6-TIPS-β-Cyclodextrin-Modified Fe3O4 for Facile Enantioseparation of 1-(1-Naphthyl)ethylamine

Article abstract of DOI:10.1002/asia.201601151

A new type of chiral magnetic nanoparticle was prepared from covalently linked magnetic nanoparticles (Fe₃O₄) and heptakis-(6-O-triisopropylsilyl)-β-cyclodextrin (6-TIPS-β-CD). The resulting selectors (TIPS-β-CD-MNPs) combined the good magnetic properties Fe₃O₄ and efficient chiral recognition ability of 6-TIPS-β-CD. The enantioselectivity of TIPS-β-CD-MNPs towards 1-(1-naphthyl)ethylamine was six times higher than that of the parent β-CD modified Fe₃O₄ particles.

Full text of DOI:10.1002/asia.201601151

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Accepted Article
Title: 6-TIPS-β-cyclodextrin modified Fe3O4 for a facile enantio-separation of 1-(1-
naphthyl) ethylamine
Authors: Lu Wang; Xiang-Yong Liang; Li-Sheng Ding; Sheng Zhang; Bang-Jing Li
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6-TIPS-β-cyclodextrin modified Fe3O4 for a facile enantio-
separation of 1-(1-naphthyl) ethylamine
Lu Wang,[a,c] Xiang-Yong Liang,[a,c] Li-Sheng Ding,[a] Sheng Zhang*[b] and Bang-Jing Li*[a]
Abstract:
A
new type of chiral magnetic nano-particles was
separation using magnetic particles have advantage of
convenience and economy, designing magnetic chiral selector
with high chiral recognition is still a challenge.
prepared via covalently linked magnetic nano-particles (Fe3O4) and
heptakis (6-O-triisopropylsilyl)-β-cyclodextrin (6-TIPS-β-CD). The
resulting selectors (TIPS-β-CD-MNPs) combined the high magnetic
property Fe3O4 and efficient chiral recognition ability of 6-TIPS-β-CD.
The enantioselectivity of TIPS-β-CD-MNPs towards 1-(1-naphthyl)
ethylamine was six times higher than that of parent β-CD modified
Fe3O4 particles.
β-CD and its derivatives are usually used as chiral selectors[10h]
because the asymmetrical cavity of β-CD can form inclusion
complexes with some chiral molecules via host-guest
interaction[11]. Recently, Akashi group demonstrated that high
chiral selectivity of aromatic amines can be realized through
host-guest interaction of 6-O-triisopropylsilyl-β-cyclodextrins (6-
TIPS-β-CD)[12]. However, the host-guest inclusion complex still
dissolved in solvent and hard to separate from mixture solution
directly. In this study, we prepared 6-TIPS-β-CD modified
magnetic nanoparticles (Fe3O4) as a chiral selecting system. The
resulting selectors combined the efficient chiral recognition
ability of 6-TIPS-β-CD for 1-(1-naphthyl) ethylamine and the
advantages of magnetic separation convenient separation
process, low-cost in time and labor. 1-(1-Naphthyl) ethylamine is
an important pharmaceutical intermediate for the synthesis of
chiral drugs and catalysts[13]. Up to now, most important splitting
methods of 1-(1-naphthyl) ethylamine, chemical resolution using
the D-tartaric acid as chiral reagent, have been explored. The
procedure is expensive in time and labour[14]. The TIPS-β-CD
modified Fe3O4 nanoparticles developed by this study provide an
alternative way for effective and facile separation of 1-(1-
naphthyl) ethylamine.
,
Introduction
Chirality is a common phenomenon in organic molecules
especially drug molecules. The two enantiomers of chiral
medicine molecules have different biological activities in living
body[1]. Therefore, it is very important to get single-enantiomer
molecules for pharmaceutical and biochemical fields. Various
methods have been applied for the separation of enantiomers,
including high performance liquid chromatography (HPLC)[2], gas
chromatography (GC)[3], supercritical fluid chromatography
(SFC)[4], simulated moving bed chromatography (SMB)[5],
capillary electrophoresis (CE)[6], nano-materials[7] and classical
chemical resolution[8]. Recently, magnetic nano-materials have
been started to be used as good candidate for enantioselective
separation because the separation process is very convenient
and there is no need of expensive equipment, as well as time-
consuming procedures[9]. In 2009, Hyun group[9a] demonstrated
that magnetic particles modified by a chiral selector can be used
in the direct separation of enantiomers firstly. Since then,
several research groups[10] have focused on chiral separation of
racemates via magnetic nano-materials. For example, Lee
group[10e] reported a type of chiral zirconia magnetic nano-
materials and demonstrated an effective separation of different
kinds of chiral drugs. Yang and coworkers[9d,10a,10f] prepared a
series of magnetic microsphere modified by dendrimers, human
serum albumin (HAS) or β-cyclodextrin (β-CD) polymer for chiral
separation of drugs and amino acid. Zou et. al[10g] reported β-CD
functionalized magnetic nanospheres for enantio-separation of
amino acid enantiomers. However, it should be noticed that the
enantiomeric excess (ee) of enantiomers separated by most
magnetic particles was below 60%[10b,10c]. Although enantio-
Results and Discussion
The fabrication of TIPS-β-CD modified Fe3O4 nanoparticles was
illustrated in Scheme 1. Fe3O4 nanoparticles (MNPs) were
synthesized by the traditional co-precipitation method[15]. The
TIPS-β-CD were coated on the surface of Fe3O4 particles via the
nucleophilic substitution reaction of the 2-(p-tolylsulfonyl)-6-
TIPS-β-CD with 3-aminopropyltriethoxysilane-modified magnetic
nanoparticles (ATPES-MNPs) (see the supplementary
information for details).
To demonstrate the successful coating 6-TIPS-β-CD on the
surface of MNPs (TIPS-β-CD-MNPs), the products were studied
with FT-IR spectroscopy. The IR spectra of MNPs, APTES-
MNPs, TIPS-β-CD-MNPs in the range of 500 - 4000 cm-1 were
showed in Figure 1a. For MNPs, two strong absorption bands at
around 570 and 3438 cm-1, corresponded to the Fe-O bond and
-OH stretching vibration of Fe3O4. The above two characteristic
bands may be observed with a little shift after coating with
APTES and β-CD. Compared APTES-MNPs with MNPs, the Si-
O-H and Si-O-Si absorption was observed at 1044 and 1107 cm-
1; The broad band at 1626 cm-1 is -NH stretching vibrations
indicating that APTES capped on the surface of MNPs. For
TIPS-β-CD-MNPs sample, the significant broad peaks of β-CD
appeared in the range of 900 - 1200 cm-1, suggesting that β-CD
have successfully coated on the magnetic nanoparticles.
[a]
Lu Wang, Xiang-Yong Liang, Prof. Dr. Li-Sheng Ding, Prof. Dr.
Bang-Jing Li
Key Laboratory of Mountain Ecological Restoration and Bioresource
Utilization, Chengdu Institute of Biology
Chinese Academy of Sciences, Chengdu, 610041 (China)
E-mail: libj@cib.ac.cn
[b]
[c]
Prof. Dr. Sheng Zhang
State Key Laboratory of Polymer Materials Engineering, Polymer
Research Institute of Sichuan University
Sichuan University, Chengdu, 610065 (China)
E-mail: zslbj@163.com
Thermogravimetric analysis (TGA) was performed to
investigate the amount of β-CD on the surface of MNPs. As
shown in Figure 1b, MNPs showed about 3.84% weight loss
Lu Wang, Xiang-Yong Liang
University of Chinese Academy of Sciences, Beijing,100049 (China)
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◦
below 200 C, which might because the loss of the absorbed
that all the particles were spherical with a narrow size
◦
water. From 200 to 700 C, the weight loss was about 3.4%
distribution. The average size of TIPS-β-CD-MNPs is a little
bigger than MNPs, implying that β-CD formed a coating layer on
the surfaces of MNPs.
owning to the dehydration of surface -OH groups. Over the full
temperature, the totally weight loss was about 7.23%. The TGA
curve of APTES-MNPs appeared two steps weight loss, 200 -
700 C. From the TGA curve of TIPS-β-CD-MNPs, a sharply
drop loss of 10.22% can be seen in range of 200 - 700 C ,
which was due to the decomposition of APTES and β-CD. The
difference value between APTES-MNPs and TIPS-β-CD-MNPs
was the loss of 6-TIPS-β-CD. Therefore, the amount of 6-TIPS-
β-CD covered on the MNPs surface is 4.83% (48.3 mg/g) and
the amount of β-CD covered on the MNPs surface is 4.68%
(46.8 mg/g) based on the TG curve in Figure S9. According to
this method (assuming the nanoparticles to be spherical, based
on the weight loss of TG), the average number of 6-TIPS-β-CD
units surrounding one MNPs was calculated to be 520 and the
average number of β-CD units covered on one MNPs was
calculated to be 513 (The details showed in supporting
information).
The XRD diffraction patterns of MNPs and TIPS-β-CD-MNPs
were shown in Figure 3. All the diffraction peaks of TIPS-β-CD-
MNPs were consistent with the MNPs (2θ=30.51, 35.67, 43.67,
53.89, 57.35, 63.13, related to the corresponding indices (2 2 0),
(3 1 1), (4 0 0), (4 2 2), (5 1 1) and (4 4 0) respectively.),
suggesting that modification of magnetic nanoparticles with
TIPS-β-CD did not change the crystal form of Fe3O4. Vibration
sample magnetometer (VSM) technique is used to measure the
magnetization properties and magnetization values at room
temperature under external magnetic field. The hysteresis loops
of MNPs and TIPS-β-CD-MNPs were shown in Figure 3b. It can
be seen that coercivity and remanence of all samples were zero,
◦
◦
indicating
that
MNPs
and
TIPS-β-CD-MNPs
are
superparamagnetic. Saturation magnetization value of TIPS-β-
CD-MNPs and MNPs were 63.91 and 70.43 emu•g-1,
respectively. Although the saturation magnetization values of
TIPS-β-CD-MNPs were a little lower than that of MNPs due to
the presence of non-magnetic organic content, they were large
enough to be separated from solution via applied an external
magnetic field.
NH OH
N
2
4
O H
OH
O H
Fe2+
Fe3+
80℃ 30min
OSi-i-Pr
O H
7
70℃ 3d
Cl
Si
N 2
OSi-i-Pr
OSi-i-Pr
7
7
N aH N 2
3 h
Ts-Cl
OTs
ATPES CH 3CH 2O H
H 2 N 2 60℃ 7 h
O H
OH
O H
O
Si
CH
NH
2
2
O
O
O
3
OSi-i-Pr
7
O
Si
C H
NH
2
2
O
O
3
O Ts
OSi-i-Pr
7
Figure 2. MNPs, TIPS-β-CD-MNPs were measured by TEM and DLS. (a)
TEM image of MNPs. (b) DLS of MNPs. (c) TEM image of TIPS-β-CD-MNPs.
(d) DLS of TIPS-β-CD-MNPs.
D M F N 2
O
Si
CH
N
H
O
2
3
O
60℃ 7 h
Scheme 1. Schematic strategy for synthesizing modified magnetic
nanoparticles.
Figure 3. (a) XRD patterns of MNPs and TIPS-β-CD-MNPs. (b) Magnetization
curves of MNPs and TIPS-β-CD-MNPs.
It has been reported that β-CD and β-CD polymer
functionalized MNPs could applied for the enantio-separation of
amino acid[10a][16]. In this study, the TIPS-β-CD-MNPs were
utilized in the separation of 1-(1-naphthyl) ethylamine. The
process of chiral recognition is showed in Scheme 2.
Figure 1. (a) FTIR spectra of MNPs, APTES-MNPs and TIPS-β-CD-MNPs. (b)
TGA curves of MNPs, APTES-MNPs and TIPS-β-CD-MNPs.
The TEM images and particles size distribution of MNPs and
TIPS-β-CD-MNPs were showed in Figure 2a-2d. It can be seen
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CD-MNPs possess high chiral recognition towards S-1-(1-
naphthyl) ethylamine and are powerful chiral selector.
Scheme 2. The process of chiral recognition by TIPS-β-CD-MNPs.
Table 1. Association Constant for TIPS-β-CD, β-CD and chiral 1-(1-naphthyl)
ethylamine
Host
Association constant
Selectivy
KS/KR
10.19
1.28
KR
KS
TIPS-β-CD
β-CD
3.04×106 L2/mol2
634 M-1
3.1×107 L2/mol2
809 M-1
It was found that the S-1-(1-naphthyl) ethylamine was
selectively taken by TIPS-β-CD-MNPs and the stereoselective
ability of TIPS-β-CD-MNPs was much better than that of parent
β-CD modified MNPs. As shown in Figure 4a, the supernatant
enantiomeric excess (ee) of 1-(1-naphthyl) ethylamine was 65%
after interaction with TIPS-β-CD-MNPs and the ee of the
complexed amine after decomplexation from the host was
showed in supporting information (in Figure S16, Figure S17 and
Figure S18). The results show that the ee of the complexed
amine after decomplexation from the host is in accordance with
the ee of supernatant, comfirming that the ee of TIPS-β-CD-
MNPs for 1-(1-naphthyl)ethylamine was 65% in deed, while ee
was only 10.3% after treatment with parent β-CD modified MNPs.
To explore the enantioselectivity mechanism of TIPS-β-CD-
MNPs for 1-(1-naphthyl) ethylamine, the association constants
of TIPS-β-CD and β-CD host molecules with 1-(1-
naphthyl)ethylamine isomers were investigated using ultraviolet
spectrophotometry methods method respectively (The details
was showed in supporting information Figure S34, S35 and
Figure S36, Figure S37). The results showed in Table 1 that the
TIPS-β-CD had clear binding selectivity for S-1-(1-naphthyl)
ethylamine. The association constant values (K) between TIPS-
β-CD and S-1-(1-naphthyl) ethylamine was 3.10×107, while K
between TIPS-β-CD and R-1-(1-naphthyl) ethylamine was only
3.04×106. KS/KR of TIPS-β-CD was 10.19. However, in the case
of β-CD, KS/KR was only 1.28. These results suggested that the
substitution of triisopropylsilyl influenced inclusion greatly.
Akashi et. al[12a] have demonstrated that the S-1-(1-naphthyl)
ethylamine molecules could incorporated within the
supramolecular capsule cavity formed by the two TIPS-β-CD
Figure 4. Results of HPLC. (a) Supernatant enantiomeric excess of 1-(1-
naphthyl) ethylamine after interaction with CD-MNPs and TIPS-β-CD-MNPs.
(b) Data of TIPS-β-CD-MNPs for chiral separating 1-(1-naphthyl) ethylamine in
different temperatures. (c) Enantiomeric excess of supernatant with adding
different amounts of TIPS-β-CD-MNPs. (d) Data of recycle used of TIPS-β-
CD-MNPs for chiral separating 1-(1-naphthyl) ethylamine.
It has been also demonstrated that the extents of penetration of
1-(1-naphthyl) ethylamine into the TIPS-β-CD cavity is also
affected by solvent. For example, 1-(1-naphthyl) ethylamine
molecule penetrates deeper into the TIPS-β-CD cavity in
cyclohexane than the case of benzene as the solvent, resulting
in a high chiral selectivity in cyclohexane[12b]. In this study, we
measured the chiral separation ability of TIPS-β-CD-MNPs for 1-
(1-naphthyl) ethylamine in cyclohexane, benzene, water and
methyl alcohol, respectively. It can be seen that the TIPS-β-CD-
MNPs showed higher chiral separation effect in nonpolar
solvents than in polar solvents, and the chiral selectivity was
best in cyclohexane (in Table 2). These results are quite
consistent with the case of TIPS-β-CD host, suggesting that
linking TIPS-β-CD molecules to magnetic nanoparticles did not
change their chiral ability. Therefore, cyclohexane was selected
as solvent in the later study. The effect of temperature on the
chiral recognition of 1-(1-naphthyl) ethylamine by TIPS-β-CD-
MNPs was also studied. As shown in Figure 4b, we did our
molecules,
and
the
naphthalene
ring
of
S-1-(1-
naphthyl)ethylamine penetrates deeper into the CD cavity than
the naphthalene ring of R-1-(1-naphthyl) ethylamine because
NH2 groups of S-1-(1-naphthyl) ethylamine are able to form
hydrogen bonding with the 3-OH groups of TIPS-β-CD. Figure 5
shows a representative spectrophotometric titration curve to
determine the coordination stoichiometry of TIPS-β-CD with 1-
(1-naphthyl) ethylamine. As can be seen in Figure 5a, 5b, the
Job plot for the TIPS-β-CD/1-(1-naphthyl) ethylamine displays a
maximum at 0.67, which corresponds to a 2:1 TIPS-β-CD/1-(1-
naphthyl) ethylamine stoichiometry. But the β-CD/1-(1-naphthyl)
ethylamine was 1:1 complex in Figure 5c, 5d. Therefore, TIPS-β-
◦
◦
◦
experiments in three different temperatures (0 C, 25 C, 40 C).
The experiments data displayed that when experimental
temperature was higher than room temperature, the effective for
the chiral recognition is declined. However, below the room
temperature, the change of temperature cannot remarkable
affect the effective for the chiral recognition. These results may
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be due to the decrease of the association constant at higher
temperatures.
It is known that the association and dissociation of CD-based
inclusion are easily controlled by temperature change[17]
.
Therefore, the TIPS-β-CD-MNPs could repetitious recycle after
facile thermal treatment. As shown in Figure 4d, although the
enantio-separation capacity of the TIPS-β-CD-MNPs decreased
gradually after a few cycles, their separation efficiency still
maintained 70% after 3rd recycle.
Table 2. Effects of solvents on the chiral separation ability of TIPS-β-CD-
MNPs for 1-(1-naphthyl) ethylamine at 25 ◦C.
Solvents
Enantiomeric excess(%)
64.8
cyclohexane
benzene
TIPS-β-CD-MNPs in
nonpolar solvents
35.5
Conclusions
water
12.8
1.5
TIPS-β-CD-MNPs in
polar solvents
methylalcohol
In conclusion, a kind of chiral magnetic nanoparticles with high
magnetic saturation value was successfully fabricated using 6-
TIPS-β-CD as a chiral selector. Stereoselective absorption
experiments using 1-(1-naphthyl) ethylamine as a model of
aromatic amines indicated that these TIPS-β-CD-MNPs showed
high chiral recognition ability and could be to recycle easily.
Therefore, the TIPS-β-CD-MNPs exhibited specificity for the
chiral selectivity for the 1-(1-naphthyl) ethylamine and these
TIPS-β-CD-MNPs are expected to be good candidates as chiral
selector in the pharmacological and biomedical research areas.
Experimental Section
Synthesis of heptakis (6-O-triisopropylsilyl)-cyclodextrin (6-TIPS-β-CD)
Figure 5. (a) Job plot of TIPS-β-CD/R-1-(1-naphthyl) ethylamine by UV-
spectra in cyclohexane. (b) Job plot of TIPS-β-CD/S-1-(1-naphthyl) ethylamine
by UV-spectra in cyclohexane. (c) Job plot of β-CD/S-1-(1-naphthyl)
ethylamine by UV-spectra in DMSO. (d) Job plot of β-CD/R-1-(1-naphthyl)
ethylamine by UV-spectra in DMSO.
The method of prepare heptakis (6-O-triisopropylsilyl)-cyclodextrin (6-
TIPS-β-CD) is according to the previous reports with
a slight
modification[12b]. Under a N2 atmosphere, β-CD (4.06 g, 3.56 mmol) and
imidazole (6.94 g, 102 mmol) were dissolved in DMF (90 ml). Into this
solution, was added triisopropylsilyl chloride dropwise under stirring at
room temperature, and then the resulting mixture was stirred for three
days at 70 ˚C. After cooled down to room temperature, the reaction
mixture was precipitated out by adding 500 mL ice pure water. The
precipitate was filtered and washed with pure water and was extracted
with saturated NaHCO3 solution. Then the supernatant was dried over
anhydrous MgSO4. After the solvent was removed, the resulting solid
was purified by silica gel column chromatography (gradient 50:1-3:1
chloroform/methanol). The product was confirmed by 1H NMR and 13C
NMR (400 MHz, CDCl3) in Figure S1 and Figure S2. MALDI-TOF MS:
m/z 2252 [M+Na]+. The yield is about 18%.
Under the optimum separation conditions, the influence of the
amount of TIPS-β-CD-MNPs on the efficiency of enantio-
separation was estimated. As shown in Figure 4c, the value of
ee increased firstly and then decreased with the increasing
amount of MNPs. The reached a maximum with adding 300 mg
TIPS-β-CD-MNPs into cyclohexane, suggesting that entrapment
efficiency was reached saturation. Based on the standard curve
in Figure S23, loading capacity and the mount of complexed
amine in the nanoparticles is 105.36 ug/g.
Synthesis of mono- mono-2-Tos-cyclodextrin
In order to determine the scope and limitations of the TIPS-β-
CD-MNPs, two comparison experiments were carried out (The
details was showed in supporting information), in which the
TIPS-β-CD-MNPs were used to separate α-methylbenzylamine
and 1-(1-naphtyl) ethanol. The results were provided in the
supporting information (in Figure 31 and Figure S32). It was
found that TIPS-β-CD-MNPs did not show chiral selectivity for α-
methylbenzylamine at all, which may be due to the mismatch
between the benzene group and the one β-CD. It is a little
surprised that TIPS-β-CD-MNPs did not show chiral selectivity
for 1-(1-naphtyl)ethanol neither, indicating that not only the size
of guest molecule, the sort of side groups also played important
role in the recognition of TIPS-β-CD-MNPs. So according to
these results, we can conclude that the TIPS-β-CD-MNPs
showed specificity for the chiral selectivity for the 1-(1-naphthyl)
ethylamine.
The technique of synthesizing mono-2-Ts-β-CD was based on the
previous reports[18]. Cyclodextrin 5 g (4.4 mmol) (dried overnight at
117 °C) in 40 ml dry DMF was added 176 mg (60% in oil, 4.4 mmol) of
NaH and the mixture was stirred overnight until the solution became clear.
This solution was added drop wise to a solution of 0.839 g (4.4 mmol) of
Toluene sulfonyl chloride in 5 ml DMF with stirring and allowed to stand
at room temperature for 30 min. β-cyclodextrin and its derivatives were
precipitated out by addition of 500 ml of acetone. The precipitate was
filtered and purified by macroporous resin (gradient 0-100%
methanol/water). The product was confirmed by 1H NMR and 13C NMR
(400 MHz, DMSO) in Figure S3 and Figure S4. MALDI-TOF MS: m/z
1288 [M-H]-. The yield is about 35%.
Synthesis of mono-2-Tos-heptakis(6-O-triisopropylsilyl)-cyclodextrin (2-
Ts-6-TIPS-β-CD)
The method of prepare mono-2-Tos-heptakis(6-O-triisopropylsilyl)-
cyclodextrin was similar with synthesis of 2-Tos-β-CD[19]. The product
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was confirmed by 1H NMR and 13C NMR (CDCl3) in Figure S5 and Figure
S6. MALDI-TOF MS: m/z 2406 [M+Na]+. The yield is nearly 23%.
Calculation of the number of β-CD on each of magnetic nanoparticles.
By assuming the core shape of nanoparticles to be spherical, the
average number of CD units around one nanoparticle (N) could be
calculated by the equations listed below:
Preparation of APTES-coated-Fe3O4 magnetic nanoparticles
Fe3O4-MNPs were prepared based on the traditional co-precipitation[20]
.
（ ）
FeCl3•6H2O (5.835 g, 0.0216 mol) and FeSO4•7H2O (3.001 g, 0.0108
mol) were dissolved in 100 ml deoxygenated water at 85 ◦C under a flow
of nitrogen. Then, 7.5 ml of ammonium hydroxide was quickly injected
into the reaction mixture in one portion. The colour of solution turned
from orange to black immediately. The formation of the black precipitates
was Fe3O4-MNPs. After the mixtures was cooled down to room
temperature. The magnetic precipitates were washed with pure water for
three times. The MNPs were dried in a vacuum desiccator for 24 h at 30
◦C. Then, the obtained MNPs powder (300 mg) was dispersed in ethanol
(90 ml) and water (1 ml) by sonication before APTES (120 ul) was added
to the mixture. After mechanically agitation for 7 h at 60 ◦C, the
suspended substance was separated with centrifugation (10,000 rpm for
30 min). The settlement product was re-dispersed in ethanol by
sonication and isolated with magnetic decantation for 5 times. The
precipitated product (APTES-MNPs) was dried at room temperature
under vacuum.
MMNPs
=
MCD
N =
=
（ ）
=
Where MMNPs and MCD are the molar number of magnetic nanoparticles
(MNPs) and 6-TIPS-β-CD, respectively. WMNPs, WCD, and DMNPs are the
iron content (obtained from TGA data, Figure 2b), cyclodextrin content
(obtained from TGA data, Figure 2b), Fe3O4 density, respectively. r is the
radius of nanoparticles (obtained from TEM results). NA is the Avogadro
content (6.02×1023). MWCD is the molecular weight of 6-TIPS-β-CD or β-
CD (M=2225 or M=1135). N is the number of β-CD on each of
nanoparticles.
Acknowledgements
Preparation of CD-functionalized MNPs
This work was funded by National Natural Science Foundation
of China(Grant Nos. 51573187, 51373174), and the West Light
Foundation of CAS.
APTES-MNPs (0.302 g) were suspended in DMF[21]
. Then, the
suspension was heated to 70◦C and mechanically agitated. The solution
of as-synthesized 2-Ts-β-CD (0.473 g) was added dropwise under
nitrogen protection. After 6 h, the reaction solution was cooled to room
temperature and diluted with 50 ml of ethanol, and then repeated the
procedure of magnetic decantation for three times. The sample was
stored at room temperature in vacuum. The black powder is β-CD
modified on surface of MNPs (named CD-MNPs). The method of
synthesizing 6-TIPS-β-CD-MNPs (named TIPS-β-CD-MNPs) was the
same as above-mentioned process with 2-Ts-6-TIPS-β-CD instead of 2-
Ts-β-CD.
Keywords: magnetic nanoparticles • enantio-seperation • host-
guest interaction
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Loading capacity
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=
[1-(1-naphthyl)ethylamine in feed － 1-(1-
mass of nanoparticles
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ug/g.
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10.1002/asia.201601151
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In this study, a new kind of chiral
magnetic nanoparticles with high
magnetic saturation and high chiral
recognition ability was successfully
fabricated using 6-TIPS-β-CD as a
Lu Wang, Xiang-Yong Liang, Li-Sheng
Ding, Sheng Zhang* and Bang-Jing Li*
Page No. – Page No.
6-TIPS-β-cyclodextrin modified Fe3O4
for a facile enantio-separation of 1-(1-
naphthyl) ethylamine
chiral
selector.
Stereoselective
absorption experiments using 1-(1-
naphthyl) ethylamine as a model of
aromatic amines indicated that these
TIPS-β-CD-MNPs showed high chiral
recognition ability
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