, H-5); 7.41–7.46 (m, 2H,
meta-Ph-BTU); 7.49–7.52 (m, 3H, H-30, H-60, para-Ph-BTU); 7.73
(dt, 1H, J = 0.8, 7.5 Hz, H-3); 7.88 (ddd, 1H, J = 1.6, 7.4, 7.5 Hz, H-
4); 8.18–8.21 (m, 2H, ortho-Ph-BTU); 9.28 (ddd, 1H, J = 0.8, 1.6,
5.0 Hz, H-6).
IR (KBr, cmꢀ1): (
1522s, 1508s, 1485s, 1431vs, 755m.
mN–H), 3077w, (mC@N, mC@C), 1637m, 1607m,
Compound 11. Yield 85%, yellow crystals, m.p. 232 °C. Anal. Calc.
for C25H18ClN3OPtS: C, 47.0; H, 2.8; N, 6.6. Found: C, 46.8; H, 3.1; N,
6.4%.
1H NMR (300 MHz, CDCl3) d: 7.01–7.08 (m, 4H, H-40, H-50, 2H-
BTU); 7.29–7.54 (m, 8H, H-5, H-30, H-60, 5H-BTU); 7.70–7.72 (m,
1H, H-3); 7.83–7.89 (m, 1H, H-4); 8.11–8.14 (m, 2H, ortho-Ph-
BTU); 9.15 (dd, 1H, J = 1.6, 6.0 Hz, H-6).
13C NMR (75 MHz, CDCl3) d: 168.9 (C@S), 165.8 (C@O), 145.1
(C-2, ppy), 138.4 (C-4, ppy), 132.8 (C-30, ppy), 131.3 (Ph-BTU),
130.0 (C-40, ppy), 129.4 (Ph-BTU), 128.4 (Ph-BTU), 124.0 (C-60,
ppy), 123.7 (C-50, ppy), 122.2 (C-5, ppy), 119.0 (C-3, ppy), 52.8,
53.1, 52.1, 31.9, 28.2, 27.4, 27.2, 23.0 (CH2), 14.4 (CH3).
IR (KBr, cmꢀ1): (
1519s, 1485s, 1431vs, 754m.
mN–H), 3052w, (mC@N, mC@C), 1635m, 1607m,
Compound 12. Yield 80%, yellow crystals, m.p. 239 °C. Anal. Calc.
for C25H18BrN3OPtS: C, 43.9; H, 2.7; N, 6.1. Found: C, 43.7; H, 3.0; N,
5.9%.
IR (KBr, cmꢀ1): (
1606m, 1514s, 1482s, 1419vs, 747m.
mC–H), 2925m, 2857m, (mC@N, mC@C), 1635m,
Compound 6. Yield 75%, yellow crystals, m.p. 71 °C. Anal. Calc.
for C35H48N3OPtS: C, 55.8; H, 6.4; N, 5.6. Found: C, 55.5; H, 6.8;
N, 5.4%.
1H NMR (300 MHz, CDCl3) d: 7.08–7.11 (m, 4H, H-40, H-50, 2H-
BTU); 7.35–7.60 (m, 8H, H-5, H-30, H-60, 5H-BTU); 7.76–7.79 (m,
1H, H-3); 7.89–7.95 (m, 1H, H-4); 8.18–8.21 (m, 2H, ortho-Ph-
BTU); 9.22 (dd, 1H, J = 1.6, 6.0 Hz, H-6).
1H NMR (300 MHz, CDCl3) d: 0.86, 0.90 (2t, 6H, J = 7.1 Hz, 2CH3);
1.25–1.44 (m, 16H, 8CH2); 1.63–178 (m, 4H, 2CH2); 1.80–1.98 (m,
4H, 2CH2); 3.78–3.89 (m, 4H, 2CH2N); 7.08–7.11 (m, 2H, H-40,
H-50); 7.30 (ddd, 1H, J = 1.4, 5.0, 7.4 Hz, H-5); 7.40–7.45 (m, 2H,
meta-Ph-BTU); 7.49–7.54 (m, 3H, H-30, H-60, para-Ph-BTU); 7.75
(dt, 1H, J = 0.8, 7.5 Hz, H-3); 7.89 (ddd, 1H, J = 1.6, 7.4, 7.5 Hz, H-4);
8.20–8.22 (m, 2H, ortho-Ph-BTU); 9.29 (ddd, 1H, J = 0.8, 1.6, 5.0 Hz,
H-6).
IR (KBr, cmꢀ1): (
1517s, 1485s, 1431vs, 754m.
mN–H), 3053w, (mC@N, mC@C), 1635m, 1608m,
Compound 13. Yield 77%, yellow crystals, m.p. 220 °C. Anal. Calc.
for C26H21N3O2PtS: C, 49.2; H, 3.3; N, 6.6. Found: C, 48.9; H, 3.6; N,
6.4%.
1H NMR (300 MHz, CDCl3) d: 3.85 (s, 1H, OCH3); 6.94 (d, 2H,
J = 8.0 Hz, BTU); 7.05–7.07 (m, 2H, H-40, H-50); 7.21–7.57 (m, 6H,
H-5, H-30, H-60, 3H-BTU); 7.75–7.77 (m, 1H, H-3); 7.87–7.93 (m,
1H, H-4); 8.11–8.20 (m, 4H, BTU); 9.24 (dd, 1H, J = 1.6, 6.0 Hz, H-6).
13C NMR (75 MHz, CDCl3) d: 168.3 (C@O), 165.5 (C@S), 144.9
(C-2, ppy), 138.0 (C-4, ppy), 132.4 (C-30, ppy), 130.9 (Ph-BTU),
129.6 (C-40, ppy), 129.1 (Ph-BTU), 128.1 (Ph-BTU), 123.6 (C-60,
ppy), 123.4 (C-50, ppy), 121.8 (C-5, ppy), 118.6 (C-3, ppy), 52.8,
51.7, 31.8, 29.3, 27.9, 27.2, 22.6 (CH2), 14.1 (CH3).
IR (KBr, cmꢀ1): (
mN–H), 3044w, (mC@N, mC@C), 1636m, 1607m,
1509s, 1484s, 1435vs, 751m.
IR (KBr, cmꢀ1): (
1636m, 1607m, 1517s, 1497s, 1483s, 1420vs, 742m.
mC–H), 2950m, 2925m, 2870m, (mC@N, mC@C),
Acknowledgements
Compound 7. Yield 77%, yellow crystals, m.p. 220 °C. Anal. Calc.
for C25H19N3OPtS: C, 49.7; H, 3.2; N, 7.0. Found: C, 49.5; H, 3.6; N,
6.8%.
The authors wish to thank MECI (Romanian Ministry of Educa-
tion and Innovation, Project PNII ID_954) for funding this study

3746
V. Cîrcu et al. / Polyhedron 28 (2009) 3739–3746
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(b) P.I. Kvam, M.V. Puzyk, K.P. Balashev, J. Songstad, Acta Chem. Scand. 49
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and to Dr. Augustin Madalan for his help with the X-ray diffraction
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Appendix A. Supplementary data
CCDC 740820 and 740821 contain the supplementary crystallo-
graphic data for 2 and 8. These data can be obtained free of charge
via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Road, Cam-
bridge CB2 1EZ, UK; fax: (+44) 1223 336 033; or e-mail: depos-
it@ccdc.cam.ac.uk. Supplementary data associated with this
article can be found, in the online version, at doi:10.1016/
j.poly.2009.08.015.
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