Studies on Absorption and Emission Characteristics of Inclusion Complexes of Some 4-Arylidenamino-5-phenyl-4H-1, 2, 4-triazole-3-thiols

Article abstract of DOI:10.1007/s10895-015-1728-5

The inclusion complexes of a series of 4-arylidenamino-5-phenyl-4H-1, 2, 4-triazole-3-thiols have been prepared with β-cyclodextrin. The compounds and their inclusion complexes have been characterized by studying their physical and spectral properties. Th

Full text of DOI:10.1007/s10895-015-1728-5

J Fluoresc (2016) 26:413–425
DOI 10.1007/s10895-015-1728-5
ORIGINAL ARTICLE
Studies on Absorption and Emission Characteristics of Inclusion
Complexes of Some 4-Arylidenamino-5-phenyl-4H-1, 2,
4-triazole-3-thiols
Sunakar Panda1 & Sashikanta Nayak1
Received: 6 September 2015 /Accepted: 16 November 2015 /Published online: 21 November 2015
#
Springer Science+Business Media New York 2015
Abstract The inclusion complexes of a series of 4-
arylidenamino-5-phenyl-4H-1, 2, 4-triazole-3-thiols have
been prepared with β-cyclodextrin. The compounds and their
inclusion complexes have been characterized by studying
their physical and spectral properties. The thermodynamic
stability constant and free energy of activation have been de-
termined to know the stability of inclusion complexes and
type of host-guest relation. Finally, absorption, excitation
and emission spectra of the compounds (4-arylidenamino-5-
phenyl-4H-1, 2, 4-triazole-3-thiols) and their inclusion com-
plexes have been taken. It is found that inclusion complex
formation brings about a drastic change in absorption and
fluorescence characteristic (both excitation and emission
spectra) of newly synthesized compounds.
exitation and emission spectra as well as quantum yields,
can be heavily influenced by environmental variables. In fact,
the high degree of sensitivity in fluorescence is primarily due
to interactions that occur in the local environment during the
excited state life time [1–7].
The drugs containing 1, 2, 4-triazole nucleus are reported to
exhibit a wide spectrum of pharmacological activities like
antimicrobial [8–12], anticancer [13, 14], antiviral [15],
anti-inflammatory [16], analgesic [17], anticonvulsant [18]
etc. It is known that the formation of inclusion complex of
drug molecules with β –cyclodextrin improves their solubili-
ty, stability as well as bioavailability [19–24]. But transference
of drug molecules which are usually nonpolar in nature, in to
hydrophobic core of β –cyclodextrin causes a drastic change
in its microenvironment. Since the spectral chacteristics of
molecules depend upon the molecular structure and its micro-
environment [6, 7] such a transference will definitely have
some impact on fluorescence characteristics of the molecules.
In view of these facts, an attempt has been made to synthe-
size some 4-arylidenamino −5-phenyl-4 H-1,2,4-triazole-3-
thiol (Schiff bases) in their purest forms and prepare their
inclusion complexes with β-cyclodextrin. The absorption,
excitation and emission spectra of the compounds and
their inclusion complexes are taken to examine whether
the inclusion complex formation has any impact on
absoption and emission characteristics of 4-arylidenamino-5-
phenyl-4H-1, 2, 4-triazole-3-thiols.
.
.
Keywords Triazole-3-thiol Inclusion complex Absorption
.
.
spectra Excitation spectra Emission spectra
Introduction
Fluorescence characteristics of fluorophores depend upon a
number of environmental factors including interactions be-
tween the fluorophore and surrounding solvent molecules
(dictated by solvent polarity), other dissolved inorganic and
organic compounds, temperature, pH, and the localized con-
centration of the fluorescent species. The effects of these pa-
rameters vary widely from one fluorophore to another. The
Experimental
* Sunakar Panda
sunakar_panda@yahoo.com
Materials and Methods
1
All the chemicals used in the present work were procured
from local market. Double distilled water was used as solvent.
P.G. Department of Chemistry, Berhampur University,
Bhanjabihar, Odisha 760007, India

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J Fluoresc (2016) 26:413–425
Scheme 1 A: 4-Benzilidenamino −5-phenyl-4H-1, 2, 4-triazole-3-thiol.
B: 4-[2-Nitrobenzilidenamino] -5-phenyl-4 H-1,2,4-triazole-3-thiol. C:
4-[4-Bromobenylideneamino] -5-phenyl-4H-1, 2, 4-triazole-3-thiol. D:
4-[4-Methoxybenylideneamino] -5-phenyl-4H-1, 2, 4-triazole-3-thiol.
E: 4-[2-Hydroxybenzylideneamino] -5-phenyl-4H-1, 2, 4-triazole-3-
thiol. F: 4-[(furan-2-yl)methyleneamino] -5-phenyl-4H-1, 2, 4-triazole-
3-thiol
1.6
Fig. 1 Phase solubility study of
the synthesized compounds in
aqueous solution of β-
cyclodextrin
Comp-A
Comp-B
Comp-C
Comp-D
Comp-E
Comp-F
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
0.001
0.002
0.003
0.004
0.005
0.006
Conc. of β-Cyclodextrin

J Fluoresc (2016) 26:413–425
415
The elemental analysis was performed in a CHN analyzer.
Melting points were recorded by open capillary method.
Absorption spectra were recorded in Shimadzu UV-1800
spectrophotometer and IR spectra were recorded in KBr
pellets in Shimadzu 8400 FT-IR spectrophotometer. 1HNMR
spectra were obtained with Brukers spectrophotometer model
ultra-shield at 300 MHz in DMSO- d6 solution with TMS as
internal standard. The purity of the newly synthesized com-
pounds were checked by TLC. Fluorescence emission and
excitation spectra were recordedy in a Shimadzu RF-1501
spectrofluorimeter equipped with a150W xenon lamp. The
synthesis of the titled compounds A, B, C, D, E and F
were carried out as per Panda et al. 2015 [24] as shown
in Scheme 1.
bance versus inverse concentration of β-cyclodextrin using
Benesi-Hilderband relation [27].
1=ΔA ¼ 1=Δε þ 1=K0 :Δε½GuestŠo:½β − CDŠ
where ΔA is change in absorbance, Δε is change in
absorption coefficient, K is stability constant, [Guest]o is
the concentration of compound and [β-CD] is the concen-
tration of β-cyclodextrin. The values of K for all the
complexes are calculated using the relation
K ¼ Intercept=Slope
The value of ΔG at 298 K was calculated using the
equation:
ΔG ¼ −RTlnK
Phase Solubility Measurements
The aqueous phase solubility of the compounds at various
concentrations of β –cyclodextrin (0-10 mM) was studied
by Higuchi-Conner method [25].
Results and Discussion
Synthesis of Inclusion Complexes
Six different 4-arylidenamino −5-phenyl-4 H-1, 2,
4-triazole-3-thiols (A, B, C, D, E and F) have been synthe-
sized (as shown in scheme 1) in their purest forms. The
inclusion complexes of A, B, C, D, E and F have been
prepared with β-cyclodextrin (β-CD) after determining the
optimum concentration of host and guest through aqueous
phase solubility study (Fig. 1). The structures of the com-
pounds (A, B, C, D, E and F) have been confirmed from the
study of their physical properties, elemental composition,
Co-precipitation method was used for the preparation of
inclusion complexes of the compounds with β-cyclodextrin
[22, 26].
Study of Thermodynamic Properties
The thermodynamic stability constants of the complexes
were calculated from plot of inverse of change in absor-
1
FT-IR and HNMR data (Tables 1 and 2). The elemental
Table 1 Some physical properties of the synthesized compounds and their inclusion complexes
Sl No.
1
Compound/Complex
Molecular formula
C15H12N4S
Molecular weight
280. 35
Colour
M.P. (°C)
Yield(%)
Compound- A
I.C.A
Light brown
white
180–185
272–274
170–172
282–285
178–180
275–280
160–162
280–285
145–148
278–280
170–175
281–283
73
75
72
74
77
77
71
77
71
75
73
77
2
3
4
5
6
Compound- B
I.C.B
C15H11N5O2S
C15H11 BrN4S
C16H14N4OS
C15H12ON4S
C13H10N4OS
325.35
359.24
310. 37
296.35
270. 31
Pale yellow
Dull white
Light yelllow
white
Compound- C
I.C.C
Compound- D
I.C.D
Dull White
white
Compound- E
I.C.E
Dull white
white
Compound- F
I.C.F
Dark gray
white

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Table 2 Spectral data and elemental composition of the compounds and their inclusion complexes
Sl No. Compound/ IR (KBr) cm−1rcase
name Complexcase
NMR(DMSO-d6)
Elemental Analysis Calculated (Found)
C
H
N
1
2
3
4
A
968.27 (N-C-S str), 3034.03, 3099.61,
(Ar-H str),1498.69(C = Cstr)696.38
(C-S str), 1350.17 (C-N str)0.1610.56
(C = Nstr)
937.4 (N-C-S str), 2931.80 (Ar-H str),
1409.96(C = Cstr)756.10 (C-S str),
1332.81 (C-N str)0.1656.85(C = Nstr),
3398.57(OHstr, β-CD),2931.80
(C-Hstr, β-CD)
7.52–7.90 (m, 10 H,
Ar-H),14.25(s, 1 H, SH),
9.70(s, 1 H, N = CH).
64.26 (64.46) 4.31 (4.02) 19.98 (19.92)
55.37 (55.27) 3.41 (3.32) 21.53 (21.50)
50.15 (50.19) 03.09 (3.14) 15.60 (15.51)
61.92 (61.95) 04.55 (4.52) 18.05 (18.01)
I.C.A
7.32–7.91 (m, 10 H,
Ar-H),3.35(s,1 H,β-CD),
3.43(s,1 H,β-CD),
3.45(s,1 H,β-CD),
3.57(s,1 H,β-CD),
3.59(s,1 H,β-CD)
B
943.27 (N-C-S str), 3115.04 (Ar-H str),
696.30(C-S str), 1498.69(C = Cstr)
1342.46 (C-N str). 1529.55,1342.46
(NO2), 1610(C = Nstr)
937.40(N-C-S str), 2933.80(Ar-H str),
1409.96(C = Cstr)704.02(C-S str),
1361.74 (C-N str)0.1409.96 (NO2),
1658.78(C = Nstr), 3367.71(OHstr,
β-CD),2931.80(C-Hstr, β-CD)
7.53–8.34(m, 9 H, ArH),
14.304 (s, 1 H, SH),10.499
(s, 1 H, N = CH).)
I.C.B
7.92–8.13 (m, 9 H,
Ar-H),3.37(s,1 H,β-CD),
3.61(s,1 H,β-CD),
3.63(s,1 H,β-CD),
3.64(s,1 H,β-CD),
3.66(s,1 H,β-CD),
7.54–7.89 (m, 9 H, Ar-H),
C
968.27 (N-C-S str), 2941.44, 3113.11
(Ar-H str),1500.62 (C = Cstr)684.73
(C-S str), 1355.96 (C-N str)0.1510.56
(C = Nstr)609.51(C-Br)
937.40 (N-C-S str), 2931.80 (Ar-H str),
1409.96(C = Cstr)756.10 (C-S str),
1332.81 (C-N str)0.1658.78(C = Nstr),
3385.07(OHstr, β-CD), 2931.80
(C-Hstr, β-CD), 613.36(C-Br)
I.C.C
7.36–7.96 (m, 9 H,
Ar-H),3.35(s,1 H,β-CD),
3.42(s,1 H,β-CD),
3.46(s,1 H,β-CD),
3.54(s,1 H,β-CD),
3.58(s,1 H,β-CD)
7.04–8.62 (m, 9 H, Ar-H),
3.82–3.85(s, 3 H, OCH3)
D
943.19(N-C-S str), 3076.46,3115.04
(Ar-H str), 1500.62(C = Cstr)696.30
(C-S str), 1352.10(C-N str), 1598.99
(C = Nstr)
I.C.D
937.40(N-C-S str), 2931.80, (Ar-H str),
1409.96(C = Cstr) 1658.78(C = Nstr),
756.10 (C-S str), 1332.81,(C-N str)
0.3371.57(OHstr, β-CD),2912.51
(C-Hstr, β-CD)
7.94–8.78(m, 9 H, Ar-H),
3.32(s,1 H,β-CD),
3.34(s,1 H,β-CD),
3.37(s,1 H,β-CD),
3.61(s,1 H,β-CD),
3.64(s,1 H,β-CD), 2.73–2.89
(s, 3 H, OCH3
5
E
941.26 (N-C-S str), 2951.09, 2993.52
(Ar-H str), 1446.61(C = Cstr), 696.30
(C-S str), 1350.17 (C-N str), 3134.33
(ArOH), 1610.56(C = Nstr)
7.49–7.88 (m, 9 H, Ar-H),
8.98 (s, 1 H, OH)
60.79 (60.84) 4.08 (4.12) 18.91 (18.93)
I.C.E
937.40 (N-C-S str), 2931.80 (Ar-H str),
1409.96(C = Cstr)756.10(C-S str),
1361.74 (C-N str),1658.78(C = Nstr)
3365.78(OHstr, β-CD), 3226.91(Ar-OH),
3236.55, 3294.42(C-Hstr, β-CD)
7.94–8.28 (m, 9 H,
Ar-H),3.34(s,1 H,β-CD),
3.54(s,1 H,β-CD),
3.57(s,1 H,β-CD),
3.62(s,1 H,β-CD),
4.46(s,1 H,β-CD)
6
F
941.26 (N-C-S str), 3099.61, 3134.33
(Ar-H str), 1571.99, (C = Cstr)
696.30(C-S str), 1350.17 (C-N str).
1610.56 (C = Nstr)
6.78–8.06(m, 8 H, ArH),
57.76 (57.64) 03.73 (3.76) 20.73 (20.70)
I.C.F
937.40(N-C-S str), 2931.80, (Ar-H str),
1656.85(C = Cstr)705.95 (C-S str),
1361.74 (C-N str). 1653.00 (C = Nstr),
3290.56.71(OHstr, β-CD),3167.12
(C-Hstr, β-CD)
7.95–8.23 (m, 8 H,
Ar-H),3.31(s,1 H,β-CD),
3.35(s,1 H,β-CD),
3.55(s,1 H,β-CD),
3.63(s,1 H,β-CD),
3.66(s,1 H,β-CD)

J Fluoresc (2016) 26:413–425
417
Fig. 2 Plot of inverse absorbance
against inverse concentration of
β-cyclodextrin
4.0
3.8
3.6
3.4
3.2
3.0
2.8
2.6
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
Comp-A
Intercept 1.36182
Comp-A
Comp-B
Comp-C
Comp-D
Comp-E
Comp-F
Slope
0.00176
Comp-B
Intercept 0.74706
Slope
0.00109
Comp-C
Intercept 0.89917
Slope
0.00111
Comp-D
Intercept 0.35279
Slope
0.00181
Comp-E
Intercept 1.83569
Slope
0.00209
Comp-F
Intercept 0.66704
Slope 0.00202
200
400
600
800
1000
1/Conc. of β-cyclodextrin
composition of the compounds matches with theoretical data
(Table 2). The FT-IR and H NMR data of the compounds
The aqueous phase-solubility diagrams of the compounds
with β-cyclodextrin are shown in Fig. 1. It is seen that aque-
ous solubility of the compounds increases linearly as a func-
tion of the concentration of β-cyclodextrin up to 5th point
followed by a decline. This clearly indicates that the concen-
tration at 5th point is the optimum concentration for inclusion
complex formation. The plot of inverse change in absorbance
against inverse concentration of β-cyclodextrin gives straight
lines with definite slope and intercept for different compounds
(Fig. 2). The thermodynamic stability constants (K) have been
calculated from the slope and intercept [27] and are found to
be in the range of 194.91 to 878.32 (Table 3). Since all the
values are remaining within ideal range [28] all the inclusion
complexes formed are quite stable. Further, it is found that the
values of all the slopes are less than one indicating the inclu-
sion complexes to have 1:1 stoichiometry [21–23]. Negative
1
confirm the expected structures. The preparation of inclusion
complexes of the compounds have been confirmed from the
1
changes in melting point, colour and FT-IR and H NMR
spectral characteristics (Tables 1 and 2). The IR- stretching
frequencies due to different bonds undergo downward shift
towards lower energy and the peaks become broader, weaker
1
and smoother. The H NMR signals due to different protons
undergo smaller shifts (small shift towards down field in
case of all the compounds) after their inclusion complex
formations. The changes in IR spectral characteristics may
be attributed to the restriction on the compounds for under-
going vibration within the cavity of β-CD due to the devel-
opment of weak interaction like H-bonding, vander-Waal
forces and hydrophobic interactions etc. [22]. This observa-
tion clearly demonstrates transference of the compound from
a more protic environment (aqueous media) to a less protic
environment (cavity of β-CD). The compound and β-CD
interaction leading to inclusion complex formation is further
Table 4 Absorption, exitation and emission peak positon of the
compounds and their inclusion complexes
1
Sl. No. Compound/
Complex
Absorption Exitation peak Emission peak
maximum position λ (nm) position λ (nm)
Max(nm)
supported by H NMR data (Table 2). The changes in the
microenvironment of the compound after encapsulation may
λ
1
cause a small shift in H NMR signals.
1
2
3
4
5
6
Compound- A 294
I.C.A 270
Compound- B 295
I.C.B 275
Compound- C 295
I.C.C 270
Compound- D 294
I.C.D 278
Compound- E 294
I.C.E 265
Compound- F 292
I.C.F 287
299
295
313
286
326
307
307
294
294
283
316
303
448
445
451
437
453
433
451
445
449
439
452
439
Table 3 Thermodynamic stability constant and free energy change of
inclusion complexes
Sl.No. Inclusion complex Thermodynamic stability ΔG (kJ/mol)
Constant (M−1
)
1
2
3
4
5
6
I.C.A
I.C.B
I.C.C
I.C.D
I.C.E
I.C.F
773.76
685.37
810.06
194.91
878.32
330.21
−16.478
−16.178
−16.592
−13.063
−16.793
−14.369

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0.700
0.600
-------------------------------------Beta Cyclodextrin
---------------------Comp-A
0.400
0.200
0.000
------------------------------------------------------ I.C.A
230.00
250.00
300.00
Wavelength (nm.)
350.00
400.00
Fig. 3 UV spectrum of β- cyclodextrin, compound A and its inclusion compex
0.700
-------------------------------------Beta Cyclodextrin
0.600
---------------------Comp-B
0.400
0.200
0.000
------------------------------------------------------ I.C.B
230.00
250.00
300.00
Wavelength (nm.)
350.00
400.00
Fig. 4 UV spectrum of β- cyclodextrin, compound B and its inclusion compex

J Fluoresc (2016) 26:413–425
419
0.700
-------------------------------------Beta Cyclodextrin
0.600
0.400
0.200
0.000
---------------------Comp-C
------------------------------------ I.C.C
350.00
230.00
250.00
300.00
400.00
Wavelength (nm.)
Fig. 5 UV spectrum of β- cyclodextrin, compound C and its inclusion compex
0.700
-------------------------------------Beta Cyclodextrin
0.600
0.400
0.200
0.000
---------------------Comp-D
------------------------------------ I.C.D
230.00
250.00
300.00
Wavelength (nm.)
350.00
400.00
Fig. 6 UV spectrum of β- cyclodextrin, compound D and its inclusion compex

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0.700
0.600
-------------------------------------Beta Cyclodextrin
0.400
0.200
0.000
---------------------Comp-E
--------------------------------- I.C.E
350.00
230.00
250.00
300.00
400.00
Wavelength (nm.)
Fig. 7 UV spectrum of β- cyclodextrin, compound E and its inclusion compex
0.700
-------------------------------------Beta Cyclodextrin
0.600
0.400
0.200
0.000
---------------------Comp-F
--------------------I.C.F
230.00
250.00
300.00
Wavelength (nm. )
350.00
400.00
Fig. 8 UV spectrum of β- cyclodextrin, compound F and its inclusion compex

J Fluoresc (2016) 26:413–425
421
500
400
300
200
100
0
ECITATION
Comp-A
I.C.A
200
250
300
350
400
450
500
550
600
Wavelength (nm)
500
400
300
200
100
0
EMISSION
Comp-A
I.C.A
200
250
300
350
400
450
500
550
600
Wavelength (nm)
Fig. 9 Excitation and emission spectra of compound A and its inclusion comlex
500
400
ECITATION
300
200
100
0
Comp-B
I.C.B
200
600
250
300
350
400
450
500
550
Wavelength (nm)
500
400
300
200
100
0
EMISSION
Comp-B
I.C.B
200
600
250
300
350
400
450
500
550
Wavelength (nm)
Fig. 10 Excitation and emission spectra of compound B and its inclusion comlex

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600
500
400
300
200
100
0
EXCITATION
Comp-C
I.C.C
200
600
250
300
350
400
450
500
550
Wavelength (nm)
600
500
400
300
200
100
0
EMISSION
Comp-C
I.C.C
200
250
300
350
400
450
500
550
600
Wavelength (nm)
Fig. 11 Excitation and emission spectra of compound C and its inclusion comlex
600
EXCITATION
500
400
300
200
100
0
I.C.D
Comp-D
200
600
250
300
350
400
450
500
550
Wavelength (nm)
600
500
400
300
200
100
0
EMISSION
I.C.C
Comp-D
200
600
250
300
350
400
450
500
550
Wavelength (nm)
Fig. 12 Excitation and emission spectra of compound D and its inclusion comlex

J Fluoresc (2016) 26:413–425
423
500
400
300
200
100
0
EXCITATION
Comp-E
I.C.E
200
600
250
300
350
400
450
500
550
Wavelength (nm)
500
400
300
200
100
0
EMISSION
Comp-E
I.C.E
200
250
300
350
400
450
500
550
600
Wavelength (nm)
Fig. 13 Excitation and emission spectra of compound E and its inclusion comlex
500
EXITATIONC
400
300
200
100
0
I.C.F
Comp-F
600
200
250
300
350
400
450
500
550
Wavelength (nm)
500
400
300
200
100
0
EMISSION
I.C.F
Comp-F
600
200
250
300
350
400
450
500
550
Wavelength (nm)
Fig. 14 Excitation and emission spectra of compound F and its inclusion comlex

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and properties of new substituted 1,2,4-triazoles: potential antitu-
mor agents. Bioorg Med Chem 11: 1701–1708
15. Abdel-Aal MT, El-Sayed WA, El-Kosy SM, El-Ashry ESH
(2008) Synthesis and antiviral evaluation of novel 5-(N-
arylaminomethyl-1,3,4-oxadiazol-2-yl)hydrazines and their
sugars,1,2,4-triazoles, tetrazoles and pyrazolyl derivatives. Arch
Pharm 341(5):307–313
values of free energy changes for all the inclusion complexes
(Table 3) further suggest that the process of inclusion complex
formation is spontaneous and thermodynamically allowed.
It is interesting to note that the absorption and emission
characterestics of all the compounds (A, B, C, D, E and F)
undergo drastic changes after their inclusion complex forma-
tion. The absorption maxima shifts towards lower wavelength
(Table 4)and the intensity of the peaks becomes higher after
their inclusion complex formation (Figs. 3, 4, 5, 6, 7, and 8).
However, although the excitation and emission peaks shift
towards lower wavelength, the intensity of the peaks be-
comes lower after their inclusion complex formation
(Figs. 9, 10, 11, 12, 13, and 14). The shifting of absorp-
tion and excitation peak positions may be due to the fact
that more amount of energy is required for the compounds
for their excitation after encapsulation because the mole-
cules get stabilized within the cavity of β-cyclodextrin
through some weak intermolecular forces. The lowering
of fluorescence intensity may be due to lesser population
of molecules in the excited state than ground state.
16. Labanauskas L, Udrenaite E, Gaidelis P, Brukstus A (2004)
Synthesis of 5-(2-,3- and 4-methoxyphenyl)-4 H-1,2,4-triazole-3-
thiol derivatives exhibiting anti-inflammatory activity. IlFarmaco
59(4):255–259
17. Labanauskas L, Kalcas V, Uderenaite E, Gaidelis P, Brukstus A,
Dauksas V (2001) Synthesis of 3-(3,4-dimethoxyphenyl)-1 H-1,2,
4-triazole-5-thiol and 2-amino-5-(3,4-dimethoxyphenyl)-1,3,4-
thiadiazole derivatives exhibiting anti-inflammatory activity.
Pharmazie 56:617–619
Conclusion
The above results established the fact that the inclusion com-
plexes of the synthesized compounds alter the absorption and
emission characteristics of the molecules.
18. Almasirad SA, Tabatabai M (2004) Synthesis and anticonvulsant
activity of new 2-substituted-5-[2-(2-fluorophenoxy) phenyl]-1,3,
4-oxadiazoles and 1,2,4-triazoles. Bioorg Med Chem Lett 14(24):
6057–6059
19. Yang B, Lin J, Chen Y, Liu Y (2009) Artemether/hydroxypropyl-b-
cyclodextrin host-guest system: characterization, phase-solubility
and inclusion mode. Bioorg Med Chem 17:6311–6317
20. Panda S, Sahu R (2013) Studies on inclusion complex of 3-
(2-chloro phenyl) 4-methyl 2- thiocarbamoyl-3,3a-dihydro
pyrazolo[3,4c] pyrazole. Am J Adv Drug Deliv 1(5):1–9
21. Panda S, Sahu R (2014) Studies on inclusion complex of 4-methyl-
3-phenyl-2- thiocarbamoyl-3,3a-dihydro pyrazolo[3,4c] pyrazole. J
Pharm Bio Sci 9(2):30–36
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