Synthesis, characterisation and optical spectroscopy of diynes and poly-ynes containing derivatised fluorenes in the backbone

Article abstract of DOI:10.1039/b208963g

A series of trimethylsilyl-protected and terminal mono- and bis-alkynes based on 9,9-dioctylfluorene, 2-(trimethylsilylethynyl)-9,9-dioctylfluorene la, 2-ethynyl-9,9-dioctylfluorene 1b, 2,7-bis(trimethylsilylethynyl)-9,9-dioctylfluorene 2a, 2,7-bis(ethynyl)-9,9-dioctylfluorene 2b, have been synthesised. Reaction of trans-[(PⁿBu₃)₂PtCl₂] with 2 equivalents of the terminal ethyne 1b yields the mononuclear platinum(II) diyne 3, reaction of trans-[(Ph)(Et₃P)₂PtCl] with 0.5 equivalents of the diterminal ethyne 2b gives the dinuclear platinum(II) diyne 4 while 1 : 1 reaction between trans-[(PⁿBU₃) ₂PtCl₂] and 2b gives the platinum(II) poly-yne 5. Treatment of 2,5-dioctyloxy-1,4-diiodobenzene with 1b in 1 : 2 stoichiometry produces the organic di-yne 6 while 1 : 1 reaction between 2,5-dioctyloxy-1,4-diiodobenzene and 2b, 2,7-bis(ethynyl)fluorene or 2,7-bis(ethynyl)fluoren-9-one produces the organic co-poly-ynes 7-9. All the new materials have been characterised by analytical and spectroscopic methods and the single crystal X-ray structures of 2a and 3 have been determined. The diynes and poly-ynes are soluble in organic solvents and are readily cast into thin films. Optical spectroscopic measurements reveal that the attachment of octyl side-chains on the fluorenyl spacer reduces inter-chain interaction in the poly-ynes while a fluorenonyl spacer creates a donor-acceptor interaction along the rigid backbone of the organometallic poly-ynes and organic co-poly-ynes. The Royal Society of Chemistry 2003.

Full text of DOI:10.1039/b208963g

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Synthesis, characterisation and optical spectroscopy of diynes and
poly-ynes containing derivatised fluorenes in the backbone
Muhammad S. Khan,*a Muna R. A. Al-Mandhary,a Mohammed K. Al-Suti,b Birte Ahrens,b
Mary F. Mahon,b Louise Male,b Paul R. Raithby,*b Clare E. Boothbyc and Anna Köhler*c
a Department of Chemistry, Sultan Qaboos University, P.O. Box 36, Al Khod 123,
Sultanate of Oman. E-mail: msk@squ.edu.om
b Department of Chemistry, University of Bath, Claverton Down, Bath, UK BA2 7AY.
E-mail: p.r.raithby@bath.ac.uk
c Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge, UK CB3 0HE
Received 17th September 2002, Accepted 24th October 2002
First published as an Advance Article on the web 25th November 2002
A series of trimethylsilyl-protected and terminal mono- and bis-alkynes based on 9,9-dioctylfluorene, 2-(trimethyl-
silylethynyl)-9,9-dioctylfluorene 1a, 2-ethynyl-9,9-dioctylfluorene 1b, 2,7-bis(trimethylsilylethynyl)-9,9-dioctyl-
fluorene 2a, 2,7-bis(ethynyl)-9,9-dioctylfluorene 2b, have been synthesised. Reaction of trans-[(PnBu3)2PtCl2] with 2
equivalents of the terminal ethyne 1b yields the mononuclear platinum() diyne 3, reaction of trans-[(Ph)(Et3P)2PtCl]
with 0.5 equivalents of the diterminal ethyne 2b gives the dinuclear platinum() diyne 4 while 1 : 1 reaction between
trans-[(PnBu3)2PtCl2] and 2b gives the platinum() poly-yne 5. Treatment of 2,5-dioctyloxy-1,4-diiodobenzene with 1b
in 1 : 2 stoichiometry produces the organic di-yne 6 while 1 : 1 reaction between 2,5-dioctyloxy-1,4-diiodobenzene
and 2b, 2,7-bis(ethynyl)fluorene or 2,7-bis(ethynyl)fluoren-9-one produces the organic co-poly-ynes 7–9. All the new
materials have been characterised by analytical and spectroscopic methods and the single crystal X-ray structures of
2a and 3 have been determined. The diynes and poly-ynes are soluble in organic solvents and are readily cast into thin
films. Optical spectroscopic measurements reveal that the attachment of octyl side-chains on the fluorenyl spacer
reduces inter-chain interaction in the poly-ynes while a fluorenonyl spacer creates a donor–acceptor interaction along
the rigid backbone of the organometallic poly-ynes and organic co-poly-ynes.
donor–acceptor architectures are currently of interest because
Introduction
the intra-molecular charge transfer can facilitate ready manipu-
In recent years there has been a considerable interest in the
lation of the electronic structure (HOMO–LUMO levels), lead-
optoelectronic properties of conjugated polymers.1,2 Many
ing to small band gap semi-conducting polymers23 or materials
potential applications such as nonlinear optics, electrolumines-
with enhanced third-order nonlinear optical properties.24 The
cence, optical information storage, etc., using conjugated poly-
donor–acceptor interaction in fluorene-based platinum() poly-
mers have been proposed.3 Among the variety of conjugated
polymers that are now studied, poly(arylene ethynylene) type
ynes and organic co-poly-ynes may impart interesting materials
properties to such polymeric systems.The fluorene structural
polymers (PAEs) and metal poly-yne polymers have been the
moiety provides a rigidly planar biphenyl unit within the poly-
focus of much research with regard to the development of
mer backbone and facile functionalisation at C-9, the latter
optoelectronic devices.4 Of particular interest are a series of
offering the prospect of improving both polymer processability
PAEs that have been employed in successful liquid crystal
and mediating potential inter-chain interactions in films.25
display and photocell technology.5,6 Platinum acetylide-based
There is also considerable interest in the solid-state structures
of the polymeric materials because of evidence for inter-chain
interactions that influence their optoelectronic properties. In
this context an analysis of intermolecular interactions in the
π-conjugated polymers have provided model systems to explain
the electronic properties of conjugated organic polymers7 used
in light emitting diodes (LEDs),8 lasers,9 photocells,10 and field-
effect transistors (FETs).11 The inclusion of heavy transition
crystal structures of the ligand precursors and of model com-
metals such as platinum in the polymer backbone introduces
plexes may lead to a better understanding of the interactions in
sufficient spin–orbit coupling to allow light emission from the
the polymers.26 With these ideas in mind we have been inter-
triplet excited state of the conjugated ligand.12–14 For com-
ested in the chemistry and photophysics of new platinum()
poly-yne incorporating fluorene-based auxiliaries. A few recent
mercial exploitation of these materials and for direct appli-
cation-oriented synthesis, a thorough understanding of the
structure–property relationship is necessary such that suitable
modification of the chemical structure may fine-tune the opto-
electronic properties of the polymers.
Recently we reported a series of platinum() poly-ynes where
the bridging alkynyl units are separated by a variety of carbo-
reports have concerned the incorporation of fluorene-based
auxiliaries into conjugated poly-yne frameworks.27
In this paper, we report the synthesis and characterisation of
mono- and bis-(ethynyl)-9,9-dioctylfluorene derivatives 1a,b,
and 2a,b, and the incorporation of 2b into the new rigid-rod
platinum() poly-yne 5 (Chart 1). In order to evaluate the role
of the platinum() centres and to undertake a systematic study
of the optoelectronic properties of the poly-ynes, a series of
cyclic and heterocyclic spacers (e.g., oligothienyl, oligopyridyl,
thienyl-pyridine, phenylene, etc.).13,15–17 The platinum centre is
electron rich compared to the conjugated ligands and the metal-
phosphine fragment acts as an electron donor within the poly-
mer.12,18,19 In a comparative series of studies we have shown that
when the 2,5-dioctyloxy-1,4-phenylene unit replaces the plat-
inum-phosphine group it acts as a donor and readily couples to
acceptor units via alkynyl bridges.20 In contrast, fluorenes are
widely used as electron acceptors in charge transfer complexes21
and electron transport materials.22 π-Conjugated polymers with
Chart 1 The numbering scheme for 9,9-dioctylfluorene.
D a l t o n T r a n s . , 2 0 0 3 , 7 4 – 8 4
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 3
74

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i
᎐
Scheme 1 i Me3SiC᎐CH, CuI, Pd(OAc)2, PPh3, Pr2NH, THF; ii KOH, MeOH, THF.
᎐
organic co-poly-ynes 7–9 that contain derivatised fluorene
9,9-dioctylfluorene 2b was accomplished by cleavage of the
groups in the backbone have also been synthesised. In addition,
the synthesis and characterisation of the model diyne com-
pounds 3, 4 and 6 is reported. Diynes can be considered as
building blocks for the high molecular weight polymers and
valuable information concerning their molecular and electronic
properties can be obtained through the studies of these model
compounds. Recently, attention has also been directed towards
linear π-conjugated dimers and oligomers, taken not only as
model compounds, but also as efficient molecular wires in elec-
tronic applications.28 Diynes are often more crystalline than the
corresponding poly-ynes, allowing for a detailed structural
analysis and, thus, an assessment of the structure–electronic
property relationship.29 The structural characterisation of
a fluorene-based ligand precursor 2a and of a mononuclear
platinum() σ-acetylide complex 3 are reported. The opto-
electronic properties of the new materials are described and
compared with related organometallic and organic polymers.
trimethylsilyl protecting group with dilute aqueous KOH in
MeOH–THF (Scheme 1). The products were purified by silica
gel column chromatography and isolated as off-white to light
yellow solids or colourless liquids in yields of 75–85%. The new
terminal mono- and bis-alkynes are stable in air and light and
were characterised by IR, NMR (1H and 13C) spectroscopy, EI
mass spectrometry as well as by satisfactory elemental analyses.
The complex trans-[(PnBu3)2PtCl2] was reacted with two
i
equivalents of 1b in Pr2NH–THF, in the presence of CuI at
room temperature to afford the mononuclear platinum() diyne
complex 3 (Scheme 2).
Results and discussion
Syntheses
The key starting materials for the alkynyl ligand precursors,
2-bromo-9,9-dioctylfluorene and 2,7-dibromo-9,9-dioctyl-
fluorene were prepared by adaptation of literature procedures
involving alkylation of 2-bromofluorene and 2,7-dibromo-
fluorene with 1-bromooctane in a two-phase system using
tetra(n-butyl)ammonium bromide as the phase-transfer
catalyst.30,31 The trimethylsilyl-protected alkynyl ligand
precursors, 2-(trimethylsilylethynyl)-9,9-dioctylfluorene 1a
and 2,7-bis(trimethylsilylethynyl)-9,9-dioctylfluorene 2a were
prepared by improved procedures involving a palladium()/
copper()-catalysed cross-coupling reaction of 2-bromo-9,9-di-
octylfluorene and 2,7-dibromo-9,9-dioctylfluorene with
trimethylsilylethyne in diisopropylamine/THF as illustrated
in Scheme 1.32 The protected alkynes 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 and
single crystal X-ray structure determination for 2a. Conversion
of the protected ligands into their terminal mono- and bis-
alkynes, 2-ethynyl-9,9-dioctylfluorene 1b and 2,7-bis(ethynyl)-
Scheme 2 i trans-[Pt(PnBu3)2Cl2], CuI, iPr2NH, CH2Cl2.
The reaction of trans-[(Ph)(Et3P)2PtCl] with 2b (2 : 1 stoichio-
metry) gave the dinuclear platinum() diyne 4 while the
dehydrohalogenation polycondensation reaction between
trans-[(PnBu3)2PtCl2] and 2b (1 : 1 stoichiometry) under similar
conditions readily afforded the platinum() poly-yne
(Scheme 3).
5
D a l t o n T r a n s . , 2 0 0 3 , 7 4 – 8 4
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Scheme 4 i 21b, CuI, Pd(OAc)2, PPh3, iPr2NH, THF; ii 2b/bis(ethynyl)-
fluorene/fluorenone, CuI, Pd(PPh3)4, iPr2NH, THF.
by its typical absorptions at 2210 and 2202 cmϪ1. Following the
cross-coupling polycondensation reaction, the νC᎐C band of the
terminal alkynes 1b and 2b at 2107–2110 cmϪ1 is shifted to a
higher frequency by about 100 cmϪ1, consistent with the known
Scheme
3
i
2[Pt(PEt3)2(Ph)Cl], CuI, iPr2NH, CH2Cl2; ii trans-
᎐
trend that disubstituted alkynes R–C᎐C–RЈ display a ν
C᎐C band
᎐
᎐
᎐
[Pt(PnBu3)2Cl2], CuI, iPr2NH, CH2Cl2.
at a frequency higher than that of monosubstituted alkynes
34
᎐
RC᎐C–H. The IR spectra of the mononuclear platinum()
᎐
The synthesis of platinum() fluorene-poly-yne 11 and
platinum() fluorenone-poly-yne 12 has been reported
previously.27a Reaction of 2,5-dioctyloxy-1,4-diiodobenzene
diyne 3, dinuclear platinum() 4 and platinum() poly-yne 5
display a single sharp νC᎐C absorption at around 2095 cmϪ1 con-
᎐
sistent with a trans-configuration of the ethynyl ligands around
the platinum() centre. The platinum() diynes and poly-yne
display lower νC᎐C values than those of the organic diyne and
poly-ynes by about 110 cmϪ1, which is attributed to a metal-to-
alkynyl ligand charge transfer process.35 The 1H and 13C NMR
spectra of all the compounds exhibit the expected signals for
the systems including appropriate resonances for the backbone
ethynylene carbons. The peak area ratios in the 1H NMR
spectra agree with the feed mole ratio of the precursors for the
diynes and poly-ynes. The single resonance in the 31P NMR
spectra of the platinum() diynes and poly-yne confirms the
trans arrangement of the phosphine ligands. From the 31P-{1H}
i
with 1b (1 : 2 stoichiometry) in Pr2NH–THF gave the organic
diyne 6 while the reaction between 2,5-dioctyloxy-1,4-diiodo-
benzene and 2b, bis(ethynyl)fluorene or bis(ethynyl)fluorenone
(1 : 1 stoichiometry) produced the organic co-poly-ynes 7–9
(Scheme 4). The poly-ynes were obtained in yields over 90%,
pointing to a very high conversion. The model diyne com-
pounds 3, 4 and 6 were synthesised to control the reaction
conversion and to facilitate spectroscopic and photophysical
characterisation of the poly-ynes. Standard palladium-
catalyzed acetylene coupling (Sonogashira–Hagihara) method-
ologies were employed in the synthesis of the organic diynes
and poly-ynes.32c The reaction conditions typically used
involved stirring a mixture of the diiodo- and diethynyl-
fluorene precursors and catalyst in diisopropylamine–THF
(1 : 4, v/v) for 20 h at a temperature of 70 to 80 ЊC. The solvent
mixture was degassed by passing argon through the solution for
1 h prior to the start of the reaction, with the aim of excluding
the Cu()-catalyzed oxidative coupling of terminal bis-alkynes33
which may compete with the desired cross-coupling or poly-
condensation reaction. The polymers remained in solution
during the reaction, with the help of the octyloxy and octyl
side-groups. They were isolated by precipitation into methanol.
Purification of diynes 3, 4, 6 and organic poly-ynes 7–9 was
accomplished by silica column chromatography while the
platinum() poly-yne 5 was purified by chromatography on an
alumina column.
1
NMR spectral data, it is clearly seen that the JPt–P coupling
constants for the diynes 3, 4 are larger than those of the poly-
yne 5 by about 300 Hz. The spectral features of the diyne
and poly-yne 3–5 are similar to other platinum() diynes and
poly-ynes previously reported,13,15–17,19 and confirm the all-trans
configuration of the complexes.
The mass spectrometric results confirm the molecular
assignments for the organic ligands and the platinum() diynes.
Gel permeation chromatography (GPC), using a polystyrene
(PS) calibration shows that the number-average molecular
weights of the poly-ynes are in the range of 9500–43500 g
molϪ1, corresponding to degrees of polymerisation between 17
and 42. The polydispersity (PDI) varied between 1.6 and 1.9.
The narrow polydispersity (PDI < 2) in molecular weights is
consistent with the proposed linear structure36 from the con-
densation polymerisation. The molecular weights should be
treated with caution in view of the difficulties associated
with utilising GPC for rigid-rod 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 those of flexible
Spectroscopic characterisation
Systematic characterisation of the diynes and poly-ynes was
achieved by spectroscopic methods (IR, 1H, 13C and 31P NMR).
The IR spectra of the organic diyne 6 and poly-ynes 7–9 pro-
᎐
vided clear evidence for the presence of the C᎐C bond, detected
᎐
D a l t o n T r a n s . , 2 0 0 3 , 7 4 – 8 4
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polymers. Therefore, calibration of the GPC with PS standards
is likely to 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 there is high degree
of polymerisation in these poly-ynes.
The low-temperature emission spectra of platinum() diynes
and poly-ynes typically show two emission bands, a fluor-
escence band just below the absorption band and a phosphor-
escence band about 0.7 eV lower.14–21 However, for the 9,9-di-
octylfluorene spacer used here, fluorescence can be seen in the
platinum()-poly-yne 5 at about 3.0 eV but not in the plat-
inum() diynes 3 and 4. The low-temperature phosphorescence
spectra are dominated by a strong, narrow peak around 2.2–2.3
eV. For the mononuclear diyne 3, there is an additional peak at
2.5 eV that disappears above 75 K. The fact that this peak has a
different temperature dependence from the remainder of the
band, coupled with the fact that it is not present in the dinuclear
platinum() diyne 4 and the platinum() poly-yne 5, suggest
that it may have a different electronic origin that could be
related to the relative orientations of rings along the chains.
Recent research on poly-9,9-dioctylfluorene (PF8) 10 shown in
Chart 2 has identified two electronic singlet S1 states separated
by about 0.1 eV,25 which are assigned to two different phases of
the homo-polymer. Further research will be needed to clarify
whether in the mononuclear diyne 3 two separate triplet states
are also caused by particular thin film morphologies.
Optical spectroscopy
The thin film absorption and emission spectra of the mono-
nuclear platinum() diyne 3, the dinuclear platinum() diyne 4
and the platinum() poly-yne 5 are compared in Fig. 1(a). In
Apart from this peak and the loss of vibronic structure, the
room-temperature spectra are similar. In contrast to the diynes
3 and 4, the phosphorescence of the poly-yne 5 is about three
orders of magnitude lower at 290 K than at 10 K. This increase
in non-radiative decay with temperature can be attributed to
thermally activated diffusion of triplet excitons along the
polymer chain, which can lead to triplet–triplet annihilation or
an increased sampling of dissociation sites or non-radiative
sites.
In Fig. 1(b), the absorption and emission spectra of the
organic diyne 6 and the organic poly-yne 7 are compared. The
0–0 peak of the absorption spectrum shifts by about 0.3 eV to
the red from the diyne 6 to the poly-yne 7, which is the same
shift as that observed for the platinum compounds and further
supports the fact that the platinum compounds are well-conju-
gated even through the metal site. Because there is no metal-
induced spin–orbit coupling in these organic analogues, only
fluorescence can be seen. The 0–0 emission peak at 2.90 eV in
the 10 K spectrum of the diyne 6 shifts to 2.71 eV in the poly-
yne 7. As for the analogous mononuclear platinum() diyne 3 a
high energy emission peak in the organic diyne 6 is observed at
3.2 eV. Taking the red-shift between diyne and poly-yne into
account, this feature would be expected to appear at about 2.9–
3.0 eV in the poly-yne, yet as in platinum() poly-yne 5, there is
no such emission at that energy.
In order to make a systematic study of the optoelectronic
properties of the poly-ynes the materials to be investigated have
been extended to form the set shown in Chart 2 including the
related compounds 10, 11 and 12. This set allows a comparison
to be made between the platinum() poly-ynes and the organic
co-poly-ynes, in addition to a study the effect of substitution at
C-9.
The absorption and room temperature photoluminescence
(PL) spectra of the organic and platinum() poly-ynes are
shown in Fig. 2. The related homo-polymer 10 is included in
Fig. 2 (a and b) to facilitate a comparison with the platinum()
poly-ynes. The platinum() poly-ynes 5 and 11 both show two
emission bands, one centred around 2.95 eV and one centred
around 2.2 eV. At room temperature, the lower-energy band is
more pronounced for 11 than for 5. The positions of the high-
energy emission band and of the first absorption band are
slightly blue-shifted (by 0.05 eV) with respect to the organic
polymer 10. The vibronic peaks in emission shifts, so that the
0–0 peak is now the main peak rather than a shoulder as in 10.
This is typical for platinum()-poly-ynes.19 The absorption and
emission of the platinum() fluorenone poly-yne 12 are shifted
by 0.7 eV with respect to 10. As for the organic analogue 9, the
emission is unstructured at room temperature. The first
absorption band centred at 2.5 eV is of much lower intensity
Fig. 1 Absorption spectra at 290 K (dotted line) and emission spectra
at 290 K (dotted line) and at 10 K (solid line) taken from thin films. (a)
platinum() diynes 3 and 4 and platinum() poly-yne 5 as indicated in
the figure. (b) Organic diyne 6 and organic co-poly-yne 7 as indicated in
the figure.
similar compounds14–21 the transitions giving rise to the first
absorption band have a strong π–π* character due to mixing
particularly between the platinum 6p orbitals and the π*
orbitals of the ligand.
In Fig. 1(a), the peak of the first absorption band shifts by
about 0.3 eV to the red from 3 to 5 which indicates an increase
in conjugation. This suggests that the singlet excited state S1 can
extend through the platinum() site.
D a l t o n T r a n s . , 2 0 0 3 , 7 4 – 8 4
77

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Chart 2 The chemical structures and compound numbers of the platinum() and analogous organic poly-ynes.
than the second absorption band centred at 3.2 eV. The photo-
luminescence quantum yields measured at room temperature
those in the range 100–10 K. The emission of the platinum()
fluorenone poly-yne 12 shows only a slight red-shift and an
increased structure at lower temperature.
for these four polymers are: 10 (60
20)% (as before); 5
(0.6 0.2)%; 11 (0.4 0.2)%; 12 (0.4 0.2)%.
Previous studies14,19 have shown that the inclusion of a heavy
transition metal, such as platinum, into the backbone of an
organic poly-yne increases spin–orbit coupling so that triplet
state emission (phosphorescence) can be observed. The T1
triplet state is typically found to be 0.7 0.1 eV below the S1
singlet state. Comparison of the organic co-poly-ynes 7 and 8
with the platinum() poly-ynes 5 and 11 (Fig. 2) shows that this
is also the case here. The low energy emission in 5 and 11 has a
strong temperature dependence and a high degree of vibronic
structure at low temperature, and is 0.7 eV below the S1 singlet
emission (fluorescence) for both polymers. Thus by comparison
with other similar polymers this emission is assigned to the T1
triplet state (phosphorescence). The strong spin–orbit coupling
induced by the platinum atoms causes strong inter-system cross-
ing from the S1 state to the T1 state. Since the non-radiative
decay rate from the T1 triplet state is equal or larger than the
radiative decay rate14 the PL quantum efficiencies of the plat-
inum() poly-ynes are reduced from those observed for the
organic polymers.
By comparing polymer 7 with 8, and 5 with 11, the effect of
side-chains on the emission and absorption spectra can be
studied, since the main backbone, which determines the intra-
chain properties of the polymers, is the same in each of these
pairs. The loss of vibronic structure even at low temperature in
8 compared to 7 [Fig. 2(b)] along with the reduction of PL
quantum yield by a factor of 10 and the associated red-shift all
point to a strong inter-chain interaction. We therefore attribute
the emission in 8 to inter-chain excited states such as excimers
or aggregates.
The absorption and PL spectra of the organic co-polymers
are shown in Fig. 2(b). When moving from the homopolymer
10 to the copolymer 7 a small red-shift of 0.15 eV in the onset
of absorption and photoluminescence and an increased
vibronic structure in the first absorption band is observed.
Omitting the alkyl side-chains at C-9 as for fluorenyl co-poly-
yne 8 leads to an increased red-shift of 0.5 eV of absorption
and emission with respect to 10 and to a loss of vibronic
structure in emission. The emission from the fluoren-9-onyl
co-poly-yne 9 obtained by derivatisation at C-9 of the fluorene
ring is similarly unstructured and further red-shifted with
respect to 10 (by 0.7 eV) and it has a pronounced low-energy
shoulder in the absorption. The thin film PL quantum yield
efficiencies measured at room temperature for these four
polymers are: 10 (60
20)%; 7 (30
10)%; 8 (3
1)%; 9
(3 1)%.
It is instructive to consider the temperature dependence of
PL for the seven polymers studied. For 10, the intensity of the
first vibronic peak increases with decreasing temperature. This
is accompanied by an overall red-shift of the emission. These
same trends are also observed for the co-poly-yne 7. The other
two co-poly-ynes, 8 and 9, show hardly any change in emission
with temperature except for a slight red-shift at low temper-
ature. For the platinum() poly-ynes 5 and 11 the intensity of
the low-energy band increases by almost three orders of
magnitude with decreasing temperature, and the intensity
of the high-energy band increases by up to one order of
magnitude as shown in Figs. 2 (c) and (d). The lower-energy
emission also shows a well-resolved vibronic structure at low
temperature. For 5, the relative weights of the vibronic bands
remain constant with temperature, only the resolution
improves, while for 11, the spectral shape of the emission
changes between the spectra at 300 and 200 K and compared to
Similarly, the vibronic structure at 300 and 200 K for 11 [Fig.
2(d)] is different from that in 5 [Fig. 2(c)], which could indicate
inter-chain interactions. Such interactions will be weaker here
than in 8 as the butyl side-chains on the Pt atoms help to
decrease aggregation effects.
D a l t o n T r a n s . , 2 0 0 3 , 7 4 – 8 4
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Fig. 2 Absorption spectra at 290 K (dotted line) and emission spectra at 290 K (dotted line) and at 10 K (solid line) taken from thin films for (a)
platinum() poly-ynes 5, 11, 12 and (b) organic co-poly-ynes 7, 8, 9. The spectra for 10 are included in both panels for comparison. All spectra show
the correct relative emission intensities except in the case of compounds 5 (and 11) which are normalised to unity at the emission peak. The emission
spectra with the correct relative emission intensities at 290, 200, 100, 50 and 10 K for compounds 5 and 11 are shown in (c) and (d), respectively, on a
logarithmic scale.
For both the organic co-poly-ynes and the platinum() poly-
ynes, the inclusion of a fluorenonyl unit in the backbone causes
a significant red-shift in the absorption and emission spectra
from the fluorene-containing polymers [compare 10 with 9 in
Fig. 2(b); 10 with 12 in Fig. 2(a)]. This points to a strong
donor–acceptor interaction between the electron-donating Pt
fragment and the electron-accepting fluorenone spacer. The low
intensity of the first absorption band is consistent with the
charge-transfer nature of this transition.19
studies the molecular geometry of the backbone is very similar
to that of the unsubstituted compound 2,7-bis(trimethyl-
silylethynyl)flourene.27a Selected bond parameters are presented
in Table 1. The central fluorenyl unit is essentially planar, with
᎐
the linear Me SiC᎐C groups occupying the 2 and 7 positions.
᎐
3
The geometry about the Si atoms is distorted tetrahedral, and
the two carbon–carbon triple bonds have an average C–C dis-
tance of ca. 1.21 Å, typical for that found in terminal
acetylides.37 In 2a the two octyl groups lie on opposite sides of
the plane of the fluorenyl unit, and while one chain extends
perpendicular to the central backbone the other chain bends
around to lie close to the SiMe3 group centred on Si(2). Both
the chains and the trimethylsilyl groups are subject to consider-
able positional disorder and the structure was modelled using
two sites for the silicon atoms and the majority of the carbon
atoms in the chains, with the occupancies summing to unity. It
is this disorder that is responsible for the relatively high residual
R factor at the end of the structure refinement process; however,
the overall molecular conformation has been established
unambiguously.
Crystal structure determinations of 2a and 3
In order to underpin the spectroscopic characterisations of the
polymer precursors attempts were made to grow single crystals
suitable for X-ray diffraction studies on a number of the key
molecules along the reaction route to polymer formation.
These attempts were successful for compounds 2a and 3, and
single-crystal X-ray analyses were undertaken.
The molecular structure of 2,7-bis(trimethylsilylethynyl)-9,9-
dioctylfluorene 2a is illustrated in Fig. 3, which includes the
atomic numbering scheme. As expected from the spectroscopic
D a l t o n T r a n s . , 2 0 0 3 , 7 4 – 8 4
79

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Fig. 3 The molecular structure of 2a showing the atom numbering
scheme. Only one orientation of the disordered chains is shown for
clarity.
Fig. 4 The molecular structure of 3 showing the atom numbering
scheme.
Table 1 Selected bond lengths (Å) and angles (Њ) for compound 2a
Table 2 Selected bond lengths (Å) and angles (Њ) for compound 3
Si(1)–C(1)
Si(1)–C(3)
C(4)–C(5)
C(6)–C(7)
1.877(8)
1.857(4)
1.208(5)
1.395(5)
1.400(5)
1.527(5)
1.463(5)
1.535(5)
1.549(5)
1.385(5)
1.394(5)
1.382(5)
1.205(5)
1.826(7)
1.856(6)
Si(1)–C(2)
Si(1)–C(4)
C(5)–C(6)
C(7)–C(8)
C(6)–C(11)
C(9)–C(10)
C(10)–C(11)
C(12)–C(13)
C(13)–C(18)
C(14)–C(15)
C(15)–C(19)
C(17)–C(18)
Si(2)–C(20)
Si(2)–C(22)
1.853(4)
1.831(4)
1.452(5)
1.382(5)
1.382(5)
1.380(5)
1.386(5)
1.534(5)
1.385(5)
1.411(5)
1.441(5)
1.400(5)
1.822(4)
1.874(7)
Pt(1)–C(1)
C(1)–C(2)
C(3)–C(4)
C(3)–C(15)
C(5)–C(6)
C(7)–C(8)
C(9)–C(10)
C(10)–C(15)
C(12)–C(13)
C(14)–C(15)
2.007(4)
1.202(6)
1.531(5)
1.523(5)
1.399(6)
1.387(6)
1.472(5)
1.403(5)
1.409(6)
1.387(5)
Pt(1)–P(1)
C(2)–C(13)
C(3)–C(31)
C(4)–C(5)
C(4)–C(9)
C(8)–C(9)
C(10)–C(11)
C(11)–C(12)
C(13)–C(14)
2.2987(12)
1.440(5)
1.541(6)
1.389(6)
1.398(6)
1.397(6)
1.382(5)
1.389(6)
1.408(6)
C(8)–C(9)
C(8)–C(12)
C(9)–C(18)
C(12)–C(24)
C(12)–C(32)
C(13)–C(14)
C(15)–C(16)
C(16)–C(17)
C(19)–C(20)
Si(2)–C(21)
Si(2)–C(23)
C(1)–Pt(1)–C(13a) 180.0
C(1)–Pt(1)–P(1)
P(1)–Pt(1)–P(13a) 180.0
C(1)–C(2)–C(13)
C(4)–C(3)–C(21)
86.79(13)
C(1a)–Pt(1)–P(1)
Pt(1)–C(1)–C(2)
C(4)–C(3)–C(15)
93.21(13)
176.9(4)
101.0(3)
178.8(5)
110.6(3)
Si(1)–C(4)–C(5)
177.8(3)
100.1(3)
111.0(3)
178.4(4)
C(4)–C(5)–C(6)
178.3(4)
112.4(3)
109.3(3)
177.6(4)
C(15)–C(3)–C(21) 111.8(3)
C(8)–C(12)–C(13)
C(8)–C(12)–C(32)
C(15)–C(19)–C(20)
C(8)–C(12)–C(24)
C(24)–C(12)–C(32)
C(19)–C(20)–Si(2)
Symmetry transformation used to generate equivalent atoms: 3a Ϫx Ϫ
1, Ϫy ϩ 1, Ϫz ϩ 1.
An analysis of the intermolecular contacts within the crystal
lattice of 2a shows no strong intermolecular interactions. The
shortest contacts involve the C(4)–C(5) triple bond and a
hydrogen atom, H(1F), from a methyl group on an adjacent
molecule. The C(4) ؒ ؒ ؒ H(1F) and C(5) ؒ ؒ ؒ H(1F) distances
are 2.85 and 2.98 Å, respectively. From the packing diagrams
there is little indication of the long alkyl chains interdigitating
between adjacent molecules.
opposite sides of the fluorenyl plane, but while the chain C(32)–
C(38) extends perpendicular to the ring plane, the second
chain C(21)–C(28), shows a significant bend at C(24) and the
carbon atoms C(24)–C(28) lie almost parallel to the six-
membered ring C(4)–C(9). While the atoms in the octyl
chains and in the n-butyl groups show relatively high dis-
placement parameters the disorder is not as severe as in 2a
and the structure was refined without resorting to a dis-
ordered model.
As in 2a there are no short intermolecular interactions
when the intermolecular contacts in the crystal lattice of
3 are analysed. In addition, the bulky n-butyl phosphines
shield the acetylenic C–C triple bonds from hydrogen-bond
contacts.
The molecular structure of the mononuclear platinum()
diyne 3 is illustrated in Fig. 4 that includes the atom numbering
scheme adopted. Selected bond lengths and angles are listed
in Table 2. The molecule sits on a crystallographic centre of
symmetry that is coincident with the platinum atom, Pt(1). This
metal exhibits the expected trans square planar geometry, as is
found in related platinum poly-yne molecules.17,38 The Pt(1)–
P(1) distance of 2.2987(12) Å lies at the longer end of the
expected range for platinum–phosphine interactions and
reflects the steric bulk of the n-butyl substituents.38 The
platinum–alkynyl σ-interaction is also within the normal range,
with the Pt(1)–C(1) distance of 2.007(4) Å. The ethynylenic unit
is linear [Pt(1)–C(1)–C(2), 176.9(4) and C(1)–C(2)–C(13),
178.8(5)Њ] and the C(1)–C(2) bond is of a similar length, at
1.202(6) Å, to that found in the precursor compound 2a.
Similarly, the fluorenyl unit is essentially planar and the bond
parameters do not show significant differences to those
observed in 2a and in the unsubstituted compound, 2,7-bis(tri-
methylsilylethynyl)flourene.27a The conformation of the octyl
chain substituents at C-9 of the central ring of the fluorene are
also similar to that observed for 2a. The two chains lie on
Conclusion
We have shown that the soluble π-conjugated platinum()-poly-
yne 5, organic poly-ynes 7–9 and their low molecular weight
model diyne compounds 3, 4, 6 containing derivatised fluorenes
in the backbone can be prepared by polycondensation and
cross-coupling reactions. The poly-ynes are easily processable
from organic solvents and exhibit good film-forming properties.
Fluorescence and phosphorescence spectra of the poly-ynes 5,
7, 8, 9, 11 and 12 have been assigned. The inclusion of
side-chains has been shown to prevent aggregation. A strong
red-shift has been achieved when a fluorenone spacer was
introduced into the poly-yne unit.
D a l t o n T r a n s . , 2 0 0 3 , 7 4 – 8 4
80

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Table 3 Crystallographic data for compounds 2a and 3
Experimental
Compound
2a
3
General procedures
All reactions were performed under a dry argon atmosphere
using standard Schlenk or glove box techniques. Solvents were
pre-dried and distilled before use by standard procedures.39 All
chemicals, except where stated otherwise, were obtained from
Sigma Aldrich and used as received. The compounds trans-
[(Ph)(PEt3)2PtCl],40 trans-[(PnBu3)2PtCl2]41 and 1,4-diiodo-2,5-
bis(octyloxy)benzene42 were prepared via literature procedures.
PF8 10 was synthesised at the Cambridge Display Technology
(CDT) via a Suzuki coupling reaction.43 The NMR spectra were
recorded on a Bruker WM-250 or AM-400 spectrometer in
Molecular formula
M
Crystal system
a/Å
b/Å
c/Å
α/Њ
β/Њ
C39H58Si2
583.03
Triclinic
C86H136P2Pt
1426.98
Monoclinic
9.1636(3)
26.4658(18)
16.5754(12)
90
95.231(4)
90
4003.2(4)
P21/c
10.1696(2)
14.1102(2)
14.4029(3)
68.2370(10)
89.3960(10)
83.8980(10)
1907.63(6)
γ/Њ
U/Å3
¯
Space group
Z
P1 (no. 2)
1
CDCl3. The H and 13C{1H} NMR spectra were referenced to
2
2
Dc/Mg mϪ3
1.015
0.116
150(2)
2.93 < θ < 27.5
46744
8639 (Rint = 0.074)
323, 19
0.3348
1.184
1.833
170(2)
3.78 < θ < 27.47
27296
9117 (Rint = 0.041)
408, 0
0.109
0.0457
solvent resonances and 31P{1H} 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 spectro-
meter by the electron impact (EI) and fast atom bombardment
(FAB) techniques. Microanalyses were performed in the
University Chemical Laboratory, University of Cambridge.
Preparative TLC was carried out on commercial Merck plates
with a 0.25 mm layer of silica. Column chromatography was
performed either on Kieselgel 60 (230–400 mesh) silica gel or
alumina (Brockman Grade II-III).
µ/mmϪ1
Temperature/K
Data collection range/Њ
Reflections measured
Independent reflections
Parameters, restraints
wR2 (all data)a
R1 [I > 2σ(I )]b
0.0976
a Data in common: Graphite-monochromated Mo-Kα radiation, λ =
2
2
4
½
0.71073 Å. b R1 = Σ||Fo| Ϫ |Fo||/Σ|Fo|, wR2 = [Σw(Fo Ϫ Fc)2/Σ wFo] , w =
1/[σ2(Fo)2 ϩ (xP)2 ϩ yP], P = (Fo2 ϩ 2F2c)/3, where x and y are constants
2
2
adjusted by the program. Goodness-of-fit = [Σ[w(Fo Ϫ Fc)2]/(n Ϫ p)]
½
where n is the number of reflections and p the number of parameters.
Molecular weight measurements
Molar masses were determined by the GPC method44 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) apparatus with 18 detectors and
auxiliary Viscotek model 200 differential refractometer/visc-
ometer detectors was used to calculate the molecular weights
(referred to as GPC LS).
geometrically-idealised positions and refined using a riding
model. In the structure of 2a the octyl chains and the trimethyl-
silyl groups exhibited severe positional disorder, and where
second positions could be found for the disordered atoms these
were refined as a pair, with the occupancies summed to unity,
and assigned isotropic displacement parameters. In the final
cycles of refinement a weighting scheme was introduced which
produced a flat analysis of variance. Crystal data and refine-
ment details are summarised in Table 3.
Optical characterisation
CCDC reference numbers 193884 and 193885.
All polymers dissolved readily in dichloromethane with gentle
heating to 40 ЊC in a closed vial. Films for use in absorption and
PL measurements were made by spin-coating onto a disc of
Spectrosil B at 1500 revs/minute using a conventional photo-
resist spin-coater, resulting in typical film thicknesses of 150 nm
as measured on a Dektak profilometer. Absorption spectra
were taken using a Hewlett-Packard UV-VIS spectrometer,
over the range 190–1100 nm. PL spectra were taken by exciting
the sample with the UV lines of an argon ion continuous wave
(cw) laser (334, 335 and 365 nm) operating at a typical power of
a few mW. The samples were held in a continuous-flow helium
cryostat, with temperature control provided by an Oxford-
Intelligent temperature controller-4 (ITC-4). The emitted light
was collected by an optical fibre and measured using an Oriel
Spectrograph and a cooled CCD array. The emission was
corrected for the spectral response of the detection system.
For low luminescence intensities, second order scatter of the
excitation lines occurring around 1.7 eV becomes noticeable
and was subtracted from the data. PL quantum yields for
excitation with the UV lines of the argon ion laser were
calculated using the integrating sphere technique.45
See http://www.rsc.org/suppdata/dt/b2/b208963g/ for crystal-
lographic data in CIF or other electronic format.
Ligand synthesis
2-Bromo-9,9-dioctylfluorene 1. 2-Bromofluorene (10.0 g, 41.0
mmol) was reacted with 1-bromooctane (18.2 g, 94.3 mmol) in a
two-phase system composed of 90 mL of toluene and 90 mL of
50 wt% aqueous NaOH using tetra(n-butyl)ammonium brom-
ide as the phase transfer catalyst at 60 ЊC for 4 h. After diluting
the reaction mixture with ethyl acetate, the organic layer was
washed with water several times to remove excess NaOH. The
organic layer was separated and dried with anhydrous MgSO4.
The solvent mixture was pumped off and the residue was
subjected to silica column chromatography using hexane as the
eluent. A colourless oil was obtained (16.4 g, 85% yield) which
was identified as the title compound. 1H NMR (250 MHz,
CDCl3): δ 7.53 (d, 1H, H-5), 7.46 (d, 1H, H-4), 7.44 (m, 2H,
H1,8), 7.35 (m, 3H, H3,6,7), 1.91 (m, 4H), 1.26–1.05 (m, 20H,),
0.81 (t, 6H), 0.52 (m, 4H). 13C NMR (100.6 MHz, CDCl3): δ
152.44 (C10), 150.5 (C13), 141.6 (C12), 140.3 (C11), 131.1–119.97
(C1 8), 55.1(C9), 40.3, 33.9–22.5 (CH2), 14.0 (CH3). EI-mass
to
spectrum: m/z 469.6 (Mϩ). Calc. for C29H41Br: C, 74.18; H, 8.80.
Found: C, 74.22; H, 8.89%.
X-Ray crystallography
Data for compounds 2a and 3 were collected on an Enraf
Nonius Kappa CCD diffractometer equipped with an Oxford
Cryostream crystal cooling apparatus. Semi-empirical absorp-
tion corrections based on interframe scaling were applied. The
structures were solved by direct methods (for 2a) and heavy
atom methods (for 3) and subsequent Fourier difference syn-
theses (SHELX 86)46 and refined by full-matrix least-squares
on F 2 (SHELXL 97).47 Hydrogen atoms were placed in
2-Trimethylsilylethynyl-9,9-dioctylfluorene 1a. To a solution
of 2-bromo-9,9-dioctylfluorene (2 g, 4.25 mmol) in 70 mL of
diisopropylamine–THF (1 : 1, v/v) under argon was added a
catalytic mixture of CuI (10 mg), Pd(OAc)2 (10 mg) and PPh3
(30 mg). The solution was stirred for 20 min at 50 ЊC and then
trimethylsilylethyne (0.62 g, 6.4 mmol) was added and the
mixture stirred for another 20 min. The reaction temperature
was then raised to 75 ЊC and left at reflux with stirring for 20 h.
D a l t o n T r a n s . , 2 0 0 3 , 7 4 – 8 4
81

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The completion of the reaction was determined by silica TLC
and IR spectroscopy. The solution was allowed to cool down to
room temperature, filtered and the solvent mixture was
removed. The residue was subjected to silica column chromato-
graphy using hexane–CH2Cl2 (1 : 1) as eluant to afford 1a as a
colourless liquid in 87% yield (1.80 g). IR (CH2Cl2): ν/cmϪ1
1H NMR (250 MHz, CDCl3): δ 7.58 (dd, 2H, H4,5), 7.44 (dd,
2H, H3,6), 7.41 (brs, 2H, H1,8), 1.92 (m, 4H), 1.21–1.01 (m, 20H),
0.83 (t, 6H), 0.53 (m, 4H), 0.18 (s, 18H, SiMe3 × 2). 13C NMR
(100.6 MHz, CDCl3): δ 150.91 (C-10,13), 140.83 (C-11,12),
᎐
131.20 (C1,8), 126.19, 121.76, 119.79 (C2
), 106.07 (C᎐C),
᎐
to
7
᎐
94.21 (C᎐C), 55.21 (C-9), 40.30, 31.75–22.56 (CH ), 14.04
᎐
2
1
(CH3), 0.17 (SiMe3). EI-mass spectrum: m/z 582.8 (Mϩ). Calc.
for C39H58Si2: C, 80.36; H, 10.03. Found: C, 80.27; H, 10.08%.
2,7-Bis(ethynyl)-9,9-dioctylfluorene 2b. Methanol (45 mL
and aqueous potassium hydroxide (4 mL, 20%) were added at
room temperature to a stirred solution of 2a (2.54 g, 4.36
mmol) in THF (80 mL). The reaction mixture was left at room
temperature for 10 h. The solvent mixture was stripped off to
obtain a viscous liquid, which was then purified by silica gel
column chromatography using hexane as the eluent followed by
recrystallisation in ethanol to give 1.55 g (yield: 82%) of 2b
᎐
2152 (–C᎐C–). H NMR (250 MHz, CDCl ): δ 7.65 (dd, 1H,
᎐
3
H5), 7.60 (d, 1H, H4), 7.43 (m, 2H, H1,8), 7.30 (m, 3H, H3,6,7),
2.15–1.01 (m, 24H, CH2 × 12), 0.83 (t, 6H, CH3 × 2), 0.52 (m,
4H), 0.27 (s, 9H, SiMe3). 13C NMR (100.6 MHz, CDCl3): δ
151.0 (C10), 150.5 (C13), 141.6 (C12), 140.3 (C11), 131.1–119.97
᎐
᎐
(C1
), 106.3 (C᎐C), 93.7 (C᎐C), 55.1 (C ), 40.3, 33.9–22.5
᎐
9
᎐
to
8
(CH2), 14.0 (CH3), 0.049 (SiMe3). EI-mass spectrum: m/z 486.8
(Mϩ). Calc. for C34H50Si: C, 83.88; H, 10.35. Found: C, 84.02;
H, 10.29%.
2-Ethynyl-9,9-dioctylfluorene 1b. 2-Trimethylsilylethynyl-9,9-
dioctylfluorene (1a) (2.0 g, 4.10 mmol) was protodesilylated in
THF–methanol (50 cm3, 4 : 1, v/v) using aqueous KOH (0.5 g,
8.9 mmol in 1 cm3 water). The reaction mixture was stirred at
room temperature for 2 h during which period IR and TLC
revealed that all protected compound had been converted to the
terminal alkyne ligand. The solvent was then removed and the
residue was dissolved in CH2Cl2 and subjected to column
chromatography on silica using hexane–CH2Cl2 (1 : 1, v/v) as
eluant to afford a light yellow viscous liquid identified as 1b
as light yellow microcrystals. Mp: 36.0–36.5 ЊC. IR (CH2Cl2):
1
ν/cmϪ1 2107 (–C᎐C–), 3299 (C᎐C–H). H NMR (250 MHz,
᎐
᎐
᎐
᎐
CDCl3): δ 7.61 (dd, 2H, H4,5), 7.46 (dd, 2H, H3,6), 7.44 (brs, 2H,
᎐
H1,8), 3.14 (s 2H, C᎐C–H), 1.94 (m, 4H), 1.26–1.04 (m, 20H),
᎐
0.89 (t, 6H), 0.56 (m, 4H). 13C NMR (100.6 MHz, CDCl3):
δ 151.03 (C10,13), 140.97 (C11,12), 131.21 (C1,8), 126.53, 120.82,
᎐
᎐
119.93 (C2
), 84.50 (C᎐C), 76.98 (C᎐C), 55.18 (C ), 40.17,
᎐
9
᎐
to
7
31.73–22.54 (CH2), 14.02 (CH3). EI-mass spectrum: m/z 438.67
(Mϩ). Calc. for C33H42: C, 90.34; H, 9.65. Found: C, 90.21; H,
9.59%.
(1.29 g, 76%). IR (CH2Cl2): ν/cmϪ1 2107 (–C᎐C–), 3299 (C᎐C–
᎐
᎐
᎐
᎐
1
H). H NMR (250 MHz, CDCl3): δ 7.66 (dd, 1H, H5), 7.63
(d, 1H, H4), 7.45 (m, 2H, H1,8), 7.34 (m, 3H, H3,6,7), 3.12 (s, 1H,
᎐
Platinum(II) diyne and poly-yne preparations
C᎐C–H), 2.18–1.04 (m, 24H), 0.85 (t, 6H), 0.54 (m, 4H). 13C
᎐
᎐
Trans-[(Bu P) Pt–(C᎐C–R) ] (R ؍ 9,9-dioctylfluoren-2-yl) 3.
NMR (100.6 MHz, CDCl3): δ 151.2 (C10), 150.7 (C13), 141.7
᎐
3
2
2
᎐
᎐
To a stirred solution trans-[(PBu3)2PtCl2] (0.335 g, 0.5 mmol)
and (1b) (0.41 g, 1.0 mmol) in CH2Cl2–iPr2NH (50 cm3, 1 : 1 v/v)
under nitrogen was added a catalytic amount (∼5 mg) of CuI.
The yellow solution was stirred at room temperature. for 15 h,
after which all volatile components were removed under
reduced pressure. The residue was dissolved in CH2Cl2 and
passed through a silica column eluting with hexane–CH2Cl2
(1 : 1, v/v). Removal of the solvents in vacuo gave the title com-
plex as a bright yellow solid in 70% yield (0.49 g). IR (CH2Cl2):
ν/cmϪ1 2095. 1H NMR (250 MHz, CDCl3): δ 7.60 (dd, 2H), 7.52
(d, 2H), 7.30–7.20 (m, 10H), 2.25–1.00 (m, 84H), 0.94 (t, 12H),
0.81 (t, 18H, PCH3), 0.65 (m, 8H). 13C NMR (100 MHz,
(C12), 140.5 (C11), 130.4–120.37 (C1 to 8), 85.8 (C᎐C), 76.7 (C᎐C),
᎐
᎐
55.1 (C9), 40.3, 34.6–22.9 (CH2), 14.4 (CH3). EI-mass spectrum:
m/z 414.6 (Mϩ). Calc. for C31H42: C, 89.79; H, 10.21. Found: C,
89.82; H, 10.11%.
2,7-Dibromo-9,9-dioctylfluorene 2. 2,7-Dibromofluorene
(3.24 g, 10.00 mmol) was reacted with 1-bromooctane (8.23 g,
42.60 mmol) in 25 mL of toluene and 25 mL of 50 wt% aque-
ous NaOH using tetra(n-butyl)ammonium bromide as the
phase transfer catalyst at 80 ЊC for 4 h. The reaction was main-
tained at 90 ЊC for a further 20 h period. A yellowish–green
solution was obtained in the organic phase after cooling to
room temperature. After diluting the reaction mixture with
ethyl acetate, the organic layer was washed with water several
times to remove excess NaOH. The organic layer was separated
and dried over anhydrous MgSO4. The solvent mixture was
stripped off. The residue was dissolved in CH2Cl2 and subjected
to column chromatography on silica using hexane as eluent to
afford a white solid. Recrystallisation from ethanol afforded
analytically pure sample as colourless crystals (4.11 g, 75%
CDCl3): δ 150.69 (C10), 150.25 (C13), 141.24 (C12), 138.09 (C11),
᎐
129.53–119.07 (C1
), 107.97 (C᎐C), 54.73 (C ), 40.55,
᎐
to
8
9
33.99–22.56 (CH2), 14.04 (CH3), 13.83 (CH3). 31P{1H} NMR
(101.3 MHz, CDCl3): δ Ϫ138.07 (1JPt–P = 2633 Hz). FAB-mass
spectrum: m/z 1427.038 (Mϩ). Calc. for C86H136P2Pt: C, 72.38;
H, 9.60. Found: C, 72.44; H, 9.58%.
᎐
᎐
᎐
Trans-[(Ph)(Et P) Pt–C᎐C–R–C᎐C–Pt(PEt ) (Ph)] (R ؍ 9,9-
᎐
3
2
3 2
1
dioctylfluoren-2,7-diyl) 4. This compound was synthesised by
adopting a similar procedure as in 3 using 2b (0.22 g, 0.50
mmol) and trans-[(PEt3)2(Ph)PtCl] (0.543 g, 1.0 mmol). The
product was purified on preparative TLC plates with hexane–
CH2Cl2 (30 : 70, v/v) as eluant giving compound 4 as a red
viscous liquid in an isolated yield of 65% (0.47 g). IR (CH2Cl2):
yield). Mp: 46–47 ЊC. H NMR (CDCl3, 250 MHz): δ 7.53
(d, 2H, J = 7.7 Hz), 7.46 (d, 2H, J = 1.8 Hz), 7.44 (d, 2H, J = 1.1
Hz), 1.91 (m, 4H, J = 3.7 Hz), 1.26–1.05 (m, 20 H), 0.83 (t, 6H,
J = 3.6 Hz), 0.58 (m, 4H, J = 3.5 Hz). 13C NMR (100.6 MHz,
CDCl3): δ 152.44, 138.94, 130.04, 126.07, 121.38, 120.96, 55.56,
40.02, 31.63, 29.78, 29.04, 29.01, 23.51, 22.47, 13.94. EI-mass
spectrum: m/z 548 (Mϩ). Anal. calc. for C29H40Br2: C, 63.49; H,
7.35. Found: C, 63.95; H, 7.30%.
ν/cmϪ1 2095 (–C᎐C–). 1H NMR (250 MHz, CDCl3): δ 7.53
᎐
᎐
(d, 2H, H-4,5), 7.41 (d, 2H, H-3,6), 7.32 (m, 4H, Hortho of Ph),
7.26 (m, 2H, H-1,8), 6.96 (t, 4H, Hmeta of Ph), 6.80 (t, 2H, Hpara
of Ph), 1.82–1.75 (m, 28H, CH2), 1.25–1.05 (m, 24H, PCH2),
0.86 (t, 6H, CH3), 0.82 (t, 36H, CH3). 13C NMR (100 MHz,
CDCl3): δ 156.43 (C10,13), 150.41 (C11,12), 139.20–118.69 (C1
2,7-Bis(trimethylsilylethynyl)-9,9-dioctylfluorene 2a. 2,7-
Dibromo-9,9-dioctylfluorene (2 g, 3.65 mmol), trimethyl-
silylethyne (0.89 g, 9.1 mmol) and iPr2NH–THF (70 mL, 1 : 1)
were mixed with catalytic amounts of CuI (8 mg), Pd (OAc)2
(9 mg) and PPh3 (25 mg) at room temperature. The temperature
was then slowly increased and the reaction mixture was refluxed
for 16 h. The solvent was stripped off under reduced pressure.
The residue was passed through a short column of silica gel
using toluene as the eluent. Evaporation of the solvent led to a
brown oil, which crystallised upon standing. Double recrystal-
lisation from ethanol gave 1.53 g (yield: 72%) of 2a as white
to
8
᎐
and Ph Cs), 112.73, 111.56 (C᎐C), 54.42 (C ), 40.43–14.95
᎐
9
(CH2 in C8H17 and Et3P), 14.07 (CH3in C8H17), 8.04 (CH3in
Et3P). 31P{1H} NMR (101.3 MHz, CDCl3): δ Ϫ131.17 (1JPt–P
=
2643 Hz). FAB-mass spectrum: m/z 1453.63 (Mϩ). Calc. for
C69H110P4Pt2: C, 57.00; H, 7.62. Found: C, 56.96; H, 7.58%.
᎐
᎐
᎐
Trans-[(Bu P) Pt–C᎐C–R–C᎐C–] , (R ؍ 9,9-dioctylfluoren-
᎐
3
2
n
crystals. Mp: 89.3–89.9 ЊC. IR (CH2Cl2): ν/cmϪ1 2149 (–C᎐C–).
2,7-diyl) 5. CuI (5 mg) was added to a mixture of trans-[Pt-
᎐
᎐
D a l t o n T r a n s . , 2 0 0 3 , 7 4 – 8 4
82

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(PBun )2Cl2] (0.670 g, 1.0 mmol) and 2b (0.438 g, 1.0 mmol) in
GPC (THF): Mn = 19200 g molϪ1 (n = 25), Mw = 32650 g molϪ1
,
PDI = 1.7.
Poly-ynes 8 and 9 were synthesised in an analogous manner.
3
iPr2NH–CH2Cl2 (50 cm3, 1 : 1 v/v). The solution was stirred at
room temperature for 15 h, after which all volatile components
were removed under reduced pressure. The residue was dis-
solved in CH2Cl2 and passed through a short alumina column.
After removal of the solvent by a rotary evaporator, an off-
white film was obtained readily which was then washed with
methanol to give the polymer 7 in 85% isolated yield (0.88 g).
Further purification can be accomplished by precipitating the
1
2
1
2
᎐
᎐
᎐
[–R –C᎐C–R –C᎐C–] (R ؍ fluoren-2,7-diyl; R ؍ 2,5-dioc-
᎐
n
tyloxybenzene-1,4-diyl) 8. Off-white solid (67% yield). IR
1
(CH2Cl2): ν/cmϪ1 2203 (–C᎐C–). H NMR (250 MHz, CDCl ):
᎐
᎐
3
δ 7.72 (m, 2H), 7.50 (m, 4H), 7.01–6.95 (m, 2H), 3.94 (m, 4H),
3.78 (s, 2H, CH2), 1.82 (m, 4H), 1.53–1.27 (m, 20H), 0.85 (t,
6H). 13C NMR (100.6 MHz, CDCl3): δ 153.55 (C2,5 benzene),
polymer solution in dichloromethane from methanol. IR
1
(CH2Cl2): ν/cmϪ1 2095 (–C᎐C–). H NMR (250 MHz, CDCl ): δ
᎐
᎐
3
150.77, 149.34, 141.48, 131.50, 120.45–117.60, (other aryl
7.53 (d, 2H, H4–5), 7.41 (s, 2H, H1,8), 7.25 (d, 2H, H3,6), 2.20–
2.01 (m, 12H, PCH2), 1.67–1.01 (m, 52H, CH2), 0.93 (t, 18H),
᎐
carbons), 113.06, 112.43 (C᎐C), 54.65 (C ), 40.21, 31.46–22.25
᎐
9
(CH2), 13.74 (CH3). Calc. for (C39H44O2)n: C, 85.98; H, 8.14.
Found: C,85.74; H, 8.16%. GPC (THF): Mn = 12000 g molϪ1
(n = 22), Mw = 19150 g molϪ1, PDI = 1.6.
0.82 (t, 6H). 13C NMR (100 MHz, CDCl3): δ 150.28 (C10,13),
᎐
137.89 (C11,12), 129.56–118.76 (C1
), 112.23, 111.16 (C᎐C),
᎐
to
8
54.50 (C9), 40.79–22.56 (CH2), 14.05–13.83 (CH3). 31P{1H}
NMR (101.3 MHz, CDCl3): δ Ϫ138.03 (1JPt–P = 2363 Hz). Calc.
for (C57H94P2Pt)n: C, 65.92; H, 9.31. Found: C, 65.77; H, 9.34%.
1
2
1
2
᎐
᎐
᎐
[–R –C᎐C–R –C᎐C–] (R ؍ fluoren-9-on-2,7-diyl; R ؍ 2,5-
᎐
n
dioctyloxybenzene-1,4-diyl) 9. Red solid (84% yield). IR
GPC (THF): Mn = 43550 g molϪ1 (n = 42), Mw = 82745 g molϪ1
PDI = 1.9.
,
1
(CH2Cl2): ν/cmϪ1 2202 (–C᎐C–), 1715 (C᎐O). H NMR (250
᎐
᎐
᎐
MHz, CDCl3): δ 7.49 (m, 2H), 7.30 (m, 4H), 7.01–6.94 (m, 2H),
3.91 (m, 4H), 1.80 (m, 4H), 1.51–1.23 (m, 20H), 0.82 (t, 6H). 13
C
Organic diyne and poly-yne preparations
NMR (100 MHz, CDCl ): δ 192.20 (C᎐O), 153.35 (C
᎐
3
2,5
1
2
1
1
2
benzene), 143.34, 138.28, 134.28, 128.41, 124.23, 120.45 (other
᎐
᎐
᎐
R –C᎐C–R –C᎐C–R (R ؍ 9,9-dioctylfluoren-2-yl; R ؍ 2,5-
᎐
᎐
aryl carbons), 103.65, 96.56 (C᎐C), 31.80–22.64 (CH ), 14.06
᎐
2
dioctyloxybenzene-1,4-diyl) 6. To a mixture of 1b (0.207 g, 0.5
mmol), 1,4-diiodo-2,5-dioctyloxybenzene (0.138 g, 0.25 mmol),
CuI (5 mg), Pd(OAc)2 (5 mg) and PPh3(15 mg) in a Schlenk
(CH3). Calc. for (C39H42O3)n: C, 83.83; H, 7.58. Found C, 84.02;
H, 7.49%. GPC (THF): Mn = 9500 g molϪ1 (n = 17), Mw = 17100
g molϪ1, PDI = 1.8.
flask, Pr2NH (10 cm3) and THF (30 cm3) were added under
i
nitrogen. The resulting mixture was refluxed with stirring for 20
h. Analysis by TLC and IR revealed that the reaction was com-
plete. It was then filtered warm to remove the inorganic com-
pounds. The filtrate was poured into an excess of methanol, and
a bright yellow solid precipitated after cooling. The precipitate
was collected and dissolved in CH2Cl2 (20 cm3). Reprecipitation
(twice) of the CH2Cl2solution into methanol followed by silica
column chromatography with hexane–dichloromethane (4 : 1,
Acknowledgements
M. S. K. acknowledges Sultan Qaboos University (SQU)
Research Grant No. IG/SCI/CHEM/02/01. M. K. A.-S. thanks
the British Council, Muscat for a scholarship and SQU for
study leave. B. A. wishes to thank the DAAD for financial
support and L. M. is grateful to the Cambridge Crystallo-
graphic Data Centre for funding. A. K. thanks Peterhouse,
Cambridge for a Research Fellowship and the Royal Society for
a University Research Fellowship. The support of the EPSRC
for the whole of the project is gratefully acknowledged. We
thank Cambridge Display Technology (CDT) for the synthesis
of 2,7-dibromo-9,9-dioctylfluorene 2 and poly(9,9-dioctyl-
fluorene) 10, Dr Robert Less for the synthesis of platinum()
poly-ynes 11 and 12 and Abdul Kader Hisham for help with
NMR characterisations.
v/v) gave a yellow solid in 65% yield (0.19 g). IR (CH2Cl2):
1
ν/cmϪ1 2210 (–C᎐C–). H NMR (250 MHz, CDCl ): δ 7.69–7.64
᎐
᎐
3
(m, 4H), 7.52–7.50 (m, 4H), 7.36 (m, 6H), 7.08 (t, 2H), 3.94
(t, 4H), 1.97–1.04 (m, 72H), 0.84 (t, 18H), 0.61 (m, 8H). 13C
NMR (100.6 MHz, CDCl3): δ 154.15 (C2,5 benzene), 150.77
(C10,13), 141.44 (C12), 138.09 (C11), 131.47–117.51 (other aryl
᎐
carbons), 112.89, 111.16 (C᎐C), 55.13 (C ), 40.31, 31.76–22.57
᎐
9
(CH2), 14.04 (CH3). EI-mass spectrum: m/z 1157.768 (Mϩ).
Calc. for C84H118O2: C, 89.45; H, 10.54. Found: C, 89.57; H,
10.48%.
References
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2
1
2
᎐
᎐
᎐
[–R –C᎐C–R –C᎐C–] (R ؍ 9,9-dioctylfluoren-2,7-diyl; R ؍
᎐
n
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᎐
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3
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0.85 (t, 12H), 0.60 (m, 4H). 13C NMR (100.6 MHz, CDCl3): δ
153.95 (C2,5 benzene), 150.86, 149.27, 141.39, 131.40, 126.71,
᎐
120.51–117.80, (other aryl carbons), 113.06, 112.43 (C᎐C),
᎐
55.00 (C9), 40.43, 31.58–22.36 (CH2), 13.81 (CH3). Calc. for
(C55H76O2)n: C, 89.61; H, 10.39. Found: C, 89.76; H, 10.38%.
D a l t o n T r a n s . , 2 0 0 3 , 7 4 – 8 4
83

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D a l t o n T r a n s . , 2 0 0 3 , 7 4 – 8 4
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