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RSC Advances
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DOI: 10.1039/C5RA20562J
RSC Advances
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palladium [Pd(PPh3)4] (1.5 mol %) was added in one portion under
o
nitrogen atmosphere. The solution was then stirred at 90 C under
Br
Br
Suzuki
coupling
Br
OH
nitrogen atmosphere. After stirring for 24 hr, the end groups,
bromobenzene and phenylbornoic acid, were then capped by
refluxing subsequently for 6 h each. After cooling, the solution was
poured into a large amount of methanol solution, and then the crude
polymers were collected by filtration and further purified by
extraction with acetone for 24 h in a Soxhlet apparatus to remove
monomers and catalyst residues.
O
O
N
+
B
B
O
O
n
Pd(PPh3)4
B
N
OH
A
2
PFA
Heck
coupling
Pd(OAc)2
n
N
Synthesis
of
poly[2,7-(9,9-dihexylfluorene)-alt-4’’-(4-
Br
vinylphenyl)-4,4’-triphenylamine] (PFA). The composition of the
reactants were 9,9ꢀdihexylfluoreneꢀ2,7ꢀdiboronic acid bis(1,3ꢀ
propanediol) ester (A) (0.502 g, 1.0 mmol), 2 (0.505 g, 1.0 mmol),
toluene (6.5 ml), Pd(PPh3)4 (0.0346 g, 0.03 mmol), 2 M aqueous
K2CO3 solution (6 ml) and aliquat 336 (20.0 mg); endꢀcapping by
bromobenzene (50.0 mg, 0.32 mmol), and phenylboronic acid (50.0
mg, 0.41 mmol). Yield: 81.2%. Tg = 169.1 oC. 1H NMR (CDCl3, δ in
ppm): 0.66ꢀ1.32 (m, CH2 and CH3), 1.96ꢀ2.10 (br, CH2), 5.21ꢀ5.27
(br, CH=C), 5.68ꢀ5.77 (br, CH=C), 6.65ꢀ6.79 (br, CH=C), 7.24ꢀ7.81
(m, ArꢀH and vinyl). Anal. Calcd. (%) from feed (C25H32)(C26H19N):
C, 90.40; H, 7.53; N, 2.07. Found: C, 88.67; H, 6.88; N, 2.21.
N
N
N
3
N
N
N
PFAD
Scheme 2 Synthetic routes of conjugated polymers (PFA and PFAD).
toluene (10 ml) was dissolved in 2 M aqueous potassium carbonate
(K2CO3) solution (6 ml) and ethanol (6 ml). The solution was then
stirred at 80 C under nitrogen atmosphere. After stirring for 48 hr,
o
Synthesis of poly[2,7-(9,9-dihexylfluorene)-alt-4’’-(4-di(2-
picolyl)amino-styrylphenyl)-4,4’-triphenylamine] (PFAD). The
synthesis of PFAD was carried out using a palladiumꢀcatalyzed
Heck coupling reaction, using palladium acetate (Pd(OAc)2) as the
catalyst. To a solution of PFA (100.0 mg), 3 (3.68 g, 10.0 mmol),
Pd(OAc)2 (0.045 g, 0.2 mmol) and triꢀpꢀtolylphosphine (0.304 g, 1
mmol) was added with a solution of triethylamine (1.518 g, 15.0
mmol) dissolved in 20 ml DMF. The solution was then stirred at 100
oC under nitrogen atmosphere. After stirring for 48 hr, the solution
was poured into a large amount of methanol solution, and then the
crude polymers were collected by filtration and further purified by
extraction with acetone for 24 h in a Soxhlet apparatus to remove
the solution was poured into an excess of methanol solution, and
then the crude product was collected by filtration and further purified
by column chromatography using nꢀhexane as eluent to give 2.
Yield: 32.0%. 1HꢀNMR (CDCl3, δ in ppm): 5.27ꢀ5.29 (dd, 1H,
CH=C), 5.80ꢀ5.82 (dd, 1H, CH=C), 6.74ꢀ6.81 (dd, 1H, CH=C),
6.94ꢀ6.97 (d, 4H, aromatic, ArꢀH), 7.08ꢀ7.11 (d, 2H, aromatic, Arꢀ
H), 7.36ꢀ7.39 (d, 4H, aromatic, ArꢀH), 7.45ꢀ7.55 (d, 6H, aromatic,
ArꢀH). Anal. Calcd. (%) for C26H19Br2N: C, 61.81; H, 3.76; N, 2.77.
Found: C 62.02; H, 3.70; N, 2.86.
Synthesis of 4-bromobenzyl-di(2-picolyl)amine (3). A mixture
of di(2ꢀpicolyl)amine (0.996 g, 5.0 mmol), potassium carbonate
(K2CO3) (1.04 g, 7.5 mmol), potassium iodide (1.0 mg, 0.006 mmol)
and N,Nꢀdimethylformamide (DMF, 30 ml) was heated at 100 oC for
0.5 h, and then 4ꢀbromobenzyl bromide (1.5 g, 6.0 mmol) was added
dropwise into the above system with stirring for 24 h. After cooling
to room temperature, the mixture was poured into a stirred of ice
water and then extracted with dichloromethane. The organic layer
was successively washed with water twice, dried over anhydrous
magnesium sulfate and concentrated under reduced pressure. Yield:
o
1
compound 3 and catalyst residues. Yield: 25.4%. Tg = 138.3 C. H
NMR (CDCl3, δ in ppm): 0.62ꢀ0.85 (br, CH2), 0.94ꢀ1.15 (m, CH3),
1.35ꢀ1.49 (m, CH2), 1.90ꢀ2.08 (br, CH2), 3.45ꢀ3.50 (br, NCH2), 3.69ꢀ
3.78 (br, NCH2), 7.12ꢀ7.80 (m, ArꢀH and vinyl). Anal. Calcd. (%)
from feed (C25H32)(C45H36N4): C, 87.14; H, 6.33; N, 5.81. Found: C,
86.52; H, 6.57; N, 5.45.
Fluorescent titration of polymer
1
Fluorescent titration experiments were carried out in THF solution.
The chloride salts of Ca2+, Mg2+, Mn2+, Zn2+, Ni2+, Fe3+, K+, Cu2+,
Fe2+, Ag+, Al3+, Ba2+, Pb2+, Hg2+, Cr3+, and Co3+ (5.0 × 10ꢀ3 M) were
dissolved in distilled water. Titration was done by adding the metal
ion solution to a test tube with polymer solution. The final
concentration of polymer was 1.1 × 10ꢀ3 wt%. Titration of the metal
ions was terminated until no change in the fluorescence intensity was
observed. The percentage of water in THF was approximately 1.0 %.
The SternꢀVolmer constant (Ksv) was estimated according to
following equation:
62.1%. HꢀNMR (acetoneꢀd6, δ in ppm): 3.67 (s, 2H, CH2), 3.77 (s,
4H, CH2), 7.20 (t, 2H, aromatic, ArꢀH), 7.42 (d, 2H, aromatic, Arꢀ
H), 7.48 (d, 2H, aromatic, ArꢀH), 7.60 (d, 2H, aromatic, ArꢀH), 7.73
(t, 2H, aromatic, ArꢀH), 8.48 (d, 2H, aromatic, ArꢀH). Anal. Calcd.
(%) for C19H18BrN3: C, 61.97; H, 4.89; N, 1.14. Found: C, 61.54; H,
4.86; N, 1.18.
Synthesis of conjugated polymers
The synthesis of a TPAꢀsubstituted polyfluorene (PFA) was
carried out using a palladiumꢀcatalyzed Suzuki coupling reaction.
The general synthetic procedures for the PF derivative are described
as follows: To a solution of predetermined amount monomers in
toluene was added with aqueous potassium carbonate (2M) and
ethanol. The mixture was degassed and exchanged with nitrogen for
three times, and a catalytic amount of tetrakis(triphenylphosphine)
(Io/I) = 1 + Ksv[Q]
(1)
where Io and I are the intensity of PL spectrum without and with a
quencher, respectively, Ksv is the SternꢀVolmer constant (quenching
coefficient), and [Q] is the concentration of the quencher ions. The
stabilization of PFADꢀFe3+ complex was investigated in the presence
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