Colorimetric and fluorescence signalling of thioesculetin in presence of oxidising agent

Article abstract of DOI:10.1007/s12039-018-1440-5

Abstract: Thioesculetin (TE) is a sulfur analogue of esculetin. The UV-Vis absorption maximum of TE at 470 nm shifted to 357 nm in the presence of oxidising agent such as m-chloroperoxy benzoic acid (m-CPBA). With gradual increase in the m-CPBA concentrat

Full text of DOI:10.1007/s12039-018-1440-5

J. Chem. Sci. (2018) 130:34
© Indian Academy of Sciences
https://doi.org/10.1007/s12039-018-1440-5
REGULAR ARTICLE
Colorimetric and fluorescence signalling of thioesculetin in
presence of oxidising agent
RUPALI G SHINDEa,b, AYESHA A KHANa and ATANU BARIKb,∗
aDepartment of Chemistry, Savitribai Phule Pune University, Pune, Maharashtra 411 007, India
bRadiation and Photochemistry Division, Bhabha Atomic Research Centre, Mumbai, Maharashtra 400 085,
India
E-mail: atanu@barc.gov.in
MS received 15 January 2018; revised 27 February 2018; accepted 27 February 2018
Abstract. Thioesculetin (TE) is a sulfur analogue of esculetin. The UV-Vis absorption maximum of TE at 470
nm shifted to 357 nm in the presence of oxidising agent such as m-chloroperoxy benzoic acid (m-CPBA). With
gradual increase in the m-CPBA concentration, the absorption band at 470 nm decreases while the band at 357
nm increases. The same system shows gradual increase in the fluorescence signal at 463 nm in the presence of
m-CPBA. The fluorescence signal was unaffected in the presence of common anions and metal cations. The
mechanism for optical signalling was due to the conversion of weakly fluorescent TE to fluorescent esculetin
through desulfurization reaction. 13C-NMR shows strong evidence in support of the chemical conversion of
TE to esculetin. TE may find applications to probe the redox environment in various chemical and biochemical
processes.
Keywords. Thioesculetin; m-chloroperoxy benzoic acid; absorption; fluorescence; desulfurization.
cence resonance energy transfer. Apart from these pho-
tophysical processes, on application of mild chemical
stimulus, the probe molecule can be reversibly or irre-
versibly transformed to another chemical form. In such
cases the recognition is achieved by ‘on-off’/‘off-on’
fluorescence signalling or through ratiometric analysis,
where the probe molecule shows optical signalling in
distinct wavelengths before and after addition of chem-
ical stimulus.23 Coordination of coumarin derivatives
with metal ions or desulfurization under mild chemical
stimulus are the two processes where such type of recog-
nition is observed. It has been reported that the mild
chemical processes have advantages in terms of selec-
tivity and sensitivity. A large number of biochemical
processes occur continuously in the human body under
mild conditions and hence such probes find extensive
application in this regard.23,27
1. Introduction
Coumarins are a class of benzopyran compounds that
exhibit exciting photophysical properties.1–6 These pro-
perties are sensitive to the surrounding solvent medium.
The medium dependent photophysical properties of
coumarin are often exploited to probe different physic-
ochemical processes in condensed media.7–21 To name
a few, investigation of solvatochromic properties,7–9
determination of the polarities of micro environments,
10,11 investigation of photoinduced electron transfer pro-
cesses,12–16 estimations of the solvent relaxation times,
etc.8–17,17–21 Coumarin derivatives are also known to
be very good sensors for various metal ions like,
Ca(II), Mg(II), Al(III), Cr(III), Fe(III), Ni(II), Cu(II),
Zn(II), Pb(II), Hg(II), and Ag(I).22–26 In the case of
anions, like fluoride, phosphate, cyanide, acetate or
benzoate, coumarin derivatives have served as good
chemosensors.22–24 The recognition mechanisms of
these chemosensors mainly involve photoinduced elec-
tron transfer, intramolecular charge transfer or fluores-
The functional analogue of coumarin, thiocoumarin
is an interesting molecule which acts as redox indica-
tor in the presence of various oxidants. In the presence
of oxidant, thiocoumarin is readily transformed to
coumarin.28,29 There is a distinct difference in the photo-
physical properties of coumarin and thiocoumarin.30,31
*
For correspondence
Electronic supplementary material: The online version of this article (https://doi.org/10.1007/s12039-018-1440-5) contains
supplementary material, which is available to authorized users.

34 Page 2 of 7
J. Chem. Sci. (2018) 130:34
HO
HO
solutions for absorption and fluorescence studies were pre-
pared in 10 mM phosphate buffer (pH 7) containing 10%
acetonitrile. Acetonitrile was added in the phosphate buffer
solution to overcome the solubility problem due to m-CPBA.
Fluorescence quantum yields of TE and esculetin were deter-
mined by relative method using Coumarin-1 laser dye as a
standardwithaknownquantumyieldof 0.62inacetonitrile.33
Hydroxyl and superoxide radicals were generated by radia-
tion chemical methods as reported in the literature.34
O
S
TE
Scheme 1. Structure of thioesculetin (TE).
Coumarin and thiocoumarin have absorption in dif-
ferent wavelength regions. Coumarins are generally
fluorescent but thiocoumarins are very weak fluo-
rophores. Chang and his group, have studied conversion
of different thiocoumarins to coumarins in the pres-
ence of various oxidising agents like hypochlorous
acid (HOCl), m-chloroperoxy benzoic acid (m-CPBA),
or trichloroisocyanuric acid.28,29,32 They have demon-
strated that during the conversion of the thioketone
group to ketone group, the fluorescence signal was
increased substantially. Also, they have shown that flu-
2.2 Instrumentation
FTIR spectra of the solid samples were recorded in KBr pel-
lets on a Bruker-Tensor 37 spectrometer. HRMS spectra were
recorded on Impact II Ultra-High-Resolution Time-of-Flight
1
Mass Spectrometer from Bruker Daltonik GmbH. HNMR
and 13CNMR were recorded on Bruker Ascend 500 NMR
spectrometer. Melting point was determined manually from
Buchi M-560 melting point apparatus. Steady state absorp-
tion and fluorescence spectra were recorded on JASCO V-650
orescence signalling was less affected in the presence spectrophotometer and JASCO FP-8500 spectrofluorometer,
respectively. For steady state irradiation, cobalt-60 radiation
source was used and the radiation dose was estimated by using
standard Fricke dosimeter.34
of common interfering cations and anions. Apart from
being redox indicators, thiocoumarin derivatives were
also reported to show colorimetric and fluorescence sig-
nalling in the presence of trivalent gold ions.26 Excellent
selectivity for gold ions was achieved with the detec-
tion limit in the sub-micromolar level was reported.
Thioesculetin (TE) is a thiocoumarin derivative of 6,7-
dihydroxy coumarin commonly known as esculetin. The
chemical structure of TE is shown in Scheme 1. With
an aim to develop TE as a chemosensor in the presence
of the oxidant, we have reported the optical signalling
behaviour of TE in the presence of m-CPBA in this
manuscript. The probable mechanism of signalling has
been identified and the effect of interfering background
ions during flourescence signalling has been discussed.
Signalling behaviour has also been studied with other
oxidants like, hydroxyl radical, hydrogen peroxide and
superoxide radical.
2.3 Synthesis of thioesculetin (TE)
A mixture of the esculetin (1 equivalent) and Lawesson’s
reagent [2,4-bis(4-thoxyphenyl)-1,3,2,4-dithiadiphosphetane
-2,4-disulfide] (2 equivalents) in anhydrous toluene was
refluxed for about 30 h according to reported method.35 After
cooling, the solvent was evaporated under reduced pressure
and the residue was extracted with ethyl acetate and water.
The ethyl acetate extract was further dried over Na2SO4.
The sticky residue was then separated by column chromatog-
raphy with petroleum ether-acetone mixture (8:2). Yield:
65–70%; M.p. 231–234◦C, 1H NMR (500 MHz, DMSO-d6):
(C9H6O3S), 6.95(s, 1H), 7.04(s, 1H), 7.06(d, J = 3 Hz, 1H),
7.76(d, J = 9 Hz, 1H) ppm; 13C NMR(500 MHz, DMSO-d6):
(C9H6O3S), 196.59, 152.66, 152.26, 144.95, 137.41, 125.64,
113.73, 112.09, 102.78 ppm; HRMS calculated for C9H6O3S
(+H): m/z: 195.0117, found: 195.0113. FTIR (C9H6O3S):
3379, 2983, 2349, 1554, 1473, 1259, 1130, 1025, 937, 810,
638, 518, 432 cm−1. The spectra for 1H, 13C NMR, HRMS
and FTIR (Figures S1–S4) are provided in electronic support-
ing information.
2. Experimental
2.1 Chemicals and reagents
Esculetin and m-chloroperoxy benzoic acid (m-CPBA) were
purchased from Sigma Aldrich Chemicals. Lawesson’s
reagent was from Avra Synthesis Pvt. Ltd. India. All metal
salts, hydrogen peroxide and phosphate buffer were of ana-
lytical grade. Anhydrous toluene, ethyl acetate, methanol,
chloroform, petroleum ether, acetone were of synthetic grade.
Acetonitrile used was of HPLC grade. Water from Millipore
water purifier system was used for solution preparation and
3. Results and Discussion
3.1 Steady state absorption and fluorescence spectra
Esculetin and TE have distinctive absorption bands in
the UV–Visible region. Esculetin has absorption max-
freshly prepared solutions were used for experiments. The imum around 357 nm whereas for TE the maximum

J. Chem. Sci. (2018) 130:34
Page 3 of 7 34
3500
3000
2500
2000
1500
1000
500
0.4
0.3
0.2
0.1
0.0
357 nm
470 nm
3500
2800
2100
1400
700
b)
0.35
0.28
0.21
0.14
0.07
0.00
a)
0
1.5
3.0
4.5
1
2
3
4
5
[m-CPBA]/[TE]
[m-CPBA]/[TE]
a)
b)
0
450
500
550
600
650
700
400 Wavele5n6g0th 6(n40m) 720
320
480
800
Wavelength (nm)
Figure 2. Fluorescence titration of TE (20 μM) solution
with m-CPBA (10–110 μM) at pH 7.0 (10 mM phosphate
Figure 1. UV-Visible absorption spectra of TE (20 μM)
with m-CPBA (10–110 μM) at pH 7.0 (10 mM phosphate
buffer containing 10% acetonitrile). Inset (a) shows camer-
a-ready pictures of TE (A) and TE in presence of m-CPBA
(B). Inset (b) shows the change in absorbance at 470 and 357
nm for the same solution.
buffer containing 10% acetonitrile).
= 400 nm. Inset (a)
λ
ex
shows the change in fluorescence intensity at 463 nm for the
same solutions. Inset (b) shows camera-ready pictures of TE
(A) and TE in presence of m-CPBA (B) under 366 nm UV
lamp illumination.
absorption appears at 470 nm. On addition of the m- fluorescence spectra of m-CPBA (Figure S6 in SI). The
CPBA in the concentration range of 10 to 100 μM to a fluorescence spectrum of pure TE does not interfere in
solution of 20 μM TE, there was decrease in absorbance the fluorescence titration process, as TE emits at dif-
at 470 nm with concomitant increase at 357 nm through ferent wavelength (516 nm). The synthesized TE was
a crossover point at 400 nm (Figure 1). The color change free from any fluorogenic contamination as observed in
can be visualized by the naked eye, from yellow to col- the absorption, emission and excitation spectra of TE
orless as shown in Figure 1, inset (a).
under similar experimental condition (Figure S7 in SI).
Above 100 μM concentration of m-CPBA, the In the context of ratiometric analysis of absorbance at
absorbance increase was not regular, in fact it starts to 470 nm and 357 nm with m-CPBA concentration, there
decrease (Figure S5 in SI). Inset (b) of Figure 1 repre- was a decrease in the ratio, suggesting possible conver-
sents the absorbance change of TE at 470 nm and 357 sion of TE to another species (Figure S8 in SI). It is very
nm with respect to m-CPBA concentrations.
common that thioketones (C=S) are readily converted
Thiocoumarins are generally weakly fluorescent in to ketone (C=O) upon oxidation through desulfurization
solution. The quantum yield for fluorescence emission process.27,29,32 m-CPBA has the unique property of oxy-
of TE was 0.023 in the solvent system under investiga- gen atom donation during oxidation.36 The conversion
tion. The change in fluorescence spectra of TE solutions process for TE in the presence of m-CPBA was com-
in the presence of m-CPBA were recorded by exciting pleted within 20 min and the product was stable upto
at 400 nm (Figure 2). The fluorescence signal at 463 nm 2 h as revealed from the time dependent fluorescence
gradually increases with the increasing concentration of signal change (Figure S9 in SI). In order to establish the
m-CPBA up to 100 μM (Inset (a) of Figure 2). In this sit- chemical conversion, 13C NMR was recorded for pure
uation the florescence of the solution can be visualized TE and the reaction product of TE in the presence of m-
by the naked eye. The blue emission observed under UV CPBA. The reaction product of m-CPBA and TE was
lamp is shown in Figure 2 inset (b).
separated using a silica column for recording the NMR.
The reason for exciting at 400 nm was to minimise The 13C NMR signal of thioketone (C=S) group for TE
the contribution of fluorescence signal due to different was observed at 196.59 ppm. After addition of 5 equiv-
amount of light absorption by TE solution with addi- alent of m-CPBA the signal appeared at 161.25 ppm
tion of m-CPBA. From the absorption and fluorescence which was identical to ketone (C=O) group of esculetin
spectra it was obvious that there was a change in the (Figure 3).
chemical nature of TE in the presence of m-CPBA. In
the process of absorption and fluorescence changes, m-
CPBA itself does not contribute directly absorption and lent of m-CPBA to TE, the fluorescence quantum yield
fluorescence signal as shown in control absorption and ofTEsolutionwasfoundtobe0.15whichwasveryclose
As mentioned earlier, TE has very low quantum yield
ϕ
(
= 0.023). However, with the addition of 5 equiva-
f

34 Page 4 of 7
J. Chem. Sci. (2018) 130:34
Figure 3. 13C-NMR spectrum of TE, TE in presence of m-CPBA and esculetin. [TE]
= 200 μM, [m-CPBA] = 1 mM, [esculetin] = 200 μM in DMSO-d6.
ϕ
to esculetin ( = 0.14) under similar conditions. From intensity for TE solution in the presence of m-CPBA
f
the above experimental evidences, the proposed mech- only.
anism for the conversion of TE to esculetin is shown
The metal ions employed in the present system did not
in Scheme 2. Similar desulfurization mechanism was increase the florescence signal of TE solution. Inset of
reported for thioamide and thioketone derivatives with Figure 4A shows the representative fluorescence spectra
high selectivity and yield by Bahrami et al.37
ofpureTEsolutionandTEsolutioninpresenceofthem-
Chang et al., have performed signalling behaviour of CPBA or metal ions. In order to understand the selective
thiocoumarin derivative in the presence of m-CPBA.29 enhancement of fluorescence intensity of TE solution
Compared to thiocoumarin, TE had achieved highest in the presence of m-CPBA, the same metal ions were
signalling at lower concentrations of m-CPBA. Also, used under competitive conditions. As mentioned ear-
the increase in fluorescence signal is almost two times lier, except mercury, the enhancement of fluorescence
higher in the case of TE compared to thiocoumarin intensity was not affected much and within the experi-
derivative. At higher concentrations of m-CPBA (more mental error in the presence of other metal ions as shown
than 5 equivalents), conversion of TE to esculetin was in Figure 4B. The interference caused by mercury may
completed and further addition of m-CPBA probably led be due to the oxidation of phenolic OH group of TE as
to the reaction with the phenolic OH groups of esculetin. reported in the literature for other molecules having phe-
Phenolic compounds yield Prussian blue colour in the nolic OH group.39 Likewise, there was no interference
presence of potassium ferricyanide and ferric chloride, observed from anions in the above signalling process of
which have absorption around 700 nm.38 The addition m-CPBA. The anions used were halides, sulphate, car-
of more than 5 equivalents of m-CPBA to TE solution bonate, acetate, nitrate and phosphate. Figure 5A shows
was unable to develop any Prussian blue colour, which thattherewasselectiveincreaseinfluorescenceintensity
confirmed that indeed the phenolic groups of esculetin for TE solution in presence of the m-CPBA only and the
have undergone further reaction with m-CPBA (Figure anions were unable to influence the florescence signal
S10 in SI).
of TE solution. Inset of Figure 5A shows the represen-
tative fluorescence spectra of TE solution alone and TE
solution in the presence of m-CPBA or anions. Under
competitive conditions, of the anions the enhancement
of fluorescence intensity of TE solution in the presence
of m-CPBA was not affected much and the small varia-
tions were within the experimental error (Figure 5B).
3.2 Effect of interfering ions on fluorescence
signalling
The fluorescence signalling process for TE with m-
CPBA was monitored in the presence of common metal
ions and anions to see the possible interference effect.
The metal ions used are of alkali, alkaline earth, tran-
sition metals along with zinc, cadmium and mercury.
There was no interference in the above signalling pro-
cess of TE with m-CPBA, except mercury, which may
3.3 Comparison of signalling effect of TE in presence
of other oxidants
be due to special affinity towards sulfur atom. Figure 4A The signalling effect of TE was compared with other
shows that there was selective increase in fluorescence oxidants like, hydroxyl radical, superoxide radical and

J. Chem. Sci. (2018) 130:34
Page 5 of 7 34
Scheme 2. Conversion of thioesculetin (TE) to esculetin by m-CPBA.
25
20
15
10
5
16
14
12
10
8
3000
2000
1000
0
A
B
TE+mCPBA
TE / TE+metal ions
TE+Hg(II) ions
6
450
500
550
600
Wavelength (nm)
4
2
0
0
+ TE
+ TE+ m-CPBA
Figure 4. (A) Ratios of fluorescence intensity of TE solution in presence of m-CPBA or metal ions with
respect to TE solution only. Inset shows the representative fluorescence spectra of TE solution only and
TE solution in presence of m-CPBA or metal ions. (B) Ratios of fluorescence intensity of TE solution in
presence of m-CPBA and metal ions with respect to TE solution only. [TE] = 20 μM, [m-CPBA] = 100 μM
and [Mn+] = 100 μM at pH 7.0 (10 mM phosphate buffer containing 10% acetonitrile).
= 400 nm.
λ
ex
25
3000
A
B
18
16
14
12
10
8
TE+mCPBA
20
15
10
5
2000
1000
0
TE/TE+Common anions
450
500
550
600
6
4
Wavelength (nm)
2
0
0
+ TE
+ TE + m-CPBA
Figure 5. (A) Ratios of fluorescence intensity of TE solution in presence of m-CPBA or anions with respect
to TE solution only. Inset shows the representative fluorescence spectra of TE solution only and TE solution
in presence of m-CPBA or anions. (B) Ratios of fluorescence intensity of TE solution in presence of m-CPBA
and anions with respect to TE solution only. [TE] = 20 μM, [m-CPBA] = 100 μM and [An−] = 100 μM at
pH 7.0 (10 mM phosphate buffer containing 10% acetonitrile).
= 400 nm.
λ
ex

34 Page 6 of 7
J. Chem. Sci. (2018) 130:34
of a weak fluorescent molecule, TE, to strongly fluores-
cent molecule, esculetin, in the presence of m-CPBA.
13C NMR clearly supported that the transformation of
TE to esculetin was through desulfurization mechanism.
In fact, TE acts as an ‘off-on’ type fluorescence switch
under oxidizing condition. The signalling was selec-
tive in nature and negligibly affected in the presence
of various metal ions and anions as background. TE
may find applications as redox indicator in chemical and
biochemical environment, in particular for designing
suitable chemodosimetry for reactive oxygen species
and reactive nitrogen species.
100
90
80
70
60
50
40
30
20
10
357 nm
470 nm
0
Hydrogen
peroxide
m-CPBA
Hydroxyl
radical
Superoxide
radical
Supporting Information (SI)
Figures S1–S10 are available as Supplementary Infor-
mation at www.ias.ac.in/chemsci.
Figure 6. % change in absorbance of TE in presence of
m-CPBA, hydroxyl radical, superoxide radical and hydro-
gen peroxide at 470 and 357 nm. [TE] = 20 μM, [m-CPBA]
= [hydroxyl radical] = [superoxide radical] = [peroxide] =
100 μM at pH 7.0 (10 mM phosphate buffer).
Acknowledgements
RGS thanks Department of Atomic Energy, Government of
India for providing fellowship under BARC-SPPU collabo-
rative research programme. The authors are highly grateful
to Dr. K. I. Priyadarsini, BARC and Prof. A. S. Kumbhar,
SPPU for the keen interest in this research work. The authors
are also thankful to Head, RPCD, BARC and Head, Chem-
hydrogenperoxidealongwithm-CPBA. Thepercentage
change in absorbance for TE at 470 nm and 357 nm in
the presence of different oxidants is shown in Figure 6.
From Figure 6, it is clear that m-CPBA shows better
signalling efficiency in comparison to other oxidants.
Apart from hydroxyl radical, the O-O bond in m-CPBA istry Department, SPPU for their constant encouragement and
support.
is the weakest, followed by hydrogen peroxide and
superoxide. The bond dissociation energy of peracetic
acid is 29.5 kcal/mol and the same for hydrogen per-
oxide is 48 kcal/mol in the gas phase.40,41 In many
reactions, m-CPBA is more selective than hydrogen
peroxide and other peracids.36 The O-O bond disso-
ciation energy in superoxide radical is expected to be
higher than in hydrogen peroxide according to molecu-
lar orbital theory and also superoxide radical is a poor
oxidant. On the contrary, though hydroxyl radical is a
strong oxidant, the conversion of TE to esculetin was
close to 50% compared to m-CPBA. The reaction of
hydroxyl radical possibly proceeds through production
of dimeric product of TE through S-S bond formation,
which further hydrolysed to yield TE and esculetin. A
similar type of reaction mechanism has been reported in
the literature for hydroxyl radical reaction with ethylene
trithiocarbonate.42
References
1. Atkins R L and Bliss D E 1978 Substituted coumarins
and azacoumarins. Synthesis and fluorescent properties
J. Org. Chem. 43 1975
2. Halstead J A and Reeves R R 1978 Mixed solvent sys-
tems for optimizing output from a pulsed dye laser Opt.
Commun. 27 273
3. Fletcher A N 1977 Laser Dye Stability. Part 3. Bicyclic
Dyes in Ethanol Appl. Phys. 14 295
4. Schimitschek E J, Trias J A, Hammond P R, Henry R
A and Atkins R L 1976 New laser dyes with blue-green
emission Opt. Commun. 16 313
5. Reynolds G A and Drexhage K H 1975 New coumarin
dyes with rigidized structure for flashlamp-pumped dye
lasers Opt. Commun. 13 222
6. Rechthaler K and Köhler G 1994 Excited state properties
and deactivation pathways of 7-aminocoumarins Chem.
Phys. 189 99
7. Li J, Zhang C, Yang S, Yang W and Yang G 2014 A
coumarin-based fluorescent probe for selective and sen-
sitive detection of thiophenols and its application Anal.
Chem. 86 3037
8. Jones II G, Jackson W R, Konaktanaporn S and Halpern
A M 1980 Solvent effects on photophysical parameters
for coumarin laser dyes Opt. Commun. 33 315
9. Jones II G, Jackson W R and Halpern A M 1980 Medium
effects on fluorescence quantum yields and lifetimes for
coumarin laser dyes Chem. Phys. Lett. 72 391
4. Conclusions
Thioesculetin (TE) was tested for colorimetric and flu-
orescence signalling in the presence of m-CPBA. The
signalling process was due to desulfurization reaction of
TE. Colorimetric signalling in the presence of m-CPBA
clearly indicated that there was transformation of TE
which was evident from the change in absorption spec-
tra. Fluorescence signalling confirms the transformation

J. Chem. Sci. (2018) 130:34
Page 7 of 7 34
10. Sarkar N, Dutta A, Das S and Bhattacharyya K 1996 26. Park J E, Choi M G and Chang S 2012 Colorimetric
Solvation dynamics of coumarin 480 in micelles J. Phys.
Chem. 100 15483
and fluorescent signalling of Au3+ by desulfurization of
thiocoumarin Inorg. Chem. 51 2880
11. Sarkar N, Das K, Dutta A, Das S and Bhattacharyya K 27. Xu C, Li H and Yin B 2015 A colorimetric and ratio-
1996 Solvation Dynamics of Coumarin 480 in Reverse
Micelles. Slow Relaxation of Water Molecules J. Phys.
Chem. 100 10523
metric fluorescent probe for selective detection and
cellular imaging of glutathione Biosens. Bioelectron. 72
275
12. Nad S and Pal H 2002 Photoinduced electron trans- 28. Moon J O, Lee W D, Choi M G, Ahn S and Chang S 2012
fer from aliphatic amine to coumarin dyes J. Chem.
Phys. 116 1658
Dual signalling of hypochlorous acid by desulfurization
of thiocoumarin Tetrahedron Lett. 53 6594
13. Castner E W, Kennedy D Jr and Cave R J 2000 Solvent 29. Cha S, Hwang J, Choi M G and Chang S 2010 Dual
as electron donor: Donor/Acceptor electronic coupling
is a dynamical variable J. Phys. Chem. A 104 2869
signallingofm-chloroperbenzoicacidbydesulfurization
of thiocoumarin Tetrahedron Lett. 51 6663
14. Pal H, Shirota H, Tominaga K and Yoshihara K 30. Bhattacharyya K, Das P K, Ramamurthy V and Rao V
1999 Ultrafast intermolecular electron transfer from
orthomethoxyaniline to excited coumarin dyes J. Chem.
Phys. 110 11454
P 1986 Triplet-state photophysics and transient photo-
chemistry of cyclic enethiones: A laser flash photolysis
study J. Chem. Soc. Faraday Trans. 2 82 135
15. ShirotaH, PalH, TominagaKandYoshiharaK1998Sub- 31. Burdzinski G, Ziolek M, Karolczak J and Maciejewski
stituent effect and deuterium isotope effect of ultrafast
intermolecular electron transfer: Coumarin in electron-
donating solvent J. Phys. Chem. A 102 3089
A 2004 S2 and S1 states deactivation of thiocoumarin in
n-hexane and acetonitrile studied by femtosecond fluo-
rescence upconversion and transient absorption spectro-
scopies J. Phys. Chem. A 108 11160
16. Nagasawa Y, Yartsev A P, Tominaga K, Johnson A E
and Yoshihara K 1993 Substituent effects on intermolec- 32. Lee S K, Choi M G and Chang S K 2014 Signalling of
ular electron transfer: coumarins in electron-donating
solvents J. Am. Chem. Soc. 115 7922
17. Nandi N, Bhattacharyya K and Bagchi B 2000 Dielectric
chloramine: a fluorescent probe for trichloroisocyanuric
acid based on deoximation of a coumarin oxime Tetra-
hedron Lett. 55 7047
relaxation and solvation dynamics of water in complex 33. Barik A, Nath S and Pal H 2003 Effect of solvent polarity
chemical and biological systems Chem. Rev. 100 2013
18. Levinger N E 2000 Ultrafast dynamics in reverse
on the photophysical properties of coumarin-1 dye J.
Chem. Phys. 119 10202
micelles, microemulsions, and vesicles Curr. Opin. Col- 34. Singh B G, Thomas E, Kumakura F, Dedachi K, Iwaoka
loid Interface Sci. 5 118
19. Gardecki J A and Maroncelli M 1999 Comparison of the
single-wavelength and spectral-reconstruction methods
M and Priyadarsini K I 2010 One-electron redox pro-
cesses in a cyclic selenide and a selenoxide: A pulse
radiolysis study J. Phys. Chem. A 114 8271
for determining the solvation-response function J. Phys. 35. Ninomiya M, Aoki T, Adfa M, Yoshimura T and
Chem. A 103 1187
20. Horng M L, Gardecki J A, Papazyan A and Maroncelli
M 1995 Subpicosecond measurements of polar solvation
Koketsu M 2014 Comparison of antitermite properties
of 2-thioxocoumarins against Coptotermes formosanus
Shiraki Holzforschung 68 361
dynamics: Coumarin 153 revisited J. Phys. Chem. 99 36. Hussain H, Al-Harrasi A, Green I R, Ahmed I, Abbas
17311
G and Rehman N U 2014 meta-Chloroperbenzoic acid
(mCPBA): a versatile reagent in organic synthesis RSC
Adv. 4 12882
21. Reynolds L, Gardecki J A, Frankland S J V, Horng M L
and Maroncelli M 1996 Dipole solvation in nondipolar
solvents: Experimental studies of reorganization ener- 37. Bahrami K, Khodaei M M, Shakibaian V, Khaledian D
gies and solvation dynamics J. Phys. Chem. 100 10337
22. Li H, Cai L and Chen Z 2012 Coumarin-Derived
Fluorescent Chemosensors In Advances in Chemical
and Yousefi B H 2012 TiCl4-promoted desulfurization of
thiocarbonyls and oxidation of sulfides in the presence
of H2O2 J. Sul. Chem. 33 155
Sensors Wen Wang (Ed.) Available at http://www. 38. Budini R, Tonelli D and Girotti S 1980 Analysis of total
intechopen.com/books/advances-in-chemical-sensors/
coumarin-derived-fluorescent-chemosensors. Accessed
on 12 May 2016
phenols using the Prussian Blue method J. Agric. Food
Chem. 28 1236
39. McKillop A and Young D W 1977 Oxidation of phenols
and hydroquinones by mercury(II) trifluoroacetate and
mercury(II) oxide Synth. Commun. 7 467
23. Du J, Hu M, Fan J and Peng X 2012 Fluorescent chemod-
osimeters using “mild” chemical events for the detection
of small anions and cations in biological and environ- 40. Evans F W and Sehon A H 1963 The thermal decom-
mental media Chem. Soc. Rev. 41 4511
24. Kaur K, Saini R, Kumar A, Luxami V, Kaur N, Singh
position of peracetic acid in aromatic solvents Can. J.
Chem. 41 1826
P and Kumar S 2012 Chemodosimeters: An approach 41. Bach R D, Ayala P Y and Schlegel H B 1996 A reassess-
for detection and estimation of biologically and medi-
cally relevant metal ions, anions and thiols Coord. Chem.
Rev. 256 1992
ment of the bond dissociation energies of peroxides. An
ab Initio study J. Am. Chem. Soc. 118 12758
42. Ramnani S P, Dhanya S and Bhattacharyya P K 1990
Pulse radiolytic studies on the oxidation of 1, 3 dithiolane
2-thione (ETTC) by OH radicals in aqueous media Int.
J. Radiat. Appl. Instrum. Part C 36 409
25. Choi M G, Kim Y H, Namgoong J E and Chang S 2009
Hg2+-selective chromogenic and fluorogenic chemod-
osimeter based on thiocoumarins Chem. Commun. 3560