Novel β-cyclodextrin-[60]fullerene conjugates based on huisgen [2+3] cycloaddition: Synthesis and dyes complexation properties

Article abstract of DOI:10.1007/s10847-015-0585-9

By using β-cyclodextrin aromatic aldehyde derivatives 5 and 6 as starting materials, the novel β-cyclodextrin-[ 60]fullerene conjugate 7 and bis- β-cyclodextrin-[ 60]fullerene conjugate 8 were designed and conveniently synthesized via the Huisgen [2+3] cy

Full text of DOI:10.1007/s10847-015-0585-9

J Incl Phenom Macrocycl Chem
DOI 10.1007/s10847-015-0585-9
ORIGINAL ARTICLE
Novel b-cyclodextrin-[60]fullerene conjugates based on Huisgen
[2+3] cycloaddition: synthesis and dyes complexation properties
1
1
1,2
1
Hongyu Guo
•
Xiaoting Fang
•
Fafu Yang
•
Yingmei Zhang
Received: 31 July 2015 / Accepted: 26 November 2015
Ó Springer Science+Business Media Dordrecht 2015
Abstract By using b-cyclodextrin aromatic aldehyde
derivatives 5 and 6 as starting materials, the novel b-cy-
clodextrin-[60]fullerene conjugate 7 and bis-b-cyclodex-
Based on their unique properties, they exhibited various
application prospective in the pharmaceutical, agrochemi-
cal, food and cosmetic fields [1–7]. For examples, some of
b-CDs derivatives and bis-b-CDs derivatives were reported
as good receptors for all kinds of organic dyes [8–12].
Given that the organic dyes are the aromatic molecules
with large conjugated structures, it is reasonable that the b-
CDs derivatives with large aromatic structures would
exhibit excellent binding abilities for dyes based on the p-p
interaction between aromatic conjugate groups and organic
dyes.
trin-[60]fullerene conjugate
8
were designed and
conveniently synthesized via the Huisgen [2?3] cycload-
dition for the first time. The UV–Vis complexation
experiments, fluorescence titration spectra and complexa-
tion ESI–MS spectrum suggested that they possessed
excellent binding abilities for dyes with 1:1 host–guest
complexes. The highest association constant of compound
5
for Orange I was as high as 6.97 9 10 .
8
On the other hand, [60]fullerene has been considered as
a powerful building block in material sciences and
supramolecular chemistry due to its unique aromatic con-
jugate structures. If C60 unit is introduced into b-cy-
clodextrin, the obtained b-CD-C60 conjugates might show
excellent dyes binding abilities based on the the p-p
intermolecular action. However, comparing with the
extensive studies of the supramolecular complexations of
b-CDs with C , the b-CD-C conjugates are seldom
reported up to now [13–16]. There were only two kinds of
synthetic methods for b-CD-C60 conjugates in literatures so
far. One was the 1,3-dipolar cycloaddition of b-CDs-N3
derivatives with C60 reported by Jiang [17], Wael [18] and
Noto groups [19], respectively. Another method was via
Hirsch–Bingel reaction described by Zhou and Liu [20,
Keywords b-Cyclodextrin Á [60]fullerene Á Synthesis Á
Complexation Á Dye
Introduction
Cyclodextrins (CDs) are shaped like a truncated cone,
rather than a perfect cylinder, as a consequence of the chair
conformation of the glucopyranose units. The capacity to
form inclusion complexes with a wide variety of guest
molecules is one of the most interesting properties of CDs.
6
0
60
Electronic supplementary material The online version of this
article (doi:10.1007/s10847-015-0585-9) contains supplementary
material, which is available to authorized users.
21]. Also, the electrochemical behaviors or DNA cleavage
performances of these b-CD-C60 conjugates were studied
but no complexation behavior was investigated. In this
paper, we firstly used the Huisgen [2?3] cycloaddition to
prepare novel b-cyclodextrin-[60]fullerene conjugate 7 and
bis-b-cyclodextrin-[60]fullerene conjugate 8. Also, the
dyes complexation behaviors of b-cyclodextrin-[60]-
fullerene conjugates were investigated for the first time.
The results suggested that novel b-cyclodextrin-
&
Fafu Yang
yangfafu@fjnu.edu.cn
1
College of Chemistry and Chemical Engineering, Fujian
Normal University, Fuzhou 350007, People’s Republic of
China
2
Fujian Key Laboratory of Polymer Materials,
Fuzhou 350007, People’s Republic of China
123

J Incl Phenom Macrocycl Chem
[
60]fullerene conjugates possess outstanding dyes com-
(1:4, V/V) as eluant). The compound 7 was obtained as
-
brown solid in yield of 26 %. Compound 7: IR/cm :
1
plexation abilities as expected.
1
919, 2849, 1664, 1509, 1377, 576, 526; H NMR
2
(
400 MHz, DMSO-d ) dppm: 2.83 (s, 3H, NCH ),
6
3
Experimental
3.25–4.02 (m, 42H, CH and CH ), 4.30 (bs, 1H, NCH -
2 2
(exo)), 4.41–4.51 (m, 6H, OH-6), 4.75–4.89 (m, 7H, CH),
General experimental information
5.05(s, 2H, CH O), 5.22 [bs, 1H, NCH -(endo)], 5.62–5.91
2
2
(
m, 15H, CH and OH-2,3), 7.2–8.25 (m, 5H, ArH and
3
1
IR spectra were recorded on a Perkin-Elmer PE-983
infrared spectrometer as KBr pellets with absorption in
NCH). C NMR (100 MHz, DMSO-d ) dppm: 163.2,
6
160.4, 155.2, 148.6, 147.1, 146.4, 145.5, 144.8, 144.3,
143.1, 142.8, 142.6, 141.9, 132.2, 131.8, 130.2, 126.0,
124.2, 115.9, 115.5, 103,8, 102.8, 101.9, 85.4, 84.1, 82.4,
82.0, 81.3, 73.6, 73.5, 73.2, 73.1, 72.8, 72.4, 72.1, 70.4,
68.3, 67.9, 61.7, 60.3, 59.9, 59.4, 50.4, 41.1. MS m/z (%):
-1 1
cm . H NMR spectra was recorded in DMSO-d on a
6
Bruker-ARX 600 instrument at 30 °C. Chemical shifts are
reported in ppm, using tetramethylsilane (TMS) as internal
standard. ESI–MS spectra were obtained from DECAX-
?
3
0000 LCQ Deca XP mass spectrometer (mobile phase:
2090.9 (MNa , 100). Anal. Calcd. For C H N O : C
114 82 4 35
MeCN, flow: MeCN, electrospray temperature: 450 °C).
Elemental analyses were performed at Vario EL III Ele-
mental Analyzer. TLC analysis was performed using pre-
coated silica gel glass plates. All chemicals were purchased
from commercial suppliers and used without further
purification. The other organic solvents and inorganic
reagents were purified according to standard anhydrous
methods before use. 4-(Prop-2-ynyloxy)benzaldehyde 3, 3,
66.21, H 4.00, N 2.71; found C 66.25, H 4.04, N 2.67 %.
Synthesis of b-cyclodextrin-[60]fullerene conjugate 8
Under N atmosphere, a mixture of compound 6 (0.63 g,
2
0.25 mmol), C60 (0.18 g, 0.25 mol), and sarcosine
(0.225 g, 2.5 mmol) in dry toluene (150 mL) was refluxed
for 48 h. After the reaction mixture was cooled to room
temperature, the solvent was removed under reduced
pressure and the residue was further purified by column
chromatography (SiO 100–200 mesh, methanol/CH Cl
2
4
-bis-(prop-2-ynyloxy)benzaldehyde 4 and b-CD deriva-
tives 5 and 6 were prepared according to published pro-
cedure [22].
2
2
All UV–Vis experiments were performed in DMSO
solution by adding aliquots stock solution of respective
dyes. The wavelength of the measurement in UV–Vis
spectra were 278 nm for OI(Orange I) and 266 nm for
NR(Neutral red), respectively. Fluorescence spectra were
measured in a conventional quartz cell (10 9 10 9 45 nm)
at 25 °C on a Hitachi F-4500 spectrometer equipped with a
constant-temperature water bath, with excitation and
emission slits 10 nm wide. The excitation wavelengths
were 310 nm. In the fluorescence titration experiments, the
(1:3, V/V) as eluant). The compound 8 was obtained as
-
1
:
brown solid in yield of 21 %. Compound 8: IR/cm
1
2922, 1668, 1506, 1262, 1150, 576, 523; H NMR
(400 MHz, DMSO-d ) dppm: 2.82 (s, 3H, NCH ),
6
3
3.19–3.95 (m, 84H, CH, CH ), 4.25–4.60 (m, 13H, NCH -
2
2
(exo) and OH-6), 4.75–4.98 (m, 14H, CH), 5.05 [bs, 1H,
NCH -(endo)], 5.33 (s, 4H, CH O), 5.61–5.91 (m, 29H, CH
2
2
1
and OH-2,3), 7.18–8.15 (m, 5H, ArH and NCH). C NMR
3
(100 MHz, DMSO-d ) dppm: 163.8, 163.6, 160.8, 156.3,
6
147.2, 145.9, 145.5, 144.8, 142.7, 142.4, 141.6, 139.9,
139.5, 136.4, 135.3, 131.2, 130.5,126.4, 126.0, 119.6,
115.9, 102,8, 102.4, 102.1, 84.4, 82.1, 81.7, 81.5, 73.4,
73.2, 72.6, 72.4, 72.1, 70.3, 69.2, 68.9, 61.5, 60.4, 60.1,
-
5
concentrations of hosts 7 and 8 were 1 9 10 M and the
concentrations of dyes were 0, 0.2, 0.4, 0.6, 0.8, 1.0,
-
5
.0 9 10 M, respectively, in the phosphate buffer (pH
2
7
?
.20). The stoichiometry of the complexes was determined
59.8, 59.4, 50.3, 41.2. MS m/z (%):3304.2 (MNa , 100).
by the Job method of continuous variations. The associa-
tion constant was calculated by Benesi–Hilderbrand for-
mula with nonlinear curve fitting procedure [23, 24].
Anal. Calcd. For C159H153N O : C 58.19, H 4.70, N 2.99;
7 70
found C58.12, H 4.75, N2.94 %.
Synthesis of b-cyclodextrin-[60]fullerene conjugate 7
Results and discussion
Under N atmosphere, a mixture of compound 5 (0.33 g,
2
Synthesis and characterization
0
.25 mmol), C60 (0.18 g, 0.25 mol), and sarcosine
(
0.225 g, 2.5 mmol) in dry toluene (100 mL) was refluxed
The synthetic routes were shown in Scheme 1. Although
Huisgen [2?3] cycloaddition was extensively applied in
preparing fullerene derivatives, it was not used in synthe-
sizing b-cyclodextrin-[60]fullerene conjugate due to the
absence of b-CD aromatic aldehyde derivative. Lately, we
for 48 h. After the reaction mixture was cooled to room
temperature, the solvent was removed under reduced
pressure and the residue was further purified by column
chromatography (SiO 100–200 mesh, methanol/CH Cl
2
2
2
1
23

J Incl Phenom Macrocycl Chem
Scheme 1 The synthetic route
of title compounds 7 and 8
HO
HO
OH
HO
OTs
N3
6
6
6
NaN3
TsCl
OH
2
OH
OH
14
14
Br
14
1
OHC
OHC
O
OHC
OHC
OH
K CO CH CN
2
3
3
3
OH
OH
Br
K CO , CH CN
O
2
3
3
O
4
HO
N
N N
O
CHO
6
sodium ascorbate
CuSO4, DMF
3
+
2
5
OH14
HO
N
6
N N
O
CHO
O
sodium ascorbate
CuSO4, DMF
OH
6
4
+
2
14
HO
N
N N
6
OH
14
CH3
N
O
HO
N
N N
6
C60
NH CH COOH
5
+
2
CH3
Toluene
7
OH
14
CH3
N
HO
N
N N
6
O
O
C60
NH CH COOH
6
+
2
OH
6
14
CH3
Toluene
HO
N
N N
8
OH
14
123

J Incl Phenom Macrocycl Chem
reported the synthesis of several b-cyclodextrin aromatic
aldehydes by click chemistry in good yields [22]. Thus, the
b-cyclodextrin-[60]fullerene conjugate 7 and bis-b-cy-
clodextrin-[60]fullerene conjugate 8 were designed and
synthesized by using these b-cyclodextrin aromatic alde-
hydes as reactants. As shown in Scheme 1, the mono-6-
azido-b-CD 2 was obtained from the readily available mono-
glucopyranose units [25–27]. Thus, the complete signal
assignment was difficult for these CD derivatives. By con-
1
3
trast, in C NMR spectra, the characteristic signals for tri-
azole cycle, NCH and NCH were observed obviously for
2
3
compounds 7 and 8. All these typical characterization of
spectra were similar to structures of mono-fulleropyrro-
lidine in literatures [28, 29].
6
-tosyl-b-CD according to references [22]. Subsequently, by
reacting compound 2 with 4-(prop-2-ynyloxy)benzaldehyde
or 3, 4-bis-(prop-2-ynyloxy)benzaldehyde 4, b-cyclodex-
Complexation Studies for dyes
3
trin aromatic aldehyde 5 and bis-b-cyclodextrin aromatic
aldehyde 6 were smoothly obtained by click reaction in
yields of 60–75 %. Finally, by treating compound 5 or 6 with
sarcosine and C60 in refluxing toluene, the novel b-cy-
clodextrin-[60]fullerene conjugate 7 and bis-b-cyclodex-
trin-[60]fullerene conjugate 8 were obtained via 1,3-dipolar
cycloaddition of azomethine ylides to C60 in isolated yields
of 21 and 26 % after column chromatography, respectively.
To the best of our knowledge, compounds 7 and 8 were the
first examples of b-cyclodextrin-[60]fullerene conjugates
via Huisgen [2?3] cycloaddition.
The inclusion complexes of compounds 7 and 8 were
investigated by titration of UV–Vis spectroscopy in the
presence of two normal dyes [Orange I (OI) and Neutral
red (NR)] with various concentrations (0.0, 0.2, 0.4, 0.6,
-
5
0.8, 1.0, 2.0 9 10 M). The results were shown in Figs. 2,
3, 4, 5 and 6. Moreover, based on the absorbance at
maximal absorption wavelength, the association constants
and correlation coefficients were calculated by Benesi–
Hildebrand equation, which was usually used to study the
complexation behaviors of host–guest [23, 24]. The cal-
culated formula was as follows:
The structures of new compounds 7 and 8 were charac-
1
terized by elemental analyses, UV, IR, ESI–MS, H NMR
H þ nG ! H Á nG
1
3
1
1
1
and C NMR spectra, etc. Their UV spectra exhibited the
typical absorption features of mono-fulleropyrrolidine at
¼
þ
n
DA KsDe½HŠ½GŠ
De½HŠ
4
33 nm as shown in Fig. 1. The ESI–MS spectra of com-
where H is host; G is guest; n is the ratio of complexation;
H] and [G] are the concentration of host and guest,
pounds 7 and 8 possessed corresponding pseudomolecular
?
ion peak (MNa ) at 2090.9 and 3304.2, indicating the
1
accomplishment of Huisgen [2?3] cycloaddition. The H
[
respectively; Ks is association constant; De is molar
absorption coefficient; DA is the change of absorbance at
maximal absorption wavelength.
NMR spectrum of compounds 7 and 8 also presented the
corresponding signals of protons. On the other hand, as
generally observed for substituted CDs, the proton signals at
sugar units were hardly exploitable due to overlapping and
broadening [25–27]. This phenomenon suggested a modifi-
cation of the conical CD structures leading to non-equivalent
The calculated results of correlation coefficients (R) and
associations constants were summarized in Table 1. One
can see that the values of correlation coefficients were
close to 1 when the ratios of complexation (n) were set as
1. These results suggested the formation of 1:1 host–guest
complexes for compounds 7 and 8 with dyes. The associ-
4
ations constants of compound 7 were higher than 10 but
1.0
0.8
0.6
0.4
0.2
0.0
5
that of compound 8 were higher than 10 . The highest
association constant of compound 8 with OI was as high as
5
6.97 9 10 . These results indicated that the more b-CD
units were favorable for dyes complexation based on the
cooperative action of polytopic b-CD units, which were in
accordance with other reports [25–27]. Moreover, com-
paring with their precursors 5 and 6 [22], compound 7
showed similar association constants to precursor 5, but
compound 8 exhibited far higher values of constants than
precursor 6. The better complexation abilities of compound
4
33 nm
8
7
8
could be attributed to cooperative complexation of C60
-
0.2
unit and b-CD unit by comparing the structures of com-
pound 8 and precursor 6. Compound 7 did not show the
similar changes, indicating that the cooperative action was
restrained. These phenomena might be ascribed to the self-
3
50
400
450
500
Wavelength (nm)
Fig. 1 UV–Vis spectra of compounds 7 and 8 in DMF solution
1
23

J Incl Phenom Macrocycl Chem
Fig. 2 The structures of the
tested organic dyes
N
H C
3
CH3
Cl-
N+
CH3
HO
N
H N
2
-
+
N
H
N
SO Na
3
Neutral red (NR)
Orange I (OI)
0
.5
-4
-5
Y =4.64597+3.16651*10
R=0.98476
X
Y =18.44239+2.64513*10
R=0.984
X
1
1
50
00
30
25
20
0
0
0
0
0
.4
.3
.2
.1
.0
2
.0
2
.0
0.4
0
.3
0.0
5
0
0
.0
0.2
0.1
0
100000 200000 300000 400000 500000
1/[G]
0
0
100000 200000 300000 400000 500000
1/[G]
0
.0
2
00
300
400
500
600
700
800
2
00
300
400
500
600
with OI)
700
800
Wavelength/nm ( 8
with OI)
Wavelength/nm (
7
-
5
Fig. 5 The UV titration spectra of compound 8 (1.0 9 10 M)
towards Orange I. The concentrations of dyes were from the bottom
-
5
Fig. 3 The UV titration spectra of compound 7 (1.0 9 10 M)
towards Orange I. The concentrations of dyes were from the bottom
-5
0
.0, 0.2, 0.4, 0.6, 0.8, 1.0, 2.0 (910 M)
-
5
0
.0, 0.2, 0.4, 0.6, 0.8, 1.0, 2.0 (910 M)
40
-4
-5
Y =10.64917+2.23625*10
R=0.991
X
Y =6.77054+5.70909*10
R=0.975
X
0
0
0
0
0
0
0
0
0
0
0
.20
.18
.16
.14
.12
.10
.08
.06
.04
.02
.00
2.0
0
0
.3
.2
2.0
1
00
20
5
0
0.0
0
0.0
0.1
0.0
0
100000
200000
300000
400000
500000
1/[G]
0
10000 20000 30000 40000 500000
/[G]
1
2
00
300
400
500
8
600
with NR)
700
800
Wavelength/nm (
2
00
300
400
500
7
600
with NR)
700
800
Wavelength/nm (
-
5
Fig. 6 The UV titration spectra of compound 8 (1.0 9 10 M)
towards Neutral red. The concentrations of dyes were from the bottom
-
5
Fig. 4 The UV titration spectra of compound 7 (1.0 9 10 M)
towards Neutral red. The concentrations of dyes were from the bottom
-5
0
.0, 0.2, 0.4, 0.6, 0.8, 1.0, 2.0 (910 M)
-5
0
.0, 0.2, 0.4, 0.6, 0.8, 1.0, 2.0 (910 M)
self-inclusion due to the steric hindrance of more CD units.
So compound 8 presented excellent dyes complexation
abilities based on the cooperative intermolecular action of
b-CD units and C60 unit. Based on the complexation
results, it was reasonable to deduce that the dye was binded
in the cavity composed of two b-CD units and C60 unit.
inclusion of C60 unit in cavity of b-CDs for compound 7,
which was usually observed in C -CDs derivatives com-
6
0
plexation systems [13–16]. This kind of self-inclusion was
disadvantageous for binding dyes. However, it was difficult
for bis-b-cyclodextrin-[60]fullerene conjugate 8 to form
123

J Incl Phenom Macrocycl Chem
Table 1 Association constants (K ) and correlation coefficients (R) for the complexation behaviors of compounds 7 and 8 with two dyes in the
s
UV titration spectra
Dyes
7
8
n
R
K
s
SD
n
R
K
s
SD
4
4
5
5
OI
1
1
0.985
0.991
1.45 9 10
4.76 9 10
1.2342
0.9476
1
1
0.975
0.984
6.97 9 10
1.18 9 10
1.2448
0.9874
NR
Also, the fluorescence titration spectra were employed
to test the complexation behaviors of compound 7 and 8 for
OI and NR. The results were exhibited in Figs. 7 and 8.
After calculation according to Benesi-Hildebrand equation,
the association constants and correlation coefficients were
summarized in Table 2. These results suggested the 1:1
host–guest complexes for compounds 7 and 8 with dyes.
Moreover, the K values for compound 7 and 8 with dyes
showed similar results to the UV titration spectra i.e. the K
s
s
5
values for compound 8 were at 10 , which were higher than
5
4
4
3
00
50
00
50
-
7
2
.0
Y =0.02625+5.635418*10
R=0.995
X
-
7
0.3
Y =0.01159+5.193818*10 X
R=0.993
0
.3
2
.0
4
4
3
50
00
50
0.2
0.2
0.1
0.0
0.1
0.0
0
100000 200000 300000 400000 500000
/ G
1
0.0
0
100000 200000 300000 400000 500000
1/[G]
3
50
360
Wavelength/nm
Compound with OI
370
350
360
Wavelength/nm
Compound 7 with NR
370
7
-
Fig. 7 The fluorescence titration spectra of compound 7 (1.0 9 10 M) with OI and NR. The concentrations of dyes were from the bottom 0.0,
5
-
5
0
.2, 0.4, 0.6, 0.8, 1.0, 2.0 (910 M)
450
400
350
450
0
0
0
.25
.20
.15
-7
Y =0.13217+2.40272*10
R=0.9525
X
-7
0
.3 Y =0.06674+5.00377*10
R=0.957
X
2.0
2
.0
0.2
4
3
00
50
0.0
0.1
0.0
0
100000 200000 300000 400000 500000
/[G]
1
0
100000 200000 300000 400000 500000
1/[G]
350
360
370
Wavelength/nm
Compound 8 for OI
350
360
370
Wavelength/nm
Compound for NR
8
-
Fig. 8 The fluorescence titration spectra of compound 8 (1.0 9 10 M) with OI and NR. The concentrations of dyes were from the bottom 0.0,
5
-
5
0
.2, 0.4, 0.6, 0.8, 1.0, 2.0 (910 M)
1
23

J Incl Phenom Macrocycl Chem
Table 2 Association constants (K ) and correlation coefficients (R) for the complexation behaviors of compounds 7 and 8 with two dyes in the
s
fluorescence titration spectra
Dyes
7
8
n
R
K
s
SD
n
R
K
s
SD
4
4
5
5
OI
1
1
0.993
0.995
2.23 9 10
4.69 9 10
1.0676
0.8392
1
1
0.953
0.957
5.51 9 10
1.14 9 10
2.4693
2.0321
NR
Fig. 9 The ESI–MS spectrum of compound 8 with Neutral red (mol ratio = 1:4)
4
that for compound 7 (order of magnitude at 10 ). Some
slight deviation for two sets of values in UV spectra and
fluorescence might be attributed to the operating skills and
the stability of apparatus. The highest association constant
aldehyde derivatives 5 and 6 with C60 via the Huisgen
[2?3] cycloaddition for the first time. Their structures were
confirmed by elemental analysis, FT-IR, ESI–MS and
NMR spectra. The UV–Vis and fluorescence complexation
experiments for Orange I and Neutral red indicated that
compound 7 showed similar complexation abilities to its
precursor 5 but bis-b-CD derivative 8 exhibited far better
complexation abilities than its precursor 6. The highest
association constant of compound 8 with OI was as high as
5
of compound 8 with OI was as high as 5.51 9 10 , which
was also in accordance with the UV titration results
approximately.
Furthermore, the ESI–MS spectrum was used to inves-
tigate the complexation behavior of compound 8 before
and after with excess Neutral red (mol ratio = 1:4) in
DMSO solution. The ESI–MS spectrum after complexation
was exhibited in Fig. 9. Two peaks were observed for
5
6.97 9 10 . Both UV–Vis titration spectroscopy, fluores-
cence titration spectra and complexation ESI–MS spectrum
indicated 1:1 complexes in DMSO solution. The excellent
dyes complexation abilities could be attributed to the
cooperative binding action of b-CD units and C60 unit,
which supplied a new idea for design and synthesis of
cyclodextrin derivatives with effective complexation abil-
ities for dyes.
?
?
compound 8 with Na (MNa ) at 3304.3 and the ion of the
complex formed between compound 8 and Neutral red
?
M?NR ) at 3557.4, respectively. It was interesting that
(
although four times of neutral red was added, only the 1:1
complexation peak appeared and the relative abundance
attained 100. This result indicated that the strong com-
plexation action existed between host and guest, and pre-
ferred to 1:1 binding ratio for complexation, which was
also in agreement with the result of UV–Vis spectra. In a
word, all the complexation experiments suggested that
compounds 7 and 8 exhibited excellent complexation
abilities for dyes with 1:1 stoichiometric ratio in DMSO
solution.
Acknowledgments This work was supported by National Natural
Science Foundation of China (No: 21406036), Fujian Natural Science
Foundation of China (No. 2014J01034), Fujian province science and
technology key project (2014N0025) and the Program for Innovative
Research Team in Science and Technology in Fujian Province
University.
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