Influence of degree of substitution on the host-guest inclusion complex between ionic liquid substituted β-cyclodextrins with 2,4-dichlorophenol: An electrochemical, NMR and molecular docking studies

Article abstract of DOI:10.1016/j.molliq.2019.111334

A mono- and di-substituted ionic liquid-β-cyclodextrin (β-CD-ILs) were synthesized and their host-guest inclusion complex with 2, 4-dichlorophenol (2,4-DCP) were evaluated by electrochemical study. First, both β-CD-ILs which is β-CD-1-BIMOTs and β-CD-2-BIMOTs were fabricated on carbon paste electrode (CPE) for determination of 2,4-DCP. The cyclic voltammetry results indicate that both β-CD-IL/CPEs exhibit higher oxidation peak current compared to native β-CD/CPE. Both complexes possess high sensitivity, stability and reproducibility. However, as the degree of substitution of ionic liquid (IL) increases, the selectivity of β-CD-IL towards 2,4-DCP decreases. Thus, it can be deduced that the degree of substitution of IL is influencing the host-guest inclusion complex of β-CD-ILs with 2,4-DCP.

Full text of DOI:10.1016/j.molliq.2019.111334

Accepted Manuscript
Influence of degree of substitution on the host-guest inclusion
complex between ionic liquid substituted β-cyclodextrins with
2,4-dichlorophenol: An electrochemical, NMR and molecular
docking studies
Fairuz Liyana Mohd Rasdi, Nurul Yani Rahim, Fara Wahida
Hasim, Samikannu Prabu, Khairulazhar Jumbri, Ninie Suhana
Abdul Manan, Sharifah Mohamad
PII:
DOI:
Article Number:
Reference:
S0167-7322(19)32570-X
https://doi.org/10.1016/j.molliq.2019.111334
111334
MOLLIQ 111334
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Journal of Molecular Liquids
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Revised date:
Accepted date:
7 May 2019
24 June 2019
7 July 2019
Please cite this article as: F.L.M. Rasdi, N.Y. Rahim, F.W. Hasim, et al., Influence of
degree of substitution on the host-guest inclusion complex between ionic liquid substituted
β-cyclodextrins with 2,4-dichlorophenol: An electrochemical, NMR and molecular
docking
studies,
Journal
of
Molecular
Liquids,
https://doi.org/10.1016/
j.molliq.2019.111334
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ACCEPTED MANUSCRIPT
Influence of degree of substitution on the host-guest inclusion complex
between ionic liquid substituted β-cyclodextrins with 2,4-dichlorophenol:
An electrochemical, NMR and molecular docking studies.
Fairuz Liyana Mohd Rasdia, Nurul Yani Rahimc, Fara Wahida Hasima, Samikannu Prabu a
Khairulazhar Jumbrid, Ninie Suhana Abdul Manana,b and Sharifah Mohamad a,b*
,
aDepartment of Chemistry, Faculty of Science, University of Malaya, Kuala Lumpur 50603,
Malaysia
bUniversity of Malaya Centre for Ionic Liquids, Department of Chemistry, Faculty of
Science, University of Malaya, Kuala Lumpur 50603, Malaysia
cSchool of Chemical Sciences, University Sains Malaysia, 11800, Pulau Pinang, Malaysia
dDepartment of Fundamental and Applied Sciences, Universiti Teknologi PETRONAS,
32610 Seri Iskandar, Perak, Malaysia.
*Email: sharifahm@um.edu.my
Abstract
A mono- and di-substituted ionic liquid-β-cyclodextrin (β-CD-ILs) were synthesized and
their host-guest inclusion complex with 2, 4-dichlorophenol (2,4-DCP) were evaluated by
electrochemical study. First, both β-CD-ILs which is β-CD-1-BIMOTs and β-CD-2-BIMOTs
were fabricated on carbon paste electrode (CPE) for determination of 2,4-DCP. The cyclic
voltammetry results indicate that both β-CD-IL/CPEs exhibit higher oxidation peak current
compared to native β-CD/CPE. Both complexes possess high sensitivity, stability and
reproducibility. However, as the degree of substitution of ionic liquid (IL) increases, the
selectivity of β-CD-IL towards 2,4-DCP decreases. Thus, it can be deduced that the degree of
substitution of IL is influencing the host-guest inclusion complex of β-CD-ILs with 2,4-DCP.
Key words: Ionic liquid-β-cyclodextrin, 2, 4-dichlorophenol, carbon paste electrode,
inclusion complex, NOESY analysis, Molecular docking
1. Introduction
Chlorophenols are the most common encountered chloroaromatic compounds and
commonly found in many industrial wastewaters [1-2]. These pollutants have detrimental
biological effect such as carcinogenicity, mutagenicity and chronic toxicity [3].
Chlorophenols tends to remain in water or in sediments due to its relatively high-water
solubility and its low air-water partition coefficients [4]. 2,4-dichlorophenol (2,4-DCP) is the
precursor for the production of 2,4-dichlorophenoxyacetate (2,4 DCPA) herbicides and it is
the most abundant chlorophenol in aquatic environment [5]. It was reported that 2, 4-DCP

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have good resistant towards biodegradation and also have ability to be accumulated in living
organisms [6-7]. An investigation on thousand people who is exposed to pesticides shows
that their urine contained 2,4-DCP with the highest percentage of 64% followed by 2,4,5-
trichlorophenol (2,4,5-TCP) (20%) and 12% for (2,4 DCPA) [8]. The in-vivo and in-vitro
studies, 2,4-DCP can modulate the endocrine system [7] including the expression of androgen
[9] and estrogenic receptors [10]. The inhalation of 2,4-DCP was reported to cause
respiratory hazard such as cough, chronic bronchitis, altered pulmonary function as well as
pulmonary lesions [11]. A regular monitoring is necessary prior to removal of 2,4-DCP from
environmental waste water samples.
The various pollutant has been found in different sources and which form inclusion
complex with cyclodextrin especially β-cyclodextrin (β-CD) [12]. The β-CD built up from
seven glucopyranose units bonded through α-1, 4-glycosidic linkage together and form a
toroidal shape with a hydrophobic inner cavity and a hydrophilic outside. Natural and
chemically modified β-CDs can be viewed as molecular receptors. The free hydroxyl at the
primary and secondary face of CDs allow the complexation formation with hydrophobic
compounds in aqueous environments. The complexation of 2, 4-DCP with suitable host allow
the development of analytical technique for its identification and separation. The
introduction of modified β-CD as the component of carbon paste electrode (CPE) create a
recognition site for electrochemical detection of 2, 4-DCP [13]. The β-CD activate the
electrode surface to attract and capture 2,4-DCP into their cavity to form host-guest inclusion
complex. Hence, increase the selectivity and sensitivity of the CPE sensor. The β-CD can
also be functionalized in order to improve both their physical and chemical properties.
In recent years, a few reports have appeared highlighting the synergetic performance
of β-CD and ionic liquid (IL) in sensor applications [13-16]. It has been shown that the
electrochemical properties of both materials are greatly enhanced compared to the individual
component especially for determination of 2,4-DCP. Immobilisation of IL on β-CD is an
alternative to introduce the β-CD-IL on the CPE surface. Ionic liquid generally composed of
organic cations and a corresponding inorganic or organic anion. The unique electrochemical
properties of IL are high ionic conductivity, wide electrochemical window and other than
that, IL act as ion exchanger to increase the analytical signal. The multi-functionality of β-
CD-IL create an improved surface conductivity, larger surface area as well as an enhanced
supramolecular recognition essential especially for 2,4-DCP [13-17].
The hydroxyl group that is located on the upper and lower rims of β-CD can be
substitute to form a variety of β-CD derivatives. The major area of interest is to perform a

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selective chemical modification of the OH- group to influence the complexation properties of
β-CD. The reactivity difference of OH- group between the upper and secondary rims allows
selective functionalization on both rims of β-CD. The three types of hydroxyl groups were
available for modification located at primary rim (C-6 position) and secondary rim (C-2 and
C-3 positions). The substitution of IL at these positions of the β-CD units strongly influence
the chemical and physical properties as well as the enantioselectivity of β-CD [18]. Other
than that, the number of substitutions does give a different effect on the complexation of β-
CD with the guest compound in-term of steric effect and molecular recognition abilities [19].
Tosylated cyclodextrin is generally a good precursor for cyclodextrin derivatives
since tosyl is a good leaving group; especially for modification of primary hydroxyl group
cyclodextrin [20]. Imidazole can easily undergo nucleophilic substitution replacing the tosyl
group and form β-CD functionalized IL complex. The single substitution of benzylimidazole
on primary hydroxyl CD with tosyl group (β-CD-1-BIMOTs) was briefly performed as
discussed by Raoov et al., 2013 [21]. However, there is no preliminary work reported on
higher degree of substitution of benzylimidazole on β-CD. In this study, the ditosylation of β-
CD was carried out in order to perform the substitution of benzylimidazole at two position of
hydroxyl group of β-CD (β-CD-2-BIMOTs). Ditosylation procedure was performed under
aqueous basic condition based on the report by Gonil et al., 2011 [22]. There are two types of
hydroxyl of cyclodextrin which is primary (C6, OH) and secondary (C2, C3, OHs) where the
primary hydroxyl is more reactive than secondary groups. The tosylation of β-CD was first
occurred at the C-6 primary hydroxyl group due to its reactivity, followed by tosylation at
secondary hydroxyl group of β-CD. The nucleophilic displacement of the tosyl group of
ditosylated β-CD form a new derivative of β-CD which is β-CD-2-BIMOTs. In our case, the
mono- and di-substitution of ionic liquid on hydroxyl of β-CD will provide a different
complexation property towards 2,4-DCP. Here in, we report the effect of mono- and di-
substitution of IL on β-CD towards determination of 2,4-DCP in electrochemistry view where
both β-CD-ILs were used as carbon paste electrode modifier. Their interactions were further
investigated by using 1H NMR, NOESY and molecular docking studies.
2. Materials and Methods
2.1. Materials
All chemicals were used of analytical reagent grade. β-cyclodextrin (β-CD), 1-
benzylimidazole (1-BIM), potassium chloride (KCl), potassium ferric cyanide (K3 Fe (CN)6),
paraffin oil and 2,4-dichlorophenol (2,4-DCP) were purchased from Sigma Aldrich.
Ammonium chloride (NH4Cl), sodium hydroxide (NaOH), 4-toluenesulfonyl chloride, 4-

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toluene sulfonic acid, N, N-dimethyl formamide (DMF), methanol (MeOH) and hydrochloric
acid 37% (HCl) were purchased from Merck, while sodium dihydrogen phosphate
(NaH2PO4), disodium hydrogen phosphate (Na2HPO4) and n-hexane were obtained from
Fisher Scientific. Graphite was purchased from HmbG Chemicals. All aqueous solutions
were prepared with ultrapure water (UPW; Milli-Q water purification system, Millipore,
Billerica, MA, USA). All measurements were performed at room temperature.
2.2 Instrumentations
The Fourier Transform Infrared (FT-IR) spectra were recorded on a Perkin-Elmer RX1
FT-IR between 4000 and 400 cm-1 with a resolution of 2 cm-1. EDX analysis was performed
using a scanning electronic microscope (SEM HITACHI SU8220, OXFORD Instruments)
equipped with an energy dispersive X-ray spectrometer. X-ray diffraction (XRD) patterns were
recorded using an Empyrean X-ray diffractometer from 2θ = 15° to 75° using Cu Kα radiation
(λ = 1.5418 Å) at a scan rate of 0.02 s−1. The proton nuclear magnetic resonance (1H NMR)
spectra were recorded on Lambda JOEL 400 MHz FT-NMR spectrometer while the two-
dimensional nuclear overhauser effect spectrpscopy (2D-NOESY) spectrum were recorded
on AVN (600 MHz) and dimethyl sulfoxide (DMSO-D6) had been used as solvent.
Spectrophotometric measurements were made with a Shimadzu Ultraviolet-Visible
spectroscopy UV-1800 (UV-Vis) recording spectrophotometer equipped with 1 cm quartz
cells.
2.3 Synthesis methods
2.3.1 Synthesis of mono- and di- functionalized beta-cyclodextrin precursor (β-CDOTs)
2.3.1.1 Synthesis of 6-monodeoxy-6-tosyl-beta-cyclodextrin precursor (β-CD-1-OTs)
A solution of β-CD (11.5 g, 10 mmol) and p-toluene sulfonic anhydride (Ts2O) in 250
ml of water was stirred at room temperature under an inert atmosphere for 2 hours. A solution
of NaOH (5.0 g in 50 ml of H2O) was added after 2 h. After 10 min, the unreacted Ts2O was
removed by filtration through silica gel. The pH of the filtrate was adjusted to ~8 by the
addition of ammonium chloride. The supernatant solution was removed via filtration and the
resulting white solid was dried under reduced pressure after overnight refrigeration affording
β-CD-1-OTs (1 g, 80%).
IR, cm-1 3279 (OH), 2927 (C-H), 1642 (C=C), 1362 (Assym. SO2), 1167 (SO2 Sym).
1H NMR/ppm, DMSO-D6: H8 (7.75, d), H9 (7.43, d), OH-2-OH-3 (5.62-5.86, m), H1 (4.84,
s), H1* (4.76, s), OH-6 (4.15-4.55, m), H5, H3, H6 (3.38-3.75, m), H4, H2 (3.18-3.34, m),
H11 (2.43, s).

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2.3.1.2 Synthesis of 6-monodeoxy-6-(3-benzylimidazolium)-β-cyclodextrin tosylate (β-
CD-1-BIMOTs)
Dry β-CD-1-OTs (1.00 g, 78 mmol) and benzylimidazole (BIM) (10 molar equiv.) was
dissolved in anhydrous DMF (40 ml). The solution was stirred at 90 °C under nitrogen for 48
hours. Acetone was added after the solution is cool down to room temperature and stirred for
30 min. The precipitate form is filtered and washed once with acetone and dried under
vacuum affording white powdery solid β-CD-1-BIMOTs. A brief pathway is shown in
Scheme 1.
IR, cm-1 IR, cm-1 3290 (OH), 2927 (C-H), 1655 (C=C), 1152 (C-N).
1H NMR/ppm, DMSO-D6: Hf (9.19, s), Hd (8.21, s), He (7.74, s), Hb (7.78, t), Hc (7.74, s),
Ha (7.47, s), H8 (7.40, d), H9 (7.15, d), OH2-OH3 (5.60-5.85, m), Hg (4.93, s), H1 (4.83, s),
OH6 (4.48, m), H6* (3.91, s), H6, H3, H5 (3.5- 3.7, m), H4,H2 (3.2-3.33, m), H11 (2.28,s).
2.3.1.3 Synthesis of 6,3-dideoxy-6,3-ditosyl-beta-cyclodextrin precursor (β-CD-2-OTs)
The β-CD (25g, 22mol) was dissolved in 350 ml of NaOH (10% w/v). After the
overnight storage at 4 °C, p-toluene sulfonyl chloride (10 g, 52 mmol) was added and the
solution was stirred at 0-5 °C in an ice water bath. After 2 hours of vigorous stirring at 0-5
°C, another portion of p-toluene sulfonyl chloride (15 g, 78.5 mmol) was added and stirred
continuously at the same temperature for 3 hours. Later, the unreacted p-toluene sulfonyl
chloride was separated via filtration through Celite on a sintered glass funnel. The filtrate was
brought to pH 1~2 by drop wise addition of hydrochloric acid in an ice water bath. Overnight
refrigeration of the resultant precipitate followed by drying and recrystallization with hot
water led to the isolation of β-CD-2-OTs (as a white powdery solid (6.36 g, 20.02% yield).
IR, cm-1 3304 (OH), 2921 (C-H), 1636 (C=C), 1358 (Assym. SO2), 1167 (SO2 Sym).
1H NMR/ppm, DMSO-D6: H8 (7.74, d), H9 (7.43, d), OH-2-OH-3 (5.63-5.88, m), H1 (4.83,
s) H1* (4.76, s) OH-6 (4.47-4.62, m), H5, H3, H6 (3.51-3.73, m), H4, H2 (3.15-3.45), H11
(2.42, s).
2.3.1.4 Synthesis of 6,3-dideoxy-6,3-(3-benzylimidazolium)-β-cyclodextrin ditosylates (β-
CD-2-BIMOTs)
Fresh dried β-CD-2-OTs (1.00 g, 68 mmol) and BIM (20 molar equiv.) was dissolved
and stirred in anhydrous DMF (60 ml). The stirring was continued at 90 °C under nitrogen for
72 hours. Consequently, the following procedure is the same as reported in section 2.3.1.2 to
afford white powdery solid β-CD-2-BIMOTs. A brief pathway is shown in Scheme 2.
IR, cm-1 3307 (OH), 2931 (C-H), 1659 (C=C), 1154 (C-N).

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1H NMR/ppm, DMSO-D6: Hf (9.19, s), Hd (8.21, s), He (7.95, s), Hb (7.78, t), Hc (7.49, s),
Ha (7.47, s), H8 (7.40, d), H9 (7.15, d), OH2-OH3 (5.60-5.85, m), Hg (4.93, s), H1 (4.83, s),
OH6 (4.48, m), H6* (3.91, s), H6, H3, H5 (3.5- 3.7, m), H4,H2 (3.2-3.33, m), H11 (2.28, s).
2.3.1.5 Synthesis of mono- and di-functionalized ionic liquid beta cyclodextrin tosylate
1
The degree of tolylation (DT) has been determined by H NMR spectroscopy as
shown in Eq. (1).
(1)
Where DT (%) is the degree of tolylation, Ar is the integral area of β-CD aromatic protons at
δ7.8-7.4 ppm, and H1- H6 is the integral areas of the β-CD protons at δ5.9-3.2 ppm. The
synthesis of 6-monodeoxy-6-(3-benzylimidazolium)-β-cyclodextrin tosylate (β-CD-1-
BIMOTs) and the novel di-6,3-dideoxy-6,3-(3-benzylimidazolium)-β-cyclodextrin
ditosylates (β-CD-2-BIMOTs) were accomplished as reported by Raoov et al., 2013 [23].
2.4 Electrochemical studies
The conventional three electrode system used consists of bare CPE, β-CD-1-
BIMOTs/CPE or β-CD-2-BIMOTs/CPE as the working electrode, Ag│AgCl│3 M KCl
(BASi MF2063) as the reference electrode, and Pt wire (BASi model MW-1032) as the
counter electrode. β-CD-1-BIMOTs/CPE and β-CD-2-BIMOTs/CPE were prepared
according to our previous report [17].
2.5 Preparation of solid inclusion complex of 2,4-DCP with β-CD-IL by kneading
method
1 g of β-CD-1-BIMOTs was mixed with ethanol in a mortar and kneaded to form a
paste. After that, an equimolar of 2, 4-DCP (0.1126 g, 6.91 × 10-4 mol) was added and the
kneading process continued for 1 hour and subsequently dried for constant mass affording
white powder precipitate. The preparation of another inclusion complex of β-CD-2-BIMOTs
1
with 2,4-DCP as follow same above. Both complexes were characterized using H NMR and
NOESY.
2.6 Docking studies
The 3D structures of mono- and di-substituted ionic liquid-β-cyclodextrin (β-CD-ILs)
were built by using PyMOL [24] from the native β-CD in which the hydroxyl group at the
primary rim in one of the glucopyranose unit was substituted with imidazole group. Both β-
CD-ILs and phenol derivatives were geometry optimized under density functional theory
(DFT) method using B3LYP/6-31G* basic set. The * accounts for the polarization effect of
the species. The docking procedure was executed by using Auto Dock Tools software version

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1.5.6 [25] where phenol derivatives were introduced into the β-CD-ILs cavity. Lamarkian
Genetic Algorithm (LGA) was applied to identify the possible binding modes of phenol
derivatives with β-CD-ILs through the entire process whereas default values were used for
other setting parameters [26]. A three-dimensional grid box of 50 Å size (x, y, z) with 0.375
Å spacing centered on β-CD-ILs was developed using Autogrid program. Its size was
appropriately designed to sufficiently enclose not only the β-CD-ILs hollow region but also
its exterior part. β-CD-ILs and phenol derivatives were set as rigid macromolecule and
flexible guest molecule, respectively. The interaction energy (ΔGbind) was then calculated by
the following expression:
A total of 10 different conformations with different binding energies were generated. The
conformation that exhibited the lowest ΔGbind energy value and most stable conformation
(obtained from the clustering analysis) was identified as the best binding mode in each
docking study. The 3D model of the docking results was visualized using PyMOL [24].
3 Results and discussion
3.1 Analysis of β-CD-IL
3.1.1 Fourier transforms infrared spectral analysis of β-CD-IL
Fig 1 depicts the FT-IR spectra for β-CD and all the synthesized precursors and β-
CD-ILs. The characteristic wavenumber of β-CD (a) were observed at all spectra which the
OH, C-H and C=C stretching appears approximately at 3291 cm-1, 2924 cm-1 and 1636 cm-1
respectively. The SO2 asymmetric and symmetric peak appeared around 1362 cm-1 and 1167
cm-1 respectively for both β-CD-1-OTs (b) and β-CD-2-OTs (d) proving that the tosylation
successfully take part on β-CD. Further reaction for replacing the tosylate group with
benzylimidazole group resulting the extra C-N peak appear approximately at 1151 cm-1 and
1154 cm-1 for both β-CD-1-BIMOTs (c) and β-CD-2-BIMOTs (e) respectively with the
intensity for asymmetric and symmetric peak of SO2 becoming less observable.
3.1.2 1H Nuclear magnetic resonance spectral analysis of β-CD-IL
1
Fig. S1 shows the H NMR spectra for β-CD (a), β-CD-1-OTs (b) and β-CD-1-
BIMOTs (c) in DMSO-d6 solvent. The mono-tosylation on β-CD can be observed by the
presence of a new resonance at δ= 7.43 ppm (H9) and δ= 7.75 ppm (H8) which belong to the
phenolic group protons of tosyl group. The other resonance is at δ= 2.43 ppm which is stand
for methyl proton of the tosyl group (H11). The degree of tolylation for β-CD-1-OTs was
calculated to be 1.12 which is considered as 1 meaning to say only one tosylation had
occurred on β-CD. As a result of IL functionalization, a new resonance appeared at δ= 4.93

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ppm (Hg) for methyl group proton in between of benzene and imidazole rings. The resonance
for benzyl group protons can be observed at δ= 7.47 ppm (Ha), δ= 7.47 ppm (Hb), δ= 7.78
ppm (Hb) and δ= 7.49 ppm (Hc). The resonance for imidazole protons appears at δ= 8.21
ppm (Hd), δ= 7.95 ppm (He) and δ= 9.19 ppm (Hf).
1
Fig. S2 shows the H NMR spectra of native β-CD, β-CD-2-OTs and β-CD-2-
BIMOTs in DMSO-D6. In Fig. S2(b), there are peaks of tosylate groups at δ = 7.74 and
7.43 ppm and methyl proton (H11) of tosyl group appear at 2.42 ppm. A new peak (H1*) at
δ=4.83 ppm that appeared in β-CD-2-OTs spectrum corresponded to substituted β-CD. The
intensity of the C6-OH peak at δ=4.1-4.6 ppm and C3-OH δ=5.64 ppm is reduced due to the
tosyl substitution at each position. Meanwhile the intensity of C2-OH peak at δ=5.72 ppm is
remained unchanged. This result confirmed the successful of ditosylation of β-CD at C6-OH
and C3-OH. In addition, the degree of tosylation (DT) was calculated to be 1.68 which is >1
that strengthen the occurrence of ditosylation of β-CD backbones.
This result does not meet agreement with the reactivity of hydroxyl group of β-CD
(C6-OH> C2-OH>C3-OH). The C3 secondary hydroxyl group of β-CD is actually less
reactive than the C2 secondary hydroxyl group due to the steric hindrance reason. However,
in our case the second substitution was proven to occur at C3 site instead of C2. Onozuka et
al., 1980 had already explained through his scale molecular model (CPK model) that the C3-
OH become more reactive under alkaline solution compared to the C2-OH which is acidic
[27]. According to the CPK model, tosyl chloride form 1:1 complex inside the β-CD cavity
under alkaline solution. Under this condition, the sulfonyl group of the tosyl chloride is
positioned nearer to both the secondary hydroxyl groups. However, the distance of sulfur is
shorter toward C3-OH compared to C2-OH make it easier to perform a specific
monotosylation on secondary OH via nucleophilic substitution at C3-OH position after the
first tosylation on C6-OH.
1
The H NMR spectrum (Fig. S2 (c)) shows that β-CD-2-BIMOTs was successfully
synthesized. There are protons of imidazole ring appear at downfield region which is Hf
(δ=9.17 ppm, s), Hd (δ=8.21 ppm, s) and He (δ=7.93 ppm, s). The aromatic protons of benzyl
moiety (Ha, Hb, Hc) were observed at δ=7.47, δ=7.76 and δ=7.49 ppm; respectively. The
methyl proton (Hg) that attached to the carbon in between of imidazole and benzene ring
appear in upfield region which at δ=5.3-5.5 ppm. There is a new peak appear at δ=3.99 ppm
corresponds to the proton H6* of the substituted β-CD.

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3.1.3 Energy Dispersive X-Ray spectral analysis of β-CD-IL
Moreover, EDX analysis confirmed the presence of IL and β-CD in the β-CD-1-
BIMOTs (Fig S3 (a)) and β-CD-2-BIMOTs (Fig 4 (b)) with the C, N, O and S signals. The
weight percentage of sulfur (S) content in β-CD-2-BIMOTs is higher (2.03%) than in β-CD-
1-BIMOTs (0.96%). This result proved that β-CD was successfully difunctionalized with IL.
3.1. 4 Powder X-ray diffraction analysis of β-CD-IL
The XRD diffractogram of β-CD-1-BIMOTs and β-CD-2-BIMOTs are demonstrated
in Fig. S4. The XRD pattern of β-CD (a) revealed a series of sharp and intense diffraction
peak especially at 2θ = 9.12°, 10.81°, 12.63°, 13.76° and 18.23° which indicate its crystalline
characteristic and a typical cage-like structure. The XRD profiles for β-CD-1-BIMOTs (b)
and β-CD-2-BIMOTs (c) showed a significant decrease of crystallinity showing that a new β-
CD derivative was successfully formed with some of β-CD characteristic peaks can still be
observed for both compounds. The pattern of both β-CD-1-BIMOTs (b) and β-CD-2-
BIMOTs (c) suggested that these β-CD derivatives are in isomorphous with a channel-type
structure crystal. As the ionic liquid has successfully functionalized on both compounds, the
crystallinity of both compounds decreased. However, it is clearly observed that the
crystallinity of β-CD-2-BIMOTs is reduced compared to β-CD-1-BIMOTs.
3.2 Analysis of inclusion complex in 2,4-DCP with β-CD-IL
3.2.1 Electrochemical studies
The β-CD functionalized IL based electrode surface modification is a promising
simple modification method which attract specific analyte of interest onto carbon paste
material especially 2,4-DCP. The electrochemical oxidation behavior of 2,4-DCP on bare
CPE, β-CD/CPE and β-CD-1-BIMOTs/CPE have been previously reported [17]. According
to our previous study on β-CD-1-BIMOTs/CPE sensor, the presence of IL does improve the
detection of 2, 4-DCP in aqueous solution. In this study β-CD-2-BIMOTs/CPE was prepared
to determine the effect of difunctionalized IL on the oxidation of 2,4-DCP using β-CD-based
as electrode surface. Fig. 2 show the cyclic voltammetric behavior of 50 µmol L-1 2,4-DCP
on CPE (a), β-CD/CPE (b), β-CD-1-BIMOTs/CPE (c) and β-CD-2-BIMOTs/CPE electrode
surfaces yielded one oxidation process in phosphate buffer solution (PBS) pH7.2. On the
reverse sweep, no distinct reduction was observed indicating that 2,4-DCP is irreversibly
oxidized at all electrode surfaces.
The study of pH ranges from 5.8 to 8.0 on the oxidation of 2,4-DCP at β-CD-1-
BIMOTs/CPE and β-CD-2-BIMOTs/CPE electrode surfaces shows that the optimum pH
remains unchanged which is pH7.2. It means that the degree of IL substitution does not affect

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the optimum pH for the oxidation of 2,4-DCP. However, as the number of IL substituted at β-
CD is increased, the optimum oxidation potential of 2,4-DCP is changed drastically. The
effect of degree of IL substitution on the oxidation potential of 2,4-DCP is shown in Fig. 3.
The oxidation potential was reduced from 0.75 V (β-CD-1-BIMOTs/CPE) to 0.68 V (β-CD-
2-BIMOTs/CPE). The presence of IL not only enhance the peak current by accelerating the
electron transfer but also decreasing the overpotential [28]. In this case, as the degree of IL
substitution increases the 2,4-DCP have high tendency to be oxidize at lower potential.
The choroamperometric measurements were employed to evaluate the effect of
potential E (V) on the anodic current response of β-CD-1-BIMOTs/CPE and β-CD-2-
BIMOTs/CPE on the oxidation of 2,4-DCP. The dependency of the current response over the
applied potentials was investigated and studied in the range of 0.60 V to 0.76 V and the
sampling time was 35 s. From amperometric measurement, the current response (I) against
the potential was constructed at 50 ×10-6 mol L-1 2,4-DCP in phosphate buffer solution (PBS,
pH 7.2) and the PBS solution without the analyte as shown in Figure 3. From Figure 3 (a)
and (b), it was shown that the increase of potential had increased the current response of the
PBS solution with or without 2,4-DCP for both electrodes. Hence, the signal to background
(S/B) current ratio was plotted against the potential value to determine the optimal potential
value as shown in Figure 3.
From Figure 3 (c) and (d), we can observe that different number of IL substitution
require a different E (V) value to be able to oxidize the 2, 4-DCP at the modified CPE
electrodes. The dependency of E (V) on number of IL substitution was clear where the one-
position of IL substitution on β-CD required a higher E (V) value compared to that two
positions of IL substitution. According to Sadeghi. et al., the presence of IL did not only
enhance the peak current by accelerating the electron transfer but also involved in decreasing
the overpotential of the electrode (Sadeghi et al., 2013). The result had supported the fact that
IL did possess a crucial role as a component of the electrode. The enhancement of electron
transfer kinetic with the increasing number of IL was closely related to the increase of
electrostatic interaction between 2,4-DCP and the cationic imidazolium part of the electrode
surface (Safavi et al., 2006).
Chrono-amperometric method was performed to investigate the relationship between
the peak current and the concentration of 2,4-DCP under the optimized condition. From
Table 1, the linear range of the detection of 2,4-DCP decreases from 4.3-100 µmolL-1 to

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13.80-100 µmolL-1 as the number of substituted IL on β-CD increases. The electrode
sensitivity was reduced from 0.0060 µmolL-1/µA to 0.0055 µmolL-1/µA. The limit of
detection (LOD) increases from 1.30 to 4.08 µmolL-1 shows that β-CD-1-BIMOTs/CPE is
more sensitive compared to β-CD-2-BIMOTs/CPE in term of determination of 2,4-DCP in
aqueous solution.
Further chrono-amperometric investigation was employed in order to investigate the
performance of both modified electrodes towards 2,4-DCP. The stability and repeatability of
the modified sensors were estimated by repeating test for 50 µmolL-1 of 2,4-DCP in PBS pH
7.2. After 10 consequences days, the measurement value retained >95% for β-CD-1-
BIMOTs/CPE and the β-CD-2-BIMOTs/CPE sensor current measurement retained >97%,
showing that they possess a good long-term stability. For the evaluation of the batch-to-batch
reproducibility, a series of seven electrodes optimum composition were measured. The
coefficient of variation (CV) of amperometric responses of the modified sensors to 2,4-DCP
were 1.40% (β-CD-1-BIMOTs/CPE) and 2.17% (β-CD-2-BIMOTs/CPE). The CVs for intra-
day and inter-day sensing at the same concentration value were measured as 0.92% and
0.89% (n=7) for β-CD-1-BIMOTs/CPE; respectively. For β-CD-2-BIMOTs/CPE, both
measurements were correspondently at 2.51% and 2.17%. This result proves that both sensors
have provided a reasonable precision towards the detection of 2,4-DCP.
The influence of various substances as potentially interfering compounds with the
determination of 2,4-DCP was studied under the optimum conditions with 0.1 PBS
(pH 7.2) containing 100 µmol L-1 2,4-DCP. Some common inorganic anions and some of the
2,4-DCP analog compounds were added to the electrolytes for the evaluation of the
selectivity of this sensor. The tolerance limit must be less than 5% error. From Fig. 4, we
found that both β-CD-1-BIMOTs/CPE (Fig. 4 (a)) and β-CD-2-BIMOTs/CPE (Fig. 4 (b))
were not affected with the foreign ions which is the error for the measurement was less than
5%. The selected analog of 2,4-DCP does not interfere significantly (error less than 5%) for
β-CD-1-BIMOTs/CPE. Different trend was observed in Fig.4 (b) where the graph shows that
the analog of 2,4-DCP which is phenol, 2-chlorophenol (2-CP), 3- chlorophenol (3-CP) and
4-chlorophenol (4-CP) significantly affected the detection of 2,4-DCP. The results show that
β-CD-1-BIMOTs/CPE sensor was selectively suitable for determination of 2,4-DCP
Meanwhile, the β-CD-2-BIMOTs/CPE was not selective towards 2,4-DCP in the presence of
its own analogs. We suggested that the IL does give a significant effect on the selectivity of
the sensor. However, the understanding on how the host-guest interact require another study
on inclusion complex between these β-CD derivatives with 2,4-DCP.

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3.2.2 The pH dependence of the modified electrode response to 2,4-DCP
The effect of pH on the peak current and potential of the oxidation of 2,4-DCP was
investigated between pH 5.8-7.6.for β-CD-1-BIMOTs/CPE and β-CD-2-BIMOTs/CPE using
cyclic voltammetry technique. Figure S5 showed that the direct electrochemistry of β-CD-1-
BIMOTs/CPE and β-CD-2-BIMOTs was strongly dependent on the pH of the electrolyte, the
phosphate buffer solution (PBS). As can be seen in Figure S5 (a) and (b), the peak potential
value of the oxidation of 2,4-DCP was shifted negatively with the increased of the electrolyte
pH from 5.8 to 7.6. However, the peak current reached the maximum value at pH 7.2 for both
β-CD-1-BIMOTs/CPE and β-CD-2-BIMOTs/CPE.
The pH of the solution did affect the existing form of 2,4-DCP. It is known that
dissociation constant (pKa) value for the 2,4-DCP is 7.89. When the pH is less than 7.6, the
2,4-DCP was in its non-dissociated form but at a higher pH value, 2.4-DCP is mainly exist in
the form of ions. When the pH > pKa, the ionized form of 2,4-DCP was dominant and
consequently no proton participated in the reaction. Meanwhile, at a basic pH, a higher
concentration of hydroxyl ions co-exists, which may replace the 2,4-DCP molecules in the
adsorption sites at β-CD-1-BIMOTs/CPE and β-CD-2-BIMOTs/CPE surfaces. Therefore,
based on the evaluation on the anodic peak response of the β-CD-1-BIMOTs/CPE and β-CD-
2-BIMOTs/CPE plotted in Figure S6, pH 7.2 was selected as the optimal pH in the following
experiments.
3.2.3 Linear response, limit of detection (LOD), limit of quantification (LOQ) and
sensitivity of the detection of 2,4-DCP at modified CPEs
Under the optimal condition, the chrono-amperometry measurement was recorded for
different concentration of 2,4-DCP at β-CD-1-BIMOTs/CPE and β-CD-2-BIMOTs/CPE;
respectively (shown in Figure S7). As can be seen in Figure S7 (a) and (b), in all cases, the
peak current increased when 2,4-DCP concentration took place. The calibration curves
obtained for 2,4-DCP indicated a linear relationship ranging from 0 to 100 × 10-6 mol L-1 for
both modified CPEs with a regression of Ip (10-6A) = 0.0044C2,4-DCP + 0.0435 (R2=0.9963)
and Ip (10-6A) = 0.0039C2,4-DCP + 0.1191 (R2=0.9972); respectively for β-CD-1-
BIMOTs/CPE and β-CD-2-BIMOTs/CPE (Figure S8).
From the I against C2,4-DCP graph, the LOD and LOQ for β-CD-1-BIMOTs/CPE
and β-CD-2-BIMOTs/CPE were calculated to determine the selectivity of the modified CPEs.
The LOD, LOQ, linear range and the sensitivity of both modified electrodes were tabulated in

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Table 1. From Table 1, it was shown that the LOD of the oxidation of 2,4-DCP at β-CD-1-
BIMOTs/CPE was 1.3 × 10-6 mol L-1 which was lower than the value obtained at β-CD-2-
BIMOTs/CPE (4.1 × 10-6 mol L-1). As can been in the table, the sensitivity of β-CD-1-
BIMOTs/CPE was 0.0060 µA/ µmol L-1 cm-2, slightly higher than β-CD-2-BIMOTs/CPE,
with 0.0055 µA/ µmol L-1 cm-2. The linear range for β-CD-1-BIMOTs/CPE and β-CD-2-
BIMOTs/CPE were in the range of 4.3 – 100 × 10-6 mol L-1 and 13.8 – 100 × 10-6 mol L-1;
respectively showing that β-CD-1-BIMOTs/CPE offered a better detection of the oxidation of
2,4-DCP.
3.2.4 1 H NMR evaluation of 2,4-DCP with β-CD-ILs.
The 1 H NMR spectra with deduced structures of β-CD-1-BIMOTs, β-CD-2-BIMOTs,
2,4-DCP and the complexes are shown in Fig. 5 (a) and (b). The values of the chemical
shifts (δ) for different protons in β-CD-1-BIMOTs, β-CD-2-BIMOTs, 2,4-DCP and inclusion
complexes are listed in Table 2 (a) and (b); respectively. According to Yuan et al. (2012), the
inclusion complex occurs when the chemical shift at H-3 and H-5 proton located inside the β-
CD cavity is change drastically [29]. The spectra (Fig. 5 (a)) and data (Table 2 (a)) shows
higher ∆δ at H3 and H5 interior proton of β-CD-1-BIMOTs-2,4-DCP. Meanwhile there are
small changes of the chemical shift at the exterior proton of H-1, H-2 and H-4 which is
considered as negligible changes. There also incorporation of the phenolic rings into β-CD-1-
BIMOTs resulted from the strong intensity of ∆δ at Hb-p and Hc-p protons of 2,4-DCP. The
data obtained was in a good term with our previous study on β-CD-1-BIMOTs-2,4-DCP [13].
Based on our NOESY spectrum from previous study, the strong changes on β-CD-1-BIMOTs
protons (H-3, H-5) and 2,4-DCP phenolic protons (Hb-p and Hc-p) proved that 2,4-DCP was
successfully incorporated into the cavity of β-CD-1-BIMOTs. The phenomena can be
explained as the formation of an inclusion complex is occurred between β-CD-1-BIMOTs
and 2,4-DCP.
However, the interaction between β-CD-2-BIMOTs and 2,4-DCP for the formation of
β-CD-2-BIMOTs-2,4-DCP complex is slightly varied compared to interaction involved for
formation of β-CD-1-BIMOTs-2,4-DCP complex. The ∆δ of H3 and H5 interior proton of β-
CD-2-BIMOTs-2,4-DCP complex (Table 2 (b)) is insignificant. Meanwhile, the exterior
proton of β-CD-2-BIMOTs-2,4-DCP complex; H2 and H4 shows a significantly stronger ∆δ
which is 0.0187 and 0.0157; respectively. This result shows that 2,4-DCP might have
interaction at the outer cavity of the β-CD-2-BIMOTs. This result is strengthened by the
NOESY analysis (Fig.6) which show the strong intensity of cross peaks for exterior proton of

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β-CD-2-BIMOTs (3.31-3.38 ppm, H2, H4) and 2,4-DCP (6.96-7.20 ppm, Hb-p, Hc-p) but no
correlation peak for the interior proton of β-CD-2-BIMOTs (H3, H5). Hence, we can
conclude that the phenolic ring of 2,4-DCP does not accommodated into β-CD-2-BIMOTs
cavity but prefer to interact at exterior part of β-CD-2-BIMOTs.
3.2.5 Molecular docking analysis
In order to rationalize the NMR experimental results described above, we carried out
molecular docking studies of the complexes. From docking simulation shown in Figure 7 &8
for complex of β-CD-1-BIMOTs-2,4-DCP, there are three different binding orientations (A-,
B- and C-orientations) between β-CD-1-BIMOTs and 2,4-DCP. The lowest interaction
energy which is -4.25 kcal/mol in A-orientation obtained for stable docking conformation.
2,4-DCP is found to trap inside the cavity complexes due to Van der Waals and electrostatic
interaction. This indicated that the functionalization of an IL molecule at C6 position located
at the narrow rim of the cavity is unaffecting for the inclusion complex formation. In
addition, atom O44 in β-CD-1-BIMOTs is able forming hydrogen bonding with atom H from
2,4-DCP to form inclusion complexation.
The penetration of a guest molecules into the hydrophobic cavity can be occur either
from primary or secondary face of β-CD depending on the size and the nature of the guest. A
molecular modeling study that was reported by Ming-Ju Huang et. al (1997) shows that
phenol hydroxyl group prefers to face the secondary rim of the β-CD cavity [30]. From our
investigation, we found that the H6 proton of the β-cyclodextrin of both β-CD-1-BIMOTs
and β-CD-2-BIMOTs does not affected upon the formation of the complexes. This
phenomenon strongly suggesting that the incorporation of 2,4-DCP might occurred at the
wider side of the cavity.
The schematic diagram for the formation of β-CD-2-BIMOTs-2,4-DCP and β-CD-2-
BIMOTs-2,4-DCP were depicted in Fig. 9. The analyte which is 2,4-DCP can easily inserted
into the cavity through the wider rim and form β-CD-2-BIMOTs-2,4-DCP complex. The
benzylimidazolium group that located at C-6 position does not affecting the formation of the
complex since it located at the narrow rim of the cavity. The second functionalization of
benzylimidazolium was located at the C-3 position at the wider rim of the cavity entrance.
Both parts do interact with 2,4-DCP through π-π interactions. However, the presence of the
ionic liquid at the secondary face might have hindered the insertion of the 2, 4-DCP resulting
the interaction between β-CD-2-BIMOTs and 2,4-DCP occurs more outside the cavity than
inside it.

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The difference between these two materials is that the main forces of the complexation of β-
CD-1-BIMOTs-2,4-DCP is governed by a strong hydrophobic and π-π interaction while only
the weak π-π interaction was applied for β-CD-2-BIMOTs-2,4-DCP. In addition, Table 3
showed the binding energy of the β-CD-1-BIMOTs and β-CD-2-BIMOTs complexes with
2,4-DCP and its analogs such as 4-CP, 3-CP, 2-CP and phenol obtained from molecular
docking. The lowest binding energy exhibit strongest interaction between host and guest. β-
CD-1-BIMOTs attained the lowest binding energy (-4.25 kcal/mol) with 2,4-DCP. The
selectivity of β-CD-1-BIMOTs and β-CD-2-BIMOTs toward 2,4-DCP and its analogs is
cause by the forces of interactions involve in the formation of complexes. β-CD-1-BIMOTs is
believed to have a strong hydrophobic and π-π interactions with 2,4-DCP. Meanwhile, β-CD-
2-BIMOTs-2,4-DCP complex is governed by the weak π-π interaction. This result indicated
that β-CD-1-BIMOTs is the most selective interaction to 2,4-DCP compared to β-CD-2-
BIMOTs.
This phenomenon helps to explain why β-CD-2-BIMOTs host does not show a
selective detection towards the 2,4-DCP in the presence of its analogous as discussed in
Section 4.1 (Fig.4) compared to β-CD-1-BIMOTs. According to Radi and Eissa (2010), a
more stable complex will form with those guests who can fit better inside the cavity of
cyclodextrin [31]. Since the 2,4-DCP had interacted more with outside cavity of β-CD-2-
BIMOTs as well as with the aromatic ring of the ionic liquid by a weak π-π interaction, the
same kind of interaction might happen to other analogous as well resulting a non-selective
phenomenon to occur.
4. Conclusion
The complexation ability of the β-CD is utilized well in electrode modification for
sensing applications especially for detection of phenolic compound; specifically, 2,4-DCP.
The ionic liquid functionalization does influence the directionality of the β-CD host-guest
complexation at the same time provide greater sensing ability compared to native β-CD
modified sensor. We conclude that the number of IL substitutions does significantly affecting
the sensing process however it is strongly depending on the positioning of the substituted IL
on β-CD.

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Acknowledgements
The authors acknowledge, with thanks the following: UMRG Projects (RP020-16SUS and
RP011B-14SUS), PPP grant: PG050-2014B from University of Malaya and the Ministry of
Education Malaysia for My-Brain (My-PhD) scholarship given to a student named Fairuz
Liyana Mohd Rasdi (SHC140048).
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Scheme 1: Synthesis pathway for β-CD-1-BIMOTs
Scheme 2: Synthesis pathway for β-CD-2-BIMOTs
Figure 1. Fourier transforms infra-red spectra of (a) β-CD, (b) β-CD-1-OTs (c) β-CD-1-
BIMOTs, (d) β-CD-2-OTs (e) β-CD-2-BIMOTs.
Figure. 2 Cyclic voltammetry for the oxidation of 2,4-DCP at CPE (a), β-CD/CPE (b), β-CD-
1-BIMOTs/CPE (c) and β-CD-2-BIMOTs/CPE electrode surfaces.
Figure. 3 Hydrodynamic voltammogram of 50 × 10-6 mol L-1 2,4-DCP (signal) and PBS
without analyte (background) at pH 7.2 at a 35 s sampling time for (a) β-CD-1-BIMOTs/CPE
and (b) β-CD-2-BIMOTs/CPE; respectively. The hydrodynamic voltammogram of signal-to-
background current ratio (S/B) is simplified in (c) β-CD-1-BIMOTs/CPE and (d) β-CD-2-
BIMOTs/CPE; respectively
Figure.4 The influence of some possible interfering substances on the determination of
50 µmol L-1 2,4-DCP in PBS at pH 7.2. β-CD-1-BIMOTs/CPE (a) and β-CD-2-BIMOTs/CPE
(b).
1
Figure. 5 (a): H-NMR spectrum of β-CD-1-BIMOTs, 2,4-DCP and β-CD-1-BIMOTs-2,4-
DCP complex.
1
Figure. 5 (b): H-NMR spectrum of β-CD-2-BIMOTs, 2,4-DCP and β-CD-2-BIMOTs-2,4-
DCP complex.
Figure. 6 The two-dimensional NOESY spectrum of β-CD-2-BIMOTs-2,4-DCP complex in
DMSO-D6.
Figure. 7 Complex structure of β-CD-1-BIMOTs-2,4-DCP in three different binding
orientations with lowest interaction energy from molecular docking
Figure. 8 Complex structure of β-CD-2-BIMOTs-2,4-DCP in three different binding
orientations with lowest interaction energy from molecular docking
Figure. 9 Schematic diagrams on interaction between β-CD-1-BIMOTs: 2,4-DCP (a), β-CD-
2-BIMOTs: 2,4-DCP (b)

ACCEPTED MANUSCRIPT
Table 1: LOD, LOQ, linear range and sensitivity of modified electrodes.
LOD
LOQ
Linear range
Sensitivity
Electrodes
β-CD-1-BIMOTs/CPE
β-CD-2-BIMOTs/CPE
1.3
4.1
4.3
4.3 - 100
13.8 - 100
0.0060
0.0055
13.8

ACCEPTED MANUSCRIPT
Table 2 (a): Chemical shift (δ) of β-CD-1-BIMOTs, 2,4-DCP and β-CD-1-BIMOTs-2,4-
DCP
Proton
β-CD-1-
BIMOTs
2,4-
DCP
β-CD-1-
BIMOTs-2,4-
DCP
Changes
δ
δ
δ
∆δ
H1
H2
H3
H4
H5
H6
H8
H9
H11
Ha
4.8204
3.3100
3.6046
3.3453
3.5864
3.6350
7.3990
7.1200
2.0726
7.4734
7.7280
7.4862
8.1920
7.9300
9.1636
5.3886
4.8222
3.3123
3.6186
3.3445
3.5704
3.6324
7.4060
7.1244
2.0744
7.4732
7.7317
7.4942
8.2002
7.9272
9.1713
5.3910
7.4270
6.9478
7.1895
0.0018
0.0020
0.0140
-0.0008
0.0160
-0.0026
0.0070
0.0045
0.0018
0.0002
0.0037
0.0080
0.0405
0.0028
0.0077
0.0025
0.0260
0.0103
0.0141
Hb
Hc
Hd
He
Hf
Hg
Hap
Hbp
Hcp
7.4011
6.9515
7.1754

ACCEPTED MANUSCRIPT
Table 2 (b): Chemical shift (δ) of β-CD-2-BIMOTs, 2,4-DCP and β-CD-2-BIMOTs-2,4-
DCP
Proton
β-CD-2-
BIMOTs
δ
2,4-DCP
β-CD-2-BIMOTs-2,4-
DCP
Changes
δ
δ
∆δ
H1
H2
H3
H4
H5
H6
H8
H9
H11
Ha
4.8181
3.2950
3.6197
3.3972
3.5939
3.6197
7.3956
7.1210
2.0739
7.4776
7.7259
7.4901
8.1663
7.9274
9.1551
5.3845
4.8223
3.3137
3.6212
3.3815
3.5881
3.6212
7.4211
7.1223
2.0740
7.4768
7.7318
7.4902
8.1509
7.9270
9.1717
5.4042
7.4211
6.9609
7.1913
0.0043
0.0187
-0.0015
0.0157
-0.0058
0.0015
0.0255
0.0013
0.0001
-0.0008
0.0059
0.0001
-0.0154
-0.0004
0.0166
0.0198
0.0201
0.0092
0.0159
Hb
Hc
Hd
He
Hf
Hg
Hap
Hbp
Hcp
7.4011
6.9515
7.1754

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Table 3: Stoichiometry ratio and binding constant for β-CD-1-BIMOTs and β-CD-2-
BIMOTs with 2,4-DCP inclusion complexes.
Stoichiometry
ratio
Binding energy,
(kcal/mol)
Complexes
β-CD-1-BIMOTs-2,4-DCP
β-CD-1-BIMOTs-4-CP
β-CD-1-BIMOTs-3-CP
β-CD-1-BIMOTs-2-CP
β-CD-1-BIMOTs-Phenol
β-CD-2-BIMOTs-2,4-DCP
β-CD-2-BIMOTs-4-CP
β-CD-2-BIMOTs-3-CP
β-CD-2-BIMOTs-2-CP
β-CD-2-BIMOTs-Phenol
1:1
1:1
1:1
1:1
1:1
1:1
1:1
1:1
1:1
1:1
-4.25
-3.76
-3.86
-3.90
-3.20
-3.37
-3.08
-2.97
-2.92
-2.59
β-CD-1-BIMOTs
complexes
β-CD-2-BIMOTs
complexes

ACCEPTED MANUSCRIPT
Research Highlights
 β-CD-IL/CPE exhibits higher oxidation peak current in cyclic voltammetry compared to
β-CD/CPE.
 Increase degree of substitution of IL, decreases the selectivity of β-CD-IL towards 2,4-
DCP
 Degree of substitution of IL is influencing the host-guest inclusion complex of β-CD-ILs
with 2,4-DCP.

Figure 1

Figure 2

Figure 3

Figure 4