Synthesis and characterization of platinum(ii) di-ynes and poly-ynes incorporating ethylenedioxythiophene (EDOT) spacers in the backbone

Article abstract of DOI:10.1039/c1dt11010a

A series of trimethylsilyl-protected di-alkynes incorporating 3,4-ethylenedioxythiophene (EDOT) linker groups Me₃Si-CC-R-CC- SiMe₃ (R = ethylenedioxythiophene-3,4-diyl 1a, 2,2′-bis-3,4- ethylenedioxythiophene-5,5′-diyl 2a, 2,2′,5′,2′

Full text of DOI:10.1039/c1dt11010a

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PAPER
Synthesis and characterization of platinum(II) di-ynes and poly-ynes
incorporating ethylenedioxythiophene (EDOT) spacers in the backbone†
Muhammad S. Khan,*a Mohammed K. Al-Suti,a Hakkikulla H. Shah,a Said Al-Humaimi,a
Fathiya R. Al-Battashi,a Jens K. Bjernemose,b Louise Male,b Paul R. Raithby,*b Ning Zhang,c Anna Ko¨hlerc
and John E. Warrend
Received 30th May 2011, Accepted 22nd July 2011
DOI: 10.1039/c1dt11010a
A series of trimethylsilyl-protected di-alkynes incorporating 3,4-ethylenedioxythiophene (EDOT) linker
groups Me3Si–C C–R–C C–SiMe3 (R = ethylenedioxythiophene-3,4-diyl 1a, 2,2¢-bis-3,4-
ethylenedioxythiophene-5,5¢-diyl 2a, 2,2¢,5¢,2¢¢-ter-3,4-ethylenedioxythiophene-5,5¢¢-diyl 3a) and the
corresponding terminal di-alkynes, H–C C–R–C C–H 1b–2b has been synthesized and characterized
and the single crystal X-ray structure of 1a has been determined. CuI-catalyzed dehydrohalogenation
reaction between trans-[(Ph)(Et3P)2PtCl] and the terminal di-alkynes 1b–2b in iPr2NH/CH2Cl2 (2 : 1
mole ratio) gives the Pt(II) di-ynes trans-[(Et3P)2(Ph)Pt–C C–R–C C–Pt(Ph)(Et3P)2] 1M–2M while
the dehydrohalogenation polycondensation reaction between trans-[(nBu3P)2PtCl2] and 1b–2b (1 : 1 mole
ratio) under similar reaction conditions affords the Pt(II) poly-ynes trans-[Pt(PnBu3)2–C C–R–C C-]n
1P–2P. The di-ynes and poly-ynes have been characterized spectroscopically and, for 1M and 2M, by
single-crystal X-ray which confirms the “rigid rod” di-yne backbone. The materials possess excellent
thermal stability, are soluble in common organic solvents and readily cast into thin films. Optical
absorption spectroscopic measurements reveal that the EDOT spacers create stronger donor-acceptor
interactions between the platinum(II) centres and conjugated ligands along the rigid backbone of the
organometallic polymers compared to the related non-fused and fused oligothiophene spacers.
as p-conjugated materials featuring high quantum efficiency for
inter-system crossing to produce the triplet excited state following
direct excitation, providing considerable insight concerning the
electronic structure, delocalization, and dynamics of the triplet
exciton.11
Introduction
Conjugated polymers are used as light emitting diodes (LEDs),1
lasers,2 photocells,3 sensors,4 piezo- and pyro-electric materials,5
and are being investigated for use as optical data storage devices,6
as optical switches and signal processing devices7 as well as
having nonlinear optical (NLO) applications.8 Within the domain
of conjugated polymers two classes of material have sparked
special interest. The first class of materials is the polythiophenes
because of their applications as organic semiconductors for
transistor applications and photovoltaic cells.9 The second class of
materials comprises the “rigid-rod” platinum poly-yne polymers
of general formula trans-[(nBu3P)2Pt–C C–R–C C-]•, where R
is a conjugated spacer group.10 Metallopolymers derived from
platinum(II) alkynyl structural units have been studied widely
We have combined the polythiophenes with the platinum(II)
poly-ynes by incorporating a broad range of oligothiophene
spacers into platinum(II) poly-ynes and investigated the electronic
structure of the singlet (S1) and triplet (T1) excited states in fused
and non-fused oligothiophenes.12 The energies of the optical tran-
sitions for the S1 and T1 states shift to higher energies when going
from the non-fused to the fused systems. The shift in electronic
energies to higher values in fused system compared to non-fused
system with the same number of thiophene rings is attributed to the
level of conjugation within the oligothiophene spacers. The greater
the number of conjugated double bonds, the lower is the energy
gap. Apart from the non-fused and fused thiophene ring systems,
3,4-ethylenedioxythiophene (EDOT) also occupies a prominent
position as the functional component for conjugated polymers
due, among other things, to the strong electron donor effect of
the ethylenedioxy group, the self-rigidification of the structure by
non-covalent intermolecular interactions as well as quinoidization
of the conjugated system.13 The past decade has witnessed some
spectacular development in EDOT-based organic polymers and
aDepartment of Chemistry, Sultan Qaboos University, P.O. Box 36, Al Khod,
123, Sultanate of Oman. E-mail: msk@squ.edu.om
bDepartment of Chemistry, University of Bath, Claverton Down, Bath, UK,
BA2 7AY. E-mail: p.r.raithby@bath.ac.uk; Fax: +44 1225 386231; Tel: +44
1225 383183
cDepartment of Physics, University of Bayreuth, Bayreuth, 95440, Germany
dThe STFC Daresbury Laboratory, Daresbury, Warrington, UK, WA4 4AD
† CCDC reference numbers 828207 and 828209. For crystallographic data
in CIF or other electronic format see DOI: 10.1039/c1dt11010a
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copolymers14 but the organometallic chemistry based on the
EDOT system remains relatively unexplored. To the best of our
knowledge, there has been no report of EDOT-containing metal
alkynyl complexes and polymers except two recent reports on the
use of EDOT-benzothiadiazole hybrid spacer in platinum(II) poly-
ynes.15
4-ethylenedioxythiophene and 5,5”-diiodo-2,2¢,5¢,2”-ter-3,4-
ethylenedioxythiophene were prepared in high yields by adap-
tation of a literature procedure involving iodination of EDOT/
bis-EDOT/tris-EDOT with iodine monochloride–pyridine
complex.15 The bis-ethynyl ligands were synthesized by a sequence
of cross-coupling and proto-desilylation reactions. The protected
dialkynyl ligand precursors, 2,5-bis(trimethylsilylethynyl)-3,4-
This background prompted us to undertake the synthesis
of platinum(II) poly-ynes incorporating EDOT spacers in the
backbone, the motivation for their synthesis is to extend the
range of organometallic polymers and establish in what way
the incorporation of EDOT spacers affects the physico-chemical
properties of the new materials. Recently, attention has also
been directed toward p-conjugated dimers and oligomers, taken
not only as model compounds for the high molecular weight
polymers, but also as efficient molecular wires in electronic device
applications.16 They are more crystalline than the corresponding
polymers, allowing for a detailed structural analysis and, thus,
an assessment of the structure-electronic property relationship.17
There is also considerable interest in the solid-state structures
of the polymeric materials because of evidence for inter-chain
interactions that influence their electronic properties. In this
context an analysis of intermolecular interactions in the crystal
structures of the dialkynyl ligands and of the model di-yne
complexes may lead to a better understanding of the interactions
in the poly-ynes.18 The structural analysis of a ligand precursor 1a
and of two model dinuclear platinum(II) di-yne complexes, 1M and
2M, are reported in this paper. Spectroscopic, thermal and opto-
electronic properties of the new platinum(II) di-ynes and poly-ynes,
1M–2M and 1P–2P are also presented and compared with those
of related organometallic complexes and polymers.
ethylenedioxythiophene
1a,
5,5¢-bis(trimethylsilylethynyl)-
2,2¢-bis-3,4-ethylenedioxythiophene 2a and 5,5¢¢-bis(trimethyl-
silylethynyl)-2,2¢,5¢,2¢-ter-3,4-ethylenedioxythiophene 3a were
prepared by palladium(II)/copper(I)-catalyzed cross-coupling
reaction of trimethylsilylethyne with the respective diiodo-EDOT,
i
in Pr2NH–THF as illustrated in Scheme 1.19 The protected
dialkynes are indefinitely stable towards light and air at ambient
temperature and were fully characterised by IR, NMR (1H
and 13C) spectroscopy, EI mass spectrometry, as well as by
satisfactory elemental analyses. Conversion of the protected
dialkynes 1a–2a into the diterminal alkynes, 2,5-bis(ethynyl)-
3,4-ethylenedioxythiophene 1b, and 5,5¢-bis(ethynyl)-2,2¢-bis-3,4-
ethylenedioxythiophene 2b, was accomplished by cleavage of the
trimethylsilyl groups with dilute aqueous KOH in MeOH–THF
(Scheme 1). The products were purified by silica gel column
chromatography and isolated as orange to red solids in 78–85%
yields. The diterminal alkynes 1b and 2b are somewhat unstable;
storage over a long period of time at ambient temperature and
under aerobic conditions leads to the formation of dark insoluble
material that was presumed to be polymerization products.
Hence, 1b and 2b were prepared freshly before reaction with
the platinum(II) phosphine complexes. The diterminal alkyne 3b
rapidly decomposed as formed during the cleavage reaction and
therefore could not be isolated for reaction with the platinum(II)
phosphine complexes.
Results and discussion
The
dehydrohalogenation
reactions
between
trans-
Synthesis
[(Ph)(Et3P)2PtCl] and the diterminal alkynes 1b–2b in a 2 : 1
stoichiometry, in iPr2NH–CH2Cl2, in the presence of CuI at room
temperature gave the dinuclear platinum(II) di-ynes 1M–2M while
The key starting materials for the dialkynyl ligand precursors,
2,5-diiodo-3,4-ethylenedioxythiophene,
5,5¢-diiodo-2,2¢-bis-3,
Scheme 1
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Scheme 2
dialkynes 1a–2a (2140–2150 cm-1). The fact that terminal ethynes
the polycondensation reactions between trans-[(PnBu3)2PtCl2] and
1b–2b, in a 1 : 1 ratio, under similar reaction conditions, readily
afforded the platinum(II) poly-ynes 1P and 2P (Scheme 2). The
poly-ynes were obtained in yields of 85–90%, pointing to a very
high conversion.
(HC C–R) have lower nC
frequencies than their protected
C
counterparts RC C–R (by about 40 cm-1 in this case) is well
established.21 Furthermore, the platinum(II) di-ynes and poly-
ynes display lower nC values than those in the corresponding
C
Purification of the platinum(II) di-ynes was accomplished by
column chromatography or preparative TLC on silica while
the poly-ynes were purified by chromatography on an alumina
column.
protected or terminal dialkynes. This may be attributed to either
metal-yne p-backbonding or the Md+–Cd- polarity.22 NMR analy-
ses indicate a rigid structure for the platinum(II) di-ynes and poly-
ynes. In all cases, 1H NMR resonances arising from the protons of
the aromatic ring systems were clearly observed. In addition, two
distinct 13C NMR peaks for the individual ethynylenic carbons
in the di-ynes and poly-ynes were observed, in accord with their
formulations, and they are shifted downfield with respect to the
signals in the diterminal alkynes. The resonances due to the ethyl
and butyl groups were clearly identified. The single resonance in
the 31P NMR spectra of the platinum(II) di-ynes and poly-ynes
confirms the trans arrangement of the phosphine ligands. The
1JPt–P values range from 2628 to 2645 Hz for the di-ynes and 2363–
2377 Hz for the poly-ynes; the spectral features are quite similar to
Spectroscopic characterization
Preliminary, systematic characterization of the organic ligand
precursors as well as the platinum(II) di-ynes and poly-ynes
was achieved by spectroscopic methods. The IR spectra of the
platinum(II) di-ynes and poly-ynes show a single, sharp nC ab-
C
sorption at around 2085 cm-1 consistent with a trans-configuration
of the ethynylenic units around the platinum(II) centre, and the
observed value is similar to that found in a range of related
12,20
materials.20 The nC values for the terminal di-ynes 1b–2b (2107
other platinum(II) di-ynes and poly-ynes reported previously
and confirm the all-trans configuration of the compounds.
C
cm-1) are much lower than those of the trimethylsilyl-protected
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The mass spectrometric results confirm the molecular assign-
ments for the organic precursors and the platinum(II) di-ynes.
Gel permeation chromatography (GPC), using a polystyrene
(PS) standard shows that the number-average molecular weights
(Mn) of the poly-ynes are in the range of 40,000–52,000 gmol-1,
corresponding to degrees of polymerization of between 66 and
44 repeat units. The value of polydispersity index (PDI) varies
between 1.4 and 1.7. The narrow polydispersity (PDI < 2) in the
molecular weights is consistent with the extended linear structure.
GPC data indicate that the number of repeat unit per chain
for the EDOT-containing poly-yne is higher than that for the
bis(EDOT)-based poly-yne. The reduction in chain length with
increasing size of the spacer group may reflect a reduction in
solubility of the larger species. The molecular weight values should
be viewed with caution in view of the difficulties associated with
utilizing GPC for rigid-rod type polymers. GPC does not give
absolute values of molecular weights but provides a measure of
hydrodynamic volume. Rod-like polymers in solution possess very
different hydrodynamic properties to flexible polymers. Therefore,
calibration of the GPC with PS standards could inflate the values
of the molecular weights of the poly-ynes to some extent. However,
the lack of discernable resonances that could be attributed to
end groups in the NMR spectra provides support for the view
that a high degree of polymerization has been achieved in these
organometallic polycondensation reactions.
(Me)C–Si–C(Me) angles (average 110.63◦) are slightly larger than
the ( C)C–Si–C(Me) angles (average 108.27◦), and the geometry
around Si is distorted tetrahedral. The C–C bond lengths within
˚
the central EDOT ring are in the range 1.369(4)–1.494(4) A, and
reflect the expected single, C(1)–C(2), and partial multiple bond
character. The two S–C bond lengths are not significantly different
˚
˚
at 1.736(3) A, and the four C–O distances average 1.404(5) A. The
thiophene ring is essentially planar with a maximum deviation
˚
from the ring plane of 0.014 A for C(4). The ethylenedioxy unit
˚
has a total puckering parameter of 0.490(4) A, q2 of 0.384(3), q3 of
0.304(3) and f2 of -86.4(4)◦, consistent with a distorted half-chair
conformation.24 All these parameters are not significantly different
from those reported in several structures that contain EDOT ring
systems.25
The 1a molecules are packed into double-stranded columns
along the (1 0 0) direction. The two strands of these columns
are connected by two weak C–H . . . O hydrogen bonds. One,
between the ethylenedioxy oxygen acceptor atom, O(1), and an
ethylenedioxy hydrogen donor, H(1a), on a molecule related by
the symmetry operation 2 -x, -y, 1 -z (O(1) . . . H(1a),◦ 2.68(3)
˚
˚
A; C(1)–H(1), 0.86(3) A; O(1) . . . H(1a)–C(1), 141 (2) ). This
interaction forms a co-operative pair of hydrogen bonds across
a crystallographic centre of symmetry. The second hydrogen
bond involves the other ethylenedioxy oxygen atom, O(2), and
a methyl hydrogen atom, H(10b), on a molecule related by the
symmetry operation 1 -x, -y, 1 -z. Here the hydrogen bond
˚
parameters are O(2) . . . H(10b), 2.45(5) A, C(10)–H(10b), 1.00(5)
Crystal structure analysis
and O(2) . . . H(10b)–C(10) 149(4)◦.
Single crystals of compounds 1a, 1M and 2M were obtained,
and the crystal and molecular structures of these materials were
determined in order to confirm the spectroscopic assignments, and
investigate the intermolecular interactions in the solid state, with
a view to correlating the structure/property relationships in these
systems.
In the crystal structure of [(Ph)(PEt3)2Pt–C C-(EDOT)-
C–Pt(PEt3)2Ph] 1M the asymmetric unit contains one unique
dimetallic fragment the structure of which is shown in Fig. 2
which also contains a selection of relevant bond parameters.
The structure is closely related to the previously reported “rigid
C
The molecular structure of 2,5-bis(trimethylsilylethynyl)-3,4-
ehyldioxythiophene 1a is shown in Fig. 1 along with selected bond
parameters. The molecules show the expected linear geometry
(average Si–C C, 171.8(3)◦, and average C C–C, 177.3(4)◦
along the two acetylene groups on either side of the ethylene-
dioxythiophene group). The two C C bonds have an average
˚
length of 1.209(4) A, consistent with values found in a range of bis-
trimethylsilylethynyl derivatives.23 For the trimethylsilyl groups the
Fig.
2
The
molecular
structure
of
[(Ph)(PEt3)2Pt–C C–
(EDOT)–C C–Pt(PEt3)2Ph] 1M with displacement ellipsoids drawn
at the 50% probability level and hy◦drogen atoms omitted for clarity.
˚
Selected bond lengths (A) and angles ( ): Pt(1)–C(8), 2.023(8); Pt(1)–C(9),
2.061(9); Pt(1)–P(1), 2.289(2); Pt(1)–P(2), 2.286(3); Pt(2)–C(16),
2.032(10); Pt(2)–C(17), 2.062(9); Pt(2)–P(3), 2.279(3); Pt(2)–P(4),
2.287(3); C(7)–C(8), 1.194(11); C(15)–C(16), 1.201(12); C(1)–O(1),
1.399(12); C(1)–C(2), 1.419(17); C(2)–O(2), 1.455(14), C(3)–O(1),
1.364(11); C(3)–C(5), 1.387(12); C(3)–C(4), 1.415(11); C(4)–O(2),
1.367(10); C(4)–C(6), 1.380(13); C(5)–C(7), 1.424(11); C(5)–S(1), 1.732(9);
C(6)–S(1), 1.742(8); C(8)–Pt(1)–C(9), 178.1(4); C(8)–Pt(1)–P(2), 88.1(3);
C(9)–Pt(1)–P(2), 91.2(3); C(8)–Pt(1)–P(1), 92.7(3); C(9)–Pt(1)–P(1),
87.9(3); P(2)–Pt(1)–P(1), 178.82(11); C(16)–Pt(2)–C(17), 179.6(4);
C(16)–Pt(2)–P(3), 91.4(3); C(17)–Pt(2)–P(3), 88.9(3); C(16)–Pt(2)–P(4),
86.9(3); C(17)–Pt(2)–P(4), 92.8(3); P(3)–Pt(2)–P(4), 178.04(12).
Fig. 1 The molecular structure of 1a with 50% thermal ellipsoids.
◦
˚
Selected bond lengths (A) and angles ( ): C(1)–O(1), 1.450(4); C(1)–C(2),
1.494(5); C(2)–O(2), 1.447(4); C(3)–O(1), 1.363(4); C(4)–O(2), 1.354(4);
C(3)–C(4), 1.413(4); C(3)–O(5), 1.379(4); C(4)–C(6), 1.369(4); C(5)–S(1),
1.735(3); C(6)–S(1), 1.736(3); C(7)–C(8), 1.203(4); C(12)–C(13), 1.214(4);
C(5)–C(7)–C(8), 178.5(4); C(7)–C(8)–Si(1), 171.9(3); C(6)–C(12)–C(13),
176.0(3); C(12)–C(13)–Si(2), 172.0(3).
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rod” diplatinum di-yne complexes with the general formula trans-
[(Ph)(R3P)2Pt–C C–X–C C–Pt(PR3)2(Ph)], where R = Et or n-
Bu and X = C6H4, (C4H2S) and related derivatives.12,17,20,26 The
two PtC2P2 units are planar and the bond parameters associated
with the platinum(II) centres are similar to previously reported
values. The diheral angle between the Pt(1)P(1)P(2)C(8)C(9) and
the thiophene ring plane, C(3)C(4)C(5)C(6)S(1), is 40.9◦ while that
between the thiophene ring and Pt(2)P(3)P(4)C(16)C(17) is 63.8◦
in such an orientation that the resultant dihedral angle between
the two Pt square planes is 90.7◦. The acetylinic units show small
deviations from linearity with C(5)–C(7)–C(8), 171.4(10)◦, Pt(1)–
C(8)–C(7), 176.1(8)◦, C(6)–C(15)–C(16), 170.5(10)◦, and Pt(2)–
C(16)–C(15), 178.9(9)◦. The bond parameters within the central
EDOT ring are similar to those found in the structure of 1a and,
again, the thiophene ring shows slight deviations from planarity
Pt(II) centre adopts the expected square planar geometry and
the Pt1C1C9P1P2 plane makes a diheral angle of 46.2◦ with the
plane of the unique thiophene ring (C3C4C5C6S1); a value within
6◦ of that found in 1M. The two thiophene rings in the bi(3,4-
ethylenedioxythiophene) spacer group are necessarily coplanar
by crystallographic symmetry. The intramolecular S(1) . . . O(1a)
˚
distance is 2.938(3) A, which is significantly shorter than the sum of
the van der Waals distances and has previously been taken as being
indicative of a strong intramolecular interaction.27 Unlike the
structures of 1a amd 1M, the ethylenedioxy ring displays disorder
with two orientations of the C(7) and C(8) atoms. However, the
ring conformation can still be described as a half-chair. The bond
parameters within the unique EDOT fragment closely resemble
those in 1a, 1M and in a series of bi(3,4-ethylenedioxythiophene)-
containing compounds.27,28 The “rigid-rod” nature of the complex
is again confirmed by the near linear acetylene unit; C(2)–C(1)–
Pt(1), 176.0(3)◦; C(1)–C(2)–C(3), 177.9(3)◦.
˚
with the maximum deviation from the plane being 0.013 Afor C(4).
The ethylenedioxy ring adopts a distorted half chair conformation
˚
with a total puckering parameter of 0.407(6) A, q2 of 0.333(4), q3
In the crystal packing of 2M there are no particularly short
intermolecular interactions. The only significant hydrogen bond
is between a methyl hydrogen and one of the and a ring oxygen
atoms in a molecule related by the symmetry operation x, y, z
of 0.233(4) and f2 of 53.3(6)◦.
An analysis of the intermolecular interactions in the crystal
structure of 1M shows no abnormally short intermolecular
interactions. The shortest potential C–H . . . O hydrogen bond with
a C–H . . . O angle greater than 140◦ is between one of the methyl
hydrogen atoms and a ring oxygen atom in a molecule related
by the symmetry operation 1 -x, 1 -y, -z; the hydrogen bond
˚
˚
-1; C(22) . . . O(1), 3.703(4) A; H(22b) . . . O(1), 2.814(2) A; C(22)–
H(22b) . . . O(1), 151.2(2)◦.
Thermal analysis
˚
˚
parameters are C(38) . . . O(2) 3.65(1) A, H(38a) . . . O(2) 2.91 A
and C(38)–H(38a) . . . O(2) 142◦.
All samples analysed under a dinitrogen atmosphere exhibit
an exotherm coincident with mass loss due to decomposition.
Decomposition onset was defined as a mass loss of 2%. The
peak decomposition temperature was defined as the first in-
flection point in the thermogravimetric curve, corresponding to
a peak in the derivative of the TG data. The decomposition
exotherms are broad with multiple peaks, and the TG curves
suggest a stepwise decomposition process. The first step can
be assigned to the removal of trialkylphosphine groups from
the Pt(II) di-ynes and poly-ynes. TG traces show that 1M–2M
and 1P–2P have decomposition temperatures of over 400 ◦C,
indicative of excellent thermal stability. These results are quite
encouraging as they allow for the use of high temperature T
sealing procedures in device fabrication. The DTA peaks show
exotherms at these temperatures, indicating that decomposition
rather than vaporization is being observed. The results are shown
in Table 1. The results indicate that the platinum(II) di-ynes
and poly-ynes containing the EDOT spacers exhibit significantly
higher thermal stability compared to those with fused and non-
fused oligothiophene spacers,12 possibly because the ethylenedioxy
groups encourage stronger inter-chain van der Waals bonding.
The poly-yne 2P exhibits higher onset and peak decomposition
temperatures than 1P; similarly the di-yne 2M shows higher onset
and peak decomposition temperatures than 1M. Thus both the
As with 1M the complex [(Ph)(PEt3)2Pt–C C-(EDOT)-
(EDOT)-C C–Pt(PEt3)2Ph] 2M crystallises in space group C2/c
but, in this case, the asymmetric unit contains only half the
dimeric unit and there is a crystallographic centre of symmetry
at the mid-point of the C(6)–C(6a) bond that links the two EDOT
groups. The structure of the dimetallic molecule is shown in Fig.
3 which also contains a selection of relevant bond parameters.
As with 1M, the structure closely resembles that of a range of
previously reported diplatinum di-yne complexes with various
aromatic and heteroaromatic linker groups.12,17,20,26 The unique
Fig.
3
The
molecular
structure
of
[(Ph)(PEt3)2Pt–
C
C–(EDOT)–(EDOT)–C C–Pt(PEt3)2Ph] 2M with displacement
ellipsoids drawn at the 50% probability level and hydrogen atoms omitted
for clarity. The disorder in the C(7)–C(8) fragment is also omitted.
◦
˚
Selected bond lengths (A) and angles ( ): Pt(1)–C(1), 2.037(3); Pt(1)–C(9),
2.069(3); Pt(1)–P(1), 2.2920(7); Pt(1)–P(2), 2.2950(7); C(1)–C(2), 1.195(4);
C(3)–S(1), 1.752(3); C(6)–S(1), 1.742(3); C(3)–C(4), 1.371(4); C(4)–C(5),
1.418(4); C(5)–C(6), 1.371(4); C(6)–C(6a), 1.446(5); C(4)–O(1), 1.374(3);
C(5)–O(2), 1.373(3); C(7)–O(1), 1.459(5); C(8)–O(2), 1.445(6); C(7)–C(8),
1.506(9); C(1)–Pt(1)–C(9), 177.13(11); C(1)–Pt(1)–P(1), 86.46(9);
C(9)–Pt(1)–P(1), 91.52(8); C(1)–Pt(1)–P(2), 94.14(9); C(9)–Pt(1)–P(2),
88.02(8); P(1)–Pt(1)–P(2), 175.75(3). The atom denoted “C(6a)” is related
to atom C(6) by the symmetry operation -x, y, 0.5 -z.
Table 1 Thermal analysis results for decomposition temperatures: all
temperatures in ◦C. Uncertainties are approximately 8 ◦
C
Compound
Tdecomp (onset) ◦
C
Tdecomp (peak) ◦
C
1M
2M
1P
392
398
382
391
426
432
418
422
2P
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Table 2 Optical gap of 1M–2M, 1P–2P and other related compounds
of 2.55 and 2.78 eV, observed for the corresponding polymers
containing the related non-fused and fused oligothiophene spacer
groups, and represents a red-shift of 0.05 eV and 0.28 eV,
respectively. Similarly, the optical gaps of the di-ynes 1M–2M are
lower compared to their counterparts containing the non-fused
and fused thiophene systems.12,30,31 Thus the electron-rich EDOT
spacers create stronger donor-acceptor interactions between the
Pt(II) centres and conjugated ligands compared to their non-fused
and fused counterparts.
Compound
Optical gap (eV)
1M
3.00
2.70
2.70
2.50
3.14
2.86
2.84
2.55
3.02
2.78
2M
1P
2P
Pt–thiophene di-yne30
Pt–thiophene poly-yne12
Pt–bithiophene di-yne32
Pt-bithiophene poly-yne12
Pt-thienothiophene di-yne12
Pt–thienothiophene poly-yne12
Conclusions
In summary, the present work has demonstrated that it is possible
to synthesize acetylide-functionalized heterocyclic ligands based
on EDOT spacer groups and incorporate them into platinum(II)
di-ynes and poly-ynes, by CuI catalysed dehydrohalogenation and
polycondensation reaction respectively. Dinuclear platinum(II)
complexes as well as polymeric materials with molar masses in the
range of 40,000–52,000 gmol-1 containing EDOT and bis-EDOT
spacer groups have been characterised by spectroscopic methods.
Attempts have been made to evaluate how the EDOT linker units
would influence the structural, thermal and optical properties of
the dimeric and polymeric organoplatinum(II) compounds. The re-
sults of optical absorption measurements reveal that the electron-
rich EDOT spacers create stronger donor-acceptor interactions
between the platinum(II) centres and conjugated ligands compared
to the non-fused and fused oligothiophene counterparts. The
EDOT spacer groups also have a significant effect on the thermal
stability of the dimeric as well as polymeric platinum(II) complexes.
The improved properties of the new materials have stimulated a
study of organometallic polymers containing a variety of hybrid
spacer groups based on EDOT systems and further investigation
of other properties (such as redox and photovoltaic properties)
of these p-conjugated organometallic systems and their organic
analogues are in progress.
di-ynes and the poly-ynes exhibit increasing thermal stability with
increasing size of the spacer group in the backbone. The di-ynes
1M–2M exhibit slightly higher onset and peak decomposition
temperatures than the corresponding poly-ynes 1P–2P. A similar
trend in thermal stability was previously observed among related
platinum(II) di-ynes and poly-yne compounds.20
Optical absorption spectroscopy
Optical absorption and emission spectra taken in thin films are
shown in Fig. 4. The first absorption band of 1P peaking at
2.90 eV has its origin in the p–p* transitions of the conjugated
polymer backbone and is associated with the first singlet excited
state S1.29 This band is red-shifted to 2.65 eV in 2P, indicating a
more conjugated backbone along the polymer chain. The optical
gaps (i.e., the onset of absorptions) of 1M–2M, 1P–2P and related
materials are shown in Table 2. The energy of the optical gap of
both the di-ynes and poly-ynes decreases in going from EDOT to
the bis-EDOT linker unit. We attribute the reduction in optical
gap to an increased delocalization of p electrons through the
more conjugated bis-EDOT spacer along the polymer backbone.
The optical gaps of the poly-ynes are lowered compared to the
corresponding di-ynes, indicating that the p conjugation of the
ligand extends into and through the metal centre. This finding is
consistent with our previous results on related systems.12,20
Experimental
General procedures
All reactions were performed under a dry nitrogen atmosphere
using standard Schlenk or glove box techniques.33 Solvents were
pre-dried and distilled before use by standard procedures.34 All
chemicals, except where stated otherwise, were obtained from
Sigma Aldrich and used as received. The compounds trans-
[(Ph)(PEt3)2PtCl],35 trans-[(PnBu3)2PtCl2],35 2,2¢-bis-EDOT36 and
2,2¢,5¢,2¢¢-ter-EDOT37 were prepared by adaptation of literature
procedures. The NMR spectra were recorded on a Bruker WM-
1
250 or AM-400 spectrometer in CDCl3. The 1H and 13C{ H} NMR
1
spectra were referenced to solvent resonances and 31P{ H}NMR
spectra were referenced to external trimethylphosphite. IR spectra
were recorded as CH2Cl2 solutions, in a NaCl cell, on a Perkin-
Elmer 1710 FT-IR spectrometer, mass spectra on a Kratos MS
890 spectrometer by the electron impact (EI) and fast atom
bombardment (FAB) techniques. Microanalyses were performed
in the Department of Chemistry, University of Bath. Preparative
TLC was carried out on commercial Merck plates with a 0.25 mm
layer of silica. Column chromatography was performed either
Fig. 4 Optical absorption spectra of Pt(II) di-ynes and poly-ynes (1 = 1M,
2 = 1P, 3 = 2M and 4 = 2P) taken at room temperature.
The optical gap of 1P is 2.70 eV, which compares to the gap of
2.86 eV observed for the corresponding polymer containing the
thiophene spacer group, and represents a red-shift of 0.16 eV.
The optical gap of 2P is 2.50 eV, which compares to gaps
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on Kieselgel 60 (230–400 mesh) silica gel or alumina (Brockman
Grade II–III).
Redcroft model STA-780 Simultaneous Thermal Analyser under
flowing N2. Sample masses were ~1 mg packed with ~1 mg Al2O3
in open Inconel crucibles. The reference crucible contained Al2O3.
Samples were heated at 10 ◦C min-1 to 485 ◦C. The thermocouple
readings were calibrated using a series of DTA standard materials:
KNO3, In, Sn, Ag2SO4, and K2SO4 as well as Pb and Al
as secondary standards, using the same heating rates as the
samples.
Molecular weight measurements
Molar masses were determined by GPC method38 using two PL
Gel 30 cm, 5 micron mixed C columns at 30 C running in THF at 1
cm3 min-1 with a Roth Mocel 200 high precision pump. A DAWN
DSP (Wyatt Technology) Multi-Angle Laser Light Scattering
(MALLS) apparatus with 18 detectors and auxiliary Viscotek
model 200 differential refractometer/viscometer detectors was
used to calculate the molecular weights (referred to as GPC LS).
X-ray crystallography
Data for 1a and 1M were collected on a Bruker Nonius Kappa
CCD diffractometer equipped with an Oxford Cryostream crystal
cooling apparatus, and using graphite monochromater Mo-Ka
radiation. Data for 2M was collected on Station 9.8 at the
SRS Daresbury synchrotron facility using a Bruker APEX II
diffractometer, also equipped with an Oxford Cryosystems crystal
cooling device. In all cases semi-empirical absorption corrections
based on inerframe scaling were applied. The structures were
solved using direct methods (SIR9239) and from subsequent
Fourier difference syntheses. The structures were refined by full-
matrix least-squares on F2 (SHELXL 9740). For 1a the hydrogen
atoms were located in the electron density difference map and
were allowed to refine freely. For 1M and 2M the hydrogen atoms
were placed in geometrically-idealised positions and refined using
a riding model. In 1M some of the ethyl groups displayed a
tendency to disorder, but the best refinement model was obtained
by using single sites with the carbon atoms assigned isotropic
displacement parameters. In 2 M the C(7) and C(8) atoms in
the EDOT ligand showed positional disorder over two sites.
The pairs of atoms were refined with the occupancies summed
to unity. The refinements were continued until convergence
was reached, and in the final cycles of refinement weighting
schemes were introduced which produced relatively flat analyses
of variance. Crystal data and refinement details are summarsied in
Table 3.
Optical spectroscopy
The dimeric and polymeric platinum(II) complexes were dissolved
in dichloromethane. Thin films were prepared on quartz substrates
using a conventional photoresist spin-coater. Typical film thick-
nesses were 100–150 nm as measured on a Dektak profilometer.
The optical absorption spectra were measured with a Hewlett-
Packard ultraviolet-visible (UV-VIS) spectrometer. Measurements
of photoluminescence (PL) were made with the sample in a
continuous-flow helium cryostat. The temperature was controlled
with an Oxford-Intelligent temperature controller-4 (ITC-4) and
was measured adjacent to the sample with a calibrated silicon
diode. For PL measurements, excitation was provided from a
continuous wave (cw) argon ion laser. The UV lines (334-365 nm)
of this laser were used for the compounds with benzene and
naphthalene spacers and 488 nm was used for the compounds
with the anthracene spacer. Typical intensities used were a few mW
mm-2. The emission spectra were recorded using a spectrograph
with an optical fibre input coupled to a cooled charge coupled
device (CCD) array (Oriel Instaspec IV).
Thermal analysis
Thermal analysis (differential thermal analysis, DTA, and ther-
mogravimetry, TG) was performed simultaneously in a Stanton–
Table 3 Crystal data and refinement parameters for 1a, 1M and 2M
Compound reference
1a
1M
2M
Chemical formula
Formula mass
C16H22O2SSi2
334.58
C46H74O2P4Pt2S
1205.17
Monoclinic
31.8940(3)
9.6610(1)
33.6030(4)
103.240(1)
10078.8(2)
150(2)
C2/c
8
Mo-Ka
0.71073
5.748
39442
9063
0.0602
0.0490
0.1194
0.0645
0.1287
1.043
C52H78O4P4Pt2S2
1345.32
Monoclinic
42.980(4)
13.4875(13)
9.8161(9)
101.078(1)
5584.3(9)
150(2)
C2/c
4
Synchrotron
0.6775
4.446
31903
8384
0.0978
0.0283
0.0722
0.0325
0.0738
0.976
Crystal system
Monoclinic
7.3848(4)
27.2437(12)
9.4632(6)
99.407(2)
1878.29(18)
150(2)
P21/a
4
Mo-Ka
0.71073
0.301
11695
4099
0.0583
0.0599
0.1168
0.1101
0.1406
1.050
˚
a/A
˚
b/A
˚
c/A
b (◦)
3
˚
Unit cell volume/A
T/K
Space group
No. of formula units per unit cell, Z
Radiation type
˚
Wavelength, l/A
Absorption coefficient, m/mm-1
No. of reflections measured
No. of independent reflections
Rint
Final R1 values (I > 2s(I))
Final wR(F2) values (I > 2s(I))
Final R1 values (all data)
Final wR(F2) values (all data)
Goodness of fit on F2
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Ligand synthesis
NMR (250 MHz, CDCl3): d = 4.27 (s, 8H,HEDOT), 6.83 (s, 2H,
Hterminal). 13C NMR (100.6 MHz, CDCl3): d 139.8, 85.5, 64.9.
EI-MS: m/z 282.3 (M+). Calc. for C12H10S2O4: C, 51.05; H, 3.57;
Found: C, 51.4; H, 3.60%.
The ligand precursors were synthesized by following a general
procedure outlined below for 1a and 1b.
2,5-Diiodo-3,4-ethylenedioxythiophene 1. A solution of 3,4-
ethylenedioxythiophene (2.8 g, 20.0 mmol) and iodine
monochloride–pyridine complex (11.5 g, 45.0 mmol) in
dichloromethane (75 mL) was stirred at room temperature for 1 h
during which time a precipitate of pyridinium salt was produced.
The precipitate was removed by filtration and the filtrate was
removed under reduced pressure. The solid residue was rinsed
with a mixture of water/methanol (1 : 1) and it was recrystallized
twice from propanone. The product was obtained as greenish-
white crystals (7.4 g, 93%). 1HNMR (400 MHz, CDCl3): d = 4.24
ppm (s, 4H, HEDOT). 13C NMR (100.6 MHz, CDCl3): d 54.08 (CH2),
64.84 (C2,5), 143.84 (C3,4), and EI-MS: m/z 393.7 (M+).
5,5¢-Diiodo-(2,2¢-bis-3,4-ethylenedioxythiophene) 2. Similar
method to the synthesis of 1 was applied but using 2,2¢-bis-
(3,4-ethylenedioxythiophene) instead. The title compound was
1
isolated as a dark-green crystalline solid in 85% yield. HNMR
(250 MHz, CDCl3) d = 4.27 (s, 8H, HEDOT). 13C NMR (100.6 MHz,
CDCl3): d 139.8, 85.5, 64.9. EI-MS: m/z 534.1 (M+). Calc. for
C12H8S2O4I2: C, 26.99; H, 1.51; Found: C, 27.09; H, 1.48%.
5,5¢-Bis(trimethylsilylethynyl)-2,2¢-bis-3,4-ethylenedioxythio-
phene 2a. Similar procedure to the synthesis of 1a was applied
using 2 (1.50 g, 2.8 mmol). 2a was isolated as a pale yellow solid
1
(1.1 g, 83% yield). IR(CH2Cl2): n cm-1 2135 (-C C-). H NMR
(250 MHz, CDCl3): d 4.22 ppm (s, 8H, HEDOT), 0.17 ppm (s, 18H,
HMe).13C NMR (100.6 MHz, CDCl3): d 139.0 (C3,4), 85.2 (C2,5)
and 65.1 (CH2), 106.23, 92.07 (C C), 0.17 (SiMe3). EI-MS: m/z
474.8 (M+). Calc. for C22H26Si2O4S2: C, 55.66; H, 5.52; Found: C,
55.90; H, 5.48%.
2,5-Bis(trimethylsilylethynyl)-3,4-ethylenedioxythiophene
1a.
i
To a deoxygenated solution of 1 (1.50 g, 3.80 mmol) in Pr2NH–
THF (50 mL, 1 : 1 (v/v)) under N2 was added a catalytic mixture
of CuI (12 mg), Pd(OAc)2 (11 mg) and PPh3 (65 mg). The
solution was stirred for 10 min at room temperature and then
trimethylsilylethyne (0.93 g, 9.5 mmol) was added. The reaction
temperature was then raised to 40 ◦C and the reaction was left
with stirring for 2 h. The reaction mixture was then allowed to
cool down to room temperature, filtered and the solvent mixture
was removed. The solid residue was purified by silica column
chromatography eluting with CH2Cl2/hexane (1 : 2 v/v). The
desired compound 1a was isolated as a light-yellow solid (1.1
g, 85% yield). IR(CH2Cl2): n cm-1 2141 (-C C-). 1H NMR
(250 MHz, CDCl3): d = 0.20 (s, 18H, HMe), 4.24 ppm (s, 4H,
HEDOT), 13C NMR (100.6 MHz, CDCl3): d 0.17 (SiMe3), 64.4
(CH2), 94.2 (C2,5), 99.97, 103.1 (C C), 143.8 (C3,4), and EI-MS:
m/z 334.4 (M+). Calc. for C16H22Si2O2S: C, 57.44; H, 6.63; Found:
C, 57.60; H, 6.70%.
5,5¢-Bis(ethynyl)-2,2¢-bis-3,4-ethylenedioxythiophene 2b. Simi-
lar procedure to that of 1b was applied using 2a (0.668 g,
1.41 mmol). 2b was isolated as a colorless microcrystalline solid
(0.37 g, 80% yield). IR(CH2Cl2): n cm-1 2107 (-C C-), 3298
(-C C–H). 1HNMR (250 MHz, CDCl3): d 4.24 ppm (s,
8H,HEDOT), 3.3 ppm (s, 2H, Hterminal). 13C NMR (100.6 MHz,
CDCl3): d 138.6 (C3,4), 85.2 (C2,5) and 64.5 (CH2), 106.23, 92.07
(C C). EI-MS: m/z 330.5 (M+). Calc. for C16H10O4S2: C, 58.17;
H, 3.05; Found: C, 58.30; H, 3.20%.
2,2¢,5¢,2¢¢-Ter-3,4-ethylenedioxythiophene. A solution of 3,4-
ethylenedioxythiophene (1.33 g, 9.37 mmol) in 50 mL THF under
◦
nitrogen was cooled to -78 C via a cooling bath. To the stirred
pre-cooled solution, (3.7 mL, 9.25 mmol) of nBuLi was added via
syringe. After 45 min the reaction mixture was allowed to warm
to 0 ◦C, then MgBr2. Et2O (2.50 g, 9.68 mmol) was added in
one portion. After 45 min, NiCl2·dppp (0.10 g, 0.187mmol) was
added followed by 2,5-diiodo-EDOT 1 (1.40 g, 3.56 mmol). The
mixture was allowed to warm slowly to room temperature. The
product was precipitated in water/pentane mixture and the title
compound was isolated as a medium brown solid (2.6 g, 65.5%).1H
NMR (250 MHz, CDCl3): d = 4.27 (s, 4H, H-4,5); 13C NMR
(100.6 MHz, CDCl3): d 139.8 (C3,4), 85.5 (C2,5) and 64.9 (CH2).
EI-MS: m/z 325 (M+).
2,5-Bis(ethynyl)-3,4-ethylenedioxythiophene 1b. 1a (0.668 g,
2.00 mmol) was dissolved in 30 mL THF. KOH (0.25 g, 4.4 mmol)
in water/methanol (20 mL, 1 : 3 v/v) was added and the solution
was stirred for one hour at room temperature. The solvent was then
removed and the residue was dissolved in CH2Cl2 and subjected
to a silica column chromatography. The desired compound was
collected with the aid of hexane/dichloromethane (1 : 1 v/v) to
afford 1b as a colorless microcrystalline solid (0.29 g, 78% yield).
1
IR(CH2Cl2): n cm-1 2107 (-C C-), 3300 (-C C–H). HNMR
(250 MHz, CDCl3): d 3.4 ppm (s, 2H, Hterminal), 4.20 ppm (s, 4H,
HEDOT). 13C NMR (100.6 MHz, CDCl3):d 64.5 (CH2), 95.2 (C2,5),
99.07, 106.23 (C C), 144.4 (C3,4) and EI-MS: m/z 190.3 (M+).
Calc. for C10H6O2S: C, 63.14; H, 3.18; Found: C, 63.20; H, 3.00%.
5,5¢¢-Diiodo -2,2¢,5¢,2¢¢-ter-3,4-ethylenedioxythiophene 3. Sim-
ilar method to the synthesis of 1 was applied using 2,2¢,5¢,2¢¢-
ter-3,4-ethylenedioxythiophene. Dark-green crystalline solid (83%
1
yield). HNMR (250 MHz, CDCl3): d = 4.300 (br, 12H, HEDOT).
2,2¢-Bis-(3,4-ethylenedioxythiophene). 3,4-Ethylenedioxythio-
phene 1 (5.00 g, 0.036 mol) in 170 mL THF was cooled to -78 ◦C
13C NMR (100.6 MHz, CDCl3): d 140.3, 139.20, 131.10, 128.64,
124.63, 124.02, 92.07, 85.2, 64.5. EI-MS: m/z 674.1 (M+). Calc.
for C18H12S3O6I2: C, 32.06; H, 1.79; Found: C, 32.11; H, 1.83%.
n
under N2. BuLi (1.6 M, 0.036 mol) was then added dropwise
and the solution was stirred for 45 min. After that CuCl2 (4.7 g,
0.036 mol) was added and the reaction mixture was left to stir at
40 ◦C for 2 h. The solution was allowed to cool down to room
temperature and the reaction was washed with water, solvent
was removed and the solid residue was purified by silica column
chromatography eluting with chloroform. The title compound
5,5¢¢-Bis(trimethylsilylethynyl)-2,2¢,5¢,2¢¢-ter-3,4-ethylenedioxy-
thiophene, 3a. Similar procedure to the synthesis of 1a was
applied using 3 (1.50 g, 2.23 mmol) instead. Pale yellow solid
1
(1.1 g, 83% yield). IR(CH2Cl2): n cm-1 2135 (-C C-). HNMR
(250 MHz, CDCl3): d 4.28 ppm (s, 12H, HEDOT), 0.16 ppm (s, 18H,
HMe).13C NMR (100.6 MHz, CDCl3): d 139.0 (C3,4), 85.0 (C2,5)
1
was isolated as a white crystalline solid (6.73 g, 68% yield). H
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and 66.7 (CH2), 105.0, 91.0 (C C), 0.22 (SiMe3). EI-MS: m/z
614.9 (M+). Calc. for C28H30Si2O6S3: C, 54.68; H, 4.93; Found: C,
55.07; H, 5.05%.
H
P–CH2), 2.20 (br, 12H, HCH2), 1.52 (sextet, 12H, HCH2), 0.90 (t,
1
18H, HCH3). 13C{ H} NMR (100 MHz, CDCl3): d 156.74, 139.19,
138.41, 128.76 (Arom.), 121.62 (C C), 26.05–24.26, 13.83 (alkyl).
31P{ H}NMR (101.3 MHz, CDCl3): d -138.03,1JPt–P = 2363 Hz.
1
5,5¢¢-Bis(ethynyl)-2,2¢,5¢,2¢¢-ter-3,4-ethylenedioxythiophene 3b.
Similar procedure to that of 1b was applied using 3a (0.867 g,
1.41 mmol), KOH (0.25 g, 4.4 mmol) in THF/methanol (30 mL,
5 : 1,v/v). The product decomposed to a black solid during work-
up and isolation.
Calc. for (C34H58SO2P2Pt)n: C, 51.83; H, 7.42. Found: C, 51.94; H,
7.45%. GPC (THF): Mn = 30,500 (n = 66), Mw = 52,008 gmol-1
gmol-1, PDI = 1.7.
trans-[(Bu3P)2Pt–C C–R–C C-]n (R = 2,2¢-bis-3,4-ethylene-
dioxythiophene-5,5¢-diyl) 2P. Similar procedure to the synthesis
of 1P was applied using 2b (0.155 g, 0.470 mmol), trans-
[(PBu3)2PtCl2] (0.315 g, 0.47 mmol) in THF/iPr2NH (50 mL, 1 : 1
v/v) and CuI (5 mg) under N2. 2P was isolated in (0.26 g, 70%
yield). Further purification was accomplished by precipitating the
polymer solution from CH2Cl2 into methanol. IR(CH2Cl2): n cm-1
2085 (–C C–). 1H NMR (250 MHz, CDCl3): d 5.20 ppm (s, 8H,
HEDOT), 2.0 ppm (t, 12H, HP–CH2), 1.50 ppm (tt, 12H, HP–CH2),1.30
Synthesis of Pt(II) di-ynes
trans-[(Ph)(Et3P)2Pt–C C–R–C C–Pt–(PEt3)2Ph] [R = 3,4-
ethylenedioxythiophene-2,5-diyl) 1M. 1b (0.0448 g, 0.2358mmol)
and trans-[Pt(PEt3P)2Cl2](0.2816 g, 0.5187 mmol) were dissolved
in CH2Cl2/iPr2NH (50 mL,1 : 1, v/v) under nitrogen. A catalytic
amount of CuI (~5 mg) was added and the solution was stirred at
room temperature for 15 h, after which all volatile components
were removed under reduced pressure and the residue was
dissolved in CH2Cl2, passed through a silica column eluting
with hexane/CH2Cl2 (1 : 1, v/v). Removal of the solvents under
reduced pressure gave the title compound as a pale yellow solid
(0.21 g, 75%). IR(CH2Cl2): n cm-1 2080 (C C). 1H NMR
(250 MHz,CDCl3): d = 7.21 ppm (d, 4H, Hortho of Ph), 6.89 ppm
(dd, 4H, Hmeta of Ph), 6.75 ppm (dd, 2H, Hpara of Ph), 4.20 ppm (s,
4H, HEDOT), 1.65 ppm (q, 24H, HP—CH2), 1.00 ppm (t, 36H, HP—CH3).
13C NMR (100.6 MHz, CDCl3): d 156.74, 139.19, 138.41, 128.76,
127.14, 122.47, 122.29 (Arom.) 107.95, 108.56 (C C), 15.02, 7.99
ppm (qt, 12H, HP–CH2), 0.85 ppm (t, 18H, HP–CH3). 31P{ H}NMR
1
(101.3 MHz, CDCl3): d -137.5. Calc. for (C40H62S2O4P2Pt)n: C,
51.77; H, 6.73. Found: C, 51.83; H, 6.80%. GPC (THF): Mn =
29,556 gmol-1 (n = 44), Mw = 40,836 gmol-1, PDI = 1.4.
Acknowledgements
We acknowledge Sultan Qaboos University (SQU) for the Re-
search Grant No. IG/SCI/CHEM/09/02 and for research leave
for MSK. We are grateful to the British Council for a PMI Grant
(GS 216) that has supported MSK, MKA-S, HHS and PRR.
PRR gratefully acknowledges support from the EPSRC through
the award of a Senior Fellowship.
1
(Et). 31P { H} NMR (100 MHz, CDCl3): d -138.07,1JPt–P = 2645
Hz. FAB-MS: m/z 1205 (M+). Calc. for C46H74SO2P4Pt2: C, 45.84;
H, 6.19. Found: C, 45.90; H, 6.30%.
trans-[(Ph)(Et3P)2Pt–C C–R–C C–Pt–(PEt3)2Ph] [R = 2,2¢-
bis-3,4-ethylenedioxythio-phene-5,5¢-diyl) 2M. Similar proce-
dure to the synthesis of 1M was applied using 2b (0.090 g,
0.272 mmol), trans-[(PEt3)2(Ph)PtCl] (0.50 g, 0.92 mmol) in
iPr2NH/CH2Cl2 (50 mL, 1 : 1 v/v) and CuI (5 mg). 1M was isolated
as a pale yellow solid (0.30 g, 58% yield). IR(CH2Cl2): n cm-1 2135
(–C C–). 1H NMR (250 MHz, CDCl3): d 7.25 ppm (d, 4H, Hortho
of Ph), 6.90 ppm (dd, 4H, Hmeta of Ph), 6.70 ppm (dd, 2H, Hpara of
Ph), 4.20 ppm (s, 8H, HEDOT), 1.65 ppm (q, 12H, HP–CH2), 1.00 ppm
(t, 36H, HP–CH3). 13C NMR (100 MHz, CDCl3): d 140.4, 139.4,
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iPr2NH/CH2Cl2 (25 mL,1:1,v/v) was added CuI (5mg). The
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1
tion from CH2Cl2 into methanol. IR(CH2Cl2): n cm-1 2088. H
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