CA2360826C - Conjugated polycarbazole derivatives and process for the preparation thereof - Google Patents

Abstract

The invention relates to conjugated polycarbazole derivates comprising units of the formula:

Description

CONJUGATED POLYCARBAZOLE DERIVATIVES AND PROCESS FOR
THE PREPARATION THEREOF
The present invention pertains to improvements in the field of conjugated polymers. More particularly, the invention relates to conjugated polycarbazole derivatives and to a process for the preparation thereof.
A conjugated polymer is a polymer which possesses a delocalized pi-electron system along its backbone as described, for example, by D.J. Sandman in "Trends in Polymer Science", Vol. 2, p. 44 (1994). Conjugated polymers are considered as a very important class of electroactive and photoactive materials by both academic and industrial laboratories. The synthesis over the last twenty years of highly pure polyacetylene, polythiophenes, polyphenylenes, polyfluorenes, ladder polymers and other conjugated polymers optimized physical properties has led to a significant improvement in the performance of these polymeric materials and to a better understanding of their structure-property relationships. However, up to now, only poorly conjugated poly(N-alkyl-3,6-carbazole) derivatives are available so that these are not optimized for the development of light-emitting diodes, electrochromic windows, electrochemical sensors, photovoltaic cells, photoconductors, photorefractive materials, transistors, etc.
It is therefore an object of the present invention to provide conjugated polycarbazole derivatives having improved optical and electrochemical properties.
According to one aspect of the invention, there is provided a conjugated poly(N-alkyl-2,7-carbazole) of formula (I):

/ /
~ O) n N

R

wherein R represents a linear or branched alkyl group having 1 to 22 carbon atoms, and n is an integer of about 3 to about 100, with the proviso that when R
is a decyl radical, n cannot represents an integer from 2 to 6.
The present invention also provides, in another aspect thereof, a process for preparing a conjugated poly(N-alkyl-2,7-carbazole) of the formula (I) defined above, which comprises treating a N-alkyl-2,7-difunctionnalized carbazole of formula (II):
x ~ / \ / x O>
I
R
wherein R is as defined above and X represents a trifluoromethanesulfonyl 1 o group or a halogen atom selected from the group consisting of bromine, chlorine and iodine atoms, with triphenylphosphine and 2,2'-bipyridine in the presence of zinc and nickel chloride, to cause polymerization of the compound of formula (II).
According to a further aspect of the invention, there is provided a conjugated polymer comprising alternated units of formula (I'):

/ \ /

N

R

wherein R is as defined above.
The conjugated polycarbazole derivatives according to the invention, comprising units of formula (I'), have interesting optical and 2 o electrochemical properties which render them suitable for use in the manufacture of light-emitting diodes, electrochromic windows, electrochemical sensors, photovoltaic cells, photoconductors, photorefractive materials and the like.

The following non-limiting examples illustrate the invention, reference being made to the accompanying drawings, in which:
Figure 1 is the absorption (Abs.) and emission (PL) spectra of poly(N-octyl-2,7-carbazole) in choroform and in the solid state; and Figure 2 is the cyclic voltammogram of poly(N-octyl-2,7-carbazole) cast on a platinum electrode, in acetonitrile containing O.1M N Bu4NBF4, at a scan rate of 10 mV/s.
EXAMPLE 1: Preparation of poly(N-octyl-2,7-carbazole) Following the procedure developed by Smith and Brown and reported in J. Am. Chem. Soc., Vol. 73, p. 2438 (1951), 4,4'-dinitro-2-biphenylamine (Aldrich Co.) was treated with NaNOz and NaN3 to give the corresponding azide via the transformation of the amino group into a diazonium salt. A ring closure reaction, assured by a nitrene intermediate, was carried out to give 2,7-dinitrocarbazole in a 66 % yield. This compound was then reduced using SnCl2 in a mixture of acetic acid/HCl (5 :1) to give 2,7-diaminocarbazole in a 78 % yield. Then, the amino groups of the resulting product were transformed to iodine atoms; the reaction was carried out in a 3M HCI solution using NaN02 and KI. N-octyl-2,7-diiodocarbazole was prepared in a 93% yield from 2,7-diiodocarbazole upon reaction with KZC03 and bromooctane in anhydrous DMF at 80 °C. All monomers were characterized by NMR
and mass spectrometry. Homopolymerization was achieved by a Yamamoto reaction described in Macromolecules, Vol. 25, p. 1214 (1992), using N-octyl-2,7-diiodocarbazole as the starting material and triphenylphosphine, 2,2'-bipyridine, and zinc and NiClz as catalysts. Poly(N-octyl-2,7-carbazole) was obtained in a 78 % yield.
The synthetic scheme is summarized as follows:

1 ) NaN02, H2S04 02N ~ ~ ~ ~ N02 AcOH OZN ~ ~ ~ ~ N02 2) NaN3 NH2 Y=72 % N3 (1 ) (2) SnCl2 0, -N2 ' ~ AcOH/HCl (5:1 ) ' Y=66 % 02N \ / \ / N02 L-12[V \ / \ / NH2 H (3) Y= 78 (4) 1 ) HCI ~aq.~, NaN02 . . 1 ) K2C03, DMF
I \ / \ / I 80 C ~ I \ / \ / I
N
2) KI ~aq.~, 24 h, r.t. H 2) C8H»Br (5) Global yield for step (6) 4 and 5 = 38%
PPh3, Zn, NiCl2 2,2'-bipyridine N DMAc, 80 °C, 3 d N n Y=78%
C$H» CBH~~
It is also possible to use, instead of N-alkyl-2,7-diiodocarbazole, N-alkyl-2,7-dichlorocarbazole which can be obtained from a different synthetic pathway, according to the following scheme:

B(OH)2 CI Pd(PPh3)a Benzene/NaZC03 aq.
CI / \ / \ CI
reflux, 18 h CI Br Y = 93% N02 P(OEt)3 reflux, 24 h Y=60%
K2CO3 .
CBHI~Br CI \ ~ ~ / CI - CI \ ~ ~CI
DMF, 80°C
CgH~7 (9) 24 h H
Y = 86 % K2COg,TBAH
PPh3, Zn, NiCl2 C18H3~Br 2,2'-bipyridine Acetone, reflux, 24 h DMAc, 100°C, 3 d Y = 86 Y = 75 % Ni(COD)2 COD, 2,2'-bipyridine _ _ DMF, 100°C, 2 d / CI \ ~ ~ / CI
Y=75 % [V
C~sH37 (1 R = C8H1~ or ClgH3~
This scheme involves a coupling between 4-chlorophenylboronic acid (Aldrich Co.) and 1-bromo-4-chloro-nitrobenzene (Aldrich Co.), followed by a ring closure using P(OEt)3 and an alkylation of the nitrogen atom in DMF and KZC03 using octylbromide or 1-bromooctadecane.
EXAMPLE 2 : Preparation of poly(N-octyl-2,7-carbazole-alt-9,9-dioctyl-2,7-fluorene) and poly[N-(2-ethylhexyl)-2,7-carbazole-alt-5,5'-(2,2'-bithiophene)].

Alternated copolymers were prepared from Suzuki couplings (described by Ranger, M. et al. in Macromolecules, Vol. 30, p. 768 (1997)) between di-boronic functionalized aromatic units and N-alkyl-2,7-diiodocarbazole derivatives. Poly(N-octyl-2,7-carbazole-alt-9,9-dioctyl-2,7-fluorene) was prepared from a reaction between 2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2y1)-9,9-dioctylfluorene and N-octyl-2,7-diiodocarbazole using (PPh3)4Pd(0) as catalyst in a mixture of THF and 2 M KZC03 aqueous solution. Moreover, Stille couplings (described by Yu, L. et al. in Acc. Chem.
Res., Vol. 29, p. 13 (1996)) between distannyl aromatic derivatives and N-1 o alkyl-2,7-diiodocarbazole derivatives are possible. As an exemple, poly[N-(2-ethylhexyl)-2,7-carbazole-alt-5,5'-(2,2'-bithiophene)] was obtained with a good yield from N-(2-ethylhexyl)-2,7-diiodocarbazole and of 5,5' bis(trimethylstannyl)-2,2'-bithiophene, in presence of Cl2(PPh3)2Pd(0) in THF.
These polymerization reactions are summarized in the following scheme:
O ~ . O
I \ / \ / I + ~g \ / \ / g N ' O O
I CaH~~ CsH~~

Pd(PPh3)4 K2COs i ~ ~ / ~ /
THF, 3 d ~ N~ ~ n Reflux I C8H~~ C8H~~
Y = 75 % C$H 17 I~ \ ~ I + Me3Sn S /S\ SnMe3 N ~ /
I
CgH 17 Pd C12(PPh 3)2 ~ ~ / \
THF \ / \ / ~S / S
Reflux, 3 d N
Y=52%
CaH~~

-EXAMPLE 3 : Preparation of poly (N-octyl-2,7-carbazole) In order to obtain a reactive monomer in better global yield than obtained with 2,7-diiodocarbazole derivatives, N octyl-2,7-bis(trifluoromethanesulfonyl)carbazole was synthesized as follows:
r (0H)2 Pd(PPhg)4 N02 ~ Benzene, KZCOg 2M - -+ ~ H3C ~ ~ ~ ~ OCH3 / / Reflux, 2h OCH3 OCH3 y = 90 % 02N (11) P(OEt)3 Reflux, Sh Y=70%
H3C0 \ ~ ~ / OCH3 N (12) H
NaOH,TBAH
1-bromooctane Acetone, reflux, 24 h Y=91 N Y = 68 % (13) (14) CBH~~ CBH~~
TfZO, DMAP
Pyridine 0°C - r.t., 24 h Y=76%
Pinacolborane* -' PdCl2(dPP~ 0.
Tf0 \ ~ ~ / OTf NEt3, CHZCIz ~p N
(15) EO°C, 24 h Y=59% C8H17 (16) C8Ht7 (15), Pd(PPh3)4>
PPhg, Zn, NiCl2 KzC03 (aq.)/THF
2,2'-bipyiridine reflux 3 d DMF, 80°C, 3 d Y = 86 %
Y=83%
\ ~ ~ / \
N n ~ n CaH~7 ~ BBrg, CHzCl2 HO \ ~ ~ / OH p°C _ r.t., 24h H3C0 \ / \ / OCHg N

- g -The biphenyl unit (11) was obtained using a Suzuki coupling between 4-methoxyphenylboronic acid and 4-bromo-3-nitroanisole in standard conditions.
Then, a Cadogan ring closure reaction was carried out in hot triethylphosphite to give 2,7-dimethoxycarbazole (12) as reported in Macromolecules, Vol. 18, p. 1388 (1985).
This compound was alkylated using finely powdered NaOH, phase transfer agent and primary alkyl bromide in anhydrous acetone. From compound (13), a standard deprotection reaction using BBr3 in methylene chloride was achieved to give 2,7-dihydroxycarbazole (14), in relatively good yields. Finally, monomer (14) was treated with DMAP and trifluoromethanesulfonic anhydride in cold pyridine to give monomers (15) that can undergo Yamamoto, Stifle or Suzuki polycondensation reaction. When necessary, boronic esters can be introduced at the 2,7-positions with pinacolborane and Pd(II) using similar procedure published in J. Org. Chem., Vol. 65, p. 164 (2000) to obtain compound (16) to perform Suzuki polycondensation reaction.
Materials. All chemicals were purchased from Aldrich Co. and were used without further purification.
4,4'-dinitro-2-azidobiphenyl (2): To a solution of 10.0 g (38.6 mmol) of 4,4'-dinitro-2-biphenylamine in a mixture of 200 mL of acetic acid and 40 mL of sulfuric acid at 0°C was added dropwise 5.32 g (77.2 mmol, Aldrich Co.) of sodium nitrite. The mixture was stirred at 5-10°C for 2h after 5.00 g of urea (to destroy the excess nitrous acid), S00 mL of ice-water and 5 g of activated carbon was added. The cold suspension was stirred again for 20 min and filtrated rapidly through a biichner funnel into a flask immersed in an ice bath. A solution of 5.07 g (77.2 mmol, Aldrich Co.) of sodium azide in 100 mL of water was added dropwise to the yellow clear filtrate. The resulting solution was stirred at 0°C for 1 h and at room temperature for 24 h. The mixture was quenched with 500 mL of a solution of NaHC03 in water and extracted three times with ethyl acetate. The organic layer was dried over magnesium sulfate and the solvent was removed under vacuum. Recristallization in ethanol afforded 7.37 g of the title product as a yellow solid. M.P. 171-172°C
(Yield: 72%).

1H NMR (300 MHz, CDC13, ppm): 8.37 (d, 2H, J= 8.8 Hz); 8.20 (d, 1 H, J= 2.2 Hz);
8.16 (dd, 1 H, J = 10.3 and 2.2 Hz); 7.89 (dd, 2H, J = 8.8 and 2.8Hz); 7.79 (d, 1 H, J =
8.1 Hz).
'3C NMR (75 MHz, CDC13, ppm): 143.84; 140.35; 137.98; 133.20; 131.81; 124.29;
120.71; 115.44.
HRMS: Calculated for C12H~N5O4: 285.0498 Found: 285.0505 2,7-dinitrocarbazole (3): To 600 mL of boiling kerosene (first washed with concentrated sulfuric acid) was added very slowly 6.00 g (21.0 mmol) of compound 2. The solution was maintained to reflux for 1 h. After cooling, the solution was kept at 4°C for 24 h. The precipitate was filtered through a biichner funnel and the solid was washed with petroleum ether. Very pure material was obtained by recristallization in ethanol to afforded 3.38 g of the title product. M.P.
>300°C. (Yield: 66 %).
1H NMR (300 MHz, Acetone-d6, ppm): 11.41 (s, 1H); 8.55 (d, 2H, J= 2.2 Hz);
8.49 (d, 2H, J= 8.8 Hz); 8.15 (dd, 2H, J= 8.8 and 2.2 Hz).
'3C NMR (75 MHz, Acetone-d6, ppm): 141.07; 126.38; 122.09; 114.76.
HRMS: Calculated for C12H~N3O4: 257.0436 Found: 257.0431 2,7-diaminocarbazole (4). To a solution of compound 3 (6.00g, 23.3 mmol) in a mixture of acetic acid (200 mL) and hydrochloric acid (35 mL) was added 44.3 g (0.24 mol, Aldrich Co.) of tin(II) chloride. The mixture was refluxed for 24 h under argon. After cooling, the precipitate was separated from the solvent by filtration and washed several times with cold acetic acid. The resulting diammonium salt was dissolved in water followed by addition of an aqueous solution of sodium hydroxide until the pH was around 10. The precipitate was collect by filtration and dried under vacuum. Recristallization in ethanol afforded 3.60 g of the title product as a shiny gray solid. M.P. 248°C (dec.). (Yield: 78 %).
1H NMR (300 MHz, Acetone-d6, ppm): 9.45(s, 1H); 7.53(d, 2H, J= 8.1 Hz) ; 6.62 (d, 2H, J= 1.5 Hz); 6.47 (dd, 2H, J= 17.0 and 2.2 Hz); 4.45 (s, 4H).
isC NMR (75 MHz, Acetone-d6, ppm) : 146.53; 142.53; 119.72; 116.58; 108.70;
96.42.

HRMS: Calculated for Cl2HnN3: 197.0953 Found: 197.0948 2,7-diiodocarbazole (5). To a solution of 1.50 g (7.56 mmol) of compound 4 in 100 mL of 3 M HCl solution at 0°C was added very slowly 1.10 g S (15.9 mmol) of sodium nitrite in 5 mL of water. The mixture was stirred at 0°C for 2 h and then added to 100 mL of a solution of potassium iodide in distillated water. The stirring was kept for 24 h at room temperature. The precipitate was collect by filtration and washed with aqueous solution of NaHC03. The solid was dried under vacuum for 24 h and use directly in the next reaction without further purification.
However, the crude material could have been purified by column chromatography (silica gel, 10 % ethyl acetate in hexanes as eluent) but the reaction yield would be greatly affected, probably due to the degradation of the product on silica gel.
1H NMR (300 MHz, Acetone-d6, ppm): 10.54(s, 1H); 7.93 (m, 4H) ; 7.53 (dd, 2H, J=

7.4 and 1.5 Hz).
1 S 13C NMR (75 MHz, Acetone-d6, ppm) : 141.77; 128.88; 122.69; 120.79;
120.74;
90.89.
HRMS: Calculated for C~2H~IzN: 418.8668 Found: 418.8675 N octyl-2,7-diiodocarbazole (6). To a solution of compound 5 (3.00 g) in 30 mL of anhydrous DMF was added 660.mg (4.78 mmol, Aldrich Co.) of anhydrous K2C03. The solution was stirred at 80°C for 2 h under argon after 0.93 g (4.82 mmol) of bromooctane was added. The mixture was stirred at 80°C
for 24 h and then quenched with 30 mL of water. The aqueous layer was extracted three times with 50 mL of diethyl ether. The organic layer was dried over magnesium sulfate and the solvent was removed under vacuum. The residue was purified by column chromatography (silica gel, hexanes as eluent) followed by recristallization in methanol to give 1.55 g of the title product as a white solid. M.P. 82-84°C. (Global yield for the last two steps: 38 %).
1H NMR (300 MHz, CDCl3, ppm): 7.78 (d, 2H, J = 8.1 Hz); 7.73 (s, 1H); 7.52 (dd, 2H, J= 8.8 and 1.5 Hz); 4.17 (t, 2H, J= 7.4 Hz); 1.82 (m, 2H); 1.30 (m, 10 H);
0.88 (t, 3H, J= 5.9 Hz).

i3C NMR (75 MHz, CDCl3, ppm) : 141.25; 128.20; 121.84; 121.81; 117.96; 90.80;
43.25; 31.81; 29.28; 29.17; 28.80; 27.15; 22.64; 14.11.
HRMS: Calculated for C2oH23IZN: 530.9920 Found: 530.9906 1-chloro-4-(4'-chlorobenzene)-2-nitrobenzene (7): In a 100 mL flask, 4-chlorophenylboronic acid (2.00g, 12.8 mmol, Aldrich Co.), 1-bromo-4-chloro-2-nitrobenzene (2.72 g, 11.5 mmol, Aldrich Co.), 18 mL of benzene and 12 mL of aqueous KZC03 2M were mixed. The resulting solution was degassed with a vigorous flow of argon. Tetrakis(triphenylphosphine)Pd(0) (0.5-1.0 mol %) was then added under argon and the mixture was refluxed for 2h. The mixture was filtered through a Buchner funnel and the filtrate was extracted three times with diethyl ether.
The combine organic layer was washed with brine and dried over magnesium sulfate.
The solvent was removed and the residue was purified by column chromatography (silica gel, hexanes as eluent) to provide 2.87 g of the title product as a yellow solid. M.P.
88-89 °C (Yield: 93%).
1H NMR (300 MHz, Acetone-d6, ppm): 8.06 (d, 1H, J= 2.2 Hz); 7.82 (dd, 1H, J=
5.9 and 2.2 Hz); 7.61 (d, 1H, J= 8.8 Hz); 7.52 (dd, 2H, J= 8.8 and 2.2 Hz); 7.40 (dd, 2H, J= 8.1 and 2.2 Hz).
i3C NMR (75 MHz, Acetone-d6, ppm) : 136.08; 134.97; 134.67; 134.15; 133.43;
130.43 (2C); 129.61; 124.88 (2C).
2,7-dichlorocarbazole (8): A 25 mL flask was charged with 2.00 g of compound 2 and 10 mL of triethylphosphite. The resulting mixture was refluxed under argon for 5 h. The excess of triethylphosphite was distillated under vacuum (30°C, 0.25 mm Hg) and the crude product was purified by column chromatography (silica gel, 10 % ethyl acetate in hexanes) to provides 1.05 g of the title product as a white solid. M.P. 188-189°C (Yield: 60 %).
1H NMR (300 MHz, CDC13, ppm): 8.02 (s, 2H); 7.91 (d, 2H, J= 8.1 Hz); 7.38 (d, 2H, J= 1.5 Hz); 7.22 (dd, 2H, J= 8.8 and 1.5 Hz).
13C NMR (75 MHz, CDC13, ppm): 140.18; 131.86; 121.43; 121.10; 120.62; 110.87.

N ((2-ethylhexyl)-2,7-dichlorocarbazole) (9): To a solution of 900 mg compound 8 (3.81 mmol) in 20 mL of anhydrous DMF was added 1.06 g (7.67 mmol, Aldrich Co.) of anhydrous KZCO3. The solution was stirred at 80°C for 2 h under argon after 1.47 g (7.61 mmol) of 2-ethylhexylbromide was added. The mixture was stirred at 80°C for 24 h and then quenched with 30 mL of water. The aqueous layer was extracted three times with 50 mL of diethyl ether. The organic layer was dried over magnesium sulfate and the solvent was removed under vacuum. The residue was purified by column chromatography (silica gel, hexanes as eluent) to give 1.15 g of the title product as a colorless oil (Yield = 86 %).
1H NMR (300 MHz, CDC13, ppm): 7.90 (d, 2H, J= 8.1 Hz); 7.32 (d, 2H, J= 1.5 Hz);
7.19 (dd, 2H, J= 8.8 and 2.2 Hz); 4.01 (m, 2H); 2.01 (m, 1H); 1.33 (m, 8H);
0.90 (m, 6H).
i3C NMR (75 MHz, CDC13, ppm): 141.74; 131.71; 121.01; 120.89; 119.81; 109.29;
47.64; 39.16; 30.87; 28.64; 24.40; 23.06; 14.03; 10.92.
N octadecane-2,7-dichlorocarbazole (10): To a solution of 3.00 g of compound 8 (12.7 mmol) in SO mL of anhydrous acetone was added 3.51 g (25.4 mmol, Aldrich Co.) of KzC03 and 8.47 g (25.4 mmol, Aldrich Co.) of 1-bromooctadecane. The solution was refluxed 24 h under argon. The mixture was poured into 100 mL of distillated water and the aqueous layer was extracted with three portions of diethyl ether. The combined organic fractions were washed with brine and dried over magnesium sulfate. The solvent was removed under vacuum.
Recristallization from methanol followed by a recristallization in hexanes afforded 4.77 g of the title product as a white solid. M. P. 72-74 °C (Yield =
86 %).
1H NMR (300 MHz, CDC13, ppm): 7.90 (d, 2H, J= 8.1 Hz); 7.33 (d, 2H, J= 1.5 Hz);
7.19 (dd, 2H, J = 8.8 and 2.2 Hz); 4.05 (t, 2H, J = 7.3 Hz); 1.82 (m, 2H);
1.32 (m, 30H); 0.90 (t, 3H, J= 5.9 Hz).
13C NMR (75 MHz, CDCl3, ppm): 141.29; 131.75; 121.09; 120.94; 119.83; 109.03;
43.34; 31.97; 29.74 (7C); 29.64; 29.59; 29.51; 29.40; 29.35; 28.76; 27.20;
22.73;
14.15.

1-methoxy-4-(4'-methoxybenzene)-2-nitrobenzene (11): In a 100 mL
flask, 4-methoxyphenylboronic acid (4.00g, 26.3 mmol, Aldrich Co.), 4-bromo-3-nitroanisole (5.50g, 25.0 mmol, Aldrich Co.), 30 mL of benzene and 20 mL of 2M in water were mixed. The resulting solution was degassed with a vigorous flow of argon. Pd(PPh3)4 (0.5-1.0 mol %) was then added under argon and the mixture was refluxed for 2 h. The mixture was filtered through a Buchner funnel and the filtrate was extracted with three portions of diethyl ether. The combined organic fractions were washed with brine and dried over magnesium sulfate. The solvent was removed under reduced pressure and the residue was purified by column chromatography (silica gel, 10 % ethyl acetate in hexanes as eluent) to provide 5.50 g of the title product as a yellow solid. M.P. 123-125 °C (Yield: 90 %).
1H NMR (300 MHz, CDCl3, ppm): 7.32 (m, 2H); 7.21 (d, 2H, J = 8.8 Hz); 7.13 (dd, 1H, J= 5.9 and 2.2 Hz); 6.94 (d, 2H, J= 8.8 Hz); 3.88 (s, 3H); 3.83 (s, 3H).
i3C NMR (75 MHz, CDCl3, ppm): 159.41; 158.84; 149.74; 132.80; 129.47; 129.22;
128.22; 118.60; 114.15; 108.96; 55.92; 55.30.
HRMS: Calculated for C14Hi3NOa: 259.0844 Found: 259.0851 2,7-dimethoxycarbazole (12): A 25 mL flask was charged with 5.30 g (20.4 mmol) of compound 11 and 15 mL of triethylphosphite. The resulting mixture was refluxed under argon for 5 h. After cooling at room temperature, the precipitate was filtrated, washed with a large amount of cold methanol and dried under reduced pressure to provides 3.25 g of the title product as a white solid. M.P. 273-274°C
(Yield: 70 %).
1H NMR (300 MHz, DMSO-db, ppm): 10.99 (s, 1H); 7.85 (d, 2H, J= 8.5 Hz); 6.95 (d, 2H, J= 1.8 Hz); 6.74 (dd, 2H, J= 6.3 and 2.0 Hz).
i3C NMR (75 MHz, DMSO-db, ppm): 157.60; 141.08; 119.95; 116.53; 107.34; 94.73;
55.26.
N-octyl-2,7-dimethoxycarbazole (13): A 50 mL flask was charged with 3.00 g (13.2 mmol) of compound 12, 5.10 g (26.4 mmol, Aldrich Co.) of 1-bromooctane, 1.06 g (26.4 mmol) of sodium hydroxide reagent grade, 134 mg (0.39 mmol) of tetrabutylamonium hydrogensulfate (TBAH) and 25 mL of anhydrous acetone. The resulting mixture was refluxed under argon for 24 h and then poured into 100 mL of distillated water. The aqueous layer was extracted three times with diethyl ether. The combined organic fractions was dried over magnesium sulfate and the solvent was removed under reduced pressure. The residue was purified by column chromatography (silica gel, 5 % ethyl acetate in hexanes as eluent) to provide 4.06 g of the title product as white fluffy solid. M.P. 63-64°C (Yield: 91 %).
1H NMR (300 MHz, CDC13, ppm): 7.88 (dd, 2H, J = 5.9 and 1.5 Hz); 6.84 (m, 4H);
4.17 (t, 2H, J = 7.4 Hz); 3.95 (s, 6H); 1.86 (m, 2H); 1.35 (m, l OH); 0.92 (t, 3H, J =
4.4 Hz).
~3C NMR (75 MHz, CDCl3, ppm): 158.22; 141.98; 120.13; 117.12; 106.65; 93.65;
55.77; 43.07; 31.87; 29.44; 29.23; 28.70; 27.33; 22.67; 14.12.
HRMS: Calculated for CZZH29N02: 339.2198 Found: 339.2193 N-octyl-2,7-hydroxycarbazole (14): A 250 mL flame dried flask was charged with 3.30 g (9.72 mmol) of compound 13 and 100 mL of anhydrous methylene chloride. The solution was cooled at -78°C and 24.3 mL (48.6 mmol) of boron tribromide (1M in methylene chloride, Aldrich Co.) was added over 0.5 h.
The resulting mixture was stirred under argon at -78°C for 3 h and at room temperature for 12 h. The mixture was quenched slowly with 50 mL of HCl 10 % (v/v) to destroy the excess of boron tribromide and extracted with 3 portions of 50 mL methylene chloride. The combined organic fractions was dried over magnesium sulfate and the solvent was removed under reduced pressure. Recristallization from toluene/hexanes afforded 1.86 g of the title product as a slightly gray solid. M.P. 144-145°C (Yield: 68 %).
1H NMR (300 MHz, Acetone-d6, ppm): 8.22 (s, 2H); 7.76 (d, 2H, J= 8.8 Hz); 6.88 (d, 2H, J = 2.2 Hz) ; 6.70 (dd, 2H J = 6.6 and 2.2 Hz); 4.19 (t, 2H, J = 7.4 Hz);
1.82 (m, 2H); 1.31 (m, 10 H); 0.86 (t, 3H, J= 6.6 Hz).
i3C NMR (75 MHz, Acetone-d6, ppm): 156.30; 142.88; 120.37; 117.15; 108.49;
95.78; 43.24; 32.39; 29.85; 29.20; 28.95; 27.24; 23.14; 14.21.
HRMS: Calculated for CZOH25N02: 311.1885 Found: 311.1891 N-octyl-2,7-bis(trifluoromethanesulfonyl)carbazole (15): A 25 mL
flask was charged with 2.00 g (6.46 mmol) of compound 14, 790 mg (6.46 mmol, Aldrich Co.) of dimethylaminopyridine (DMAP) and 16 mL of anhydrous pyridine.
The mixture was cooled at 0°C and 5.47 g (19.4 mmol, Aldrich Co.) of trifluoromethanesulfonic anhydride was added dropwise. After 10 min., 4 mL of pyridine was added to dissolve the white precipitate formed during the addition of anhydride. The mixture was stirred at 0°C for 1 h and at room temperature for 24 h.
The excess of anhydride was destroy with slow addition of 25 mL of distillated water.
The mixture was extracted three times with 25 mL of diethyl ether. The combined organic fractions were washed successively with five 50 mL portions of distillated water, five 50 mL portions of aqueous CuS04 O.1M, three 50 mL portions of brine and again with SO mL portion of distillated water. The mixture was dried over magnesium sulfate and the solvent was removed under reduced pressure. The crude product was purified by column chromatography (silica gel, 5 % ethyl acetate in hexanes as eluent) to provide 2.83 g of the title product as a red oil.
(Yield: 76 %).
1H NMR (300 MHz, CDC13, ppm): 8.00 (d, 2H, J= 8.8 Hz); 7.31 (d, 2H, J= 2.2 Hz);
7.17 (dd, 2H, J = 5.9 and 2.2 Hz); 4.17 (t, 2H, J = 7.4 Hz); 1.83 (m, 2H);
1.30 (m, l OH); 0.89 (t, 3H, J= 6.6 Hz).
i3C NMR (75 MHz, CDC13, ppm): 148.23; 141.31; 125.34; 121.73; 121.63; 121.09;
116.83; 112.84; 112.58; 102.53; 43.60; 31.68; 29.22; 29.04; 28.68; 27.15;
22.57;
13.90.
HRMS: Calculated for CZZH23F6NO6S2: 575.0871 Found: 575.0877 N-octyl-2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)carbazole (16): A flame dried 25 mL flask was charged successively with 1.50 g (2.60 mmol) of compound 15, 11 mL of 1,2-dichloroethane, 38 mg (0.05 mmol) of PdCl2(dppfJ, 2.2 mL of triethylamine and 1.14 mL (7.86 mmol) of 4,4,5,5-tetramethyl-1,3,2-dioxaborolane. The mixture was stirred under argon for 4 h at 80°C
and then poured in 50 mL of distillated water. The aqueous layer was extracted with three portions of CHC13. The combined organic layers were dried over magnesium sulfate and the solvent was removed under reduced pressure. The crude dark red oil was puriifed by column chromatography (NEt3 pretreated silica gel, 5 % ethyl acetate in hexanes) to provide 837 mg of the title product as a white solid. M.P. 168-169°C
(Yield: 59 %).
1H NMR (300 MHz, CDC13, ppm): 8.13 (d, 2H, J= 7.4 Hz); 7.89 (s, 2H); 7.69 (d, 2H, J = 7.4 Hz); 4.39 (t, 2H, J = 7.4 Hz); 1.90 (m, 2H); 1.41 (m, 12 H); 1.30 (m, l OH);
0.88 (t, 3H, J= 6.6 Hz).
isC NMR (75 MHz, CDC13, ppm): 140.47; 125.09; 124.86; 120.01; 115.28; 83.80;
42.91; 31.84; 29.37; 29.20; 29.17; 27.12; 24.95; 22.64; 14.11. (The missing peak is due to the carbon linked to the boronic function which shows no signal in'3C
NMR).
HRMS: Calculated for C32H4~BZNOq: 531.3691 Found: 531.3700 EXAMPLE 4: Preparation of poly (N-octyl-2,7-carbazole) In a 10 mL flask, 1.00 g (1.88 mmol) of compound 6, 296 mg (1.13 mmol) of triphenylphosphine, 405 mg (6.20 mmol) of zinc powder 99.998% 100 mesh, 15.0 mg (0.09 mmol) of 2,2'-bipyridine 12.0 mg (0.09 mmol) of anhydrous nickel (II) chloride and 3 mL of anhydrous DMAc were stirred under argon for 3 days at 100°C. The whole mixture was then poured into a cold mixture of methanol/HCl (5:1 v/v). The precipitated material was recovered by filtration through a Buchner funnel and washed with dilute HCI. The solid material was washed for 24 h in a Soxhlet apparatus using acetone to remove oligomers and catalyst residues. The resulting solid was dilute again in chloroform and filtrated on 0.2 pm filtering paper to remove all traces of nickel. The resulting solid was dried under reduced pressure for 24 h. (Yield: 78 %).
EXAMPLE 5: Preparation of poly (N-octadecane-2,7-carbazole) In a 25 mL flask, 384 mg (2.46 mmol, Aldrich Co.) of 2,2'-bipyridine, 676 mg (2.46 mmol, Aldrich Co.) of Ni(COD)2 and 0.25 mL (2.05 mmol, Aldrich Co.) of 1,5-cyclooctadiene (COD) 7 mL of degassed anhydrous DMF were stirred under argon for 1h at 80°C. 1.00 g (2.05 mmol) of compound 10 in 7 mL
of degassed anhydrous DMF was added and the mixture was stirred for 48 h under argon at 100°C. The whole mixture was then poured into a cold of methanol. The precipitated material was recovered by filtration through a Buchner funnel. The solid material was washed for 24 h in a Soxhlet apparatus using acetone to remove oligomers and catalyst residues. The resulting solid was dilute again in chloroform and filtrated on 0.2 ~m filtering paper to remove all traces of nickel. The resulting solid was dried under reduced pressure for 24 h. (Yield: 75 %).
EXAMPLE 6: Preparation of poly (N-octyl-2,7-carbazole-alt-9,9-dioctyl-2,7-fluorene) In a 10 mL flask, 225 mg (0.42 mmol) of compound 6, 271 mg (0.42 mmol) of 2,7-Bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2y1)-9,9-dioctylfluorene and mg of (PPh3)4Pd(0) were dissolved in a degassed mixture of THF (2.5 mL) and 10 aqueous 2 M KZC03. The solution was refluxed under argon for 3 days. The whole mixture was then poured into cold methanol (100 mL). The precipitated material was recovered by filtration through a Buchner funnel and washed with dilute HCI.
The solid material was washed for 24 h in a Soxhlet apparatus using acetone to remove oligomers and catalyst residues. The resulting polymers were soluble in THF
and 1 S CHC13. (Yield: 78 %).
EXAMPLE 7: Preparation of poly [N-2-ethylhexyl-2,7-carbazole-alt-S,5'-(2,2'-bithiophene)]
In a 50 mL flask, 541 mg (1.10 mmol) of 5,5'-bis(trimethylstannyl)-2,2'-bithiophene, 531 mg (1.00 mmol) of N 2-ethylhexyl-2,7-diiodocarbazole and p.g of C12(PPh3)ZPd(0) were dissolved in 30 mL of degassed THF. The solution was refluxed under argon for 3 days. The whole mixture was then poured into cold methanol (300 mL). The precipitated material was recovered by filtration through a Buchner funnel and washed with dilute HCI. The solid material was washed for 24 h in a Soxhlet apparatus using acetone to remove oligomers and catalyst residues. The resulting polymers were soluble in THF and CHC13. (Yield: 52 %).
EXAMPLE 8: Preparation of poly (N-octyl-2,7-carbazole-alt-2,5-thiophene) (PTC) In a 25 mL flask was added 350 mg (0.66 mmol) of compound (3), 276 mg (0.67 mmol) of compound (8), 9 mg (13 ~mol, Aldrich Co.) of PdCl2(PPh3)2 and 8 mL of anhydrous THF. The mixture was refluxed under argon for 72 h. The yellow suspension was poured in cold methanol. The precipitate was collected by flitration and washed with acetone in a Soxhlet apparatus for 48 h. After being dried under reduced pressure, an orange solid was obtained. (Yield: 68 %).
EXAMPLE 9: Preparation of poly (N-octyl-2,7-carbazole-alt-2,5-S dioxyethylenethiophene) (PEDOTC) In a 10 mL flask was added 190 mg (0.36 mmol) of compound (14), 107 mg (0.36 mmol) of compound (7), 8 mg (7 pmol) of Pd(PPh3)4, 3 mL of anhydrous THF and 2 mL of KZC03 2M in water. The mixture was refluxed under argon for 72 h. The black suspension was poured in cold methanol. The precipitate was collected by filtration and washed with acetone in a Soxhlet apparatus for 48 h.
After being dried under reduced pressure, a black solid was obtained. (Yield:
68 %).
EXAMPLE 10: Preparation of poly (N-(2-ethylhexyl)-2,7-carbazole-alt-4-butyl-N,N
Bis(p-phenyl)phenylamine) (PPAC) In a 10 mL flask, 501 mg (0.87 mmol) of N (2-ethylhexyl)-2,7-bis(trifluoromethanesulfonyl)carbazole, 474 mg (0.87 mmol) of 4-butyl-N,N
Bis(p-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)phenylamine) and 10 mg of (PPh3)4Pd(0) were dissolved in a degassed mixture of THF (3 mL) and aqueous 2 M
KZC03 (2 mL). The solution was refluxed under argon for 3 days. The whole mixture was then poured into cold methanol (100 mL). The precipitated material was recovered by filtration through a Biichner funnel and washed with dilute HCI.
The solid material was washed for 24 h in a Soxhlet apparatus using acetone to remove oligomers and catalyst residues. The resulting polymers were soluble in THF
and CHCI3. (Yield: 75 %).
EXAMPLE 11: Preparation of poly (N-octyl-2,7-carbazole) In a 10 mL flask, 500 mg (0.87 mmol) of compound 15, 137 mg (0.52 mmol) of triphenylphosphine, 188 mg (2.88 mmol) of zinc powder 99.998% 100 mesh, 7.0 mg (0.09 mmol) of 2,2'-bipyridine 12.0 mg (0.04 mmol) of anhydrous nickel (II) chloride and 3 mL of anhydrous DMF were stirred under argon for 3 days at 100°C. The whole mixture was then poured into a cold mixture of methanol/HCI
(S:1 v/v). The precipitated material was recovered by filtration through a Buchner funnel and washed with dilute HCI. The solid material was washed for 24 h in a Soxhlet apparatus using acetone to remove oligomers and catalyst residues. The resulting solid was dilute again in chloroform and filtrated on 0.2 ~m filtering paper to remove all traces of nickel. The resulting solid was dried under reduced pressure for 24 h. (Yield: 83 %).
EXAMPLE 12: Preparation of poly (N-octyl-2,7-carbazole) In a 10 mL flask, 540 mg (0.94 mmol) of compound 15, 500 mg (0.94 mmol) of compound 16 and 10 mg of (PPh3)4Pd(0) were dissolved in a degassed mixture of THF (6.6 mL) and aqueous 2 M K2C03 (2.8 mL). The solution was refluxed under argon for 3 days. The whole mixture was then poured into cold methanol ( 100 mL). The precipitated material was recovered by filtration through a Buchner funnel and washed with dilute HCI. The solid material was washed for 24 h in a Soxhlet apparatus using acetone to remove oligomers and catalyst residues. The resulting polymers were partially soluble in THF and CHC13. (Yield: 86 %).
The resulting conjugated homopolymers and copolymers are soluble in common organic solvents, such as chloroform and tetrahydrofuran. The number-average molecular weight (measured by size exclusion chromatography against monodisperse polystyrene standards) of these polymers is about 10 kDa with a polydispersity of 2. They can be processed by spin coating or by simple casting to yield thin polymer films with good mechanical properties. As reported in Figure 1, the solution and solid-state optical properties of poly(N-octyl-2,7-carbazole) have been investigated in more details. In dilute solutions or as thin films, this polymer exhibits an absorption maximum around 380-390 nm, indicating a pale-yellow color in both forms. This absorption maximum is significantly red-shifted compared to that previously reported for poly(N-alkyl-3,6-carbazole)s (i.e. 300-320 nm) and can be related to a more conjugated structure. Moreover, poly(N-octyl-2,7-carbazole) exhibits an intense blue emission upon radiative excitation, with a quantum yield of about 80% in chloroform, at room temperature. In solution, poly(N-octyl-2,7-carbazole) shows a maximum of emission at 417 nm followed by two vibronic side-bands at 439 and 474 nm whereas in the solid state, the polymer is slightly more conjugated with an emission maxium at 437 nm followed by two other maxima at 453 and 492 nm. These solid-state and solution emission spectra are slightly red-shifted compared to poly(9,9-dioctyl-2,7-fluorene) and could be related to the electron-donating effect of the nitrogen atom in the inner ring. Moreover, poly(N-octyl-2,7-carbazole) shows a relatively low oxidation potential at 0.75 V vs Ag/AgCI (Figure 2). This oxidation potential is lower than those reported for poly(N-alkyl-3,6-carbazole)s at 0.85 and 1.2 V vs Ag/AgCI and is an indirect proof of the more delocalized structure in 2,7-linked polycarbazoles.
This combination of electrical and optical properties is particularly interesting 1 o for the development of a novel class of blue-light emitting materials.
Moreover, with the possibilities of structural modifications through the synthesis of various alternating copolymers, it is possible to develop tunable light-emitting materials.

Claims (11)

1. A conjugated poly(N-alkyl-2,7-carbazole) of formula (I):

wherein R represents a linear or branched alkyl group having 1 to 22 carbon atoms and n is an integer of about 3 to about 100, with the proviso that when R
is a decyl radical, n cannot represent an integer from 2 to 6.

2. Poly(N-octyl-2,7-carbazole).

3. Poly(N-octadecane-2,7)carbazole.

4. A conjugated polymer comprising alternating units of formula (I'):

wherein R represents a linear or branched alkyl group having 1 to 22 carbon atoms.

5. Poly(N-octyl-2,7-carbazole-alt-9,9-dioctyl-2,7-fluorene).

6. Poly[N-2-ethylhexyl-2,7-carbazole-alt-5,5'-bithiophene)].

7. Poly(N-octyl-2,7-carbazole-alt-2,5-thiophene).

8. Poly(N-octyl-2,7-carbazole-alt-2,5-dioxyethylenethiophene).

9. Poly(N-(2-ethylhexyl)-2,7-carbazole-alt-4-butyl-N,N bis(p-phenyl)phenylamine).

10. A process for preparing a conjugated poly(N-alkyl-2,7-carbazole) of formula (I):

wherein R represents a linear or branched alkyl group having 1 to 22 carbon atoms and n is an integer of about 3 to about 100, which comprises treating a N-alkyl-2,7-difunctionnalized carbazole of formula (II):

wherein R is as defined above and X represents a trifluoromethanesulfonyl group or a halogen atom selected from the group consisting of bromine, chlorine and iodine atoms, with triphenylphosphine and 2,2'-bipyridine in the presence of zinc and nickel chloride, to cause polymerization of the compound of formula (II).

11. A process according to claim 10, wherein in compounds of formula (I) and (II) R is an octyl group, and in compound of formula (II) X is an iodine atom or a trifluoromethanesulfonyl group.