Synthesis, characterisation and electronic properties of a series of platinum(II) poly-ynes containing novel thienyl-pyridine linker groups

Article abstract of DOI:10.1039/b201073a

The synthesis and characterisation of a series of novel poly-yne polymers, trans-[-(PⁿBu₃)₂Pt(C≡C-L-C≡C)-] _n (L = 2-(2′-thienyl)-pyridine (L1), 2,5-bis(2′-thienyl)pyridine (L2), 6,6′-bis(2″-thienyl)-3,3′-bipyridine (L3)), and the corresponding platinum dimers trans-[(PEt₃)₂(Ph)Pt(C≡CLC≡C)Pt(Ph)(PEt ₃)₂] are described. The dimers were prepared by the reaction of two equivalents of trans-[Pt(PEt₃)₂(Ph)Cl] with one equivalent of the diterminal diyne HC≡C-L-C≡CH, in CuI catalysed dehydrohalogenation reactions in CH₂Cl₂-Prⁱ₂NH, while the polymers are obtained similarly from the diyne and one equivalent of trans-[Pt(PⁿBu₃)₂Cl₂]. The optical absorption and photoluminescence spectra of the polymers with L1 and L2 linker groups are reported. The optical gaps are 465 nm (2.67 eV) and 486 nm (2.55 eV), respectively. The photoluminescence spectrum for each polymer exhibits one band at room temperature. At 10 K, low-energy emission bands emerge which are attributed to emission from the triplet excited state. The results of these studies are compared with those obtained for other platinum-containing poly-yne and related organometallic polymers.

Full text of DOI:10.1039/b201073a

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Synthesis, characterisation and electronic properties of a series of
platinum(II) poly-ynes containing novel thienyl-pyridine linker
groups
Muhammad S. Khan,*a Muna R. A. Al-Mandhary,a Mohammad K. Al-Suti,a Neil Feeder,b
Saifun Nahar,b Anna Köhler,c Richard H. Friend,*c Paul J. Wilsond and Paul R. Raithby*d
a College of Science, Sultan Qaboos University, PO Box 36, Al-Khod 123, Sultanate of Oman
b Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge,
UK CB2 1EW
c Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge, UK CB3 0HE
d Department of Chemistry, University of Bath, Claverton Down, Bath, UK BA2 7AY
Received 23rd January 2002, Accepted 16th April 2002
First published as an Advance Article on the web 7th May 2002
n
᎐
᎐
᎐
The synthesis and characterisation of a series of novel poly-yne polymers, trans-[–(P Bu ) Pt(C᎐C–L–C᎐C)-]
᎐
3
2
n
(L = 2-(2Ј-thienyl)-pyridine (L1), 2,5-bis(2Ј-thienyl)pyridine (L2), 6,6Ј-bis(2Љ-thienyl)-3,3Ј-bipyridine (L3)), and
᎐
᎐
the corresponding platinum dimers trans-[(PEt ) (Ph)Pt(C᎐CLC᎐C)Pt(Ph)(PEt ) ] are described. The dimers were
᎐
᎐
3
2
3 2
prepared by the reaction of two equivalents of trans-[Pt(PEt3)2(Ph)Cl] with one equivalent of the diterminal diyne
i
᎐
᎐
HC᎐C–L–C᎐CH, in CuI catalysed dehydrohalogenation reactions in CH Cl –Pr NH, while the polymers are
᎐
᎐
2
2
2
obtained similarly from the diyne and one equivalent of trans-[Pt(PnBu3)2Cl2]. The optical absorption and
photoluminescence spectra of the polymers with L1 and L2 linker groups are reported. The optical gaps are 465 nm
(2.67 eV) and 486 nm (2.55 eV), respectively. The photoluminescence spectrum for each polymer exhibits one band
at room temperature. At 10 K, low-energy emission bands emerge which are attributed to emission from the triplet
excited state. The results of these studies are compared with those obtained for other platinum-containing poly-yne
and related organometallic polymers.
Introduction
Over the last decade there has been growing interest in organo-
metallic polymeric materials that contain transition metals in
the polymer backbone.1 The development of effective poly-
condensation2 and ring-opening polymerisation strategies3 has
made possible the reliable syntheses and characterisation of
high molecular weight organometallic polymers. Such metallo-
polymers provide model systems for the study of some of the
photophysical processes that occur in conjugated organic
polymers,4 used in optoelectronic devices such as light-emitting
diodes,5 lasers,6 photocells,7 and field-effect transistors.8 In
organic conjugated polymers, light emission is possible from the
singlet excited state (fluorescence) but it is spin-forbidden from
the triplet excited state (phosphorescence). This renders the
triplet excited state difficult to examine in conjugated organic
polymers. In light emitting-diodes, electrical excitation occurs
to both singlet and triplet excited states. It is desirable to under-
stand the photophysics of the triplet excited state and in par-
ticular how its energy level relates to the chemical structure of
the material in order to provide sufficient background for the
systematic use of methods that harvest the energy of the triplet
state.9
Recently we have been examining a series of ‘rigid rod’
organometallic poly-yne polymers10 with the general formula 1
where M = Ni, Pd, Pt; R = Ph, Et, nBu, and L is one of a number
of aromatic spacer groups.
The inclusion of the transition metal introduces sufficient
spin-orbit coupling so as to allow light emission from the triplet
excited state of the conjugated ligand thus making this state
spectroscopically accessible. The π conjugation of the ligand
continues through the metal centres along the polymer chain
since there is mixing of the π* ligand orbitals and the lowest
unoccupied metal 6p states.4,11 The electronic properties of the
polymers vary with the nature of L. Appropriate variation of
L gives optical gaps in the range from 1.58 to 3.0 eV.12,13
We have recently investigated two series of platinum-
containing poly-yne polymers. In one series the conjugated
spacer ligand L is based on phenylene derivatives.12 In the
second series the ligand was varied from thiophene to bithio-
phene to terthiophene, thus rendering the ligand increasingly
electron rich.14 In both series the same energy difference
between the first excited singlet (S1) and the triplet (T1), 0.7
0.1 eV, was found.15 In an extension to this work, we have
investigated a series of systems that contain thienyl-pyridine
rings, with adjacent electron donating and accepting units in
the main polymer chain. The aim of the investigation is to
establish in what way the insertion of a donor–acceptor unit as
the spacer ligand, L, affects the energies of the singlet and
triplet excited states. These results may then be compared with
those reported for the novel platinum thienopyrazine polymer
2,16 where the spacer group, L, consists of an electron donat-
ing thiophene ring fused to an electron accepting pyrazine ring,
the unit lying perpendicular to the main polymer chain.
Copolymers that contain π-conjugated pyridine and thiophene
ring systems have already been shown to exhibit novel optical
and electronic properties,17–19 and a ruthenium-containing
polythiophene–bipyridine copolymer displays interesting redox
properties.20
DOI: 10.1039/b201073a
J. Chem. Soc., Dalton Trans., 2002, 2441–2448
This journal is © The Royal Society of Chemistry 2002
2441

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i
Scheme 1 i CuI, Pd(OAc)2, PPh3, Pr2NH, THF; ii KOH, MeOH,
THF.
We now report the synthesis, characterisation and opto-
electronic properties of a series of platinum() poly-yne
polymers that contain novel thienyl-pyridine linker groups.
and air sensitive and give insoluble brown precipitates on stand-
ing. They are significantly less soluble than the trimethylsilyl
derivatives, and compound 8 is only sparingly soluble.
Results and discussion
Synthesis of dinuclear platinum complexes and polymers
Ligand synthesis
The reaction of each of the diterminal diynes with two equiv-
alents of the platinum complex, trans-[Pt(PEt3)2(Ph)Cl], in
CH2Cl2–iPr2NH, in the presence of CuI, at room temperature,
Three mixed thienyl-pyridine ring systems, that contain two
(L1), three (L2) and four (L3) linked rings, respectively, were
initially chosen for incorporation into the ‘rigid rod’ poly-yne
systems, and these are illustrated below:
᎐
᎐
readily affords the dimers trans-[(PEt ) (Ph)Pt(C᎐CLC᎐C)Pt
᎐
᎐
3
2
(Ph)(PEt3)2] (L = L1 (9), L2 (10), L3 (11)), in good yields
(Scheme 2). The bright yellow complexes were characterised by
In the compounds with three and four rings, one or two
pyridine rings occupy the central positions with a thiophene
ring at each end. In each case pyridine rings should act as elec-
tron accepting groups and thiophene rings as electron donating
groups. Hence, in 3, there is a donor functionality at one end of
the spacer and an acceptor functionality at the other. In 4 and 5
the acceptor group(s) are central with donor groups at either
end of the spacer. This provides an adequate range of ligand
systems to probe the electronic effects of the different spacer
groups in the organometallic polymers. Each of the three
compounds, 2-(2Ј-thienyl)pyridine, 2,5-bis(2Ј-thienyl)pyridine
and 6,6Ј-bis(2Љ-thienyl)-3,3Ј-bipyridine, were dibrominated
using NBS in DMF in the absence of light. Then 5,5Ј-
bis(trimethylsiylethynyl)-2-(2Ј-thienyl)pyridine (3), 5Ј,5Љ-bis(tri-
methylsilylethynyl))-2,5-bis(2Ј-thienyl)pyridine (4), and 5Ј,5Љ-
bis(trimethylsilylethynyl)-6,6Ј-bis(2Љ-thienyl)-3,3Ј-bipyridine (5)
were prepared by the PdII/CuI catalysed cross-coupling reaction
of the resulting dibromides with trimethylsilylacetylene21 as
illustrated in Scheme 1. These compounds were isolated as
yellow (3), and bright yellow (4 and 5) solids in yields of
50–70%, and were fully characterised by IR, 1H and 13C NMR,
and UV/visible spectroscopy, and by mass spectrometry (Table
1). They are all stable in air and towards light, and are readily
soluble in common organic solvents.
Scheme 2 i 2[Pt(PEt3)(Ph)Cl], CuI, iPr2NH, CH2Cl2; ii [Pt(PnBu3)Cl2],
CuI, iPr2NH, CH2Cl2.
1
IR, H, 13C and 31P NMR, and UV/visible spectroscopies, and
EI mass spectrometry (Table 2), and all gave satisfactory
microanalyses.
Similarly, the corresponding polymers trans-[–(PnBu3)2Pt
᎐
᎐
(C᎐C–L–C᎐C)–] (L = L1 (12), L2 (13)) were prepared by the
᎐
᎐
n
reaction of one equivalent of trans-[Pt(PnBu3)2Cl2] with the
appropriate diterminal diyne, in CH2Cl2–NHiPr2, under reflux,
in the presence of CuI. The intense yellow products were puri-
fied by passing through an alumina column, and obtained as
rubbery materials from CH2Cl2–hexane. The polymers were
1
These trimethylsilylethynyl derivatives are readily converted
characterised by IR, H, 13C and 31P NMR, and UV/visible
᎐
᎐
into their free diethynyl derivatives, HC᎐C–L–C᎐CH 6–8, by
spectroscopies, and their molar masses were determined by Gel
Permeation Chromatography (GPC) (Table 2). The micro-
analyses for these polymers gave somewhat low observed car-
bon values that reflect the difficulty in isolating completely pure
samples of these relatively insoluble materials.
᎐
᎐
desilylation with KOH in MeOH22 (Scheme 1). The products
were purified by silica column chromatography, and obtained as
pale yellow solids in 70–90% yield. They were characterised
spectroscopically (Table 1). All the diterminal diynes are light
2442
J. Chem. Soc., Dalton Trans., 2002, 2441–2448

View Article Online
Table 1 Spectroscopic data for the ligand compounds 3–8
Mass
spec.
(calc.)
UV-Visible
λmax/nm
(CH2Cl2)
IR/cmϪ1
Compound (CH2Cl2)
13C-{1H} NMR/ppm
(62.89 MHz, CDCl3)
1H NMR/ppm (250.13 MHz, CDCl3)
3
4
5
2144 (s)
8.56 (1H, d, J6,3 1.34 Hz, H-6), 7.67 (1H,
dd, J4,6 2.06 Hz, J3,4 8.26 Hz, H-4), 7.49 101.67 (all s, C᎐C), 117.9 (C-5), 118.55
(1H, d, J3,4 8.25 Hz, H-3), 7.38 (1H, d,
J3Ј,4Ј 3.91 Hz, H-3Ј), 7.17 (1H, d, J4Ј,3Ј 3.89
Hz, H-4Ј), 0.24 (d, J 2.42 Hz, SiMe3)
8.75(d, 1H, J6,3 1.79 Hz, H-6), 7.79 (dd, Ϫ0.18 (s, SiMe3), 97.69, 97.14, 100.72
1H, J4,6 2.36, J4,3 6.02 Hz, H-4), 7.58 (dd,
1H, J3,6 0.43 Hz, J3,4 7.26 Hz, H-3), 7.41
Ϫ0.18 (s, SiMe3), 97.6, 99.03, 100.83,
353.1 (353.11) 353
᎐
2156 (sh)
᎐
᎐
(C᎐C)
(C-3), 124.8 (C-5Ј), 125.67 (C-2Ј), 133.65
(C-4Ј), 139.34 (C-3Ј) 145.24 (C-4), 150.64
(C-2), 152.51 (C-6)
᎐
᎐
2144 (C᎐C)
435.1 (435.7)
512.8 (512.4)
379
373
᎐
᎐
(C᎐C), 118.81 (C-3), 123.66 (C-5Ј),
᎐
124.38 (C-2Ј), 133.35, 133.74, 133.82
(d, 2H, J3Ј,4Ј 3.92 Hz, H-3Ј), 7.2 (d, 2H, (C-3Ј or C-4Ј), 141.49 (C-4), 146.64,
J4Ј,3Ј 1.33 Hz, H-4Ј), 0.25 (s, 18H, SiMe3)
8.8 (dd, 2H, J2,5 0.98 Hz, J2,4 2.23 Hz,
H-2), 7.89 (dd, 2H, J2,4 2.34 Hz, J4,5
8.27 Hz, H-4), 7.7 (dd, 2H, J2,5 0.45 Hz,
J5,4 8.44 Hz, H-5), 7.46 (d, 2H, J3Ј,4Ј 3.86
Hz, H-3Ј), 7.23 (d, 2H, J4Ј,3Ј 3.9 Hz, H-4Ј),
0.26 (s, SiMe3)
150.96 (C-2 or C-6). (100.6 MHz)
᎐
᎐
2144 (C᎐C)
100.79 (C᎐C), 118.98 (C-3 or C-5), 124.62
᎐
᎐
(C-2Ј or C-5Ј), 133.77, 134.55, (C-3Ј or
C-4Ј), 147.68 (C-4 or C-4Ј), 151.50 (C-2
or C-6) (100.62 MHz)
᎐
6
7
8
3300
8.61 (1H, d, J6,3 1.36 Hz, H-6), 7.73 (1H,
dd, J4,6 2.07 Hz, J3,4 8.27 Hz, H-4), 7.55
80.48, 81.34, 82.96, (all s, C᎐C), 117.65,
209.0 (209.02) 340
᎐
᎐
(C᎐CH)
117.99 (C-3 or C-5), 124.58, 124.84 (C-2Ј
᎐
᎐
2102.6 (C᎐C) (1H, dd, J3,6 0.7 Hz, J3,4 8.27 Hz, H-3), 7.4 or C-5Ј), 134.15 (C-4Ј), 139.67 (C-3Ј)
᎐
(1H, d, J3Ј,4Ј 3.92 Hz, H-3Ј), 7.23 (1H, d,
145.47 (C-4), 150.96 (C-2), 152.66 (C-6).
᎐
J4Ј,3Ј 3.92 Hz, H-4Ј), 3.44 (s, 1H, C᎐CH),
᎐
᎐
3.26 (s, 1H, C᎐CH).
᎐
᎐
3300
8.77 (d, 1H, J6,3 1.68 Hz, H-6), 7.82 (dd,
1H, J4,6 2.36, J4,3 6.03 Hz, H-4), 7.62 (dd,
1H, J3,6 0.63Hz, J3,4 7.71 Hz, H-3), 7.43 (C-3Ј or C-4Ј), 142.0 (C-4), 146.70, 150.91
82.79 (C᎐C), 118.83 (C-3), 123.79 (C-5Ј), 292.0 (291.4)
369
362
᎐
᎐
(C᎐CH)
124.33 (C-2Ј), 133.54, 134.20, 134.31
᎐
2101.9
᎐
(C᎐C)
(d, 2H, J3Ј,4Ј 3.84 Hz, H-3Ј), 7.22 (d, 2H, (C-2 or C-6) (100.62 MHz)
᎐
᎐
J4Ј,3Ј 3.88 Hz, H-4Ј), 3.43 (s, 2H, C᎐CH)
᎐
(400.13 MHz)
᎐
3279
8.85 (dd, 2H, J2,5 0.48 Hz, J2,4 2.15 Hz,
H-2), 8.08 (dd, 2H, J2,4 2.66 Hz, J4,5 8.32
84.45 (C᎐C), 118.75 (C-3 or C-5), 124.62,
374 (368.5)
᎐
᎐
(C᎐CH)
125.41, 125.89 (C-2Љ or C-5Љ), 134.69,
᎐
2093
(C᎐C)
᎐
Hz, H-4), 7.87 (d, 2H, J5,4 8.32 Hz, H-5), 135.35, (C-3Љ or C-4Љ), 147.57, 148.46
7.61 (d, 2H, J3Љ,4Љ 3.89 Hz, H-3Љ), 7.24 (d, (C-4 or C-4Ј), 152.21 (C-2 or C-6)
᎐
in Nujol
2H, J4Љ,3Љ 3.88 Hz, H-4Љ), 3.99 (s, 2H,
C᎐CH) (400.13 MHz, d8-THF)
᎐
᎐
Spectroscopic properties
All the organic compounds, the platinum dimers and the
ther red-shifts, such that for ligand L1, the absorption for the
diterminal diyne, 6, occurs at 340 nm, that of the corresponding
platinum dimer, 9, at 393 nm, and that of the platinum-
containing polymer, 12, at 430 nm. The dimer and polymer that
contain the three-ring spacer, L2, show a slightly smaller shift
from 420 nm for 10 to 453 nm for 13. The observed red-shift, as
with the poly-thiophene platinum complexes and polymers,14,23
is consistent with the platinum fragments acting as net electron
donors to the electron withdrawing spacer groups.25
᎐
platinum polymers show a single strong ν(C᎐C) absorption,
᎐
that in the metal complexes is consistent with the trans con-
figuration for the Pt() centres. As observed in other poly-yne
᎐
compounds there is a lowering of the ν(C᎐C) stretching
᎐
frequencies in the platinum complexes and polymers compared
to the values found in the corresponding trimethylsilyl-
substituted diyne compounds.14,23 This may be attributed to
either metal-yne π-back bonding or the Mδϩ–CδϪ polarity.24 The
1H and 13C NMR spectra exhibit the expected signals for the
systems including resonances around 102 ppm for the acetyl-
enic carbons. The single resonance in the 31P NMR for all the
platinum() dimers and polymers confirms the trans arrange-
ment of the phosphine ligands.
Molecular structure of 4
In order to confirm the linear nature of the compounds and
polymers the crystal structure of the bis-(trimethylsilylethynyl)
derivative of spacer L2, compound 4, has been determined. The
molecular structure of 4 is shown in Fig. 1 while selected bond
The mass spectrometric results confirm the molecular
assignments for the organic compounds and the platinum dimer
complexes. The weight-average molecular weights (Mw)
obtained by GPC for 12 and 13 indicate a high degree of poly-
merisation. The number-average molecular weight (Mn) values
for 12 and 13 correspond to 115 and 159 repeating units per
chain, respectively.
The solution electronic absorption spectra of the organic
diyne compounds all exhibit one, strong, relatively low-energy
π–π* transition. There is a shift towards longer wavelength for
the trimethylsilyl derivatives when compared to the diterminal
diynes, and there is also a shift to longer wavelength in going
from the two-ring compounds, 3 and 6, to the three and four-
ring compounds, 4 and 7, and 5 and 8, respectively. These shifts
presumably reflect higher degrees of conjugation as the number
of rings in the central spacer increases. The platinum() dimers
and the metallo-poly-yne polymers also exhibit absorption
spectra that are dominated by π–π* transitions, and show fur-
Fig. 1 The molecular structure of 4 showing the atom numbering
scheme. Anisotropic displacement parameters are shown at the 50%
probability level.
parameters are presented in Table 3. The molecule sits on a
crystallographic centre of symmetry, at the centre of the pyr-
idine ring, and as a consequence the two trimethylsilylethynyl
substituents are diametrically opposite in the required pseudo-
trans relationship. The crystallographic symmetry imposes dis-
order on the central pyridine ring such that the nitrogen atom,
J. Chem. Soc., Dalton Trans., 2002, 2441–2448
2443

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Table 2 Spectroscopic data for the platinum compounds 9–13
31P-{1H}
NMR/ppm
(101.3 MHz,
CDCl3)
Mass
spec.
(calc.)
UV-Visible
λmax/nm
(CH2Cl2)
IR/cmϪ1
Compound (CH2Cl2) 1H NMR/ppm (CDCl3)
13C-{1H} NMR/ppm (CDCl3)
9
2084.3
(C᎐C)
᎐
1.08 (t, 36H, CH3), 1.69–1.76 (m, 24H,
CH2P), 6.80–6.98 (m, Ph), 7.29 (br, 1H,
H-4Ј), 7.32 (br, 1H, H-3Ј), 7.42 (br, 1H,
H-3), 7.4 (dd, 1H, J4,6 1.7 Hz, J4,3 8.29
8.02 (t, CH3), 15.14 (t, CH2P),
Ϫ129.98 1JPt–P
1315 Hz
1225
(1223)
393
᎐
᎐
102.7 (C᎐C), 117.32, 119.42 (C-3
᎐
or C-5), 121.40, 125.16, (C-2Ј or
C-5Ј), 127.37, 128.12 (C-4Ј or
Hz, H-4), 8.46 (d, 1H, J6,3 1.12 Hz, H-6) C-3Ј), 138.89 (C-4), 150.37 (C-2
(250.13 MHz)
or C-6) (62.896 MHz)
10
2081.3
(C᎐C)
᎐
1.02–1.15 (m, 36H, CH3), 1.69–1.78 (m,
24H, CH2P), 6.96 (t, Ph), 7.12 (d, 2H,
J4Ј,3Ј 3.77 Hz, H-4Ј), 7.32 (d, 2H, J3Ј,4Ј
8.03 (s, CH3), 14.99–15.33 (m,
Ϫ129.46, 1JPt–P 1307
1313 Hz (1305)
420
᎐
᎐
PCH2), 102.8 (C᎐C), 118.1 (C-5),
᎐
121.37 (C-3), 123.27, 124.29 (C-2Ј
3.34 Hz, H-3Ј), 7.52 (d, 1H, J3,4 8.4 Hz, or C-5Ј), 127.36–128.21 (Ph), 132.6
H-3), 7.72 (dd, 1H, J4,6 2.33 Hz, J4,3 6.4 C-3Ј), 136.42 ((C-4Ј), 139.06 (C-4),
Hz, H-4), 8.71 (d, 1H, J6,3 1.93 Hz, H-6) 146.08 (C-2), 150.84 (C-6) (100.62
(250.13 MHz)
1.02–1.13 (m, 36H, CH3), 1.70–1.77 (m,
24H, CH2P), 6.86 (d, 2H, J4Љ,3Љ 3.83 Hz,
H-4Љ), 6.96 (t, Ph), 7.07 (d, 2H, J3Љ,4Љ 3.88 118.38 (C-3 or C-5), 127.75, 128.21
Hz, H-3Љ), 7.69 (dd, 2H, J2,5 0.67, J5,4
3.15 H-5), 7.87 (dd, 2H, J2,4 2.4 Hz, J4,5
8.31 Hz, H-4), 8.76 (d, 2H, J2,4 2.44 Hz, or 4Ј), 148.43 (C-2 or C-6) (62.89
H-2) (400.13 MHz)
0.90 (t, 18H, CH3), 1.40–1.57 [m, 24H,
(CH2)2], 1.86–2.14 (m, 12H, PCH2), 6.79
(br, 2H, H-4Ј), 6.99 (br, 2H, H-3Ј), 7.27
(d, 1H, J = 2.58 Hz, H-3), 7.42 (br, 1H,
H-4), 8.4 (br, 1H, H-6) (400.13 MHz)
MHz)
11
12
13
2081.4
(C᎐C)
᎐
8.03 (s, CH3), 14.59–15.42 (m,
PCH2), 102.75 (C᎐C), 118.19,
Ϫ129.78, 1JPt–P 1384
1312 Hz (1382)
412
430
᎐
᎐
᎐
(C-2Ј or C-5Ј), 130.04–133.36 (Ph),
134.27 (C-3Љ or C-4Љ), 139.01 (C-4
MHz)
2086.7
13.84 (s, CH3), 23.78–25.08 {m,
Ϫ136.48, 1JPt–P GPC
1166 Hz 85420
nw = 115
᎐
(C᎐C)
(CH2)2}, 26.38 (PCH2), 102.5
᎐
᎐
(C᎐C), 117.66, 117.78 (C-3 or C-5),
᎐
123.18, 123.8, (C-2Ј or C-5Ј),
128.58, (C-4Ј), 137.62 (C-3Ј),
148.42 (C-4), 151.45, 151.76 (C-2
or C-6).
2086.6
0.94 (t, 18H, CH3), 1.43–1.59 [m, 24H, 13.86 (s, CH3), 23.86–24.41 {m,
Ϫ136.02, 1JPt–P GPC
1163 Hz 141467
nw = 159
453
᎐
(C᎐C)
(CH2)2], 2.12–2.16 (m, 12H, PCH2), 6.82
(br, 2H, H-4Ј), 7.12 (d, 1H, J = 3.34 Hz,
H-3Ј), 7.35 (d, 1H, J = 3.34 Hz, H-3Ј),
7.52 (d, 1H, J = 8.31 Hz, H-3), 7.72 (d,
1H, J = 7.64 Hz, H-4), 8.71 (br, 1H,
H-6) (250.13 MHz)
(CH2)2}, 26.4 (s, PCH2), 102
᎐
᎐
(C᎐C), 118.3 (C-5), 123.3, 124.37
᎐
(C-3 or C-5Ј), 128.42, 128.64
(C-2Ј), 132.08 C-3Ј), 132.58
((C-4Ј), 136.89 (C-4), 140.62 (C-2),
146.16 (C-6).
Table 3 Selected bond lengths (Å) and angles (Њ) for 4a
No solid-state π–π stacking between adjacent molecules, nor
short intermolecular contacts below 3 Å are present, presum-
ably due to the presence of the bulky trimethylsilyl groups.
Si(1)–C(1)
Si(1)–C(3)
C(4)–C(5)
C(6)–C(7)
S(1)–C(9)
C(8)–C(9)
C(10)–C(11)
C(11)–C(12a)
1.856(3)
1.855(4)
1.202(5)
1.370(4)
1.724(3)
1.365(4)
1.386(4)
1.373(5)
Si(1)–C(2)
Si(1)–C(4)
C(5)–C(6)
C(6)–S(1)
C(7)–C(8)
C(9)–C(10)
C(10)–N(1)
1.850(3)
1.844(4)
1.424(5)
1.731(3)
1.411(5)
1.467(4)
1.349(4)
Absorption spectroscopy
The electronic absorption spectra of the polymers were also
investigated in the solid state, the materials were spun into films.
Fig. 2 shows the normalised electronic absorption spectra of
the platinum-containing polymers 12 and 13, respectively.
The spectra of 12 and 13 both comprise of two prominent
C(2)–Si(1)–C(1)
C(3)–Si(1)–C(1)
C(4)–Si(1)–C(2)
Si(1)–C(4)–C(5)
C(5)–C(6)–C(7)
C(7)–C(6)–S(1)
C(6)–C(7)–C(8)
C(8)–C(9)–C(10)
C(10)–C(9)–S(1)
N(1)–C(10)–C(9)
110.52(18)
111.45(19)
109.53(17)
179.7(4)
129.3(3)
110.9(3)
112.4(3)
129.9(3)
119.7(2)
119.1(3)
C(2)–Si(1)–C(3)
C(4)–Si(1)–C(1)
C(4)–Si(1)–C(3)
C(4)–C(5)–C(6)
C(5)–C(6)–S(1)
C(6)–S(1)–C(9)
C(7)–C(8)–C(9)
C(8)–C(9)–S(1)
N(1)–C(10)–C(11)
C(11)–C(10)–C(9)
109.68(17)
107.64(16)
109.68(17)
178.5(4)
119.8(2)
92.23(16)
114.1(3)
110.4(3)
119.6(3)
121.3(3)
C(10)–N(1)–C(11a) 119.8(3)
C(10)–C(11)–C(12a) 120.6(3)
a Symmetry transformation used to generate the equivalent atoms “a”
is Ϫx ϩ 2, Ϫy, Ϫz ϩ 1.
N(1), and the ring carbon, C(12), are disordered over the two
sites in a 50 : 50 ratio. The dihedral angle between the pyridine
ring and the unique thiophene ring is 6.1Њ (12.2Њ between
thiophene rings), the twist reducing the unfavourable steric
interaction between the hydrogen atoms on the adjacent pyr-
idine and thiophene rings. This twist angle is similar to that
found in 2-(2Ј-thienyl)pyrazine, L1, and in a number of related
molecules.26 A search of the Cambridge Structural Database27
revealed no structures containing the L2 unit.
Fig. 2 Thin film absorption spectra of polymer 12 (dotted line) and 13
(solid line).
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J. Chem. Soc., Dalton Trans., 2002, 2441–2448

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absorption bands in the visible region. Bands of similar inten-
sity are observed at 430 and 455 nm for 12, whereas 13 also
possesses a band at 430 nm with an additional high-energy
shoulder centred at ca. 405 nm. The optical gaps for 12 and 13
are at 465 nm (2.67 eV) and 486 nm (2.55 eV). This compares to
the corresponding polymers containing a bithiophene or ter-
thiophene spacer which have optical gaps of 486 (2.55 eV) and
516 nm (2.40 eV).14 This represents a blue-shift of 0.12 and 0.15
eV, respectively.
485 nm (2.56 eV) for 13 is 0.78 and 0.77 eV, respectively. These
gaps fall in the same range as the values obtained for the S1–T1
energy gaps in related polymeric materials.11–16
There are three noteworthy features in these results. The first
is the markedly smaller (0.14 eV) S1 to S0 gap observed for
polymer 13 over 12. In order to understand the electronic struc-
tures of the bridging groups we have performed preliminary
density functional theory (DFT) calculations on the diethynyl
functionalised 6 and 7 bridging groups, respectively, using the
Gaussian 98 program,28 employing the B3LYP29–31 functional in
conjunction with the 6–31G* basis set for H, C, N and S.32
Representations of the HOMO and LUMO levels for 6 (Cs) and
7 (C1) are given in Fig. 5. When the second thiophene ring is
Photoluminescence spectroscopy
The solid-state photoluminescence spectra of the polymers as
spun films recorded at 10 K and room temperature are illus-
trated in Fig. 3 for 12 and Fig. 4 for 13, respectively. The spectra
Fig. 3 Photoluminescence spectra of a thin film of polymer 12 at 10
and 300 K.
Fig. 5 Molecular orbital plots for the HOMO and LUMO of 6 and 7.
introduced into the then planar 6 molecule the HOMO–LUMO
energy gap is reduced by ca. 0.3 eV, which is inherently a con-
sequence of greater conjugation in the longer bridging ligand.
However, the magnitude of that “reduction” is reduced as the
optimised ground state structure of 7 contains a twist of ca. 24Њ
between the pyridine and second thiophene ring (see Fig. 5),
which mediates unfavourable intramolecular interactions
between hydrogen atoms on adjacent rings, and is consistent
with the twist seen in the crystal structure described earlier in
the paper. Due to the similarity in the natures of the HOMO
and LUMO levels for 6 and 7, similar situations can be envis-
aged when the ethynyl protons are exchanged for linking
Pt(PR3)2 groups, and hence there again the HOMO–LUMO
gap for 13 should be smaller than for 12, and polymer 13 should
be twisted.
Fig. 4 Photoluminescence spectra of a thin film of polymer 13 at 10
and 300 K.
were taken on the same sample, in each case, with the same
experimental geometry and set-up. They are comparable in
intensity except for changes in the absorbance at the excitation
wavelength that may occur, and this factor does not signifi-
cantly alter the general spectral features. The low temperature
spectra show two emission bands, one from about 450 to
600 nm, and one from about 630 or 670 to beyond 850 nm. We
attribute the first (higher energy) band to emission from the first
singlet excited state, S1, (fluorescence) while we attribute the
second (lower energy) band to emission from the first triplet
excited state, T1, (phosphorescence) due to its strong temp-
erature dependence, energetic position and line shape.11–16 The
energetic separation of the peak for the triplet state at 646 nm
(1.92 eV) for 12 and at 691 nm (1.79 eV) for 13 from the peak
for the singlet excited state at 460 nm (2.70 eV) for 12 and at
The second feature is the blue-shift of the singlet state com-
pared to the corresponding bi- and tri-thiophene-containing
systems. If there was any charge-transfer-like electronic inter-
action between the electron-rich thiophene ring and the
electron-poor pyridine ring, this should result in increased
conjugation and thus lead to a red-shift with respect to an
J. Chem. Soc., Dalton Trans., 2002, 2441–2448
2445

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analogous system consisting only of thiophene rings. The
observed blue-shift indicates the absence of such a charge-
transfer interaction. Instead, exchange of a thiophene ring by a
pyridine ring seems to reduce any donor–acceptor interaction
between the metal and the ligand. This can be rationalised by
considering that the pyridine ring might withdraw electron
density from the polymer backbone towards the lone pair. This
reduction in electron density compared to a purely thiophene-
containing system manifests itself in reduced conjugation and
thus higher optical gaps. Indeed, the calculated HOMO–
LUMO energy gaps for 6 and 7 are ca. 0.2 eV higher than those
of their corresponding bi- and tri-thiophene analogues (C2),
which is mainly a consequence of the HOMOs of 6 and 7 being
higher in energy that those of their thiophene counterparts,
whereas the energy levels of the corresponding LUMOs are
comparable.
The last important feature is the observation of a S1–T1
energy gap that is identical to the values observed for other
platinum-containing polymers with phenylene or thiophene-
based spacer ligands.11–16 Earlier work has shown that the triplet
excited state in these materials is localised within one spacer
unit4,14 while the singlet excited state extends over one or two
repeat units.4 It is, therefore, reasonable to speculate that intra-
ligand charge-transfer interactions between the thiophene and
pyridine units might shift the energy of the triplet excited state
with respect to the singlet state. However, there is no such effect
on the position of the triplet state, consistent with the lack
of any charge-transfer effect on the energetic position of the
singlet state.
referenced to external trimethylphosphite and solvent reson-
ances, respectively. Infrared spectra were recorded as CH2Cl2
solutions, in a NaCl cell, using a Perkin–Elmer 1710 Fourier
Transform IR spectrometer. Mass spectra were recorded
using a Kratos MS890 spectrometer with electron impact (EI)
techniques. Microanalyses were performed in the Department
of Chemistry. UV/visible absorption spectra were obtained
using a Perkin–Elmer Lambda UV/NIR spectrometer. Column
chromatography was performed on alumina (Brockman Grade
II–III).
Synthesis of the spacer groups
5,5Ј-Dibromo-2-(2Ј-thienyl)pyridine (BrL1Br). The compound
was synthesised by following the literature method.35 1H NMR
(250.13 MHz, CDCl3): δ = 8.58 (1H, d, J6,3 1.35 Hz, H-6), 7.70
(dd, 1H, J4,6 2.05, J3,4 8.28 Hz, H-4), 7.52 (d, 1H, J3,4 8.26 Hz,
H-3), 7.39 (d, 1H, J3Ј,4Ј 3.91 Hz, H-3Ј), 7.20 (d, 1H, J4Ј,3Ј 3.89 Hz,
H-4Ј). EI-mass spectrum: m/z 319.3; Calc. 319.2. Calc for
C9H5NSBr2: C, 33,86; H, 1.58; N, 4.39. Found: C, 33.91;
H, 1.65; N, 4.47%
5Ј,5Љ-Dibromo-2,5-bis(2Ј-thienyl)pyridine (BrL2Br). In the
absence of light, NBS (2.66 g, 15 mmol) was added portionwise
at 20 ЊC to a solution of 2,5-bis(2Ј-thienyl)pyridine (1.80 g, 7.4
mmol) in DMF (25 mL). The reaction mixture was stirred for
3 h, poured onto ice forming a yellow–brown precipitate. The
solid was filtered off, washed several times with water and dried
in vacuo over P2O5. The crude product was purified by column
chromatography on alumina using CH2Cl2–hexane (4 : 1 v/v) to
yield a yellow solid. Recrystallisation from ethanol afforded
1
2.12 g (88% yield) as a bright yellow solid. H NMR (250.13
Conclusions
MHz, CDCl3): δ = 8.74 (d, 1H, J6,3 1.74 Hz, H-6), 7.75 (dd, 1H,
J4,6 2.37, J4,3 6.01 Hz, H-4), 7.60 (dd, 1H, J3,6 0.55 Hz, J3,4 7.64
Hz, H-3), 7.42 (d, 2H, J3,4 3.88 Hz, H-3Ј), 7.21 (d, 2H, J4Ј,3Ј 2.33
Hz, H-4Ј). EI-mass spectrum: m/z 401.3; Calc. 401.3. Calc for
C13H7NS2Br2: C, 38.90; H, 1.76; N, 3.49. Found: C, 38.98; H,
1.74; N, 3.53%.
In summary, it has been shown that it is possible to prepare
a series of platinum poly-yne polymers that contain mixed
heterocyclic ring linker groups in good yields, by CuI catalysed
dehydrohalogenation reactions. Polymers with molar masses in
the range 85,000–140,000 that contain the 2-(2Ј-thienyl)-
pyridine (12) and 2,5-bis(2Ј-thienyl)pyridine (13) linking groups
have been fully characterised. The optical gaps for the two
polymers, 12 and 13, are 2.67 and 2.55 eV, respectively, which
compare to gaps of 2.55 and 2.40 eV observed for the corre-
sponding polymers that contain bi and tri-thiophene linker
groups,14 and represents blue-shifts of 0.12 and 0.15 eV, respect-
ively. This result is consistent with a reduction in the donor–
acceptor interaction between the metal and the ligand. The
photoluminscence spectra exhibit both triplet (phosphor-
escence) and singlet (fluorescence) emission. In both cases the
triplet emission is ca. 0.8 eV below the singlet emission, a
feature that has been similarly observed in the spectra of related
systems.11–16 These results have stimulated a study of organo-
metallic polymers that contain spacer groups with significantly
different intra-ligand charge transfer properties, and this work
is in progress.
5Љ,5Љ-Dibromo-6,6Ј-bis(2Љ-thienyl)-3,3Ј-bipyridine (BrL3Br).
In the absence of light, NBS (0.356 g, 2 mmol) dissolved in
DMF (10 mL), was rapidly added to a vigorously stirred solu-
tion of 6,6Ј-bis(2Љ-thienyl)-3,3Ј-bipyridine (0.32 g, 1 mmol) in
DMF (50 mL) at 80 ЊC. After 2 h the reaction mixture was
cooled to room temperature. and poured onto ice. The crude
product was purified by column chromatography using
CH2Cl2–hexane (2 : 1 v/v) on alumina to yield a bright yellow
1
solid, 0.37 g (76%). H NMR (250.13 MHz, CDCl3): δ = 8.78
(dd, 2H, J2,5 0.78 Hz, J2,4 2.19 Hz, H-2), 8.01 (dd, 2H, J2,4 2.44,
J4,5 8.29 Hz, H-4), 7.82 (dd, 2H, J2,5 0.48 Hz, J5,4 8.49 Hz, H-5),
7.46 (d, 2H, J3Љ,4Љ 3.88 Hz, H-3Љ), 7.25 (d, 2H, J4Љ,3Љ 3.89 Hz,
H-4Љ). EI-mass spectrum: m/z 478.5; Calc. 478.4. Calc for
C18H10N2S2Br2: C, 45.19; H, 2.11; N, 5.86. Found: C, 45.23;
H, 2.14; N, 5.95%.
5Ј,5Љ-Bis(trimethylsilylethynyl)-2,5-bis(2Ј-thienyl)pyridine (4).
5Ј,5Љ-Dibromo-2,5-bis(2Ј-thienyl)pyridine (3g, 7.48 mmol) was
Experimental
All reactions were performed under an inert nitrogen
atmosphere using standard Schlenk techniques. Solvents were
pre-dried and distilled before use by standard procedures.33
All chemicals, except where stated otherwise, were obtained
from commercial sources and used without further purification.
Trimethylsilyl acetylene was obtained from the preparation
laboratory in the Department of Chemistry, University of
Cambridge. The platinum complex trans-[Pt(PnBu3)2Cl2] was
prepared by the literature method,34 as were each of the
three compounds, 2-(2Ј-thienyl)pyridine,17 2,5-bis(2Ј-thienyl)-
pyridine17 and 6,6Ј-bis(2Љ-thienyl)-3,3Ј-bipyridine,19 NMR
spectra were recorded on a Bruker WM-250 spectrometer in
appropriate solvents. 31P{1H} NMR and 1H NMR spectra were
dissolved in freshly distilled THF–iPr2NH (700 cm3, 6 : 1 v/v) at
᎐
room temperature under nitrogen. Me SiC᎐CH (1.83 g, 18.69
᎐
3
mmol) was then added followed by the catalysts CuI (17.8 mg,
0.093 mmol), Pd(OAc)2 (16.9 mg, 0.075 mmol) and PPh3
(97.7 mg, 0.37 mmol). The solution mixture was stirred at room
temperature for 1 h then slowly heated to reflux for 48 h. The
reaction was monitored by IR spectroscopy and TLC until
completion was established. The solution was allowed to cool
to room temperature, Et2O (100 cm3) was added and the pre-
cipitate was filtered off. The volatiles were removed from the
yellow filtrate under reduced pressure and the residue was dis-
solved in Et2O (100 cm3) and washed sequentially with 10%
HCl (3 × 100 cm3), H2O (3 × 100 cm3), NaHCO3 (3 × 100 cm3),
2446
J. Chem. Soc., Dalton Trans., 2002, 2441–2448

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and H2O (3 × 100 cm3). The resulting organic phase was then
dried (MgSO4) and the volatiles removed once again to leave a
yellow residue. The residue was dissolved in the minimum
amount of CH2Cl2 and subjected to column chromatography
on silica using toluene–CH2Cl2 (2 : 1 v/v). The product eluted as
a bright yellow band which was further purified by recrystallis-
ation from warm 2 : 1 toluene–CH2Cl2 to afford 4 as glistering
yellow flakes in 67% yield (2.2 g). Calc. for C23H25Si2S2N: C,
63.4; H, 5.78; N, 3.21. Found: C, 61.9; H, 5.62; N, 3.03.
described for 9 by the reaction of 7 (41.38 mg, 0.142 mmol)
with equivalents of trans-[Pt(PEt3)2(Ph)Cl] (154.5 mg,
0.284 mmol). Calc. for C53H77P4Pt2S2N: C, 48.7; H, 5.94;
N, 1.07. Found: C, 48.98; H, 5.91; N, 1.04%.
2
᎐
᎐
᎐
Trans-[(PEt P) (Ph)Pt(C᎐C–L3–C᎐C)Pt(Ph)(PEt ) ] (11).
᎐
3
2
3 2
Complex 11 was synthesised using the similar method to that
described for 9 from the reaction of 8 (55.9 mg, 0.15 mmol) and
trans-[Pt(PEt3)2(Ph)Cl] (165 mg, 0.303 mmol) in THF–iPr2NH
(80 cm3, 1 : 1 v/v) because of limited solubility of 8 in CH2Cl2.
Calc. for C58H80P4Pt2S2N2: C, 50.35; H, 5.83; N, 2.02, Found:
C, 49.33; H, 5.22; N, 2.79%.
5,5Ј-Bis(trimethylsilylethynyl)-2-(2Ј-thienyl)pyridine (3). Sim-
ilar procedures as for 4 were adopted using 5,5Ј-dibromo-2-(2Ј-
thienyl)pyridine (2.0 g, 6.27 mmol) (except that the solvent used
i
n
᎐
᎐
᎐
in this reaction was Pr2NH) to produce light yellow 3 in 60%
Trans-[–Pt(P Bu ) (C᎐C–L1–C᎐C)–] (12). To a mixture of
᎐
3
2
n
trans-[Pt(PnBu3)2Cl2] (0.19 g, 0.28 mmol) and one equivalent of
HC᎐C–L1–C᎐CH (6, 59.3 mg, 0.28 mmol) in CH Cl – Pr NH
yield (0.66 g). Calc. for C19H23Si2SN: C, 64.50; H, 6.6; N, 3.96.
Found: C, 64.47; H, 6.61; N, 3.93%.
i
᎐
᎐
᎐
᎐
2
2
2
(60 cm3, 1 : 1 v/v) was added CuI (3 mg). The mixture was
stirred at room temperature for 18 h, after which all volatiles
were removed under reduced pressure. The residue was redis-
solved in CH2Cl2 and filtered through a short alumina column.
After removal of volatiles once again a yellow residue was
obtained which was purified by precipitation from CH2Cl2–
hexane to produce a deep yellow polymer 12 in 94% yield
(0.2 g). Calc. for [C37H59SNP2Pt]n: C, 59.65; H, 7.98: N, 1.88.
Found: C, 54.76; H, 7.35; N, 1.76%.
5Љ,5Љ-Bis(trimethylsilylethynyl)-6,6Ј-bis(2Љ-thienyl)-3,3Ј-bipyr-
idine (5). Similar procedures as for 3 were adopted using 5Ј,5Љ-
dibromo-6,6Ј-bis(2Љ-thienyl)-3,3Ј-bipyridine (1.2 g, 2.51 mmol)
to produce bright yellow 5 in 52% yield (0.66 g). Calc. for
C28H28Si2S2N2: C, 65.50; H, 5.50; N, 5.46. Found: C, 64.10; H,
5.22; N, 5.29%.
5Ј,5Љ-Di(ethynyl)-2,5-bis(2Ј-thienyl)pyridine (7). The tri-
methylsilylethynyl-derivative 4 (145 mg, 0.33 mmol) was desil-
ylated by dissolving in freshly distilled THF–MeOH (70 cm3,
6 : 1 v/v) and adding dropwise a solution of KOH (92 mg,
1.65 mmol) in a minimum amount of H2O. The reaction was
completed by stirring for 1 h at room temperature. The volatiles
were then removed under reduced pressure to afford a light
yellow residue which was washed with H2O and extracted with
CH2Cl2. The solution was dried (MgSO4) and filtered and
the volatiles removed under reduced pressure. The residue was
subjected to column chromatography on silica using toluene–
CH2Cl2 (2 : 1 v/v) affording the desired product as a light yellow
solid in 77% yield (75 mg). Calc. for C17H9S2N: C, 70.10; H,
3.11; N, 4.81. Found: C, 68.96; H, 3.43; N, 4.47%.
n
᎐
᎐
᎐
Trans-[–Pt(P Bu ) (C᎐C–L2–C᎐C)–] (13). The diterminal
᎐
3
2
n
i
diyne 7 (17.3 mg, 0.06 mmol) was dissolved in 100 ml Pr2NH
and heated at 95 ЊC for 30 min. Trans-[Pt(PnBu3)2Cl2] (39.8 mg,
0.06 mmol) was added followed by CuI (2 mg). The reaction
mixture was then heated under reflux for a further 24 h, after
which all volatile components were removed under reduced
pressure. The mixture was worked up as described for 12 to
produce a deep yellow rubbery polymer 13 in 75% yield (0.04 g).
Calc. for [C41H61S2NP2Pt]n: C, 55.38; H, 6.92; N, 1.57. Found:
C, 53.51; H, 6.64; N, 1.46%.
X-Ray crystallography
A colourless, plate-like crystal of 4 was obtained by slow
evaporation of a CH2Cl2–hexane solution. Crystal data were
collected on a Rigaku R-Axis II imaging plate diffractometer
equipped with a molybdenum rotating anode target, a graphite
monochromator, and an Oxford Cryosystems crystal cooling
apparatus.
5,5Ј-Di(ethynyl)-2-(2Ј-thienyl)pyridine (6). Compound 6 was
synthesised from 3 adopting a similar procedure to that
described above for 7. The product was obtained as a pale
yellow solid in 84% yield after purification using a silica column
and CH2Cl2–hexane (1 : 2) as eluent. Calc. for C13H7SN: C,
74.6; H, 3.37; N, 6.69. Found: C, 74.58; H,3.50; N, 6.60%.
Crystal data: Crystal size 0.40 × 0.25 × 0.10 mm, monoclinic,
P21/c, a = 17.605(3), b = 5.744(2), c = 11.719(2) Å, β = 96.42(1)Њ,
5Љ,5Љ-Di(ethynyl)-6,6Ј-bis(2Љ-thienyl)-3,3Ј-bipyridine (8). Com-
pound 8 was synthesised from 5 adopting the similar procedure
as above for 7. However, the product 8 was only sparingly
soluble in organic solvents which made purification difficult. It
was purified by passing a THF (sparingly soluble) solution
through a silica column and washing the residue with hexane.
The product was not sufficiently pure for use with organometal-
lic polymerisation reactions where an accurate 1 : 1 reactant
ratio is required.
V = 1177.6 Å3, Z = 2, ρcalc = 1.229 Mg mϪ3, µ = 0.337 mmϪ1
,
2θmax = 50.38Њ, MoKα radiation, λ = 0.71073 Å, T = Ϫ93 ЊC, two
orientations: 18 frames, 10Њ per frame, 100 s per frame and 23
frames, 8Њ per frame, 80 s per frame, 3641 reflections measured,
1999 (Rint = 0.0627) independent reflections; data corrected for
Lorentz polarization and for absorption (min. and max. trans-
mission 0.877, 0.967); structure solved by direct methods
(TEXSAN),36 and refined by full matrix least-squares based on
F 2 (SHELXL97).37 131 parameters. H atoms in calculated posi-
tions, R1 = 0.0550 for 1397 observed reflections, and wR2 =
Synthesis of the platinum complexes and polymers
0.137 (all data), S ᎐ 0.995; final residual electron density 0.268
᎐
᎐
᎐
᎐
Trans-[(PEt ) (Ph)Pt(C᎐C–L1–C᎐C)Pt(Ph)(PEt ) ]
(9).
and Ϫ0.306 e ÅϪ3. C(12) and N(1) disordered of two sites with
50% occupancies.
᎐
3
2
3 2
Treatment of the diterminal diyne compound 6 (29.1 mg,
0.14 mmol) with 2 equivalents of trans-[Pt(PEt3)2(Ph)Cl] (151
mg, 0.277 mmol) for 20 h at room temperature, in the presence
of CuI (3 mg), in CH2Cl2–iPr2NH (60 cm3, 1 : 1 v/v), gave the
required complex as a bright yellow solid in 39% yield (0.15 g)
after purification on a silica column using toluene–CH2Cl2
(2 : 1) as eluent and subsequent recrystallisation from a hot
solution of hexane–CH2Cl2 (2 : 1). Calc. for C49H75P4Pt2SN:
C, 48.07; H, 6.18; N, 1.14. Found: C, 48.67; H, 6.13; N, 1.44%.
CCDC reference number 148650.
See http://www.rsc.org/suppdata/dt/b2/b201073a/ for crystal-
lographic data in CIF or other electronic format.
Molecular weight determinations
Molar masses were determined by Gel Permeation Chrom-
atography (GPC) using two PL Gel 30 cm, 5 micron mixed
C columns at 30 ЊC running in THF at 1 cm3 minϪ1 with a Roth
Mocel 200 high precision pump. A DAWN DSP (Wyatt
Technology) Multi-Angle Laser Light Scattering (MALLS)
᎐
᎐
᎐
Trans-[(PEt P) (Ph)Pt(C᎐C–L2–C᎐C)Pt(Ph)(PEt ) ] (10).
᎐
3
2
3 2
Complex 10 was synthesised using the same conditions as
J. Chem. Soc., Dalton Trans., 2002, 2441–2448
2447

View Article Online
12 J. S. Wilson, A. Köhler, R. H. Friend, M. K. Al-Suti, M. R. A.
Al-Mandhary, M. S. Khan and P. R. Raithby, J. Chem. Phys., 2000,
113, 7627.
13 W.-Y. Wong, K.-H. Choi, G.-L. Lu and J.-X. Shi, Macromol. Rapid
Commun., 2001, 22, 461.
14 N. Chawdhury, A. Köhler, R. H. Friend, W.-Y. Wong, J. Lewis,
M. Younus, P. R. Raithby, T. C. Corcoran, M. R. A. Al-Mandhary
and M. S. Khan, J. Chem. Phys., 1999, 110, 4963.
15 J. S. Wilson, N. Chawdhury, M. R. A. Al-Mandhary, M. Younus,
M. S. Khan, P. R. Raithby, A. Köhler and R. H. Friend, J. Am.
Chem. Soc., 2001, 123, 9412.
16 M. Younus, A. Köhler, S. Cron, N. Chawdhury, M. R. A.
Al-Mandhary, M. S. Khan, J. Lewis, N. J. Long, R. H. Friend and
P. R. Raithby, Angew. Chem., Int. Ed. Engl., 1998, 37, 3036.
17 Z.-H. Zhou, T. Maruyama, T. Kanbara, T. Ikeda, K. Ichimura,
T. Yamamoto and K. Tokuda, J. Chem. Soc., Chem. Commun., 1991,
1210.
apparatus with 18 detectors and auxiliary Viscotek model 200
differential refractometer/viscometer detectors was used to
calculate the absolute molecular weights (referred to GPC LS).
Photophysical measurements
The polymer films for optical measurements were spin-coated
from dichloromethane solutions onto quartz substrates. The
optical absorption was measured with a Perkin–Elmer λ-9
spectrometer. Excitation for the photoluminescence studies was
provided by UV lines (334–364 nm) of an Arϩ laser; the samples
were mounted in a continuous flow helium cryostat. The
emission spectra were recorded using a spectrograph with an
optical fibre input and a CCD (charge coupled device) parallel
detection system (Oriel Instaspec IV).
18 I. H. Jenkins, U. Salzner and P. G. Pickup, Chem. Mater., 1996, 8,
2444.
Acknowledgements
19 I. H. Jenkins, N. G. Rees and P. G. Pickup, Chem. Mater., 1997, 9,
1213.
20 S. S. Zhu and T. M. Swager, Adv. Mater., 1996, 8, 497.
21 M. S. Khan, A. K. Kakkar, N. J. Long, J. Lewis, P. R. Raithby,
P. Nguyen, T. B. Marder, F. Wittmann and R. H. Friend, J. Mater.
Chem., 1994, 4, 1227 and references therein.
22 S. Takahashi, Y. Kuroyama, K. Sonogashira and N. Hagihara,
Synthesis, 1980, 627.
23 J. Lewis, N. J. Long, P. R. Raithby, G. P. Shields, W.-Y. Wong and
M. Younus, J. Chem. Soc., Dalton Trans., 1997, 4283.
24 J. Manna, K. D. John and M. D. Hopkins, Adv. Organomet. Chem.,
1995, 38, 79.
We are grateful to S. Mang of the Melville Laboratory for
Polymer Synthesis for assistance in GPC measurements. A. K.
thanks Peterhouse, Cambridge, and the Royal Society for
Research Fellowships. M. S. K. acknowledges Sultan Qaboos
University, Oman, for the award of a Research Grant IG./SCI./
CHEM./1999/02. This work is supported by the Engineering
and Physical Sciences Research Council (UK).
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