Benzoquinolateplatinum(ii) complexes as building blocks in the synthesis of Pt-Ag extended structures

Article abstract of DOI:10.1039/c2dt11885h

The reaction between (NBu₄)[Pt(bzq)(C₆F ₅)₂] (1, bzq = 7,8-benzoquinolate) and AgClO₄ in a 1:1 molar ratio, in acetone, gives the polymer [{Pt(bzq)(C ₆F₅)₂}Ag]_n (2). The reaction of 2 with equimolecular amounts of PPh₃ and SC₄H₈ (tht) produces the bimetallic complexes [{Pt(bzq)(C₆F ₅)₂}AgL] (L = PPh₃ (3), tht (4)). For L = py, decomposition takes place and [Pt(bzq)(C₆F₅)py] (5) is obtained. All these complexes have been characterized by X-ray diffraction. The most interesting features of complexes 2-4 is the presence of Pt-Ag bonds, with Pt-Ag distances of ca. 2.75 A. Besides, the silver centres establish short η¹ bonding interactions with the C_ipso of the bzq ligands, with distances Ag-C of ca. 2.45 A. Complex 2 is a one-dimensional infinite chain in which the fragments "Pt(bzq)(C₆F ₅)₂^-" and Ag⁺ alternate. On the other hand, complexes 1 and 3-5 show intermolecular pairing through π...π interactions between the aromatic rings of the bzq ligand, having interplanar separations of ca. 3.5 A. Complex 2 dissolves in donor solvents (acetone, THF) as discrete bimetallic solvated fragments [{Pt(bzq)(C₆F₅)₂}AgS_n] (S = solvent), similar to complexes 3 and 4. The persistence of the Pt-Ag bond in 2-4, supported by multinuclear NMR spectroscopy, causes a significant blue-shift in the lowest-lying absorption in relation to 1. This fact is attributed (TD-DFT) to a remarkable modification of the orbitals contributing to the HOMO, which changes the character of the transition from ¹LC/ ¹MLCT in 1 to admixture ¹L′LCT/¹MLCT in the bimetallic complexes. The low energy feature (490-530 nm) of 2 in solid state is attributed to CT from the Pt fragments to the Ag centers. Complexes 2-4 are only emissive in rigid media (solid and glasses). In the solid state, the metallic chain 2 exhibits a bright orange emission (560 nm, 298 K; 590 nm, 77 K), assigned to an excited state involving charge transfer from the platinum fragment with a remarkable contribution of C₆F₅ (Ar _f) rings to the Pt-Ag bond (³LMM′CT/ ³L′M′CT). However, 3 and 4 exhibit in solid state at 298 K a vibronic band, which is clearly resolved in two close non-equilibrated bands at 77 K in 3, tentatively ascribed to a mixture of ³MLCT/ ³L′LCT transitions modified by the formation of the Pt-Ag bond. In glassy solution (77 K) 2-4 display a vibronic emission ascribed primarily to ³LC character. The Royal Society of Chemistry 2012.

Full text of DOI:10.1039/c2dt11885h

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PAPER
Benzoquinolateplatinum(II) complexes as building blocks in the synthesis of
Pt–Ag extended structures†
a
a
b
a
b
Juan Forniés, Susana Ibáñez, Elena Lalinde,* Antonio Martín,* M. Teresa Moreno
c
and Athanassios C. Tsipis*
Received 6th October 2011, Accepted 23rd December 2011
DOI: 10.1039/c2dt11885h
The reaction between (NBu )[Pt(bzq)(C F ) ] (1, bzq = 7,8-benzoquinolate) and AgClO in a 1 : 1 molar
4
6
5 2
4
ratio, in acetone, gives the polymer [{Pt(bzq)(C F ) }Ag] (2). The reaction of 2 with equimolecular
6
5 2
n
amounts of PPh and SC H (tht) produces the bimetallic complexes [{Pt(bzq)(C F ) }AgL] (L = PPh
3
3
4
8
6
5 2
(
3), tht (4)). For L = py, decomposition takes place and [Pt(bzq)(C F )py] (5) is obtained. All these
6 5
complexes have been characterized by X-ray diffraction. The most interesting features of complexes 2–4
is the presence of Pt–Ag bonds, with Pt–Ag distances of ca. 2.75 Å. Besides, the silver centres establish
1
short η bonding interactions with the C
of the bzq ligands, with distances Ag–C of ca. 2.45 Å.
ipso
−
+
Complex 2 is a one-dimensional infinite chain in which the fragments “Pt(bzq)(C F ) ” and Ag
6
5 2
alternate. On the other hand, complexes 1 and 3–5 show intermolecular pairing through π⋯π interactions
between the aromatic rings of the bzq ligand, having interplanar separations of ca. 3.5 Å. Complex 2
dissolves in donor solvents (acetone, THF) as discrete bimetallic solvated fragments [{Pt(bzq)(C F ) }
6
5 2
AgS ] (S = solvent), similar to complexes 3 and 4. The persistence of the Pt–Ag bond in 2–4, supported
n
by multinuclear NMR spectroscopy, causes a significant blue-shift in the lowest-lying absorption in
relation to 1. This fact is attributed (TD-DFT) to a remarkable modification of the orbitals contributing to
1
1
1
the HOMO, which changes the character of the transition from LC/ MLCT in 1 to admixture L′
1
LCT/ MLCT in the bimetallic complexes. The low energy feature (490–530 nm) of 2 in solid state is
attributed to CT from the Pt fragments to the Ag centers. Complexes 2–4 are only emissive in rigid media
(solid and glasses). In the solid state, the metallic chain 2 exhibits a bright orange emission (560 nm,
2
98 K; 590 nm, 77 K), assigned to an excited state involving charge transfer from the platinum fragment
3
3
with a remarkable contribution of C F (Ar ) rings to the Pt–Ag bond ( LMM′CT/ L′M′CT). However, 3
6
5
f
and 4 exhibit in solid state at 298 K a vibronic band, which is clearly resolved in two close non-
3
3
equilibrated bands at 77 K in 3, tentatively ascribed to a mixture of MLCT/ L′LCT transitions modified
by the formation of the Pt–Ag bond. In glassy solution (77 K) 2–4 display a vibronic emission ascribed
3
primarily to LC character.
Introduction
In the widely studied field of intermetallic bonds, metallophilic
interactions between closed shell (d , d , d s ) ions have
a
Departamento de Química Inorgánica –Instituto de Síntesis Química y
10
8
10 2
Catálisis Homógenea. Universidad de Zaragoza – C.S.I.C, 50009
1
–12
attracted a considerable amount of attention.
Among these
Zaragoza, Spain. E-mail: tello@unizar.es
b
8
Departamento de Química – Grupo de Síntesis Química de La Rioja,
types of interactions, the particular case of M(d )→M′ dative
bonds has been found in a rich variety of systems, mostly invol-
ving electron rich Pt(II) complexes as a framework donor invol-
ving the occupied dz orbital.
Heteropolymetallic complexes containing this kind of bond
UA–C.S.I.C. Universidad de La Rioja, 26006 Logroño, Spain
c
Laboratory of Inorganic and General Chemistry, Department of
Chemistry, University of Ioannina, 451 10 Ioannina, Greece and
Departamento de Química Inorgánica – Instituto de Ciencia de
Materiales de Aragón. Universidad de Zaragoza – C.S.I.C, 50009
Zaragoza, Spain(on sabbatical leave)
2
5,13–31
32
are interesting for several reasons. One is the utility of the metal–
metal bond as a tool in molecular or crystal engineering. Thus, it
is possible to find in the literature examples of a wide array of
structure types in which the metal–metal bond links together the
†
Electronic supplementary information (ESI) available: Complete
authors list for ref. 94. X-ray structural drawings and data for complexes
and 5 (Fig. S1–S2 and Tables S1–S3). Normalized absorption spectra
3
calculated from their reflectance diffuse spectra of 1, 2 and 4 in solid
state (Fig. S3). Details on the theoretical calculations carried out in 1–3
and 4′ (Fig. S4–S9 and Tables S4–S11). CCDC reference numbers
16,17,22,24
different subassemblies: linear bimetallic compounds,
16–18,24,30
33–35
trimetallic “sandwiches”
or triangles,
tetrametallic
8
47963–847967. For ESI and crystallographic data in CIF or other elec-
15,19,24
35–37
38
tronic format see DOI: 10.1039/c2dt11885h
“squares”
or tetrahedrons,
octanuclear stellate,
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Dalton Trans., 2012, 41, 3439–3451 | 3439

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Scheme 1
2
3,24
30
oligometallic “chains”,
that sometimes arrange in helical motifs in the crystal structure,
etc. Besides, complexes containing Pt–Ag bonds have been
infinite one-dimensional chains
L has allowed the synthesis of complexes of stoichiometry [{Pt
(bzq)(C F ) }AgL]. The reported complexes have been charac-
23
6
5 2
terised and studied by X-ray crystallography and NMR spec-
troscopy. Finally, their optical properties have been investigated
and time-dependent density functional theory (TD-DFT) calcu-
lations have been performed to shed light on the nature of the
electronic transitions.
1
4
shown to act as intermediates in halogen abstraction or Pt–C
cleavage reactions. Finally, some of these complexes exhibit
39
interesting
properties,
photophysical
and
photochemical
1
–10,18,31,40–52
which in some cases have been exclu-
sively attributed to the presence of metallophilic bonds. In other
polymetallic systems based on potential emissive polydentate
53–56
54
57–59
Results and discussion
groups (alkynyl,
thiolate, pyrazolate
…), the presence
of metallophilic bonds also plays a crucial role in their final
luminescent properties.
Synthesis and characterization
In the course of our current research, we have developed syn-
thetic methods for the preparation of complexes containing Pt–
M bonds, mainly based on the use of perhalophenyl platinate(II)
As we have already mentioned, we reported that the reaction of
(NBu )[Pt(bzq)(C F ) ] (1) with AgClO in 2 : 1 (or even in
4
6
5 2
4
1 : 1) molar ratio in acetone results in the isolation of the trinuc-
13,16,17,34,37,38,60–63
17
complexes.
Following our interest in this area,
lear “sandwich” complex (NBu )[{Pt(bzq)(C F ) } Ag].
4
6 5 2 2
we are now interested in exploring the synthesis and properties
of heteropolymetallic complexes based on anionic platinate
building blocks containing typical strong ligand field cyclometa-
However, if this reaction is carried out in a 1 : 1 molar ratio in
acetone and the solid resulting after evaporation to dryness is
treated with CH Cl , a yellow solid of formula [{Pt(bzq)
2
2
5
,15–18,64,65
lated C^N phosphors.
Thus, we have shown that by
(C F ) }Ag] is obtained from the solution (see Experimental
6 5 2
using the properties of the basic platinum(II) centre as a Lewis
section). The X-ray crystal structure of this complex (see below)
base in the anionic complex (NBu )[Pt(bzq)(C X ) ] (X = F, 1;
has revealed its polymeric nature [{Pt(bzq)(C F ) }Ag] (2) (see
4
6
5 2
6
5 2
n
Cl; bzq = 7,8-benzoquinolate), several luminescent complexes
Scheme 1).
stabilized by unsupported Pt–M (M = Cd, Ag) bonds can be
The molecular structures of 1 and 2 have been established by
X-ray diffraction studies. Fig. 1 shows the complex anion of 1
and Table 1 lists its most relevant bond distances and angles.
The most important feature found in the structure of 1 is the
pairing of anions though π⋯π interactions of the bzq ligand. The
16,17
easily generated.
A few years ago we reported several bi-
1
7
and trinuclear complexes containing Pt–Ag bonds and very
1
unusual η bonding interactions between the silver(I) centre and
the Cipso of the bzq ligand and additionally stabilized by short or
long-range π⋯π stacking interactions between the aromatic rings
of the bzq ligands. All these complexes exhibited interesting
photoluminescent properties, including the occurrence of a lumi-
nescence polymorphism associated to the trinuclear “sandwich”
complex (NBu )[{Pt(bzq)(C F ) } Ag].
−
two [Pt(bzq)(C F ) ] units stack their bzq planes (interplanar
6
5 2
distance of ca. 3.6 Å) with the bulky C F ligands oriented in
6
5
the opposite direction in order to avoid steric hindrance. This
π⋯π stacking has already been described in some neutral and
15–18,66–71
4
6 5 2 2
cationic benzoquinolate platinum complexes,
but is
In this paper we expand our study on the ability of the
rather uncommon in anionic systems with bulky counter cations
−
+
synthon [Pt(bzq)(C F ) ] to form new complexes of diverse
such as [NBu ] .
6
5 2
4
nuclearity containing Pt–Ag bonds. We have achieved the prep-
aration of a one-dimensional polymer containing an infinite
chain of formula [{Pt(bzq)(C F ) }Ag] (2). The reactivity of 2
More interesting is the crystal structure of 2, a view of which
is presented in Fig. 2. Table 2 contains the most important bond
lengths and angles. Complex 2 is a one-dimensional infinite
6
5 2
n
−
+
has been investigated and the cleavage of the chain with ligands
chain in which the fragments “[Pt(bzq)(C F ) ] ” and Ag
6 5 2
3440 | Dalton Trans., 2012, 41, 3439–3451
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6 5 2 n
Fig. 2 View of the molecular structure of [{Pt(bzq)(C F ) }Ag] (2).
Fig. 1 View of the molecular structure of the anion of (NBu
] (1).
4
)[Pt(bzq)
)[Pt(bzq)
(C
6
F
5
)
2
Table 2 Selected bond lengths (Å) and angles (°) for [{Pt(bzq)
a
6 5 2 n
(C F ) }Ag] (2)
Table 1 Selected bond lengths (Å) and angles (°) for (NBu
] (1)
4
Pt–C(7)
Pt–N
Pt–Ag′
Ag–C(23)
2.028(14)
2.108(9)
2.761(1)
2.398(11)
Pt–C(1)
Pt–C(23)
Pt–Ag
2.065(13)
2.109(14)
2.777(1)
6 5 2
(C F )
Pt–C(1)
Pt–N(1)
2.013(4)
2.080(3)
Pt–C(23)
Pt–C(7)
2.042(4)
2.088(4)
Ag–C(23′′)
2.507(11)
C(7)–Pt–C(1)
C(1)–Pt–N
C(1)–Pt–C(23)
C(7)–Pt–Ag′
N–Pt–Ag′
C(7)–Pt–Ag
N–Pt–Ag
Ag′–Pt–Ag
C(23)–Ag–Pt′′
C(23)–Ag–Pt
Pt′′–Ag–Pt
87.7(5)
95.3(4)
174.4(4)
94.7(3)
87.8(3)
89.1(3)
85.6(2)
116.9(1)
159.4(3)
47.4(3)
145.0(1)
C(7)–Pt–N
C(7)–Pt–C(23)
N–Pt–C(23)
C(1)–Pt–Ag′
C(23)–Pt–Ag′
C(1)–Pt–Ag
C(23)–Pt–Ag
C(23)–Ag–C(23′′)
C(23′′)–Ag–Pt′′
C(23′′)–Ag–Pt
174.7(4)
C(1)–Pt–C(23)
C(23)–Pt–N(1)
C(23)–Pt–C(7)
91.65(15)
81.56(14)
173.29(14)
C(1)–Pt–N(1)
C(1)–Pt–C(7)
N(1)–Pt–C(7)
171.83(13)
92.47(15)
94.73(13)
97.2(5)
80.0(4)
116.9(3)
60.2(3)
126.2(3)
56.8(3)
144.1(4)
46.9(3)
135.8(3)
alternate. Thus, each Pt centre forms two bonds with two Ag
centres, and alternatively, each silver(I) is bonded to two plati-
num(II). To the best of our knowledge, there is only one similar
complex formed by an infinite chain of Pt–Ag bonds, reported
23
a
by Yamaguchi et al. The Pt–Ag distances in 2 are 2.761(1) Å
The symmetry transformations used to generate equivalent atoms are
y − 1/4, −x + 7/4, z − 1/4 for the primed atoms and −y + 7/4, x + 1/4,
z + 1/4 for the double primed atoms.
and 2.777(1) Å, in the range found for other complexes with
13,17,23,24,34,35,38,60
Pt–Ag bonds.
Besides the Pt–Ag bonds, the silver centre establishes a short
1
η interaction with the C
of the bzq ligand [C(23) in Fig. 2],
ipso
the distances being Ag–C(23) = 2.398(11) Å and Ag–C(23′) =
are 116.9(1)° and 145.0(1)°, respectively. The dihedral angle
between two consecutive Pt platinum coordination planes is 10.3
(5)°. Moreover, the disposition of the ligands in the chain is such
that they are rotated 90° along the main axis of the chain with
respect to their positions in the preceding “Pt(bzq)(C F ) ” sub-
1
2
.507(11) Å. Similar η -Ag–C interactions have been previously
17,23
found in other cycloplatinate complexes with Pt–Ag bonds.
1
These η -Ag–C interactions are important and, along with the
Pt–Ag bonds contribute to fulfilling the electronic requirements
of the acidic silver centre and the formation of the infinite chain.
We note that the affinity of silver for some aromatic π-donor
6
5 2
unit, in this way configuring a helix (see Fig. 3). This is due to
the fact that the chain contains a crystallographic 4 axis, and
1
3
3,72–77
1
2
systems is well known,
the η and η coordination modes
thus the helical motif completes every four “Pt(bzq)(C F ) ”
6
5 2
being the most usual ones. Also, the Ag–C lines are usually
almost perpendicular to the plane of the aromatic rings, which is
almost accomplished in complex 2 taking into consideration the
additional constraints caused by the existence of the Pt–Ag
bonds. Thus the angles between the Ag–C lines and the perpen-
dicular to the best bzq planes are 11.9(6)° and 19.4(6)°. Due to
fragments and the length of the “({Pt(bzq)(C F ) }Ag) ” motif
6 5 2 4
is 14.13 Å. Since the space group in which 2 crystallises is cen-
trosymmetric (I4 /a), both the right and left-handed screw
1
helices are present in the crystal structure. A helical disposition
is also observed in the Pt–Ag chain reported by Yamaguchi
23
et al., but in this case the cycle of the helix comprises (PtAg)12
sub-units.
1
the formation of the η -Ag–C (bzq) contacts, the Pt–Ag bonds
lean toward the bzq ligand (angles with the perpendicular 35.2
The extended compound [{Pt(bzq)(C F ) }Ag] (2) is insolu-
ble in CH Cl , and thus, H and F NMR spectra were recorded
2 2
6
5 2
n
1
19
(4)° and 28.1(4)°) and the silver centres move away from the
bulky pentafluorophenyl groups (no o-F⋯Ag contacts are
observed).
in acetone-d at room temperature. The proton spectrum exhibits
6
19
the expected resonances for one kind of bzq ligand and the
F
The arrangement of the sequence of bonds ⋯Pt–Ag–Pt–Ag⋯
is not linear. The values of the Ag–Pt–Ag and Pt–Ag–Pt angles
NMR spectrum exhibits two sets of C6F5 AA′MM′X spin
systems. The equivalence of the two o-F and the two m-F on
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6 5 2 n
Fig. 3 View of the helical arrangement of the infinite chain in the molecular structure of [{Pt(bzq)(C F ) }Ag] (2).
each C F ring indicates that in acetone either the Pt–Ag bonds
S3†). The existence of two polymorphs for 3 and also for the
analogous silver sandwich complex [{Pt(bzq)(C F ) } Ag]
6 5 2 2
6
5
−
17
are cleaved or that a dynamic process (partial dissociation) is
195
operating. The Pt NMR spectrum was measured at two differ-
ent temperatures (298 K and 253 K) showing in both cases a
unique signal at −3330 and −3353 ppm respectively. These
values represent a high-field shift of the signal with respect to
the starting material 1 (−3705 ppm, 298 K). This, along with the
seems to indicate that these kinds of “Pt(bzq)” complexes con-
taining Pt–M dative bonds are likely to exist in different crystal-
line phases. Organometallic compounds are well known for their
structural flexibility and it has been suggested that this molecular
non-rigidity is related to the occurrence of polymorphism in the
78
low conductivity of the compound in acetone solution (Λ
=
structures of these systems. This flexibility has also been
M
1
2
−1
3
7.5 Ω− cm mol ), indicates that a dynamic dissociative
described in systems containing metallophilic bonds such as the
79
process is operating in acetone. Similar behaviour has been
trinuclear Pt–Ag–Pt complex (NBu )[{Pt(C F ) (tht)} Ag], or
4 6 5 3 2
reported by Yamaguchi et al. for complexes [Pt(phpy) Ag] or
the heterometallic clusters [Pt M (CuCR) ] (M = Cu, R = Ph,
2 4 8 n
2
x
80–82
[
Pt(thpy) Ag]x [Hphpy = 2-phenylpyridine, Hthpy = 2-(2-
n = 2, 3; M = Ag, R = C H -OMe , n = 1, ∞).
2
6
4
3
23
thyenyl)pyridine].
The crystal structure of 4 shows that, besides the tetrahy-
drothiophene ligand, the silver centre coordinates one acetone
molecule, which is one of the solvents used to obtain suitable
crystals for the X-ray study. Thus, the complex whose structure
we will discuss is better formulated as [{Pt(bzq)(C F ) }Ag(tht)
When an equimolar amount of PPh or tht (tetrahydrothio-
3
phene, SC H ) is added to a suspension of 2 in CH Cl and the
4
8
2
2
mixture is stirred for 60 min, all the solid present dissolves,
which seems to indicate that the cleavage of the infinite ⋯Pt–
Ag–Pt–Ag⋯ chain has taken place. After evaporation of the
solvent and treatment of the residue (see Experimental section)
the corresponding [{Pt(bzq)(C F ) }AgL] (L = PPh (3), tht (4))
6
5 2
(Me CO)] (4′). Fig. 4 shows the molecular structure of 4′ and
2
Table 3 lists its most relevant bond distances and angles. The
main feature is, as in 2 and 3, the interaction between the [Pt
(bzq)(C F ) ] and [Ag(tht)(Me CO)] fragments through Pt–Ag
6
5 2
3
complexes are isolated (see Scheme 1). Nevertheless, when L =
py only mixtures of products are obtained, of which we were
only able to identify [Pt(bzq)(C F )py] (5) through its crystal
6
5 2
2
(2.721(1) Å) and Ag–C(23) (2.463(3) Å) bonds. The Pt–Ag line
deviates significantly (31.4(1)°) from the perpendicular to the
best Pt square plane. The Ag–S distance is 2.445(1) Å, and the
Ag–O distance is 2.438(3) Å, both in the range usually found for
6
5
structure, which is reported in the ESI (Fig. S1, Tables S1 and
S2†). The formation of 5 indicates the occurrence of a more
favourable process, involving not only the breaking of the Pt–Ag
bond, but also of a Pt–C(C F ) bond.
23,60,79,83–87
this type of bonds.
The presence of the coordinated
acetone in 4′ and its absence in 3 can be explained by the differ-
ent steric requirements of the ligand bonded to silver. While in 3
the bulky PPh3 ligand “protects” the silver centre from the
approximation of a further ligand, in 4′ the less sterically
demanding tht allows the proximity of a small molecule such as
acetone on the side of the planar bzq ligand. It is interesting to
note that 4′ establishes weak π⋯π interactions in such a way that
the bzq ligands of two adjacent complexes stack with an inter-
planar distance of ca. 3.5 Å (see Fig. 4b), forming dimers in a
6
5
The preparation and structural characterization of [{Pt(bzq)
(
C F ) }Ag(PPh )] (3) and its analogue [{Pt(bzq)(C Cl ) }Ag
6
5 2
3
6
5 2
(
PPh )] had been previously carried out in our laboratory by
3
reacting 1 (or the pentachlorophenyl analogue) with [Ag(OClO )
3
1
7
(
PPh )] in a 1 : 1 molar ratio. In that case, the formation of 3
3
involved the formation of a Pt–Ag bond. In the method
described here the addition of the ligand L causes the cleavage
of one of the Pt–Ag bonds on each platinum centre in the poly-
meric structure of 2 and the entering ligand occupies the position
formerly occupied by one “Pt(bzq)(C F ) ” fragment. The exist-
1
6–18,66–71
similar way to 1, 3 or other “Pt(bzq)” complexes.
19
The F NMR spectra of 4 both at room temperature and at
6
5 2
ence of one Pt–Ag bond in 3 and 4 has been confirmed by X-ray
213 K in CDCl show the presence of two types of C F groups,
3
6 5
diffraction.
with typical AA′MM′X spin systems. This indicates that, in the
NMR time scale, the square planar Pt coordination plane is a
symmetry plane. The remarkable deshielding (∼200 ppm)
1
7
We had previously reported the crystal structure of 3, but
more recently we have been able to obtain new crystals of this
complex, which show different cell parameters from the reported
ones and which correspond to a new pseudo-polymorph of 3.
The relevant structural parameters of this new polymorph are
195
1
observed in its Pt{ H} NMR spectrum in CDCl at 253 K (m,
3
7
8
−3509 ppm) and the value of the conductivity in acetone sol-
ution (ΛM = 22.1 Ω− cm mol ) is in accordance with a
dynamic process involving partial dissociation of the Pt and Ag
fragments.
1
2
−1
17
very similar to those already reported in our previous paper,
and have been only included in the ESI (Fig. S2, Tables S1 and
3442 | Dalton Trans., 2012, 41, 3439–3451
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Table 4 Absorption data (2 × 10− M solutions) for complexes 1–4
5
Absorption/nm (10 ε/M cm−1
)
3
−1
Compound
(NBu
4
)[Pt(bzq)(C
6
F
5
)
2
] (1)
243(66.4), 260(58.4), 315(27.15),
45(20.1), 380(12.1), 425(6.9)
3
a,b
(
CH
2
Cl )
2
2
43(46.9), 262(40.3), 317(11.0), 352
(8.4), 399(5.6), 448(2.5) (THF)
2
15(21.0), 328(13.4), 344(12.0), 393
a
(
8.4), 422sh(5.8) (acetone)
65, 310, 357, 392, 434, 472 (solid)
228(42.3), 254(43.8), 315(7.5), 354
4.2), 377(2.8), 419(1.5) (THF)
27(9.8), 350(7.2), 375(4.6), 418
2.3) (acetone)
62, 314, 358, 429, 490–520 (solid)
)] (3) 221sh(19.2), 239(62.0), 278sh(27.4),
11(15.9), 340(8.2), 365(4.8), 413
2
[
{Pt(bzq)(C
6
6
F
5
5
)
2
2 n
} Ag] (2)
(
3
(
2
[{Pt(bzq)(C
F
)
2
}Ag(PPh
3
3
b
2 2
(3.4) (CH Cl )
2
2
3
22(57.4), 241sh(48.0), 256(42.6),
79sh(15.4), 303(10.3), 344(5.2),
89(2.6), 423(1.1) (acetonitrile)
b
[
{Pt(bzq)(C
6
F
5
2
) }Ag(tht)] (4)
228(42.1), 253(42.4), 293(15.2), 352
5.2), 378(3.4), 405(2.8) (CH Cl
29(50.4), 254(52.2), 316(13.5), 352
7.0), 378(4.9), 416(3.7) (THF)
29(8.9), 351(5.0), 373(4.0), 408
2.5) (acetone)
(
2
(
3
2
2
)
(
2
82(16.0), 315(14.4), 359(4.9), 380
(3.6), 421(2.8) (toluene)
2
58, 326, 360, 418, 480 (solid)
a
−5
b
Values taken from ref. 16 (5 × 10 M). Values taken from ref. 17
5 × 10− M).
5
(
the silver centre. Absorption spectra of diluted solutions of the
Pt–Ag complexes 2 (THF, acetone) and 4 (CH Cl , THF,
Fig. 4 a) View of the molecular structure of [{Pt(bzq)(C
6
F
)
5 2
}Ag(tht)
2
2
acetone, toluene) showed high-energy intraligand absorptions
range 215–373 nm) and a less intense band at 405–421 nm.
(
Me CO)] (4′). b) Supramolecular arrangement in pairs of 4′.
2
(
With reference to previous spectroscopic work on cycloplatinate
complexes and the theoretical calculations in binuclear com-
plexes [{Pt(bzq)(C F ) }Ag(PPh )] (3) and [{Pt(bzq)(C F ) }
Table 3 Selected bond lengths (Å) and angles (°) for [{Pt(bzq)
}Ag(tht)(Me CO)]·Me CO (4′·Me CO)
(C
6
F
5
)
2
2
2
2
6
5 2
3
6 5 2
Ag(tht)(acetone)] (4′) (see below), the low energy band is
Pt–C(7)
Pt–C(1)
Pt–Ag
Ag–S
2.006(3)
2.080(3)
2.721(1)
2.445(1)
Pt–C(23)
Pt–N
Ag–O(1)
Ag–C(23)
2.055(3)
2.091(3)
2.438(3)
2.463(3)
assigned to an admixture of metal-to-ligand [d (Pt)→π*(bzq)]
π
and ligand to ligand [Ar →bzq] charge transfer transitions
f
(
Fig. 5). This low-energy band, which follows the Beer–Lambert
−4
−5
law in a range of concentrations from 10 M to 10 M, is
C(7)–Pt–C(23)
C(23)–Pt–C(1)
C(23)–Pt–N
O(1)–Ag–S
S–Ag–C(23)
S–Ag–Pt
94.98(13)
176.37(12)
80.64(12)
102.00(8)
143.10(8)
144.95(3)
C(7)–Pt–C(1)
C(7)–Pt–N
C(1)–Pt–N
O(1)–Ag–C(23)
O(1)–Ag–Pt
87.88(13)
175.61(12)
96.48(12)
97.16(11)
110.09(7)
clearly blue-shifted in relation to the precursor 1 (ie, CH Cl ,
2
2
4
05 nm 4 vs. 425 nm 1; acetone, 418 2, 408 nm 4 vs. 422 nm 1;
THF, 419 nm 2, 416 nm 4 vs. 448 nm 1), confirming the persist-
ence of Pt–Ag bonds even in donor solvents. This observation
has been previously noted in related complexes such as 3 (λ
max
17
CH Cl 413 nm), [(N^N)PtR M](OTf) (N^N = ArNC(Me)C
2
2
2
2
1
4
6
(Me)NAr; Ar = 2,6-dichlorophenyl; M = Cu, Ag; R = Me, Ph)
or [{Pt(bzq)(C F ) }Cd(cyclen)]ClO (λ CH Cl 410 nm),
6
5 2
4
max
2
2
Electronic and luminescence spectroscopy
3
1
in which the presence of Pt–M bond was also supported by
P
1
1
19
The absorption and emission spectra of 2 and 4 are summarized
in Tables 4 and 5 and for comparative purposes some previously
published data of 1 and 3 are also included. As noted before, the
extended complex 2 is insoluble in CH Cl , so that the absorp-
{ H}, H or F NMR spectroscopy. In these systems, the
8
10
+
donation of electron density from Pt(d ) to a d ion (Ag or
Cd ) increases the electrophilicity of the Pt centre, lowering the
energy of the HOMO and, hence, increasing the gap of the
2+
2
2
1
tion spectra were registered in THF and in acetone, in which it is
assumed that the extended chain 2 dissolves as bimetallic frag-
ments [{Pt(bzq)(C F ) }AgS ] (S = solvent) with the donor
MLCT [5d(Pt)→π*(bzq)] absorption.
The solid state diffuse reflectance spectra of the extended
chain 2 display a distinctive low-energy feature (490–520 nm 2)
(Fig. S3†), which is slightly blue-shifted in 4 and is absent in the
6
5 2
n
solvent molecules completing the coordination environment of
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Table 5 Photophysic data for complexes 1–4 [solid state and glasses
−
5
(
5 × 10 M)]
Compound
(T/K)
λem/nm {Φ/%}
τ/μs
a
[
(
NBu
C F ) ] (1)
6 5 2
4
][Pt(bzq)
Solid
(298)
Solid
518
16.5
1
7
514, 550, 595sh
485, 521, 563,
(
77)
CH
77)
2
Cl
2
b
(
608sh
THF (77) 485, 522, 565,
c
6
11sh
[
(
{Pt(bzq)
C F ) } Ag] (2)
6 5 2 2 n
Solid
(298)
Solid
560 {6.1}
13.2
16.8
590
(
77)
THF (77) 495max, 530,
75sh
5
[
(
{Pt(bzq)(C
PPh )] (3)
3
6
7
F
5
)
2
}Ag Solid
(298)
491max, 523,
562sh {12.7}
12.4
1
+
Solid
487˙, 502 ,
12.4 (487 nm)
[∼278(45%),
∼13.6(55%)]
+
(77)
520˙, 540,
Fig. 5 Absorption spectra of 1, 2 and 4 in THF, 2 × 10−5 M at 298 K.
Inset: low-energy region.
+
d
5
85
CH
77)
2
Cl
2
495max, 530,
570, 625 sh
490max, 520,
560sh {27.8}
490max, 525,
565sh
(
[
{Pt(bzq)(C
tht)] (4)
6
F
5
)
2
}Ag Solid
(298)
27.9 (490)
(
Solid
35.1 (490)
[31.4(68%),
298 K; 35.1 μs, 77 K) in relation to 1, suggest that the contri-
(77)
3
bution of the MLCT to the emissive state decreases on going
9
8.2(32%)]
from 1 to 4. This hypothesis is consistent with the fact that the
formation of the Pt–Ag dative bond increases the electrophilicity
(525)
CH
77)
2
Cl
2
480max, 515,
553sh
3
(
of the Pt centre, raising the energy of the MLCT. While the life-
THF (77) 492max, 525,
65
time at the peak maxima fits to one component, at 77 K the
decay in the shoulder is composed of two components [τ = 31.4
5
a
b
2 2
Measured in KBr pellets at 298 K. CH Cl
5 × 10−5 M, 298 K: weak
(68%), 98.2 (32%) μs, (525 nm)], which indicates that the emis-
c
−5
band at 520 nm, λexc 365 nm. THF 5 × 10 M, 298 K: weak band at
d
sion still has some degree of mixed origin. Curiously, the behav-
iour of 4 in the solid state contrasts with that of the related PPh3
derivative 3. In this complex 3, the vibronic band with a λmax
5
25 nm, λexc 365 nm. Measurements in the low energy peak.
4
91 nm (Φ = 12.7%, τ = 12.4 μs) seen at 298 K is clearly
precursor. This band is tentatively assigned to an admixture of
Pt(bzq)→Ag] (LMM′CT) and [Ar →Ag] (L′M′CT), involving
the promotion of electron density from platinum fragments to the
silver centre.
resolved at 77 K into two close non-equilibrated structured
bands with different origins (487 and 502 nm, respectively) and
also distinct decays (see Table 5), which were tentatively
[
f
3
ascribed in our previous work to MLCT (or a mixed
3
3
17
The platinum precursor 1 exhibits in solid state at room temp-
LC/ MLCT) manifold. In this work, the nature of the low-
erature
a
broad unsymmetrical green phosphorescence
lying phosphorescent emission has been addressed by DFT cal-
culations. Inspection of the salient features of the SOMOs in the
(
(
∼518 nm), also detected as a weak broad emission in CH Cl2
∼520 nm) or THF (∼525 nm) solutions. Upon cooling to 77 K,
2
optimized T state for both complexes (see Theoretical section)
1
the spectra display a blue-shifted vibronic structured band (514
solid, 485 nm CH Cl or THF glasses), which according to
suggests that the emissions are mainly associated with charge
transfer from the metals and C F groups to the low lying benzo-
2
2
6 5
theoretical calculations, is mainly ascribed to an admixture of
quinolate group with some intraligand (bzq) character. Due to
the low contribution of the Ag to the SOMO (3% in 3 and 4% in
4′) we suggest that the emission comes mainly from an admix-
3
3
3
3
[
π→π*(bzq)] ( LC) and [5d(Pt)→π*(bzq)] ( MLCT) triplet
excited states (Fig. 6a, solid state).
3
3
Complexes 2–4 were only emissive in rigid media (solid and
glasses) (see Table 5). The lack of luminescence in solution
ture of MLCT/ L′LCT.
It is worth noting that despite the presence of short π⋯π con-
tacts between the bzq ligands of two adjacent monomers in com-
plexes 1, 3 and 4′ (∼3.6 Å in 1, 3.4–3.5 Å in 3 and 4′), leading
to final π⋯π stacked dimers, these interactions are not reflected
in the energy of their emissions, probably because they are not
of a long-range. By contrast, the presence of an extended met-
allic [–Pt–Ag–Pt–Ag–] chain in complex 2 is reflected in its
optical behaviour. In solid state, 2 exhibits a bright (ϕ = 6.1%)
orange emission (560 nm) with a mono exponential decay of
13.2 μs, revealing its triplet parentage. The emission is remark-
ably red-shifted in relation to the precursor (1, 518 nm) and also
3
could be attributed to the decreasing contribution of MLCT to
the excited state (see below). For comparative purposes, the
emission spectra of the precursor 1 and 4 are shown in Fig. 6.
As is shown in Fig. 6b, upon formation of the Pt–Ag bond, the
emission of 4 in solid state at 298 K becomes structured with a
λmax hypsochromically shifted (λmax 490 nm, Φ = 27.8%,
2
98 K, 77 K) in relation to the precursor, thus reflecting the
stabilization of the HOMO level. The clear vibronic appearance
of the emission at 298 K as well as the lack of rigidochromism
and the increasing of the lifetime on going to 77 K (τ = 27.9 μs,
3444 | Dalton Trans., 2012, 41, 3439–3451
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Fig. 7 Normalized excitation and emission spectra of 2 in solid state at
2
98 K (black) and at 77 K (grey) λexc 400 nm.
Theoretical calculations
The absorption and emission spectra of complexes 1–3 and 4′
were examined on the optimized geometries (for the S and T1
0
states) at the PBE1PBE/Def2-TZVP(M)∪6-31+G(d,p)(X) (M =
metal atom, X = non metal element) level in the gas phase. The
equilibrium geometries along with selected structural parameters
are shown in Fig. S4.† The optimized structural parameters of
1
–3 and 4′, in their S ground state, closely resemble the X-ray
0
structural analysis data. The higher deviation from the exper-
imental value of the Pt–Ag bond length in 2 (elongated by
0
.125 Å) could be due to the fact that the computed structural
parameter refers to an isolated building block of the polymeric
structure.
The absorption spectra of 1–3 and 4′ simulated with TD-DFT
calculations in the gas phase are depicted schematically in
Fig. 8. Selected TD-DFT singlet–singlet electronic transitions,
excitation energies and oscillator strengths are compiled in
Tables S4 and S5 (ESI†). Assignments on the electronic tran-
sitions, which are based on the nature of the molecular orbitals
(Fig. S5–S8†) and electron density difference maps (EDDM)
(Fig. S9†) are summarized in Tables S6–S9.†
According to the shapes of the MOs involved in the tran-
sitions (Fig. 9) as well as the respective EDDM (Fig. S9†) and
%CT values (Table S4†), the high energy bands for the anionic
precursor 1 (245–307 nm) possess a complex set of electronic
Fig. 6 Normalized emission spectra of 1 (a) and 4 (b) in solid state at
98 K and at 77 K (λexc 400 nm).
2
upon cooling at 77 K (590 nm 2) pointing to the involvement of
Pt–Ag bonds and Ag orbitals in the excited state (Fig. 7). The
excitation profile with a low-energy peak at ∼500 nm mimics the
solid reflectance diffuse spectrum (see Fig. S3†). According to
the contributions of the metals and ligands to the frontier orbitals
in the bimetallic fragment “[{Pt(bzq)(C F ) }Ag]” as model for
6
5 2
2
, we tentatively assign this emission to as arising from a mixed
3
3
LMM’CT [Pt(bzq)→Ag]/ L′M′CT [Ar →Ag] excited state
transitions (LC/L′LCT/MLCT; L = bzq, L′ = Ar
while the low intensity bands in the range of 330–406 nm are
mainly due to Pt→bzq and Ar →bzq charge transfer (MLCT/L′
f f 6 5
; Ar = C F ),
f
involving charge transfer from the platinum fragment to the
silver centre. The presence of an extended metallic chain stabil-
f
ized by the occurrence of both Pt–Ag and metallated carbon–
LCT). The low energy band calculated at 436 nm arises mainly
from the HOMO→LUMO (84%) excitation with the HOMO
+
silver [C (bzq)→Ag ] bonding interactions could raise and lower
π
the energies of the frontier orbitals HOMO and LUMO
respectively.
constructed from the out-of-phase combination of Pt(5dyz
(43%), bzq (46%) and Ar ligands (11%) and the LUMO located
on the bzq having therefore a remarkable MLCT character.
For discrete complexes 3 and 4′ having the cationic units Ag
(PPh ) and Ag(tht)(acetone), respectively, coordinated to the
)
f
Not surprisingly, complex 2 dissolves in THF giving non-
emissive pale-yellow solutions, probably formed by bimetallic
solvated fragments [{Pt(bzq)(C F ) }Ag(THF) ]. The spectra of
6
5 2
n
3
all three complexes 2–4 recorded in glassy (77 K) solution (2,
THF; 3, CH Cl ; 4, CH Cl , THF) display vibronic structures
anionic fragment 1 through a Pt–Ag bond, the frontier orbitals
(FMOs) are quite similar (Fig. 9). Thus, in both complexes the
HOMO−3 to HOMO are mainly composed of platinum AOs
2
2
2
2
with minor variations in their maxima, suggesting luminescence
3
from states exhibiting a primarily LC character.
overlapping with MOs located on both ligands (bzq, Ar
f
) with a
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Fig. 8 TD-DFT/PBE1PBE/Def2-TZVP(M)∪6-31+G(d,p)(X) simulated absorption spectra of complexes 1–3 and 4′ in gas phase.
Fig. 9 Frontier molecular orbital plots for 1–3 and 4′ along with their composition (%) in terms of ligands and metals obtained by DFT.
higher contribution from the MOs located on the Ar groups and
forming the Pt–Ag bond is the stabilization of the HOMO
decreasing the weight of the bzq (12–13% vs. 46% in 1) and the
Pt (∼28% 3, 30% 4′ vs. 43% in 1) orbitals and increasing the
orbital character of the electron-withdrawing C6F5 groups
(∼55% vs. 11% in 1). For both complexes, the two low-energy
absorptions (378, 402 nm 3; 393, 414 nm 4′) are primarily
associated with HOMO, HOMO−1 → LUMO transitions,
showing significant %CT values (see Table S5†) and are hence
f
just a marginal contribution of the AOs of Ag atom and the
LUMO and LUMO+1 correspond to π* MOs located on the bzq
ligand. However, while in 4 the LUMO+3 has bzq (∼ 64%) and
a metallic character (Pt 15%, Ag ∼11%) with a small contri-
bution of the tht ligand (6.7%), in complex 3 it has an essentially
high (93%) orbital character from the PPh ligand. Therefore, for
3
these complexes the main difference with the precursor 1 upon
3446 | Dalton Trans., 2012, 41, 3439–3451
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ascribed to admixture MLCT/L′LCT (L = bzq; L′ = Ar ). The
calculated values are comparable to the experimental values
However, as it has been noted before, in acetone or THF solution
complex 2 dissolves giving discrete bimetallic fragments [{Pt
(bzq)(C F ) }AgS ] (S = solvent) analogous to [{Pt(bzq)
f
(
365, 413 nm CH Cl 3; 373, 408 nm acetone 4) and are blue-
2 2
6
5 2
n
shifted in relation to 1 (calculated 406, 436 nm) in agreement
(C F ) }AgL] (L = PPh 3, tht 4). Therefore, for complex 2 in
6 5 2 3
with the experimental results. The remaining high-energy bands
solution the low energy bands are assigned, as in 3 and 4, to
admixture MLCT/L′LCT.
(240–360 nm 3, with peak maxima at 255, 297, 316 and
3
44 nm; 220–360 nm 4′, with peak maxima at 251, 282, 327
The lowest-energy emissions for complexes 1–3 and 4′, calcu-
lated as ΔET1–S0, occur at 554.2, 563.8, 484.9 and 467.5 nm
respectively, closely resembling with the experimentally
observed emission bands with maxima at 518, 560, 491 and
490 nm in the solid state emission spectra of 1–4 respectively.
The phosphorescent emission of 1–3 and 4′ can be associated
with the singly occupied molecular orbitals (SOMO) and SOMO
−1 of the optimized T1 state. The 3D contour plots of the
SOMO and SOMO−1 of complexes 1–3 and 4′ and their com-
position (% in terms of ligands and metals) are shown in Fig. 10.
For complex 1, the SOMO−1 is mainly contributed from bzq
(81.2%) and Pt (16.8%) centre, whereas the SOMO is located on
and 361 nm) arise from a multitude of excitations (electron
density difference maps and a detailed assignment of these latter
electronic transitions are shown in Fig. S9† and Table S5†).
Calculations on the monomeric building block [{Pt(bzq)
(C F ) }Ag] in 2 were performed as an adequate model for the
6 5 2
polymer 2. As can be seen in Fig. 9, Fig. S6† and Table S7,† the
formation of the Pt–Ag bond has a remarkable effect in the
nature of the frontier orbitals. Thus, the HOMO is mainly loca-
lized on the Pt (23%) and C F groups (73%) and the HOMO−1
and HOMO−2 also have a significant contribution from the Arf
groups, while the LUMO is located on the Ag metal (71%) and
has a small contribution from orbitals of Pt (11%) and bzq
6
5
3
the bzq (99%), pointing to a ligand-centred (bzq) LC character
3
(
17%). The calculated spectrum in gas phase (Fig. 8) shows an
intense band at 236 nm and several bands of medium intensity
270–350 nm), which are mainly ascribed to mixed LC/L′LCT/
mixed with MLCT contribution. For the bimetallic complexes 3
and 4′, the SOMO−1 resembles the HOMO of the ground state,
with contribution of Pt (24.2% 3, 29.3% 4′) and both ligands
(
MLCT character with some L′M′CT (Ar →Ag) (see Table S4 for
(bzq, Ar ) with a marginal contribution of the silver, whereas the
f
f
assignments†). The low-energy region 350–500 nm has two
peak maxima at 375 nm and 462 nm and a very low band (f =
SOMO is located on the bzq. Therefore, their emissions could be
3
3
primarily ascribed to a MLCT/ L′LCT manifold. For model 2,
given that the SOMO is located in both metals (Pt 16.8%, Ag
64%) whereas the SOMO−1 is distributed over the platinum
fragment with a remarkable contribution of the Arf rings
(52.5%), the emission can be assigned as an admixture of
0
.0007) at 495 nm. These bands are primarily associated with
transitions to the LUMO, which is mainly located on the Ag
atom: 375.4, HOMO−6 → LUMO (81%) and 380 nm, HOMO
−
5 → LUMO (84%); 462.2 nm, HOMO−2, HOMO−1 →
3
3
LUMO (82%); 495 nm HOMO−1 → LUMO (95%). The
HOMO−6 and HOMO−5 are constructed from AOs of the Pt
and MOs located on the bzq ligand and therefore the band at
[Pt(bzq)→Ag] ( LMM′CT) and Ar →Ag ( L′M′CT).
f
Conclusions
3
75 nm could be assigned as LMM′CT. However, the HOMO−2
to HOMO have a remarkable contribution from Pt and the Arf
ligands (52.5–73%) and the bands at 462 and 495 nm also
exhibit a remarkable L′M′CT character. In agreement with this,
the diffuse reflectance spectrum of the solid extended chain 2
exhibits a low energy feature from 490–520 nm (Fig. S3†),
which could tentatively be ascribed as an admixture of [Pt
To summarize, an unusual polymer metallic chain system [{Pt
(bzq)(C F ) }Ag] (2) and a series of bimetallic [{Pt(bzq)
6
5 2
n
(C F ) }AgL] complexes (3, 4) stabilized by short Pt–Ag
6
5 2
1
(2.75 Å) and η Ag⋯C(bzq) (∼ 2.45 Å) bonding interactions
have been constructed starting from the anionic [Pt(bzq)
−
(C F ) ] (1) building block. Their photophysical properties
6
5 2
(
bzq)→Ag] (LMM′CT) and [Ar →Ag] (L′M′CT) involving
(absorption and emission) have been studied and discussed with
theoretical calculations to obtain greater insight into the
f
charge transfer from the platinum fragments to the silver centres.
Fig. 10 3D contour plots of SOMO and SOMO−1 for 1–3 and 4′ involved in the emission process along with their composition (%) in terms of
ligands and metals obtained by DFT.
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8
10
3
3
3
influence of d –d metallophilic bonds on the nature of the elec-
tronic transitions.
J
= 8.0 Hz, J
= 0.8 Hz), 8.4 (H2, d, J
=
H(4),H(3)
3
H(4),H(2)
H(2),H(3)
3
5.2 Hz, J
= 28 Hz), 7.7 (H5, d, J
= 8.0 Hz, J
JH(6),H(5) = 8.8 Hz), 7.5 (H7, dd, J
= 8.8 Hz), 7.6
= 5.2 Hz), 7.6 (H6, d,
H(2),Pt
3
H(3),H(4)
H(5),H(6)
3
For complexes 3 and 4 (and also for 2 upon solution in donor
solvents as acetone or THF) the formation of the Pt–Ag bond
produces a significant blue shift of the lowest-lying absorption in
relation to 1. This fact has been attributed to the stabilization and
modification of the nature of the HOMO, which changes the
character of the transition from LC/ MLCT in 1 to admixture
L′LCT/ MLCT with a lower weight of the MLCT in the bi-
metallic fragments. The emission in 3 and 4 is also mainly
associated with an admixture of MLCT/ L′LCT, only slightly
modified by the Ag centre. By contrast, both the experimental
data in solid state and the theoretical calculations on “[{Pt(bzq)
C F ) }Ag]” as the model for 2 suggest that excitation of the
polymer moves electron density from the platinum fragments,
the C F rings having a remarkable contribution to an orbital
(H3, dd, J
H(3),H(2)
3
3
3
= 8.0 Hz, J
H(7),H(8)
H(7),H(9)
3
3
= 0.8 Hz), 7.2 (H8, dd, J
7.2 (H9, dd, J
= 8.0 Hz, J
= 6.0 Hz),
H(8),H(7)
H(8),H(9)
3
3
3
= 6.0 Hz, J
= 0.8 Hz, J
=
=
=
H(9),H(8)
H(9),H(7)
H(9),Pt
3
F,F
1
9
34 Hz). F NMR (acetone-d , 295 K), δ −114.1 (o-F, d, J
6
1
1
3
3
3
28 Hz, J = 552 Hz), −117.0 (o-F, d, J = 28 Hz, J
F,Pt
F,F
F,Pt
1
1
1
3
320 Hz), −165.2 (p-F, t, J = 20 Hz), −165.7 (m-F, br m),
F,F
3 19
F,F
−166.5 (p-F, t, J = 20 Hz), −166.7 (m-F, br m). F NMR
3
3
3
(acetone-d , 183 K), δ −113.8 (o-F, br s, JF,Pt = 426 Hz),
6
3
3
−117.0 (o-F, br s, J
= 207 Hz), −164.4 (p-F, t, J = 30
F,Pt
F,F
3
Hz), −164.9 (m-F, br m), −165.6 (p-F, t, J = 30 Hz), −165.9
F,F
195
1
(
(m-F, br m). Pt{ H} NMR (acetone-d , 295 K), δ −3330 [Pt,
6
5 2
6
m]; (acetone-d , 253 K), δ −3353 [Pt, m].
6
6
5
with a strong Pt, Ag metallic character. Absorption and emission
of the polymer in the solid state is therefore suggested to be
associated with an electronic transition of a mixed [Pt
Preparation of [{Pt(bzq)(C
6 5 2 3
F ) }Ag(PPh )] (3)
This complex has now been obtained by a different method to
17
(
bzq)→Ag]/[Ar →Ag] character.
that previously reported. To a yellow suspension of 2 (0.100 g,
f
0
0
.123 mmol) in CH Cl (10 mL), PPh was added (0.032 g,
2 2 3
.123 mmol). After 30 min of stirring in absence of light, the
Experimental
solution was evaporated to dryness. The residue was treated with
n-hexane, filtered off and finally air-dried, 0.104 g, 79% yield.
Anal. Found (calcd for C H AgF NPPt), C 47.66 (47.91); H
General comments
43
23
10
−1
Literature methods were used to prepare the starting material
2
.26 (2.15); N 1.37 (1.30). IR (Nujol): IR (cm ): 1632 (w),
1
6
(
NBu )[Pt(bzq)(C F ) ] (1). C, H and N analyses, mass, con-
4 6 5 2
1500 (s), 1098 (m), 1060 (s), 1044 (m), 955 (s), 836 (m), 821
88
ductivity, IR and NMR spectra were performed as described
(w), 801 (m, C F , X-sensitive vibr.), 777 (m, C F , X-sensi-
6 5 6 5
16
88
1
19
elsewhere. Diffuse reflectance UV-vis (DRUV) data of pressed
powder were recorded on a Shimadzu UV-3600 spectropho-
tometer with a Harrick Praying Mantis accessory and recalcu-
lated following the Kubelka–Munk function. The optical
absorption spectra were recorded using a Hewlett Packard 8453
tive vibr.), 742 (s), 692 (s), 522 (m), 505 (m). IR and H,
F
Pt
31
1
195
and P{ H} NMR agree with those described in ref. 17.
1
{
H} NMR (CDCl , 233 K), δ −3507 [Pt, m].
3
Preparation of [{Pt(bzq)(C F ) }Ag(tht)] (4)
6
5 2
(solution) spectrophotometer in the visible and near-UV ranges.
Emission and excitation spectra were obtained on a Jobin-Ybon
Horiba Fluorolog 3-11 Tau-3 spectrofluorimeter and the lifetimes
were measured operating in the phosphorimeter mode with a F1-
To a yellow suspension of 2 (0.242 g, 0.297 mmol) in CH Cl2
2
(5 mL), tht was added (26.2 μL, 0.297 mmol). After 1 h of stir-
ring in absence of light the solution was evaporated to dryness.
The residue was treated with ether, filtered off and finally air-
dried, 0.181 g, 68% yield. Anal. Found (calcd for
C H AgF NPtS), C 38.11 (38.54); H 1.15 (1.79); N 1.65
1
029 lifetime emission PMT assembly, using a 450 W Xe lamp.
Quantum yields in the solid state were measured upon excitation
at 400 nm, using an F-3018 Integrating Sphere mounted on a
Fluorolog 3-11 Tau-3 spectrofluorimeter.
Safety note: Perchlorate salts of metal complexes with organic
ligands are potentially explosive. Only small amounts of material
should be prepared and these should be handled with great
caution.
2
9
16
10
−
1
(
8
1.55); S 3.43 (3.56). IR (cm ): 1630 (w), 955 (s), 884 (s, tht),
35 (m), 819 (w), 799 (m, C F , X-sensitive vibr.), 777 (m,
6 5
8
8
8
8
C F , X-sensitive vibr.), 756 (s), 672 (s), 620 (s), 515 (m). Λ
M
6
5
−
1
2
−1 1
(
8
acetone) = 22.2 Ω cm mol . H NMR (CDCl , 295 K), δ
.6 (H2, d, J
3
3
3
3
= 4.8 Hz, J
= 31 Hz), 8.3 (H4, d, J
H(2),H(3)
H(2),Pt
H
3
=
7.8 Hz), 7.7 (2 H, m), 7.6 (H6, d, J
= 9.0 Hz),
(
4),H(3)
H(6),H(5)
19
7
.4 (3 H, m), 3.0 (tht, s); 2.0 (tht, s). F NMR (CDCl , 295 K),
3
Preparation of [{Pt(bzq)(C F ) }Ag] (2)
6
5 2
n
3
3
δ −115.5 (o-F, d, J = 28 Hz, J = 539 Hz), −118.5 (o-F, d,
F,F
F,Pt
3
3
3
To a solution of AgClO4 (0.069 g, 0.336 mmol) in acetone
15 mL), (NBu )[Pt(bzq)(C F ) ] 1 (0.319 g, 0.336 mmol) was
JF,F = 28 Hz, J = 330 Hz), −162.4 (p-F, t, J = 20 Hz),
F,Pt
F,F
19
(
−163.6 (m-F+ p-F, br m), −164.6 (m-F, br m). F NMR
4
6 5 2
3 3
F,F
added. After 1 h of stirring in absence of light the solution was
(CDCl , 213 K), δ −115.5 (o-F, d, J = 19 Hz, J
= 540
F,Pt
3
3
3
evaporated to dryness. CH Cl (5 mL) was added and 2 crystal-
Hz), −118.4 (o-F, d, J = 28 Hz, J = 327 Hz), −162.1 (p-
2
2
F,F
F,Pt
3
lized. The yellow solid was filtered off, washed with cold
F, br s, J = 20 Hz), −163.2 (m-F+ p-F, br m), −164.0 (m-F, br
F,F
195 1
CH Cl2 (3 × 1 mL) and vacuum-dried, 0.209 g, 76% yield.
m). Pt{ H} NMR (CDCl , 253 K), δ −3509 [Pt, m].
2
3
Anal. Found (calcd for C H AgF NPt): C, 36.42 (36.81); H,
2
5
8
10
−
1
0
.85 (0.99); N, 1.83 (1.79). IR (cm ): 1634 (w), 1507 (s), 1061
6 5 2 n
Reaction of [{Pt(bzq)(C F ) }Ag] (2) with py
(
s), 954 (s), 835 (s), 819 (w), 802 (s), 784 (m, C F , X-sensitive
6
5
88
88
vibr.), 766 (m, C F , X-sensitive vibr.). ΛM (acetone) = 37.5
Ω
To a yellow suspension of 2 (0.100 g, 0.123 mmol) in CH Cl2
6
5
2
−1
2
−1 1
cm mol . H NMR (acetone-d , 295 K), δ 8.6 (H4, dd,
(5 mL), pyridine was added (10 μL, 0.123 mmol). After 1 h of
6
3448 | Dalton Trans., 2012, 41, 3439–3451
This journal is © The Royal Society of Chemistry 2012

View Article Online
stirring in absence of light the solution was evaporated to
dryness. The residue was treated with ether, filtered off and
finally air-dried (0.072 g). The solid is a mixture of complexes,
Computational details
The geometries of all stationary points were fully optimized,
without symmetry constraints, employing the 1997 hybrid func-
tional of Perdew, Burke and Ernzerhof as implemented in the
one of which was identified (X-ray) as [Pt(bzq)(C F )(py)] (5).
6
5
93
94
Gaussian03 program suite. This functional uses 25% exchange
and 75% correlation weighting and is denoted as PBE0. For the
geometry optimizations we have used the Def2-TZVP basis set
for Pt and Ag metal atoms and the 6-31+G(d,p) for all other non
metal atoms. Hereafter the method used in DFT calculations is
abbreviated as PBE0/Def2-TZVP(M)∪6-31+G(d,p)(X) (M =
metal atom, X = non-metal element). All stationary points have
been identified as minima (number of imaginary frequencies
NImag = 0).
Gas-phase time-dependent DFT (TD-DFT) calculations of the
lowest 50 singlet–singlet excitations were performed at the
PBE0/Def2-TZVP(M)∪6-31+G(d,p)(X) level, using the S0
ground state geometries of complexes 1–3 and 4′ as obtained
from the optimizations at the same level of theory in order to
simulate the absorption spectra of these species. The unrestricted
X-ray structure determinations
Crystal data and other details of the structure analyses are pre-
sented in Table 6 (full data for the X-ray analyses of 3 and 5 are
presented in the ESI, Table S1†). Suitable crystals for X-ray dif-
fraction studies were obtained by slow diffusion of n-hexane into
concentrated solutions of the complexes in 3 mL of Me CO.
Crystals were mounted at the end of a quartz fibre. The radiation
used in all cases was graphite monochromated MoKα (λ =
2
0
.71073 Å). For 4′·Me CO, X-ray intensity data were collected
2
on a Bruker Smart Apex diffractometer. The diffraction frames
were integrated using the SAINT program and the reflections
8
9
9
0
corrected from absorption with SADABS. For the rest of the
structures, X-ray intensity data were collected on an Oxford Dif-
fraction Xcalibur diffractometer. The diffraction frames were
integrated and corrected from absorption by using the CrysAlis
uPBE0 was used to optimize the lowest triplet state (T ) for com-
1
plexes 1–3 and 4′ for the investigation of the nature of the emis-
sive state. The calculated emission maxima were estimated from
the differences between the triplet- and ground-state energies at
their corresponding equilibrium geometries. All TD-DFT calcu-
lations were performed using the Gaussian03 suite of
91
RED program. The structures were solved by Patterson and
2
Fourier methods and refined by full-matrix least squares on F
92
with SHELXL-97. All non-hydrogen atoms were assigned ani-
sotropic displacement parameters and refined without positional
constraints, except as noted below. All hydrogen atoms were
constrained to idealized geometries and assigned isotropic dis-
placement parameters equal to 1.2 times the Uiso values of their
attached parent atoms (1.5 times for the methyl hydrogen
atoms). Full-matrix least-squares refinement of these models
94
programs.
Acknowledgements
This work was supported by the Spanish MICINN (DGPTC/
FEDER) (Project CTQ2008-06669-C02-01,02/BQU). S. Ibáñez
2
against F converged to final residual indices given in Table 6.
Table 6 Crystal data and structure refinement for complexes [NBu
Me CO)]·Me CO (4′·Me CO)
4 6 5 2 6 5 2 n 6 5 2
][Pt(bzq)(C F ) ] (1), [{Pt(bzq)(C F ) }Ag] (2), and [{Pt(bzq)(C F ) }Ag(tht)
(
2
2
2
1
2
4′·Me
2
CO
Formula
C
41
H
44
F
10
N
2
Pt
(C25
H
8
AgF10NPt)
n
C
33
H
22AgF10NOPtS·Me CO
2
M
t
949.87
Triclinic
P1ˉ
815.28
Tetragonal
I4 /a
1019.60
Triclinic
P1ˉ
Crystal system
Space group
1
a/Å
b/Å
c/Å
α/°
β/°
γ/°
V/Å
9.8757(3)
25.8768(3)
25.8768(3)
18.5465(2)
90
90
90
12418.9(3)
16
1.744
11.0879(14)
12.7152(17)
13.3809(18)
80.369(2)
76.834(2)
68.048(2)
1696.7(4)
2
11.6449(3)
18.5109(5)
100.069(2
98.845(2)
114.516(2)
1845.17(9)
2
3
Z
D
/g cm−
3
1.710
1.996
c
T/K
μ/mm
100(1)
3.886
123(1)
5.203
100(1)
3.658
−1
F(000)
θ range/°
Collected reflections
Unique reflections
944
7.4–50.0
19190
6080
8.3–51.0
39290
984
3.2–50.0
9235
2
6451
5732
5887
R
R
R
int
0.0276
0.0656
0.0556, 0.1481
0.0871, 0.1546
1.006
0.0124
a
a
2
1
, wR
, wR
2
2
(I > 2σ(I))
(ball data)
0.0262, 0.0675
0.0312, 0.0688
1.076
0.0215, 0.0535
0.0225, 0.0540
1.041
1
GOF (F )
a
2
o
2 2
2 2 1/2
b
2
o
2 2
1/2
R
1
o
= ∑(|F | − |F
c o
|)/∑ |F |. wR
2
= [∑w(F
− F
c
) /∑w(F
o
) ]
.
Goodness-of-fit = [∑w(F
− F
c
) /(nobs − nparam)]
.
This journal is © The Royal Society of Chemistry 2012
Dalton Trans., 2012, 41, 3439–3451 | 3449

View Article Online
thanks the Ministerio de Eduación
y
Ciencia for
a
34 E. Alonso, J. Forniés, C. Fortuño, A. Martín and A. G. Orpen, Organo-
metallics, 2003, 22, 5011.
grant. A. C. T. thanks the University of Ioannina for a sabbatical
leave and all colleagues at the Departamento de Química Inorgá-
nica, Instituto de Ciencia de Materiales de Aragón, Facultad de
Ciencias, Universidad de Zaragoza-CSIC, Zaragoza (Spain) for
their generous hospitality. In particular I want to single out my
host Professor Juan Forniés for his hospitality and support
during this sabbatical leave.
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