A fluorescence sensor based on chiral polymer for highly enantioselective recognition of phenylalaninol

Article abstract of DOI:10.1016/j.polymer.2010.12.011

The chiral polymer P-1 incorporating (S)-2,2′-binaphthol (BINOL) and (S)-2,2′-binaphthyldiamine (BINAM) moieties in the main chain of the polymer backbone was synthesized by the polymerization of (S)-6,6′- dibutyl-3,3′-diformyl-2,2′-binaphthol (S-M-1) with (S)-2,2′-binaphthyldiamine (S-M-2) via nucleophilic addition-elimination reaction, and the chiral polymer P-2 could be obtained by the reduction reaction of P-1 with NaBH₄. The fluorescence intensity of the chiral polymer P-1 exhibits gradual enhancement upon addition of (d)- or (l)-phenylalaninol and keeps nearly a linear correlation with the concentration molar ratios of (d)- or (l)-phenylalaninol. The value of enantiomeric fluorescence difference ratio (ef) is 6.85 for the chiral polymer on (d)-phenylalaninol. On the contrary, the chiral polymer P-2 shows no obvious fluorescence response toward either (d)- or (l)-phenylalaninol.

Full text of DOI:10.1016/j.polymer.2010.12.011

Polymer 52 (2011) 363e367
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Polymer
journal homepage: www.elsevier.com/locate/polymer
A fluorescence sensor based on chiral polymer for highly enantioselective
recognition of phenylalaninol
,
,
b,
**
Jie Meng a, Guo Wei a, Xiaobo Huang a c, Yu Dong a, Yixiang Cheng a , Chengjian Zhu
*
a Key Lab of Mesoscopic Chemistry of MOE, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, China
b State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, China
c College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325027, China
a r t i c l e i n f o
a b s t r a c t
The chiral polymer P-1 incorporating (S)-2,20-binaphthol (BINOL) and (S)-2,20-binaphthyldiamine
(BINAM) moieties in the main chain of the polymer backbone was synthesized by the polymerization of
(S)-6,60-dibutyl-3,30-diformyl-2,20-binaphthol (S-M-1) with (S)-2,20-binaphthyldiamine (S-M-2) via
nucleophilic additioneelimination reaction, and the chiral polymer P-2 could be obtained by the
reduction reaction of P-1 with NaBH4. The fluorescence intensity of the chiral polymer P-1 exhibits
Article history:
Received 12 October 2010
Received in revised form
2 December 2010
Accepted 7 December 2010
Available online 15 December 2010
gradual enhancement upon addition of (
with the concentration molar ratios of ( )- or (
difference ratio (ef) is 6.85 for the chiral polymer on (
polymer P-2 shows no obvious fluorescence response toward either (
D
)- or (
)-phenylalaninol. The value of enantiomeric fluorescence
)-phenylalaninol. On the contrary, the chiral
)- or ( )-phenylalaninol.
L)-phenylalaninol and keeps nearly a linear correlation
D
L
Keywords:
Chiral polymer
Fluorescence sensor
Molecular recognition
D
D
L
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
and biological fields, there have been some reports on developing
sensors for amino alcohols, especially the enantioselective recog-
nition of chiral amino alcohols [18,19]. Although great progress has
been made for the asymmetric synthesis of chiral amino alcohol
compounds, the search for highly enantioselective as well as
practical catalysts still keeps great interest. Therefore, the design of
fluorescent sensors for the highly enantioselective recognition of
chiral molecules and the rapid determination of their enantiomeric
composition is highly desirable [5,20e24].
Molecular recognition, especially chiral recognition, is one of the
most fundamental and crucial properties of various natural
systems. It is of particular significance for understanding the
interactions of biological molecules and for the designing of
asymmetric catalysis systems [1e5]. More and more attentions
have been paid on fluorescence-based enantioselective sensors due
to their high selectivity and potential application in analytical,
biological, clinical and biochemical environments. They can also
effectively provide a real-time analytical tool for chiral compound
assay [4,6e9]. Using chiral fluorescence-based sensors can not only
greatly facilitate rapid determination of enantiomeric composition
of chiral compounds, but also allow a rapid screening of high-
throughput catalysts for their asymmetric synthesis [10e13]. So far,
reports of successful enantiodiscriminating sensors are mainly
focused on a variety of chiral macrocycles (fluorophore-modified
calixarenes, cyclodextrins, and crown ethers), dendrimers, and
oligomers [4,14e17].
The chirality of 2,20-binaphthol, 2,20-binaphthyldiamine and
their derivatives is derived from the restricted rotation of the two
naphthalene rings. The rigid structure and C2 symmetry of the
chiral binaphthyl molecules can play an important role in inher-
ently chiral induction [25e33]. The skeletal structure of BINOL at
the 3,30-, 5,50- or 6,60-positions of binaphthyl can be selectively
functionalized at well-defined molecular level and lead to a variety
of polybinaphthyls which can exhibit efficient and stable chiral
configuration as well as high chiral induction and chiral discrimi-
nation in fluorescence chemosensor and asymmetric catalysis
[34e41]. Pu’s group reported that the bisbinaphthyl macrocycles
containing chiral diamine were useful for the enantioselective
Chiral amino alcohols are very useful as intermediates for
making a variety of biologically active molecules or as ligands for
stereoselective catalysts. Due to their great application in medical
fluorescence recognition for amino acid derivatives and a-hydrox-
ycarboxylic acids [15,42e44]. Hou and his coworkers also reported
that the enantioselective fluorescent sensors based on multiple
chiral center could exhibit highly enantioselectivity for the recog-
* Corresponding author. Tel.: þ86 25 83685199; fax: þ86 25 83317761.
** Corresponding author.
nition of diverse a-hydroxycarboxylic acids [45,46].
E-mail addresses: yxcheng@nju.edu.cn (Y. Cheng), cjzhu@nju.edu.cn (C. Zhu).
0032-3861/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.polymer.2010.12.011

364
J. Meng et al. / Polymer 52 (2011) 363e367
Many chiral fluorescence host compounds for enantioselective
2.3. Preparation of (S)-6,60-dibutyl-2,20-bis(methoxymethoxy)-1,10-
recognition of chiral guest compounds have been reported, but most
of them are based on chiral small molecules, and fluorescent poly-
mer-based sensors are very few [47e54]. Recently, we have initiated
a project to focus on the chiral polymer used as fluorescence sensors
for enantioselective recognition of chiral molecules [50]. Chiral
polymers used as fluorescence-based sensors for chiral molecule
enantioselective recognition offer several advantages over small
molecule sensors, such as fluorescence efficiency enhancement and
possible cooperative effects of multiple chiral units [55e61].
Moreover, these fluorescent chiral polymers can be systematically
modified bythe introduction of the functional groupsbased on steric
and electronic property and represent a newgeneration of materials
used as chemosensors in chiral molecule recognition.
binaphthyl (2) (Scheme 1) [62]
(S)-6,60-Dibromo-2,20-bis(methoxymethoxy)-1,10-binaphthy (1)
[63] (5.9 g, 11.1 mmol) was dissolved in anhydrous THF (50 mL), n-
BuLi (15.0 mL, 2.5 mol/L in hexanes, 37.5 mmol) was added by
syringe injection at ꢀ78 ꢁC under N2 atmosphere. After the reaction
mixture was stirred for 10 min, n-C4H9Br (5.3 g, 38.7 mmol) was
added to the above solution at ꢀ78 ꢁC under N2 atmosphere. The
reaction mixture was gradually warmed to room temperature and
stirred overnight. The mixture was extracted with ethyl acetate
(2 ꢂ 100 mL). The combined organic layers were washed with
water and brine, and then dried over anhydrous Na2SO4. After
removal of solvent under reduced pressure, the crude product was
purified by column chromatography (petroleum ether/ethyl
acetate) (30:1, v/v) to afford a colorless viscous product (S)-6,60-
In this paper, we report the synthesis of chiral polymers P-1 and
P-2. The chiral (S)-BINOL and (S)-BINAM moieties can orient a well-
defined spatial arrangement in the main chain of the polymer
backbone. This kind fluorescence polymer P-1 can exhibit the most
Dibutyl-2,20-bis(methoxymethoxy)-1,10-binaphthyl (2) in 70.4%
25
yield (3.8 g). [
a]
D
¼ ꢀ38.0 (c 0.5, CH2Cl2). Mp: 150e152 ꢁC. 1H NMR
pronounced chiral discrimination of
D-phenylalaninol. The results
(300 MHz, CDCl3):
d
7.93 (d, 2H, J ¼ 9.0 Hz), 7.71 (s, 2H), 7.6 (d, 2H,
also indicated that P-1 can be used as a fluorescence sensor for
enantiomer composition determination of phenylalaninol.
However, the chiral polymer P-2 obtained by the reduction reaction
of P-1 with NaBH4 shows no obvious fluorescence response toward
phenylalaninol.
J ¼ 9.0 Hz), 7.19 (s, 4H), 5.12 (d, 2H, J ¼ 6.6 Hz), 5.01 (d, 2H,
J ¼ 6.6 Hz), 3.21 (s, 6H), 2.79 (t, 4H, J ¼ 7.2 Hz), 1.75e1.67 (m, 4H),
1.48e1.41 (m, 4H), 0.98 (t, 6H, J ¼ 7.2 Hz). 13C NMR (75 MHz, CDCl3):
d
152.6, 138.5, 132.9, 130.4, 129.0, 128.1, 126.6, 125.9, 121.7, 117.5,
95.3, 55.7, 35.9, 33.8, 22.8, 14.3. FT-IR (KBr, cmꢀ1): 2956, 2929, 2857,
1596, 1500, 1480, 1241, 1151, 1028. MS (EI, m/z): 486 (Mþ, 7%), 410
(100%), 382 (48%), 339 (34%).
2. Experimental part
2.4. Preparation of (S)-6,60-dibutyl-3,30-diformyl-2,20-binaphthol
2.1. Materials
(S-M-1) (Scheme 1) [62]
All solvents and reagents were commercially available and
analytical-reagent-grade. (S)-2,20-binaphthol and (S)-2,20-binaph-
thyldiamine were purchased from Aldrich directly used without
purification. THFand toluene were purified by distillation from sodium
in the presence of benzophenone. CH3CN was distilled from P2O5.
Compound 2 (3.36 g, 6.6 mmol) was dissolved in anhydrous THF
(80 mL), n-BuLi (9.4 mL, 2.5 mol/L in hexanes, 23.5 mmol) was
added by syringe injection at room temperature under a N2
atmosphere. The mixture was first stirred for 2 h, and then cooled
to 0 ꢁC.1.9 mL of DMF (24.8 mmol) was added to the above solution.
The reaction mixture was gradually warmed to room temperature
and continued to stir for 4 h. After 60 mL of HCl (12 mol/L) was
added to the solution, the solution was stirred at room temperature
overnight. After the removal of the solvent under reduced pressure,
the residue was extracted with CH2Cl2 (3 ꢂ 50 mL). The combined
extract was washed with 100 mL of saturated NaHCO3 solution and
brine twice and then dried over anhydrous Na2SO4. After removal
of solvent under reduced pressure, the crude product was purifed
by column chromatography (petroleum ether/ethyl acetate) (10:1,
2.2. Measurements
NMR spectra were obtained using a 300-Bruker spectrometer
300 MHz for 1H NMR and 75 MHz for 13C NMR and reported as parts
per million (ppm) from the internal standard TMS. FT-IR spectra
were taken on a Bruck VERTEX70 FT-IR spectrometer. Fluorescence
spectra were obtained from an RF-5301PC spectrometer. Specific
rotation was determined with a Ruololph Research Analyfical
Autopol III. MS was determined on a Micromass GCT. C, H, N of
elemental analyses were performed on an Elemental Vario MICRO
analyzer. GPC measurements were carried out on a BI-200SM using
polystyrene as a standard and HPLC grade THF as eluent.
v/v) to afford (S)-6,60-dibutyl-3,30-diformyl-2,20-binaphthol (S-M-
25
1) as yellow solids in 38.4% yield (1.2 g). [
a]
¼ ꢀ216.0 (c 0.5,
D
CH2Cl2). Mp: 150e152 ꢁC. 1H NMR (300 MHz, CDCl3):
d 10.55(s, 2H),
n-Bu
n-Bu
n-Bu
n-Bu
CHO
Br
(1) n-BuLi
(1) Br2
(1) n-BuLi
(2) n-BuBr
OMOM
OMOM
OH
OH
OMOM
OMOM
OH
OH
(2) DMF
(3) HCl
(2) NaH/MOMCl
CHO
Br
2
1
S-BINOL
S-M-1
S-M-1
n-Bu
n-Bu
N
H
N
H
NaBH4
THF
N
NH2
NH2
N
]
OH
]
OH
n
n
HO
[
HO
[
Bu-n
P-2
Bu-n
P-1
Scheme 1. Synthesis procedures of two chiral polymers P-1 and P-2.
S-M-2

J. Meng et al. / Polymer 52 (2011) 363e367
365
10.19(s, 2H), 8.28(s, 2H), 7.77(s, 2H), 7.30(dd, 2H, J ¼ 8.7, 1.8 Hz), 7.15
(d, 2H, J ¼ 8.7 Hz), 2.75(t, 4H, J ¼ 7.8 Hz), 1.73e1.67(m, 4H),
1.47e1.35(m, 4H), 0.96(t, 6H, J ¼ 7.2 Hz). 13C NMR (75 MHz, CDCl3):
6,60-dibromo-2,20-bis(methoxymethoxy)-1,10-binaphthyl
(1)
according to reported literatures [63]. Compound 2 was first lithi-
ated with n-BuLi, and then followed by carbonylation to afford the
MOM-protected intermediate, which was hydrolysed in HCl solu-
tion to afford the crude product (S)-6,60-dibutyl-3,30-diformyl-2,20-
binaphthol (S-M-1). The purification of S-M-1 could be carried out
by column chromatography on silica gel to afford a yellow solid
product in 38.4% yield [62]. The chiral polymer P-1 incorporating
(S)-2,20-binaphthol and (S)-2,20-binaphthyldiamine moieties could
be obtained by Schiff-base formation via nucleophilic addi-
tioneelimination reaction between S-M-1 and S-M-2 in 75% yield.
And polymer P-2 could be obtained by the reduction of P-1 with
NaBH4 in 81% yield. This two chiral polymers are air stable solid and
show good solubility in common solvents, such as toluene, THF,
CHCl3, and CH2Cl2, which can be attributed to the nonplanarity of
the twisted polymer chain backbone and the flexible n-butyl
substituents. TGA result of P-1 shows the chiral polymer has high
thermal stability without loss weight before 420 ꢁC and tends to
completely decompose at 750 ꢁC. (See Supporting information
Fig. S1) Therefore, polymer P-1 can provide a desirable thermal
property for practical application as a fluorescence sensor.
d
196.9, 153.1, 139.0, 137.9, 136.0, 132.5, 128.2, 127.9, 124.8, 122.1,
116.6, 35.3, 33.2, 22.4, 14.0. FT-IR (KBr, cmꢀ1): 3426, 2955, 2928,
2856, 1658, 1506, 1377, 1294. MS (EI, m/z): 454 (Mþ, 100%), 436
(11%), 411 (21%), 393 (15%). Anal. Calcd for C30H30O4: C, 79.27; H,
6.65. Found: C, 79.21; H, 6.67.
2.5. Preparation of P-1 (Scheme 1)
A mixture of Compound S-M-1 (0.1 g, 0.22 mmol) and S-BINAM
(S-M-2) (62.5 mg, 0.22 mmol) was dissolved in 10 mL of toluene.
The obtained solution was stirred at 80 ꢁC for 48 h. 20 mL of
Methanol was added to precipitate the yellow polymer. The
resulting polymer was filtrated and washed with methanol several
times and dried in the yield of 75% (0.12 g). GPC results:
25
Mw ¼ 10800, Mn ¼ 6230, PDI ¼ 1.73; [
a]
¼ þ83.4 (c 0.28, THF); 1H
D
NMR (300 Hz, CDCl3):
d
¼ 0.87e2.77 (m, 21H), 6.88e8.64 (m, 20H),
10.04e10.54 (m, 0.04H), 11.90 (s, 0.54H). FT-IR (KBr, cmꢀ1): 3467,
2957, 2927, 1625, 1610, 1588, 1506, 1260. Anal. Calcd for
C50H42N2O2: C, 85.44; H, 6.02; N, 3.99. Found: C, 79.07; H, 6.00; N,
4.04.
3.2. Fluorescence recognition of (D)- or (L)-phenylalaninol
2.6. Preparation of P-2 (Scheme 1)
The fluorescence response behavior of the two chiral polymers
on ( )- or ( )-phenylalaninol has been investigated by fluorescence
D
L
0.15 g polymer P-1 was dissolved in the mixed solvents of 10 mL
THF and 10 mL MeOH, and then NaBH4 was added in batches to the
above solution. The reaction mixture was stirred at room temper-
ature until the yellow color disappeared. The colorless solution was
stirred for another 30 min, and 10 mL water was added to stop the
reduction reaction. The mixture was extracted with CH2Cl2
(3 ꢂ 20 mL). The combined organic layers were dried with anhy-
drous Na2SO4 and evaporated under reduced pressure to afford
spectra. Fig. 1(a) shows the fluorescence spectra of P-1
(1.0 ꢂ 10ꢀ5 mol/L corresponding to (S)-BINOL unit in toluene
solution) upon addition of (D)- or (L)-phenylalaninol (0.1 mol/L in
THF) at 1:100 M ratio on excitation at 360 nm. Remarkable differ-
ences in fluorescence enhancement were observed as demon-
strated in Fig. 1(a), (L)-phenylalaninol has little effect on the
fluorescence of the polymer, on the contrary, (D)-phenylalaninol
causes a large increase in the fluorescence intensity of the polymer
under the same determination condition. It also can be found that
the fluorescent emission wavelengths do not show an obvious
difference between the guest-free polymer and guestepolymer
complexes. The selective recognition effect on the guest of the
chiral molecular isomers is related to the enantiomeric fluores-
cence difference ratio, ef [ef ¼ (Id ꢀ I0)/(Il ꢀ I0)]. Herein, I0 represents
the fluorescence emission intensity in the absence of the chiral
substrate, ID and Il are the fluorescence intensities in the presence of
salan-based polymer P-2 as a white solid (0.11 g, 73% yield).
25
[
a]
¼ þ71.9 (c 0.17, THF); 1H NMR (300 Hz, CDCl3):
¼ 0.91e2.68
d
D
(m, 25H), 6.55e8.45 (m, 20H),10.19 (s, 0.10H),10.52 (s, 0.04H). FT-IR
(KBr, cmꢀ1): 3528, 3412, 2963, 2927, 1619, 1598, 1511, 1262. Anal.
Calcd for C50H46N2O2: C, 84.95; H, 6.56; N, 3.96. Found: C, 84.78; H,
6.64; N, 4.01.
2.7. General procedure for the enantioselective molecular
recognition of host compounds to guest compounds
(
D
)-substrate and (
is 6.85 for this polymer, which indicates that this polymer can
exhibit highly enantioselective response toward )-phenyl-
L)-substrate, respectively [50,64]. The value of ef
1.0 ꢂ 10ꢀ5 mol/L solution of host compounds in toluene and
0.1 mol/L solution of guest compounds in THF were freshly
prepared. To give the mixed solutions of host and guest compound
with the mole ratio 1:1, 1:5, 1:10, 1:20, 1:50, 1:80 and 1:100,
3.00 mL host compound solution and a certain volume of guest
compound solution were added in each micro-test tube, respec-
tively. The resulting solution was allowed to stand at room
temperature for 12 h before the fluorescence measurement. Fluo-
rescence intensity of alone host compound solution and above
solution of host-guest compound solution were obtained on the RF-
5301PC Spectrometer under respective optimal exciting wave-
length with 3 nm exciting slit width and 3 nm emission wavelength
in fast scan speed.
(D
alaninol. The reason may be attributed to an inherent chiral
recognition property based on the steric repulsion of the chiral
polymer sensor for (
receptor containing imine and hydroxyl groups can well fit for the
formation of a more stable complex of S,S- complex as compared
to the S,S- diastereomeric complex. On the contrary, chiral polymer
P-2 shows no obvious enantioselective response toward ( )- or ( )-
D)-phenylalaninol. The building block of (S,S)-
D
L
D
L
phenylalaninol (Fig. 1(b)). In a set of comparable experiments, we
also studied the fluorescence response behavior of polymer P-1 on
other guest molecules. As shown in Fig. 1(c), polymer P-1 can
exhibit obvious enantioselective response toward
D
-alaninol, and
the value of ef is 1.86 at 1:100 M ratio. While using (
D
)-/( )-mandelic
L
acid, (R)-/(S)-phenylethylamine, or (D)-/(L)-phenylglycinol as guest
3. Results and discussion
molecules, no obvious fluorescence response on the enantiose-
lectivity of these guest molecule enantiomers was observed
although the fluorescence intensities can appear great enhance-
ment (See Supporting information Figs. S2eS4).
3.1. Syntheses and feature of the polymers
The synthesis procedures of the monomer S-M-1 and chiral
polymer sensors are shown on Scheme 1. (S)-6,60-dibutyl-2,20-bis
(methoxymethoxy)-1,10-binaphthyl (2) was synthesized from (S)-
In addition, the interaction of the chiral polymer P-1 with phe-
nylalaninol was investigated at a much broader concentration range
of the substrate. In regard to the fluorescence signal changes of this

366
J. Meng et al. / Polymer 52 (2011) 363e367
280
a
350
300
250
200
150
100
50
a
b
c
P-1+100eq
P-1+80eq
P-1+50eq
P-1+20eq
P-1+10eq
P-1+5eq
P-1+1eq
P-1
260
240
220
200
180
160
140
120
100
80
P-1
P-1+D-phenylalaninol
P-1+L-phenylalaninol
60
40
20
0
0
380 400 420 440 460 480 500 520 540
Wavelength(nm)
380 400 420 440 460 480 500 520 540
Wavelength(nm)
350
300
250
200
150
100
50
P-2
280
260
240
220
200
180
160
140
120
100
80
b
P-2+D-phenylalaninol
P-2+L-phenylalaninol
P-1+100eq
P-1+80eq
P-1+50eq
P-1+20eq
P-1+10eq
P-1+5eq
P-1+1eq
P-1
0
60
40
20
0
380 400 420 440 460 480 500 520 540
Wavelength(nm)
350
300
250
200
150
100
50
380 400 420 440 460 480 500 520 540
Wavelength(nm)
P-1
P-1+(D)-Alaninol
P-1+(L)-Alaninol
Fig. 2. Fluorescence spectra of P-1 with and without (D)-phenylalaninol (a), (L)-phe-
nylalaninol (b) at different molar ratios.
We further investigated the fluorescence response of polymer P-
1 on different enantiomeric compositions of phenylalaninol. The
fluorescence intensities based on various molar ratios of (
phenylalaninol revealed a fair linear relationship between I/I0 and
the percent of the ( )-phenylalaninol component (Fig. 4). The result
indicates that the enantioselective fluorescence sensor can be
effectively applied for enantiomer composition determination of
phenylalaninol.
L)- or (D)-
D
0
380 400 420 440 460 480 500 520 540
Wavelength(nm)
Fig. 1. Fluorescence spectra of P-1 (1.0 ꢂ 10ꢀ5 mol/L in toluene) with and without (D)-
and (L)-phenylalaninol (lex ¼ 360 nm, lem ¼ 404 nm) (a), P-2 (1.0 ꢂ 10ꢀ5 mol/L in
toluene) with and without (D)- and (L)-phenylalaninol (lex ¼ 360 nm, lem ¼ 414 nm)
(b), and P-1 with and without (D)- and (L)-alaninol (c) at 1:100 M ratio (lex ¼ 360 nm,
lem ¼ 404 nm).
24
22
20
Polymer P-1 +(D)-phenylalaninol
18
16
14
12
10
chiral polymer sensor on (
intensities appear gradual enhancement upon addition of (
phenylalaninol in the range from 1:0 to 1:100 M ratios (Fig. 2).
Meanwhile, it can also be found that the addition curve keeps
a nearly linear correlation with the molar ratio of (L)- or (D)-phe-
nylalaninol (Fig. 3). The obvious fluorescence enhancement can be
attributed to suppressed PET (photoinduced-electron-transfer)
quenching [65e68] when the protons of phenylalaninol interact
with the nitrogen atoms of imine moieties in the chiral polymer
main chain through the intramolecular hydrogen bonding. On
complexation, the lone pair of electrons on the nitrogen atom is no
longer available for PET, leading to the fluorescence enhancement.
L
)- or (
D
)-phenylalaninol, the fluorescence
D
)- or ( )-
L
Polymer P-1 +(L)-phenylalaninol
8
6
4
2
0
0
10 20 30 40 50 60 70 80 90 100
[phenylalaninol]x10-5 mol/L
Fig. 3. Fluorescence enhancement of the chiral polymer P-1 (1.0 ꢂ 10ꢀ5 mol/L in
toluene) vs molar ratios of (D)- and (L)-phenylalaninol from 1:1 to 1:100.

J. Meng et al. / Polymer 52 (2011) 363e367
367
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(D)-Enantiomer(%)
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Fig. 4. Fluorescence enhancement of the chiral polymer P-1 (1.0 ꢂ 10ꢀ5 mol/L in
toluene) vs the enantiomeric composition of phenylalaninol (1.0 ꢂ 10ꢀ3 mol/L in THF).
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In summary, a novel fluorescence-based polymer P-1 incorpo-
rating (S)-BINOL and (S)-BINAM moieties in the main chain back-
bone can exhibit an excellent fluorescence sensor for
enantioselective recognition of (
used in ascertaining the enantiomeric composition of (
phenylalaninol. The value of enantiomeric fluorescence difference
D)-phenylalaninol, and can also be
D
)- or ( )-
L
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Acknowledgment
[42] Li ZB, Lin J, Zhang HC, Sabat M, Hyacinth M, Pu L. J Org Chem 2004;69:6284e93.
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2010;122:612e6.
This work was supported by the National Natural Science
Foundation of China (No. 20774042, 20832001, 21074054), National
Basic Research Program of China (2010CB923303) and the Bureau
of Science and Technology of Wenzhou (No. S20100007).
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Appendix. Supporting information
Supporting information associated with this article can be found
online at doi:10.1016/j.polymer.2010.12.011.
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