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Synthesis and properties of novel aggregation-induced emission compoundswith combined tetraphenylethylene and dicarbazolyl triphenylethylenemoieties

Xiqi Zhang, Zhenguo Chi,* Haiyin Li, Bingjia Xu, Xiaofang Li, Siwei Liu, Yi Zhang and Jiarui Xu *

Received 26th August 2010, Accepted 19th October 2010DOI: 10.1039/c0jm02824j

A novel class of compounds containing tetraphenylethylene and dicarbazolyl triphenylethylene

moieties combined with different spacers is synthesized. The compounds exhibit high thermal stabilities

and aggregation-induced emission properties. The different spacers lead to differences in spatial

conformation structures and spatial electron distributions, and markedly affect the thermal and

photophysical properties of the compounds. The size of the aggregates formed in waterTHF mixtures

decreases with increasing water fractions. The time-resolved emission decay behaviors of the

synthesized compounds in waterTHF mixtures with water fractions from 60% to 99% show three

relaxation pathways in their fluorescence decays.

IntroductionOrganic luminescent materials with aggregation-induced emis-

sion (AIE) properties have attracted considerable attention

because of their potential application in electroluminescence

devices and chemosensors. Since the first AIE compound 1-

methyl-1,2,3,4,5-pentaphenylsilole was reported in 2001 by

Tangs group,1 aggregation-caused quenching (ACQ) is no

longer the almost insurmountable obstacle it once was. Since

then, a large number of AIE compounds have been developed by

various research groups, examples of which include silole,

1,1,2,2-tetraphenylethene (TPE) and 1-cyano-trans-1,2-bis-(4-

methylbiphenyl)ethylene (CN-MBE) derivatives.2

The thermal stability of organic materials is very important for

the stability and lifetime of electroluminescence devices because

the heat generated during the electroluminescent process could

affect material morphology and device performance. This could

eventually cause permanent damage to the device. Hence,

a relatively high glass transition temperature (Tg) is essential for

emissive materials used in optoelectronic applications. Recently,

the synthesis and application of carbazole derivatives as emissive

materials have been of great interest for chemists and material

scientists due to their high thermal stabilities, charge-transport

properties and luminescence.3 Therefore, we have endeavored to

attach carbazole moieties onto AIE materials, and recently

reported a new kind of AIE molecules, triphenylethylene

carbazole derivatives.4 These derivatives exhibit excellent

thermal and device properties, moreover, most of which have

strong blue light emission capabilities. Thus, we are extending

these studies by combining dicarbazolyl triphenylethylene and

tetraphenylethene units into a single compound via synthetic

methodology, and also aim to design materials with potentialtechnological applications.

In this article, we present the synthesis of three new

compounds, in which tetraphenylethene combines dicarbazolyl

triphenylethylene units with different spacers, and their thermal

and optoelectronic properties are also investigated. These

compounds exhibit aggregation-induced emission properties and

high levels of thermal stabilities, which make them promising

candidates as luminescent materials for electroluminescence

applications.

Results and discussion

Synthesis methods

The target compounds were synthesized according to the routes

depicted in Scheme 1. The target compounds possessed

a common structural feature, that is, each molecule could be

divided into two parts: the tetraphenylethylene and the dicar-

bazolyl triphenylethylene moieties. However, the linker con-

necting these two moieties was varied. For P4Bc2, the two

moieties shared one phenyl ring, and for P5Bc2 and P6Bc2, the

two parts were linked by a CC single bond and a phenylene

group, respectively. Thus, to study the influence of the linker on

the properties of the compounds is one of our main purposes.

The synthesis of TPE-PBr was a straightforward (two steps)

procedure using readily available starting material diphenyl-methane. The hydroxy intermediate, TPE-P(OH)Br, was used

without further purification in the next step. And TPE-PBr was

obtained by the dehydration reaction of TPE-P(OH)Br in the

presence of p-toluenesulfonic acid. TPE-Br was synthesized

according to a literature method5 and TBE-Br was purchased

from a commercial source. The aryl boronic acid C2B was

synthesized starting from carbazole according to our previous

procedure.4 The chemical structures of these products were

confirmed with proton and carbon-13 nuclear magnetic reso-

nance spectra (1H NMR and 13C NMR), high resolution mass

spectrometry and elementary analysis.

PCFM Lab and DSAPM Lab, FCM Institute, State Key Laboratory ofOptoelectronic Materials and Technologies, School of Chemistry andChemical Engineering, Sun Yat-sen University, Guangzhou, 510275,China. E-mail: [email protected]; [email protected]; Fax:+86 20 84112222; Tel: +86 20 84111081

Electronic supplementary information (ESI) available: Fig. S1S4. SeeDOI: 10.1039/c0jm02824j

1788 | J. Mater. Chem., 2011, 21, 17881796 This journal is The Royal Society of Chemistry 2011

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

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Thermal and photophysical properties

Thermal properties were investigated by thermal gravimetric

analysis (TGA) and differential scanning calorimetry (DSC), and

are summarized in Table 1. The compounds exhibited high

thermal stabilities. The decomposition temperatures with 5%

weight loss under N2atmosphere (Td) of P4Bc2, P5Bc2and P6Bc2were 496, 538 and 562 C, respectively (Fig. 1). The Td values

increased with the increasing size of the linkers. High glass

transition temperatures (Tg) were essential for emissive materials

used to improve stability and lifetime of devices. TheTgvalues of

P4Bc2, P5Bc2 and P6Bc2 were 126, 156 and 170 C, respectively.

The highTgwere attributed to the effect of the bulky carbazolyl

groups. As expected, Tg values increased with the increasing

linker sizes.

The DSC curves of the samples in the first and second heating

runs are shown in Fig. 2. In the first heating run, the DSC curves

of P5Bc2and P6Bc2showed obvious crystalline melting peaks at

263 and 305 C, respectively. However, for P4Bc2, no melting

peak could be detected under the same condition, which indicates

that the compound had lower crystallizability from solution than

that of P5Bc2and P6Bc2. In the second heating run, only the glass

transition could be observed for each compound. This indicates

that the compounds had very low tendency to crystallize from

their melts. Amorphous materials possessing highTgshould have

better chances of retaining film morphology during device

operation.

It is well-known that an organic molecule may have many

conformational structures. However, among these structures, themost stable one governs the space structure of the molecule,

which affects the planarity of the molecular structure and inter-

molecular packing. The above geometrical factor would directly

affect some physical properties of the compound, such as thermal

transition temperatures (Tg,Tm,etc.) and optical properties (UV,

PL,etc.). The geometrical structures of the isolated molecules of

the compounds in the ground states were optimized on the basis

of B3LYP/6-31G calculations using Gaussian 03.6 To evaluate

the degree of planarity of these systems, the dihedral angles were

measured and are summarized in Table 2. Fig. 3 shows the

position of each plane.

The results of calculation clearly reveal that the molecules are

not planar. In P5Bc2 and P6Bc2, the six dihedral angles are thesame, which indicates that the dicarbazolyl triphenylethylene

moieties in P5Bc2and P6Bc2exhibit the same degree of planarity,

that is why these two compounds show similar crystallization

behavior from their solutions as reflected in their first heating

DSC curves. Although the dihedral angles B2B3, B2B4 and

B3B5 in the three compounds are the same, and B1B2 and B1

B3 are close, the dihedral angle values of B4B5 differ greatly in

P4Bc2and P5Bc2(P6Bc2), with values of 19 and 87. This means

that the two carbazole groups in P4Bc2 are almost coplanar,

however, they are perpendicular to each other in P5Bc2(P6Bc2).

This indicates that P4Bc2has better co-planarity than P5Bc2and

P6Bc2, which leads to larger conjugation and higher rigidity. The

high rigidity of the molecular structure of P4Bc2 may be thereason why the compound cannot form crystals from its solution.

It is well-known that it is not easy to arrange a bulky rigid

molecule into a crystal lattice.

To further study the relationship between their molecular

structures and photophysical properties, we investigated the

photophysical properties of these compounds by UV-Vis

absorption spectroscopy (UV) in solution and photo-

luminescence spectroscopy (PL) in both solution and solid state.

The data are summarized in Table 1.

Fig. 4 outlines the UV absorption and PL emission spectra of

the compounds in dichloromethane (10 mM). The shapes and

Scheme 1 Synthetic routes for the compounds.

Table 1 Thermal and optical properties of the compounds

Tg/CTm/

CTd/C lem

a/nm labsb/nm lem

b/nm FFLb (%) FFL

c (%)

P4Bc2126 NA 496 490 343 474 0.09 1.1P5Bc2156 263 538 456 343 461 0.24 2.6P6Bc2170 305 562 460 344 462 0.32 3.4

a Determined in solid powder. b Determined in dichloromethane.c Determined in cyclohexane.

Fig. 1 TGA curves of the compounds.

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maximum absorption wavelengths (labs) of UV spectra are very

similar. There were two main absorption bands in all the

compounds: one located at ca. 343 nm and the other located atca.293 nm.

The PL emission intensities of the compounds in 10 mM

dichloromethane solutions increased in the order of P6Bc2 >

P5Bc2 > P4Bc2, and the fluorescence quantum yields (FFL) also

increased according to this order, either in dichloromethane

solutions or in cyclohexane solutions. Although P4Bc2 has the

largest conjugation and highest rigidity among the three

compounds as mentioned above, it exhibits the lowest FFLbecause AIE compounds are special systems which are different

from the common dyes. In solution, if the phenyl rings or groups

in an AIE molecule rotate more freely, its fluorescent quantum

yield is lower. As is well-known, the molecular size and effect of

steric hindrance will affect the rotation and a larger molecule

should have lower freedom of rotation. Therefore, the data of

FFLare arranged in the order of P6Bc2> P5Bc2 > P4Bc2. Fig. 5

shows the PL spectra of the compounds in solid powders.

Comparing the PL spectra of the compounds from solutions to

corresponding solid powders, it can be observed that the

maximum emission wavelengths (lem) of P5Bc2 and P6Bc2 are

very close to each other (460 nm) and there are only slightlemblue-shifts (25 nm), suggesting weak intermolecular interac-

tions. However, the lem of the P4Bc2 in solution and in solid

powder were 474 and 490 nm, respectively. The lem are much

longer than those of P5Bc2and P6Bc2in either solutions or solid

powders. For example, compared to P5Bc2 in solid powder, the

lemof P4Bc2was red-shifted by 34 nm.

It is well-known that the highest occupied molecular orbital

(HOMO) and the lowest unoccupied molecular orbital (LUMO),which are related to the redox potentials, are two important

parameters for electroluminescent materials because of their

relationship with the hole/electron-injecting capability of organic

light-emitting devices. Besides, the energy levels are related to the

level of difficulty of p-electron transitions, which is directly

reflected in UV and PL spectra. To measure the HOMO levels of

the synthesized compounds, cyclic voltammetry (CV) was carried

out. The CV curve of P5Bc2is shown in Fig. 6. The CV curves for

Fig. 2 DSC curves upon the first and the second heating runs with 10 C

min1 heating rate.

Table 2 Some dihedral angle parameters of the compounds

Dihedral angles P4Bc2(deg.) P5Bc2(deg.) P6Bc2(deg.)

B1B2 56 60 60B1B3 70 64 64B2B3 76 76 76B2B4 55 55 55B3B5 55 55 55B4B5 19 87 87

Fig. 3 Schematic diagram for the optimization geometries of the

compounds (R represents the tetraphenylethylene moiety).

Fig. 4 UV (left) and PL (right) spectra of the compounds in dichloro-

methane (10 mM).

Fig. 5 PL spectra of the compounds in solid powders.


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P4Bc2 and P6Bc2 are provided in the Electronic Supplementary

Information (Fig. S1). The HOMO energy levels were obtained

using onset oxidation potentials. The energy band gaps (DEg) of

the compounds were estimated from the onset wavelength of

their UV absorptions. The LUMO energy levels were obtained

from the HOMO energy and the energy band gap (DEg

HOMO LUMO).

The HOMO, LUMO and DEgvalues are listed in Table 3. The

DEg values of the compounds were found to be in the range of

2.993.04 eV. Comparing the DEg values of three compounds,

theDEgof P4Bc2was the lowest (2.99 eV), which means that the

p-electron transition of P4Bc2 was the easiest. This may be the

major reason why the P4Bc2 exhibited the longest PL emission

wavelength among the compounds.

To gain insights into differences in the photophysical proper-

ties of the compounds, quantum mechanical computations were

carried out using the Gaussian 03 program.6 On the basis of the

density functional method at the B3LYP/6-31G level after opti-

mizing the structure, the HOMO and LUMO of thesecompounds were obtained, as shown in Fig. 7. The calculated

values are also summarized in Table 3 in brackets. As can be seen

from Table 3, the experimental values are not in good agreement

with the calculated values. P4Bc2 had a larger dipole moment

(2.1616 Debye) than P5Bc2 and P6Bc2. As expected, P5Bc2 and

P6Bc2 showed similar electron distributions in either their

HOMO or LUMO orbitals. This may be the reason why P5Bc2and P6Bc2exhibited very close UV and PL spectra. However, in

either the HOMO or LUMO orbital, the electron distributions of

P4Bc2were significantly different from P5Bc2and P6Bc2. On the

HOMO orbital of P4Bc2, the electron distributions in the two

carbazole groups had equal opportunities. However, for P5Bc2

and P6Bc2, the electron distributions in the two carbazole groupswere different. The carbazole group on the molecular backbone

had a dense electron distribution. Comparing the electron

distributions in the LUMO orbitals, the electron distribution

density in the tetraphenylethylene moiety was rather high in

P4Bc2. However, the tetraphenylethylene moieties in P5Bc2 and

P6Bc2 had almost no electron distribution. Thus, based on the

theoretical calculations, it is clear that the different electron

distributions of the compounds led to their different emission

properties.

AIE properties

To determine whether the compounds have aggregation-induced

emission properties, the UV absorption and PL emission

behaviors of their diluted mixtures were studied in a mixture of

waterTHF with different water fractions. Since the compounds

were insoluble in water and soluble in THF, increasing the water

fraction in the mixed solvent could change their existing forms

from a solution in pure THF to the aggregated particles in the

mixtures, which will result in changes in their UV and PL spectra.

The PL spectra of 10 mM of P5Bc2 in waterTHF mixtures

with different water contents are shown in Fig. 8 as an example

(the others are shown in Fig. S2). For P5Bc2in pure THF and in

the mixtures with water fraction 60%, the PL

intensity slightly decreased with increasing water fraction up to

80%. A dramatic enhancement in luminescence was observed

when the water fraction was up to 90%. While the PL intensity in

pure THF was only 3 (a.u.), it was boosted to 241 (a.u.) in 99%

waterTHF mixture, an enhancement of about 80 times. Similar

effects were observed for the other compounds. This increase in

Fig. 6 CV curve of P5Bc2in dichloromethane.

Table 3 Energy levels of the compoundsa

HOMO/eV LUMO/eV OEg/eVDipole moment(Debye)

P4Bc2 5.53 (5.17) 2.54 (1.71) 2.99 (3.46) 2.1616P5Bc2 5.54 (5.20) 2.52 (1.71) 3.04 (3.49) 2.0779P6Bc2 5.55 (5.20) 2.53 (1.74) 3.02 (3.46) 2.0140

a Data in parentheses obtained from theoretical calculation. Fig. 7 Calculated spatial electron distributions of LUMO and HOMO

of the compounds.


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PL intensity can be attributed to an AIE effect caused by the

formation of molecular aggregates, in which the restriction of

intramolecular rotations leads to increased fluorescent emission.

To quantitatively estimate the AIE process, the PL quantum

yields (FFL) were calculated for the compounds in the waterTHF mixtures with different water fractions using 9,10-diphe-

nylanthracene as the reference (Fig. 9). The FFLcurves could be

divided into four stages according to water fraction (x): (1) 0

50%, almost no change; (2) 50% < x # 60%, slight increase; (3)

60% < x #80%, slight decrease; and (4) >80%, significant

increase. The variation of the FFLvalues with the water fractions

was in accordance with that of PL intensity. Compared to the

FFLobtained in pure THF, theFFLof P4Bc2, P5Bc2and P6Bc2in

waterTHF mixtures with 99% water fraction increased 200-,

190- and 121-fold, respectively. For example, in THF, the FFLof

P4Bc2 was 0.14%; but in waterTHF mixtures with 99% water

fraction, the FFLwas 28%.

As the water fraction was increased, decreases in PL intensityand FFLwere often observed, such as in Stage (3), in some AIE

compounds with AIE properties. The reasons for these remain

unclear. Liet al.7 considered that the reason was the decreasing

number of emissive molecules located at the surface of the

aggregates as the aggregates increase in size upon increasing

amounts of water being added to the mixtures. In other words,

after aggregation, the particle size further increased after the

addition of more water. We thus measured the particle size using

a laser light scattering system. The effective diameters (EDs) and

polydispersity indexes (PDIs) are summarized in Table 4. To

demonstrate the ED changes in the particles more visually, we

plotted the changes in ED versus water fractions in the water

THF mixtures (Fig. 10). When the water fraction is 50% in the waterTHF mixture.

The spectra showed absorption tails extending well into the long

wavelength region. This indicates that the molecules had aggre-gated into nanoparticles in the mixtures. It was considered that

the Mie effect of nanoparticles could cause such leveling-off of

tails in the absorption spectra.

Recently, a time-resolved fluorescence technique was used to

elucidate the mechanism of AIE. It was found that most of the

addition of water to an AIE solution led to a change in the

emission lifetime of AIE and that excited molecule decay

occurred through two relaxation pathways.8,9 In solution, the

decay was through a rapid pathway, and in aggregation it was

mainly through a slow one. To the best of our knowledge, there

are few three decay pathways reported for the AIE system.10

Time-resolved emission decay behaviors of the synthesized

compounds in waterTHF mixtures with water fractions from60% to 99% were studied in this article. As an example, the time-

resolved fluorescence curves of P5Bc2 are illustrated in Fig. 13

(the others are shown in Fig. S4), and the lifetime data are

summarized in Table 5. As can be seen from the table, there are

three relaxation pathways in their fluorescence decays. This

implies that the time-resolved PL spectra of the compounds

include independent emissions from the segments with different

p-conjugation lengths because multiple lifetimes have been

detected. For these three compounds, different pathways played

Fig. 8 PL spectra of P5Bc2in waterTHF mixtures (10 mM).

Fig. 9 PL quantum yields of the compounds in waterTHF mixtures

with water fraction (10 mM).

Table 4 Effective diameter and polydispersity index of the compoundsin waterTHF mixtures with different water fractiona

Water (v%)

P4Bc2 P5Bc2 P6Bc2

ED PDI ED PDI ED PDI

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different predominant roles. For example, in the mixture with

60% water fraction, the excited molecules of P4Bc2mainly decay

through the second pathway (A2 0.51). However, for P5Bc2and P6Bc2, the excited states mainly decay through the first

pathway with A1 0.69 and A1 0.84, respectively. With

increasing water fractions in the solvent mixture, the weighted

mean lifetimes exhibited V-shape changes (Fig. 14) in

accordance with the changes of PL intensities and quantum

yields, which may due to the combined action of the increasing

solvent polarity and the molecular aggregation.

Conclusions

A novel class of AIE compounds containing tetraphenylethylene

and dicarbazolyl triphenylethylene moieties combined with

different spacers was synthesized. The compounds possessed

high thermal stability with Tgof 126170 C andTdof 496562

C. The different spacers led to differences in spatial conforma-

tion structures and spatial electron distributions, and markedly

affected the thermal and photophysical properties of the

compounds synthesized. The size of the aggregated particles

formed from the waterTHF mixtures decreased with increasingwater fractions. Studies of the time-resolved emission decay

behaviors of the synthesized compounds in waterTHF mixtures

showed that there exist three relaxation pathways in their fluo-

rescence decay processes.

Fig. 10 Effective diameters of the compounds in waterTHF mixtures

with water fraction (10 mM). Note:

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Experimental

Bromotriphenylethylene, diphenylmethane, 4-bromobenzophe-

none, 4-(4-bromophenyl)benzophenone, n-butyl-lithium inhexane (2.2 M), tetrakis(triphenylphosphine)palladium(0), p-

toluenesulfonic acid, tricaprylylmethyl-ammonium chloride

(Aliquat 336) and tetrabutylammonium perchlorate (electro-

chemical grade) purchased from Alfa Aesar were used as

received. All other reagents and solvents were purchased as

analytical grade from Guangzhou Dongzheng Company (China)

and used without further purification. Tetrahydrofuran (THF)

was distilled from sodium/benzophenone. Ultra-pure water was

used in the experiments. TPE-Br5 and C2B4 were synthesized

according to the literature methods.1H NMR and 13C NMR spectra were measured on a Mercury-

Plus 300 spectrometer [CDCl3 or DMSO-d6 as solvent and tet-

ramethylsilane (TMS) as the internal standard]. Mass spectra(MS) were measured on a Thermo MAT95XP-HRMS spec-

trometer. Elemental analyses (EA) were performed with an

Elementar Vario EL elemental analyzer. Fluorescence spectra

were measured on a Shimadzu RF-5301pc spectrometer with

a slit width of 1.5 nm for both excitation and emission. Time-

resolved emission decay behaviors were done with an Endin-

burgh Instruments Ltd spectrometer (FLSP920) and the data

were processed according to the literature method.8 Differential

scanning calorimetry (DSC) curves were obtained with

a NETZSCH thermal analyzer (DSC 204) at heating and cooling

rates of 10 C min1 under N2 atmosphere. Thermogravimetric

analyses (TGA) were performed with a thermal analyzer (TA

Instruments Inc. A50) under N2atmosphere with a heating rateof 20 C min1. The fluorescence quantum yields (F) of all the

compounds in different solvents or THFwater mixtures were

evaluated using 9,10-diphenylanthracene as in reference 11.

Cyclic voltammetry (CV) measurement was carried out on

a Shanghai Chenhua electrochemical workstation CHI660C in

a three-electrode cell with a Pt disk counter electrode, a Ag/AgCl

reference electrode, and a glassy carbon working electrode. All

CV measurements were performed under an inert argon atmo-

sphere with supporting electrolyte of 0.1 M n-Bu4NClO4 in

dichloromethane at a scan rate of 100 mV s1 using ferrocene as

standard. The lowest unoccupied molecular orbital/highest

occupied molecular orbital (LUMO/HOMO) energy gaps DEgfor the compounds were estimated from the absorption edge of

UV-Vis absorption spectra.

The sizes of the particles of the compounds in THFwater

mixtures were determined using a ZetaPALS dynamic light

scattering system (Brookhaven, ZetaPALS Zeta Potential

Analyzer).

The waterTHF mixtures with different water fractions were

prepared by slowly adding distilled water into the THF solutionof samples under ultrasound at room temperature. For example,

a 70% water fraction mixture was prepared in a volumetric flask

by adding 7 mL distilled water into 3 mL THF solution of the

sample. The concentrations of all samples were adjusted to 10

mM after adding distilled water.

Synthesis of TPE-PBr

A 2.2 M solution of n-butyllithium in hexane (23.8 mmol, 10.8

mL) was added into a solution of diphenylmethane (4.00 g, 23.8

mmol) in anhydrous tetrahydrofuran (50 mL) at 0 C under an

argon atmosphere. After stirring for 1 h at that temperature, the

4-(4-bromophenyl)benzophenone (6.41 g, 19.0 mmol) was addedand the reaction mixture was stirred for 10 h allowing the

temperature to rise gradually to room temperature. Then the

reaction was quenched with an aqueous solution of ammonium

chloride and the mixture was extracted with dichloromethane.

The organic layer was evaporated after drying with anhydrous

sodium sulfate and the resulting crude product was dissolved in

toluene (100 mL). The p-toluenesulfonic acid (1.00 g, 5.8 mmol)

was added, and the mixture was refluxed overnight and cooled to

room temperature. The mixture was evaporated and the crude

product was purified by silica gel column chromatography using

n-hexane as eluent to yield a light green powder (4.15 g, 45%). 1H

NMR (300 MHz, CDCl3) dppm: 7.49 (d, 2H), 7.38 (d, 2H), 7.28

(d, 2H), 7.126.98 (m, 17H). FT-IR (KBr) n/cm1: 3025, 1595,1478, 813, 764, 699, 578. HRMS (EI), m/z: 488 ([M]+, calcd for

C32H23Br, 488); Anal. calc. for C32H23Br: C 78.85, H 4.76, Br

16.39; Found: C 78.78, H 4.72.

Synthesis of C2B

To a stirred solution of C2Br (6.0 g, 9.0 mmol) in anhydrous THF

(100 mL) was added n-butyllithium solution in hexane (2.2 M, 6

mL, 13.2 mmol) dropwise slowly at 78 C. The mixture was

stirred at 78 C under Ar gas for an additional 5 h. B(OCH3)3(2.2 mL) was added quickly at 78 C and the mixture was

stirred overnight allowing the temperature to rise gradually to

room temperature. Water (40 mL) was added and then acidifiedwith conc. HCl. The mixture was stirred for a further 2 h. The

product was extracted into ethyl acetate (3 50 mL). The

organic layer was separated and dried over anhydrous sodium

sulfate. After removing the solvent under reduced pressure, the

residue was chromatographed on a silica gel column with

acetone/CH2Cl2(1 : 20 by volume) as eluent to give C2B (2.1 g,

55% yield). 1H NMR (300 MHz, DMSO-d6) dppm: 7.14 (s, 1H),

7.257.58 (m, 16 H), 7.627.78 (m, 8 H), 7.98 (s, 2 H, B(OH)2),

8.208.30 (m, 4 H); MS (EI), m/z: 586 ([M(B(OH)2)]+, calcd for

C44H29, 585); Anal. calc. for C44H31BN2O2: C 83.81, H 4.96, N

4.44; Found: C 83.64, H 4.89, N 4.48.

Fig. 14 Relationship between the weighted mean lifetimes of the

synthesized compounds and the water fractions in waterTHF mixtures.


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Synthesis of P4Bc2

Bromotriphenylethylene (0.24 g, 7.16 104 mol) andC2B(0.30

g, 4.76 104 mol) were dissolved in the mixture of toluene (20

mL), Aliquat 336 (5 drops) and 2 M potassium carbonate

aqueous solution (5 mL). The mixture was stirred at room

temperature for 0.5 h under Ar gas followed by adding Pd(PPh3)4(0.010 g, 8.70 106 mol) and then heated to 90 C for 24 h.

After that the mixture was poured into water and extracted threetimes with ethyl acetate. The organic layer was dried over

anhydrous sodium sulfate. After removing the solvent under

reduced pressure, the residue was chromatographed on a silica

gel column with n-hexaneCH2Cl2(3 : 1 by volume) as eluent to

giveP4Bc2(0.22 g, 55% yield).1H NMR (300 MHz, CDCl3)dppm:

6.92 (s, 4H), 6.957.18 (m, 16H), 7.277.36 (m, 4H), 7.417.67

(m, 16H), 8.138.21 (m, 4H); 13C NMR (75 MHz, CDCl3) dppm:

143.84, 143.74, 143.62, 143.08, 142.21, 141.50, 140.92, 140.70,

139.40, 137.28, 137.15, 135.34, 132.23, 131.50, 131.33, 129.62,

129.14, 127.85, 127.46, 126.97, 126.72, 126.18, 123.66, 120.56,

120.24, 110.08; MS (EI) calcd. for C64H44N2 840, found 840;

Anal. calc. for C64H44N2: C 91.40, H 5.27, N 3.33; Found: C

91.29, H 5.30, N 3.28.

Synthesis of P5Bc2

1-Bromo-4-(1,2,2-triphenylethenyl)benzene (0.295 g, 7.17 104

mol) and C2B (0.30 g, 4.76 104 mol) were dissolved in the

mixture of toluene (20 mL), Aliquat 336 (5 drops) and 2 M

potassium carbonate aqueous solution (5 mL). The mixture was

stirred at room temperature for 0.5 h under Ar gas followed by

adding Pd(PPh3)4(0.010 g, 8.70 106 mol) and then heated to

90 C for 24 h. After that the mixture was poured into water and

extracted three times with ethyl acetate. The organic layer was

dried over anhydrous sodium sulfate. After removing the solvent

under reduced pressure, the residue was chromatographed on

a silica gel column with n-hexaneCH2Cl2 (3 : 1 by volume) as

eluent to give P5Bc2 (0.20 g, 46% yield). 1H NMR (300 MHz,

CDCl3) dppm: 7.017.15 (m, 16H), 7.177.24 (m, 3H), 7.277.40

(m, 7H), 7.407.72 (m, 18H), 8.17 (d, 4H,J 7.8 Hz); 13C NMR

(75 MHz, CDCl3) dppm: 143.86, 143.17, 142.08, 141.39, 141.08,

140.92, 140.62, 139.44, 138.19, 137.39, 137.32, 136.16, 133.32,

132.20, 132.03, 131.51, 130.26, 129.31, 129.12, 127.93, 127.88,

127.83, 127.56, 127.02, 126.66, 126.18, 123.70, 120.59, 120.27,

110.08, 110.01; MS (EI) calcd. for C70H48N2 916, found 916;

Anal. calc. for C70H48N2: C 91.67, H 5.28, N 3.33; Found: C

91.71, H 5.23, N 2.97.

Synthesis of P6Bc2

TPE-PBr (0.35 g, 7.18 104 mol) andC2B(0.30 g, 4.76 104

mol) were dissolved in the mixture of toluene (20 mL), Aliquat

336 (5 drops) and 2 M potassium carbonate aqueous solution (5

mL). The mixture was stirred at room temperature for 0.5 h

under Ar gas followed by adding Pd(PPh3)4(0.010 g, 8.70 106

mol) and then heated to 90 C for 24 h. After that the mixture

was poured into water and extracted three times with ethyl

acetate. The organic layer was dried over anhydrous sodium

sulfate. After removing the solvent under reduced pressure, the

residue was chromatographed on a silica gel column with n-

hexaneCH2Cl2(6 : 1 by volume) as eluent to give P6Bc2(0.22 g,

47% yield). 1H NMR (300 MHz, CDCl3) dppm: 7.027.17 (m,

16H), 7.27.36 (m, 8H), 7.377.73 (m, 24H), 8.17 (d, 4H, J 7.5

Hz); 13C NMR (75 MHz, CDCl3) dppm: 143.90, 143.11, 142.36,

142.08, 141.56, 141.38, 141.20, 140.93, 140.66, 139.87, 139.50,

138.38, 137.42, 136.38, 132.21, 132.04, 131.61, 131.54, 130.39,

129.16, 128.53, 127.96, 127.59, 127.42, 127.34, 127.04, 126.82,

126.71, 136.23, 123.73, 120.62, 120.32, 110.09, 110.02; MS (EI)

calcd. for C76H52N2992, found 992; Anal. calc. for C76H52N2: C

91.90, H 5.28, N 2.82; Found: C 91.85, H 5.21, N 2.78.

Acknowledgements

The authors gratefully acknowledge the financial support from

the National Natural Science Foundation of China (Grant

numbers: 50773096 and 51073177), the Start-up Fund for

Recruiting Professionals from 985 Project of SYSU, the

Science and Technology Planning Project of Guangdong Prov-

ince, China (Grant numbers: 2007A010500001-2,

2008B090500196), Construction Project for University-Industry

cooperation platform for Flat Panel Display from The

Commission of Economy and Informatization of Guangdong

Province (Grant numbers: 20081203) and the Open ResearchFund of State Key Laboratory of Optoelectronic Materials and

Technologies.

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