Indole - based distinctive chemosensors for 'naked-eye' detection of CN- and HSO4-, associated with hydrogen-bonded complex and their DFT study

Article abstract of DOI:10.1080/10610278.2015.1092534

Colorimetric detection of anions (HSO₄^- and CN^-) was achieved via analyte triggered colour changing of the dipodal and tripodal sensors in CH₃CN-H₂O (1:1). The sensors exhibited very sharp visual colo

Full text of DOI:10.1080/10610278.2015.1092534

Supramolecular Chemistry
ISSN: 1061-0278 (Print) 1029-0478 (Online) Journal homepage: http://www.tandfonline.com/loi/gsch20
Indole-based distinctive chemosensors for ‘naked-
−
eye’ detection of CN and HSO4 , associated with
hydrogen-bonded complex and their DFT study
Dibyendu Sain, Chanda Kumari, Ashish Kumar & Swapan Dey
To cite this article: Dibyendu Sain, Chanda Kumari, Ashish Kumar & Swapan Dey (2015):
−
Indole-based distinctive chemosensors for ‘naked-eye’ detection of CN and HSO4 , associated
with hydrogen-bonded complex and their DFT study, Supramolecular Chemistry, DOI:
10.1080/10610278.2015.1092534
To link to this article: http://dx.doi.org/10.1080/10610278.2015.1092534
View supplementary material
Published online: 11 Nov 2015.
Submit your article to this journal
Article views: 7
View related articles
View Crossmark data
Full Terms & Conditions of access and use can be found at
http://www.tandfonline.com/action/journalInformation?journalCode=gsch20
Download by: [Karolinska Institutet, University Library]
Date: 16 November 2015, At: 21:10

Supramolecular chemiStry, 2015
http://dx.doi.org/10.1080/10610278.2015.1092534
−
Indole-based distinctive chemosensors for ‘naked-eye’ detection of CN− and HSO4 ,
associated with hydrogen-bonded complex and their DFT study
Dibyendu Sain, Chanda Kumari, Ashish Kumar and Swapan Dey
Department of applied chemistry, indian School of mines, Dhanbad, india
ARTICLE HISTORY
received 3 June 2015
accepted 6 September 2015
ABSTRACT
−
Colorimetric detection of anions (HSO4 and CN−) was achieved via analyte triggered colour changing
of the dipodal and tripodal sensors in CH3CN–H2O (1:1). The sensors exhibited very sharp visual colour
−
changes and fluorescence quenching–enhancing effect upon addition of the HSO4 and CN−. The large
downfield shift of the NH proton signals in 1H-NMR complexation studies and quantum chemical DFT
calculations proved the formation of hydrogen-bonded complexes where no proton transfer mechanism
was found.
KEYWORDS
Dipodal and tripodal
receptors; indole;
chemosensors; CN− and
HSO4 − ions
Introduction
limited numbers of fluorescent‘on-off’sensors (4, 5) and some
reviews (6) have been focused for the detection of the CN−
ion through the hydrogen bonding interaction. Indeed, the
development of easy and selective detectors for the cyanide
ion is a great chance with simple chemosensors.
Selective detection and sensing of hydrogen sulfate
(HSO4−) ion is an active research area as it is used in various
fertilizers, industrial raw materials, nuclear fuel waste and it
The exposure on colorimetric sensors for identifying ani-
ons through hydrogen bonding interaction is an emerg-
ing research area (1). The anions have various fatal effects
for human, mammals, aquatic life and the environment (2).
The cyanide ion (CN−) is considered as the most toxic ion for
human body among all anions, as it binds Fe3+ of the haem
unit and inhibits the oxygen supply in our body (3). Recently,
CONTACT Swapan Dey
© 2015 taylor & Francis
dey.s.ac@ismdhanbad.ac.in

2
D. SAIN eT Al.
N
H
Indole
(iii)
(ii)
(i)
N
HN
N
N
H
H
N
N
N
N
H
H
H
H
Receptor 2
Receptor 3
Receptor 1
Scheme 1. (colour online) Reagents and conditions: (i) p-dimethylaminobenzaldehyde, Bi(No3)3·5h2o, dry ethanol, r.t., 6 h., 80% yield, (ii)
9-anthracenecarboxaldehyde, Bi(No3)3·5h2o, dry ethanol, r.t., 6 h., 85% yield, (iii) indole-3-carbaldehyde, Bi(No3)3·5h2o, dry ethanol, r.t., 6 h., 90% yield.
also has a number of adverse effects as an environmental pol-
lutant (7). At higher pH, the HSO4− ion dissociates to generate
poisonous sulfate ion (SO42−) which leads to diarrhoea, irri-
tation of skin and eyes and respiratory paralysis (8). Till date,
Reaction procedure for the synthesis of receptors
(R1–R3)
R1 and R2 were synthesised by the condensation reaction of
indole with N,N-dimethylaminobenzaldehyde and 9-anthra-
cenecarboxaldehyde, respectively. The reactions were carried
out in the presence of 0.1 equivalent bismuth nitrate pen-
tahydrate as a catalyst in dry ethanol solvent. To prepare R3,
the indole-3-carbaldehyde was first obtained from indole by
Vilsmeier–Haack reaction using DMF and POCl3 (15). Finally,
the aldehyde was condensed with indole itself to produce R3
(reaction Scheme 1).
−
only a few fluorogenic chemosensors for sensing the HSO4
have been reported so far (9). So, the development of chem-
osensors for selective,‘naked-eye’detection of the sulfate and
hydrogen sulfate ions has attracted considerable attention
as simple and cost-effective methods (10). Among the other
techniques used for the detection of anions, fluorescence‘on-
off’technique has been fascinated much attention due to its
high sensitivity (11).
In this present context, we report two indole-based
dipodal (R1 and R2) and one tripodal (R3) chemosen-
sors for selective colorimetric sensing of HSO4− and CN−
ions in CH3CN–H2O (1:1). Herein, the indole moiety has
been used as a binding site for the hydrogen bonding
as well as a basic fluorophore unit (12). earlier, Wei et al.
have described the comparative study of anion sensing
ability of the methyl substituted R3, where it did not
show any spectral response to anions in CH3CN only (13).
However, in continuation of our research (14), we inves-
tigated the complexation studies for all the receptors
in semi-aqueous medium (CH3CN–H2O, 1:1, v/v), where
the receptors exhibit very sharp visual colour change
and a fluorescence quenching–enhancing effect upon
Result and discussion
All the receptors (R1–R3) were characterised by FTIR, 1H-NMR,
13C-NMR and mass spectroscopic techniques. Only for R3, we
obtained a single crystal to determine the geometry of the
molecule in the solid state.
Single-crystal X-ray analysis of R3
The isothermal diffusion technique was followed to find out
a good single crystal of R3 using methanol (10%) in chloro-
form. The crystal was monoclinic in molecular setting with P
21/c space group and there were eight molecules present in
a unit cell (Z = 8). The crystal structure of R3 showed that the
indole moieties were connected to the central sp3 carbon (C1)
atom to form a tripod structure, where the three N–H groups
were far apart from each other (Figure 1(a)). In addition, one
R3 molecule was associated with the others by several short
contacts in all directions to form a supramolecular network.
The most important short contact was found among the NH
−
addition of HSO4 and CN− selectively over other ani-
ons. Interestingly, no proton transfer incident from sen-
sors to anions was observed under complexation but
hydrogen-bonded complex formation was obviously
established in 1H-NMR study. Quantum chemical DFT
calculations displayed the actual binding and interac-
tions involved in the recognition process.

SuPRAMOleCulAR CHeMISTRy
3
Figure 1. (colour online) (a) ortep diagram of R3 and (b) crystal packing diagram of R3 in a unit cell (ccDc No. 868517).
−
group (N3−H013) and six aromatic carbon atoms (C41–C46)
(Figure 1(b)). The different short contacts and the crystallo-
graphic data were summarised in electronic Supplementary
Information (eSI), Tables S1 and S2.
(Figure 2(c) inset) upon addition of 1.0 equivalent HSO4 and
consequently, became colourless by adding 3.0 equivalents
CN− ion (Figure 2(d) inset). However, the receptor solutions
did not exhibit any interesting response by adding large
−
amounts of other anions like F−, Cl−, Br−, I−, AcO− and H2PO4
even up to 10.0 equivalents (see ESI, Figures S1, S6 and S10).
Absorption of R1 (c = 5.47 × 10−4 M) was recorded using
uV–vis spectroscopy and it showed two peaks at λmax = 535
and 465 nm. It was also noticed that at lower concentration
(2.52 × 10−5 M) an extra peak at λmax = 252 nm was attributed
to the indole ring with very high absorbance value (see ESI,
Figure S2). The sharp decrease in absorbance was observed
only by the addition of nBu4N+CN− into the solution of R1.
The absorbance at 535 nm decreased rapidly and the peak
vanished finally, which resulted pale yellow (almost colour-
less) solution (Figure 2(a)). In case of R2 (c = 1.89 × 10−4 M),
it was seen that the receptor itself showed three absorp-
tion maxima at λmax = 352, 370 and 391 nm. With the grad-
Complexation studies of the receptors with different
anions through visual detection, UV–vis and
fluorescence spectroscopy techniques
The sensing ability of the receptors was investigated with a
−
series of anions ([nBu4 N]+X−, X = F−, Cl−, Br−, I−, CN−, AcO−, HSO4
−
and H2PO4 ) in CH3CN–H2O (1:1, v/v). R1 (c = 1.09 × 10−3 M)
changed its colour from deep red to pale yellow only upon
addition of 2.0 equivalent CN− ion (Figure 2(a) inset), whereas
R2 (c = 1.13 × 10−3 M) turned to pink colour from colourless
−
upon addition of 1.0 equivalent HSO4 (Figure 2(b) inset).
On the other hand, R3 (c = 1.25 × 10−3 M) instantly changed
its colour (without taking time) from yellow to orange red

4
D. SAIN eT Al.
Figure 2. (colour online) uV–vis titration spectra of (a) R1 with cN−, (b) R2 with hSo4−, (c) R3 with HSO4− and (d) R3 with CN− in ch3cN–h2o
(1:1, v/v) (inset: visual colour change).
−
ual addition of HSO4 ion, the absorbance at 352, 370 and
391 nm decreased regularly along with an increase in a new
absorption peak at λmax = 513 nm (Figure 2(b)). This change
was associated with the appearance of one isosbestic point
at 420 nm, indicating the complex formation. On the other
hand, R3 (c = 1.11 × 10−4 M) itself exhibited an absorption
maximum at λmax = 283 nm, along with a secondary peak
at 466 nm. In the presence of HSO4−, the intensity of the
absorbance at 283 nm decreased regularly along with increas-
ing intensity of a new absorption band at λmax = 483 nm
(Figure 2(c)). The formation of one isosbestic point at 307 nm
was found to support the complex formation. In contrast,
the peak intensity at 466 nm decreased by the addition of
CN− to make R3 solution colourless along with the regular
decrease in intensity of the peak at 283 nm (Figure 2(d)). High
polarisability over the H–N bonds of the receptors generated
by the approach of the anions with the NH group of indole
moieties through hydrogen bond formation. As a result, the
energy of the benzene ring of the indole moiety moved to
the N centres, which promoted the π-electron circulation in
the indole moieties, causing considerable colour change and
higher binding affinity for anions (16). The complexation pro-
cess was occurring mainly due to hydrogen bond formation,
not for deprotonation process. This phenomenon was also
established by the anion sensing study of the receptor (R3)
with strong base like tetrabutylammonium hydroxide. No
colour change as well as λmax shifting in uV–vis experiment
was observed accordingly (see ESI, Figure S11).
For further investigation of solvatochromic effect, the
uV–vis absorption study of R3 was carried out in different
solvents of different polarities, where it was observed that
no characteristic peak was found in low polarity solvent like
n-hexane and toluene (due to very low solubility) and the
peak position of R3 remained quite same (λmax 274–283 nm)
in high polarity solvent like DCM, chloroform, methanol,
acetonitrile, DMF, DMSO and CH3CN–H2O (1:1, v/v) (see ESI,
Figure S12).
The complexation studies of the receptors with the ani-
ons were also carried out by the fluorescence spectroscopic
analysis in CH3CN–H2O (1:1, v/v). When R1 (2.52 × 10−5 M) was
excited at λmax 252 nm, the corresponding emission spectrum
was found at λmax 360 nm. The regular decrease in the peak
intensity, i.e. fluorescence quenching was observed upon
addition of CN− ion (Figure 3(a)). The calculated limit of detec-
tion (lOD) (17) of R1 for sensing of CN− was 2.03 × 10−8 M (see
ESI). Corresponding emission peak of R2 (c = 1.42 × 10−5 M) was
found at 535 nm (λexc = 391 nm) with regular enhancement of
−
the fluorescence intensity for HSO4 anion (0–3.0 equivalents)
(Figure 3(b)) and R2 can sense HSO4− up to the 1.98 × 10−8
M
identified through lOD calculation. On exciting the solution

SuPRAMOleCulAR CHeMISTRy
5
−
Figure 3. ((colour online) a) Fluorescence titration spectra of (a) R1 with CN− (λex = 252 nm), (b) R2 with HSO4− (λex = 391 nm), (c) R3 with HSO4
(λex = 283 nm) and (d) R3 with CN− (λex = 283 nm) in ch3cN–h2o (1:1, v/v).
Figure 4. (colour online) probable complex structures of R1:CN−, R2:HSO4−, R3:HSO4− and R3:CN−.
of R3 (c = 2.2 × 10−6 M) at λmax 283 nm, an emission spectrum
with peak maxima at 360 nm was recorded and substantial
quenching of the fluorescence intensity was observed with
compared to π–π* state of the receptors, resulting a consid-
erable decrease in the fluorescence emission intensity (18).
For the calculation of binding isotherm using uV–vis and
fluorescence, the titration data were plotted as a function of
[G]/[H] vs ΔI. It was observed that the curve after [G]/[H] = 2.0
tended to be parallel to X-axis and a break point of slope of
the titration curve implied 1:2 stoichiometry between R1 and
CN− (see ESI, Figure S3), whereas 1:1 stoichiometry was found
for R2 and R3 with HSO4− (see ESI, Figures S7 and S13). The
slope of the titration curve of R3 with CN− pointed out the
breakpoint after [G]/[H] = 3, indicating 1:3 stoichiometry (see
ESI, Figure S12). In addition, the Job’s plot (19) (XH vs ΔI. XH,
where XH = mole fraction of the host, ΔI = Change in inten-
−
the gradual addition of both HSO4 and CN− anion (0–3.0
equivalents, Figure 3(c) and (d)). The lOD calculation showed
−
that R3 recognise HSO4 and CN− anions up to 2 × 10−8
M
concentration (see ESI). Previously, a probable mechanism for
the fluorescence quenching effect was reported by Mahapa-
tra et al., which suggested an inversion between the strongly
emissive ππ* state and the poorly emissive nπ* states of the
fluorophore. Here, the complexation through the hydrogen
bond formation of the indole NH group with the HSO4− and
CN− was responsible for the better stabilisation of n–π* state

6
D. SAIN eT Al.
Figure 5. 1h Nmr spectra of (a) R1 and R1:CN− complex (b) R2 and R2:HSO4− complex and (c) R3, R3:HSO4− and R3:CN− in cD3cN.

SuPRAMOleCulAR CHeMISTRy
7
Figure 6. (colour online) mep map diagrams (positive regions in blue colour, isovalue for new surfaces: mo = 0.02, density = 0.0004) of (a) R1, (c)
R2, (e) R3, and the optimised complex structures of (b) R1:CN− complex, (d) R2:HSO4− complex, (f) R3:HSO4− complex and (g) R3:CN− complex
by DFt/B3lyp/6-31G method.
sity) in uV–vis and fluorescence titration also suggested the
same stoichiometry of complexation (see ESI, Figure S14). The
association constant (Ka) values of the receptors with all the
anions were calculated by Benesi–Hildebrand linear plot (20)
using uV–vis and fluorescence spectroscopic titration data.
The highest association constant values were observed for
R1 with CN−, R2 with HSO4− and R3 with HSO4− and CN− (see
ESI, Tables S3, S4 and S5).
0.15 ppm). The H9 proton at the meso position appeared
slightly down field upon complexation. In case of R2,
the peak positions varied significantly with 1.0 equiv-
−
alent HSO4 (Figure 5(b)) and the NH peak shifted from
7.86 to 9.17 ppm (Δδ 1.31 ppm) upon 1:1 complexation
with HSO4−. Most of the aromatic protons of R2 appeared
slightly down field. The proton at meso position shifted to
downfield from 7.12 to 7.59 ppm (Δδ 0.47 ppm) upon com-
plexation. While, the peak positions changed drastically for
R3 upon addition of 1.0 equivalent HSO4− and 3.0 equiva-
lents CN− ions (Figure 5(c)). The NH peak shifted from 7.92
to 9.20 ppm (Δδ 1.28 ppm) and 9.38 ppm (Δδ 1.46 ppm)
Complexation studies of the receptors using 1H NMR
technique
−
The specific complexation tendency of R1 with CN−, R2 with
on complexation with HSO4 and CN−, respectively. The
−
−
HSO4 and R3 with HSO4 and CN− were confirmed by the
visual colour change, uV–vis and fluorescence experiments.
Therefore, we performed the 1H NMR complexation analysis
of the receptors with the respective anions only. A probable
binding mode of the respective complexes is presented in
Figure 4.
aromatic protons of R3 appeared slightly up field, except
the protons adjacent to NH (H6). The H2 proton peak of
R3 merged with the peak of H3 due to upfield shifting of
H2 (from 7.53 to 7.43 ppm, Δδ 0.10 ppm), which made the
spectrum of the complexes broad in the aromatic region.
Same peak broadening took place by merging two proton
peaks (H5 and H6), where H5 peak shifted to upfield (from
7.02 to 6.93 ppm, Δδ 0.09 ppm) and H6 peak shifted to
downfield (from 6.81 to 6.89 ppm, Δδ 0.08 ppm). The pro-
ton at meso position (H7) moved to upfield slightly upon
complexation. So, it could be summarised that the CN−
and HSO4− anions strongly coordinate with the NH groups
of the respective receptors and drag the electron density
from the neighbouring CH centres also.
From the 1H NMR spectrum of R1 in CD3CN, it was clearly
observed that the peak positions of R1 shifted dramati-
cally, when 2.0 equivalents nBu4NCN was introduced to
R1 solution (Figure 5(a)). The NH peak shifted from 7.83
to 9.33 ppm (Δδ 1.50 ppm) upon 1:2 complexation with
CN−. Most of the aromatic protons of R1 moved slightly up
field, except the protons adjacent to NH groups (H8) which
shifted to a downfield region from 6.61 to 6.76 ppm (Δδ

8
D. SAIN eT Al.
Table 1. energy of the receptors and their complexes with cN− and
hSo4−.
The electron density distribution of the receptors was dis-
torted by the influence of the anions through the formation of
different hydrogen bonds. So, the orbital diagrams of the highest
occupied molecular orbital (HOMO) and the lowest unoccupied
molecular orbital (luMO) of the receptors and their complexes
were investigated, which is shown in ESI, Figures S17, S18 and
S19. Careful inspection of the MOs from DFT calculation shows
that the position of HOMO or luMO parts in the molecules is
being changed upon complexation. Such different dispositions
of the HOMO and luMOs might be responsible for the visual
colour change of the receptor solutions in the presence of ani-
ons. The quantum chemical DFT calculations also asserted the
decrease in energy gap of HOMO and luMO on complexation
receptors
optimisation energy
(a.u.)
complexes
optimisation energy
(a.u.)
R1
R2
R3
−1130.83 −1304.14
−1128.09
−
−
R1:CN−
R2:HSO4
R3:HSO4
R3:CN−
−1316.59 −2003.07 −1827.42 −1406.47
Quantum chemical (DFT) calculation and molecular
modelling studies
Quantum chemical DFT calculations were performed using
Gaussian09 (21) program package with the aid of the Gauss-
View 5.0 (22) visualisation program. The structure of the
receptors and their complexes were optimised by density
functional theory (DFT) in its restricted forms, using 6–31 g
basis set and B3lyP procedure (23) DFT calculation and
molecular modelling study exhibited the energy-optimised
structures, electronic properties and the probable modes of
binding through the formation of different hydrogen bonds
between receptors and anions.
−
with CN− and HSO4 , resulting the bathochromic shift in the
uV–vis absorption spectra (9g)This calculation also pointed out
the total energy of all the optimised complex structures were
very low compare to the energy of their respective receptors
(Table 1) and concluded the greater stability of the complexes
than receptor itself.
Conclusions
Molecular electrostatic potential (MeP) map diagram
(Figure 6(a), (c), and (e)) displayed the most positive regions
shown in deep blue colour and were sited mainly above the
NH protons of indole moieties. The appearance of this positive
region above the NH protons encouraged CN− and HSO4− to
take part for H-bonding. It was also found that the NH groups
of each receptor (far apart from each other) could bind only
larger size of anions which contained at least two available
electrons donating centres for hydrogen bond formation. This
In conclusion, we reported the design and synthesis of three
indolyl dipodal and tripodal receptors (R1, R2 and R3), which
−
were very efficient colorimetric sensor for CN− and HSO4
among other anions. R1 showed strong binding interactions
with highly poisonous cyanide (CN−) ion, whereas R2 exhib-
−
ited very selective sensing ability towards toxic HSO4 ion.
An interesting observation was found for R3 as it could sense
−
both HSO4 and CN− selectively. The colour changes of the
−
criterion was perfectly fulfilled by the HSO4 anion due to the
size and shape complementarity.
receptors in the presence of CN− and HSO4− could be visual-
ised instantly through naked eyes. uV–vis spectra, fluores-
The optimised R1:CN− complex structure suggested
that R1 could bind two CN− ions individually as the ‘NH’
groups of R1 remained far away from each other (Figure
6(b)). Due to the very high nucleophilic character of CN−,
it remained connected to the positive regions of R1, i.e.
‘NH’ centres through hydrogen bonding (2.25 and 2.18 Å).
1
cence spectra and H-NMR spectra clearly pointed out the
hydrogen-bonded complex formation of the receptors with
the respective anions. Quantum chemical (DFT) calculations
supported the above phenomena.
−
Experimental section
R2:HSO4 complex structure showed that two ‘O’ centres
of HSO4− ion were connected through hydrogen bonding
(1.87 Å) with the two N–H protons of R2. Two adjacent ring
protons (C–H) of R2 were also hydrogen bonded (2.18 Å)
with another ‘O’ atom of HSO4− (Figure 6(d)). The complex
structure of R3 with HSO4 exhibited that the HSO4 ion
was attached with R3 in 1:1 fashion, where two NH protons
of R3 were connected with two ‘O’ atom of HSO4− individ-
ually through H-bonding interactions (2.23 Å). Another ‘O’
atom of HSO4− ion interacted with three adjacent C–H pro-
tons via three different hydrogen bonds (2.18 Å) formation
(Figure 6(f)). On the other hand, R3:CN− complex showed
that three individual CN− ions were connected to three
different ‘NH’ centres of R3 through hydrogen bonding
(1.84 Å) (Figure 6(g)).
All reagents (AR grade) were purchased commercially and
used without further purification. Solvents were dried fol-
lowing standard procedures. uV-grade CH3CN was used
for uV–vis and fluorescence titration. 1H-NMR spectra were
recorded on a Bruker AV400 instrument at 400 MHz with
TMS as internal standard. eSI-MS measurements were car-
ried out using a microTOF-Q II 10330 mass spectrometer. IR
spectra were measured using Spectrum 2000 Perkin–elmer
Spectrometer. uV–vis spectra and fluorescence spectra
were recorded using uV-1800 Shimadzu Spectrophotome-
ter (1.0 cm quartz cell) and Perkin–elmer lS 55 fluorescence
spectrometer, respectively. Melting points were detected
using Remco hot-coil stage melting point apparatus and
are uncorrected.
−
−

SuPRAMOleCulAR CHeMISTRy
9
13C-NMR of R2 (125 MHz, CDCl3): δ 136.1, 134.7, 131.5, 128.7,
126.9, 126.8, 124.2, 123.5, 121.4, 119.6, 118.8, 118.5, 110.5,
34.6; TOF-MS ES+ (m/z, %): 423.1777 (M+1, 20%), 422.1728
(M+, 40%), 421.1705 (M−1, 100%); FTIR (KBr, cm−1): 3409 (NH
str.), 3048 (benzylic CH str.), 1721, 1619 (ar C=C str.), 1454,
1417 (ar. C–N str.), 1338, 1092, 1014, 739 (NH bend.).
Synthesis of 4-(di(1H-indol-3-yl)methyl)-N,N-dimethyl-
benzenamine (R1) (24)
Indole (0.393 g, 3.35 mmol) was mixed with 4-dimethyl-
aminobenzaldehyde (0.25 g, 1.675 mmol) in dry ethanol
(10.0 ml) followed by the addition of Bi(NO3)3·5H2O (0.813 g,
0.167 mmol). After constant stirring at room temperature
for 5 h, the reaction mixture was dried by removing ethanol
and distilled water was added to get precipitate. The ppt. was
then filtered and dried followed by the purification through
column chromatography to obtain the desired pink colour
receptor 1 (80% yield, m.p. 208–210 °C).
Synthesis of tri-(indol-3-yl)methane (R3) (26)
The condensation reaction between indole (807 mg,
6.89 mmol) and indole-3-carbaldehyde (500 mg, 3.445 mmol)
was carried out in ethanol (10.0 ml) using Bi(NO3)3·5H2O
(167 mg, 0.344 mmol) as a catalyst with continuous stirring
at room temperature for 6 h. After completion of the reaction,
ethanol was distilled off under vacuum and distilled water
was then added to precipitate the product. The residue was
filtered, dried and purified through column chromatography
using CHCl3 solvent to obtain pure receptor 3 (solid, reddish
brown colour, 90% yield, m.p. 235–237 °C).
Spectral data of R1
1H-NMR of R1 (400 MHz, CD3CN): δ 7.83 (bs, 2H), 7.63 (q,
J = 3.2 Hz, 2H), 7.45 (q, J = 3.2 Hz, 2H), 7.33 (d, J = 8.0 Hz, 2H), 7.26
(d, J = 8.4 Hz, 2H), 7.12 (d, J = 6.4 Hz, 2H), 7.08 (d, J = 6.4 Hz, 2H)
6.91 (s, 2H), 5.72 (s, 1H), 2.83 (s, 6H); 1H-NMR of R1:CN− com-
plex (400 MHz, CD3CN): δ 9.33 (bs, 2H), 7.40 (d, J = 8.0 Hz, 2H),
7.32 (d, J = 8.0 Hz, 2H), 7.19 (d, J = 8.0 Hz, 2H), 7.09 (t, J = 7.2 Hz,
2H), 6.92 (t, J = 7.2 Hz, 2H), 6.76 (s, 2H), 6.71 (d, J = 7.2 Hz, 2H),
5.78 (s, 1H), 2.88 (s, 6H); 13C-NMR of R1 (100 MHz, CDCl3):
δ 149.0, 136.6, 129.2, 127.1, 123.4, 121.7, 120.4, 120.0, 119.0,
112.6, 112.1, 110.8, 40.8, 39.1, 29.6; TOF-MS ES+ (m/z, %):
367.06 (M+2, 20%), 366.05 (M+1, 100%), 364.04 (M−1, 30%);
FTIR (KBr, cm−1): 3405 (NH str.), 2926 (benzylic CH str.), 1726,
1604 (ar. C=C str.), 1515, 1111 (ar. C–N str.), 745 (NH bend.).
Spectral data of R3
1H NMR of R3 (400 MHz, CD3CN): δ 7.92 (bs, 3H), 7.53 (d,
J = 8.4 Hz, 3H), 7.38 (d, J = 8.0 Hz, 3H), 7.18 (t, J = 8.0 Hz, 3H),
1
7.02 (t, J = 7.6 Hz, 3H), 6.81 (s, 3H), 6.19 (s, 1H); H NMR of
R3:HSO4− complex (400 MHz, CD3CN): δ 9.20 (bs, 3H), 7.43–
7.39 (m, 6H), 7.09 (t, J = 7.6 Hz, 3H), 6.92 (t, J = 7.6 Hz, 3H), 6.89
1
(s, 3H), 6.15 (s, 1H); H NMR of R3:CN− complex (400 MHz,
CD3CN): δ 9.38 (bs, 3H), 7.43–7.39 (m, 6H), 7.08 (t, J = 8.0 Hz,
3H), 6.92 (t, J = 8.0 Hz, 3H), 6.89 (s, 3H), 6.15 (s, 1H); 13C-NMR of
R3 (100 MHz, CDCl3): δ 136.6, 127.0, 123.3, 121.6, 120.0, 119.3,
118.9, 110.9, 29.6; TOF-MS ES+ (m/z, %): 385.01 (M+1+23,
30%), 384.01 (M+23, 100%), 360.02 (M−1, 25%), 245.03 (35%);
FTIR (KBr, cm−1): 3405 (NH str.), 3051 (benzylic CH Str.), 1609
(Ar. C=C str.), 1455, 1337 (Ar. C–N str.), 1089, 747 (NH def).
Synthesis of 3-((anthracen-9-yl)(1H-indol-3-yl)methyl)-
1H-indole (R2) (25)
The condensation reaction between indole (227.5 mg,
1.94 mmole) and 9-anthracenecarboxaldehyde (200 mg,
0.97 mmole) was carried out in dry ethanol (10.0 ml) using
Bi(NO3)3·5H2O (94.2 mg, 0.19 mmole) as a catalyst with contin-
uous stirring at room temperature for 6 h. After monitoring the
completion of the reaction, ethanol was distilled off under vac-
uum. Distilled water was then added and the organic part was
extracted with ethyl acetate for several times. The extracted
organic part was now dried and purified through column chro-
matography using 20% Pet. ether in CHCl3 solvent to obtain
pure receptor 2 (solid, off white colour, 85% yield, m.p. 240 °C).
Acknowledgements
SD acknowledges erasmus Mundus Action 2 AReAS+ for provid-
ing Postdoctoral fellowship. DS, CK and AK are sincerely thankful to
Indian School of Mines for the Junior Research Fellowship. We are
grateful to Professor Wim Dehaen, Department of Chemistry, Ku
leuven for his valuable suggestion.
Supplemental material
Spectral data of R2
Supplemental data for this article can be accessed here:
http://dx.doi.org/10.1080/10610278.2015.1092536
1H NMR of R2 (400 MHz, CD3CN): δ 8.63 (d, J = 9.2 Hz, 2H),
8.43 (s, 1H), 7.99 (d, J = 8.0 Hz, 2H), 7.86 (bs, 2H), 7.41 (s, 2H),
7.36 (bs, 2H), 7.30 (d, J = 8.0 Hz, 2H), 7.12 (s, 1H), 7.09 (d,
J = 8.0 Hz, 4H), 6.85 (t, J = 7.6 Hz, 2H), 6.77 (s, 2H); 1H NMR of
R2:HSO4− complex (400 MHz, CD3CN): δ 9.17 (bs, 2H), 8.66
(d, J = 9.2 Hz, 2H), 8.54 (s, 1H), 8.06 (d, J = 8.8 Hz, 2H), 7.59 (s,
1H), 7.42 (s, 2H), 7.37 (d, J = 8.0 Hz, 2H),7.30 (bs, 2H), 7.04 (t,
J = 7.6 Hz, 2H), 6.95 (d, J = 8.0 Hz, 2H), 6.79 (s, 2H), 6.78 (m, 2H);
References
(1) (a) Martinez-Manez, R.; Sancenon, F. Chem. Rev. 2003, 103,
4419–4476; (b) Caltagirone, C.; Gale, P.A. Chem. Soc. Rev. 2009,
38, 520–563; (c) Wiskur, S.l.; Ait-Haddou, H.; lavigne, J.J.;
Anslyn, e.V. Acc. Chem. Res. 2001, 34, 963–972; (d) Amendola,
V.; Fabbrizzi, l. Chem. Commun. 2009, 513–531.

10
D. SAIN eT Al.
(2) (a)young, C.;Tidwell, l.; Anderson, C. Cyanide Social, Industrial,
and Economic Aspects; Minerals, Metals, and Materials
Society: Warrendale, PA, 2001; (b) eisler, R. Cyanide Hazards to
Fish, Wildlife, and Invertebrates: A 80 Synoptic Review – U.S. Fish
Wildl. Serv., Biol. Rep. 1991, 85, 1–58.
R.G.; Bai, Z.P. Chem. Commun. 2006, 624–626; (c) Hu, S.Z.;
Guo, y.; Xu, J.; Shao, S.J. Org. Biomol. Chem. 2008, 6, 2071–
2075; (d) lopez, M.V.; Bermejo, M.R.; Vazquez, M.e.; Taglietti,
A.; Zaragoza, G.; Pedrido, R.; Martinez-Calvo, M. Org. Biomol.
Chem. 2010, 8, 357–362.
(3) (a) Baskin, S.I.; Brewer, T.G. In Medical Aspects of Chemical and
Biological Warfare: Cyanide Poisoning (Chapter 10) Sidell, F.;
Takafuji, e.T.; Franz, D.R. eds.; TMM Publications: Washington,
DC, 1997, 10, 271–286; (b) Holland, M.A.; Kozlowski, l.M. Clin.
Pharm. 1986, 5, 737–741; (c) Way, J.l. Annu. Rev. Pharmacol.
Toxicol. 1984, 24, 451–481.
(11) (a) li, Q.; Guo, y.; Shao, S. Analyst 2012, 137, 4497–4501; (b)
Hutt, J.T.; Jo, J.; Olasz, A.; Chen, C.-H.; lee, D.; Aron, Z.D. Org.
Lett. 2012, 14, 3162–3165; (c) Gale, P.A.; Hiscock, J.R.; lalaoui,
N.; light, M.e.; Wells, N.J.; Wenzel, M. Org. Biomol. Chem.
2012, 10, 5909–5915; (d) Sakai, R.; Nagai, A.; Tago, y.; Sato, S.;
Nishimura, y.; Arai, T.; Satoh, T.; Kakuchi, T. Macromolecules
2012, 45, 4122–4127; (e) Fu, l.; Jiang, F.-l.; Fortin, D.; Harvey,
P.D.; liu, y. Chem. Commun. 2011, 47, 5503–5505.
(12) (a) Gale, P.A. Chem. Commun. 2008, 4525–4540; (b) Shiraishi,
y.; Maehara, H.; Hirai, T. Org. Biomol. Chem. 2009, 7, 2072–
2076; (c) Caltagirone, C.; Gale, P.A.; Hiscock, J.R.; Brooks, S.J.;
Hursthouse, M.B.; light, M.e. Chem. Commun. 2008, 3007–
3009; (d) Dydio, P.; Zielinski, T.; Jurczak, J. Chem. Commun.
2009, 4560–4562.
(13) (a) Wang, l.; He, X.; Guo, y.; Xu, J.; Shao, S. Org. Biomol. Chem.
2011, 9, 752–757; (b) Wang, l.; Wei, W.; Guo, y.; Xu, J.; Shao, S.
Spectrochim. Acta Part A 2011, 78, 726–731; (c) He, X.; Hu, S.; liu,
K.; Guo, y.; Xu, J.; Shao, S. Org. Lett. 2006, 8, 333–336; (d) Wei, W.;
Guo,y.; Xu, J.; Shao, S. Spectrochim. Acta Part A 2010, 77, 620–624.
(14) (a) Dey, S.; Sain, D.; Goswami, S. RSC Adv. 2014, 4, 428–433; (b)
Dey, S.; Sain, D. Supramol. Chem. 2014, 26, 769–776; (c) Dey, S.;
Sain, D.; Kumar, A.; Kumari, C. RSC Adv. 2014, 4, 51486–51495.
(15) (a) Mallegol, T.; Gmouh, S.; Meziane, M.A.A.; Blanchard-Desce,
M.; Mongin, O. SynthSIs 2005, 1771–1774; (b) Fieser, l.F.;
Hartwell, J.l.; Jones, J.e.; Wood, J.H.; Bost, R.W. Org. Syn. 1940,
20, 11–13.
(4) (a) Kumar, S.; Singh, P.; Hundal, G.; Hundal, M.S.; Kumar, S.
Chem. Commun. 2013, 49, 2667–2669; (b) Mashraqui, S.H.;
Betkar, R.; Chandiramani, M.; estarellasb, C.; Fronterab, A.
New J. Chem. 2011, 35, 57–60; (c) lee, K.S.; Kim, H.J.; Kim, G.H.;
Shin, I.; Hong, J.I. Org. Lett. 2008, 10, 49–51; (d) li, M.-J.; lin,
Z.; Chen, X.; Chen, G. Dalton Trans. 2014, 43, 11745–11751;
(e) Wang, F.; Wang, l.; Chen, X.; yoon, J. Chem. Soc. Rev. 2014,
43, 4312–4324; (f) Garg, B.; yan, l.; Bisht, T.; Zhu, C.; ling, y.-
C. RSC Adv. 2014, 4, 36344–36349; (g) Khairnar, N.; Tayade, K.;
Bothra, S.; Sahoo, S.K.; Singh, J.; Singh, N.; Bendre, R.; Kuwar,
A. RSC Adv. 2014, 4, 41802–41806; (h) Wang, P.; yao, y.; Xue,
M. Chem. Commun. 2014, 50, 5064–5067; (i) Zhang, y.; yu, D.;
Feng, G. RSC Adv. 2014, 4, 14752–14757; (j) Peng, M.-J.; Guo,
y.; yang, X.-F.; Suzenet, F.; li, J.; li, C.-W.; Duan, y.-W. RSC Adv.
2014, 4, 19077–19085.
(5) (a) Goswami, S.; Manna, A.; Paul, S.; Aich, K.; Das, A.K.;
Chakraborty, S. Tetrahedron Lett. 2013, 54, 1785–1789; (b)
Saha, S.; Ghosh, A.; Mahato, P.; Mishra, S.; Mishra, S.K.; Suresh,
e.; Das, S.; Das, A. Org. Lett. 2010,
12, 3406–3409; (c) Hao, y.;
Chen, W.; Wang, l.; Zhou, B.; Zang, Q.; Chen, S.; liu, y.-N. Anal.
Methods 2014, 6, 2478–2483; (d) lin, y.-D.; Peng, y.-S.; Su, W.; Tu,
C.-H.; Sun, C.-H.; Chow, T.J. Tetrahedron 2012, 68, 2523–2526;
(e) Dong, y.-M.; Peng, y.; Dong, M.; Wang, y.-W. J. Org. Chem.
2011, 76, 6962–6966; (f) Xu, Z.; Chen, X.; Kim, H.N.; yoon, J.
Chem. Soc. Rev. 2010, 39, 127–137; (g) Huh, J.O.; Do, y.; lee,
M.H. Organometallics 2008, 27, 1022–1025; (h) Konidena, R.K.;
Thomas, K.R.J. RSC Adv. 2014, 4, 22902–22910.
(16) (a) Hammud, H.H.; Ghannoum, A.; Masoud, M.S. Spectrochim.
Acta. Part A 2006, 63, 255–265; (b) Sain, D.; Kumari, C.; Kumar,
A.; Dey, S. Sens. Actuat. B 2015, 221, 849–856.
(17) (a) Shortreed, M.; Kopelman, R.; Kuhn, M.; Hoyland, B. Anal.
Chem. 1996, 68, 1414–1418; (b) lin, W.; yuan, l.; Cao, Z.; Feng,
y.; long, l. Chem. Eur. J. 2009, 15, 5096–5103; (c) yang, y.;
Cheng, T.; Zhu, W.; Xu, y.; Qian, X. Org. Lett. 2011, 13, 264–267;
(d) Zhu, M.; yuan, M.; liu, X.; Xu, J.; lv, J.; Huang, C.; liu, H.; li,
y.; Wang, S.; Zhu, D. Org. Lett. 2008, 10, 1481–1484.
(18) (a) Mahapatra, A.K.; Hazra, G.; Sahoo, P. Beilstein J. Org. Chem.
2010, 6, 1–8; (b) Bazzicalupi, C.; Bencini, A.; Bianchi, A.;
Borsari, l.; Danesi, A.; Giorgi, C.; lodeiro, C.; Mariani, P.; Pina,
F.; Santarelli, S.; Tamayo, A.; Valtancoli, B. Dalton Trans. 2006,
4000-4010.
(6) (a) Xu, Z.; Chen, X.; Kim, H.N.;yoon, J., Chem. Soc. Rev. 2010, 39,
127–137; (b) Kaur, K.; Saini, R.; Kumar, A.; luxami, V.; Kaur, N.;
Singh, P.; Kumar, S. Coord. Chem. Rev. 2012, 256, 1992–2028.
(7) Moyer, B.A.; Delmau, l.H.; Fowler, C.J.; Ruas, A.; Bostick, D.A.;
Sessler, J.l.; Katayeu, e.; Pantos, G.D.; llinares, J.M.; Hossain,
M.A.; Kang, S.O.; Bowman-James, K. Supramolecular Chemistry
of Environmentally Relevant Anions: Advances in Inorganic
Chemistry ed. eldik, R.V.; Bowman-James, K., Academic Press:
New york, 2006, 59, 175–204.
(8) McKee, J.e.; Wolf, H.W. Water Quality Criteria, 2nd ed.; California
State Water Quality Control Board: Sacramento, CA, 1963.
(9) (a) Goswami, S.; Das, S.; Aich, K.; Sarkar, D.; Mondal, T.K.
Tetrahedron Lett. 2013, 54, 6892–6896; (b) Bhardwaj,V.K.; Saluja,
P.; Hundal, G.; Hundal, M.S.; Singh, N.; Jang, D.O. Tetrahedron
2013, 69, 1606–1610; (c) Song, N.R.; Moon, J.H.; Choi, J.; Jun,
e.J.; Kim, y.; Kim, S.-J.; lee, J.y.; yoon J. Chem. Sci. 2013, 4, 1765–
1771; (d) Kaur, P.; Kaur, H.; Singh, K. Analyst 2013, 138, 425–428;
(e) yang, S.-T.; liao, D.-J.; Chen, S.-J.; Hu, C.-H.; Wu, A.-T. Analyst
2012, 137, 1553–1555; (f) Sarkar, D.; Pramanik, A.K.; Mondal,
T.K. RSC Adv. 2014, 4, 25341–25347; (g) Fegade, u.; Sahoo, S.K.;
Singh, A.; Mahulikar, P.; Attarde, S.; Singh, N.; Kuwar, A. RSC
Adv. 2014, 4, 15288–15292; (h) Kumar, V.; Kumar, A.; Diwan, u.;
upadhyay, K.K. Chem. Commun. 2012, 48, 9540–9542.
(19) Job, P. Ann. Chim. 1928, 9, 113–203.
(20) (a) Benesi, H.A.; Hildebrand, J.H. J. Am. Chem. Soc. 1949, 71,
2703–2707; (b) liao, J.-H.; Chen, C.-T.; Chou, H.-C.; Cheng,
C.-C.; Chou, P.-T.; Fang, J.-M.; Slanina, Z.; Chow, T.J. Org. Lett.
2002, 4, 3107–3110.
(21) Frisch, M.J., et al. GAUSSIAN 09, Rev. D.01; Gaussian, Inc.:
Wallingford, CT, 2009.
(22) Dennington, R.D. (II), Keith, T.A.; Millam, J.M. GaussView 5.0,
Gaussian, Inc.: Wallingford, CT, 2009.
(23) (a) Becke, A.D. J. Chem. Phys. 1993, 98, 5648–5652; (b) lee, C.;
yang, W.; Parr, R.G. Phys. Rev. B 1988, 37, 785–789; (c) Becke,
A.D. Phys. Rev. A 1988, 38, 3098–3100.
(24) Gu, R.; Van Snick, S.V.; Robeyns, K.; Van Meervelt, l.V.; Dehaen,
W. Org. Biomol. Chem. 2009, 7, 380–385.
(25) Vahdat, S.M.; Khaksar, S.; Baghery, S. Lett. Org. Chem. 2012, 9,
138–144.
(10) (a) Ali, H.D.P.; Kruger, P.e.; Gunnlaugsson, T. New J. Chem.
2008, 32, 1153–1161; (b) lin, Z.H.; Ou, S.J.; Duan, C.y.; Zhang,
(26) Deb, M.l.; Baruah, B.; Bhuyan, P.J. Synthesis 2008, 286–292.