Journal of Photochemistry & Photobiology, A: Chemistry 403 (2020) 112836
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Journal of Photochemistry & Photobiology, A: Chemistry
journal homepage: www.elsevier.com/locate/jphotochem
Rhodamine-Based Arylpropenone Azo Dyes as Dual Chemosensor for Cu2+/
Fe3+ Detection
Akın Sağırlı a, Ebru Bozkurt b, *
a
b
Department of Chemistry, Bolu Abant İzzet Baysal University, 14280 Bolu, Turkey
Program of Occupational Health and Safety, Vocational College of Technical Sciences, Atatürk University, 25240 Erzurum, Turkey
A R T I C L E I N F O
A B S T R A C T
Keywords:
Rhodamine
Cu
Fe
Colorimetric
Fluorometric
Dual sensor
A novel chemosensor APA-Rh based on rhodamine ring was developed for detection of Cu2+ and Fe3+ ions. For
this purpose, the optical properties of the chemosensor APA-Rh were investigated in DMSO:H2O (4:1, v/v) in the
presence of different metal ions such as Li+, Na+, K+, Ag+, Mg2+, Ca2+, Ba2+, Cd2+, Zn2+, Cu2+, Hg2+, Cr2+,
Pb2+, Fe2+, Mn2+, Co2+, Fe3+, Cr3+, and Al3+. The chemosensor APA-Rh exhibited high selectivity and sensi­
tivity for Cu2+ and Fe3+ ions among other metal ions. Detection limit (LOD), interaction stoichiometry and
association constant values were calculated for Cu2+ and Fe3+ ions. LOD values for Cu2+ and Fe3+ were 1.04 μM
and 0.91 μM, respectively. It was also found that the response time of APA-Rh was as low as 0.5 min and the
other metal ions did not cause interference for detection of Cu2+ and Fe3+ ions. The results showed that the new
chemosensor APA-Rh is a both colorimetric and fluorometric reversible dual sensor for Cu2+ and Fe3+ ions.
1. Introduction
Developments of fluorescent probes for determination of transition
metal ions have been receiving an increasing interest in past decades
[1–5]. Although these ions are well known to play a significant role in
biological processes in living organisms, they are also extremely harmful
to the environment [6–10]. Among these metals, iron and copper that
are two of the most abundant metals in earth crust, are extensively used
in the field of chemistry, biology and industry [11,12].
Cu2+ ion is of great importance for being a part of various biological
and physiological processes [13]. However, excess intake of Cu2+ ion
may cause the accumulation of Cu in human body that brings some
serious neurodegenerative diseases (Alzheimer, Wilson, Menkes) as well
as liver or kidney damage [14,15]. Moreover, it has an extremely toxic
impact on environment as metal pollutant due to its widespread use
[16].
On the other hand, Ferric ion (Fe3+) is considered to be an essential
ion for different metabolic systems in most of the living organisms such
as carrying oxygen in HEME and as a cofactor in many enzymatic re­
actions [17]. Meanwhile, its overdose or deficiency can cause multiple
disorders in human body, especially Parkinson, Alzheimer, Huntington,
Anemia and some type of cancers [18–20].
In this regard, it is somewhat vital to detect these cations in living
systems as well as the environment. Therefore, designing a rapid and
highly selective chemosensor for simultaneous detection of Cu and Fe
metals is highly desirable [21,22]. So far, various flourescent chemo­
sensors have been developed to detect the trace amounts of Cu and Fe
ions in an analyte with high sensitivity [23–25]. But emerging of new
chemosensor candidate for sensing both Cu and Fe ions is still a chal­
lenge. For this purpose, rhodamine-based dyes seem to be an interesting
fluorophore due to its excellent photophysical property such as high
quantum yield, large extension coefficient and photostability [6,7]. So, a
new rhodamine derivative was designed to detect both Cu and Fe ions in
our study.
In the present study, we described arylpropenone azo dye appended
rhodamine-based dual chemosensor, 3’,6’-bis(diethylamino)-2-((E)((E)-3-oxo-2-(2-(p-tolyl)hydrazono)-3-(4-(trifluoromethyl)phenyl)pro­
pylidene)amino)spiro[isoindoline-1,9’-xanthen]-3-one
(APA-Rh),
capable of selective sensing Cu2+ and Fe3+ ions without any interference
of other metals. The structure of intermediate and chemosensor APA-Rh
was fully characterized by means of IR, 1H NMR, 13C NMR and TOF-MS
spectral data.
* Corresponding author.
E-mail address: ebrubozkurt@atauni.edu.tr (E. Bozkurt).
https://doi.org/10.1016/j.jphotochem.2020.112836
Received 29 February 2020; Received in revised form 4 August 2020; Accepted 5 August 2020
Available online 7 August 2020
1010-6030/© 2020 Elsevier B.V. All rights reserved.
A. Sağırlı and E. Bozkurt
Journal of Photochemistry & Photobiology, A: Chemistry 403 (2020) 112836
Scheme 1. The synthesis arylpropenone azo disperse dye.
2. Experimental
pellets or neat on NaCl plates for liquids and were recorded on a SHI­
MADZU FTIR-8400S spectrophotometer. NMR spectra were recorded on
Jeol spectrometer operating at 400 MHz for 1H and at 100 MHz for 13C,
all at 25 ◦ C, as specified for each data set. HRMS spectra were obtained
from Agilent ZQ instrument.
All chemical shifts are reported in ppm downfield from TMS.
Coupling constants (J) are reported in Hz. Routine TLC analyses were
carried out on pre-coated silica gel plates with fluorescent indicator.
Flash column chromatography was performed on silica gel (230-400
Mesh ASTM. Stain solutions of potassium permanganate and 2,4-DNP
were used for visualization of the TLC spots.
2.1. Materials
Ethanol and LiCl, NaCl, KCl, AgCH3COO, MgCl2.6H2O, CaCl2.2H2O,
BaCl2.2H2O, CdCl2, ZnCl2.H2O, CuCl2.2H2O, HgCl2, CrCl2, Pb
(CH3COOH)2.3H2O, FeSO4.7H2O, MnCl2.4H2O, CoCl2.6H2O, CrCl3,
FeCl3, and AlCl3 as the metal ion sources were obtained from Sigma. A
stock solution of the chemosensor APA-Rh was prepared in chloroform
at 1.0 × 10-3 M. A certain amount of fresh the chemosensor APA-Rh
samples in aqueous solution were made ready from this stock solution by
evaporating chloroform. The final concentration of the chemosensor
APA-Rh was 40 μM for all measurements. All the experiments were
performed at room temperature.
2.3. Synthesis of Arylpropenone Azo Disperse Dye
A cooled aqueous solution of diazonium tetrafluoroborate salt 2
[28–31] (1.5 equiv.) at 0 ◦ C was added into a solution of NaOAc (3.0
equiv.) and dimethylamino-4-(trifluoromethyl)phenylpropenone 1 [32,
33] (1.0 equiv.) in DCM (15 mL). The resulting mixture was stirred at RT
for 2 h, the resulting precipitate was filtered off using sintered funnel via
suction filtration and dried under high-vacuum to afford corresponding
azo disperse dye (3) as a solid (Scheme 1). Solid residue of disperse dye
(3) was further purified by flash CC using mixtures of hexanes-EtOAc
and obtained in pure state as an orange solid. (0.856 g, 60%), m.p.
114-116 ◦ C; Rf (50% EtOAc/hexane) 0.70; IR (KBr) υ: 3117 (NH), 3016,
2924, 1643 (C = O), 1527, 1419, 1327, 1288, 1165, 1118, 1072, 956,
810 cm-1; 1H-NMR (400 MHz, CDCl3) δ: 10.17 (1H, s, CHO), 8.02-8.00
(2H,d, J 8.2 Hz), 7.74-7.72 (2H,d, J 8.5 Hz), 7.19 (4H, s), 2.34 (3H,s);
13
C-NMR (100 MHz, CDCl3) δ: 190.3 (C = O), 189.1 (C = O), 138.6,
137.3, 133.8-132.9 (2JCF(ortho) =32.6 Hz), 130.6, 130.3, 130.1, 129.1,
124.9-124.8 (3JCF(meta) =3.8 Hz), 125.2-122.5 (1JCF =272.5 Hz),
119.5, 116.7, 21.0; (TOF-MS ESI-) m/z: 333
2.2. Apparatus
The UV-Vis. absorption and fluorescence spectra of the samples were
recorded using Shimadzu UV-3600 Plus UV-VIS-NIR Spectrophotometer
and Agilent Technologies Cary Eclipse Fluorescence Spectrophotometer,
respectively. For the fluorescence measurements, the solutions were
excited at 540 nm and their fluorescence intensities were recorded be­
tween 550-700 nm, respectively.
Fluorescence quantum yields of the samples were calculated by using
Parker-Rees equation (Equation 1).
( )( 2 )(
)
DS
ηs
1 − 10− ODr
∅s = ∅r
(1)
2
−
OD
Dr
ηr
1 − 10 s
where D is the integrated area under the corrected fluorescence spec­
trum, n is the refractive index of the solution, and OD is the optical
density at the excitation wavelength (λexc= 540 nm). The subscripts s
and r refer to the sample and reference solutions, respectively [26].
Rhodamine 101, which has a quantum yield of 1.0 in methanol, was
chosen as the reference [27].
Melting points were determined on a Meltemp melting point appa­
ratus and are uncorrected. Infrared spectra were obtained from KBr
2.4. Synthesis of compound APA-Rh (chemosensor)
The rhodamine B hydrazide 5 was prepared according to previous
report [34]. Then, a mixture of rhodamine B hydrazide 5 (0.4676 g,
Scheme 2. The synthetic pathway of chemosensor APA-Rh.
2
A. Sağırlı and E. Bozkurt
Journal of Photochemistry & Photobiology, A: Chemistry 403 (2020) 112836
Fig. 1. Absorption and fluorescence spectra of APA-Rh (40 μM) in DMSO:H2O (4:1, v/v) (λexc = 540 nm).
1.0 mmol) and arylpropenone azo disperse dye 3 (0.334 g, 1.0 mmol) in
absolute ethanol was refluxed for 12 hours to obtain a yellow precipi­
tate. Next, the precipitate was filtered and washed three times with cold
ethanol (Scheme 2). The residue was dried to give compound APA-Rh in
63% yield. m.p. 256-258 ◦ C; IR (KBr) υ: 2967 (aliphatic CH), 1687, 1632
(C = O), 1610, 1514, 1406, 1305, 1254, 1217, 1118, 1064, 867, 814
cm-1; 1H NMR (400 MHz,CDCl3) δ 8.96 (s, 1H, C = NH), 8.00 (d, J
=6.6 Hz, 1 H), 7.91 (d, J =8.1 Hz, 2 H), 7.62 (d, J =8.2 Hz, 2 H), 7.55 –
7.43 (m, 2 H), 7.11 (d, J =7.7 Hz, 1 H), 7.06 (d, J =8.3 Hz, 2 H), 6.98 (d,
J =8.3 Hz, 2 H), 6.54 (d, J =8.8 Hz, 2 H), 6.47 (d, J =2.1 Hz, 2 H), 6.27
(dd, J = 8.9, 2.1 Hz, 2 H), 3.31 (q, J =6.9 Hz, 8H, NCH2), 2.29 (s, 3H,
CH3), 1.13 (t, J =7.0 Hz, 12H, NCH3).; 13C NMR (101 MHz, CDCl3) δ
189.94(C = O, ketone), 164.93(C = O, lactam), 153.10, 149.17, 142.93,
141.53, 140.30, 134.21, 134.01, 130.75, 130.51, 130.00, 128.59,
128.14, 124.48, 124.44, 124.41, 124.37, 124.05, 123.54, 115.88,
108.28, 104.64, 98.12, 77.31(spiro C), 44.42 (NCH2), 21.05 (CH3),
12.68 (NCH3). HRMS (+APCl-TOF) calcd for C45H44F3N6O3 [M+H]+
773.3427, found 773.3422
line in fluorescence titration experiment. Moreover, the association
constants were calculated with Benesi-Hildebrand equation (Equation
2):
1
1
1
=
+
F − F0 KS (Fmax − F0 )[M x+ ]n Fmax − F0
(2)
where F0, F, and Fmax are the fluorescent intensity of molecule in the
absence of metal ion, at a certain concentration of metal ion and at a
complete interaction concentration of metal ion, respectively. [Mx+] is
the concentration of ion, n is the binding stoichiometry for dye and
metal ion [35].
3. Result and discussion
3.1. Synthesis of chemosensor APA-Rh
Initially, the starting material, arylpropenone azo disperse dye 3,
was synthesized by the azocoupling reaction of dimethylamino-4(trifluoromethyl)phenylpropenone 1 with diazonium tetrafluoroborate
salt 2 in good yield (Scheme 1). This was followed by the condensation
reaction of Rhodamine B hydrazide 5 and arylpropenone azo disperse
dye 3 gave rise to the formation of the chemosensor APA-Rh which was
precipitated out of ethanol in pure state (Scheme 2). Spectral data for all
synthesized compounds can be found in supplementary material (Figs.
S1-S8).
2.5. The sensing of metal ions
1.0 × 10-2 M stock solutions of all metal ions (Li+, Na+, K+, Ag+,
Mg2+, Ca2+, Ba2+, Cd2+, Zn2+, Cu2+, Hg2+, Cr2+, Pb2+, Fe2+, Mn2+,
Co2+, Cr3+, Fe3+ and Al3+) were prepared in pure water. Then, 200 μL of
metal ion solution was added to 5 mL DMSO:H2O (4:1, v/v) solution of
the chemosensor APA-Rh having 40 μM concentration at room tem­
perature. The absorption and fluorescence measurements were recorded
for the spectroscopic changes in the chemosensor APA-Rh. In addition,
Cu2+ and Fe3+ ions with different concentrations were also prepared for
the fluorescence and absorption titration experiments. Absorption and
fluorescence measurements were conducted for each solution contain­
ing Cu2+, and Fe3+. The fluorescence data were used to determine
detection limits of Cu2+, and Fe3+. For this purpose, 3 s/k equation was
used, where s is the standard deviation of blank, k is the slope of the fit
3.2. The effect of various metal ions on the photo-physical properties of
the chemosensor APA-Rh
The optical behavior of the chemosensor APA-Rh were investigated
in DMSO:H2O (4:1, v/v) by using UV-Vis. absorption and fluorescence
measurements. It was observed that although the chemosensor APA-Rh
had three absorption bands at 278, 315 and 432 nm in DMSO:H2O (4:1,
v/v), it exhibited very weak fluorescence property due to the spirocyclic
3
A. Sağırlı and E. Bozkurt
Journal of Photochemistry & Photobiology, A: Chemistry 403 (2020) 112836
Fig. 2. (a) Absorption spectra of APA-Rh (40 μM) in the absence and presence of 40 μM metal ions in DMSO:H2O (4:1, v/v). (b) Photographs of APA-Rh (40 μM) in
the presence of metal ions under day light.
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Journal of Photochemistry & Photobiology, A: Chemistry 403 (2020) 112836
Fig. 3. Fluorescence spectra of APA-Rh (40 μM) in the absence and presence of 40 μM metal ions in DMSO:H2O (4:1, v/v) (λexc = 540 nm).
form in its molecular structure (Fig. 1). After determining the optical
properties of the newly synthesized rhodamine derivative APA-Rh, the
effect of different charged metal ions on its optical properties was
investigated. The absorption and fluorescence spectra of the chemo­
sensor APA-Rh were recorded in the presence of nineteen different
metal ions (Li+, Na+, K+, Ag+, Mg2+, Ca2+, Ba2+, Cd2+, Zn2+, Cu2+,
Hg2+, Cr2+, Pb2+, Fe2+, Mn2+, Co2+, Fe3+, Al3+ and Cr3+). 40 μM of each
metal ions were added to the solutions with 40 μM APA-Rh and the
absorption and fluorescence measurements of these samples were taken
in DMSO:H2O (4:1, v/v). The absorption characteristic of the chemo­
sensor APA-Rh did not change in the presence of all ions except for Cu2+
and Fe3+ ions (Fig. 2a). However, as shown in Fig. 2a, a new peak in the
absorption spectra of APA-Rh was detected at 562 nm in the presence of
Cu2+ ions. In the presence of Fe3+ ions, it was observed that the char­
acteristic absorption bands of APA-Rh disappeared and a shoulder
formed at 342 nm (Fig. 2a). This change in the absorption spectrum of
APA-Rh was also observed by the naked eye. The color of the solution
changed from light yellow to red in the presence of Cu2+ ions as seen in
the daylight photograph of Fig. 2b. It was also observed that the color of
the solution changed from light yellow to light red in the presence of
Fe3+ ions (Fig. 2b). This results showed that structural changes occurred
in the ring-opened form of spirolactam [36,37].
The fluorescence spectra of the chemosensor APA-Rh in the presence
of various metal ions were also recorded in DMSO:H2O (4:1, v/v). As
seen in Fig. 3, while APA-Rh presented very weak fluorescence property
in the presence of other metal ions, it had a new and strong fluorescence
peak at 595 nm in the presence of Cu2+ ions. APA-Rh also showed a new
and strong fluorescence peak at 589 nm in the presence of Fe3+ ions.
These results indicated that the chemosensor APA-Rh had high selec­
tivity towards Cu2+ and Fe3+ ions as both colorimetrically and fluoro­
metrically. The effect of metal ions on the fluorescence quantum yield of
APA-Rh was determined by using equation (1). The fluorescence
quantum yield value of APA-Rh was calculated to be 0.02 in DMSO:H2O
(4:1, v/v). This value for APA-Rh did not change in the presence of other
ions except Cu2+ and Fe3+ ions. However, the fluorescence quantum
yield values of the chemosensor APA-Rh significantly increased in
presence of Cu2+ and Fe3+ ions (Φ = 0.57 Cu2+ for, Φ = 0.40 for Fe3+).
These significant increases in fluorescence quantum yield values of APARh in presence of Cu2+ and Fe3+ ions confirmed that the Cu2+ and Fe3+
ions increased fluorescence property of the chemosensor APA-Rh.
3.3. Detection of Cu2+ and Fe3+ ions with the chemosensor APA-Rh
Cu2+ and Fe3+ ions were detected with the changes in the absorption
and fluorescence spectra of APA-Rh. For this purpose, titration experi­
ments were performed using different concentrations of Cu2+ and Fe3+
ions. When Cu2+ ions at different concentrations (0-40 μM) were added
to the chemosensor APA-Rh solution, it was observed that the intensity
of the new absorption peak of APA-Rh detected at 562 nm increased
depending upon the concentration of Cu2+ ions (Fig. 4a). The fluores­
cence titration experiments showed that the fluorescence peak of APARh at 595 nm increased with Cu2+ ion concentration (Fig. 4b). It was
also found that Fe3+ ions (0-40 μM) behaved in similar fashion to Cu2+
ions. It was determined that the shoulder at 342 nm in the absorption
band and fluorescence peak intensity at 589 nm of APA-Rh increased
with increased concentration of Fe3+ ions (Figs. S9a and S9b).
The detection limit values (LOD) of APA-Rh for Cu2+ and Fe3+ ions
were calculated using the results of fluorescence titration experiments.
The fluorescence intensity of APA-Rh at 595 nm showed good linear
increase depending on the concentration of Cu2+ ions ranging from 0-40
μM (Fig. 5). The LOD for Cu2+ was calculated as 1.04 μM. This value was
well below the limit value permitted (20 μM) by the US EPA, showing
that the new rhodamine derivative sensor had high sensitivity [38].
Similar calculations were also made to determine the detection limit of
Fe3+ ions with APA-Rh. The LOD for Fe3+ was found as 0.91 μM (Fig.
S10). The association constants with Cu2+ and Fe3+ for APA-Rh were
determined by Job’s method. Job’s plot was generated by plotting AJob
or FJob against Xion, AJob or FJob = (1 − Xion )(A or F − A0 or F0 ) and Xion is
mole fraction of the detected ion [39]. The stoichiometry ratios between
APA-Rh and ions were 2:1 and 1:2 for Cu2+ and Fe3+ respectively, based
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A. Sağırlı and E. Bozkurt
Journal of Photochemistry & Photobiology, A: Chemistry 403 (2020) 112836
Fig. 4. (a) Absorption and (b) fluorescence spectra of APA-Rh (40 μM) with the increasing concentration of Cu2+ (λexc = 540 nm).
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Journal of Photochemistry & Photobiology, A: Chemistry 403 (2020) 112836
Fig. 5. Change fluorescence intensity of APA-Rh (40 μM) with the increasing concentration of Cu2+.
Fig. 6. Job’s plot of APA-Rh with Cu2+ in DMSO:H2O (4:1, v/v).
on the Job’s plot (Figs. 6 and S11). The association constants were found
as 67.01 M-1 and 1.57 × 103 M-2 for Cu2+ and Fe3+ respectively, from the
slope of the Benesi-Hildebrand graphs (Figs. 7 and S12).
The interfering effect of 17 metal ions (Li+, Na+, K+, Ag+, Mg2+,
2+
Ca , Ba2+, Cd2+, Zn2+, Hg2+, Cr2+, Pb2+, Fe2+, Mn2+, Co2+, Al3+ and
Cr3+) on the absorption and fluorescence properties of the chemosensor
APA-Rh was investigated to check the possible interference of other
metal ions. The results showed that none of the competing ions affected
the Cu2+ and Fe3+ ion colorimetrical selectivity of APA-Rh (Figs. 8a and
S13a). However, it was determined that APA-Rh has high fluorometri­
cally selectivity for Cu2+ and Fe3+ ion in the presence of other
competing ions except Hg2+, Cr2+, and Pb2+ (Figs. 8b and S13b). It was
suggested that this new chemosensor would be a good sensor system for
the selectively detection of Cu2+ and Fe3+ ions without interfering with
the other ions.
Reversibility is a very important parameter for colorimetric or fluo­
rometric sensors. EDTA tests were performed to determine the revers­
ibility of the newly synthesized chemosensor APA-Rh. As depicted in
Fig. 9, by the addition of EDTA (40 μM) to APA-Rh solution in the
presence of Cu2+, the new absorption peak observed at 562 nm of APARh disappeared. In experiments for Fe3+, it was seen that the increasing
fluorescence intensity of APA-Rh in the presence of Fe3+ decreased by
the addition of EDTA to the solution (Fig. S14). These results demon­
strated the reversible interactions between APA-Rh, Cu2+ and Fe3+ ions.
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Journal of Photochemistry & Photobiology, A: Chemistry 403 (2020) 112836
Fig. 7. Benesi-Hildebrand plot based on a 1:2 association stoichiometry between Cu2+and APA-Rh.
The ion detection response time of the novel chemosensor APA-Rh
was also investigated. The fluorescence measurements for APA-Rh were
performed between from 0.5 min to 10 min for both Cu2+ and Fe3+ ions.
It was observed that fluorescence intensity of APA-Rh for both ions
reached maximum value in 0.5 min and then remained constant (Fig. 10
and S15). These results showed that this new sensor had a very short
response time.
3.5. Comparison with other sensors
3.4. Metal ion sensing mechanism
4. Conclusions
Sensing performance of APA-Rh was compared with other studies in
the literature. The comparison results in terms of their binding constant,
limit of detection, sensing ions, response time were summarized in
Table 1. According to the data obtained with APA-Rh similar results or
values were obtained with these parameters in Table 1 supporting the
previous literatures [21,22,40–42]
2+
The interaction between the chemosensor APA-Rh with Cu and
Fe3+ was determined by 1H NMR measurements. In the examination of
NMR spectrum of APA-Rh in CDCl3, all proton signals were observed
except NH proton which was possibly caused by the fast tautomeric
equilibration in CDCl3 as depicted in Scheme 3. However, when it was
run in DMSO-d6, NH signal appeared at 13.4 ppm as singlet surprisingly.
Therefore, all NMR titration experiments were recorded in DMSO-d6/
D2O (5:1, v/v) mixture because, the NH signal is not only necessary for
structural elucidation of APA-Rh but also it is vital for clarifying which
N atom on APA-Rh coordinated upon the addition of Cu2+ or Fe3+ ion.
On the addition of 0.5 equiv. Cu2+ ion, the NH signal disappeared while
imine proton shifted down to 9.16 ppm (Fig. 11). This clearly confirms
the opening of lactam ring and interaction of Cu2+ with the APA-Rh.
Upon the addition of 2.0 equiv. Fe3+ ion onto the APA-Rh, iminic NH
signal shifted up to 9.20 ppm due to increasing electron density on
iminic nitrogen atom. This explains no contribution of iminic nitrogen
on binding Fe3+ atom. Also any decrease and shift in the NH signal to
further downfield region indicates direct coordination between NH ni­
trogen and Fe3+ ion. Furthermore, aromatic proton signals shifted to
downfield region with broadening of the peak (marked as b,c,e,d,f,g,h)
which verifies the binding of Fe3+ ion to the probe APA-Rh without ring
opening of lactam (Fig. S16). The suggested mechanism for the inter­
action of the chemosensor APA-Rh with Cu2+ and Fe3+ was presented in
Scheme 4.
In this study, a novel rhodamine derivative (chemosensor APA-Rh)
was synthesized and its sensor property was examined. The structural
and optical characterization of APA-Rh was performed by IR, 13C and 1H
NMR, HRMS, absorption and fluorescence spectroscopic techniques. The
absorption and fluorescence spectra showed that only Cu2+ and Fe3+
ions among 19 different cations caused a change in the optical properties
of APA-Rh. Based on these changes, LOD, interaction stoichiometry and
association constants were calculated for the ions detected. LOD values
for Cu2+ and Fe3+ were 1.04 μM and 0.91 μM, respectively. The inter­
ference studies in the presence of competitive ions and the reversibility
studies with EDTA tests were also conducted for Cu2+ and Fe3+ ions.
These studies showed that no competitive ion interfered and APA-Rh
was a reversible sensor. It was also determined that the response time of
APA-Rh for Cu2+ and Fe3+ ions was as short as 0.5 min. Furthermore,
the interaction mechanism between Cu2+ and Fe3+ ions and the che­
mosensor APA-Rh was explained by using 1H NMR measurements.
These results were suggested that APA-Rh was both fluorometric and
colorimetric dual chemosensor.
CRediT authorship contribution statement
Akın Sağırlı: Visualization, Conceptualization, Methodology,
Writing - original draft. Ebru Bozkurt: Data curation, Visualization,
8
A. Sağırlı and E. Bozkurt
Journal of Photochemistry & Photobiology, A: Chemistry 403 (2020) 112836
Fig. 8. (a) Absorption and (b) fluorescence metal ion selectivity profiles of APA-Rh for Cu2+ in the presence of various metal ions in DMSO:H2O (4:1, v/v).
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Journal of Photochemistry & Photobiology, A: Chemistry 403 (2020) 112836
Fig. 9. Absorbance spectra of APA-Rh in the presence of Cu2+ ion (40 μM) and EDTA (40 μM) in DMSO:H2O (4:1, v/v).
Fig. 10. Fluorescence enhancing profile of addition Cu2+ to APA-Rh in DMSO:H2O (4:1, v/v) from 0.5 min to 10 min.
Investigation, Methodology, Writing - review & editing.
Declaration of Competing Interest
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influence
the work reported in this paper.
Appendix A. Supplementary data
Scheme 3. Hydrazone-Azo type tautomerization.
Supplementary material related to this article can be found, in the
online version, at doi:https://doi.org/10.1016/j.jphotochem.2020.
112836.
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Journal of Photochemistry & Photobiology, A: Chemistry 403 (2020) 112836
Fig. 11. 1H NMR spectra of APA-Rh and APA-Rh+0.5 eq Cu2+ in DMSO-d6 and DMSO-d6:D2O (5:1, v/v) solution respectively.
Scheme 4. Proposed reversible reaction mechanism of Cu2+ and Fe3+ binding with APA-Rh.
Table 1
Comparison of some Cu2+ and Fe3+selective chemosensors.
Ref
Binding Constant
Detection Limit(μM)
Sensing Ions
Response Time (min)
[21]
[22]
[39]
[40]
[41]
APA-Rh(This work)
1.804 × 103 M-1 for Cu2+ and 7.32 × 104 M-1 for Fe3+
13.99 × 10-2 M for Cu2+ and 1.3 × 10-2 M for Fe3+
1.9575 × 105 M-1 for Cu2+ and 1.9262 × 105 M-1 for Fe3+
4.94 × 103 M-1 for Cu2+ and 1.92 × 103 M-1 for Fe3+
67.01 M-1 for Cu2+ and 1.57 × 103 M-2 for Fe3+
0.5264 for Cu2+ and 0.00463 for Fe3+
0.018 for Cu2+ and 0.033 for Fe3+
0.448 for Cu2+ and 0.109 for Fe3+
0.188 for Cu2+ and 0.0252 for Fe3+
0.12 for Cu2+ and 0.11 for Fe2+
1.04 for Cu2+ and 0.91 for Fe3+
Cu2+ and Fe3+
Cu2+ and Fe3+
Cu2+ and Fe3+
Cu2+ and Fe3+
Cu2+ and Fe2+
Cu2+ and Fe3+
1.0 for both ions
0.5 for both ions
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