Syntheses and luminescent properties of 3,5-diphenylpyrazolato-bridged heteropolynuclear platinum complexes. the influence of chloride ligands on the emission energy revealed by the systematic replacement of chloride ligands by 3,5-dimethylpyrazolate

Article abstract of DOI:10.1021/ic202663q

Heteropolynuclear Pt^II complexes with 3,5-diphenylpyrazolate [Pt₂Ag₄(μ-Cl)₂(μ-Ph₂pz) ₆] (3), [Pt₂Ag₂Cl₂(μ-Ph ₂pz)₄(Ph₂pzH)<

Full text of DOI:10.1021/ic202663q

Article
pubs.acs.org/IC
Syntheses and Luminescent Properties of 3,5-Diphenylpyrazolato-
Bridged Heteropolynuclear Platinum Complexes. The Influence of
Chloride Ligands on the Emission Energy Revealed by the Systematic
Replacement of Chloride Ligands by 3,5-Dimethylpyrazolate
Seiji Akatsu,† Yasunori Kanematsu,† Taka-aki Kurihara,† Shota Sueyoshi,† Yasuhiro Arikawa,†
Masayoshi Onishi,† Shoji Ishizaka,‡ Noboru Kitamura,§ Yoshihide Nakao,¶,⊥ Shigeyoshi Sakaki,¶
and Keisuke Umakoshi*,†
†Division of Chemistry and Materials Science, Graduate School of Engineering, Nagasaki University, Bunkyo-machi, Nagasaki
852-8521, Japan
‡Department of Chemistry, Graduate School of Science, Hiroshima University, Kagamiyama, Higashi-Hiroshima, 739-8526, Japan
§Division of Chemistry, Graduate School of Science, Hokkaido University, Kita-ku, Sapporo 060-0810, Japan
¶Fukui Institute for Fundamental Chemistry, Kyoto University, Takano-Nishihiraki-cho, Sakyou-ku, Kyoto 606-8103, Japan
⊥Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Kyoto-Daigaku-Katsura, Nishikyou-ku,
Kyoto 615-8510, Japan
S
* Supporting Information
ABSTRACT: Heteropolynuclear PtII complexes with 3,5-
diphenylpyrazolate [Pt2Ag4(μ-Cl)2(μ-Ph2pz)6] (3),
[Pt2Ag2Cl2(μ-Ph2pz)4(Ph2pzH)2] (4), [Pt2Cu2Cl2(μ-
Ph2pz)4(Ph2pzH)2] (5), [Pt2Ag4(μ-Cl)(μ-Me2pz)(μ-Ph2pz)6]
(7), and [Pt2Ag4(μ-Me2pz)2(μ-Ph2pz)6] (8) have been
prepared and structurally characterized. These complexes are
luminescent except for 5 in the solid state at an ambient
temperature with emissions of red-orange (3), orange (4),
yellow-orange (7), and green (8) light, respectively. Systematic
red shift of the emission energies with the number of chloride
ligands was observed for 3, 7, and 8. DFT calculations indicate
that the highest occupied molecular orbital (HOMO) as well as
HOMO-1 of the heterohexanuclear complexes, 3, 7, and 8,
having Pt2Ag4 core, mainly consist of dδ orbital of PtII and π
orbitals of Ph2pz ligands, while the lowest unoccupied molecular orbital (LUMO) of these complexes mainly consists of in-phase
combination of 6p of two PtII centers and 5p of four AgI centers. It is likely that the emissions of 3, 7, and 8 are attributed to
emissive states derived from the Pt2(d)/π → Pt2Ag4 transitions, the emission energy of which depends on the ratio of chloride
ligands to pyrazolate ligands.
brightly luminescent heterohexanuclear PtII complexes
INTRODUCTION
Heteropolynuclear transition-metal complexes have been
■
[Pt2M4(μ-Me2pz)8] (MI = AgI, CuI) by using only 3,5-
dimethylpyrazolate as bridging ligands instead of alkynyl
ligands.26 Furthermore, we have succeeded in the preparation
of heterohexanuclear PtII complexes [Pt2Au2M2(μ-Me2pz)8]
(MI = AgI, CuI) and achieved the fine-tuning of the emission
energy by incorporating the third transition metal element such
as AgI and CuI.27 These heterohexanuclear PtII complexes
exhibit colorful luminescence. Large difference of emission
energy was observed depending on the nature of the coinage
metal ions (Cu, Ag, or Au) among these complexes. The low
attracting much attention because they are expected to exhibit
characteristic interactions and cooperative effects between the
transition elements and provide novel functions that cannot be
obtainable by one kind transition metal element. The syntheses
of heterohexanuclear PtII complexes [Pt2M4(CCR)8] (MI =
CuI, AgI, AuI; R = t-butyl, phenyl)1 have prompted studies on
the photophysical properties of these mixed-metal complexes
containing group 11 metal ions2−11 and related complexes
containing main group metal ions (CdII, TlI, PbII),10−18 as well
as lanthanide ions.19−25 Heterohexanuclear PtII complexes
stabilized by both of alkynyl and 3,5-dimethylpyrazolate
(Me2pz) have also been prepared.6 We have also prepared
Received: December 10, 2011
© XXXX American Chemical Society
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Figure 1. Schematic representation of Pt2Ag4 and Pt2Ag2 complexes with photographs showing their luminescence in the solid state upon exposure
to UV radiation at an ambient temperature.
energy emission was assigned to a metal−ligand-to-metal
charge transfer (3MLM′CT) transition (Pt(d)π(CCR) →
Pt(pz)/M′(sp)/π*(CCR)) modified by Pt···M′ and M′···M′
contact for [Pt2M4(CCR)8].5−7 Similarly the low energy
emissions of dimethylpyrazolato-bridged complexes [Pt2M4(μ-
Me2pz)8] were assigned to the transition from the in-phase
combination of 6p(Pt) and 5p(Ag) to the dδ(Pt) nonbonding
orbitals (3[Pt2 → Pt2Ag4]) for M = Ag and the transition from
the in-phase combination of 6p(Pt) and 4p(Cu) orbitals to a
dπ(Cu) orbital localized on one of the four Cu ions (3[Cu(d)
→ Pt2Cu4]) for M = Cu, respectively, reflecting the difference
in d orbital energies of Pt, Ag, and Cu.26 These assignments
indicate that the emissions of [Pt2M4(CCR)8] and
[Pt2M4(μ-Me2pz)8] occur from the excited state containing
one-electron transition from Pt(d) (or Cu(d)) orbital to the in-
phase combination among coinage metal ions and PtII ions.
The Pt2Ag4 complexes with 3,5-dialkylpyrazolates (R2pz),
[Pt2Ag4(μ-R2pz)8], exhibit sky-blue to green emission.26 The
use of 3,5-diphenylpyrazole (Ph2pzH) as a bridging ligand
instead of alkylpyrazoles, on the other hand, afforded
[Pt2Ag4(μ-Cl)2(μ-Ph2pz)6] (3) containing two μ-chloro ligands
in the complex molecule. It is very interesting that 3 exhibits
red-orange luminescence in the solid state upon exposure to
UV radiation in spite of the presence of octahedral Pt2Ag4 core
unlike [Pt2Ag4(μ-R2pz)8] (Figure 1). To the best of our
knowledge, however, very little is discussed about the
dependence of the emission energy on the molecular structure
of Pt2M4 core. It is thus of considerable interest to elucidate the
origin of such large difference of emission energies between
[Pt2Ag4(μ-Me2pz)8] and 3. Furthermore we have also
succeeded in the replacement of chloride ligand in chlorotris-
(3,5-diphenylpyrazole) complex with 3,5-dimethylpyrazole,
which leads to the synthesis of chloride-free Pt2Ag4 complex
bridged by Ph2pz and Me2pz. Thus, one can expect that the
complexes bearing Pt2Ag4 core provide new findings about the
relation between the molecular structure of the Pt2Ag4 core and
the emission spectra.
are to clarify the dependence of emission energy on the
molecular structure and to elucidate the reasons.
RESULTS AND DISCUSSION
■
Preparation of Complexes. It is known that the pKa value
of the conjugate acid of 3,5-dimethylpyrazole (Me2pzH; 4.06)
is higher than that of nonsubstituted pyrazole (pzH; 2.83) as
shown in Figure 2.28 On the contrary, the corresponding value
Figure 2. pKa values of conjugate acid of pyrazole, 3,5-dimethylpyr-
azole, and 3,5-diphenylpyrazole.
of Ph2pzH (1.85) is smaller than that of pzH, indicating that
the coordination ability of Ph2pzH is weaker than those of
Me2pzH and pzH. Actually the reactions of PtII starting
material, [PtCl2(C2H5CN)2], with Me2pzH and pzH afford
tetrakis(pyrazole derivative) complexes, [Pt(Me2pzH)4]Cl2 and
[Pt(pzH)4]Cl2, respectively. However, as mentioned below, the
reaction with Ph2pzH affords chlorotris(3,5-diphenylpyrazole)
complex, [PtCl(Ph2pzH)3]Cl (1), which contains an unsub-
stituted chloride ligand in the complex cation (Scheme 1). The
effect of the basicity of pyrazole derivatives on the geometrical
structure and reactivity of product has not been fully
understood. We have now found the geometrical preference
of mononuclear PtII complexes of pyrazole derivatives, which
gives the guideline for the synthesis of tetrakis(pyrazole
derivative) complexes and chlorotris(pyrazole derivative)
complex.
In this paper, we wish to report the syntheses, structures, and
photophysical properties of dichloro-, monochloro-, and
chloride-free Pt2Ag4 complexes of 3,5-diphenylpyrazolate, as
well as their precursor mononuclear PtII complexes, and
dichloro-Pt2Ag2 and Pt2Cu2 complexes. Our purposes here
The reaction of [PtCl2(C2H5CN)2] with 3,5-diphenylpyr-
azole (Ph2pzH) afforded a cationic mononuclear platinum
complex, [PtCl(Ph2pzH)3]Cl (1), in which a chloride ligand
and three neutral Ph2pzH ligands coordinate to the PtII ion in a
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is noteworthy here that the three-component reaction of
isolated 2, isolated 6, and AgBF4 gave 7 in much better yield.
Since it was found that the reaction of cationic complex 1
with Me2pzH even in the presence of Et3N does not give a
chloride-free mononuclear complex as a major product, next we
attempted to replace the chloride ligand with Me2pzH by using
neutral complex 2. Fortunately the reaction of 2 with potassium
salt of 3,5-dimethylpyrazole (K[Me2pz]) afforded a neutral
chloride-free complex 6 as expected. Finally the reaction of 6
with AgI ion gave a chloride-free Pt2Ag4 complex, [Pt2Ag4(μ-
Me2pz)2(μ-Ph2pz)6] (8), which exhibits green emission in the
solid state (Figure 1). Thus it can be concluded from the
preparation of monochloro and chloride-free Pt2Ag4 complexes
that the lower energy shift of the emission spectrum (vide
infra) in 3 mainly originates from the coordination of chloride
ligands to Pt atoms.
Scheme 1. Geometrical Preference of Mononuclear Platinum
Complexes
Crystal Structures. X-ray structural analyses of 2·CH3OH,
3·3CH2Cl2, 4·2CH3CN, 5·CH3CN, 7·0.5CH3OH·0.5H2O, and
8 were performed. Although cluster complexes 3, 4, 5, and 7
crystallized with solvent molecules, any contacts between
cluster complexes with solvent molecules were not found in
their crystal structures (Supporting Information Figures S14−
S17).
The neutral mononuclear platinum complex with 3,5-
diphenylpyrazole, [PtCl(Ph2pz)(Ph2pzH)2] (2), which is the
precursor of 3, 4, 5, 6, and 7, crystallized with a methanol
molecule as a solvent of crystallization. The molecular structure
of 2 is shown in Figure 3. The complex 2 has a structure in
which a chloride ion, a Ph2pz anion and two neutral Ph2pzH
ligands coordinate to the PtII center. One of the two Ph2pzH
ligands forms intramolecular hydrogen bonding (N12−
H12···N22) together with the Ph2pz ligand (Supporting
Information Table S1). The other Ph2pzH ligand also forms
hydrogen bonding (N32−H32···O1) with methanol molecule.
These two hydrogen atoms participating in the hydrogen
bonding were found from the Fourier map and refined
isotropically in the structural analysis.
monodentate fashion, probably due to weaker basicity of
Ph2pzH (Scheme 2). A treatment of 1 with strong base brought
about liberation of a proton from one of the three Ph2pzH
ligands as well as loss of an outer sphere chloride ligand to give
a neutral mononuclear complex [PtCl(Ph2pz)(Ph2pzH)2] (2),
which is stabilized by an intramolecular hydrogen bonding.
This is different from the formation of dimer complex
[{Pt(Me2pz)2(Me2pzH)2}2] stabilized by intermolecular hydro-
gen bonding, upon treatment of a cationic mononuclear
complex [Pt(Me2pzH)4]Cl2 with base.26 The preference of the
formation of mononuclear complex and dimer complex seems
to be associated with the bulkiness of substituent groups on the
pyrazoles. The reaction of the neutral mononuclear complex
with AgI ion afforded a di(μ-chloro) complex, [Pt2Ag4(μ-
Cl)2(μ-Ph2pz)6] (3), which consists of two PtII ions, four AgI
ions, two chloride ligands, and six Ph2pz ligands. The complex 3
exhibits red-orange emission in the solid state upon exposure to
UV radiation at an ambient temperature.
It also became obvious that 3 can be prepared in a stepwise
manner via [Pt2Ag2Cl2(μ-Ph2pz)4(Ph2pzH)2] (4), which
exhibits orange emission in the solid state. Although the
Pt2Ag2Cl2 complex 4 was obtained even by the reaction of
neutral mononuclear complex 2 with an excess amount of
AgBF4 in the absence of Et3N, the reaction of 2 with AgBF4 in a
1:1 ratio gave 4 and that in a 1:2 ratio gave 3, respectively, in
the presence of Et3N in good yield. Furthermore, similarly to
the reaction of 2 with AgI ion, that with CuI ion also gave
corresponding Pt2Cu2Cl2 complex, [Pt2Cu2Cl2(μ-
Ph2pz)4(Ph2pzH)2] (5).
In order to elucidate, from the viewpoint of synthetic
chemistry, whether the main factor of lower energy emission
(red-orange emission) of 3 is the coordination of chloride
ligand to Pt atom or not, we have also conducted the
replacement of chloride ligands in 3 with Me2pz, which can be
regarded as a stronger base than Ph2pz (Figure 2). The chloride
ligand in the neutral complex 2, as well as cationic complex 1,
could not be replaced by Ph2pz anion. However the reaction of
1 with Me2pzH in the presence of Et3N partially proceeded to
give an intermediate species, which is mainly consisting of
[Pt(Ph2pz)2(Me2pzH)(Ph2pzH)] (6, vide infra) and 2 (see
Supporting Information). Further reaction of the intermediate
species with AgBF4 afforded a (μ-chloro)(μ-dimethylpyrazola-
to) complex, [Pt2Ag4(μ-Cl)(μ-Me2pz)(μ-Ph2pz)6] (7), which
exhibits yellow-orange emission in the solid state (Figure 1). It
The di(μ-chloro) complex, [Pt2Ag4(μ-Cl)2(μ-Ph2pz)6] (3),
crystallizes with three dichloromethane molecules, and the
molecular structure of 3 is shown in Figure 4. The complex
molecule is formed by liberation of four protons in total from
two molecules of 2 and incorporation of four AgI ions into the
molecule. A chloride ion and three Ph2pz anions coordinate to
each PtII center to form {PtCl(Ph2pz)3} unit, and four AgI ions
are sandwiched by the two {PtCl(Ph2pz)3} units, each AgI ion
being located between two Ph2pz ligands and between chloride
ligand and Ph2pz ligand. The chloride ligands act as bridging
ligands in 3, and the Pt2Ag4 core can be regarded as a distorted
octahedron similarly to [Pt2Ag4(μ-Me2pz)8].26 The complex
molecule has an idealized 2-fold axis passing through Ag3 and
Ag4. The Pt···Pt distance in 3 is 5.0276(8) Å (Supporting
Information Table S2). The Pt···Ag distances are ranging from
3.0069(9) to 3.5337(8) Å, and the proximate Ag···Ag distances
are ranging from 2.9647(13) to 3.3367(13) Å. The Pt−Cl
distances (2.337(3) and 2.3379(19) Å) in 3 are ca. 0.04 Å
longer than those in the precursor complex 2 (2.299(2) Å),
|{[(PPh3)(C6F5)Pt(μ-Cl)]2Ag}(μ-Cl)2Ag(MeOH)|n (9)
(2.295(4), 2.308(3) Å),29 and [(Me)(N−N)Pt(μ-Cl)Ag(μ-
Cl)Pt(N−N)(Me)]BF4 (N−N = ArNC(Me)C(Me)NAr,
Ar = 2,6-(iPr)2C6H3) (10) (2.291(1), 2.298(1) Å).30 The Ag−
Cl distances (2.486(3) and 2.518(3) Å) in 3 fall into the range
of Ag−Cl distances found in 9 (2.225(5), 2.400(6), 2.551(3)
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Scheme 2. Preparative Methods for 3, 7, and 8
Å)29 and in 10 (2.398(1), 2.471(1) Å).30 The Ag−Cl distance
seems to be readily changed by alterations in Pt−Cl−Ag angle.
[Pt2Ag2Cl2(μ-Ph2pz)4(Ph2pzH)2] (4) crystallizes with two
acetonitrile molecules, and the molecular structure of 4 is
shown in Figure 5. The complex molecule is formed by
liberation of two protons in total from two molecules of 2 and
incorporation of two AgI ions into the molecule. A chloride ion,
two Ph2pz anions and a neutral Ph2pzH molecule coordinate to
each PtII center, and each AgI ion is located between the two
Ph2pz ligands. The complex molecule has a crystallographically
imposed 2-fold axis passing through the midpoint of Pt1···Pt1*
and the midpoint of Ag1···Ag1*, and half of the atoms in the
molecule are independent. The Pt···Pt distance in 4 is
4.2846(3) Å, which is ∼0.75 Å shorter than that in 3
(Supporting Information Table S3). The Pt···Ag distances
(3.2156(5) and 3.4554(4) Å) and the Ag···Ag distance
(3.1111(6) Å) in 4 are comparable to those in 3, respectively.
The Pt−Cl distance in 4 (2.3303(12) Å) is also comparable to
that in 3.31
The copper analogue, [Pt2Cu2Cl2(μ-Ph2pz)4(Ph2pzH)2] (5)
also crystallizes with two acetonitrile molecules, and its crystal
structure is isomorphous to that of 4·2CH3CN. The molecular
structure of 5 is shown in Figure 6. Similarly to 4, the complex
molecule of 5 is formed by liberation of two protons in total
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Figure 3. Molecular structure of 2 with the atom numbering scheme (50% probability ellipsoids).
from two molecules of 2 and incorporation of two CuI ions into
the molecule. A chloride ion, two Ph2pz anions and a neutral
Ph2pzH molecule coordinate to each PtII center, and each CuI
ion is located between the two Ph2pz ligands. The complex
molecule also has a crystallographically imposed 2-fold axis
passing through the midpoint of Pt1···Pt1* and the midpoint of
Cu1···Cu1*, and half of the atoms in the molecule are
independent. The Pt···Pt distance in 5 is 3.9614(3) Å, which is
ca. 0.3 Å shorter than that in 4 due to the smaller ionic radius of
CuI than that of AgI (Supporting Information Table S4).
Nevertheless the Pt···Cu distances (3.3458(7) and 3.2127(7)
Å) and the Cu···Cu distance (3.1465(10) Å) in 5 are not so
much different from the Pt···Ag distances and Ag···Ag distance
in 4, respectively.
Pt···Pt distances between two independent molecules in 7 may
be attributed to a difference of packing effect. The Pt···Ag
distances are ranging from 3.0925(11) to 3.5798(13) Å, and the
proximate Ag···Ag distances are ranging from 2.9527(14) to
3.2964(15) Å. The Pt−Cl distances (2.329(4) and 2.346(4) Å)
in 7 are comparable to those in 3 and 4. The Ag−Cl distances
(2.454(4) and 2.452(3) Å) and Pt−Cl−Ag angles (80.58(11)
and 80.24(10)°) are also very similar to those in 3 (2.486(3)
and 2.518(3) Å, and 80.82(8) and 76.43(6)°), respectively.
The molecular structure of bis(dimethylpyrazolato) complex
[Pt2Ag4(μ-Me2pz)2(Ph2pz)6] (8) is shown in Figure 8. The
complex 8 consists of two Pt atoms, four Ag atoms, two Me2pz
anions, and six Ph2pz anions. Each Pt atom is coordinated by a
Me2pz anion and three Ph2pz anions. Similarly to 3 and 7, the
two Pt units, {Pt(Me2pz)(Ph2pz)3}, sandwiches four AgI ions to
form Pt2Ag4 distorted octahedron, each AgI ion being located
between two Ph2pz ligands and between two Me2pz ligands. It
is noteworthy here that no AgI ion is located between Ph2pz
ligand and Me2pz in this major isomer. Nevertheless the
complex molecule also has an idealized 2-fold axis passing
through Ag1 and Ag3. The Pt···Pt distance in 8 is 5.1001(9) Å
(Supporting Information Table S6), which is comparable to
those in 3 and 7. The Pt···Ag distances are ranging from
3.3460(15) to 3.5822(14) Å, and the proximate Ag···Ag
distances are ranging from 3.159(2) to 3.3514(18) Å. Those
are also very similar to those in 3 and 7.
The monochloromono(dimethylpyrazolato) complex,
[Pt2Ag4(μ-Cl)(μ-Me2pz)(Ph2pz)6] (7), crystallized in triclinic
P1. Because the asymmetric unit of 7 consists of two
̅
crystallographically independent molecules, one of them is
illustrated in Figure 7. The complex 7 consists of two Pt atoms,
four Ag atoms, a chloride ion, a Me2pz anion, and six Ph2pz
anions. In a molecule, a chloride ion and three Ph2pz anions
coordinate to one of the two Pt atoms, and the other Pt atom is
coordinated by a Me2pz anion and three Ph2pz anions. These
two Pt units, {PtCl(Ph2pz)3} and {Pt(Me2pz)(Ph2pz)3},
sandwiches four AgI ions to form Pt2Ag4 distorted octahedron,
each AgI ion being located between two Ph2pz ligands, between
chloride ligand and Ph2pz ligand, and between Me2pz ligand
and Ph2pz ligand. The overall structure of 7 is similar to that of
dichloro complex 3, though one of the chloride ligands is
replaced by Me2pz ligand. The Pt···Pt distances in 7 are
5.2345(7) and 5.1066(6) Å (Supporting Information Table
S5), which are comparable to those in 3 (5.0276(8) Å) and
[Pt2Ag4(μ-Me2pz)8] (5.1578(8) Å).26 The large difference of
Absorption and Emission Spectroscopy. The colorless
mononuclear PtII complexes with Ph2pz and/or Ph2pzH
ligands, 1, 2, and 6 exhibit absorption bands in the UV region
shorter than 350 nm. On the contrary, the pale yellow
heteropolynuclear complexes having chloride ligands exhibit
weak absorption band tail in the range of 350−400 nm. The
UV/vis absorption spectra of 2, 3, 6, and 8 are shown in Figure
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Figure 4. Molecular structure of 3 with the atom numbering scheme (30% probability ellipsoids) and metal−metal distances (Å) in 3. The arrow
indicates direction of idealized 2-fold axis.
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Figure 5. Molecular structure of 4 with the atom numbering scheme (50% probability ellipsoids) and metal−metal distances (Å) in 4.
9; we omitted the spectra of 4 and 7 since the absorption
spectra of heterohexanuclear PtII complexes 3, 4, and 7
resemble to each other (Supporting Information Figure S10).
The photophysical data for 2-8 are summarized in Table 1.
Both of these mononuclear PtII complexes and heteropolynu-
clear PtII complexes exhibit absorption bands arising from
π−π* transition of Ph2pz/Ph2pzH at around 250 nm.
The mononuclear PtII complexes 1 and 2, with a chloride
ligand and Ph2pzH or Ph2pz do not exhibit emission in the
solid state as well as in solution at an ambient temperature,
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Figure 6. Molecular structure of 5 with the atom numbering scheme (50% probability ellipsoids) and metal−metal distances (Å) in 5.
while the neutral chloride-free complex 6 exhibits weak green
emission in the solid state (Supporting Information Figure
S16). The reaction of 2 with AgI ion in a different Pt/Ag ratio
afforded the Pt2Ag4Cl2 complex 3 and the Pt2Ag2Cl2 complex 4,
which exhibit red-orange emission (λmax = 683 nm) and orange
emission (λmax = 626 nm), respectively, in the solid state at an
ambient temperature (Figure 10). The Pt2Ag4Cl(Me2pz)
complex 7, obtained by two synthetic methods (Scheme 2),
exhibits yellow-orange emission (λmax = 599 nm) in the solid
state (Figure 10). Although the dichloro complexes 3 and 4
also exhibit weak emission in CH2Cl2 solution at an ambient
temperature, the emission spectra of these complexes are
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Figure 7. Molecular structure of 7 with the atom numbering scheme (30% probability ellipsoids) and metal−metal distances (Å) in 7.
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Figure 8. Molecular structure of 8 with the atom numbering scheme (30% probability ellipsoids) and metal−metal distances (Å) in 8.
dependent on the excitation wavelength and slightly change
with time. These characteristics are in contrast with those of
Me2pz-bridged Pt2Ag4 complex, [Pt2Ag4(μ-Me2pz)8],26 the
emission spectrum of which does not show the dependence
on the excitation wavelength and does not change with time
under irradiation of UV light in solution. The photophysical
data for 3, 4, and 7 are listed in Table 1. The observed lifetimes
of the emission for these complexes in the microsecond regime
indicate that the emissions are phosphorescence. The solid
state quantum yields of 3 (Φem = 0.07) and 7 (Φem = 0.16) are
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The chloride-free Pt2Ag4 complex bridged by Ph2pz and
Me2pz, 8, was found to exhibit green emission (λmax = 515 nm)
in the solid state at an ambient temperature (Figure 10). The
solid-state quantum yield of 8 (Φem = 0.16) was moderate
(Table 1). It should be emphasized that these photophysical
data provided the answer for our original question why Pt2Ag4
complexes of 3,5-diphenylpyrazolate having chloride ligands
exhibit orange to red-orange emission in spite of the sky-blue to
green emission of the Pt2Ag4 complexes with 3,5-dialkylpyr-
azolates (R2pz), [Pt2Ag4(μ-R2pz)8].26 Now it is obvious that
the low energy shift of the emission spectra was induced by the
coordination of chloride ligands to the PtII centers. Very
interestingly, systematic red shift of the emission energies with
increase of chloride/pyrazolate ratio was observed for 3, 7, and
8 (Figure 10). It indicates that the coordination of a chloride
ligand to one of the two PtII centers affects the whole orbital
energies of 7. The HOMOs as well as HOMO-1s of 3, 7, and 8
mainly consist of dδ orbitals of PtII centers and π orbitals of
Ph2pz ligands (vide infra). The LUMO of 8 mainly consists of
in-phase combination of 6p of two PtII centers and 5p of four
AgI centers, and those of 3 and 7 also mainly consist of similar
pσ orbitals stabilized by the coordination of chlorido ligands to
PtII centers. Therefore, it is likely that the emissions of 3, 7, and
8 are attributed to emissive states derived from the Pt2(d)/π →
Pt2Ag4 transitions, the emission energy of which depends on
the ratio of chloride ligands to pyrazolate ligands.
Figure 9. Electronic absorption spectra of 2 (black), 3 (red), 6
(green), and 8 (blue) in CH2Cl2 at 298 K.
Table 1. Photophysical Data for 2−8
a
absorption λmax [nm]
(εmax [dm3
b
c
complex
mol−1cm−1])
emission λmax [nm] (τ [μs])
Φem
2
3
253 (54300), 300 sh
250 (138000), 290 sh, 683 (τ1 = 0.33 (A1 = 0.73), τ2 = 0.07
330 sh
d
2.81 (A2 = 0.27))
4
5
6
7
253 (124000), 335 sh 626 (6.34)
255 (110000), 320 sh
0.41
Although the shift of emission energies has been reported by
the replacement of a chloride ligand in the PtII complex with an
iodide ion,32 the stepwise replacement of chloride ligands in the
complex molecule with other ligands has not been studied
probably due to the difficulty in the control of substitution
reaction for the mononuclear PtII complex. The heterohex-
anuclear PtII complexes, 3, 7, and 8, demonstrated for the first
time that the emission energies of the Pt2Ag4 complexes could
be shifted systematically by changing the ratio of coordinated
chloride ligands to pyrazolate ligands.
258 (64200), 285 sh
529
251 (136000), 290 sh, 599 (τ1 = 1.41 (A1 = 0.41), τ2 = 0.16
d
320 sh
9.00 (A2 = 0.59))
8
250 (121000), 290 sh, 515 (τ1 = 1.02 (A = 0.92), τ2 = 0.13
1 d
a
320 sh
2.37 (A2 = 0.08)) 522 (0.72)
a
b
c
In dichloromethane at 298 K. In the solid state at 298 K. Emission
d
quantum yield in the solid state. Emission decay curve was analyzed
by the equation (I(t) = A1 exp(-t/τ1) + A2 exp(−t/τ2)) using the
nonlinear least-squares method.
Computational Study. To provide better understanding of
the origin of the low-energy absorption bands of the
heterohexanuclear PtII complexes, DFT calculations were
performed on the ground states of 3−5, 7, and 8. The selected
molecular orbitals near frontier orbitals are depicted in Figure
11. The highest occupied molecular orbitals (HOMOs) as well
as HOMO-1s of the heterohexanuclear complexes, 3, 7, and 8,
having Pt2Ag4 core, mainly consist of dδ orbital of PtII and π
orbitals of Ph2pz ligands. Their lowest unoccupied molecular
orbitals (LUMOs) mainly consist of in-phase combination of
6p of two PtII centers and 5p of four AgI centers. The LUMOs
of 3, 7, and 8 resemble well those of [Pt2M4(μ-Me2pz)8] (M =
Ag, Cu)26 and [Pt2Au2M2(μ-Me2pz)8] (M = Ag, Cu),27 and the
absorption bands of [Pt2M4(μ-Me2pz)8] and [Pt2Au2M2(μ-
Me2pz)8] are assigned to [Pt2 → Pt2M4] and [Pt2 → Pt2Au2M2]
transitions, respectively. Theoretical calculations by the time-
dependent density functional theory (TD-DFT) for 3, 7, and 8
revealed that the excitations with large oscillator strength were
assigned to be π → π* excitation in Ph2pz ligands but the
lowest excited state, which is assigned to be HOMO and/or
HOMO-1 to LUMO excitation, exhibits small oscillator
strength; see Supporting Information Figures S19−S24. The
lowest energy absorption bands are assigned to [Pt2(d)/π→
Pt2Ag4] transition for 3, 7, and 8. Careful examination of the
DFT computational results further revealed that the 3p orbitals
of Cl atoms interact with 6p orbitals of PtII centers and 5p
orbitals of AgI centers in the same phase. It is obviously shown
Figure 10. Normalized emission spectra of 3 (νmax = 14600 cm−1 (683
nm)), 4 (νmax = 16000 cm−1 (626 nm)), 7 (νmax = 16700 cm−1 (599
nm)), and 8 (νmax = 19200 cm−1 (515 nm)) in the solid state at 295 K
(λex = 355 nm).
moderate, while that of 4 (Φem = 0.41) is found to be very high
at an ambient temperature. However, the emission of
Pt2Cu2Cl2 complex 5 was not observed in the range of 300−
950 nm. Because the LUMO of 5, similarly to 4, mainly consists
of π* orbitals of monodentate Ph2pzH ligands and the energy
level of HOMO of 5 (Cu(d)) is higher than that of 4 (Pt(5d)),
it is expected that the emission energy of 5 is lower than that of
4 (vide infra). The reason why the emission of 5 was not
observed is unclear at this stage.
K
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Figure 11. Spatial plot (isovalue = 0.02) of selected molecular orbitals of the singlet state for 3, 4, 7, and 8 by the B3LYP method.
a
Table 2. Orbital Composition Percentages of Selected Molecular Orbitals for 3, 4, 7, and 8
HOMO−1
HOMO
LUMO
LUMO+1
3
4
7
8
3
4
7
8
3
4
7
8
3
4
7
8
Pt
(Pt1)
(Pt2)
14
1
7
2
6
0
6
6
10
3
8
6
2
6
6
33
7
1
44
0
0
7
1
12
1
10
0
13
1
6
1
6
55
6
2
0
5
52
3
6
1
0
3
2
Ag
1
2
1
49
5
4
Cl
1
3
0
1
2
1
1
11
44
1
13
39
Other
83
82
85
84
85
84
85
85
27
95
34
39
97
95
a
The composition percentages were expressed in terms of contributions from each Pt metal center, four or two Ag metal centers, Cl ligands, and
Ph2pz ligands (including neutral Ph2pzH ligands for 4).
that the contribution of Cl atoms to LUMO (6% for 3
(Pt2Ag4Cl2) and 3% for 7 (Pt2Ag4Cl)) increases with increase
of chloride/pyrazolate ratio, while the Cl atom little contributes
to the HOMO (less than 1%) (Table 2). Though the calculated
HOMO−LUMO energy difference is not exactly the same as
the emission energy, in particular, in the case of the
phosphorescence, the decreasing trend of the LUMO energy
is parallel to the decreasing order of the emission energy
(Figure 11). This suggests that the trend of emission energy is
mainly determined by the LUMO energy shift. Therefore the
coordination of chloride ligands to PtII centers stabilizes the
L
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photodetector (Hamamatsu PMA-11, model C5966−23) and the
third-harmonic generation of an Nd:YAG Laser (Continuum Surelite)
at 355 nm excitation. The instrumental responses of the system were
corrected by using a software package for the detector. Lifetime
measurements were conducted by using a streak camera (Hamamatsu
C4334) as a detector. Emission quantum yields in the solid state were
determined by using a Hamamatsu Photonic Absolute PL Quantum
Yield Measurement System C9920−02. Powder X-ray diffraction
patterns were measured on a Rigaku RINT-2200VL diffractometer
using graphite-monochromated Cu Kα (λ = 1.5418 Å) radiation at 296
K.
LUMOs of 3 and 7, leading to the red shift of the emission
spectra.
In contrast, the HOMO of 4 mainly consists of dδ orbital of
PtII mixing with π* orbitals of bridging Ph2pz ligands, and the
LUMO of 4 mainly consists of π* orbitals of neutral Ph2pzH
ligands which are monodentate ligands. Thus it is likely that the
low-energy absorption bands of 4 include the ligand-to-ligand
charge-transfer (LLCT) and the metal-to-ligand charge-transfer
(MLCT) transitions. Similarly to [Pt2Cu4(μ-Me2pz)8]26 and
[Pt2Au2Cu2(μ-Me2pz)8],27 the HOMO of 5 also mainly
consists of Cu d orbitals, owing to higher orbital energy of
Cu(3d) than that of Pt(5d). Since the LUMO of 5 mainly
consists of π* orbitals of neutral monodentate Ph2pzH ligands,
the low-energy absorption bands of 5 contain the MLCT
character (Supporting Information Table S11).
Preparation of Complexes. [PtCl(Ph2pzH)3]Cl (1). A toluene
solution (15 mL) of Ph2pzH (136 mg, 0.62 mmol) was added to a
suspension of [PtCl2(C2H5CN)2] (60 mg, 0.16 mmol) in toluene (5
mL), and the suspension was refluxed for 10 h under an argon
atmosphere. Yellowish-white precipitate was filtered, washed with
toluene, hexane and diethyl ether, and dried in vacuo. Yield: 137 mg
(93%). Anal. Calcd for C45H36Cl2N6Pt: C, 58.32; H, 3.92; N, 9.07.
1
CONCLUSIONS
Found: C, 58.38; H, 3.92; N, 9.11. H NMR (300 MHz, CDCl3, 25
■
°C, TMS): δ = 15.52 (s, 1H, NH), 14.40 (s, 2H, NH), 8.22−8.19 (m,
4H, Ph), 7.92 (d, J = 7.2 Hz, 4H, Ph), 7.83 (d, J = 7.1 Hz, 2H, Ph),
7.52−7.34 (m, 15H, Ph), 7.09 (d, J = 7.0 Hz, 2H, Ph), 6.91 (d, J = 7.3
Hz, 1H, Ph), 6.65 (d, J = 2.1 Hz, 2H, H4), 6.59 (t, J = 7.6 Hz, 2H, Ph),
6.39 ppm (d, J = 2.3 Hz, 1H, H4). FABMS: m/z 891.3 [M − Cl]+.
[PtCl(Ph2pz)(Ph2pzH)2] (2). A solution of KOH (35 mg, 0.62 mmol)
in methanol (2 mL) was added dropwise to a suspension of 1 (198
mg, 0.21 mmol) in methanol (18 mL) with stirring at 25 °C, so that
the white-yellow suspension immediately changed to white. After
stirring for 1 h, the formed white solid was collected, washed with
methanol and water, and then dried in vacuo. Yield: 173 mg (91%).
Anal. Calcd for C45H35ClN6Pt: C, 60.71; H, 3.96; N, 9.44. Found: C,
60.68; H, 3.93; N, 9.29. 1H NMR (300 MHz, CDCl3, 25 °C, TMS): δ
= 8.12 (d, J = 7.7 Hz, 4H, Ph of Ph2pzH), 7.93 (d, J = 7.7 Hz, 2H, Ph
of Ph2pz), 7.50−7.23 (m, 21H, Ph), 7.25 (t, J = 7.6 Hz, 2H, Ph of
Ph2pz), 7.06 (t, J = 7.4 Hz, 1H, Ph of Ph2pz), 6.45 (s, 2H, H4 of
Ph2pzH), 6.24 ppm (s, 1H, H4 of Ph2pz). FABMS: m/z 890.3 [M]+.
[Pt2Ag4(μ-Cl)2(μ-Ph2pz)6] (3). To a suspension of 2 (54 mg, 0.061
mmol) in acetonitrile (10 mL) were added Et3N (18 mg, 0.18 mmol)
and a solution of AgBF4 (26 mg, 0.13 mmol) in acetonitrile (10 mL).
The suspension was stirred for 5 h at 25 °C to give a clear solution.
After filtration, the filtrate was concentrated almost to dryness by a
rotary evaporator. Methanol (30 mL) was added to the flask. The
resulted white precipitate was collected, washed with methanol, and
then dried in vacuo. Yield: 59 mg (89%). It was recrystallized from
CH2Cl2/CH3OH. Anal. Calcd for C90H66Ag4Cl2N12Pt2: C, 48.96; H,
3.01; N, 7.61. Found: C, 48.89; H, 2.90; N, 7.64. 1H NMR (300 MHz,
CDCl3, 25 °C, TMS): δ = 7.78 (d, J = 7.1 Hz, 4H, Ph), 7.68−7.65 (m,
4H, Ph), 7.47−7.36 (m, 14H, Ph), 7.24−7.16 (m, 10H, Ph), 7.09−
7.03 (m, 8H, Ph), 6.87 (d, J = 4.4 Hz, 10H, Ph), 6.83 (s, 2H, Ph), 6.70
(t, J = 7.5 Hz, 4H, Ph), 6.36 (d, J = 2.4 Hz, 2H, H4), 5.97 (d, J = 2.6
Hz, 2H, H4), 5.88 (d, J = 2.5 Hz, 2H, H4), 5.85 (d, J = 6.9 Hz, 4H, Ph).
FABMS: m/z 2208.1 [M + H]+
By taking advantages of weak basicity and bulkiness of 3,5-
diphenylpyrazole, we succeeded to prepare the mononuclear
PtII complex consisting of three neutral Ph2pzH ligands and a
chloride ligand, 1. The treatment of 1 with a base and
successive reaction with AgI give the Pt2Ag4Cl2 complex, 3,
which exhibits red-orange emission in the solid state at an
ambient temperature. The red-orange emission of 3 is very
unique, because the Pt2Ag4 complexes with 3,5-dialkylpyrazo-
late, [Pt2Ag4(μ-R2pz)8], has tendency to exhibit sky-blue to
green emission. The replacement of chloride ligands in 3 with
Me2pz ligands afforded the Pt2Ag4Cl(Me2pz) complex, 7, and
the Pt2Ag4(Me2pz)2 complex, 8, respectively. The red-orange
emission of 3, yellow-orange emission of 7, and green emission
of 8 revealed that the emission energies of the series of
heterohexanuclear PtII complexes is systematically modulated
by the ratio of coordinated chloride ligands to pyrazolate
ligands. It implies that the coordination of chloride ligands to
PtII ions affects the whole orbital energies of Pt2Ag4 complexes.
DFT calculations indicate that the highest occupied molecular
orbital (HOMO) as well as HOMO-1 of the heterohexanuclear
complexes, 3, 7, and 8, having Pt2Ag4 core, mainly consists of
dδ orbital of PtII and π orbitals of Ph2pz ligands, while the
lowest unoccupied molecular orbital (LUMO) of these
complexes mainly consists of in-phase combination of 6p of
two PtII centers and 5p of four AgI centers. Thus it is likely that
the emissions of 3, 7, and 8 are attributed to emissive states
derived from the Pt2(d)/π→Pt2Ag4 transitions. Careful
examination of the DFT computational results further revealed
that the bonding contribution of Cl atoms to LUMO increases
with increase of chloride/pyrazolate ratio, while the Cl atom
little contributes to the HOMO. These results are consistent
with the fact that the coordination of chloride ligands to PtII
centers stabilizes the LUMOs of 3 and 7, leading to the red
shift of the emission spectrum.
[Pt2Ag2Cl2(μ-Ph2pz)4(Ph2pzH)2] (4). Method A. To a suspension of
2 (58 mg, 0.065 mmol) in acetonitrile (8 mL) was added a solution of
AgBF4 (26 mg, 0.13 mmol) in acetonitrile (10 mL). The suspension
was stirred for 2 h at 25 °C, and the resulted white precipitate was
collected, washed with acetonitrile, and dried in vacuo. Yield: 27 mg
(45%). It was recrystallized from CHCl3/CH3CN. Anal. Calcd for
C90H68Ag2Cl2N12Pt2: C, 54.20; H, 3.44; N, 8.43. Found: C, 53.84; H,
EXPERIMENTAL SECTION
Materials. [PtCl2(C2H5CN)2] was prepared by the literature
methods.33 All other commercially available reagents were used as
purchased.
■
1
3.39; N, 8.46. H NMR (300 MHz, CDCl3, 25 °C, TMS): δ = 11.34
(s, 2H, NH), 7.98 (d, J = 7.0 Hz, 2H, Ph), 7.90−7.87 (m, 4H, Ph),
7.73 (d, J = 7.3 Hz, 4H, Ph), 7.67 (d, J = 6.9 Hz, 4H, Ph), 7.48 (d, J =
6.5 Hz, 4H, Ph), 7.43−7.06 (m, 26H, Ph), 6.97 (t, J = 7.4 Hz, 2H, Ph),
6.86−6.69 (m, 4H, Ph), 6.61 (d, J = 2.2 Hz, 2H, H4), 6.52 (t, J = 7.4
Hz, 2H, Ph), 6.32 (t, J = 7.5 Hz, 4H, Ph), 6.15 (d, J = 2.0 Hz, 2H, H4),
5.93 (d, J = 6.9 Hz, 4H, Ph), 5.68 ppm (s, 2H, H4).
Physical Measurement and Instrumentation. UV−vis and
diffuse reflectance spectra were recorded on a Hitachi U-3300
spectrophotometer and a Jasco V-560 spectrophotometer at 20 °C.
Electrical conductivity was measured using a TOA EC meter CM-30G.
The 1H NMR spectra were obtained at 300 MHz with a Varian
Method B. To a suspension of 2 (60 mg, 0.067 mmol) in
acetonitrile (8 mL) were added Et3N (6.1 mg, 0.060 mmol) and a
solution of AgBF4 (13 mg, 0.065 mmol) in acetonitrile (10 mL). The
suspension was stirred for 6 h at 25 °C, and the resulted white
1
Gemini 300 spectrometer. The variable-temperature H NMR spectra
were obtained at 400 MHz with a JEOL JNM-AL400 spectrometer.
Corrected emission spectra were obtained by using a red-sensitive
M
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Table 3. Crystallographic Data for [PtCl(Ph2pz)(Ph2pzH)2]·CH3OH (2·CH3OH), [Pt2Ag4(μ-Cl)2(μ-Ph2pz)6]·3CH2Cl2
(3·3CH2Cl2), [Pt2Ag2Cl2(μ-Ph2pz)4(Ph2pzH)2]·2CH3CN (4·2CH3CN), [Pt2Cu2Cl2(μ-Ph2pz)4(Ph2pzH)2]·2CH3CN
(5·2CH3CN), [Pt2Ag4(μ-Cl)(μ-Me2pz)(μ-Ph2pz)6]·0.5CH3OH·0.5H2O (7·0.5CH3OH·0.5H2O), and [Pt2Ag4(μ-Me2pz)2(μ-
Ph2pz)6] (8)
2·CH3OH
3·3CH2Cl2
4·2CH3CN
formula
fw
C46H39ClN6OPt
922.40
C93H72Ag4Cl8N12Pt2
2462.95
C94H74Ag2Cl2N14Pt2
2076.53
T [K]
296
296
296
λ [Å]
0.71070
0.71070
0.71070
crystal systems
space group
a [Å]
monoclinic
P21/n (14)
15.8874(10)
9.6977(4)
27.367(2)
90
triclinic
orthorhombic
P1 (2)
̅
Pnna (52)
15.438(3)
17.477(3)
17.818(3)
80.488(3)
84.636(3)
77.718(3)
4624.3(12)
2
18.1830(4)
b [Å]
22.6303(5)
c [Å]
20.1687(4)
α [deg]
β [deg]
γ [deg]
V [Å3]
Z
90
105.6240(9)
90
90
90
4060.7(4)
4
8299.1(3)
4
ρcalcd [g cm−3
]
1.509
1.769
1.662
μ(Mo Kα) [mm−1
]
3.550
4.112
3.931
reflns collected
29287
35378
59486
no. unique reflns
9132 (Rint = 0.0493)
R1 = 0.072 [I > 2σ(I)]
19799 (Rint = 0.025)
R1 = 0.060 [I > 2σ(I)]
9437 (Rint = 0.028)
R1 = 0.042 [I > 2σ(I)]
a
final R indices
b,
c
d
d
d
d
d
d
R indices
R = 0.090, Rw = 0.115
R = 0.069, Rw = 0.174
R = 0.046, Rw = 0.086
goodness-of-fit on F2
1.290
1.10
1.22
5·2CH3CN
7·0.5CH3OH·0.5H2O
8
formula
fw
C94H74Cl2Cu2N14Pt2
1987.89
296
C95.5H76Ag4ClN14Pt2
2292.85
C100H80Ag4N16Pt2
2327.49
T [K]
296
296
λ [Å]
0.71070
orthorhombic
Pnna (52)
18.3146(5)
22.6251(5)
19.7815(5)
90
0.71070
0.71070
crystal systems
space group
a [Å]
triclinic
triclinic
P1 (2)
̅
P1 (2)
̅
13.8447(4)
15.3018(5)
41.1566(13)
94.524(2)
92.992(2)
90.787(2)
8678.6(5)
4
14.544(2)
14.751(2)
22.063(2)
95.221(3)
92.255(3)
112.527(4)
4339.9(7)
2
b [Å]
c [Å]
α [deg]
β [deg]
γ [deg]
V [Å3]
Z
ρcalcd [g cm−3
μ(Mo Kα) [mm−1
90
90
8196.9(4)
4
]
1.611
1.755
1.781
]
4.023
4.168
4.139
rflns collected
58362
54612
32572
no. of unique rflns
9141 (Rint = 0.029)
32082 (Rint = 0.038)
R1 = 0.071 [I > 2σ(I)]
R = 0.078, Rw = 0.212
1.13
18453 (Rint = 0.061)
a
final R indices
R1 = 0.045 [I > 2σ(I)]
R1 = 0.097 [I > 2σ(I)]
R = 0.110, Rw = 0.302
1.08
b,
c
d
d
R indices
goodness-of-fit on F2
R = 0.047, Rw = 0.091
1.21
a
b
c
d
2
2
2
2
R1 = ∑∥Fo| − |Fc∥/Σ|Fo|. R = ∑(Fo − Fc2)/∑Fo . Rw = [∑[w(Fo − Fc2)2]/∑[w(Fo )2]]1/2
. All data.
precipitate was collected, washed with acetonitrile, and dried in vacuo.
Yield: 60 mg (89%). It was recrystallized from CHCl3/CH3CN.
[Pt2Cu2Cl2(μ-Ph2pz)4(Ph2pzH)2] (5). To a solution of 2 (149 mg,
0.17 mmol) in dichloromethane (7 mL) were added a solution of
[Cu(CH3CN)4]BF4 (61 mg, 0.19 mmol) in dichloromethane (10 mL)
and Et3N (18 mg, 0.18 mmol). The solution turned to yellow
suspension immediately after the addition of Et3N, and the suspension
was stirred for 6 h to give pale yellow solution. The solution was
evaporated to dryness. The resulted solid was collected, washed with
acetonitrile and diethyl ether, and dried in vacuo. Yield: 128 mg
(80%). It was recrystallized from CHCl3/CH3CN. Anal. Calcd for
C90H68Cu2Cl2N12Pt2: C, 56.72; H, 3.60; N, 8.82. Found: C, 56.43; H,
(d, J = 1.7 Hz, 2H, NH), 7.66−7.58 (m, 12H, Ph), 7.47 (d, J = 1.5 Hz,
2H, Ph), 7.45 (s, 2H, Ph), 7.36 (t, J = 7.4 Hz, 4H, Ph), 7.31−7.04 (m,
18H, Ph), 6.95−6.90 (m, 8H, Ph), 6.77 (t, J = 7.6 Hz, 4H, Ph), 6.56 (s,
2H, H4), 6.51 (d, J = 7.5 Hz, 2H, Ph), 6.40 (t, J = 7.5 Hz, 4H, Ph),
6.10 (s, 2H, H4), 5.94 (d, J = 7.7 Hz, 4H, Ph), 5.72 ppm (d, J = 2.2 Hz,
2H, H4).
[Pt(Ph2pz)2(Me2pzH)(Ph2pzH)] (6). A solution of KOH (40 mg,
0.71 mmol) in methanol (5 mL) was added to a solution of Me2pzH
(68 mg, 0.71 mmol) in methanol (5 mL), and the mixture was stirred
for 10 min at 25 °C. A solid of K[Me2pz] was obtained by removing
solvent from the solution. To a flask containing K[Me2pz] was added a
solution of 2 (577 mg, 0.65 mmol) in acetonitrile (40 mL), and the
solution was refluxed for 24 h under an argon atmosphere. Reduction
1
3.41; N, 8.86. H NMR (300 MHz, CDCl3, 25 °C, TMS): δ = 11.53
N
dx.doi.org/10.1021/ic202663q | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
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of the solution volume gave white precipitate. It was collected, washed
with acetonitrile and hexane, and dried in vacuo. Yield: 248 mg (40%).
Recrystallization from CHCl3/CH3OH gave fine crystals, which
include chloroform molecules as solvent of crystallization. Anal.
Calcd for C51H43Cl3N8Pt (6·CHCl3): C, 57.28; H, 4.05; N, 10.48.
Found: C, 57.28; H, 3.90; N, 10.48. 1H NMR (400 MHz, CDCl3, −50
°C, TMS): δ = 7.97 (m, 7H, Ph), 7.84 (d, J = 7.4 Hz, 2H, Ph), 7.51−
7.24 (m, 19H, Ph), 7.06 (m, 2H, Ph), 6.70 (s, 1H, H4 of Ph2pz), 6.21
(s, 1H, H4 of Ph2pz), 6.04 (s, 1H, H4 of Ph2pz), 5.48 (s, 1H, H4 of
Me2pz), 1.97 (s, 3H, Me), 1.71 ppm (s, 3H, Me). FABMS: m/z 950.4
[M + H]+.
structural analysis, we have not succeeded in preparing another crystals
suitable for X-ray structural analysis.
The crystal structures of 2·CH3OH and 5·2CH3CN were solved by
direct method (SIR92).35 Those of 3·3CH2Cl2, 4·2CH3CN,
7·0.5CH3OH·0.5H2O, and 8 were solved by heavy-atom method by
using DIRDIF.36 The positional and thermal parameters of non-H
atoms were refined anisotropically by the full-matrix least-squares
2
method. The minimized function was Σw(Fo − Fc2)2. Hydrogen
atoms were included at calculated positions with fixed displacement
parameters except for the hydrogen atoms in Ph2pzH ligands
participating in the hydrogen bonding in 2·CH3OH. In the final
cycle of the refinement, parameter shifts were less than 0.1σ. No
correction was made for secondary extinction.
[Pt2Ag4(μ-Cl)(μ-Me2pz)(μ-Ph2pz)6] (7). Method A. To a suspension
of 1 (301 mg, 0.33 mmol) were added a solution of Me2pzH (34 mg,
0.35 mmol) in acetonitrile (10 mL) and Et3N (32 mg, 0.32 mmol).
The suspension was refluxed for 5 h under an argon atmosphere. The
formed yellow-white solid was collected, washed with hexane and
All calculations were performed using the CrystalStructure37
crystallographic software package except for refinement, which was
performed using SHELXL-97.38 Further crystallographic data are given
in Table 3. Listings of the selected bond distances and angles are
summarized in Supporting Information Tables S1−S6.
1
methanol, and dried in vacuo. Yield: 180 mg. H NMR spectrum,
FABMS (m/z 890.3, 950.4), and the molar conductivity indicate that
the solid consists of 2 and 6 (see Supporting Information). This solid
was used for further reaction with silver ion without purification. To a
suspension of the above solid (107 mg) in acetonitrile (30 mL) were
added a solution of AgBF4 (82 mg, 0.42 mmol) in acetonitrile (10 mL)
and Et3N (22 mg, 0.22 mmol). The suspension was stirred for 3 h at
25 °C. Reduction of the solution volume gave white precipitate. It was
collected, washed with methanol, and dried in vacuo. The precipitate
was dissolved into chloroform to separate the fine solid of AgCl from
the solution. An addition of methanol to the solution followed by slow
evaporation of the solution gave crystalline compound. Yield: 41 mg
(19% (based on 1)). Anal. Calcd for C95H73Ag4ClN14Pt2: C, 50.32; H,
3.24; N, 8.65. Found: C, 50.16; H, 3.04; N, 8.33. 1H NMR (300 MHz,
CDCl3, 25 °C, TMS): δ = 7.82 (d, J = 6.9 Hz, 2H, Ph), 7.48−6.77 (m,
52H, Ph), 6.67 (t, J = 7.3 Hz, 2H, Ph), 6.40 (d, J = 2.5 Hz, 1H, H4 of
Ph2pz), 6.33 (d, J = 2.5 Hz, 1H, H4 of Ph2pz), 6.18 (d, J = 6.9 Hz, 2H,
Ph),6.11 (d, J = 2.7 Hz, 1H, H4 of Ph2pz), 5.92 (d, J = 6.9 Hz, 2H, Ph),
5.88 (d, J = 2.5 Hz, 2H, H4 of Ph2pz), 5.78 (d, J = 2.7 Hz, 1H, H4 of
Ph2pz), 5.11 (d, J = 2.3 Hz, 1H, H4 of Me2pz), 1.56 (s, 3H, Me), 1.24
ppm (s, 3H, Me). FABMS: m/z 2268.1 [M]+.
Computational Methods. The geometries of 3, 4, 5, 7, and 8
were optimized with the DFT method, where B3LYP functional was
employed.39−41 X-ray structures were used as initial geometries
without any geometrical constraints. In these calculations, for all
metals, basis sets with ECPs proposed by Christiansen et al were
employed.42−44 In details, for Cu, Ag, and Pt atoms, (761/6711/411),
(541/541/211), and (541/5511/211) basis sets were used,
respectively. For Cl, C, N, and H atoms, usual cc-pVDZ basis sets
were used.45,46 All calculations were carried out using the Gaussian 03
package.47 Molecular orbitals with the isovalue of 0.02 were drawn by
the Gauss View 4.1.48
ASSOCIATED CONTENT
■
S
* Supporting Information
Characterization of intermediate species, crystallographic data,
and tables of selected bond lengths and angles for 2·CH3OH,
3·3CH2Cl2, 4·2CH3CN, 5·2CH3CN, 7·0.5CH3OH·0.5H2O,
and 8, optimized geometries, special plot of selected molecular
orbitals for 5, excitation, emission and diffuse reflectance
spectra of 3, 4, 7, and 8, emission spectra of 6, VT NMR
Method B. To a solution containing 2 (45 mg, 0.051 mmol) and 6
(48 mg, 0.050 mmol) in acetonitrile (20 mL) were added a solution of
AgBF4 (41 mg, 0.21 mmol) in acetonitrile (5 mL) and Et3N (11 mg,
0.11 mmol). The solution was stirred for 3 h at 25 °C. Reduction of
the solution volume gave white precipitate. It was collected, washed
with methanol, and dried in vacuo. Yield: 78 mg (69%). It was
recrystallized from CHCl3/CH3OH.
1
spectra of 2, H NMR spectra of the intermediate species with
related complexes, and crystal structures of 3, 4, 5, 7, and 8.
This material is available free of charge via the Internet at
http://pubs.acs.org.
[Pt2Ag4(μ-Me2pz)2(μ-Ph2pz)6] (8). To a solution of 6 (105 mg, 0.11
mmol) in acetonitrile (20 mL) were added Et3N (23 mg, 0.23 mmol)
and a solution of AgBF4 (45 mg, 0.23 mmol) in acetonitrile (10 mL).
The solution was stirred for 3 h at 25 °C. Reduction of the solution
volume gave white precipitate. It was collected, washed with methanol,
dried in vacuo, and then recrystallized from CHCl3/CH3OH. Yield 26
mg (21%). Anal. Calcd for C100H80Ag4N16Pt2: C, 51.61; H, 3.46; N,
9.63. Found: C, 51.39; H, 3.32; N, 9.54. 1H NMR (300 MHz, CDCl3,
25 °C, TMS): δ = 7.39−6.71 (m, 56H, Ph), 6.38 (d, J = 2.4 Hz, 4H,
Ph), 6.35 (d, J = 2.2 Hz, 2H, H4 of Ph2pz), 5.99 (d, J = 2.5 Hz, 2H, H4
of Ph2pz), 5.84 (d, J = 2.5 Hz, 2H, H4 of Ph2pz), 4.83 (d, J = 2.3 Hz,
2H, H4 of Me2pz), 1.52 (s, 6H, Me), 1.26 ppm (s, 6H, Me).
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: kumks@nagasaki-u.ac.jp.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was partially supported by a Grant-in-Aid for
Scientific Research (No. 21550062).
X-ray Structural Determinations. Crystals suitable for X-ray
structural analysis were obtained by recrystallization from CH2Cl2/
CH3OH (2·CH3OH, 3·3CH2Cl2), CHCl3/CH3CN (4·2CH3CN,
5·2CH3CN), and CHCl3/CH3OH (7·0.5CH3OH·0.5H2O, 8), re-
spectively. The crystal of 7·0.5CH3OH·0.5H2O, and 8 were mounted
on a glass fiber, while the crystals, 2·CH3OH, 3·3CH2Cl2, 4·2CH3CN,
and 5·2CH3CN were sealed in thin-walled glass capillaries. Intensity
data were collected on a Mercury CCD area detector coupled with a
Rigaku AFC7S diffractometer using graphite-monochromated Mo Kα
(λ = 0.71070 Å) radiation at 296 K. Final cell parameters were
obtained from a least-squares analysis of reflections with I > 10σ(I).
The data were corrected for Lorentz and polarization effects. An
empirical absorption correction was applied.34 We have noticed a low
completeness of data collection for 7·0.5CH3OH·0.5H2O during
REFERENCES
(1) Espinet, P.; Fornies
Moreno, M. T.; Ruiz, A.; Welch, A. J. J. Chem. Soc., Dalton Trans. 1990,
■
́
, J.; Martinez, F.; Tomas
́
, M.; Lalinde, E.;
791−798.
(2) Yam, V. W.-W.; Yu, K.-L.; Cheung, K.-K. J. Chem. Soc., Dalton
Trans. 1999, 2913−2915.
́ ́
(3) Charmant, J. P. H.; Fornies, J.; Gomez, J.; Lalinde, E.; Merino, R.
I.; Moreno, M. T.; Orpen, A. G. Organometallics 1999, 18, 3353−3358.
(4) Ara, I.; Fornies, J.; Gomez, J.; Lalinde, E.; Moreno, M. T.
́
́
Organomeistallics 2000, 19, 3137−3144.
(5) Yam, V. W.-W.; Hui, C.-K.; Yu, S., -Y.; Zhu, N. Inorg. Chem. 2004,
43, 812−821.
O
dx.doi.org/10.1021/ic202663q | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
(6) Fornies
M. T. Chem.Eur. J. 2006, 12, 8253−8266.
(7) Gil, B.; Fornies, J.; Gomez, J.; Lalinde, E.; Martín, A.; Moreno, M.
́
, J.; Fuertes, S.; Martín, A.; Sicilia, V.; Lalinde, E.; Moreno,
System, Technical Report; Crystallography Laboratory, University of
Nijmegen: The Netherlands, 1994.
(37) CrystalStructure 4.0: Crystal Structure Analysis Package; Rigaku
́
́
Corporation: Tokyo, Japan, 2000−2010.
T. Inorg. Chem. 2006, 45, 7788−7798.
(38) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112−122.
(39) Becke, A. D. J. Chem. Phys. 1992, 96, 2155−2160.
(8) Leung, S. Y.-L.; Lam, W. H.; Zhu, N.; Yam, V. W.-W.
Organometallics 2010, 29, 5558−5569.
(40) Becke, A. D. J. Chem. Phys. 1993, 98, 5648−5652.
(9) Chen, Z.-N.; Zhao, N.; Fan, Y.; Ni, J. Coord. Chem. Rev. 2009,
253, 1−20.
(41) Lee, C.; Yang, W.; Parr, R. G. Phys. Rev. B 1988, 37, 785−789.
(42) Hurley, M. M.; Pacios, L. F.; Christiansen, P. A.; Ross, R. B.;
Ermler, W. C. J. Chem. Phys. 1986, 84, 6840−6850.
́
(10) Díez, A.; Lalinde, E.; Moreno, M. T. Coord. Chem. Rev. 2011,
255, 2426−2447.
(43) LaJohn, L. A.; Christiansen, P. A.; Ross, R. B.; Atashroo, T.;
Ermler, W. C. J. Chem. Phys. 1987, 87, 2812−2824.
(11) Berenguer, J. R.; Lalinde, E.; Moreno, M. T. Coord. Chem. Rev.
2010, 254, 832−875.
(44) Ross, R. B.; Powers, J. M.; Atashroo, T.; Ermler, W. C.; LaJohn,
L. A.; Christiansen, P. A. J. Chem. Phys. 1990, 93, 6654−6670.
(45) Woon, D. E.; Dunning, T. H. J. Chem. Phys. 1993, 98, 1358−
1371.
(12) Berenguer, J. R.; Fornies
T. Organometallics 2001, 20, 4847−4851.
(13) Fernandez, J.; Fornies, J.; Gil, B.; Gom
Moreno, M. T. Organometallics 2006, 25, 2274−2283.
(14) Berenguer, J. R.; Fornies
, J.; Gil, B.; Lalinde, E. Chem.Eur. J.
2006, 12, 785−795.
(15) Berenguer, J. R.; Gil, B.; Fernandez, J.; Fornies, J.; Lalinde, E.
Inorg. Chem. 2009, 48, 5250−5262.
(16) Fornies, J.; Fuertes, S.; Martin, A.; Sicilia, V.; Gil, B.; Lalinde, E.
Dalton Trans. 2009, 2224−2234.
(17) Berenguer, J. R.; Fernandez, J.; Gil, B.; Lalinde, E.; San
Inorg. Chem. 2010, 49, 4232−4244.
(18) Berenguer, J. R.; Díez, A.; Fernndez, J.; Fornies
́ ́
, J.; Gomez, J.; Lalinde, E.; Moreno, M.
́
́
́
ez, J.; Lalinde, E.;
(46) Dunning, T. H. J. Chem. Phys. 1989, 90, 1007−1023.
(47) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;
Robb, M. A.; Cheeseman, J. R.; Montgomery, J. A. J.; Vreven, T.;
Kudin, K. N.; Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.;
Barone, V.; Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.;
Petersson, G. A.; Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.;
Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao,
O.; Nakai, H.; Klene, M.; Li, X.; Knox, J. E.; Hratchian, H. P.; Cross, J.
B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R.
E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.;
Ayala, P. Y.; Morokuma, K.; Voth, G. A.; Salvador, P.; Dannenberg, J.
J.; Zakrzewski, V. G.; Dapprich, S.; Daniels, A. D.; Strain, M. C.;
Farkas, O.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.; Foresman,
J. B.; Ortiz, J. V.; Cui, Q.; Baboul, A. G.; Clifford, S.; Cioslowski, J.;
Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi, I.;
Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.; Peng, C. Y.;
Nanayakkara, A.; Challacombe, M.; Gill, P. M. W.; Johnson, B.; Chen,
W.; Wong, M. W.; Gonzalez, C.; Pople, J. A. Gaussian 03, revision
C.02, Gaussian, Inc.: Wallingford CT, 2004.
́
́
́
́
́
́
chez, S.
́
, J.; García, A.;
Gil, B.; Lalinde, E.; Moreno, M. T. Inorg. Chem. 2008, 47, 7703−7716.
(19) Shavaleev, N. M.; Accorsi, G.; Virgili, D.; Bell, Z. R.; Lazarides,
T.; Calogero, G.; Armaroli, N.; Ward, M. D. Inorg. Chem. 2005, 44,
61−72.
(20) Ward, M. D. Coord. Chem. Rev. 2007, 251, 1663−1677.
(21) Xu, H.-B.; Zhang, L.-Y.; Xie, Z.-L.; Ma, E.; Chen, Z.-N. Chem.
Commun. 2007, 2744−2746.
(22) Chen, Z.-N.; Fan, Y.; Ni, J. Dalton Trans. 2008, 573−581.
(23) Li, X.-L.; Shi, L.-X.; Zhang, L.-Y.; Wen, H.-M.; Chen, Z.-N.
Inorg. Chem. 2007, 46, 10892−10900.
(48) Dennington, R.; Keith, T.; William, J. GaussView, version 4.1,
Gaussian, Inc.: Shawnee Mission, KS, 2007.
(24) Xu, H.-B.; Ni, J.; Chen, K.-J.; Zhang, L.-Y.; Chen, Z.-N.
Organometallics 2008, 27, 5665−5671.
(25) Xu, H.-B.; Zhang, L.-Y.; Chen, Z.-H.; Shi, L.-X.; Chen, Z.-N.
Dalton Trans. 2008, 4664−4670.
(26) Umakoshi, K.; Kojima, T.; Saito, K.; Akatsu, S.; Onishi, M.;
Ishizaka, S.; Kitamura, N.; Nakao, Y.; Sakaki, S.; Ozawa, Y. Inorg.
Chem. 2008, 47, 5033−5035.
(27) Umakoshi, K.; Saito, K.; Arikawa, Y.; Onishi, M.; Ishizaka, S.;
Kitamura, N.; Nakao, Y.; Sakaki, S. Chem.Eur. J. 2009, 15, 4238−
4242.
(28) Calculated values in SciFinder using Advanced Chemistry
Development (ACD/Laboratories) Software v11.02
(29) Ara, I.; Aranaz, J.; Fornies
1107.
́
, J. J. Fluorine Chem. 2010, 131, 1103−
(30) Albano, V. G.; Serio, M. D.; Monari, M.; Orabona, I.; Panunzi,
A.; Ruffo, F. Inorg. Chem. 2002, 41, 2672−2677.
(31) The Ag···Cl distances are by 0.5 Å less than van der Wasls
distance. However, the Cl−Pt−N(cis) angle is almost 90 degree and
the Cl−Pt−N(trans) angle is 174 degree, which is almost linear, as
seen in Table S3. If some coordination or covalent interaction exists
between Ag and Cl atoms, the Pt−Cl moiety would distort from the
planar geometry. It is likely that the rather short Ag···Cl distance arises
from electrostatic interaction between Ag and Cl.
(32) Miskowski, V. M.; Houlding, V. H.; Che, C.-M.; Wang, Y. Inorg.
Chem. 1993, 32, 2518−2524.
(33) Kukushkin, V. Y.; Oskarsson, Å.; Elding, L. I.; Jonasdottir, S.
Inorg. Synth. 1997, 31, 279−284.
(34) Jacobson, R. A. REQABS, version 1.1; Molecular Structure
Corp.: The Woodlands, TX, 1998.
(35) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A.;
Burla, M. C.; Polidori, G.; Camalli, M. J. Appl. Crystallogr. 1994, 27,
435−436.
(36) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.;
de Gelder, R.; Israel, R.; Smits, J. M. M. The DIRDIF94 Program
P
dx.doi.org/10.1021/ic202663q | Inorg. Chem. XXXX, XXX, XXX−XXX