Synthesis, spectral properties of cyanine dyes-β-cyclodextrin and their application as the supramolecular host with spectroscopic probe

Article abstract of DOI:10.1016/j.dyepig.2012.08.010

Six new cyanine dye functionalised β-cyclodextrins were designed and synthesized to improve the drawback of the inadequate chromophore in β-cyclodextrin and to be suitable for the study of supramolecular interactions directly by visible spectroscopy. The dye structures were confirmed by ¹H NMR, IR, UV-Vis and HRMS. The UV-Vis spectra of the new cyanine dyes in different solvents were investigated. The inclusion behaviour of a quinocyanine derived β-cyclodextrin dye which was used as the supramolecular host with 1-adamantanol or vitamin B₆ was investigated. The results indicated that the stoichiometry for the inclusion complex of the quinocyanine derived β-cyclodextrin dye and both 1-adamantanol and vitamin B₆ was 1:1, and their inclusion constants were 9.39 × 10⁴ L/mol and 6.14 × 10² L/mol, respectively. The quinocyanine derived β-cyclodextrin dye was also used as the supramolecular host for the analysis of vitamin B₆ in tablets with satisfactory results.

Full text of DOI:10.1016/j.dyepig.2012.08.010

Dyes and Pigments 96 (2013) 180e188
Contents lists available at SciVerse ScienceDirect
Dyes and Pigments
journal homepage: www.elsevier.com/locate/dyepig
Synthesis, spectral properties of cyanine dyes-
b-cyclodextrin and their application
as the supramolecular host with spectroscopic probe
*
Jun-Long Zhao, Ying Lv, Hai-Jing Ren, Wei Sun, Qi Liu, Yi-Le Fu, Lan-Ying Wang
Key Laboratory of Synthetic and Natural Functional Molecule Chemistry, Ministry of Education, College of Chemistry and Materials Science, Northwest University,
Xi’an 710069, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Six new cyanine dye functionalised
b-cyclodextrins were designed and synthesized to improve the
Received 11 November 2011
Received in revised form
6 August 2012
Accepted 6 August 2012
Available online 14 August 2012
drawback of the inadequate chromophore in b-cyclodextrin and to be suitable for the study of supra-
molecular interactions directly by visible spectroscopy. The dye structures were confirmed by 1H NMR,
IR, UVeVis and HRMS. The UVeVis spectra of the new cyanine dyes in different solvents were investi-
gated. The inclusion behaviour of a quinocyanine derived
supramolecular host with 1-adamantanol or vitamin B6 was investigated. The results indicated that the
b-cyclodextrin dye which was used as the
stoichiometry for the inclusion complex of the quinocyanine derived b-cyclodextrin dye and both 1-
Keywords:
Cyanine dye-b-cyclodextrin
Spectral properties
Supramolecular inclusion complex
Spectroscopic probe
1-Adamantanol
adamantanol and vitamin B6 was 1:1, and their inclusion constants were 9.39 ꢀ 104 L/mol and
6.14 ꢀ 102 L/mol, respectively. The quinocyanine derived
b-cyclodextrin dye was also used as the
supramolecular host for the analysis of vitamin B6 in tablets with satisfactory results.
Ó 2012 Elsevier Ltd. All rights reserved.
Vitamin B6
1. Introduction
simultaneously as a supramolecular ligand for CuI and host for aryl
bromides, which could catalyse N-arylation of imidazole with aryl
bromides under mild conditions. Yamada and Hashimoto [21],
Cyanine dyes present typical optical properties and act as one of
the most important organic functional dyes [1,2]. These dyes have
tunable wavelengths across the visible spectrum, and exhibit high
molar extinction coefficients permitting the use of low concentra-
synthesized a water-soluble
then mixed the water-soluble
b
-CD-immobilized poly (allylamine),
-CD derivatives and DNA to form
b
inclusion complexes, which had the potential to absorb harmful
compounds. However, there are no reports concerning the use of
tions [3]. b-cyclodextrin (b-CD), which has both hydrophobic cavity
and hydrophilic surface, is considered as an attractive compound in
the field of molecular recognition [4,5], enzyme mimics [6],
construction of molecular building blocks with ordered nano-
structures [7], commodity [8e11], medicine [12e14] and chemical
cyanine dye modified
probes to recognize colourless guest molecules [22,23].
In this study, six new cyanine dyes- -CD were synthesized
b-CDs as host compounds with spectroscopic
b
(Fig. 1) and characterized. Their UVeVis spectra were investigated
industry [15e17]. However,
in molecular recognition. Therefore, chemically modified
studied extensively. -CD was modified with quinoline to obtain
the biquinolino-bridged bis-cyclodextrin, which included pyro-
ninophilic dye at different pH to study the protonation and
deprotonation of xanthene dyes [18]. Voncina et al. [19], grafted
b
-CD shows poor molecular selectivity
in different solvents. At the same time, the inclusion interaction of
b-CD is
cyanine dye-
(VB6) (Fig. 2(b)) was studied by spectroscopic methods. Previously,
the molecular recognition study on -CD and its modified
b-CD (6) and 1-adamantanol (Fig. 2(a)) or vitamin B6
b
b
analogues with VB6 was done using spectrophotometric titration
by competitive inclusion method using guest molecules with
chromophore or dyes as spectral probes [24,25]. In this work,
synthetic dye-b-CD (6) had its own chromophore and could be used
as a host compound with spectroscopic probe to recognize VB6
without adding other spectral probes. This study describes the use
b
-CD onto PET textile materials, which could be used as odour
carriers or as malodorous absorbers. Suresh and Pitchumani [20],
modified -CD with amino to obtain per-6-amino- -CD, acting
b
b
of dyes-
b-CD as host compounds with spectroscopic probes to
* Corresponding author. Tel.: þ86 29 88302604; fax: þ86 29 88303798.
E-mail address: wanglany@nwu.edu.cn (L.-Y. Wang).
recognize colourless guest molecules.
0143-7208/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.dyepig.2012.08.010

J.-L. Zhao et al. / Dyes and Pigments 96 (2013) 180e188
181
H3CS
N
I
CH3
H3C
N
N
N
CH3
I
I
N
N
CH3
4
TsO
S
H3CS
S
N
CH3
I
2
N
CH3
OH
OTs
N
I
H3CS
H3CS
I
TsCl
CH3
N
N
CH3
6
S
N
CH3
S
I
I
CH3
CH3
N
N
I
N
CH3
N
7
TsO
N CH3
I
N
SCH3
N
3
CH3
8
TsO
NH
OHC
N
N
H
9
Fig. 1. Synthesis of dyes-b-CD.
2. Experimental
were recorded at 400 MHz on a Varian Inova-400 spectrometer and
chemical shifts were reported relative to internal Me4Si. HRMS was
recorded on a microTOFQ II ESI-Q-ToF LC/MS/spectrometer.
2.1. Chemicals and instruments
2.1.1. Chemicals
2.2. Synthesis of cyanine dyes-b-cyclodextrin
Commercially available reagents were used without additional
purification. All solvents were of analytical grade.
2.2.1. Mono-6-oxygen-tosyl-
b-cyclodextrin (1)
Compound (1) was prepared according to the literature [26].
2.1.2. Instruments
Melting points were taken on an XT-4 micromelting apparatus
and uncorrected. IR spectra in cmꢁ1 were recorded on a Bruker
Equiox-55 spectrometer. The absorption spectra were recorded on
a Purkinje General UV-1900 UVeVis spectrometer. 1H NMR spectra
2.2.2. Mono-6-deoxy-6-(2-methylpyridinium)-b-cyclodextrin-p-
toluenesulfonate (2)
Compound (2) was prepared according to the literature [27]. A
mixture of compound (1) (2.70 g, 2.10 mmol) and 2-methyl pyri-
dine (12.0 mL) was stirred at 85 ꢂC for 12 h. After cooling, the
solution was poured into acetone with stirring. The resulting
precipitate was collected and purified with water and acetone
(yield: 87%, m.p. 267e269 ꢂC).
a
b
OH
CH2OH
OH
HOH2C
HCl
2.2.3. Mono-6-deoxy-6-(4-methylpyridinium)-b-cyclodextrin-p-
N
CH3
(VB
toluenesulfonate (3)
Compound (3) was prepared according to the literature [27]. The
same procedure described above but using 4-methyl pyridine
(12.0 mL) (yield: 91%, m.p. 273e275 ꢂC).
1-adamantanol
Vitamin B
6
6
)
Fig. 2. Structures of 1-adamantanol (a) and VB6 (b).

182
J.-L. Zhao et al. / Dyes and Pigments 96 (2013) 180e188
2.2.4. Mono-6-deoxy-6-[2-(1-methyl-2-quinoline methyne)
pyridinium]- -cyclodextrin iodide (4)
from H2O:EtOH (2:1). Pure yellow powder 0.28 g was obtained
b
(yield: 19%), m.p.: >300 ꢂC. UVeVis (MeOH): lmax ¼ 452.0 nm
Compound (2) (1.37 g, 1.00 mmol) and 1-methyl-2-
methylthioquinolinium iodide (0.31 g, 1.02 mmol) were dissolved
in DMF (10.0 mL). Piperidine (0.8 mL) was added as a catalyst. The
reaction mixtures were stirred at 75e80 ꢂC for 5 h. After cooling to
room temperature, the mixtures were poured into acetone under
agitating, causing immediately formation of precipitate. The
resulting precipitate was filtered off, dried and purified by silica gel
chromatography (H2O/EtOH/NH3$H2O, 6:2:2) and then recrystal-
lised from H2O:EtOH (2:1). Pure pink powder 0.25 g was obtained
(yield: 17%), m.p.: >300 ꢂC. UVeVis (MeOH): lmax ¼ 472.0 nm
(1.17 ꢀ 104 L molꢁ1 cmꢁ1). 1H NMR (400 MHz, DMSO-d6):
d
¼ 2.29
(s, 3H, CH3), 3.55e3.47 (m, 59H), 4.08e4.16 (m, 4H), 4.22e4.30 (m,
2H), 4.45e5.35 (m, 4H), 5.02e5.24 (m, 1H, CH]C), 5.91e6.10 (m,
2H, CH2), 7.32e7.64 (m, 4H, PhH), 7.97 (d, 2H, J ¼ 8.0 Hz, pyridine),
8.84 (d, 2H, J ¼ 8.0 Hz, pyridine) ppm. IR (KBr):
y
¼ 3385 (s, yOeH),
2928 (w, yCeH), 1641, 1522 (m, yC]C, yC]N), 1373 (m, dCeH), 1079,
1032 (s, yCeOeC), 945 (w, d]
CH) cmꢁ1. HRMS (TOF MS ES-) calcu-
lated for C56H81N2O34Sþ: 1357.4385; found: 1357.4330.
2.2.8. Mono-6-deoxy-6-[4-(1-methyl-2-pyridine methyne)
pyridinium]-b-cyclodextrin iodide (8)
(2.21 ꢀ 104 L molꢁ1 cmꢁ1). 1H NMR (400 MHz, DMSO-d6):
d
¼ 2.72
(s, 3H, CH3), 2.30e3.95 (m, 41H), 4.31e5.13 (m, 14H), 5.52e5.75 (m,
14H), 6.66 (s, 1H, CH]C), 7.18e7.51 (m, 6H, ArH), 7.91 (d, 2H,
J ¼ 7.6 Hz, pyridine), 8.63 (d, 2H, J ¼ 7.6 Hz, pyridine) ppm. IR (KBr):
The same procedure described above but using 1-methyl-2-
methylthiopyridinium iodide (0.27 g, 1.02 mmol) and stirring at
70e80 ꢂC for 3 h gave crude product, which was purified by silica
gel chromatography (H2O/EtOH/NH3$H2O, 7:2:1) and then recrys-
tallised from H2O:EtOH (2:1). Pure orange red powder 0.54 g was
obtained (yield: 38%), m.p.: >300 ꢂC. UVeVis (MeOH):
lmax ¼ 482.0 nm (1.07 ꢀ 104 L molꢁ1 cmꢁ1). 1H NMR (400 MHz,
y
¼ 3390 (s,
y
ꢁOH), 2926 (s, yCeH), 1652, 1546, 1524 (m,
y
C]C,
CH), 756
CH) cmꢁ1. HRMS (TOF MS ES-) calculated for C58H83N2Oþ34
1351.4822; found: 1351.4777.
yC]N),
1466 (m, dCeH), 1155 (m, yCeN), 1029 (m, yCeOeC), 844 (m,
(m,
d]
d
]
:
D2O):
7.22e7.76 (m, 4H, pyridine), 8.16 (d, 2H, J ¼ 7.4 Hz, pyridine), 8.80
(d, 2H, J ¼ 7.4 Hz, pyridine) ppm. IR (KBr): ¼ 3423 (s, ꢁOH), 2924
(s, yCeH), 1631, 1546, 1523, (m, C]C, C]N), 1476 (m, dCeH), 1157 (m,
d
¼ 2.46 (s, 3H, CH3), 3.40e3.96 (m, 69H), 6.64 (s, 1H, CH]C),
2.2.5. Mono-6-deoxy-6-[2-(3-methyl-2-benzothiazole methyne)
pyridinium]- -cyclodextrin iodide (5)
b
y
y
The same procedure described above but using 3-methyl-2-
methylthiobenzothiazolium iodide (0.33 g, 1.02 mmol) and stir-
ring at 85e90 ꢂC for 5 h gave crude product, which was purified by
silica gel chromatography (H2O/EtOH, 7:3) and then recrystallised
from H2O:EtOH (2:1). A yellow brown powder 0.17 g was obtained
(yield: 11%), m.p.: >300 ꢂC. UVeVis (MeOH): lmax ¼ 450.0 nm
y
y
yCeN), 1030 (m, yCeOeC), 844 (m, d]CH), 785, 755 (m, d] .
CH) cmꢁ1
HRMS (TOF MS ES-) calculated for C58H81N2Oþ34: 1301.4665; found:
1301.4599.
2.2.9. Mono-6-deoxy-6-[4-(3-indole ethenyl) pyridinium]-b-
cyclodextrin-p-toluenesulfonate (9)
(1.74 ꢀ 104 L molꢁ1 cmꢁ1). 1H NMR (400 MHz, DMSO-d6):
d
¼ 2.78
(s, 3H, CH3), 3.55e3.47 (m, 59H), 4.08e4.16 (m, 4H), 4.22e4.30 (m,
2H), 4.45e5.35 (m, 4H), 6.38(s, 1H, CH]C), 7.21e7.38 (m, 4H, PhH),
7.57 (d, 2H, J ¼ 7.6 Hz, pyridine), 7.85 (d, 2H, J ¼ 7.6 Hz, pyridine)
The same procedure described above but using 1H-indole-3-
carboxaldehyde (0.15 g, 1.02 mmol) and stirring at 95e100 ꢂC for
3 h gave crude product, which was purified by silica gel chroma-
tography (H2O/EtOH/NH3$H2O, 6:2:2) and then recrystallised from
H2O:EtOH (2:1). Pure yellow powder 0.24 g was obtained (yield:
ppm. IR (KBr):
(m, C]C,
845 (m,
y
¼ 3420 (s, ꢁOH), 2924 (s, yCeH), 1655, 1600, 1502
y
y
yC]N), 1452 (m, dCeH), 1156 (m, yCeN), 1030 (m, yCeOeC),
d
]
CH), 785, 752 (m,
d
]
CH) cmꢁ1. HRMS (TOF MS ES-)
16%), m.p.: >300 ꢂC. UVeVis (MeOH): lmax
¼
444.0 nm
¼ 3.55e
calculated for C56H81N2O34Sþ: 1357.4385; found: 1357.4352.
(1.24 ꢀ 104 L molꢁ1 cmꢁ1). 1H NMR (400 MHz, DMSO-d6):
d
3.47 (m, 59H), 4.08e4.16 (m, 4H), 4.22e4.30 (m, 2H), 4.45e5.35 (m,
4H), 5.61e6.02 (m, 4H, PhH), 7.17 (d, 2H, J ¼ 16.2 Hz, CH]C), 7.51 (d,
2H, J ¼ 7.8 Hz, pyridine), 8.67e8.74 (m, 3H, two phenyl and one
2.2.6. Mono-6-deoxy-6-[4-(1-methyl-2-quinoline methyne)
pyridinium]-b-cyclodextrin iodide (6)
Compound (3) (1.37 g, 1.00 mmol) and 1-methyl-2-
methylthioquinolinium iodide (0.31 g, 1.02 mmol) were dissolved
in DMF (10.0 mL). Piperidine (0.8 mL) was added as a catalyst. The
reaction mixtures were stirred at 75e80 ꢂC for 3 h. After cooling to
room temperature, the mixtures were poured into acetone under
agitating, causing immediately formation of precipitate. The
resulting precipitate was filtered off, dried and purified by silica gel
chromatography (H2O/EtOH/NH3$H2O, 6:2:2) and then recrystal-
lised from H2O:EtOH (2:1). Pure red powder 0.31 g was obtained
(yield: 21%), m.p.: >300 ꢂC. UVeVis (MeOH): lmax ¼ 484.0 nm
vinylic protons), 9.21 (s, 1H, NH) ppm. IR (KBr):
2924 (s, yCeH), 1656, 1526 (m, yC]C, yC]N), 1451 (m, dCeH), 1157 (m,
y
¼ 3423 (s,
y
ꢁOH),
yCeN), 1030 (m, yCeOeC), 855 (m, d]CH), 755 (m, d]
CH) cmꢁ1. HRMS
(TOF MS ES-) calculated for C57H81N2Oþ34: 1337.4665; found:
1337.4612.
2.3. Determination of absorption spectra of dyes-
b
-CD
The 1 ꢀ 10ꢁ4 M dyes-
b-CD stock solutions were prepared by
dissolving dyes-b-CD in DMSO and further diluted to the appro-
(2.63 ꢀ 104 L molꢁ1 cmꢁ1). 1H NMR (400 MHz, DMSO-d6):
d
¼ 2.64
priate concentration with DMF, DMSO, water, ethanol and meth-
anol, respectively. The absorption spectra were then recorded.
(s, 3H, CH3), 2.30e3.95 (m, 41H), 4.10e5.30 (m, 14H), 5.01 (s, 1H,
CH]C), 5.80e6.35 (m, 14H), 6.63e7.92 (m, 6H, ArH), 7.96 (d, 2H,
J ¼ 7.2 Hz, pyridine), 8.89 (d, 2H, J ¼ 7.2 Hz, pyridine) ppm. IR (KBr):
y
¼ 3442 (s,
y
ꢁOH), 2926 (s, yCeH), 1640, 1567, 1524 (m,
y
C]C,
y
C]N),
2.4. Determination of inclusion constant of the inclusion complex
between dye-b-CD (6) and 1-adamantanol
1456, 1388 (m, dCeH), 1101 (m, yCeN), 1035 (m, yCeOeC), 885 (m,
d]CH), 786, 756 (m, d]
CH) cmꢁ1. HRMS (TOF MS ES-) calculated for
C58H83N2Oþ34: 1351.4822; found: 1351.4757.
In spectral measurements, NaH2PO4eNa2HPO4 buffer solution
(0.1 M, pH ¼ 7.2, methanolewater mixed solvents) was used as the
2.2.7. Mono-6-deoxy-6-[4-(3-methyl-2-benzothiazole methyne)
solvent. The concentration of dye-b-CD (6) was kept constant,
pyridinium]-
b
-cyclodextrin iodide (7)
1.82 ꢀ 10ꢁ5 M. The concentrations of 1-adamantanol were in the
range from 0 M (a) to 8.99 ꢀ 10ꢁ3 M (i). The UVeVis absorption
spectra of these solutions were measured at 300.0e600.0 nm to
evaluate the inclusion constant of the inclusion complex between
The same procedure described above but using 3-methyl-2-
methylthiobenzothiazolium iodide (0.33 g, 1.02 mmol) and stir-
ring at 85e90 ꢂC for 3 h gave crude product, which was purified by
silica gel chromatography (H2O/EtOH, 7:3) and then recrystallised
dye-b-CD (6) and 1-adamantanol.

J.-L. Zhao et al. / Dyes and Pigments 96 (2013) 180e188
183
For a 1:1 stoichiometry, the inclusion complexation of guest 1-
2.5. Determination of inclusion constant of the inclusion complex
between dye- -CD (6) and VB6
adamantanol (G) and host with spectroscopic probe dye-
(H) was expressed by Eq (1).
b-CD (6)
b
NaH2PO4eNa2HPO4 buffer solution (0.1 M, pH ¼ 7.2, distilled
H þ G ¼ HG
(1)
water) was used as the solvent. The concentration of dye-b-CD (6)
was kept constant, 2.70 ꢀ 10ꢁ5 M. The concentrations of VB6 were
in the range from 0 M (a) to 8.00 ꢀ 10ꢁ3 M (j). The UVeVis
absorption intensities of these solutions were measured at
300.0e600.0 nm to evaluate the inclusion constant of the inclusion
Inclusion constant Ks could be expressed in the form of Eq. (2),
where [H]0 and [G]0 were the initial concentrations of H and G; [H],
[G] and [HG] were the equilibrium concentrations of H, G and HG,
respectively.
complex between dye-
b-CD (6) and VB6.
½HGꢃ
½HGꢃ
À
Á
À
Á
Ks
¼
¼
(2)
½Hꢃ ꢀ ½Gꢃ
½Hꢃ0 ꢁ ½HGꢃ ꢀ ½Gꢃ0 ꢁ ½HGꢃ
2.6. Sample preparation
In the experiment, if the concentrations of G and H were kept
Forty pieces of VB6 tablets (10 mg/piece) were crushed into
a powder, and dissolved into distilled water. The sample was
filtered and the filtrate was transferred into a 100 mL volumetric
flask, and diluted to final volume with distilled water to afford stock
solutions.
[G]0 [ [H]0, the extended equation of Eq. (2) was shown below
(Eq. (3)):
½HGꢃ
À
Á
Ks
¼
(3)
½Hꢃ0 ꢁ ½HGꢃ ꢀ ½Gꢃ0
Before the inclusion interaction of G and H, the absorbance
3. Results and discussion
properties of dye-b-CD were shown as follows (Eq. (4)) [28]:
3.1. Synthesis of cyanine dyes-b-CD
A0 ¼ k0½Hꢃ0
(4)
After coordination equilibrium was attained, the absorbance
properties of dye- -CD could be shown below (Eq. (5)):
In all cases investigated, cyanine dyes-
ceeded efficiently. The synthetic conditions of cyanine dyes-
b
-CD formation pro-
b
b
-CD
were listed in Table 1. From reaction temperature it could be found
that the sequence of the reaction activity for mono-6-deoxy-6-(4-
methylpyridinium)-b-cyclodextrin-p-toluenesulfonate (3) and
various 2-methylthio heterocyclic quaternary salts or 1H-indole-3-
carboxaldehyde was 1-methyl-2-methylthiopyridinium iodide z
1-methyl-2-methylthioquinolinium iodide > 3-methyl-2-methy
lthiobenzothiazolium iodide > 1H-indole-3-carboxaldehyde. This
À
Á
A ¼ k0½Hꢃ þ k1½HGꢃ ¼ k0 ½Hꢃ0 ꢁ ½HGꢃ þ k1½HGꢃ
(5)
where k0 and k1 were defined as absorption coefficients. Eq. (4) was
subtracted by Eq. (5), resulting in the following expression (Eq. (6)):
D
A ¼ A0 ꢁ A ¼ ðk0 ꢁ k1Þ½HGꢃ ¼
D
k½HGꢃ
(6)
was because the conjugated degree of the dyes-b-CD formed by
Eq. (6) was substituted into Eq. (3), then BenesieHildebrand Eq.
intermediate (3) and various 2-methylthio heterocyclic quaternary
salts or 1H-indole-3-carboxaldehyde differed from each other. The
larger the conjugated degree was, the more stable the formed dye-
(7) was obtained:
½Hꢃ0
1
1
¼
þ
D
k
(7)
D
A
Ks ꢀ
D
k ꢀ ½Gꢃ0
b
-CD was, according to the Hammond postulate [29,30], the
smaller the activation energy required for forming dye- -CD was,
and the faster the reactive rate was, that is, this reaction occurred
more easily. The donore eacceptor (De eA) conjugated skeleton
-CD (6), (7), (8) and (9) were showed respec-
b
where
D
k
was sensitive coefficient of host’s conformational
A vs 1/
changes during the process of inclusion. By plotting [H]0/
D
p
p
[G]0, a linear relationship could be obtained. Inclusion constant Ks
structures of dyes-
b
could be calculated from the intercept and slope.
tively as follows:
N
C
H
C
H
C
C
H
C
S
C C N CH3
N
N
C
H
C
H
C
C
H
C
C
H
C
H
C C N CH3
(7)
(6) or (8)
C
H
C
C
C
C
H
C
C N H
H
H
H
(9)
Table 1
The synthetic conditions of cyanine dyes-
b
-CD.
Dyes-
b
-CD
Reactant
2
Reaction temperature (ꢂC)
Reaction time (h)
4
5
6
7
8
9
1-methyl-2-methylthioquinolinium iodide
75e80
85e90
75e80
85e90
70e80
95e100
5
5
3
3
3
3
3-methyl-2-methylthiobenzothiazolium iodide
1-methyl-2-methylthioquinolinium iodide
3-methyl-2-methylthiobenzothiazolium iodide
1-methyl-2-methylthiopyridinium iodide
1H-indole-3-carboxaldehyde
3

184
J.-L. Zhao et al. / Dyes and Pigments 96 (2013) 180e188
In the conjugated structure, when the group eSe was bonded to
the De eA framework, there was pe conjugation, and when a e
CH]CHe unit was bonded to the De eA framework, there was
conjugation, and the conjugated degree of was greater than that
of pe . In addition, when the electron-donating group was NMe, the
methyl group exhibited ep hyperconjugation effect through its
p
p
p
pep
pep
p
s
sigma orbit and p orbit of N, thus an NMe could be considered to be
a better donor group than an NH. Therefore the size of the conjugated
degree of dyes-b-CD (6), (7), (8) and (9) was (6) z (8) > (7) > (9), and
the sequence of the reaction activity was 1-methyl-2-
methylthiopyridinium iodide z 1-methyl-2-methylthioquinolinium
iodide
>
3-methyl-2-methylthiobenzothiazolium iodide
>
1H-
indole-3-carboxaldehyde.
The synthetic cyanine dyes-b-CD were not easily purified,
because of their high molecular weight, the presence of several
hydroxyl groups and their association with either small reactant
molecules or solvent molecules. In this paper, the end products
were initially purified according to their differing solubility in
various solvents. The preliminary purification was effected by
precipitation from acetone followed silica gel chromatography.
3.2. UVeVis absorption spectra properties of cyanine dyes-b-CD
The absorption spectra of dyes-
solvents were shown in Fig. 3. It could be seen that the influence of
solvents on the absorption spectra of dye- -CD (7) was different
from that of dyes- -CD (6) and (8). This phenomenon was attrib-
uted to the fact that the De eA structures of these three dyes- -CD
were different. In dyes- -CD (6), (7) and (8), their electron acceptor
was the same, while the electron donor was different. In dye- -CD
(7) the electron donor was a benzothiazole nucleus, but in dyes-
b-CD (6), (7) and (8) in different
b
b
p
b
b
b
b
-
CD (6) and (8) the electron donor was a quinoline and a pyridine
nucleus, respectively, and quinoline and pyridine nucleus had
similar structure and properties. The absorbance properties of
dyes-
Table 2. It could be found that the maximum absorption wave-
lengths (lmax) of the same dye- -CD showed variations in different
solvents. The lmax of the same dye- -CD in aprotic solvent was
b-CD (4)e(9) in different solvents were summarized in
b
b
DMSO > DMF, but the lmax in the protic solvent showed no such
order. The experimental results also revealed that the sequence of
the lmax was (6) z (8) > (4) > (7) > (5) > (9) in the same solvent.
The reason was that the lmax was related to the size of the conju-
gated system of dyes-
dyes- -CD was, the greater the lmax was. Based on the previous
analysis, the size of the conjugated system of dyes- -CD (4)e(9)
was (6) z (8) > (4) > (7) > (5) > (9), leading to the lmax of dyes-
-CD was (6) z (8) > (4) > (7) > (5) > (9) in the same solvent.
b-CD. The greater the conjugated system of
b
b
b
Fig. 3. Absorption spectra of dyes-b-CD (6), (7) and (8) in different solvents.
3.3. The self-inclusion interactions of dye-
b
-CD (6) molecules
-CD, dye- -CD (6) and
Structural model of control dye, control
the self-inclusion interactions of dye- -CD (6) molecules for each
other were represented in Fig. 4. The chemical shifts of partial
protons in control dye, control -CD and dye- -CD (6) in D2O
solvent were summarized in Tables 3 and 4.
From Table 3, we could see that: (i) Chemical shifts of H(c), H(d),
H(e), H(f), H(g), H(h) and H(CH3) in dye- -CD (6) shifted to high
field compared with the control dye. These shifts indicated that the
quinoline ring entered into the cavity of the -CD in dye- -CD (6)
b
b
From Table 4 it could be seen that: (i) H(3) and H(5) in dye-
(6) absorbed at higher field compared with the control -CD. It
further demonstrated that quinoline ring entered into the cavity of
-CD at equator direction, and effected on H(3) and H(5) in dye-
CD (6) molecules, which led to the chemical shifts of H(3) and H(5)
in dye- -CD (6) shifting to higher field. (ii) Chemical shift of H(5) in
dye- -CD (6) changed significantly, which suggested that the
quinoline ring entered deeply into the cavity of -CD, making H(5)
in dye- -CD (6) absorb at higher field. Besides, the carbon chain
between De eA system and -CD in dye- -CD (6) molecules was
short and it was thus impossible for the quinoline ring in dye- -CD
(6) to enter into its own cavity. In other words, dye- -CD (6) had
intermolecular inclusion interaction, and the quinoline ring of one
dye- -CD (6) molecule entered into the cavity of another dye- -CD
(6) molecule.
b-CD
b
b
b
b
b
b-
b
b
b
b
b
b
b
[31]. (ii) The upfield shift was obvious in H(f), H(g), H(h) and
H(CH3), but relatively less in H(c), H(d) and H(e); this feature
p
b
b
b
indicated that the quinoline ring entered into the cavity of
the equator direction, but did not enter vertically into the cavity of
-CD (Fig. 4). H(f), H(g), H(h) and H(CH3) were close to the inner
wall of -CD, so they were affected by protons in the cavity of -CD.
b-CD in
b
b
b
b
b
b

J.-L. Zhao et al. / Dyes and Pigments 96 (2013) 180e188
185
Table 2
Physical properties of solvent, the lmax and
3
of dyes-
b
-CD in different solvents.
Dyes-
b
-CD
Solvent
Dielectric constant
lmax/nm
MeOH
32.63
472.0
2.21
450.0
1.74
484.0
2.63
452.0
1.17
H2O
78.39
463.0
1.75
449.0
1.52
464.0
1.15
453.0
1.15
483.0
0.95
433.0
0.92
EtOH
24.55
461.0
3.96
448.0
1.81
470.0
4.02
451.0
1.12
DMF
37.60
467.0
3.11
448.0
2.51
479.0
3.42
451.0
1.16
484.0
1.15
434.0
1.44
DMSO
48.90
470.0
1.79
450.0
2.15
483.0
1.42
452.0
1.11
485.0
0.91
441.0
1.06
4
5
6
7
8
9
3
ꢀ 10ꢁ4/L molꢁ1 cmꢁ1
lmax/nm
3
ꢀ 10ꢁ4/L molꢁ1 cmꢁ1
lmax/nm
3
ꢀ 10ꢁ4/L molꢁ1 cmꢁ1
lmax/nm
3
ꢀ 10ꢁ4/L molꢁ1 cmꢁ1
lmax/nm
3
482.0
1.07
444.0
1.24
475.0
0.42
449.0
1.25
ꢀ 10ꢁ4/L molꢁ1 cmꢁ1
lmax/nm
3
ꢀ 10ꢁ4/L molꢁ1 cmꢁ1
d
e
c
f
g
H3C N
I
N
CH3
h
Control dye
d
c
e
f
equator
I
g
N
N
CH3
h
Dye-β-CD (6)
Fig. 4. Structural model of control dye, control b-CD, dye-b-CD (6) and the self-inclusion interactions of dye-b-CD (6) molecules.
3.4. Inclusion complexation stoichiometry of dye-
b
-CD (6) with 1-
According to the range of dye-b-CD (6), the plot showed
adamantanol
a maximum at the molar fraction of 0.5, which indicated the
formation of 1:1 inclusion complex.
In order to determine the stoichiometry for the formation of the
inclusion complex of dye- -CD (6) with 1-adamantanol, the
continuous variation method was used. In NaH2PO4eNa2HPO4
buffer solutions (0.1 M, pH 7.2, methanolewater mixed
b
3.5. The inclusion interactions of dye-b-CD (6) and 1-adamantanol
¼
The absorption spectra of dye-
adamantanol were shown in Fig. 6. It could be seen that the lmax
of dye- -CD (6) was not changed with the addition of 1-
adamantanol, and the absorption intensity of dye- -CD (6) was
b-CD (6) in the presence of 1-
solvents), the total concentration of dye-b-CD (6) and 1-
adamantanol was kept constant, 2.0 ꢀ 10ꢁ5 M, and the ratio of
b
the two components was changed continuously. The absorbance
b
difference (
-CD (6) and 1-adamantanol was measured under the same
condition, and the stoichiometry could be obtained by plotting
vs mole fraction of any component. A Job’s plot for the complexa-
DA) between dye-b-CD (6) and miscible liquids of dye-
regularly increased with the increasing concentrations of 1-
adamantanol. The reason was that the chromophoric group of
b
DA
one dye-
b-CD (6) molecule entered into the hydrophobic cavity of
another dye-
b
-CD (6) molecule in the solution of dye- -CD (6).
b
tion of dye-b-CD (6) with 1-adamamtanol was shown in Fig. 5(a).
When 1-adamantanol was added into the solution, the
Table 3
Table 4
Chemical shifts of protons in control dye and dye-
b-CD (6) in D2O solvent.
Chemical shifts of H(3) and H(5) in control
b-CD and dye-
b-CD (6) in D2O solvent.
H(c)
H(d)
H(e)
H(f)
H(g)
H(h)
H(CH3)
H(3)
H(5)
Control dye
7.57
7.56
0.01
7.54
7.53
0.01
7.59
7.53
0.06
7.31
7.18
0.13
7.50
7.19
0.31
7.61
7.51
0.10
3.69
2.86
0.83
Control
Dye-b-CD (6)
Dd
b
-CD
3.96
3.78
0.18
3.84
3.49
0.35
Dye-
b-CD (6)
Dd

186
J.-L. Zhao et al. / Dyes and Pigments 96 (2013) 180e188
40
35
30
25
20
β
15
10
100
200
300
400
500
1/[1-adamantanol]
o
Fig. 7. BenesieHildebrand analyses for the inclusion complexation of dye-b-CD (6)
with 1-adamantanol.
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
a
b
c
d
e
f
g
Fig. 5. Job’s plot of the complexation of dye-b-CD (6) with 1-adamantanol or VB6 in
10ꢁ5 M; (b)
400
450
500
550
600
buffer solution. (a) [6]
þ
[1-adamantanol]
¼
2.00
ꢀ
[6] þ [VB6] ¼ 4.00 ꢀ 10ꢁ5 M.
Wavelength (λ/nm)
Fig. 8. UVeVis spectra of dye-
b
-CD (6) (2.70 ꢀ 10ꢁ5 M) in the presence of VB6 in
NaH2PO4eNa2HPO4 buffer solution (pH ¼ 7.2). The concentrations of VB6: (a) 0 M; (b)
1.00 ꢀ 10ꢁ3 M; (c) 2.00 ꢀ 10ꢁ3 M; (d) 4.50 ꢀ 10ꢁ3 M; (e) 6.00 ꢀ 10ꢁ3 M; (f)
7.00 ꢀ 10ꢁ3 M; (g) 8.00 ꢀ 10ꢁ3 M.
a
b
c
d
e
f
g
h
i
0.50
i
0.45
0.26
0.24
0.22
0.20
0.18
0.16
0.14
0.12
0.10
0.08
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
-0.05
a
400
450
500
550
600
Wavelength (λ/nm)
0.000
0.002
0.004
0.006
0.008
0.010
10ꢁ5 M) in the presence of 1-
[VB6]
Fig. 6. UVeVis spectra of dye-
b
-CD (6) (1.82
ꢀ
adamantanol in NaH2PO4eNa2HPO4 buffer solution (pH ¼ 7.2). The concentrations of
1-adamantanol: (a) 0 M; (b) 1.97 ꢀ 10ꢁ3 M; (c) 2.97 ꢀ 10ꢁ3 M; (d) 3.99 ꢀ 10ꢁ3 M; (e)
5.03 ꢀ 10ꢁ3 M; (f) 6.00 ꢀ 10ꢁ3 M; (g) 7.00 ꢀ 10ꢁ3 M; (h) 8.01 ꢀ 10ꢁ3 M; (i)
8.99 ꢀ 10ꢁ3 M.
Fig. 9. Linear relationship between the concentrations of VB6 (1.00
ꢀ
10ꢁ3
A) in the system of VB6 and dye- -CD
e
9.00 ꢀ 10ꢁ3 M) and the absorbance changes (
D
b
(6) (2.70 ꢀ 10ꢁ5 M).

J.-L. Zhao et al. / Dyes and Pigments 96 (2013) 180e188
187
Table 5
The results of determination of the samples (n ¼ 6).
The absorbance of
the samples (A)
The absorbance changes of
The measured
concentration (mol/L)
The calculated
content (mg/piece)
Relative error (%)
RSD (%)
0.83
the systems (
DA)
0.614
0.620
0.634
0.645
0.652
0.662
0.124
0.130
0.144
0.155
0.162
0.172
2.63 ꢀ 10ꢁ3
2.97 ꢀ 10ꢁ3
3.74 ꢀ 10ꢁ3
4.35 ꢀ 10ꢁ3
4.74 ꢀ 10ꢁ3
5.29 ꢀ 10ꢁ3
9.67
9.59
9.62
9.73
9.81
9.72
ꢁ3.3
ꢁ4.1
ꢁ3.8
ꢁ2.7
ꢁ1.9
ꢁ2.8
chromophoric group of dye-
cavity by 1-adamantanol, on the contrary, the 1-adamantanol
induced the geometric complement between the chromophoric
b
-CD (6) was not replaced out of the
10.00 mg/piece) and the relative standard deviation (RSD) was
0.83% (n ¼ 6). Compared with detection methods reported in the
literature, this method was simple and fast, and could obtain
satisfactory results.
group and the cavity of b-CD [32,33]. Namely, the chromophoric
group was included deeper than in absence of 1-adamantanol.
Thus, the absorption intensities increased regularly.
4. Conclusions
The BenesieHildebrand analyses about the inclusion complex-
ation of dye-
b-CD (6) with 1-adamantanol were shown in Fig. 7. Our
Six new cyanine dyes-
synthetic cyanine dyes- -CD displayed good absorption properties.
The inclusion interactions of dye- -CD (6) as the supramolecular
host with 1-adamantanol or VB6 showed that dye- -CD (6) could
b-CD were designed and synthesized. The
data gave y ¼ 0.0647x þ 6.0746 (R ¼ 0.9972), and according to this
b
formula, the inclusion constant of dye-b-CD (6) and 1-adamantanol
b
was determined to be 9.39 ꢀ 104 L/mol. The result corresponded to
b
the conclusion mentioned above, that is, the ratio of dye-
b-CD (6) to
form a (1:1) inclusion complex with either 1-adamantanol or VB6,
with the inclusion constants of 9.39 ꢀ 104 L/mol and 6.14 ꢀ 102 L/
1-adamantanol was 1:1.
mol, respectively. What is more, dye-b-CD (6) could be applied to
the spectroscopic analysis of VB6 in tablets with satisfactory results.
3.6. Inclusion complexation stoichiometry of dye-b-CD (6) with VB6
In order to determine the stoichiometry for the formation of the
inclusion complex of dye- -CD (6) with VB6, the continuous vari-
Acknowledgement
b
ation method was used. In NaH2PO4eNa2HPO4 buffer solutions
(0.1 M, pH ¼ 7.2, with distilled water as solvent), the total
We appreciate the financial support for this research by a grant
from the Scientific and Technological Research and Development
Projects in Shaanxi Province (2012K07-06), the Special Science
Research Foundation of Education Committee (No. 11JK0558).
concentration of dye-b-CD (6) and VB6 was kept constant,
4.0 ꢀ 10ꢁ5 M, and the ratio of the two components was changed
continuously. The absorbance difference (DA) between dye-b-CD
(6) and miscible liquids of dye-
under the same condition. The stoichiometry could be obtained by
plotting A vs mole fraction of any component. A Job’s plot for the
complexation of dye- -CD (6) with VB6 was shown in Fig. 5(b).
According to the range of dye- -CD (6), the plot showed
b-CD (6) and VB6 was measured
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