The development of phenylethylene dendrons for blue phosphorescent emitters

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www.rsc.org/materials | Journal of Materials Chemistry

The development of phenylethylene dendrons for blue

phosphorescent emitters

a

Shih-Chun Lo, Ruth E. Harding,^bEdward Brightman,^cPaul L. Burn^aand Ifor D. W. Samuel^b

*

Received 13th November 2008, Accepted 3rd February 2009

First published as an Advance Article on the web 24th March 2009

DOI: 10.1039/b820235d

New high triplet energy dendrons based on 1,2-diphenylethylene with and without 2-ethylhexyloxy

surface groups have been developed for deep blue phosphorescent iridium(III) dendrimers. The fac-

tris[1-methyl-5-(4-ﬂuoro)phenyl-3-n-propyl-1H-[1,2,4]triazolyl]iridium(III)-cored dendrimers, bearing

ﬁrst generation 1,2-diphenylethylene dendrons on the ligand triazolyl and phenyl rings, were prepared

in excellent yields, employing Sonogashira cross-couplings and palladium catalysed hydrogenation as

the key synthetic steps. Both dendrimers showed good thermal stability although the ﬂexible nature

of the dendrons led to the materials having low glass transition temperatures. Dendrimer 15 (without

the surface groups) emitted good blue phosphorescence with a solution photoluminescence quantum

yield (PLQY) of 46%, Commission Internationale de l’Eclairage (CIE) co-ordinates of (0.15, 0.14)

and photoluminescence peaks at 441 and 468 nm. The solution PLQY was 50% higher than the

parent iridium(III) complex showing that the high triplet energy of the diphenylethylene dendrons

does not quench the luminescence of the iridium(III) complex core. Dendrimer 34, which has the

surface groups, had a ﬁlm PLQY of 49% and CIE co-ordinates of (0.16, 0.19) with PL peaks at

441 and 469 nm.

critical for device performance, and in some cases the dendrons

themselves are also electroactive.^10,13

Introduction

Light-emitting dendrimers have played an important role in the

development of highly efﬁcient solution processed organic light-

emitting diodes (OLEDs). Dendrimers are comprised of cores,

dendrons, and at the distal ends of the dendrons surface groups

can often be found. The dendrons themselves are made up of

branching points and often linking groups that connect the

Dendrimers that are composed of conjugated branching points

and non-conjugated linking units have been studied less for

optoelectronic applications. Benzene,¹⁴triazine,¹⁵and phospha-

zene¹⁶branching groups in conjunction with alkoxy linking units,

and carbazolyl branching points with ethylene linkers¹⁷have

been used in dendrons that have given rise to light-emitting

dendrimers used in OLEDs. One of the issues of the alkoxy-

linked dendrons is the long-term stability of the ether linkage.

1,2-Diphenylethylene based dendrons are isostructural with the

ꢀ

individual branching points. For example, Frechet type den-

drons have benzene branching points and methylenoxy linking

groups.¹The dendrons can play an important role in the prop-

erties of a dendrimer either through the generation that is used

and/or the branching and linking units from which they are

made.²We have primarily been interested in developing den-

drimers for organic optoelectronics applications.^3,4Within this

area conjugated dendrons including stilbenyl⁵or diphenylacety-

lenyl⁶units with phenyl branching and vinyl and acetylenyl

linkers, respectively, and biphenyl,^7,8bithiophenyl,⁹and carba-

zolyl moieties^10–13have played an important role in the devel-

opment of working devices. The latter three dendron types are

differentiated in that the (hetero)aryl units are contiguously

attached in the dendrons. One of the key elements of these latter

dendrons is that they give rigidity to the dendrimers, which

enables control over the intermolecular interactions that are

ꢀ

moieties in Frechet dendrons but have not yet been reported.

As part of our program on light-emitting dendrimer develop-

ment for OLEDs, we have been interested in developing solution

processible deep blue phosphorescent emitters. To this end we

have

developed

fac-tris(1-methyl-5-phenyl-3-n-propyl-1H-

[1,2,4]triazolyl)iridium(III) complexes that show good blue

phosphorescence at room temperature.¹⁸However, small mole-

cule phosphorescent emitters generally require the use of a host

to control the intermolecular interactions that can lead to the

quenching of the luminescence.¹⁹In addition, it has been recently

found that bis-cyclometalated iridium(III) complexes undergo

isomerisation during vacuum processing meaning that their

integrity can be lost during device manufacturing.²⁰By incor-

porating light-emitting chromophores at the core of a dendrimer,

it has been found that the dendritic architecture can control the

interactions that govern device efﬁciency, and that small mole-

cule chromophores can be made solution processible.²¹Biphenyl-

based dendrons have been successfully used for red,²²green,²³

and sky-blue emissive dendrimers²⁴but more recently it has been

reported that the biphenyl dendrons quench the deep blue

emission from iridium(III) complexes in the solid state.^25,26The

^aCentre for Organic Photonics

Queensland, School of Chemistry and Molecular Biosciences, Chemistry

Building, QLD 4072, Australia. E-mail: s.lo@uq.edu.au

^bOrganic Semiconductor Centre, SUPA, School of Physics & Astronomy,

University of St Andrews, North Haugh, Fife, UK KY16 9SS

^cDepartment of Chemistry, University of Oxford, Chemistry Research

Laboratory, Mansﬁeld Road, Oxford, UK OX1 3TA

& Electronics, The University of

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quenching has been attributed to the fact that the triplet energy

of the biphenyl dendrons is near to that of the emissive cores, and

hence the dendrons act as a pathway for energy loss.

the focus in an excellent yield of 99%. The acetylenyl groups in 2

were then hydrogenated with a palladium on carbon catalyst to

give the corresponding 1,2-diphenylethylene dendron 3 in an

87% yield. Reduction of the ester group of 3 with lithium

aluminium hydride furnished the benzyl alcohol focussed den-

dron 4 in a 97% yield and subsequent treatment with phosphorus

tribromide at approximately 90 ^ꢀC gave the benzylbromide

focussed dendron 5 in a 99% yield. The next part of the synthesis

was the generation of the phenylacetylene dendron 12, required

for the dendronisation of the phenyl ring of the ligand. Phenyl-

acetylene 1 was coupled with 3,5-dibromobenzaldehyde under

Sonogashira reaction conditions at 76 ^ꢀC for 2.5 days to give the

ﬁrst generation aldehyde focussed dendron 9 in an 81% yield. For

the conversion of the ﬁrst generation focussed aldehyde 9 into its

acetylene derivative 12, we found that carrying out the Corey–

Fuchs reaction with isolation of the 1,1-dibromovinyl 10 (90%)

and bromoacetylene 11 (97%) intermediates gave a very good

overall yield of 80% of the acetylenyl focussed ﬁrst generation

dendrimer 12.

In this paper we investigate 1,2-diphenylethylene based den-

drons as high triplet energy dendrons that could address this

problem of quenching by the dendrons, and would therefore be

suitable for use with deep blue emissive iridium(III) complexes.

We show that this approach enables good room temperature

photoluminescence quantum yields to be achieved for blue

phosphorescent materials. We ﬁnd that the ethylene linkers

within the dendrons and the presence of surface groups have

a strong effect on the thermal properties of the dendrimers. In

addition, we discuss the effect of the attached dendrons on the

photophysical and electronic properties of the dendrimers and

compare them with a dendrimer with the same emissive core and

surface groups but biphenyl-based dendrons, and the simple

parent and methyl substituted complexes.

Results and discussion

With the two dendrons in hand, there were now two different

approaches toward the formation of the doubly dendronised

ligand 14. The ﬁrst method was to couple 12 with methyl-4-ﬂu-

oro-3-iodobenzoate followed by hydrogenation and elaboration

of the ester group to form the required N-benzoylbutanimidic

acid ethyl ester necessary for the formation of the triazolyl ring.

Although we initially followed this route we found that the

cyclisation step to form the triazolyl ring was capricious and we

were only able to isolate the doubly dendronised ligand 14 in low

yields of between 5–15%. We therefore developed a slightly

different strategy where the mono-dendronised ligand with the

dendron on the triazolyl ring 8 was formed ﬁrst. The benzyl-

bromide focussed dendron 5 was converted to the corresponding

hydrazine 6, which was then reacted with the preformed N-4-

ﬂuoro-3-iodobenzoylbutanimidic acid ethyl ester 7 (formed

from hydrolysis of the methyl ester of methyl-4-ﬂuoro-3-iodo-

benzoate, conversion to the acid chloride, and subsequent

reaction with ethyl butyrimidate hydrochloride) to give the

mono-dendronised ligand 8 in a 64% yield with respect to 5. In

principle two isomers of the triazole ring could form and the

In previous work on light-emitting phosphorescent dendrimers,

it has been found that the attachment of dendrons to both

aromatic rings of the ligands encapsulates the light-emitting iri-

dium(III) complex at the core more efﬁciently than a single

dendron per ligand.²¹Therefore, the dendrimers in this study

have been designed to incorporate a dendron on the triazolyl and

phenyl rings of the core fac-tris[1-methyl-5-(4-ﬂuoro)phenyl-3-n-

propyl-1H-[1,2,4]triazolyl]iridium(III) complex 35. This iridiu-

m(III) complex was chosen as the core because it emits deep blue

phosphorescence at room temperature with CIE co-ordinates of

(0.16, 0.13).¹⁸We chose to form the 1,2-diphenylethylene units

within the dendrons by hydrogenation of diphenylacetylene²⁷

rather than stilbene^28,29units as the former can be prepared under

milder conditions and with excellent yields.^30,31

Synthesis and physical properties

The light-emitting dendrimers (15 and 34) were prepared by ﬁrst

generating a doubly dendronised ligand [a dendron on each

(hetero)aromatic moiety of the ligand], followed by complexa-

tion with iridium(III) (Schemes 1 and 2). The dendrimers differ in

that 34 has 2-ethylhexyloxy surface groups whilst 15 does not.

The 2-ethylhexyloxy surface groups increase the solubility of

dendrimers with conjugated dendrons, and it is likely that they

also play an important role in controlling the intermolecular

interactions of the emissive cores in the solid state. Although the

basic strategy for the formation of the two dendrimers is essen-

tially the same, given the number of steps involved, they will be

discussed separately for clarity.

1

structure of 8 was assigned by comparison with the H NMR

spectrum of the non-dendronised ligand.¹⁸A Sonogashira cross-

coupling of 8 with 12 then gave the doubly dendronised ligand 13

in a 79% yield, and a subsequent hydrogenation over palladium

on charcoal gave the desired ligand with two ﬁrst generation 1,2-

diphenylethylene dendrons, 14, in an 86% yield. The ﬁnal step in

the synthesis of dendrimer 15, without the surface groups, was

the complexation of the doubly dendronised ligand with iridiu-

m(III). This was achieved using the standard two-step proce-

dure.³²In the ﬁrst step 14 was reacted with iridium(III) chloride

trihydrate in a water/2-(n-butoxy)ethanol mixture heated at

reﬂux and then the intermediate chloro-bridged dimer was

reacted with an excess of ligand of 14 in the presence of silver

triﬂuoromethanesulfonate in the melt. Under these conditions,

the iridium(III) dendrimer 15 was formed in a good yield of 69%

for the two steps. 15 was determined as the facial isomer by the

symmetry associated with the ¹H NMR spectrum. The symmetry

in the spectrum of 15 was the same as that for complex 35

(Fig. 1), which has been unambiguously assigned as the facial

isomer from an X-ray crystal structure.¹⁸

The synthesis of the doubly dendronised ligand of 15

(Scheme 1) involved attachment of a dendron to the ligand phenyl

ring prior to hydrogenation with the second dendron incorpo-

rated into the ligand during the cyclisation reaction to form the

triazolyl ring. The synthesis of the ﬁrst generation benzylbromide

focussed 1,2-diphenylethylene dendron 5, required for the

formation of the triazolyl ring of the ligand, started with

commercially available methyl-3,5-diiodobenzoate. An excess of

phenylacetylene 1 was reacted with methyl-3,5-diiodobenzoate

under Sonogashira conditions to give 2 with an ester moiety at

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Scheme 1 Conditions and reagents: (i) Methyl-3,5-diiodobenzoate, Pd(PPh₃)₄, CuI, NEt₃, THF, heat, argon. (ii) 10% Pd/C, hydrogen, EtOAc, MeOH,

r.t. (iii) Lithium aluminium hydride, THF, r.t. and then heat, argon. (iv) PBr₃, r.t. and then heat, argon. (v) Hydrazine monohydrate, EtOH, heat, argon.

(vi) CHCl₃, r.t., argon. (vii) 3,5-Dibromoaldehyde, Pd(PPh₃)₄, CuI, NEt₃, THF, heat, argon. (viii) CBr₄, CH₂Cl₂, PPh₃, r.t., argon. (ix) Sodium tert-

butoxide, toluene, heat, argon. (x) tert-Butyllithium, THF, ꢁ78 ^ꢀC, argon, and then water, ꢁ78 ^ꢀC to r.t, argon. (xi) Pd(PPh₃)₄, CuI, NEt₃, THF, heat,

argon. (xii) 10% Pd/C, hydrogen, EtOAc, MeOH, r.t. (xiii) Iridium(III) chloride trihydrate, water, 2-(n-butoxy)ethanol, heat, argon, and then silver

triﬂuoromethanesulfonate, 14, heat, argon.

The ﬁrst step in the preparation of dendrimer 34 with the

2-ethylhexyloxy surface groups was the synthesis of phenyl-

acetylene 18. 2-(2-Ethylhexyloxy)-4-iodobenzene 16³³was

reacted with 2-methylbuty-3-yn-2-ol to give 4-[4-(2-ethyl-

hexyloxy)phenyl]-2-methylbut-3-yn-2-ol 17 in quantitative yield

under the standard Sonogashira coupling conditions. 17 was

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Scheme 2 Conditions and reagents: (i) 2-Methylbut-3-yn-2-ol, Pd(PPh₃)₄, CuI, NEt₃, THF, heat, argon. (ii) Sodium tert-butoxide, heptane, heat, argon.

(iii) 3,5-Dibromobenzaldehyde, Pd(PPh₃)₄, CuI, NEt₃, THF, heat, argon. (iv) CBr₄, CH₂Cl₂, PPh₃, r.t., argon. (v) Sodium tert-butoxide, toluene, heat,

argon. (vi) tert-Butyllithium, THF, ꢁ78 ^ꢀC, argon, and then water, ꢁ78 ^ꢀC to r.t., argon. (vii) Methyl-4-ﬂuoro-3-iodobenzoate, Pd(PPh₃)₄, CuI, NEt₃,

THF, heat, argon. (viii) 10% Pd/C, hydrogen, EtOAc, MeOH, r.t. ix) Methyl-3,5-diiodobenzoate, Pd(PPh₃)₄, CuI, NEt₃, THF, heat, argon. (x) 10% Pd/

C, hydrogen, EtOAc, MeOH, r.t. xi) Lithium aluminium hydride, THF, r.t. and then heat, argon. (xii) PBr₃, r.t. and then heat, argon. (xiii) Hydrazine

monohydrate, EtOH, heat, argon. (xiv) LiOH, water, MeOH, THF, heat, argon and then 3 M HCl_(aq), r.t. (xv) Thionyl chloride, heat, argon. (xvi) Ethyl

butyrimidate hydrochloride, NEt₃, CHCl₃, argon. (xvii) 27, CHCl₃, argon. (xviii) Iridium(III) chloride trihydrate, water, 2-(n-butoxy)ethanol, heat,

argon, and then silver triﬂuoromethanesulfonate, 33, heat, argon. R ¼ 2-ethylhexyl.

then deprotected with sodium tert-butoxide to give after puriﬁ-

cation a 94% yield of 18. To form the required dendron benzyl

bromide precursor to the triazolyl ring, 18 was reacted with

methyl-3,5-diiodobenzoate under Sonogashira conditions to give

the ﬁrst generation dendron 23 in a 97% yield. The acetylenes

were then reduced using palladium on carbon catalysed

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Fig. 1 Structure of the parent 35 and methyl-substituted 36 complexes and ﬁrst generation dendrimer 37 with 2-ethylhexyloxy surface groups and ﬁrst

generation biphenyl-based dendrons.

hydrogenation to give 24 also in a 97% yield. The ester at the

focus of 24 was then reduced to the corresponding benzyl alcohol

25 with lithium aluminium hydride and then the benzyl alcohol

25 was converted into the benzylbromide 26 using phosphorous

tribromide. This gave 26 in an overall yield of 93% for the two

steps. For the preparation of the phenylacetylenyl-focussed

dendron 22, required for the formation of the dendronised ligand

phenyl ring, 18 was ﬁrst reacted with 3,5-dibromobenzaldehyde

to give 19 in an 88% yield. The dibromovinyl focussed dendron

20 was then formed by reaction of 19 with triphenylphosphine

and carbon tetrabromide in a 94% yield, and 20 was then con-

verted to the bromoacetylene 21 in a 92% yield by treatment with

sodium tert-butoxide in toluene at 50 ^ꢀC. Finally the acetylene 22

was formed by metallation with tert-butyllithium followed by

quenching of the anion in a 93% yield. The ﬁrst generation

acetylenyl focussed dendron 22 was then coupled with methyl-4-

ﬂuoro-3-iodobenzoate, which itself was prepared from 4-ﬂuoro-

3-iodotoluene by oxidation with potassium permanganate and

then acid catalysed esteriﬁcation with methanol in an overall

yield of 44%. The Sonogashira coupling of dendron 22 with

methyl-4-ﬂuoro-3-iodobenzoate gave the dendronised phenyl

ring of the ligand 28 in a quantitative yield. Hydrogenation of 28

afforded 29 with the saturated dendron in place in a 95% yield.

The ﬁnal formation of the doubly dendronised ligand involved

several consecutive parallel steps. The ester of 29 was hydrolysed

to give the corresponding acid 30, which was then converted to

the acid chloride 31 with thionyl chloride and subsequent reac-

tion gave the butanimidic acid ethyl ester 32. 32 was then reacted

with the preformed benzylhydrazine 27 prepared by reaction of

26 with hydrazine hydrate to give 49% of the doubly dendronised

ligand 33 as a single isomer. The ﬁnal dendrimer 34 with the 2-

ethylhexyloxy surface groups and two dendrons per ligand was

synthesised using the two step sequence,³²namely reaction with

iridium(III) chloride trihydrate to form the chloro-bridged dimer

followed by treatment of the dimer with an excess of 33 and silver

triﬂuoromethanesulfonate. Under these conditions the den-

drimer 34 was formed in a creditable 47% yield for the two steps.

The proposed facial arrangement of 34 was consistent with the

symmetry observed in the ¹H NMR spectrum.

We determined the hydrodynamic radii of the two new den-

drimers using gel permeation chromatography (GPC) (against

polystyrene standards) in combination with the Hester–Mitchell

equation and Mark–Houwink relationship.³⁴GPC analysis

showed that dendrimers 15 and 34 were mono-disperse and had

ꢁ

M_vs of 1966 and 3836 corresponding to hydrodynamic radii of

˚

9.4 A and 13.8 A, respectively. The presence of the 2-ethyl-

hexyloxy surface groups clearly increases the relative size of the

dendrimer. For comparison the doubly dendronised dendrimer

37 (Fig. 1) that has 2-ethylhexyloxy groups and ﬁrst generation

26

˚

biphenyl-based dendrons has a hydrodynamic radius of 12.8 A.

The larger radius of 34 with respect to 37 illustrates the fact that

the ethylene linkers make the dendrons and hence dendrimers

larger. It is interesting to note that 15, which does not have any

surface groups, was very soluble in a range of organic solvents

including chloroform, toluene and tetrahydrofuran unlike the

case of iridium(III) complex cored dendrimers with biphenyl

dendrons but no surface groups.³⁵The ﬂexibility within the

dendron and the link to the iridium(III) complex core clearly

improves the solubility of dendrimers.

Given the difference in solubility between the dendrimers with

the rigid and ﬂexible dendrons, we were interested to see what

affect the ﬂexible dendrons had on the thermal properties of the

dendrimers. Thermal gravimetric analysis of 15 and 34 showed

that they had good thermal stability with both dendrimers

having decomposition temperatures, corresponding to a 5%

weight loss, of around 400 ^ꢀC. Differential Scanning Calorimetry

showed that 15 (without the surface groups) and 34 (with the

surface groups) had glass transition temperatures (T_gs) of 34 ^ꢀC

ꢀ

and ꢁ3 C, respectively. In contrast, 37 with the rigid biphenyl

dendrons and the 2-ethylhexyloxy surface groups had a T_gof 76

^ꢀC. It is therefore clear that while the surface groups can play an

important role in the processing of the dendrimers, they can also

depress their thermal transitions. The fact that the T_gof 37 is

higher than 15 or 34 indicates that a reduction in the T_gcan be

counteracted, at least in part, by using rigid structures in the

dendrons. Therefore, the balance between rigid and ﬂexible units

within a light-emitting dendrimer structure is an important

design criterion.

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Photophysical and electronic properties

To understand the effect of the 1,2-diphenylethylene dendrons

on the properties of the emissive core, we compare the properties

of dendrimers 15 and 34 with a simple parent complex 35, the

methyl-substituted complex 36,²⁵and doubly dendronised

biphenyl dendrimer 37 (Fig. 1).²⁶The UV-visible absorption

spectra of dendrimers 15 and 34 are shown in Fig. 2. The stronger

absorptions at short wavelength (240–320 nm) correspond to the

p–p* transitions of the ligands with those at wavelengths >320

nm being due to a transition between a Highest Occupied

Molecular Orbital consisting of metal d orbitals and ligand p

orbitals and a Lowest Unoccupied Molecular Orbital mainly

consisting of ligand p orbitals.¹⁸The onset of absorption of the

dendrimers is slightly red-shifted compared to the simple core

complex 35 and this is due to the presence of the alkyl group

attached to the phenyl ring of the ligand. Evidence for this comes

from the absorption of the methyl substituted complex 36, which

has the same onset to absorption. The next step in the analysis of

the photophysical properties was the measurement of the solu-

tion photoluminescence (PL) spectra (at room temperature,

Fig. 3). It can be seen that as with the absorption spectrum the

addition of the methyl group shifts the PL spectrum of 36 to the

red when compared with the core complex 35. The dendrons and/

or the presence of the surface groups do not change the positions

of the peaks appreciably when compared to 36 (see Table 1) and

the dendrimers emit deep blue light with Commission Inter-

nationale de l’Eclairage (CIE) co-ordinates of (0.15–0.16, 0.14–

0.18). The CIE co-ordinates are slightly different for each of the

compounds due to a different weighting of the (0,0) and (0,1)

transitions. On moving to the solid state the PL spectra of den-

drimers 15 and 34 were essentially the same even though there

was a small red-tail in the ﬁlm PL of 15 (Fig. 4). The similarity in

the PL spectra on going from solution to ﬁlm indicates that to

Fig. 3 Solution (toluene) PL spectra of 15, 34, 35, 36, and 37. The

spectra have been normalised for ease of comparison.

Table 1 Summary of the photophysical and electrochemical properties

of the iridium(III) complexes and dendrimers

PL

PLQYs (%)

CIEs (x,y)^aSolution^aFilm^bt [ms]

PL lifetime^a

peaks

[nm]^a

E_1/2

(ox)^c[V]

35¹⁸428, 456 (0.16, 0.13) 27

36²⁵437, 467 (0.16, 0.16) 40

37²⁶441, 468 (0.15, 0.16) 59

—

17

21

49

1.25

1.93

22

1.72

1.65

0.50

0.41

0.53

0.47

0.45

15

34

441, 468 (0.15, 0.14) 46

441, 470 (0.16, 0.18) 45

a

b

c

Measured in toluene. Spin-coated from chloroform solution. The

potentials are quoted against the ferricenium/ferrocene couple, scan

rate ¼ 40 mV/s, solvent ¼ dichloromethane, concentration ¼ 1 mM,

platinum working electrode.

a ﬁrst approximation the dendrons are controlling the intermo-

lecular interactions that lead to the quenching of the lumines-

cence.

To understand the effect of the dendrons on the photophysical

properties of the emissive iridium(III) complex core in greater

detail, we measured the solution PLQYs and time resolved PL

(TRPL) (Table 1). The ﬁrst point to note is that the solution

PLQYs of 15 and 34 are signiﬁcantly higher than the parent

complex 35 and essentially the same as each other. Compound 36

has a similar solution PLQY, showing that the addition of the

alkyl groups signiﬁcantly increases the luminescence of the

complexes, whilst only slightly changing the colour. The solution

PLQYs of the dendrimers with the diphenylethylene dendrons

are slightly lower than that of 37, which has the biphenyl den-

drons. However, the PL lifetimes of 15 and 34 are shorter by

more than an order of magnitude when compared to that of the

37 and close to that of the core complex (Table 1). This indicates

Fig. 2 Solution (dichloromethane) UV-visible spectra for 15, 34, 35,

and 36.

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the oxidation potentials of all the materials are similar indicating

that attachment of a dendron para to the iridium and meta to the

heterocyclic ring has little effect on the highest occupied molec-

ular orbital energies.

Conclusions

In conclusion we have developed methodology for forming

diphenylethylene-based dendrons. These dendrons are like

ꢀ

Frechet dendrons in that the branching points are separated by

saturated units but are without the relatively sensitive benzyloxy

group. Such dendrons could therefore be of use in applications in

which the benzyloxy group is unstable. The diphenylethylene-

based dendrons have a high triplet energy making them suitable

for encapsulating deep blue emissive iridium(III) complexes. The

diphenylethylene dendrons were found not to quench the lumi-

nescence of the emissive core in solution, and enhanced the

solution PLQY of the core chromophore. In the solid state it was

found that the combination of dendrons and surface groups

enabled a high room temperature PLQY (49%) for a neat spin-

coated ﬁlm of a blue phosphorescent material to be achieved.

Our results show that high triplet energy dendrons are required

for blue phosphorescent dendrimers.

Fig. 4 Solution (toluene) and ﬁlm PL spectra of 15 and 34. The spectra

have been normalised for ease of comparison.

that the strong modiﬁcation of the luminescence process in 37,

which is due to the triplet spending time on the dendron, has been

avoided in 15 and 34 by the high triplet energy dendrons. That is,

for 15 and 34 the triplet is localised on core metal complex,

whereas for 37 it also spends time on the dendrons. Finally, the

ﬁlm PLQYs of the dendrimers were measured. For dendrimer 37

with the biphenyl dendrons there was a signiﬁcant drop in the

PLQY in moving from solution to the solid state (from 59% to

17%).²⁶Intermolecular interactions of emissive chromophores

can lead to the quenching of the luminescence and while the core

of dendrimer 37 is surrounded by dendrons and surface groups,

the triplet excitons spend time on the dendron of 37 and hence

dendron–dendron interactions can also lead to quenching of the

luminescence. For dendrimer 15 (without the surface groups)

there was a 50% decrease in the PLQY in moving from solution

to the solid state. However, for dendrimer 34 with surface groups

the solution and solid state PLQYs were essentially the same,

with an excellent solid state PLQY of 49% for an emission colour

with CIE co-ordinates of (0.16, 0.18). The lower solid state

PLQY for dendrimer 15 indicates that the lack of surface groups

allows an increase of intermolecular interactions of the emissive

core. That is, the surface groups not only play an important role

in the processing of the dendrimers but also in the way the

emissive cores interact in the solid state.

Experimental

Synthesis of organic materials

Unless otherwise noted, all chemicals were obtained from

commercial suppliers and used as received. Melting points were

measured in a glass capillary on a Gallenkamp melting point

apparatus and are uncorrected. The ¹H NMR spectra were

measured in deuterated chloroform with either Bruker DPX 400

MHz, DQX 400 MHz, or AMX 500 MHz spectrometers: SP ¼

surface phenyl; BP ¼ branch phenyl; LP ¼ ligand phenyl; EH ¼

2-ethylhexyl; Pr ¼ n-propyl. All J values are rounded to the

nearest 0.5 Hz. Microanalyses were carried out in the Inorganic

Chemistry Laboratory, Oxford, or at the Metropolitan Univer-

sity, London, UK. The UV-visible absorption spectra were

recorded as solutions in HPLC grade dichloromethane with

a Perkin-Elmer UV-vis Lambda 25 spectrometer. Mass spectra

were recorded on a Waters LCT Premier XE for TOF ES or an

Applied Biosystems Voyager matrix-assisted laser desorption/

ionisation time-of-ﬂight (MALDI-TOF) from 2-[(2E)-3-(4-tert-

butylphenyl)-2-methylprop-2-enylidene]malononitrile, (DCTB)

in positive reﬂection mode at the EPSRC National Mass Spec-

trometry Centre, Swansea, UK or a Micromass Tofspec E

spectrometer matrix-assisted laser desorption/ionisation time-

of-ﬂight (MALDI-TOF) from 2-5-dihydroxybenzoic acid, (DHB)

in positive reﬂection mode at Oxford. Thermal gravimetric

analysis was performed on a Perkin-Elmer thermogravimetric

analyzer TGA7. Differential Scanning Calorimetry was carried

out using a Perkin Elmer Pyris 1. Gel permeation chromatog-

raphy was carried out using PLgel Mixed-A columns (600 mm +

300 mm lengths, 7.5 mm diameter) from Polymer Laboratories

A ﬁnal aspect of the study was to determine the effect of the

dendrons on the electronic properties of the dendrimers. Cyclic

voltammetry measurements were carried out on dendrimers 15

and 34 and the methyl substituted core. Under the conditions

used we were able to observe a single chemically reversible

oxidation for each of the materials and the results are summar-

ised in Table 1. However, we could not observe chemically

reversible reductions under the conditions used. The ﬁrst key

point to note is that the electroactive component of dendrimers

15 and 34 is the core. This can be seen by the fact that the

oxidation potential does not change appreciably for 15 and 34

when compared with the methyl substituted complex 36. Indeed

ꢁ

calibrated with polystyrene narrow standards (Mp ¼ 580 to 3.2

ꢂ 10⁶) in tetrahydrofuran. The tetrahydrofuran was degassed

with helium and pumped with a rate of 1 mL/min at 30.0 ^ꢀC.

Light petroleum refers to the fraction of boiling point 40–60 ^ꢀC.

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When solvent mixtures are used for chromatography over silica,

the proportions are given by volume.

cooled to room temperature and the solvents were removed.

Water (16 cm³) was added and the mixture was extracted with

dichloromethane (4 ꢂ 10 cm³). The dichloromethane extracts

were combined, washed with brine (20 cm³), dried over anhy-

drous sodium sulfate and ﬁltered. The ﬁltrate was collected and

the solvent was removed. The residue was puriﬁed by column

chromatography over silica using dichloromethane:light petro-

leum (1:70 to 1:3) mixtures as eluent to give 2 as a light yellow

Electrochemical measurements

Electrochemistry was performed using an EG&G Princeton

Applied Research potentiostat/galvanostat model 263A. All

measurements were made at room temperature on samples dis-

solved in dichloromethane, with 0.1 M tetra-ethylammonium

tetraﬂuoroborate as the electrolyte. The electrolyte was puriﬁed

by recrystallization from a mixture of ethyl acetate and diethyl

ether. The solutions were deoxygenated with argon. The ferri-

cenium/ferrocene couple was used as standard³⁶and the ferro-

cene was puriﬁed by sublimation. All potentials are quoted

relative to the ferricenium/ferrocene couple. In all cases several

scans were carried out to conﬁrm the chemical reversibility of the

redox processes.

ꢀ

solid (346 mg, 99%); mp 105–106 C; (Found: C, 85.6; H, 4.7.

C₂₄H₁₆O₂requires C, 85.7; H, 4.8%); l_max(CH₂Cl₂)/nm: 259 sh

(log 3/dm³mol^ꢁ1cm^ꢁ14.69), 271 sh (4.81), 285 (4.95), 290 sh

(4.91), 302 (4.92) and 336 sh (3.69); n_max(ﬁlm)/cm^ꢁ11728 (C]O),

2214 (ChC); d_H(400.1 MHz, CDCl₃) 3.97 (3 H, s, COOCH₃),

7.36–7.40 (6 H, m, SP H), 7.52–7.58 (4 H, m, SP H), 7.87 (1 H, dd

J 1.5, J 1.5, G1-BP H) and 8.16 (2 H, d, J 1.5, G1-BP H); d_C

(100.6 MHz; CDCl₃) 52.4, 87.6, 90.85, 122.6, 124.1, 128.4, 128.7,

130.8, 131.7, 132.1, 138.2 and 165.8; m/z [microTOF ES⁺] 337.1

(MH⁺), 359.1 (M⁺+ Na).

Photophysical studies

Methyl-3,5-bis[2-phenylethylen-1-yl]benzoate 3. A solution of

2 (403 mg, 1.20 mmol), ethyl acetate (23 cm³), and methanol

(23 cm³) was deoxygenated (by placing under vacuum and

backﬁlling with argon) four times. 10% Palladium on carbon

(102 mg) was added to the mixture and the mixture was

deoxygenated three times. A balloon ﬁlled with hydrogen was

attached and the reaction mixture was brieﬂy degassed and

backﬁlled with hydrogen three times. The reaction was stirred

at room temperature under hydrogen for 17 h. The mixture was

passed through a plug of silica using dichloromethane as eluent

(the silica was poured into excess water immediately to quench

the catalyst). The ﬁltrate was collected and the solvent was

removed. The residue was puriﬁed by column chromatography

over silica using dichloromethane:light petroleum (0:1 to 1:5)

mixtures as eluent to give 3 as a colourless oil (360 mg, 87%);

(Found: C, 83.7; H, 7.1. C₂₄H₂₄O₂requires C, 83.7; H, 7.0%);

l_max(CH₂Cl₂)/nm: 238 (log 3/dm³mol^ꢁ1cm^ꢁ14.03), 269 (3.12),

285 (3.28) and 293 (3.24); n_max(neat)/cm^ꢁ11722 (C]O); d_H

(400.1 MHz, CDCl₃) 2.92 (8 H, m, CH₂CH₂), 3.93 (3 H, s,

COOCH₃), 7.09 (1 H, s, G1-BP H), 7.15–7.24 (6 H, m, SP H),

7.27–7.33 (4 H, m, SP H) and 7.74 (2 H, s, G1-BP H); d_C(100.6

MHz; CDCl₃) 37.7, 37.8, 52.05, 126.0, 127.3, 128.4, 128.5,

130.2, 133.6, 141.4, 142.0 and 167.4; m/z [TOF ES⁺] 345.3

(MH⁺), 362.3 (MNH₄⁺).

For solution measurements samples were dissolved in spectro-

scopic grade toluene, their optical density was adjusted to 0.1 ꢃ

0.01 at 360 nm. The solution was transferred into quartz

degassing cuvettes, then degassed by three freeze–pump–thaw

cycles, sealed under vacuum, and warmed to nominal room

temperature in a bath of water. A Jobin Yvon Fluoromax 2

ﬂuorimeter was used to measure the photoluminescence spectra.

The measurements in solution were recorded using, the highest

spectral resolution, using an excitation wavelength of 360 nm,

whilst those in ﬁlm were recorded using a medium resolution at

an excitation wavelength of 325 nm. Spectra were corrected after

measurement using the emission calibration obtained from

measuring a calibrated lamp spectrum. Solution PLQYs were

measured by a relative method using quinine sulfate in 0.5 M

sulfuric acid as a standard.³⁷The error in this method is esti-

mated to be approximately 10%. Film PLQYs were measured by

exciting with a HeCd laser at a wavelength of 325 nm using

a calibrated integrating sphere.³⁸

Photoluminescence lifetimes were measured on the same

degassed solutions at room temperature by the method of time-

correlated single-photon counting (TCSPC). The samples were

excited at 390 nm by a pulsed light-emitting diode (Picoquant

PLS 370) giving 10 pJ/pulse at a pulse repetition rate of 100 kHz.

The emission was focused onto a monochromator entrance slit

and detected with a cooled Hamamtsu micro-channel plate

photomultiplier tube RU-3809U-50. The average number of

photons collected per pulse was 0.1 or less. The apparatus

response function was z0.5 ns (FWHM) in the shortest time

window. The measured lifetime was obtained by ﬁtting a single

exponential decay to the measured transient.

3,5-Bis[2-phenylethylen-1-yl]benzyl

alcohol

4.

Lithium

aluminium hydride (144 mg, 3.80 mmol) was added to a solution

of 3 (600 mg, 1.74 mmol) in anhydrous tetrahydrofuran (29 cm³).

The mixture was stirred at room temperature for 5 min and then

heated in an oil bath held at 60 ^ꢀC under argon for 4 h. The

reaction was allowed to cool to room temperature and carefully

poured into a mixture of ice and water (z20 cm³). The mixture

was extracted with ethyl acetate (4 ꢂ 20 cm³). The ethyl acetate

extracts were combined, washed with brine (30 cm³), dried over

anhydrous sodium sulfate, and ﬁltered. The ﬁltrate was collected

and the solvent was removed to give 4 as a colourless oil (537 mg,

97%); (Found: C, 87.2; H, 7.75. C₂₃H₂₄O₂requires C, 87.3; H,

7.6%); l_max(CH₂Cl₂)/nm: 248 sh (log 3/dm³mol^ꢁ1cm^ꢁ12.83), 254

sh (2.94), 259 (2.99), 263 sh (2.96), 269 (2.91), 274 sh (2.56) and

293 sh (1.97); n_max(neat)/cm^ꢁ13326 (OH); d_H(400.1 MHz,

Methyl-3,5-bis[2-phenylacetylen-1-yl]benzoate 2. Tetrakis-

(triphenylphosphine)palladium(0) (83 mg, 0.07 mmol) was added

to a deoxygenated (by placing under vacuum and backﬁlling with

argon) mixture of methyl-3,5-diiodobenzoate (400 mg, 1.03

mmol), phenylacetylene 1 (316 mg, 3.09 mmol), copper iodide (30

mg, 0.14 mmol), triethylamine (3 cm³), and tetrahydrofuran (3

cm³). The mixture was deoxygenated again and then heated in an

ꢀ

oil bath held at 60 C under argon for 18 h. The mixture was

3220 | J. Mater. Chem., 2009, 19, 3213–3227

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CDCl₃) 1.58 (1 H, s, OH), 2.90 (8 H, s, CH₂CH₂), 4.65 (2 H, d, J

4.5, ArCH₂O), 6.93 (1 H, s, G1-BP H), 7.03 (2 H, s, G1-BP H),

7.17–7.24 (6 H, m, SP H) and 7.27–7.33 (4 H, m, SP H); d_C(100.6

MHz, CDCl₃) 37.8, 37.9, 65.2, 124.7, 125.9, 128.0, 128.3, 128.4,

140.9, 141.7 and 142.0; m/z [microTOF ES⁺] 339.2 (M⁺+ Na).

using dichloromethane:light petroleum (1:10 to 1:5) mixtures as

eluent to give 10 as a brownish oil (5.42 g, 90%); (Found: C, 62.4;

H, 3.1; C₂₄H₁₄Br₂requires C, 62.4; H, 3.05%); l_max(CH₂Cl₂)/nm:

272 sh (log 3/dm³mol^ꢁ1cm^ꢁ15.29), 280 sh (5.34), 287 (5.40) and

304 (5.30); n_max(neat)/cm^ꢁ12213 (ChC); d_H(400.1 MHz,

CDCl₃) 7.37–7.44 (6 H, m, SP H), 7.46 (1 H, s, Br₂C]CH),

7.53–7.60 (4 H, m, SP H), 7.64 (2 H, d, J 1.5, G1-BP H) and 7.68

(1 H, dd, J 1.5, J 1.5, G1-BP H); d_C(100.6 MHz; CDCl₃) 87.9,

90.5, 91.7, 122.7, 124.0, 128.4, 128.6, 130.9, 131.7, 134.3, 135.3

and 135.9.

3,5-Bis[2-phenylethylen-1-yl]benzylbromide 5. Phosphorus tri-

bromide (0.7 cm³, 7.57 mmol) was added to 4 (537 mg, 1.70

mmol) with care. The mixture was heated in an oil bath held at 93

^ꢀC under argon for 14 h. The reaction was cooled to room

temperature and diluted with ether (15 cm³). The mixture was

cooled to 0–2 ^ꢀC and very carefully quenched with a mixture of

ice and water (10 cm³). The two layers were separated and the

aqueous layer was extracted with ether (3 ꢂ 10 cm³). The organic

layers were combined, washed with brine (20 cm³), dried over

anhydrous sodium sulfate, and ﬁltered. The ﬁltrate was collected

and the solvent was removed. The residue was puriﬁed by

column chromatography over silica using dichloromethane:light

petroleum (1:40 to 1:5) mixtures as eluent to give 5 as a colourless

oil (640 mg, 99%); (Found: C, 72.9; H, 6.1. C₂₃H₂₃Br requires C,

72.8; H, 6.1%); l_max(CH₂Cl₂)/nm: 241 sh (log 3/dm³mol^ꢁ1cm^ꢁ1

3.90), 269 sh (3.23) and 283 sh (2.87); d_H(400.1 MHz, CDCl₃)

2.89 (8 H, s, CH₂CH₂), 4.46 (2 H, s, ArCH₂Br), 6.91 (1 H, s, G1-

BP H), 7.05 (2 H, s, G1-BP H), 7.16–7.24 (6 H, m, SP H) and

7.27–7.33 (4 H, m, SP H); d_C(100.6 MHz, CDCl₃) 33.8, 37.7,

37.8, 125.9, 126.8, 128.3, 128.4, 129.0, 137.7, 141.5 and 142.3; m/z

[microTOF ES⁺] 403.1 (M⁺+ Na).

1-[3,5-Bis(2-phenylacetylen-1-yl)phenyl]-2-bromoacetylene 11.

Sodium tert-butoxide (2.26 g, 23.5 mmol) was added to a solution

of 10 (5.42 g, 11.7 mmol) in toluene (167 cm³). The mixture was

heated in an oil bath at 50 ^ꢀC under argon for 15 h. The reaction

was cooled to room temperature and the solvent was removed.

Water (10 cm³) was added to the residue and the mixture was

extracted with dichloromethane (3 ꢂ 20 cm³). The organic layers

were combined, washed with brine (20 cm³), dried over sodium

sulfate, and ﬁltered. The ﬁltrate was collected and the solvent

removed. The residue was puriﬁed by column chromatography

over silica using dichloromethane:light petroleum (1:30 to 1:5)

mixtures as eluent to give 11 as a white solid (4.32 g, 97%); mp

103–104 ^ꢀC; (Found: C, 75.7; H, 3.4. C₂₄H₁₃Br requires C, 75.6;

H, 3.4%); l_max(CH₂Cl₂)/nm: 243sh (log 3/dm³mol^ꢁ1cm^ꢁ14.43),

269 (4.69), 279 sh (4.67), 286 (4.77), 293 sh (4.70) and 304 (4.75);

n_max(ﬁlm)/cm^ꢁ12185 (ChC), 2211 (ChC); d_H(400.1 MHz,

CDCl₃) 7.33–7.40 (6 H, m, SP H), 7.50–7.60 (6 H, m, SP H & G1-

BP H) and 7.67 (1 H, dd, J, 1.5, J 1.5, G1-BP H); d_C(100.6 MHz;

CDCl₃) 51.4, 78.6, 87.6, 90.7, 122.7, 123.4, 124.1, 128.4, 128.7,

131.7, 134.4 and 134.5; m/z [TOF FI⁺] 380.0, 382.0 (M⁺).

3,5-Bis[2-phenylacetylen-1-yl]benzaldehyde 9. A mixture of 3,5-

dibromobenzaldehyde (4.33 g, 16.4 mmol), phenylacetylene 1

(4.20 g, 41.1 mmol), copper iodide (330 mg, 1.73 mmol), tri-

ethylamine (40 cm³), and tetrahydrofuran (40 cm³) was deoxy-

genated (by placing under vacuum and backﬁlling with argon)

four times. Tetrakis(triphenylphosphine)palladium(0) (1.00 g,

0.865 mmol) was added to the mixture, which was then deoxy-

genated further four times. The solution was heated under argon

in an oil bath held at 76 ^ꢀC for 63 h. The reaction was cooled to

room temperature and the solvent was removed. The residue was

puriﬁed by column chromatography over silica using dichlor-

omethane:light petroleum (1:100 to 1:5) mixtures as eluent to

give 9 as a brownish solid (4.08 g, 81%); mp 85–88 ^ꢀC; (Found: C,

90.1; H, 4.5. C₂₄H₁₃O requires C, 90.2; H, 4.6%); l_max(CH₂Cl₂)/

nm: 277 sh (log 3/dm³mol^ꢁ1cm^ꢁ15.00), 285 (5.06), 303 (4.98) and

341 sh (3.87); n_max(ﬁlm)/cm^ꢁ11704 (C]O), 2212 (ChC); d_H

(400.1 MHz, CDCl₃) 7.33–7.47 (6 H, m, SP H), 7.52–7.63 (4 H,

m, SP H), 7.94 (1 H, dd, J 1.5, J 1.5, G1-BP H), 7.98 (1 H, d, J

1.5, G1-BP H) and 10.02 (1 H, s, CHO); d_C(100.6 MHz; CDCl₃)

87.2, 91.5, 122.4, 124.9, 128.5, 128.9, 131.7, 131.9, 136.6, 139.5

and 190.9.

1-[3,5-Bis(2-phenylacetylen-1-yl)phenyl]acetylene 12. A solu-

tion of 11 (4.32 g, 11.3 mmol) in tetrahydrofuran (180 cm³) was

cooled to ꢁ78 ^ꢀC under argon. Tert-butyllithium (10.7 cm³, 18.1

mmol) was added dropwise with care to the mixture. The reac-

tion was stirred at ꢁ78 C for 2 h and then water (20 cm³) was

ꢀ

added very carefully while the mixture was at ꢁ78 C. The reac-

tion was allowed to warm to room temperature and then stirred

for 13 h. The tetrahydrofuran was removed and the residue was

extracted with dichloromethane (4 ꢂ 20 cm³), and the combined

extracts were washed with brine (25 cm³), dried over magnesium

sulfate, and ﬁltered. The ﬁltrate was collected and the solvent was

removed. The residue was puriﬁed by column chromatography

over silica using dichloromethane:light petroleum (1:20 to 1:10)

mixtur_ꢀes as eluent to give 12 as a white solid (3.15 g, 92%); mp

83–84 C; (Found: C, 95.2; H, 4.6. C₂₄H₁₄requires C, 95.3; H,

4.7%); l_max(CH₂Cl₂)/nm: 244 sh (log 3/dm³mol^ꢁ1cm^ꢁ14.63), 257

(4.73), 272 sh (4.78), 279 sh (4.84), 286 (4.95), 293 sh (4.88) and

303 (4.94); n_max(ﬁlm)/cm^ꢁ12211 (ChC), 3292 (ChC–H); d_H

(400.1 MHz, CDCl₃) 3.13 (1 H, s, ChC–H), 7.35–7.40 (6 H, m,

SP H), 7.50–7.58 (4 H, m, SP H), 7.61 (2 H, d, J 1.5, G1-BP H)

and 7.69 (1 H, dd, J 1.5, J 1.5, G1-BP H); d_C(100.6 MHz; CDCl₃)

78.3, 82.0, 87.6, 90.6, 122.7, 122.8, 124.0, 128.4, 128.6, 131.7,

134.5 and 134.6; m/z [EI⁺] Anal. Calcd for C₂₄H₁₄: 302.1096

(M⁺). Found: 302.1090 (M⁺).

1-[3,5-Bis(2-phenylacetylen-1-yl)phenyl]-2,2-dibromovinylene 10.

A solution of 9 (4.00 g, 13.1 mmol), carbon tetrabromide (8.66 g,

26.1 mmol) and dichloromethane (70 cm³) was cooled in a water

bath. Triphenylphosphine (13.7 g, 52.2 mmol) was added in

portions over a period of 7 min to the mixture (Note: the reaction

is exothermic). After addition of the triphenylphosphine, the

water bath was removed and the reaction was stirred at room

temperature under argon for 14 h. The solvent was removed and

the residue was puriﬁed by column chromatography over silica

1-[3,5-Bis(2-phenylethylen-1-yl)benzyl]-5-(4-ﬂuoro-3-iodophenyl)-

3-n-propyl-1H-1,2,4-triazole 8. 5 (520 mg, 1.37 mmol) was added

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slowly to a solution of hydrazine monohydrate (360 mg, 7.32

mmol) in ethanol (10 cm³) heated at reﬂux. After addition, the

mixture was kept at reﬂux under argon for 14 h. The reaction

was allowed to cool to room temperature and the solvent was

removed. The residue was dissolved in dichloromethane (40 cm³),

dried over anhydrous sodium sulfate, and ﬁltered. The ﬁltrate

was collected and the solvent was removed to give a colourless

oil of 6 (z453 mg), which was used without puriﬁcation. A

mixture of thionyl chloride (2.1 cm³) and 4-ﬂuoro-3-iodobenzoic

acid (1.98 g, 7.44 mmol) was heated at reﬂux for 27 h under

argon. The reaction was allowed to cool and the excess thionyl

chloride was removed to give 4-ﬂuoro-3-iodobenzoyl chloride

(z1.97 g) as a light brown solid. Triethylamine (0.5 cm³) was

added dropwise to a mixture of 4-ﬂuoro-3-iodobenzoyl chloride

(z390 mg, z1.37 mmol), ethyl butyrimidate hydrochloride (208

mg, 1.37 mmol) and dichloromethane (9 cm³) under argon. The

reaction mixture was stirred at room temperature for 15 h. The

mixture was washed with water (4 ꢂ 7 cm³) and brine (7 cm³),

dried over anhydrous sodium sulfate, and ﬁltered. The ﬁltrate

was collected and the solvent was removed to give a brownish oil

of the ethyl butyrimidate ester 7 (z498 mg), which was used

without puriﬁcation. A solution of 6 (z453 mg) in chloroform

(2 cm³) was added to a solution of 7 (z498 mg) in chloroform (8

cm³) under argon. The reaction mixture was stirred at room

temperature for 22 h. The solvent was removed to leave a yellow

oil as the residue. The residue was puriﬁed by column chroma-

tography over silica using dichloromethane:light petroleum (1:10

to 1:0) and ethyl acetate–dichloromethane (1:10) mixtures as

eluent to give 8 as a colourless oil (556 mg, 64% for the two

steps with respect to 5); (Found: C, 65.0; H, 5.2; N, 6.6.

C₃₄H₃₃FIN₃requires C, 64.9; H, 5.3; N, 6.7%); l_max(CH₂Cl₂)/

nm: 253 sh (log 3/dm³mol^ꢁ1cm^ꢁ13.94) and 310 sh (2.93); d_H

(400.2 MHz, CDCl₃) 1.04 (3 H, t, J 7.5, Pr CH₃), 1.85 (2 H, m,

Pr CH₂), 2.73 (2 H, t, J 7.5, Pr CH₂), 2.86 (8 H, s, CH₂CH₂),

5.27 (2 H, s, NCH₂Ar), 6.81 (2 H, s, G1-BP H), 6.91 (1 H, s,

G1-BP H), 7.06–7.29 (11 H, m, SP H & LP H), 7.46 (1 H, m, LP

H) and 7.94 (1 H, dd, J 2 & 6, LP H); d_F(376.6 MHz, CDCl₃)

ꢁ91.0; m/z [microTOF ES⁺] 630.2 (MH⁺).

H, m, SP H), 7,14–7.20 (3 H, m, SP H & LP H), 7.24 (4 H m,

SP H),7.39 (6 H, m, SP H), 7.47 (1 H, m, LP H), 7.56 (4 H, m, SP

H), 7.62 (2 H, d, J 1.5, G1-BP H), 7.68 (1 H, dd, J 1.5, J 1.5, G1-

BP H) and 7.72 (1 H, dd, J 2, J 6.5, LP H); d_F(376.6 MHz,

CDCl₃) ꢁ106.9; m/z [TOF ES⁺] 804.3 (MH⁺).

1-[3,5-Bis(2-phenylethylen-1-yl)benzyl]-5-[4-ﬂuoro-3-(2-{3,5-bis-

[2-phenylethylen-1-yl]phenyl}ethylen-1-yl)phenyl]-3-n-propyl-1H-

1,2,4-triazole 14. A solution of 13 (470 mg, 0.58 mmol) in an ethyl

acetate (8.5 cm³) and methanol (15 cm³) mixture was deoxygen-

ated (by placing under vacuum and backﬁlling with argon) four

times. 10% Palladium on carbon (66 mg) was added to the

solution and the mixture was degassed then deoxygenated

further four times. A balloon ﬁlled with hydrogen was attached

and the mixture was brieﬂy degassed and backﬁlled with

hydrogen four times. The reaction mixture was stirred at room

temperature under an atmosphere of hydrogen for 16 h. The

mixture was passed through a plug of silica using dichloro-

methane as eluent (the silica was poured into excess water

immediately to quench the catalyst). The ﬁltrate was collected

and the solvent removed. The residue was puriﬁed by column

chromatography over silica using dichloromethane:light petro-

leum (1:40 to 1:3) mixtures as eluent to give 14 as a light yellow

oil (409 mg, 86%); (Found: C, 85.4; H, 7.1; N, 5.25. C₅₈H₅₈FN₃

requires C, 85.4; H, 7.2; N, 5.15%); l_max(CH₂Cl₂)/nm: 247 sh

(log 3/dm³mol^ꢁ1cm^ꢁ14.16); d_H(400.1 MHz, CDCl₃) 1.04 (3 H, t,

J 7.5, Pr CH₃), 1.86 (2 H, m, Pr CH₂), 2.75–2.92 (22 H, m, Pr CH₂

& CH₂CH₂), 5.21 (2 H, s, NCH₂Ar), 6.74 (2 H, s, G1-BP H), 6.80

(3 H, bm, G1-BP H), 6.88 (1 H, s, G1-BP H), 7.04–7.34 (22 H, m,

SP H & LP H) and 7.43 (1 H, dd, J 2, J 7, LP H); d_F(376.6 MHz,

CDCl₃) ꢁ115.6; m/z [microTOF ES⁺] 816.5 (MH⁺).

Tris-fac-[1-(3,5-bis{2-phenylethylen-1-yl}benzyl)-5-(4-ﬂuoro-3-

{2-[3,5-bis(2-phenylethylen-1-yl)phenyl]ethylen-1-yl}phenyl)-3-n-

propyl-1H-1,2,4-triazolyl]iridium(III) 15. A mixture of 14 (240

mg, 0.29 mmol), iridium(III) chloride trihydrate (43 mg, 0.12

mmol), water (0.5 cm³), and 2-(n-butoxy)ethanol (1.5 cm³) was

heated at reﬂux under argon for 14 h. The reaction was allowed

to cool to room temperature to leave a brown gel and a yellow

liquid. The liquid was removed and the gel was triturated with

water (3 ꢂ 2 cm³). The residue was dissolved in dichloromethane

(10 cm³), dried over anhydrous sodium sulfate and ﬁltered. The

ﬁltrate was collected and the solvent was removed to give

a brown–yellow oil (270 mg) containing a mixture of the iridium

chloro-bridged dimer and 14. A mixture of the oil (270 mg), 14

(560 mg, 0.69 mmol), silver triﬂuoromethanesulfonate (63 mg,

0.24 mmol) was heated under argon in an oil bath held at 166 ^ꢀC

for 14.5 h. The mixture was allowed to cool to room temperature

and then puriﬁed by column chromatography over silica using

dichloromethane:light petroleum (1:20 to 2:1) and ethyl aceta-

te:dichloromethane (1:20 to 1:10) mixtures as eluent to give

a yellow gum of 15 (223 mg, 69% for the two steps); mp 38–40 ^ꢀC;

(Found: C, 79.3; H, 6.5; N, 4.7. C₁₇₄H₁₇₁F₃IrN₉requires C, 79.2;

H, 6.5; N, 4.8%); l_max(CH₂Cl₂)/nm: 249 (log 3/dm³mol^ꢁ1cm^ꢁ1

4.80), 262 (4.71), 273 sh (4.61), 298 (4.29), 339 (4.12), 366 sh

(3.93), 395 sh (3.61) and 433 sh (2.61); d_H(400.2 MHz, CDCl₃)

0.73 (9 H, t, J 7.5, Pr CH₃), 1.40 and 1.50 (2 ꢂ 3 H, m, Pr CH₂),

2.07 and 2.27 (2 ꢂ 3 H, m, Pr CH₂), 2.47 and 2.64 (2 ꢂ 3 H, m,

CH₂CH₂), 2.71–2.92 (54 H, m, CH₂CH₂), 5.35 (3 H, d, J 16.5, 1/

1-[3,5-Bis(2-phenylethylen-1-yl)benzyl]-5-[4-ﬂuoro-3-(2-{3,5-bis-

[2-phenylacetylen-1-yl]phenyl}acetylen-1-yl)phenyl-3-n-propyl-1H-

1,2,4-triazole 13. A mixture of 8 (470 mg, 0.75 mmol), 12 (270 mg,

0.90 mmol), copper iodide (37 mg, 0.19 mmol), triethylamine

(3.7 cm³) and tetrahydrofuran (3.7 cm³) was deoxygenated (by

placing under vacuum and backﬁlling with argon) four times.

Tetrakis(triphenylphosphine)palladium(0) (60 mg, 0.05 mmol)

was added to the mixture, which was then deoxygenated further

four times. The reaction mixture was heated under argon in an oil

bath held at 77 ^ꢀC for 15 h. The reaction was cooled to room

temperature and the solvents were removed. The residue was

puriﬁed by column chromatography over silica using dichlor-

omethane:light petroleum (1:20 to 1:0) mixtures as eluent to give

13 as a colourless oil (476 mg, 79%); (Found: C, 88.7; H, 5.7; N,

5.3. C₅₈H₄₆FN₃requires C, 88.6; H, 5.8; N, 5.2%); l_max(CH₂Cl₂)/

nm: 258 sh (log 3/dm³mol^ꢁ1cm^ꢁ14.25), 273 sh (4.40), 288 (4.58),

296 sh (4.51) and 305 (4.56); n_max(neat)/cm^ꢁ12214 (ChC);

d_H(400.2 MHz, CDCl₃) 1.06 (3 H, t, J 7.5, Pr CH₃), 1.88 (2 H, m,

Pr CH₂), 2.77–2.88 (10 H, m, Pr CH₂& CH₂CH₂), 5.32 (2 H, s,

NCH₂Ar), 6.79 (2 H, s, G1-BP H), 6.90 (1 H, s, G1-BP H), 7.10 (4

3222 | J. Mater. Chem., 2009, 19, 3213–3227

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2NCH₂Ar), 5.53 (3 H, d, J 16.5, 1/2NCH₂Ar), 6.24 (3 H, d,

J 11.4, LP H), 6.82 (6 H, m, G1-BP H), 6.88 (12 H, m, G1-BP H)

and 7.04–7.28 (63 H, m, SP H & LP H); d_F(376.6 MHz, CDCl₃)

ꢁ115.4; m/z [MALDI: DCTB] Anal. Calcd for C₁₇₄H₁₇₁F₃IrN₉:

2634.3 (21%), 2635.3 (42%), 2636.3 (78%), 2637.3 (100%), 2638.3

(85%), 2639.3 (52%), 2640.3 (25%), 2641.3 (8%), 2642.3 (3%).

Found: 2634.3 (26%), 2635.3, (51%), 2636.3 (83%), 2637.3

(100%), 2638.3 (92%), 2639.3 (56%), 2640.3 (25%), 2641.3 (11%),

2642.3 (4%) (M⁺). Excess 14 (474 mg), which co-chromato-

reaction was cooled to room temperature and the solvents were

removed. The residue was puriﬁed by column chromatography

over silica using dichloromethane:light petroleum (0:1 to 1:5)

mixtures as eluent to give 19 as a brownish oil (14.3 g, 88%);

(Found: C, 83.1; H, 8.2. C₃₉H₄₆O₃requires C, 83.2; H, 8.2%);

l_max(CH₂Cl₂)/nm: 256 (log 3/dm³mol^ꢁ1cm^ꢁ14.60), 302 (4.75),

315 (4.75) and 359 sh (3.75);n_max(neat)/cm^ꢁ11704 (C]O), 2211

(ChC); d_H(400.1 MHz, CDCl₃) 0.90–0.98 (12 H, m, EH CH₃),

1.30–1.55 (16 H, m, EH CH₂), 1.70–1.80 (2 H, m, EH CH), 3.88

(4 H, m, ArOCH₂), 6.90 & 7.48 (8 H, AA⁰BB⁰, SP H), 7.88 (1 H,

dd, J 1.5, J 1.5, G1-BP H), 7.92 (2 H, d, J 1.5, G1-BP H) and 10.0

(1 H, s, ArCHO); d_C(100.6 MHz, CDCl₃) 11.1, 14.1, 23.0, 23.8,

29.0, 30.4, 39.2, 70.5, 86.0, 91.7, 114.1, 114.6, 125.15, 131.3,

133.2, 136.5, 139.1, 159.9 and 191.0; m/z [microTOF ES⁺] 585.3

(M⁺+ Na).

1

graphed with and had an identical H NMR to an authentic

sample, was also recovered.

4-[4-(2-Ethylhexyloxy)phenyl]-2-methylbut-3-yn-2-ol 17. Tet-

rakis(triphenylphosphine)palladium(0) (600 mg, 0.519 mmol)

was added to a deoxygenated (by placing under vacuum and

backﬁlling with argon) mixture of 16 (12.9 g, 38.8 mmol), 2-

methylbut-3-yn-2-ol (4.25 g, 50.5 mmol), copper iodide (740 mg,

3.83 mmol), triethylamine (80 cm³) and tetrahydrofuran (80 cm³).

The mixture was then deoxygenated again before being heated

1-[3,5-Bis(2-{4-[2-ethylhexyloxy]phenyl}acetylen-1-yl)phenyl]-

2,2-dibromovinylene 20. Triphenylphosphine (4.11 g, 15.6 mmol)

was added to a mixture of 19 (2.20 g, 3.91 mmol), carbon tet-

rabromide (2.60 g, 7.84 mmol), and dichloromethane (22 cm³)

(Note: the reaction is exothermic). The mixture was stirred at

room temperature under argon for 4 h and then passed through

a plug of silica using dichloromethane as the eluent. The ﬁltrate

was collected and the solvent removed. The residue was puriﬁed

by column chromatography over silica using dichloromethane:-

light petroleum (0:1 to 1:10) mixtures as eluent to give 20 as

a brownish oil (2.64 g, 94%); (Found: C, 66.9; H, 6.5.

C₄₀H₄₆Br₂O₂requires C, 66.9; H, 6.45%); l_max(CH₂Cl₂)/nm: 259

sh (log 3/dm³mol^ꢁ1cm^ꢁ14.61), 269 (4.64), 301 (4.83), and 317

(4.80); n_max(neat)/cm^ꢁ12211 (ChC); d_H(400.2 MHz, CDCl₃)

0.93–1.01 (12 H, m, EH CH₃), 1.31–1.61 (16 H, m, EH CH₂),

1.71–1.81 (2 H, m, EH CH), 3.88 (4 H, m, ArOCH₂), 6.91 and

7.50 (8 H, AA⁰BB⁰, SP H), 7.44 (1 H, s, Br₂C]CH), 7.61 (2 H, m,

G1-BP H) and 7.66 (1 H, dd, J 1.5, J 1.5, G1-BP H); d_C(100.6

MHz, CDCl₃) 11.1, 14.1, 23.0, 23.8, 29.0, 30.4, 39.2, 70.5, 86.7,

90.7, 91.3, 114.47, 114.53, 124.3, 130.3, 133.1, 133.9, 135.5, 135.6

and 159.6; m/z [microTOF ES⁺] 739.2, 741.2, 743.2 (M⁺+ Na).

ꢀ

under argon in an oil bath held at 60 C for 16 h. The reaction

was cooled to room temperature and the solvents were removed.

The residue was puriﬁed by column chromatography over silica

using dichloromethane:light petroleum (0:1 to 1:10) mixtures as

eluent to give of 17 as a brownish oil (11.15 g, 100%); (Found: C,

79.2; H, 9.7. C₁₉H₂₈O₂requires C, 79.1; H, 9.8%); l_max(CH₂Cl₂)/

nm: 257 (log 3/dm³mol^ꢁ1cm^ꢁ14.46), 284 sh (3.40) and 296 (3.15);

n_max(neat)/cm^ꢁ12229 (ChC), 3360 (OH); d_H(400.2 MHz,

CDCl₃) 0.89–0.97 (6 H, m, EH CH₃), 1.27–1.55 (8 H, m, EH

CH₂), 1.62 (6 H, s, CH₃), 1.67–1.78 (1 H, m, EH CH), 2.35 (1 H,

br s, OH), 3.83 (2 H, m, ArOCH₂), 6.83 and 7.34 (4 H, AA⁰BB⁰,

SP H); d_C(100.6 MHz, CDCl₃) 11.0, 14.0, 23.0, 23.7, 29.0, 30.4,

31.5, 39.2, 65.5, 70.4, 82.0, 92.2, 114.35, 114.4, 132.9 and 159.3;

m/z [TOF ES⁺] 271.2 (M-OH), 289.2 (MH⁺).

1-(2-Ethylhexyloxy)-4-acetylenylbenzene 18. A mixture of 17

(38.8 g, 134 mmol), heptane (650 cm³) and sodium tert-butoxide

(3.75 g, 39.0 mmol) was heated under argon in an oil bath held at

100 ^ꢀC for 17 h. The mixture was allowed to cool to room

temperature and the solvent was removed. The residue was

puriﬁed by column chromatography over silica using dichlor-

omethane:light petroleum (1:80 to 1:5) mixtures as eluent to give

18 as a brownish oil (28.9 g, 94%); (Found: C, 83.6; H, 9.6.

C₁₆H₂₂O requires C, 83.4; H, 9.6%); l_max(CH₂Cl₂)/nm: 255 (log

3/dm³mol^ꢁ1cm^ꢁ14.33), 283 (3.42), 294 (3.24), 302 sh (2.95), 322

(2.99), and 345 (2.90);n_max(neat)/cm^ꢁ12108 (ChC); d_H(400.2

MHz, CDCl₃) 0.88–0.99 (6 H, m, EH CH₃), 1.29–1.59 (8 H, m,

EH CH₂), 1.69–1.80 (1 H, m, EH CH), 3.02 (1 H, s, ChCH), 3.86

(2 H, m, ArOCH₂), 6.86 and 7.45 (4 H, AA⁰BB⁰, SP H); d_C(100.6

MHz, CDCl₃) 11.0, 14.0, 23.0, 23.8, 29.0, 30.4, 39.3, 70.5, 75.6,

83.8, 113.8, 114.4, 133.5 and 159.7; m/z [TOF CI⁺] 231.2 (MH⁺).

1-[3,5-Bis(2-{4-[2-ethylhexyloxy]phenyl}acetylen-1-yl)phenyl]-

2-bromoacetylene 21. A mixture of 20 (1.52 g, 2.12 mmol),

sodium tert-butoxide (406 mg, 4.23 mmol), and toluene (30 cm³)

was heated under argon in an oil bath held at 50 ^ꢀC for 15 h. The

mixture was allowed to cool to room temperature and the solvent

was removed. Water (10 cm³) was added to the residue. The

mixture was extracted with dichloromethane (3 ꢂ 15 cm³). The

dichloromethane extracts were combined, washed with brine (20

cm³), dried over anhydrous magnesium sulfate, and ﬁltered. The

ﬁltrate was collected and the solvent removed. The residue was

puriﬁed by column chromatography over silica using dichlor-

omethane:light petroleum (0:1 to 1:10) mixtures as eluent to

afford 21 as a pale yellow oil (1.24 g, 92%); (Found: C, 75.4; H,

7.0. C₄₀H₄₅BrO₂requires C, 75.3; H, 7.1%); l_max(CH₂Cl₂)/nm:

254 sh (log 3/dm³mol^ꢁ1cm^ꢁ14.53), 266 (4.56), 306 (4.76) and 318

(4.75);n_max(neat)/cm^ꢁ12211 (ChC); d_H(400.1 MHz, CDCl₃)

0.88–1.00 (12 H, m, EH CH₃), 1.28–1.61 (16 H, m, EH CH₂),

1.70–1.82 (2 H, m, EH CH), 3.87 (4 H, m, ArOCH₂), 6.89 & 7.45

(8 H, AA⁰BB⁰, SP H), 7.51 (2 H, d, J 1.5, G1-BP H) and 7.62 (1

H, dd, J 1.5, J 1.5, G1-BP H); m/z [microTOF ES⁺] 636.3,

638.3 (M⁺).

3,5-Bis[2-(4-{2-ethylhexyloxy}phenyl)acetylen-1-yl]benzalde-

hyde 19. Tetrakis(triphenylphosphine)palladium(0) (1.42 g, 1.23

mmol) was added to a deoxygenated (by placing under vacuum

and backﬁlling with argon four times) mixture of 3,5-dibromo-

benzaldehyde (7.58 g, 28.7 mmol), 18 (18.0 g, 78.1 mmol), copper

iodide (740 mg, 3.89 mmol), triethylamine (76 cm³), and tetra-

hydrofuran (76 cm³). The mixture was deoxygenated again and

then heated under argon in an oil bath held at 72 ^ꢀC for 61 h. The

This journal is ª The Royal Society of Chemistry 2009

J. Mater. Chem., 2009, 19, 3213–3227 | 3223

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[3,5-Bis(2-{4-[2-ethylhexyloxy]phenyl}acetylen-1-yl)phenyl]ace-

tylene 22. A solution of 21 (220 mg, 0.345 mmol) in ether (10 cm³)

was cooled to ꢁ78 ^ꢀC under argon. Tert-butyllithium (0.32 cm³,

0.552 mmol) was added carefully to the reaction. The mixture

was stirred at ꢁ78 ^ꢀC for 2.5 h and then water (1 cm³) was added

a deoxygenated (by placing under vacuum and backﬁlling with

argon) mixture of methyl-4-ﬂuoro-3-iodobenzoate (250 mg, 0.89

mmol), 22 (700 mg, 1.25 mmol), copper iodide (34 mg, 0.19 mmol),

triethylamine (5 cm³), and tetrahydrofuran (5 cm³). The mixture

was deoxygenated again and then heated under argon in an oil

bath held at 77 ^ꢀC for 14 h. The mixture was cooled to room

temperature and the solvents were removed. The residue was

puriﬁed by column chromatography over silica using dichlor-

omethane:light petroleum (1:40 to 1:3) mixtures as eluent to give 28

as a colourless oil (635 mg, 100%); (Found: C, 81.1; H, 7.3.

C₄₈H₅₁FO₄requires C, 81.1; H, 7.2%); l_max(CH₂Cl₂)/nm: 259 sh

(log 3/dm³mol^ꢁ1cm^ꢁ14.68), 273 sh (4.74), 290 sh (4.95), 301 sh

(5.03), 308 (5.07) and 319 sh (4.92); n_max(neat)/cm^ꢁ11728 (C]O),

2211 (ChC); d_H(400.2 MHz, CDCl₃) 0.89–0.99 (12 H, m, EH

CH₃), 1.28–1.58 (16 H, m, EH CH₂), 1.69–1.80 (2 H, m, EH CH),

3.87 (4 H, m, ArOCH₂), 3.94 (3 H, s, COOCH₃), 6.90 and 7.48 (8

H, AA⁰BB⁰, SP H), 7.18 (1 H, t, J 8.5, LP H), 7.48 (4 H, 1/

2AA⁰BB⁰, SP H), 7.64 (3 H, m, G1-BP H), 8.04 (1 H, m, LP H) and

8.24 (1 H, dd, J 2, J 7, LP H); d_F(376.6 MHz, CDCl₃) ꢁ102.7; m/z

[TOF ES⁺] 711.3 (MH⁺).

ꢀ

very carefully dropwise to the reaction mixture while atꢁ78 C.

After 30 min, the mixture was warmed to room temperature and

diluted with water (5 cm³) and ether (6 cm³). The organic layer

was separated and the aqueous layer was extracted with ether (3

ꢂ 10 cm³). The organic layers were combined, washed with brine

(12 cm³), dried over anhydrous magnesium sulfate, and ﬁltered.

The ﬁltrate was collected and the solvent was removed. The

residue was puriﬁed by column chromatography over silica using

dichloromethane:light petroleum (0:1 to 1:5) mixtures as eluent

to give 22 as a pale yellow oil (180 mg, 93%); (Found: C, 86.05;

H, 8.4. C₄₀H₄₆O₂requires C, 86.0; H, 8.3%); l_max(CH₂Cl₂)/nm:

244 sh (log 3/dm³mol^ꢁ1cm^ꢁ14.65), 254 (4.69), 263 sh (4.66), 303

(4.94) and 317 (4.93); n_max(neat)/cm^ꢁ12209 (ChC), 3297 (ChC–

H); d_H(400.1 MHz, CDCl₃) 0.85–0.99 (12 H, m, EH CH₃), 1.27–

1.60 (16 H, m, EH CH₂), 1.69–1.80 (2 H, m, EH CH), 3.10

(ChC–H), 3.87 (4 H, m, ArOCH₂), 6.89 & 7.46 (8 H, AA⁰BB⁰,

SP H), 7.56 (2 H, m, G1-BP H) and 7.63 (1 H, m, G1-BP H); d_C

(100.6 MHz, CDCl₃) 11.1, 14.1, 23.0, 23.8, 29.0, 30.4, 39.3, 70.5,

78.1, 82.2, 86.4, 90.8, 114.4, 114.5, 122.7, 124.3, 133.1, 133.9,

134.3 and 159.7; m/z [microTOF ES⁺] 581.3 (M⁺+ Na).

Methyl-3-[2-(3,5-bis{2-[4-(2-ethylhexyloxy)phenyl]ethylen-1-yl}-

phenyl)ethylen-1-yl]-4-ﬂuorobenzoate 29. A solution of 28 (635

mg, 0.89 mmol), ethyl acetate (10 cm³), and methanol (10 cm³)

was deoxygenated (by placing under vacuum and backﬁlling with

argon) four times. 10% Palladium on carbon (130 mg) was

added to the mixture, which was then deoxygenated further

four times. A balloon ﬁlled with hydrogen was attached and the

reaction mixture was brieﬂy degassed and backﬁlled with

hydrogen four times. The reaction was stirred at room

temperature under hydrogen for 14 h. The mixture was passed

through a plug of silica using dichloromethane as eluent (60

cm³) (the silica was poured into excess water immeditely to

quench the catalyst). The ﬁltrate was collected and the solvent

removed. The mixture was puriﬁed by column chromatography

over silica using dichloromethane:light petroleum (1:30 to 1:3)

mixtures as eluent to give 29 as a colourless oil (612 mg, 95%);

(Found: C, 79.8; H, 8.8. C₄₈H₆₃FO₄requires C, 79.7; H, 8.8%);

l_max(CH₂Cl₂)/nm: 279 (log 3/dm³mol^ꢁ1cm^ꢁ13.67) and 286

(3.55);n_max(neat)/cm^ꢁ11726 (C]O); d_H(400.1 MHz, CDCl₃)

0.87–0.96 (12 H, m, EH CH₃), 1.26–1.55 (16 H, m, EH CH₂),

1.65–1.76 (2 H, m, EH CH), 2.76–2.97 (12 H, m, CH₂CH₂), 3.82

(4 H, m, ArOCH₂), 3.90 (3 H, s, COOCH₃), 6.80–6.87 (7 H, m,

SP H & G1-BP H), 7.05–7.11 (5 H, m, SP H & LP H) and 7.88–

7.94 (2 H, m, LP H); d_F(376.6 MHz, CDCl₃) ꢁ111.4; m/z [TOF

ES⁺] 723.3 (MH⁺).

Methyl-4-ﬂuoro-3-iodobenzoate. A solution of 3-iodo-4-ﬂuo-

rotoluene (5.00 g, 21.2 mmol), water (33 cm³), and pyridine (10

cm³) was heated in an oil bath held at 60 ^ꢀC. Potassium

permanganate (10.4 g, 65.8 mmol) was added in portions to the

hot mixture over a 5 h period. After addition, the reaction

mixture was stirred for another 2.5 h and then room temperature

for 12 h. The reaction was ﬁltered and the manganese dioxide

was washed with water (3 ꢂ 7 cm³). The ﬁltrate was collected and

the solution concentrated. Hydrochloric acid (3 M, 40 cm³) was

added to the residue, and the mixture was extracted with ether (4

ꢂ 20 cm³). The ether extracts were combined, washed with brine

(30 cm³), and dried over anhydrous magnesium sulfate, and

ﬁltered. The ﬁltrate was collected and the solvent was removed to

give crude 3-iodo-4-ﬂuorobenzoic acid (z2.52 g, z45%) as

a white solid, which was used without further puriﬁcation.

Concentrated sulfuric acid (30 drops) was carefully added to

a solution of the crude 4-ﬂuoro-3-iodobenzoic acid (z2.52 g) in

methanol (30 cm³). The mixture was heated at reﬂux under argon

for 18 h and then allowed to cool to room temperature. The

solvent was removed and the residue was puriﬁed by column

chromatography over silica using dichloromethane:light petro-

leum (1:20 to 1:3) mixtures as eluent to give methyl-4-ﬂuoro-3-

iodobenzoate as a colourless oil (2.59 g, 97%), which solidiﬁed to

a white solid at room temperature on standing; mp 42–43 ^ꢀC;

(Found: C, 34.4; H, 2.1. C₈H₆FIO₂requires C, 34.3; H, 2.2%);

l_max(CH₂Cl₂)/nm: 278 sh (log 3/dm³mol^ꢁ1cm^ꢁ12.93) and 289 sh

(2.77); n_max(ﬁlm)/cm^ꢁ11723 (C]O); d_H(400.2 MHz, CDCl₃)

3.93 (3 H, s, CH₃), 7.12 (1 H, m, ArH), 8.02 (1 H, m, ArH) and

8.47 (1 H, m, ArH); d_F(376.5 MHz, CDCl₃) ꢁ86.7.

Methyl-3,5-bis[2-(4-{2-ethylhexyloxy}phenyl)acetylen-1-yl]ben-

zoate 23. Tetrakis(triphenylphosphine)palladium(0) (85 mg,

0.074 mmol) was added to a deoxygenated (by placing under

vacuum and backﬁlling with argon) mixture of methyl-3,5-diio-

dobenzoate (410 mg, 1.06 mmol), 18 (730 mg, 3.17 mmol),

copper iodide (60 mg, 0.315 mmol), triethylamine (6 cm³), and

tetrahydrofuran (6 cm³). The mixture was deoxygenated again

and then heated under argon in an oil bath held at 77 ^ꢀC for 28 h.

The reaction was cooled to room temperature and the solvents

were removed. The residue was puriﬁed by column chromatog-

raphy over silica using dichloromethane:light petroleum (1:40 to

1:3) mixtures as eluent to give 23 as a light yellow oil (610 mg,

Methyl-3-[2-(3,5-bis{2-[4-(2-ethylhexyloxy)phenyl]acetylen-1-yl}-

phenyl)acetylen-1-yl]-4-ﬂuorobenzoate 28. Tetrakis(triphenyl-

phosphine)palladium(0) (103 mg, 0.09 mmol) was added to

3224 | J. Mater. Chem., 2009, 19, 3213–3227

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97%); (Found: C, 81.1; H, 8.0. C₄₀H₄₈O₄requires C, 81.0; H,

8.2%); l_max(CH₂Cl₂)/nm: 247 sh (log 3/dm³mol^ꢁ1cm^ꢁ14.67), 259

(4.72), 305 (4.98) and 314 sh (4.97); n_max(neat)/cm^ꢁ11728

(C]O), 2212 (ChC); d_H(400.1 MHz, CDCl₃) 0.87–0.98 (12 H,

m, EH CH₃), 1.29–1.59 (16 H, m, EH CH₂), 1.69–1.80 (2 H, m,

EH CH), 3.88 (4 H, m, ArOCH₂), 3.95 (3 H, s, COOCH₃), 6.90

and 7.47 (8 H, AA⁰BB⁰, SP H), 7.82 (1 H, dd, J 1.5, J 1.5, G1-BP

H) and 8.10 (2 H, m, G1-BP H); d_C(100.6 MHz, CDCl₃) 11.1,

14.1, 23.0, 23.8, 29.0, 30.5, 39.3, 52.4, 70.6, 86.4, 91.0, 114.4,

114.6, 124.5, 130.6, 131.5, 133.1, 137.8, 159.8 and 165.9; m/z

[TOF ES⁺] 593.3 (M⁺).

(8 cm³), dried over anhydrous magnesium sulfate, and ﬁltered.

The ﬁltrate was collected and the solvent was removed. The

residue was puriﬁed by column chromatography over silica using

dichloromethane:light petroleum (1:30 to 1:5) mixtures as eluent

to give 26 as a colourless oil (560 mg, 93% for the two steps with

respect to 24); (Found: C, 73.8; H, 8.6. C₃₉H₅₅BrO₂requires C,

73.7; H, 8.7%); l_max(CH₂Cl₂)/nm: 279 (log 3/dm³mol^ꢁ1cm^ꢁ1

3.76) and 286 (3.68); d_H(400.2 MHz, CDCl₃) 0.93–1.04 (12 H, m,

EH CH₃), 1.33–1.64 (16 H, m, EH CH₂), 1.72–1.83 (2 H, m, EH

CH), 2.90 (8 H, s, CH₂CH₂), 3.88 (4 H, m, ArOCH₂), 4.50 (2 H, s,

ArCH₂Br), 6.90 and 7.13 (8 H, A⁰BB⁰, SP H), 6.96 (1 H, br dd,

G1-BP H) and 7.09 (2 H, br d, G1-BP H); d_C(100.6 MHz,

CDCl₃) 11.1, 14.1, 23.0, 23.8, 29.0, 30.5, 33.9, 36.9, 38.0, 39.4,

70.4, 114.4, 126.8, 129.0, 129.2, 133.3, 137.6, 142.4 and 157.7; m/z

[microTOF ES⁺] 657.3, 659.3 (M⁺+ Na).

Methyl-3,5-bis[2-(4-{2-ethylhexyloxy}phenyl)ethylen-1-yl]ben-

zoate 24. 10% Palladium on carbon (125 mg) was added to

a solution of 23 (600 mg, 1.01 mmol), ethyl acetate (20 cm³), and

methanol (20 cm³). The mixture was deoxygenated (by placing

under vacuum and backﬁlling with argon) four times. A

hydrogen balloon was attached and the mixture was brieﬂy

degassed under vacuum and backﬁlled with hydrogen four times.

The mixture was stirred at room temperature under hydrogen for

14 h and then passed through a plug of silica using dichloro-

methane as eluent (the silica was poured into excess water

immediately to quench the catalyst). The ﬁltrate was collected

and the solvent was removed. The residue was puriﬁed by

column chromatography over silica using dichloromethane:light

petroleum (1:40 to 1:3) mixtures as eluent to give 24 as a col-

ourless oil (587 mg, 97%); (Found: C, 80.0; H, 9.45. C₄₀H₅₆O₄

requires C, 80.0; H, 9.4%); l_max(CH₂Cl₂)/nm: 280 (log 3/dm³

mol^ꢁ1cm^ꢁ13.83), 286 (3.81) and 295 sh (3.37); n_max(neat)/cm^ꢁ1

1726 (C]O); d_H(400.1 MHz, CDCl₃) 0.86–0.97 (12 H, m, EH

CH₃), 1.27–1.60 (16 H, m, EH CH₂), 1.67–1.76 (2 H, m, EH CH),

2.79–2.93 (8 H, m, CH₂CH₂), 3.82 (4 H, m, ArOCH₂), 3.92 (3 H,

s, COOCH₃), 6.83 & 7.07 (8 H, AA⁰BB⁰, SP H), 7.10 (1 H, s, G1-

BP H) and 7.73 (2 H, s, G1-BP H); d_C(100.6 MHz, CDCl₃) 11.1,

14.1, 23.0, 23.8, 29.0, 30.5, 37.0, 38.0, 39.4, 52.0, 70.5, 114.4,

127.2, 129.2, 130.1, 133.2, 133.6, 142.1, 157.7 and 167.4; m/z

[TOF ES⁺] 601.4 (MH⁺).

1-[3,5-Bis(2-{4-[2-ethylhexyloxy]phenyl}ethylen-1-yl)benzyl]-5-

[4-ﬂuoro-3-(2-{3,5-bis[2-(4-{2-ethylhexyloxy}phenyl)ethylen-1-yl]-

phenyl}ethylen-1-yl)phenyl]-3-n-propyl-1H-1,2,4-triazole 33.

A

mixture of 29 (2.49 g, 3.45 mmol), lithium hydroxide (165 mg,

6.89 mmol), water (9 cm³), methanol (9 cm³), and tetrahydro-

furan (20 cm³) was heated under argon in an oil bath held at 63

^ꢀC for 4 h. The reaction mixture was allowed to cool to room

temperature and the solvent was removed. Hydrochloric acid (3

M, 20 cm³) was added to the residue. The mixture was extracted

with dichloromethane (3 ꢂ 30 cm³). The dichloromethane

extracts were combined, washed with brine (35 cm³), dried over

anhydrous magnesium sulfate, and ﬁltered. The ﬁltrate was

collected and the solvent was removed. The mixture was puriﬁed

by column chromatography over silica using dichloromethane:-

light petroleum (0:1 to 1:0) and ethyl acetate:dichloromethane

(1:4 to 2:1) mixtures as eluent to give 3-[2-(3,5-bis{2-[4-(2-eth-

ylhexyloxy)phenyl]ethylen-1-yl}phenyl)ethylen-1-yl]-4-ﬂuoroben-

zoic acid 30 (2.19 g, 90%) as a colourless oil, which was used

immediately. A mixture of thionyl chloride (1.1 cm³) and 30 (2.17

g, 3.06 mmol) was heated at reﬂux for 13 h under argon. The

reaction was allowed to cool and the excess thionyl chloride was

removed by evaporation under reduced pressure to give crude

3-[2-(3,5-bis{2-[4-(2-ethylhexyloxy)phenyl]ethylen-1-yl}phenyl)-

ethylen-1-yl]-4-ﬂuorobenzoyl chloride 31 (z2.23 g, z3.06 mmol)

as a brownish oil, which was used without puriﬁcation. A solution

of triethylamine (1.2 cm³) in chloroform (6 cm³) was added

dropwise to a mixture of 31 (z2.23 g, z3.06 mmol), ethyl

butyrimidate hydrochloride (510 mg, 3.34 mmol), and chloroform

(10 cm³) under argon. The reaction was stirred at room temper-

ature for 67 h. The solvent was removed and the residue was

dissolved into a mixture of water (30 cm³) and dichloromethane

(30 cm³). The aqueous layer was separated and the organic layer

was washed with water (4 ꢂ 20 cm³) and brine (20 cm³), dried over

anhydrous sodium sulfate, and ﬁltered. The ﬁltrate was collected

and the solvent was removed to give 32 (z2.45 g) as a brownish

oil, which was used without further puriﬁcation. 26 (900 mg, 1.42

mmol) was added in small portions to a mixture of hydrazine

monohydrate (369 mg, 7.36 mmol) and ethanol (10 cm³) heated at

reﬂux under air. After addition (2 h), the mixture was kept at

reﬂux under argon for 26 h. The reaction was allowed to cool to

room temperature and the solvent was removed. The residue was

dissolved in dichloromethane (40 cm³), dried over anhydrous

sodium sulfate, and ﬁltered. The ﬁltrate was collected and the

3,5-Bis[2-(4-{2-ethylhexyloxy}phenyl)ethylen-1-yl]benzyl bromide

26. Lithium aluminium hydride (72 mg, 1.90 mmol) was added to

a mixture of 24 (570 mg, 0.95 mmol) and anhydrous tetrahy-

drofuran (20 cm³). The reaction mixture was stirred at room

temperature under argon for 40 min and then heated in an oil

ꢀ

bath held at 60 C for 2 h. The mixture was allowed to cool to

room temperature and carefully poured into a mixture of ice and

water (z60 cm³). The mixture was extracted with ethyl acetate

(6 ꢂ 20 cm³). The ethyl acetate extracts were combined, washed

with brine (50 cm³), dried over anhydrous magnesium sulfate and

ﬁltered. The ﬁltrate was collected and the solvent was removed to

give crude methyl-3,5-bis[2-(4-{2-ethylhexyloxy}phenyl)ethylen-

1-yl]benzyl alcohol 25 (z543 mg) as a colourless oil, which was

used directly in the next step. Phosphorus tribromide (0.4 cm³,

4.21 mmol) was added to 25 (z543 mg, 0.95 mmol) and then the

mixture was heated under argon in an oil bath held at 90 ^ꢀC for

14 h. The mixture was cooled to room temperature and diluted

with ether (8 cm³). The mixture was cooled to 0–2 ^ꢀC and slowly

and carefully quenched with water (4 cm³). The two layers were

separated and the aqueous layer was extracted with ether (3 ꢂ 3

cm³). The organic layers were combined, washed with brine

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J. Mater. Chem., 2009, 19, 3213–3227 | 3225

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solvent was removed under vacuum to give a colourless oil of 3,5-

bis[2-(4-{2-ethylhexyloxy}phenyl)ethylen-1-yl]benzyl hydrazine

27 (z830 mg), which was used without further puriﬁcation. A

solution of 27 in chloroform (5 cm³) was added to a solution of 32

(1.00 g, 1.24 mmol) in chloroform (8 cm³) under argon. The

reaction was stirred at room temperature for 14 h. The solvent was

removed and the residue was puriﬁed by column chromatog-

raphy over silica using ethyl acetate:light petroleum (1:50 to 1:10)

mixtures as eluent to give 33 as a colourless oil (929 mg, 49% for

the two steps with respect to 26); (Found: C, 81.4; H, 9.3; N, 3.1.

C₉₀H₁₂₂FN₃O₄requires C, 81.3; H, 9.25; N, 3.2%); l_max

(CH₂Cl₂)/nm: 272 sh (log 3/dm³mol^ꢁ1cm^ꢁ13.96), 277 (3.98) and

286 (3.87); d_H(400.2 MHz, CDCl₃) 0.87–1.02 (24 H, m, EH

CH₃), 1.09 (3 H, t, J 7.4, Pr CH₃), 1.30–1.62 (32 H, m, EH CH₂),

1.70–1.81 (4 H, m, EH CH), 1.92 (2 H, m, Pr CH₂), 2.83 (20 H,

br s, CH₂CH₂), 2.95 (2 H, m, Pr CH₂), 3.85 (8 H, m, ArOCH₂),

5.27 (2 H, s, NCH₂Ar), 6.78–6.91 (13 H, m, SP H & G1-BP H),

6.93 (1 H, br s, G1-BP H), 7.01–7.16 (9 H, m, SP H & LP H),

7.38 (1 H, br m, LP H) and 7.49 (1 H, br dd, LP H); d_F(376.6

MHz, CDCl₃) ꢁ115.6; m/z [MALDI: DCTB] Anal. Calcd for

C₉₀H₁₂₂FN₃O₄: 1327.9 (98%), 1328.9 (100%), 1329.9 (50%),

1331.0 (17%), 1332.0 (3%). Found: 1328.0 (83%), 1329.0 (100%),

1330.0 (67%), 1331.0 (36%), 1332.0 (3%) (M⁺).

CDCl₃) ꢁ115.6; m/z [MALDI: DCTB] Anal. Calcd for

C

₂₇₀H₃₆₃F₃IrN₉O₁₂: 4171.8 (8%), 4172.8, (26%), 4173.8 (55%),

4174.8 (85%), 4175.8 (100%), 4176.8 (92%), 4177.8 (64%), 4178.8

(36%), 4179.8 (17%), 4180.8 (7%), 4181.8 (3%). Found: 4171.9

(17%), 4172.9, (36%), 4173.9 (60%), 4174.9 (79%), 4175.8 (100%),

4176.9 (68%), 4177.9 (46%), 4178.9 (34%), 4179.9 (14%), 4180.9

(9%), 4181.9 (4%) (M⁺). Excess 33 (533 mg), which co-chroma-

1

tographed with and had an identical H NMR to an authentic

sample, was also recovered.

Acknowledgements

We thank CDT Oxford Ltd and EPSRC for ﬁnancial support.

We also thank the EPSRC National Mass Spectroscopy Centre,

Swansea, UK. Professor Paul Burn is recipient of an Australian

Research Council Federation Fellowship (project number

FF0668728).

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a chromatotron using dichloromethane:light

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Article Doi

The development of phenylethylene dendrons for blue phosphorescent emitters

DOI: 10.1039/b820235d

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