An ampyrone based azo dye as pH-responsive and chemo-reversible colorimetric fluorescent probe for Al3+ in semi-aqueous medium: Implication towards logic gate analysis

Article abstract of DOI:10.1039/c7nj04194b

A novel ampyrone based azo dye, 4-((6-hydroxybenzo[d][1,3]dioxol-5-yl)diazenyl)-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one (1), was synthesized by coupling sesamol and 4-amino antipyrine (ampyrone) and was characterized spectroscopically. The interaction

Full text of DOI:10.1039/c7nj04194b

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ISSN 1144-0546
PAPER
Jason B. Benedict et al.
The role of atropisomers on the photo-reactivity and fatigue of
diarylethene-based metal–organic frameworks
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An Ampyrone based azo dye as pH-responsive and chemo-
reversible colorimetric fluorescent probe for Al3+ in semi-aqueous
medium: Implication towards logic gate analysis
Gaurav Bartwala, Komal Aggarwala and Jitender M. Khurana*
A
novel ampyrone based azo dye, 4-((6-hydroxybenzo[d][1,3]dioxol-5-yl)diazenyl)-1,5-dimethyl-2-phenyl-1H-pyrazol-
3(2H)-one (1), has been synthesized by coupling sesamol and 4-amino antipyrine (ampyrone) and was characterized
spectroscopically. The interaction of azo dye (1) with different metal ions has been studied using UV-vis and fluorescence
spectra. Chemosensor 1 exhibits high selectivity and sensitivity towards Al3+ over other metal ions by fluorescence
enhancement in methanol: water (1:1, v/v, at pH = 7.2), which could also be detected directly by the naked eye under
visible light. The fluorescence of 1-Al3+ complex was found to be reversible in presence of EDTA. pH-dependent absorption
behavior of chemosensor 1 was also investigated. It was observed that, chemosensor 1 could also be used as selective
‘naked-eye’ colorimetric sensor for H+, and displayed a very strong red shift in the absorption band from 492 nm to 540 nm
with a notable color change from yellow to violet-blue. Moreover, the chemosensor 1 showed keto-enol tautomerization
in the presence of acidic media and both forms have been confirmed by 1H and 13C NMR spectra. Practical applicability of
sensor 1 has been further explored by use of sensing strip analysis which allows rapid detection of Al3+ and H+ ions. NMR
and DFT optimized geometries of 1 suggest that the compound is present in the azo form (enol form) in the ground state.
In addition, one INHIBIT logic gate was constructed based on multi-responsive properties of 1 induced by Al3+ and EDTA2-
which contained two input signals (In1: Al3+, In2: EDTA) and an output signal (O1: Fluorescence intensity at 613 nm. The
chemosensor 1 exhibited a high association constant with a detection limit of 3.55 x 10-7 M for Al3+ in MeOH-water
solution.
According to WHO, the average admissible value of Al3+ ions that
human can intake is about 7 mg/kg of the body weight.4,5 Over
Introduction
Aluminium is the most abundant metallic element found naturally on
the planet comprising just over 8% of the earth’s crust. It is also third
most abundant of all elements after oxygen and silicon, and exits in
nature in its ionic form Al3+. Aluminum and its alloys have diversified
applications in our lifestyles, such as packaging materials, food
additives, cooking utensils, building constructions etc.1,2 The content
of dissolved aluminium in water and soil increased due to acid rain,
results in the inhibition of plant growth3 and thus, most foods
contain at least trace amount of aluminium. Food products
containing aluminium based food additives have a higher amount of
aluminium than natural level.
accumulation of aluminium in our body may not only lead to the
failure of nervous system but can also cause a wide range of
diseases like Al-related bone disease (ARBD), idiopathic Parkinson’s
disease, impairment of memory and Alzheimer’s disease, microcytic
hypochromic anemia, amyotrophic lateral sclerosis, dementia etc.6-9
Therefore, the detection of Al3+ is essential to control its impact on
the human health as well as on the environment.
In recent years, bipyridine, rhodamine, diazafluorene and naphthol
functionalized fluorescent Schiff bases have been designed for Al3+
detection but lack of spectroscopic characterization, poor binding
ability and strong hydration ability10-13 makes these sensors less
compelling. Moreover, azo dye based probes have not been
extensively explored in the literature for the selective sensing of
aluminium ion. The detection of Al3+ is commonly interfered by
aDepartment of Chemistry, University of Delhi, Delhi-110007, India
*Corresponding author. Tel.: +91 11 2766772; fax: +91 11 27667624
E-mail addresses: jmkhurana1@yahoo.co.in
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other trivalent metal ions like In3+, Fe3+, Cr3+, and Ga3+ in the binding The design of synthesized compound
Journal Name
1
consists of antipyrine
process due to similarity in electronic configuration.14-16 Therefore, fluorophore unit attached to a sesamol ring (receptor) through a azo
advancement in the synthesis of sensitive, selective and reversible spacer. Sesamol ring can act as a receptor by transferring lone pair of
Al3+ probes with improved properties is still in high demand.
electrons on oxygen to the antipyrine ring by PET mechanism shown
Azo dyes have attracted considerable importance in the recent years in Fig. 1.
because of their utilities and applications in the field of indicators,
colorimetric probes, dyeing of textile fibers, food additives, pigments
and paint industries.17 An enormous variety of colors with a
reasonably simple and rapid synthesis has made azo dye an
illustrious mode for developing fluorescent enhancement probes.
Incorporation of a bioactive heterocyclic moiety, such as antipyrine,
into the backbone of azo dye, would further enhance their
applications as colorant and chromophoric strength.18-22
Fluorophore
Receptor
HO
O
O
O
N
N
N
N
PET
Spacer
Recently ampyrone based azo dyes have been synthesized as
Fig. 1: Design of Azo dye with ‘receptor–spacer–fluorophore’ PET
fluorescent chemosensors for the detection of various metal ions.23-
26 But no ampyrone azo dye based colorimetric probes are available
in the literature for the detection of Al3+. In continuation of our
ongoing research on developing novel low cost and efficient
fluorescent chemosensors27-29, we designed and synthesized a novel
azo dye from the coupling of sesamol and ampyrone to investigate
its fluorescence properties and role as a metal ion and pH sensor.
design.
Effect of metal ions on photophysical properties of 1
The photophysical properties like UV-vis and fluorescence of
chemosensor 1 (1 x 10-5 M, MeOH : H2O (1:1, v/v) have been studied
by the addition of different metal ions such as Pb2+, Cu2+, Zn2+, Mn2+
,
Cd2+, Hg2+, Sr2+, Co2+, Sn2+, Fe3+, Al3+, Cr3+, La3+, In3+ and Th4+, Ni2+,
Mg2+, Ca2+, Ba2+, Na+ in MeOH : H2O (1:1, v/v) buffered with HEPES
solution at pH 7.2.
Results and Discussion
Synthesis and characterization of chemosensor (1)
Absorption spectra
Herein, we report the synthesis of a novel PET (photoinduced
electron transfer) based azo dye of ampyrone i.e. 4-((6-
hydroxybenzo[d][1,3]dioxol-5-yl)diazenyl)-1,5-dimethyl-2-phenyl-1H-
pyrazol-3(2H)-one (1) by diazotization of 4-amino-1,5-dimethyl-2-
phenyl-1H-pyrazol-3(2H)-one followed by the addition of alkaline
solution of sesamol at 0-5oC shown in Scheme 1. The novel product 1
has been characterized by 1H NMR, 13C NMR, FTIR, and HRMS. The
chemosensor 1 exhibited fluorescence enhancement upon binding
with Al3+ which was found to be reversible with EDTA and also
showed a visible color change from yellow to pink. Moreover,
chemosensor 1 showed keto-enol tautomerism in the presence of an
acid which was confirmed by 1H and 13C NMR spectra.
The UV-vis absorption spectrum of chemosensor 1 showed two weak
absorption bands in short wavelength region centered at 238 nm,
334 nm and a broad band in the long wavelength range from 394 to
490 nm. Addition of one equiv. of different cations Pb2+, Cu2+, Zn2+
,
Mn2+, Cd2+, Hg2+, Sr2+, Co2+, Sn2+, Fe3+, Cr3+, La3+, In3+ and Th4+, Ni2+,
Mg2+, Ca2+, Ba2+, Na+ exhibited no effect in the absorption spectrum
of 1. However, the addition of one equiv. of Al3+ into 1 x 10-5 M, 1:1
MeOH:H2O solution of 1 resulted in a significant shift in the
absorption spectra shown in Fig. 2(a). In the presence of Al3+ ions,
band at 334 nm showed a bathochromic shift of 18 nm and
appeared at 352 nm. The broad band appearing in the range of 394
to 490 nm disappeared completely and a new band appeared in a
long wavelength region at 505 nm. The absorption spectrum of 1 has
been further investigated in presence of increasing amount of Al3+
.
The broad band at 394 to 490 nm showed diminishment while band
at 505 nm showed an enhancement in intensity with the isosbestic
point at 460 nm (Fig. 2(b)). These absorption spectral changes
Scheme 1: Synthesis of Compound 1
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resulted in a visible color change from yellow to pink in the presence
of Al3+ ions as detected by the naked eye (Fig. 3). Therefore,
can be
1
used as a potential colorimetric chemosensor for the detection of
Al3+ ions.
(a)
(b)
Fig. 4: Emission spectra of
1
(1 x 10-5 M) ) in MeOH : H2O (1:1)
containing HEPES (0.01 mM, pH=7.2) buffer solution (a) upon
addition of 1 equiv. of Pb2+, Cu2+, Cd2+, Zn2+, Mn2+, Co2+, Hg2+, Sr2+
,
Sn2+, Fe3+, Cr3+, La3+, Th4+, In3+, Al3+, Ni2+, Mg2+, Ca2+, Ba2+ and Na+
(a)
(b)
metal ions; (b) in the presence of varying amount of Al3+ (0 – 1 equiv.)
Fig. 2: UV-vis spectra of
1
(1 x 10-5 M) in MeOH : H2O (1:1) containing
HEPES (0.01 mM, pH=7.2) (a) upon addition of 1 equiv. of Pb2+, Cu2+
,
(λex = 450 nm); Inset: line graph of fluorescence intensities of
depending on the concentrations of Al3+
1
Cd2+, Zn2+, Mn2+, Co2+, Hg2+, Sr2+, Sn2+, Fe3+, Cr3+, La3+, Th4+, In3+, Al3+,
Ni2+, Mg2+, Ca2+, Ba2+ and Na+ metal ions; (b) in the presence of
varying amount of Al3+ (0 - 1 equiv.); Inset: line graph of absorbance
.
The fluorescence response of chemosensor
1
for various
intensities of 1 .
depending on the concentrations of Al3+
concentrations of Al3+ ions (0 – 1 equiv.) was also scanned. The
fluorescence intensity of was gradually increased upon addition of
1
an incremental amount of Al3+ ions and remained steady after the
addition of 1 equiv. of Al3+ ions, indicating the formation of 1:1
binding mode between
1
and Al3+ ions (Fig. 4(b)). Line graph of
with varying Al3+ concentrations also
fluorescence intensities of
1
showed no change in intensity after the addition of 1 equiv. of Al3+
ions.
Fig. 3: Visual color changes observed in MeOH : H2O (1:1) solution of
(1 x10-5 M) after addition of 1 equiv. of various metal ions.
Selectivity and Reversibility of chemosensor 1
1
The selectivity of chemosensor
determining the changes in fluorescence intensity of
in presence of various interfering metal ions (Fig. 5). The fluorescence
intensity of
in presence of 1 equiv. of Al3+ ions followed by the
1
for Al3+ ions was examined by
-Al3+ complex
Fluorescence spectra
1
The emission spectrum of chemosensor
1
(1 x 10-5 M), displayed a
very weak band at 587 nm (λex = 450 nm). This weak emission band
attributed to the existence of hydrazone form in solution phase
which diminishes the population of azo form in the excited state and
eventually undergoes photoisomerization.30,31 Another possibility for
weak fluorescence could be the presence of PET (photoinduced
1
addition of 10 equiv. of other metal ions like Pb2+, Cu2+, Zn2+, Mn2+,
Cd2+, Hg2+, Sr2+, Co2+, Sn2+, Fe3+, Cr3+, La3+, In3+ and Th4+ was remain
unaffected. This clearly indicates that the chemosensor
1 is highly
selective for Al3+ ions in presence of other competitive metal ions.
electron transfer). The fluorescence spectrum of
1 was investigated
in the presence of one equiv. of various cations Pb2+, Cu2+, Zn2+, Mn2+
Cd2+, Hg2+, Sr2+, Co2+, Sn2+, Fe3+, Cr3+, La3+, In3+, Th4+, Ni2+, Mg2+, Ca2+
,
,
Ba2+ and Na+ No such effect was observed in the emission spectra of
as shown in Fig. 4(a). However, a prominent enhancement in the
fluorescence intensity of
was observed after the addition of Al3+
1
1
ions with a redshift of 16 nm from 587 nm to 613 nm. This
enhancement in fluorescence intensity could be due to inhibition of
PET upon binding with Al3+ ions [34].
Fig. 5: Selectivity of
1
for Al3+ on the addition of 10 equiv. of various metal
ions.
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Reversibility plays a significant role in the development of a novel The binding stoichiometry of
Journal Name
1
and Al3+ was calculated from Job's
chemosensor for practical applicability. Therefore, we also examined plot analysis on the basis of fluorescence (Fig. 7). The Job’s plot
the interfering effect of various anions on the emission spectrum of measurement revealed 1:1 complexation stoichiometry between
1
1
-Al3+ complex. It can be inferred from Fig. 6 that the addition of 5 and Al3+. A graph was plotted by varying the mole fraction of Al3+
-
-
2-
equiv. of various anions like F-, Cl-, Br-, I-, NO2 , SCN-, ClO3 , PO4
,
ions while keeping the resultant concentration of
1
and Al3+ constant
2-
2-
CrO4 and SO3 to 1+Al3+ complex has no major effect on the (1.0 x 10-5 M). The plot displayed a maximum when the mole fraction
fluorescence intensity but addition of 5 equiv. of EDTA resulted in of Al3+ was nearly half.
fluorescence quenching and color change from pink to yellow.
(a)
(b)
Fig. 7: Job's plot for stoichiometric determination of 1
and Al3+.
Fig. 6: (a) Effect of various anions on the fluorescence behaviour of (
1
The stoichiometry of
1
and Al3+ was further confirmed by HRMS (ESI,
m/z) data analysis. The mass spectrum of 1-Al3+ complex showed a
peak at 478.1198 which corresponds to [(
+ Al + Cl + 2CH3OH) + H]+
(calcd. m/z: 478.1194, found: 478.1198, Fig. S1). This clearly confirms
the formation of 1:1 complex between chemosensor
and Al3+ ion.
The association constant (Ka) of
and Al3+ was obtained from Benesi-
+ Al3+) complex in MeOH : H2O (1:1) containing HEPES (0.01 mM,
pH=7.2) buffer solution (λex = 450 nm). (b) Reversible switching of the
emission of
1
(1 x 10-5M) at 613 nm upon alternate addition of Al3+
M
and EDTA. Inset: Images of color change during fluorescence
reversibility.
1
Further addition of Al3+ ions to the solution of 1 + Al3+ + EDTA,
resulted in the enhancement of fluorescence intensity again along
with the color change from yellow to pink, thus confirming the
1
Hildebrand plot32 (Fig. 8). The fluorescence titration plot of Fo/(F- Fo)
against 1/[Mn+] (M-1) based on 1:1 binding mode shows good
correlation and the association constant was found to be 5.42 x 105
by the ratio of intercept/slope (linearly dependent coefficient R2 =
0.9827) which is within the range 104–107 M-1 of other reported
reversible behavior of chemosensor
1 with Al3+ ions and then decomplexation with EDTA is shown in
Scheme 2. Therefore, chemosensor could be used as a reversible
1
for Al3+ ions. Complexation of
1
fluorescent as well as a colorimetric sensor for the detection of Al3+
ions. This on-off switching phenomenon could be repeated several
times by alternate Al3+ and EDTA additions.
sensors for Al3+ 33
complex between
.
This demonstrates the formation of strong
and Al3+.
1
Al3+
Al3+
HO
O
N
O
O
O
O
O
O
N
N
N
N
N
N
1
N
T
E
P
T
E
P
-
e
-
e
1 + Al3+
Fluorescence "ON"
Al(EDTA)-
Fluorescence "OFF"
Fig. 8: Benesi-Hildebrand plot for calculation of binding constant
between
and Al3+.
1
Scheme 2: Proposed sequential sensing process of Al3+ and EDTA
Thereafter, the detection limit was calculated from the fluorescence
titration data by plotting a graph between normalized fluorescence
intensity, (I - Imin)/(Imax -Imin) and log [Al3+] at 602 nm (Fig. 9) by the
Determination of Binding Constant and Detection limit
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reported methods .34-36 A linear curve ranging from 2.82 x 10-7 M to in intensity with the appearance of an isosbestic point at 452 nm,
2.5 x 10-6 M with the straight relationship was obtained. The which clearly indicates that there are two species in equilibrium. This
intercept at the ordinate axis corresponds to the detection limit of could be due to the existence of tautomeric form (II) i.e. the keto
3.55 x 10-7 M which is much lower than the tolerance limit of Al3+ in form of dye
1. At pH 1, the band at 401 nm disappeared completely
drinking water (1.85 x 10-3 M). Therefore, chemosensor
1
is sensitive and the band at 492 nm showed a strong bathochromic shift of 48
nm and appeared at 540 nm. These spectral changes were also
detected by the naked eye as the color of the solution changes from
yellow to violet-blue with the change of pH from basic to acidic range
(Fig. 11).
enough to monitor the quality of drinking water.
O
O
HO
O
O
O
N
O
N
O
N
H+
N
N
N
N
H
N
OH-
II
Hydrazone form (Keto form)
I
Azo form (Enol form)
Fig. 9: Plot of (I - Imin)/(Imax - Imin) vs log [Al3+] for the calculation of
minimum detection limit for
1.
Scheme 3: Two tautomeric structures of compound 1.
Effect of acid and base on chemosensor 1
Effect of pH on the UV-vis absorption spectra of
1 was investigated in
MeOH: H2O (1:1, v/v). pH of the solution was adjusted by adding an
appropriate amount of NaOH and HCl. The titration of chemosensor
at different pH suggested the existence of tautomerisation between
two species (I and II) as shown in Scheme 3. The compound exhibits
1
1
three absorption bands at 236 nm, 334 nm and 492 nm at pH 7 as
shown in Fig. 10. When pH of the solution was increased from 7 to
Fig. 11: Visual color changes observed in MeOH: H2O (1:1) solution
of
(1 x10-5 M) at different pH.
1
11,
a new broad band appeared at 401 nm which showed
Sensing with paper strips
hyperchromic shift (enhancement in intensity) and the band at 492
nm showed a hypochromic shift.
The practical utility of chemosensor
1 was explored by paper test
strips. Whatman filter papers were dipped in 1 x 10-3 M MeOH: H2O
(1:1, v/v) solution of for 15 minutes and then dried in air. The test
1
strips loaded with probe were then dipped in the Al3+ ion solution (1
x 10-3 M in MeOH : H2O, 1:1, v/v).
Fig. 10: Change in absorption spectra of compound
1
(1 x 10-5 M) in
MeOH in presence of acid and base.
Fig. 12: Color changes detected for
1 immobilized on Whatman filter
paper, dipped in (a) 1 x 10-3 M MeOH: H2O (1:1, v/v) solution of
1 (b)
Lowering the pH from 7 to 2 resulted in the diminishment of broad
band at 401 nm while the band at 492 nm showed an enhancement
1 x 10-3 M Al3+ ion solution in MeOH : H2O (1:1, v/v) (c) in 0.01 N of
aq. HCl (pH = 1) (d) Al3+ ion solution followed by EDTA.
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changes in 1H and 13C NMR spectra of
1 confirm that compound 1
(1mM) in MeOH : H2O (1:1, v/v). The yellow colored strip was exists in hydrazone form in acidic medium.
1
converted to pink when dipped in Al3+ ion solution (Fig. 12a). The Change in H NMR of
1 with the addition of base (10 μL NaOH) was
original yellow color of
1 could be regenerated by dipping pink strip also observed. There was a change in chemical shift of proton Hb in
in 1mM EDTA solution (Fig. 12c). Yellow colored strip changed to 1H NMR (shifted upfield from 6.425 ppm to 5.87 ppm) only due to
violet-blue when exposed to 0.01N aq. HCl solution (pH = 1) which the abstraction of hydroxyl proton as shown in Fig. 13(d). No other
allows selective sensing of highly acidic solution as well (Fig. 12b). significant changes were observed.
Development of such strips is so handy for instant on-site sensing
analysis which can also negate the dependency on instrumental
techniques.
Spectroscopic studies
NMR spectra in presence of aluminium
The binding ratio of
plot. The binding sites of chemosensor
recording 1H NMR spectra of in presence and absence of Al3+ in
1
and Al3+ has already been calculated by Job’s
and Al3+ were identified by
1
1
DMSO-d6. Significant changes were observed in the peak positions in
presence of Al3+ ions (Fig S2). One phenolic –OH proton at 11.55 ppm
in 1H NMR spectrum of
1
disappeared upon binding with Al3+ ions
which clearly indicates the coordination between aluminum and
oxygen atom as shown in Fig 13 (a and b). The aromatic protons of
sesamol ring at Ha = 7.0 ppm and Hb = 6.52 ppm shifted downfield
and upfield and appeared at 7.12 ppm and 6.26 ppm, respectively.
One methyl group of antipyrine ring showed a strong downfield shift
from 2.36 ppm to 2.68 ppm, clearly indicating the involvement of
carbonyl group of antipyrine with Al3+. These appreciable changes in
Fig. 13: 1H NMR spectra in DMSO-d6 of (a) neat
5 eq. Al3+; (c)
in presence of acid; (d) in presence of base.
1; (b) 1 in presence of
1
1
1H-NMR spectrum of
of
for Al3+ were hydroxyl group from sesamol, one nitrogen atom
1 primarily confirm that the coordinative cites
1
of the azo moiety and carbonyl oxygen of antipyrine ring.
NMR spectra in presence of acid and base
The 1H and 13C NMR spectra of chemosensor
recorded in presence of acid. 1H NMR spectra of
1
in DMSO-d6 were also
in presence of
1
acid (10 μL HCl) showed the clear disappearance of phenolic –OH
group suggesting the formation of keto form (II) in acidic media. This
Fig. 14: 13C NMR spectra in DMSO-d6 of (a) neat
1; (b) 1 in presence
was confirmed by the appearance of a new peak at 207.28 ppm in of acid.
13C NMR corresponding to the carbonyl carbon of sesamol ring as
FT-IR spectral behavior
shown in Fig. 14(b) (Fig S3). Furthermore, both aromatic protons of
Binding of chemosensor
1
with Al3+ has been further confirmed by IR
sesamol ring Ha = 7.0 ppm and Hb = 6.42 ppm shifted downward to
spectra. The v(O-H) broad band at 3448 cm-1 in free azo dye
disappeared when complexed with Al3+. The v(C=O) band at 1604
7.38 ppm and 6.78 ppm, respectively in 1H NMR
(Fig. 13(c)). These
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cm-1 for shifted to 1637 cm-1 after complex formation. The -N=N- was on (In1 = In2 = 0), fluorescence intensity of
1
1 at 613 nm was
stretching band at 1490 cm-1 also disappeared after binding with nearly zero (Output = 0) indicating ‘OFF’ state. On complexion with
Al3+. These notable changes in IR spectra clearly indicate the Al3+ (In1 = 1, In2 = 0), fluorescent intensity enhanced significantly
participation of –O-H, C=O and -N=N- groups in the binding of
Al3+ (Fig. 15).
1
with indicating ‘ON’ state of the system.
Both inputs Al3+ and EDTA2-, when present, failed to induce any
appreciable change in emission intensity at 613 nm i.e. ‘OFF’ state of
the system. Thus, In 2 inhibits the gate from responding to In1. All
these combinations lead to the construction of INHIBIT logic gate
shown in Fig. 16. Monomolecular circuit and truth table for this
proposed logic gate are shown in Fig. 16.
(a)
In1
In2
O1
(Al3+) (EDTA) F.I. at 613nm
0
1
0
1
0
0
1
1
0 (Low
1 (High
0 (Low)
0 (Low
)
TR
)
(b)
)
(a)
(b)
(c)
Fig. 16: (a) Fluorescence spectra of
Fig 15: IR spectra of (a) neat 1 (b) 1 .
in presence of Al3+
1
(1 x 10-5 M) in the presence of
different chemical inputs at λex = 450 nm in MeOH : H2O (1:1, v/v)
containing HEPES (0.01 mM, pH=7.2) buffer solution (b) Truth table
for sequential logic circuit. (c) Sequential logic circuit representing
the INHIBIT gate.
Application as Logic gate circuit
Logic gates have emerged as crucial building blocks in the formation
of combinational circuits. In this current work, we report a simple
two input based INHIBIT logic gate. It was observed that yellow
HOMO-LUMO analysis
solution of
1
turns pink upon complexion with Al3+. The original
-Al3+
The optimized structure of
by quantum chemical calculations at DFT using B3LYP/6311G basis
set is shown in Fig. 17. HOMO-LUMO analysis of (I, enol form)
1 and its tautomeric form (II) calculated
yellow color reappeared when EDTA2- was added to the
1
solution. However, the addition of EDTA2- alone did not produce any
1
color change.
revealed that the HOMO is mainly localized over antipyrine linked
with sesamol ring through azo linkage and LUMO is localized over
sesamol ring and azo linkage. Therefore, the charge transfer occurs
from the azo group to the sesamol ring with energy gap (ΔE) of -
0.12274 eV.
This enchanting “off–on” colorimetric behavior of ligand
1 allow us
to mimic the INHIBIT logic gate. An INHIBIT gate is nearly similar to
an AND gate with one input inverted by a NOT function. The
presence and absence of chemical inputs (In1 = Al3+ and In2 = EDTA2-
) were assigned with Boolean values ‘1’ (ON-state) and ‘0’ (OFF-
state), respectively. The output emission signals were monitored at
613 nm. The enhanced fluorescence of
1 was assigned as 1 (ON-
state) and the low fluorescence as 0 (OFF-state). When neither input
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as vmax cm-1. The NMR (1H and 13C) spectra were recorded on Jeol
JNM ECX-400P at 400 MHz and 100 MHz, respectively using TMS as
an internal standard. The mass spectrum was recorded on Agilent
6520 Q-TOF (ESI-HRMS) mass spectrometer having ESI source in
positive mode. Ultraviolet-visible (UV–vis) absorption spectra were
recorded on Analytikjena specord 250 Spectrophotometer. The
fluorescence spectra were measured at Cary Eclipse Fluorescence
Spectrophotometer. All spectroscopic measurements were done at
room temperature. The hybrid density function B3LYP (Becke–Lee–
Young–Parr composite of exchange-correction functional) method37
and the standard 6-311G basis set were used for structure
optimization. All the theoretical calculations are performed with
GAUSSIAN 09W software package.38
Fig. 17: Optimised structures and HOMO-LUMO diagrams of both
tautomeric forms (I & II) of chemosensor 1.
Sensing experiments
The stock solution of the sensor
1 was prepared in MeOH : H20 (1:1,
v/v, HEPES 0.01 mM, pH = 7.2) at the concentration of 1.0 x 10-3
M
However the HOMO-LUMO analysis of Keto form (II) indicates the
charge transfer occurs between antipyrine and sesamol rings with
the energy gap of -0.10107 eV (Fig. 17). Therefore, there is a less
charge transfer from HOMO to LUMO in case of enol form (azo form)
which implies more electron density is available for metal binding. In
case of keto form (hydrazone form) because of the low energy gap
(ΔE = -0.10107 eV), there is more charge transfer which means less
electron density is available for metal binding. Therefore,
and diluted to 1 x 10-5 M. The stock solutions of different metal salts
(Pb2+, Cu2+, Zn2+, Mn2+, Cd2+, Hg2+, Sr2+, Co2+, Sn2+, Fe3+, Al3+, Cr3+, La3+,
In3+, Th4+, Ni2+, Mg2+, Ca2+, Ba2+ and Na+) in HEPES (0.01 mM, pH =
7.2) of concentration 0.1 M were prepared and were diluted
accordingly before experimentation. While examining the sensing
behaviour of
1 with different metal ions, 3 mL stock solution was
taken and metal salt solution was added accordingly.
chemosensor
binding.
1 exists in its tautomeric form I (enol form) for metal
Procedure for the synthesis of compound 1
A solution of 4-Amino-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one
(0.5 g, 0.0024 mol) in water (10 mL) and conc. HCl (5 mL) was cooled
to 0-5oC in an ice bath. A solution of sodium nitrite (0.254g, 0.00368
mol) in water (10 mL) was added dropwise to the above solution.
The mixture was stirred for 45 min and disappearance of starting
material was observed by TLC using ethyl acetate: petroleum ether
(50: 50) as eluent. The diazonium chloride was then coupled with an
alkaline solution of sesamol (0.339 g, 0.00246 mol) in 10% NaOH
solution (10 mL) by slow addition over 30 min at 10-15oC. The
stirring was continued for 1 h at room temperature. A deep orange
solid was obtained which was filtered at pump and washed several
times with cold water (3 x 5 mL). The crude product was purified by
recrystallization from hot ethanol to give pure product as dark red
solid. The product was characterized by IR, 1H NMR and 13C NMR and
mass spectra.
Experimental
Reagents
4-Amino-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one (ampyrone)
and sesamol were purchased from Alfa-Aesar, HPLC water and
methanol from S.D. Fine. All the metal salts were in chloride form
while all the anions tested were the corresponding sodium salt. All
other reagents and solvents used in the synthesis and analysis were
of analytical reagent grade. All spectroscopic measurements were
performed in HEPES buffer solution (pH = 7.2).
Physical measurements
Melting point was recorded on a Tropical Lab equip apparatus (Buchi
M-560) and is uncorrected. IR (KBr) spectrum was recorded on
Perkin-Elmer FTIR spectrophotometer and the values are expressed
8 | J. Name., 2012, 00, 1-3
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4-((6-Hydroxybenzo[d][1,3]dioxol-5-yl)diazenyl)-1,5-dimethyl-2-
5. Z. Krejpcio and R.W. Wojciak, Pol. J. Environ. Stud. 2002,
11, 251–254.
phenyl-1H-pyrazol-3(2H)-one (1)
o
Dark red solid; Yield: 95 %; m.p.> 200 C; IR (KBr, cm-1): 3448, 1604,
6. E. Altschuler, Med. Hyp. 1999, 53, 22–23.
7. B. Wang, W. Xing, Y. Zhao, and X. Deng, Environ. Toxicol.
Pharmacol. 2010, 29, 308–313.
1
1521, 1490, 1458, 1417, 1325, 1203, 1028, 862; H NMR (DMSO-d6,
400 MHz): δ = 11.55 (1H, brs, OH, D2O exchangable), 7.42 (m, 2H),
7.32 (m, 1H), 7.23 (d, 2H), 7.0 (s, 1H), 6.42 (s, 1H), 5.88 (s, 2H), 3.20 (
s, 3H), 2.36 (s, 3H); 13C NMR (DMSO-d6, 100 MHz): δ = 169.7 (s),
157.4 (s), 152.5 (s), 151.0 (s), 136.8 (s), 133.8 (s), 129.3 (s, 2C), 127.8
(s), 125.9 (s, 2C), 122.8 (s), 101.9 (s), 100.0 (s), 93.4 (s), 34.8 (s, 3C),
9.74 (s, 3C); HRMS (ESI) calcd. for C18H16N4O4 [M + H]+ 353.1172,
found: 353.1241. (Fig S4-S7)
8. J.R. Walton, Neuro. Toxicol. 2006, 27, 385–394.
9. M. Baral, S.K. Sahoo and B.K. Kanungo, J. Inorg. Biochem.
2008, 102, 1581–1588.
10. Y. Donga, T. Liu, X. Wan, H. Pei, L. Wu and Y. Yao, Sens. and
Act. B 2017, 241, 1139–1144.
11. J. Y. Xie, C. Y. Li, Y. F. Li, Y. J. Fu, S. X. Nie and H. Y. Tan, Dyes
and Pigm. 2017, 136, 817-824.
Conclusion
12. S.J. Zhanga, H. Lia, C.L. Gong, J.Z. Wang, Z.Y. Wu and F.
Wang, Synth. Metals 2016, 217, 37–42.
In summary, we have designed and synthesized a new PET-based
“turn on” fluorescent as well as colorimetric chemosensor (
selective recognition of Al3+ ion. The addition of EDTA quenches the
fluorescence of could be used as a
+ Al3+ complex indicating that
1) for
13. B. Liu, P. F. Wang, J. Chai, X. Q. Hu, T. Gao, J. B. Chao, T.G.
Chen and B. S. Yang, Spectrochim. Acta Part A: Mol. and
Biomol. Spectro. 2016, 168, 98–103.
1
1
reversible “off-on-off” fluorescent sensor. The binding stoichiometry
suggests a 1:1 complexation with a large association constant for Al3+
ions. The detection limit was found to be sufficiently low to detect
14. J. Wang, Y. Li, N.G. Patel, G. Zhang, D. Zhou and Y. Pang,
Chem. Commun. 2014, 50, 12258–12261.
15. X. Wan, T. Liu, H. Liu, L. Gu and Y. Yao, RSC Adv. 2014,
4
,
,
,
micromolar concentrations of Al3+. Moreover, chemosensor
1 can
29479–29484.
also act as a “naked-eye” colorimetric sensor for the detection of H+
ions when pH < 2 because of the intramolecular charge transfer.
Based on these characteristics, one logic gate circuit was
constructed. Therefore, the novel chemosensor can be used as a
color-tunable pH sensor in highly acidic environment as well as an
excellent fluorescent sensor for the detection of Al3+ ion.
16. S. Paul, A. Manna and S. Goswami, Dalton Trans. 2015, 44
11805-11810.
17. C. Fleischmann, M. Lievenbrück, H. Ritter, Poly. 2015,
7
717-746.
18. M. Gaber, A.M. Hassanein and A.A. Lotfalla, Jourl. of Mol.
Struc. 2008, 875, 322–328.
19. A.Z. El-Sonbati, G.G. Mohamed, A.A. El-Bindary, W.M.I.
Hassan, and A.K. Elkholy, Jour. of Mol. Liq. 2015, 209, 625–
634.
Acknowledgments
GB thanks CSIR, New Delhi, India for the grant of Junior Research
Fellowship. The authors also thank Gaussian for providing us
Gaussian 09 software.
20. A.Z. El-Sonbati, M.A. Diab, A.A. El-Bindary, A.M. Eldesoky
and Sh.M. Morgan, Spectrochim. Acta Part A: Mol. and
Biomol. Spect. 135, 774–791.
References
21. H.J. Mohammed, B.J. Kadhim and A. S. Mohammed, E.
Jour. of Chem., 2011, 8(2), 739-747.
1. N.W. Baylor, W. Egan and P. Richman, Vacc. 2002, 20, 18–
23.
22. M.A. Metwally, A. Metwally, E.A. Galil, and F.A. Amer,
Monat. fṻr Chemie, 2008, 139, 35–42.
2. M.G. Soni, S.M. White, W.G. Flamm, and G.A. Burdock,
Regul. Toxicol. Pharm. 2001, 33, 66–79.
23. S.N. Chaulia, Der Pharma Chemica 2016, 8(3), 254-272.
24. L. H. Nair and A.S. Appukuttan, Journ. of the Kor. Chem.
Soc. 2012, 56, 217-227.
3. E. Delhaize and P. Ryan, Plnt. Physiol., 1995, 107, 315–321.
4. J. Barcelo and C. Poschenrieder, Environ. Exp. Bot., 2002,
48, 75–92.
This journal is © The Royal Society of Chemistry 20xx
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Page 10 of 11
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ARTICLE
25. A. Z. E. Sonbati, G.G. Mohamed, A. A. E. Bindary, W. M. I.
Journal Name
Hassan and A.K. Elkholy, Jour. of Mol. Liq. 2015, 209, 625–
634.
26. M. Gaber, A.M. Hassanein and A.A. Lotfalla, Jour. of Mol.
Struc. 2008, 875, 322–328.
27. K. Aggarwal and J. M. Khurana, Jour. of Lumin. 2015, 167
,
146–155.
28. K. Aggarwal and J. M. Khurana, Jour. of Lumin. 2017, 187
,
457-465.
29. H. Singh, J. Sindhu and J. M. Khurana, Sens. and Acut. B:
Chem. 2014, 192, 536-542.
30. H. Rau, Angew Chem. Int. Ed. Engl. 1973, 12, 224-235.
31. A. Cembran, F. Bernardi, M. Garavelli, L. Gagliardi and G.
Orlandi, J. Am. Chem. Soc. 2004, 3, 234-43.
32. H.A. Benesi, and J.H. Hildebrand, J. Am. Chem. Soc. 1949,
71, 2703.
33. M. Shortreed, R. Kopelman, M. Kuhn and B. Hoyland, Anal.
Chem. 1996, 68, 1414.
34. M. Shortreed, R. Kopelman, M. Kuhn and B. Hoyland, Anal.
Chem. 1996, 68, 1414.
35. W. Lin, L. Yuan, L. Long, C. Guo and J. Feng, Adv. Funct.
Mater. 2008, 18, 2366.
36. A. Caballero, R. Martınez, V. Lloveras, I. Ratera, J. V.
Gancedo, K.Wurst, A. Tarraga, P. Molina and J. Veciana, J.
Am. Chem. Soc. 2005, 127, 15666.
37. A.D. Becke, J. Chem. Phys. 1993, 98, 5648.
38. M.J. Frisch, G.W. Trucks, H.B. Schlegal, et al., Gaussian 09,
Revision A.02, Gaussian Inc., Wallingford CT, 2009.
10 | J. Name., 2012, 00, 1-3
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Graphical Abstract
An Ampyrone based azo dye as pH-responsive and chemo-reversible colorimetric
fluorescent probe for Al3+ in semi-aqueous medium: Implication towards logic gate
analysis
Gaurav Bartwala, Komal Aggarwala and Jitender M. Khuranaa,*
aDepartment of Chemistry, University of Delhi, Delhi-110007, India
*Corresponding author. Tel.: +91 11 2766772; fax: +91 11 27667624
E-mail addresses: jmkhurana1@yahoo.co.in