Synthesis and photophysical properties of a series of biscyclometalated platinum(II) complexes on the basis of a tridentate 2,6-diphenylpyridine

Article abstract of DOI:10.1023/B:RUGC.0000025140.64970.10

The complexes C,C-trans-[Pt(C∧N∧C)L]^z [C∧N∧C is bisdeprotonated 2,6-diphenylpyridinate (dppy^2-); L = CO, Me2SO (dmso), ethylenediamine (en), CN^-, pyrazine (pz), P(C ₆F₅)₃, 4,4′-bipyridine (4,4′-bpy)] were synthesized and characterized by ¹H NMR, electronic, and emission spectroscopy. Spectralluminescence properties of the chromophoric group (platinum-cyclometalating ligand) in the C,C-trans-bis-cyclometalated complexes depend on the nature of the noncyclometalating ligand L, which is explained by its donor-acceptor effects on the form of existence of the complex in solution.

Full text of DOI:10.1023/B:RUGC.0000025140.64970.10

Russian Journal of General Chemistry, Vol. 73, No. 12, 2003, pp. 1839 1845. Translated from Zhurnal Obshchei Khimii, Vol. 73, No. 12, 2003,
pp. 1942 1949.
Original Russian Text Copyright
2003 by Kulikova, Balashev, Erzin.
Synthesis and Photophysical Properties of a Series
of Biscyclometalated Platinum(II) Complexes on the Basis
of a Tridentate 2,6-Diphenylpyridine
M. V. Kulikova, K. P. Balashev, and Kh. Erzin
Gertsen Russian State Pedagogical University, St. Petersburg, Russia
Received November 26, 2002
Abstract The complexes C,C-trans-[Pt(C^N^C)L]z [C^N^C is bisdeprotonated 2,6-diphenylpyridinate
(dppy2 ); L = CO, Me2SO (dmso), ethylenediamine (en), CN , pyrazine (pz), P(C6F5)3, 4,4 -bipyridine (4,4 -
bpy)] were synthesized and characterized by 1H NMR, electronic, and emission spectroscopy. Spectral-
luminescence properties of the chromophoric group (platinum cyclometalating ligand) in the C,C-trans-bis-
cyclometalated complexes depend on the nature of the noncyclometalating ligand L, which is explained by
its donor acceptor effects on the form of existence of the complex in solution.
Cyclometalated complexes of Pt(II), Pd(II), and
Ru(II) with tridentate ligands, containing one acti-
vated C H bond, are well documented. Such com-
plexes are formed by N^C^N [1], P^C^P [2 5],
S^C^S [6], or C^N^N [7 11] coordination of cyclo-
metalating ligands. However, only a few C,C-trans-
biscyclometalated complexes with two activated C H
bonds are known, among them Pt(II) and Pd(II) com-
plexes with C^P^C,P [12] [unstable with respect to
isomerization into (P^C)2] and C^N^C [13 16]
coordination of the cyclometalating ligand.
Pd(II)] at 10 C in the same solvent. Finally, after
repeated chromatographic purification, the yields of
[Pt(C^N^C)SEt2] complexes were as low as 10%,
whereas the yields of the corresponding palladium
complexes were about 2%. Cave et al. [15] proposed
another, much more effective synthetic procedure for
such complexes. In the present work we made use of
this procedure to prepare the complex [Pt(dppy)dmso]
which proved to be a convenient starting compound
for preparing other [Pt(dppy)L] complexes (see the
scheme below).
In view of the fact that at present there is a great
deal of information on optical and photophysical
properties of [M(C^N)XY]z monocyclometalated
complexes [17, 18] and C,C-cis-biscyclometalated
complexes of the [M(C^N)2] type [M = Pt(II), Pd(II),
C^N cyclometalating ligand on the basis of 2-(2 -
thienyl)pyridine, 2-phenylpyridine, benzo(h)quinoline,
etc.] [19 21], of considerable interest is to study
photophysical properties of C,C-trans-biscyclome-
talated compounds with tridentate ligads, such as
2,6-diphenylpyridine (H2dppy), an analog of 2,2 :6 ,2 -
terpyridine (N^N^N) but having two donor carbon
atoms. In this connection in the present work we took
the example of C,C-trans-[Pt(C^N^C)L]z complexes
to study the effect of donor acceptor properties of the
ligand L on photophysical properties of the [Pt(dppy)]
chromophoric group.
The first cyclometalation (formation of the dimeric
complex [Pt(Hdppy)( -Cl)]2) was accomplished by
refluxing 2,6-diphenylpyridine and K2PtCl4 in glacial
acetic acid. At the same time, as shown in [16], the
driving force of the second cyclometalation is the
possibility of ionization of the by-product HCl. There-
fore, by using a polar solvent mixture (dmso/H2O)
we could fairly readily convert the monocyclometa-
lated product into biscyclometalated. The subsequent
substitution of the dimethyl sulfoxide ligand by
various ligands L occurs in mild conditions in CH2Cl2,
resulting in quantitative formation of the complexes
[Pt(dppy)L], except for [Pt(dppy)pz] whose yield is as
low as 10%.
1
Principal parameters of the H NMR spectra of the
resulting complexes are listed in Table 1.
1
The first synthetic approach to C,C-trans-biscyclo-
metalated complexes [13] involved reaction of organo-
lithium reagents (for example, BuLi) with a C^N^C-
cyclometalating ligand at 5 C in diethyl ether fol-
lowed by reaction with M(SEt2)2Cl2 [M = Pt(II),
The H NMR spectra of the complexes contain six
signals of the 2,6-diphenylpyridine ligand (integral
intensity 11H), which points to equivalence of res-
pective phenyl ring protons and provides evidence for
tridentate coordination of 2,6-diphenylpyridine in
1070-3632/03/7312-1839$25.00 2003 MAIK Nauka/Interperiodica

1840
KULIKOVA et al.
N
Pt
Pt
N
K2PtCl4
Cl
Cl
H2dppy
N
dmso
4
3
5
6
6
3
5
5
4
N
L
N
4
3
Pt
Pt
S
L
H3C
O
CH3
L = CO, CN , en, P(C6F5)3, pz, 4,4 -bpy.
solutions at room temperature. The
=
conclusion was obtained by single-crystal X-ray
analysis of [Pt(dppy)pz] (Fig. 1). The asymmetric unit
of the crystal contains four molecules. The mean
torsion angle of the pyrazine ring is 59.4 . Because
of this position, the pz ligand can exhibit no other but
donor properties. The [Pt(dppy)dmso] and [Pt(dppy)
CO] complexes contain in their asymmetric units
respectively three and two molecules that differ from
each other to a lesser extent than in [Pt(dppy)pz]. The
complexes all have a distorted square-planar geometry.
The C1PtC17 angle is 160.2 in the dmso and CO
complexes and 161.5 in the pz complex. Such distor-
tion is characteristic of Pt(II) complexes with tri-
dentate ligands [14, 22 25].
comp
lig
(Table 1) values for the H5 ,5 and H6 ,6 phenyl ring
protons, as well as for pyridine ring protons which
are less sensitive to the anisotropic effect of L, point
to a considerable concentration of electron density on
the dppy ligand. Probably, for this reason a similar
complex with the donor chloride ligand could not
be obtained.
We failed to reveal any trend in variation of the
values of the H3 ,3 protons with donor acceptor
properties of L, since these values are much more
contributed by steric rather than electronic factors.
Thus, the
value for the complex with dmso is
0.29 ppm, whereas the respective values for the com-
plexes with the CO, 4,4 -bpy, pz, and P(C6F5)3 ligands
which are potentially much stronger -acceptors
decrease along this series of ligands (0.04, 0.56,
0.68, and 0.76 ppm). The anisotropic effect of one
of the phenyl rings of the phosphine ligand, which is
orthogonal to the other rings, we observed earlier [17]
in [Pt(tpy)Cl(PZ3)] complexes [tpy is 2-(2 -thienyl)-
pyridinate and PZ3 is phosphine].
A characteristic feature of a tridetate 2,6-diphenyl-
pyridine ligand is that its Pt C bond is elongated
[mean value 2.07(2) ] because of the trans-effect of
carbon atoms on each other and the Pt Npyridine bond
[mean value 1.99(7) ] compared with those in a
bidentate (C^N,C) 2,6-diphenylpyridine ligand (Pt C
and Pt Npyridine bond lengths 1.970 and 2.074
,
respectively [16]) and in some other monocyclome-
talated complexes [Pt(C^N)XY]z. The longest Pt N
bond (2.018 ) is observed in [Pt(dppy)CO], which is
consistent with the fact that CO is a much stronger
trans-activator than dmso and pz. Moreover, very
important, in terms of the possible effect on the
photophysical properties, is that the Pt C1 and Pt C17
bonds have different lengths [mean values 2.05(1) and
2.08(5) , respectively] in [Pt(dppy)pz] and equal
The equivalence of the H3 and H3 protons, which
1
reveals itself in the H NMR spectrum of [Pt(dppy)P
(C6F5)3], suggests that here already two phenyl sub-
stituents of the phosphine ligand exhibit anisotropic
effect. The pyrazine and 4,4 -bipyridine ligands can
shield H3 and H3 only if their rings are turned with
respect to the dppy plane. Direct evidence for this
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SYNTHESIS AND PHOTOPHYSICAL PROPERTIES OF A SERIES
1841
1
1
Table 1. Chemical shifts ( , ppm, relative TMS) and H 1H and 195Pt 1H coupling constants (J, Hz) in the H NMR
spectra of [Pt(dppy)L] complexes
Atom
Compound
L
(solvent)
H3 ,3
H4 ,4
H5 ,5
H6 ,6
H3
H4
H5
H2dppypa
(CD3CN)
7.52
(3J 7.4,
7.6)
7.46
(3J 7.5,
7.0)
7.52
(3J 7.4,
7.6)
8.18
7.79
7.88
7.79
(3J 7.8)
(3J 7.8)
(3J 8.1, (3J 7.8)
7.5)
(3J 7.8)
[Pt(dppy)dmso]
(CDCl3)
7.81
7.28
7.12
7.30
7.48
7.62
7.48
3.69 (CH3,
(3J 7.2,
(3J 7.3)
(3J 7.2)
(3J 8.0)
(3J 8.2)
(3J 8.0)
3JPtH 26.8)
3JPtH 22.8)
[Pt(dppy)CO]
(CD2Cl2)
7.56
(3J 7.4,
4J 1.4,
7.19
7.10
7.41
(3J 7.3,
4J 1.1)
7.21
7.59
7.21
(3J 7.3,
4J 1.5)
(3J 7.5,
4J 1.5)
(3J 7.8)
(3J 8.0) (3J 7.8)
3JPtH 33.5)
(Bu4N)
[Pt(dppy)CN]
(CD2Cl2)
7.90
7.13
6.99
7.39
7.23
7.53
7.23
3.07 (CH2N),
1.41 quintet
(3J 7.1,
4J 1.5,
(3J 7.2, (3J 7.7, 7.4, (3J 7.8)
(3J 7.8)
(3J 7.8) (3J 7.8) (CH2), 1.22 sextet
4J 1.2)
4J 1.5)
(CH2), 0.85 t
(CH3)
3JPtH 34.2)
[Pt(dppy)En]
(CD2Cl2)
7.40
7.26
7.06
7.45
7.22
7.53
7.22
4.53 (NH2,
2
(3J 7.1 , (3J 7.2,
(3J 7.5,
4J 1.5)
(3J 7.7,
4J 1.2)
(3J 7.8)
(3J 7.5, (3J 7.8) JPtH 60.0),
4J 1.4,
4J 1.2)
8.4)
1.23
(NH2), 3.23
3JPtH 25.1)
3.15 m (CH2),
3.00 s (CH2)
[Pt(dppy)
(4,4 -bpy)]b
(CD2Cl2)
6.96
(3J 7.1,
4J 0.9,
7.19
7.06
7.48
7.29
7.58
7.29
(3J 7.2,
4J 1.2)
(3J 7.5,
4J 1.3)
(3J 7.6,
4J 0.8)
(3J 8.0)
(3J 8.0) (3J 8.0)
3JPtH 25.4)
[Pt(dppy)pz]c
(CDCl3)
6.84
7.3 7.17
7.06
7.45
7.3 7.17
7.54
7.3 7.17
7.31
(3J 7.2,
(3J 7.6)
(3J 7.4)
(3J 7.8)
3JPtH 24.4)
[Pt(dppy)
P(C6F5)3]d
(CDCl3)
6.76
(3J 7.0,
3JPtH 21.0)
e
6.95
7.04
7.46
7.31
7.62
(3J 7.0)
(3J 7.2)
(3J 7.5)
(3J 8.0)
(3J 7.9) (3J 8.0)
e
for
7.06 0.04 7.42 0.06 7.29 0.06 7.57 0.04 7.29 0.06
[Pt(dppy)L]
a
3
b
3
4
3
3
Other signals, , ppm (J, Hz): 8.18 ( J 7.8). Other signals, , ppm (J, Hz): 9.14 (H , J 5.2, J 1.6, J
43.4), 8.80 (H , J 4.4,
o
PtH
o
4
3
4
3
4
c
3
3
J 1.7), 7.72 (H , J 5.2, J 1.6), 7.67 (H , J 4.4, J 1.7). Other signals, , ppm (J, Hz): 9.04 (H , J 2.8,
J
46.8), 8.68
m
m
o
PtH
3
d 31
1
e
(H , J 2.8).
P NMR spectrum (CDCl ), , ppm (J, Hz): 27.13 ( J 4432). The mean
value is not given since it is
m
3
P
PtP
much contributed by the steric factor.
lengths in [Pt(dppy)dmso] and [Pt(dppy)CO]. In other
In the UV region of all the spectra, there is a strong
words, the latter two complexes are more symmetrical. structureless band at 270 280 nm and a strong struc-
tured band at 330 350 nm. The complexes with the
The electronic absorption spectra of [Pt(dppy)L]
complexes at room temperature are presented in
Table 2.
en, CN , pz, and 4,4 -bpy ligands which are primarily
electron donors give one more band at 310 nm. The
high molar absorption coefficients
(7000 38000)
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 73 No. 12 2003

1842
KULIKOVA et al.
N3
3
4
C21
C20
C19
C18
2
1
N2
Pt1
C16
C15
C2
2
C17
C1
C3
10
3
4
C13
2
C6
C14
1
C4
C5
C12
C11
C10
N1
C7
C8
250 300 350
400 450
500
, nm
C9
Fig. 2. Absorption spectra of (1) [Pt(dppy)CO],
(2) [Pt(dppy)dmso], (3) [Pt(dppy)pz], and (4) [Pt(dppy)
en] in CH Cl at 293 K.
Fig. 1. Molecular structure of the [Pt(dppy)pz] complex.
2
2
and the observation of similar bands in the spectra of
C,C-cis-[Pt(Hdppy)2] [14] and some other complexes
The most considerable differences are observed in
the visible region of the spectra (Fig. 2). Thus, the
spectra of the complexes with such -acceptor ligands
as dmso, P(C6F5)3, and CO, show at 400 470 nm a
weak finely structured band that is lacking in the spec-
trum of the free H2dppy ligand. Such low-energy
bands were observed in the spectra of C,C-cis-
with phenylpyridine ligands suggest that these bands
1
are formed by (
*) transitions in the dppy ligands.
Table 2. Electronic absorption spectra of [Pt(dppy)L]
complexes in methylene chloride
[Pt(Hdppy)2] (
402 nm,
2600) and C,C-cis-
max
1
Compound
H2dppya
max, nm ( 10 )
[Pt(ppy)2] (ppy is 2-phenylpyridinate) (
402 nm,
10500) [20], and they were assigned mtoax a metal
cyclometalating ligand charge-transfer transition. In
our case, too, the same assignment is possible.
Apparently, the stronger forbiddenness of such transi-
tion (as follows from the magnitude of the molar
245 (42.3), 285 (17.4), 305
(17.5)
[Pt(dppy)CO]
271 (26.7), 287 sh (21.4), 334
(13.8), 350 (12.6), 420 (0.49),
445 (0.50), 470 (0.32)
274 (34.9), 332 sh (14.5), 345
(15.7), 407 (0.71), 428 (0.70),
456 (0.35)
269 (18.2), 331 sh (6.3), 344
(7.2), 410 (0.25), 429 (0.27),
453 (0.16)
absorption coefficient,
< 1000) and its spectral
[Pt(dppy)dmso]
[Pt(dppy)P(C6F5)3]
[Pt(dppy)en]
region are specific of [Pt(C^N^C)L] complexes with
-acceptor ligands L which favor equivalent transfer
of electron density from the two carbon atoms of the
C^N^C ligand and its delocalization throughout the
tridentate ligand. The most rigid structure of the dppy
ligand is attained in [Pt(dppy)CO]. The low-energy
transition in [Pt(dppy)CO], [Pt(dppy)dmso], and
281 (37.6), 312 (8.9), 350 (8.6),
367 sh (7.1)
[Pt(dppy)P(C6F5)3] probably belongs to a 1(d *)/
3
*) mixed transition.
(Bu4N)[Pt(dppy)CN] 280 (19.3), 315 (4.1), 349 (4.6),
360 sh (4.1)
(
[Pt(dppy)pz]
275 (22.4), 306 sh (9.4),
334 sh (11.8), 348 (13.3),
360 sh (12.7), 392 sh (3.6)
Compared with the above-described complexes,
the complexes with purely donor (such as en), weakly
acceptor [such as pz and 4,4 -bpy (for steric reasons)],
and CN (donor properties prevail over acceptor)
[Pt(dppy)(4,4 -bpy)] 277 (22.4), 306 sh (6.3),
333 sh (6.2), 352 (7.7), 363 sh
(7.4), 410 sh (4.1)
ligands strongly absorb at 370 420 nm. This absorp-
*
tion might be assigned to a d
transition involving
the aromatic ligands pz and 4,4 -bpy. However, the
fact that the en and CN complexes, too, exhibit the
a
In C H OH.
2
5
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SYNTHESIS AND PHOTOPHYSICAL PROPERTIES OF A SERIES
1843
same absorption points to one more optical transition
in this spectral region. The absorption spectra of
previously described monocyclometalated complexes
[Pt(ppy)XY]z and [Pt(Hdppy)en]+ [18] and iso-
cyanide complexes like [Pt(C^N^N)C NR]+ on the
basis of the unsymmetrical tridentate 6-phenyl-2,2 -
bipyridine ligand [7] contain Pt cyclometalating
ligand charge-transfer bands at 381 9 and 395 5 nm,
respectively.
Table 3. Luminescent properties of [Pt(dppy)L] complexes
in freshly prepared solutions at 77 K (concentration
5
10 M)
Complex
max, nma
,
s
[Pt(dppy)CO]b
521
506
506
477
477
481
483
490
491
480
481
11
0.9
0.5
0.8
0.6
0.2
0.4
0.3
[Pt(dppy)dmso]b
[Pt(dppy)P(C6F5)3]b
[Pt(dppy)en]b
9
13
23
25
16
12
11
4
It can be proposed that the donor ability of the en,
CN, pz, and 4,4 -bpy ligands (whether it arises from
the very nature of the ligand or its geometric arrange-
(Bu4N)[Pt(dppy)CN]b
[Pt(dppy)pz]c
[Pt(dppy)(4,4 -bpy)]c
C,C-cis-[Pt(Hdppy)2]d
C,C-cis-[Pt(ppy)2]e
[Pt(Hdppy)en]+ f
[Pt(ppy)en]+ f
ment) prevents delocalization of electron density over
*
the dppy ligand, and low-lying
orbitals are only
partly localized on the C^N,C ligand. Indirect evi-
dence for this proposal are provided by the non-
equality of the Pt C1 and Pt C17 bond lengths in
[Pt(dppy)pz], revealed by X-ray diffraction analysis.
17
15
0.8
0.7
a
Position of the short-wave luminescence maximum.
c
1
b
d
However, the H NMR spectra of the complexes in
C H OH CH OH CH Cl , 4:1:1.
Butyronitrile.
e
2
5
3
2
2
hand at room temperature give no way of distinguish-
ing between symmetrical and unsymmetrical
molecular forms which can be in dynamic equilibrium
in solutions. The first example of such a dynamic
equilibrium in solutions is provided by palladium
complexes with a tridentate (N^N^N) 2,2 :6 ,2 -
terpyridine ligand. Ramdeehul et al. [26] have studied
Published data [14], CH OH C H OH, 1: 5. Published data
3 2 5
f
[21], butyronitrile. Published data [18], DMF toluene, 1:1.
luminescence maximum are similar to those of
[Pt(Hdppy)en]+ and [Pt(ppy)XY]z.
The luminescence excitation spectra at 77 K of
these complexes are similar to the absorption spectra
of monocyclometalated phenylpyridinate complexes,
and the shoulder at 360 nm for the pz and 4,4 -bpy
complexes is probably formed by charge-transfer
transitions involving the pz and 4,4 -bpy ligands.
Therefore, the lowest electronically excited state
1
variable-temperature H NMR spectra of such com-
plexes (188 298 K) to show that in methylene chlo-
ride at room temperature the dynamic equilibrium is
much shifted to the unsymmetrical form (the limiting
case is a bidentate mode of coordination of ter-
pyridine) as the temperature decreases, i.e. the un-
symmetrical form
symmetrical form transition is
(a)
(b)
I
endothermic. In our case, the tridentate ligand
contains two donor carbon atoms (C ), and the
dynamic equilibrium in solution can be affected not
only by the temperature, but also by the nature of the
ligand L.
1
1
2
2
Evidence for the proposed model of behavior of
C,C-trans-biscyclometalated complexes [Pt(dppy)L]
in solutions comes from their luminescent properties
(Table 3, Fig. 3). In solutions at 77 K all the com-
plexes show a structured luminescence bond which,
on the basis of the half-life and the long-wave shift
relative to the phosphorescence maximum of the free
ligand H2dppy, was assigned to the 3(d *) type.
However, like with the absorption spectra, the lowest
electronically excited state in one group of complexes
[CO, dmso, P(C6F5)3] is of the (d C^N^C) type, as
evidenced by the fact that their luminescence band
shapes are similar to those of C,C-cis-[Pt(Hdppy)2].
In the other group of complexes (en, CN , pz, 4,4 -
bpy), the position and shape of the short-wave
(a)
(b)
4
3
4
3
250 300 350 400 450 500 550 600 650
, nm
3
*
Fig. 3. (a) Excitation and (b) luminescence spectra of
(1) (Bu N)[Pt(dppy)CN], (2) [Pt(dppy)pz], (3) [Pt(dppy)
dmso], and (4) [Pt(dppy)CO] in solutions at 77 K.
4
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1844
KULIKOVA et al.
responsible for luminescence of second-group
and dried in a vacuum, yield 40%. IR spectrum:
(SO) 1115 cm .
1
complexes can be assigned to the 3(d C^N,C) type.
Complex [Pt(dppy)CO]. Carbon monoxide was
passed through a solution of 20 mg of [Pt(dppy)dmso]
in 2 3 ml of CH2Cl2 for 30 min. The solution quickly
got orange, and needle-like crystals formed. They
were washed with a minimum of cold CH2Cl2 and
dried in a vacuum, yield 98%. IR spectrum: (CO)
2044 cm . The sample for X-ray diffraction analysis
was obtained by slowly diffusing pentane vapors into
a solution of the complex in methylene chloride.
The results of investigation of the luminescent
properties of the complexes show that the strongest
temperature effect on the dynamic equilibrium
between the symmetrical and unsymmetrical forms of
[Pt(dppy)L] complexes in solutions is observed when
the ligands L are primarily electron donors. However,
whether this process involves cleavage of one of the
Pt C bonds (limiting case of the unsymmetrical form)
1
1
can be found out by a combined study of the H and
13C NMR and luminescence spectra of the complexes
at various temperatures.
Complex [Pt(dppy)pz]. Pyrazine, 14 mg, was
added to a solution of 45 mg of [Pt(dppy)dmso] in
5 6 ml of CH2Cl2, and the mixture was stirred for
30 min. Hexane, 1 2 ml, was then added. Methylene
chloride was slowly evaporated. The complex pre-
cipitated as orange crystals, as well as a dark red
substance unidentified because of the poor solubility.
The crystals were separated by hand, washed with
hexane, and dried in a vacuum, yield 10%.
Thus, using the example of C,C-trans-[Pt(dppy)L]
complexes with a tridentate cyclometalating ligand
we showed that the form of their existence in solu-
tions and, as a consequence, photophysical properties
of the platinum cyclometalating ligand chromophore
are much affected by the donor acceptor ability of the
noncyclometalating ligand L. Such an effect we did
not previously observed in monocyclometalated
complexes like [Pt(C^N)XY]z [17].
Complex [Pt(dppy)(4,4 -bpy)]. 4,4 -Bipyridine,
20 mg, was added to a solution of 60 mg of [Pt(dppy)
dmso] in 10 ml in CH2Cl2, and the mixture was
stirred for 30 min. Hexane was then added dropwise
to the reaction mixture until crystallization began.
Methylene chloride was slowly evaporated. Orange
fine crystals formed and were filtered off, washed
with hexane and ethanol, and dried in a vacuum, yield
98%.
EXPERIMENTAL
1
The H and 31P NMR spectra were obtained on a
Bruker AC-250 spectrometer at 298 K. The structure
of the [Pt(dppy)dmso], [Pt(dppy)CO], and [Pt(dppy)pz]
complexes we determined on a STOE-IPDS diffrac-
tometer (University of Regensburg, Germany). The
electronic absorption spectra were measured on
Kontron Uvikon-860 and SF-121 spectrophotometers.
The luminescence spectra were obtained on a Spex-
Jobin Yvon-Fluoromax-2 fluorimeter and a KSVU-1
Complex (Bu4N)[Pt(dppy)CN]. To a solution of
36 mg of [Pt(dppy)dmso] in 5 6 ml of CH2Cl2 we
added 21 mg of (Bu4N)CN. The mixture was stirred
at room temperature for 20 min. Equal volume of
water was then added, the mixture was vigorously
stirred for 1 2 min, and the upper (aqueous) layer was
decanted. The washing operation was repeated 3 times.
The methylene chloride solution was filtered, and the
filtrate was diluted with equal volume of hexane.
Yellowish orange fine crystals formed and were
washed with hexane and dried in a vacuum, yield 92%.
setup (LGI-21 pulse nitrogen laser,
337 nm,
pulse
10 ns). The IR spectra were taken oneax Perkin Elmer-
200 spectrophotometer in KBr.
Complex [Pt(dppy)dmso] was prepared by a
modified procedure [15]: 600 mg of K2PtCl4 was
added to a warm solution of 334 mg of 2,6-diphenyl-
pyridine in 250 ml of glacial acetic acid. The reaction
mixture was stirred at 80 C for 7 days. The yellow
precipitate that formed was filtered off, washed with
water, acetone, diethyl ether, and dried in a vacuum.
The dry reaction product was dissoled in 1 2 ml of a
hot dimethyl sulfoxide, cooled to room temperature,
and diluted by half with water. The presipitate was
filtered off, washed with water, and treated with
CH2Cl2. The extract was subjected to chromatography
on Al2O3 (eluent CH2Cl2), and the eluate was duluted
with hexane until crystallization began. The solvent
was slowly evaporated to leave a yellowish orange
material which was filtered off, washed with hexane,
1
IR spectrum: (CN) 2093 cm .
Complex [Pt(dppy)en]. Ethylenediamine, 1 drop,
was added to a solution of 30 mg of [Pt(dppy)dmso]
in 5 6 ml of CH2Cl2, and the mixture was stirred at
room temperature for 30 min and then washed with
water as described above. The methylene chloride
solution was filtered, hexane was added dropwise to
the filtrate until crystallization began, and the mixture
was left to stand at 10 C for 1 day. Yellow needle-
like crystals formed and were filtered off and dried in
a vacuum, yield 47%.
Complex [Pt(dppy)P(C6F5)3]. To a solution of
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 73 No. 12 2003

SYNTHESIS AND PHOTOPHYSICAL PROPERTIES OF A SERIES
1845
12 mg of [Pt(dppy)dmso] in 5 6 ml of CH2Cl2 we
added 12.3 mg in P(C6F5)3, and the mixture was
stirred for 30 min. Further workup was similar to that
described for (Bu4N)[Pt(dppy)CN] and [Pt(dppy)en].
Light yellow neddle-like crystals formed in a CH2Cl2
CH3OH mixture, yield 80%.
11. Lai, S.-W., Chan, C.-W., Cheung, T.-C., Peng, S.-M.,
and Che, C.-M., Inorg. Chem., 1999, vol. 38, no. 18,
p. 4046.
12. Cheney, A.J., McDonald, W.S., o’Flynn, K., and
Shaw, B.L., Chem. Commun., 1973, vol. 128,
nos. 1 2, p. 128.
13. Deuschel-Cornioley, C., Ward, T., and von Zelew-
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p. 130.
ACKNOWLEDGMENT
The authors express their gratitude to the Analytical
Center, University of Regensburg (Germany) for help
in making investigations.
14. Maestri, M., Deuschel-Cornioley, C., and von Ze-
lewsky, A., Coord. Chem. Rev., 1991, vol. 111, no. 1,
p. 117.
The work was financially supported by the Go-
vernment of St. Petersburg and the Ministry of Educa-
tion of the Russian Federation (grant for young
scientists no. PD02-1.3-15).
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1999, vol. 18, no. 9, p. 1801.
16. Cave, G., Fanizzi, F., Deeth, R., Errington, W., and
Rourke, J., Organometallics, 2000, vol. 19, no. 7,
p. 1355.
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