A coumarin based fluorescent chemodosimeter for phosgene gas detection instantaneously in solution and the gas phase

Article abstract of DOI:10.1039/d0nj00645a

A coumarin based compound, 7-(diethylamino)-2-oxo-2H-chromene-3-carbaldehyde oxime (DCCO), has been developed as a visual fluorescent chemodosimeter for selective detection of highly toxic phosgene gas. DCCO exhibits absorption bands at 330 nm and 425 nm. In the presence of phosgene, the absorbance at 330 nm increases and the peak at 425 nm is shifted to 420 nm with decreasing absorbance accompanying a color change from yellow to colorless. The fluorescence intensity of the probe at 483 nm is enhanced in the presence of phosgene (λ_ex = 425 nm) but nerve agents and other acid chlorides including trisphosgene could not induce any significant enhancement of the fluorescence. DCCO on interaction with phosgene is converted to the corresponding nitrile derivative, 7-(diethylamino)-2-oxo-2H-chromene-3-carbonitrile (DCC). The quantum yield has been increased 13 fold on conversion from DCCO to DCC. The fluorescence enhancement has been explained by the ICT mechanism, which has been supported by theoretical calculations. It exhibits a rapid response for naked eye detection of phosgene. DCCO has been used for the detection of phosgene in solution and the gas phase.

Full text of DOI:10.1039/d0nj00645a

View Article Online
View Journal
NJC
New Journal of Chemistry
Accepted Manuscript
A journal for new directions in chemistry
This article can be cited before page numbers have been issued, to do this please use: S. Paul, P. Ghosh
and P. Roy, New J. Chem., 2020, DOI: 10.1039/D0NJ00645A.
Volume 42
Number
March 2018
Pages 3963-4776
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
6
21
NJC
New Journal of Chemistry
rsc.li/njc
A journal for new directions in chemistry
Accepted Manuscripts are published online shortly after acceptance,
before technical editing, formatting and proof reading. Using this free
service, authors can make their results available to the community, in
citable form, before we publish the edited article. We will replace this
Accepted Manuscript with the edited and formatted Advance Article as
soon as it is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes to the
text and/or graphics, which may alter content. The journal’s standard
Terms & Conditions and the Ethical guidelines still apply. In no event
shall the Royal Society of Chemistry be held responsible for any errors
or omissions in this Accepted Manuscript or any consequences arising
from the use of any information it contains.
ISSN 1144-2546
PAPER
Chechia Hu, Tzu-Jen Lin et al.
Yellowish and blue luminescent graphene oxide quantum dots
prepared via a microwave-assisted hydrothermal route using
H2O2 and KMnO4 as oxidizing agents
rsc.li/njc

Page 1 of 8
Pl eNa es we dJ oo u nr no at l ao df jCu hs et mm i as tr rgy ins
1
2
3
4
5
6
7
View Article Online
DOI: 10.1039/D0NJ00645A
ARTICLE
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
A coumarin based fluorescent chemodosimeter for phosgene gas
detection instantaneously in solution and gas phase
Received 00th January 20xx,
Accepted 00th January 20xx
a
b
,a
Sima Paul, Pritam Ghosh and Partha Roy*
DOI: 10.1039/x0xx00000x
A coumarin based compound, 7-(diethylamino)-2-oxo-2H-chromene-3-carbaldehyde oxime (DCCO), has been developed as
a visual fluorescent chemodosimeter for selective detection of highly toxic phosgene gas. DCCO exhibits absorption bands
at 330 nm and 425 nm. In the presence of phosgene, the absorbance at 330 nm increases and the peak at 425 nm is
shifted to 420 nm with decreasing absorbance accompanying a color change from yellow to colorless. Fluorescence
intensity of the probe at 483 nm enhances in the presence of phosgene (λex = 425 nm) but nerve agents and other acid
chlorides including trisphosgene could not induce any significant enhancement of the fluorescence. DCCO on interaction
with phosgene is converted to the corresponding nitrile derivative, 7-(diethylamino)-2-oxo-2H-chromene-3-carbonitrile
(DCC). Quantum yield has been increased by 13 fold on conversion from DCCO to DCC. Fluorescence enhancement has
been explained by ICT mechanism which has been supported by theoretical calculations. It exhibits rapid response for
naked eye detection of phosgene. DCCO has been used for the detection of phosgene in solution and gas phase.
human safety and environment because of its possible use in
terrorist activity and accidental exposure from industries.
Thus, there is demand for the development of effective
Introduction
Development of chemosensors for small neutral molecules
becomes important as the compounds have potential to be
used in the terrorist activities. Nerve agents such as sarin,
soman, cyclosarin, tabun, etc. along with phosgene are known
chemosensor for detection of this poisonous gas.
Presence of phosgene has been indicated by some
conventional methods such as chromatographic techniques
7
8
1
coupled with mass spectrometry, electrical methods,
as chemical warfare agents (CWAs). These agents have
9
10
colorimetric procedures, and fluorogenic methods. Among
all mentioned techniques, the fluorescence method is
considered to be the best because of its operational simplicity,
high selectivity, good sensitivity, rapidity, low cost, non-
destructive methodology and direct visual perception. In
addition to these, other techniques suffer several limitations
e.g. on-site detection, portability issue, time consuming or
complex analysis, etc.
intended uses as chemical weapons. Generally, nerve agents
covalently bind with acetylcholinesterase to inhibit activity of
the neurotransmitter acetylcholine, causing severe effects on
2
humans and animals. On the other hand, phosgene (COCl ) is
2
a colorless toxic gas due to the presence of its highly active
acyl chloride group. It had been used in a chemical weapon in
World War I. It is responsible for 80% deaths caused by the
3
use of chemical weapons. Exposure of phosgene can damage
the respiratory track and lungs of humans, including
Phosgene undergoes very fast acylation reactions with
various nucleophilic moieties such as amino, hydroxyl and
4
noncardiogenic pulmonary edema and even lead to death. It
11
sulfhydryl groups. There are various types of probe for
has been reported that lungs injury takes place severely within
min under exposure 20 ppm phosgene and 90 ppm exposure
becomes fatal. It is extensively used as an intermediate in the
production of several important substances such as
insecticides, plastics, pharmaceuticals, pesticides, etc. Use of
nerve agents has been forbidden whereas phosgene is readily
phosgene where phosgene undergoes acylation reaction with
2
12
13
14
5
amine-containing coumarin,
naphthalimide,
BODIPY,
15
16
17
rhodamine, pyronin, or benzothiadiazole. Most of the
above mentioned probes are developed on photoinduced
electron transfer (PET) or intramolecular charge transfer
16
16,17
6
(ICT)
mechanism. Besides these, there are few
accessible. Thereby, phosgene has become a serious threat to
chemodosimeters reported based on fluorescence resonance
energy transfer (FRET) via phosgene-induced covalent cross-
10a
10e,10h,13c
linking the ring opening of rhodamine derivatives,
a.
Department of Chemistry, Jadavpur University, Kolkata 700 032, India Email:
partha.roy@jadavpuruniversity.in or proy@chemistry.jdvu.ac.in (P.R.)
Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Technion
18
the cyclization of a flexible chromophore precursor,
aggregation induced emission (AIE)
intramolecular proton transfer (ESIPT). But most of the
b.
19
and excited-state
City, Haifa 3200008, Israel
20
†
Footnotes relating to the title and/or authors should appear here.
Electronic Supplementary Information (ESI) available: [details of any sensors show poor selectivity. Some of these sensors have
21
supplementary information available should be included here]. See
been impeded by formaldehyde and nitric oxide. Few
DOI: 10.1039/x0xx00000x
Please do not adjust margins

Pl eNa es we dJ oo u nr no at l ao df jCu hs et mm i as tr rgy ins
Page 2 of 8
ARTICLE
Journal Name
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
phosgene sensors could not discriminate between triphosgene DCCO and its phosgene interacted product was prepared from
and phosgene because of amine catalyzed decomposition of the reported crystal structure. def2-SVP was considered for
triphosgene to phosgene. So, it is important to design probes every atoms at the level of B3-LYP using COSMO for
that can easily discriminate between phosgene and acetonitrile.
triphosgene. Now-a-days, with increasing demand of phosgene Here, the quantum yield φ was measured by using the
as important chemical in organic synthesis and in terrorist following equation
attack, it is necessary to design and develop a very rapid,
highly selective probe for the detection of phosgene.
View Article Online
DOI: 10.1039/D0NJ00645A
2
5
2
2
2
6
2
2
φ = φ ( F / F )( A / A )(n / n )
x s x s s x x s
where, X and S indicate the unknown and standard solution
respectively, φ = quantum yield, F = area under the emission
curve, A = absorbance at the excitation wave length, n = index
of refraction of the solvent. Here φ measurements were
performed using anthracene in ethanol as standard (φ =
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
2
7
0
.27).
Synthesis of Probe:
Synthesis of 7-diethylamino coumarin (2):
3
0.0 mL of ethanol was added to
a
mixture of 4-
diethylaminosalicylaldehyde (1.93 g, 10 mmol), diethylmalonate
(3.2 g, 20 mmol), piperidine (1.0 mL). It was refluxed for 6 h. The
mixture was cooled to room temperature. Solvent was evaporated
under reduced pressure. Glacial acetic acid (20.0 mL) and
concentrated HCl (20.0 mL) were added to the reaction mixture for
hydrolyze and the mixture was stirred for 6 h. The solution was
cooled to room temperature and poured onto 100 mL of ice water.
NaOH solution (40%) was added dropwise to adjust pH (to approx.
Scheme 1 Synthesis of the chemodosimeter (DCCO) for phosgene
In this context, we report here the synthesis,
characterization and phosgene sensing properties of a
coumarin based compound, 7-(diethylamino)-2-oxo-2H-
chromene-3-carbaldehyde oxime (DCCO) (Scheme 1). In this
work we have chosen coumarin as fluorophore unit because
the coumarin derivatives were widely used in the preparation
of medicine, perfumes, biology and fluorescent dye. Carbon 6.57 ( q, 1H, 6.3 Hz), 6.50 (d, 1H, 2.4 Hz), 6.04 (d, 1H, 9.3 Hz), 3.42
atom of phosgene is highly electron deficient as two chlorine (q, 4H, 7.2 Hz), 1.26 (m, 6H).
atoms are attached with it and this leads to easy nucleophilic
substitution at carbon center. DCCO has oxygen atom (at
oxime unit) which undergoes reaction with COCl . Some
theoretical calculations have been carried out to support
formation of DCCO and its product with phosgene.
5
) and a pale yellow precipitate was formed immediately. After
stirring for 30 min, the mixture was filtered, washed with water,
dried, and recrystallized from toluene to afford 7-
1
diethylaminocoumarin (1.65 g, 8.0 mmol) in 76% yield. H NMR
(
CDCl , 300 MHz) δ (ppm): 7.54 (d, 1H, 9.3 Hz), 7.27 (t, 2H, 5.4 Hz),
3
2
3
Synthesis of 7-diethylamino coumarin-3-aldehyde (3):
2
2
.0 mL of dry DMF was added drop by drop to POCl at 0 ºC under
3
N atmosphere and stirred for 1 h to obtain a red solution. This
2
solution was combined with 7-diethylaminocoumarin (1.52 g, 7.0
mmol, dissolved in 10 mL DMF). The mixture was then stirred at 60
°C for overnight and then poured into 100 mL of ice water. NaOH
solution (20%) was added until precipitation occurred. Then the
precipitate was filtered, washed with water, dried and recrystallized
in absolute ethanol to get 7-diethylaminocoumarin-3-aldehyde
1.23 g, 5.0 mmol) in 71% yield. H NMR (CDCl , 300 MHz) δ (ppm):
0.14 (1H, S), 8.27 (1H, S), 7.42 (1H, d, 9 Hz), 6.65 (1H, q, 6.6 Hz),
.50 (1H, d, 2.4 Hz), 3.49 (4H, q, 7.2 Hz), 1.28 (6H, q, 7.2 Hz).
Experimental
General Methods
All Solvents and Chemicals used in this work were purchased
from commercial sources and were used without further
purification. H NMR and C NMR spectra were recorded by
1
(
1
6
3
1
13
using Brucker 300 MHz instruments. CDCl was used as solvent
3
Synthesis of 7-(diethylamino)-2-oxo-2H-chromene-3-carbaldehyde
oxime (DCCO):
for NMR spectra. UV-vis titration experiments were done by
using Perkin Elmer Lambda 750 spectrophotometer.
Fluorescence experiments were performed on Perkin Elmer LS
Compound 3 (0.5 g, 2.03 mmol) was dissolved in dry ethanol (15
mL). Triethylamine (0.36 mL, 2.8 mmol) and hydroxylamine
hydrochloride (0.12 g, 1.72 mmol) were added to it. The resulting
reaction mixture was heated to reflux for overnight and a yellow
precipitate was formed. The precipitate was washed properly with
water. The crude product was recrystallized in CHCl –CH OH (1: 1)
5
5 with a fluorescence cell of 10 mm path. Silica gel (100−200
mesh) was used to perform Column chromatography.
Fluorescence lifetime experiment was performed by using
TCSPC (Time-correlated single photon counting) set-up. All the
measurement experiments were carried out under ambient
conditions.
DFT-D3 calculation was performed using Turbomole
software package (V. 7.3), OS: MACOS. The structure of the 7.5 Hz); C NMR (CDCl , 75 MHz): 160.63, 155.58, 151.02, 150.66,
3
3
1
to yield a yellow solid; yield: 73% (0.19 g). H NMR (CDCl , 300 MHz)
3
δ (ppm): 10.69 (1H, s), 9.07 (1H, s), 8.17 (1H, s), 8.04 (1H, s), 7.42
1H, d, 1.2 Hz), 7.28 (1H, d, 8.7 Hz), 3.41 (4H, q, 6.9 Hz), 1.21 (6H, q,
(
24
13
3
2
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 3 of 8
Pl eNa es we dJ oo u nr no at l ao df jCu hs et mm i as tr rgy ins
Journal Name
ARTICLE
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
1
37.94, 130.17, 129.29, 109.67, 108.91, 107.96, 44.40, 11.98; HRMS indicates formation of new product (Fig. 1, inset). ThVieewraArttiicolme Oentlriniec
+
(
ESI TOF): (m/z, %): 261.1300 [(DCCO + H ), 100 %].
value (A425/A330) changes from 0.36 to 22.65D(O6I3: 1f0o.1ld03e9n/Dha0nNcJe0m06e4n5tA)
in the presence of 1 equivalent phosgene (Fig. S1).
Synthesis of 7-(diethylamino)-2-oxo-2H-chromene-3-carbonitrile
(DCC):
DCCO (0.050 g, 0.19 mmol) was dissolved in dry acetonitrile (4.0
mL). Triethylamine (0.1 mL, 0.7 mmol) and triphosgene (0.070 g,
0
.23 mmol) was added to it. The reaction mixture was allowed to
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
stir at room temperature for 5 min. The solvent was evaporated to
dryness and the residue was purified by silica-gel column
chromatography and reddish yellow product was obtained. H NMR
1
(
CDCl , 300 MHz) δ (ppm): 7.98 (1H, s), 6.62 (2H, d, 9 Hz), 6.48 (1H,
3
13
s), 3.43 (4H, t, 5.4 Hz), 1.23 (6H, d, 8.1 Hz); C NMR (CDCl , 75
MHz): 160.00, 155.56, 150.09, 128.94, 127.97, 127.19, 124.28,
3
1
2
07.46, 96.02, 95.89, 43.90, 11.43 ; HRMS (ESI TOF): (m/z, %):
43.1126 [(DCC + H )].
+
General method of UV-vis and fluorescence titrations by UV-vis
and fluorescence:
-
Stock solution of chemodosimeter (DCCO) was prepared (c = 2 × 10
5
-1
ML ) in acetonitrile: water (1:1, v/v). The solution of the guest ions
-4
-1
and amine containing compounds were prepared (2 × 10 ML ) in
acetonitrile: water (1:1, v/v) immediately before performing the
experiment. The solution of probe and other analytes were
prepared in doubly distilled deionized water by using appropriate
dilution technique. Absorption and fluorescence spectra were
recorded by transferring appropriate amount of stock solution to
deionized water. After well mixing, the solutions were allowed to
stand at room temperature for 1 min. Then, absorption and
fluorescence spectra were recorded.
Fig. 1 Absorption titration spectra of DCCO (10 μM) in acetonitrile :
water (1:1) with triethylamine (100 μM) immediately after the
addition of different amounts of triphosgene (0−50 μM) at 25 °C
and the visual color change of DCCO with addition of 1 eqv. of
phosgene under UV light (inset).
The response of the probe towards various competing acid
chlorides has been studied in acetonitrile in the presence of
triethylamine by recording absorption spectra of DCCO with
different acid chlorides. A plot of (A425/A330) in the presence of
Detection of phosgene using TLC plate sticks:
phosgene,
diethyl
cyanophosphate
(DCNP),
diethyl
TLC plate sticks were prepared by immersing TLC plates into the
solution of DCCO (2 × 10 M) in CH CN and exposing it to air to
evaporate the solvent. The detection of phosgene was carried out
by inserting the TLC plate to the solution of phosgene (1 mM) and
evaporating solvent to dryness.
chlorophosphate (DCP), trifluoroacetic acid (TFA), HCl, p-
toluenesulfonyl chloride (p-TsCl), thionyl chloride (SOCl2),
phosphorus oxychloride (POCl ), oxalyl chloride (COCl) , acetyl
-
4
3
3
2
chloride (CH COCl) is shown in Fig. S2. As shown in the figure, it is
3
clear that the probe displays a high selectivity towards phosgene
among all other acid chlorides. Thus, the probe exhibits high
selectivity towards phosgene.
Results and discussion
Absorption spectral studies
Fluorescence studies
Phosgene is a volatile and highly toxic compound, while its Fluorescence spectra of DCCO (10 μM) have been obtained in
precursor triphosgene is a nonvolatile, easily controllable and less acetonitrile containing triethylamine (100 μM) immediately after
toxic solid material. In the presence of triethylamine, triphosgene is the addition of different amounts of triphosgene (0−50 μM) at 25 °C
2
8
converted into phosgene. So, we have used triphosgene in the (λ : 425 nm) (Fig. 2). From the figure it is evident that the probe
ex
presence of triethylamine instead of phosgene. We have first shows low intensity fluorescence peak at 488 nm in absence of
investigated the absorption spectra of the probe (DCCO) in phosgene with quantum yield (ɸ) of 0.004. Upon gradual addition
acetonitrile containing triethylamine (100 μM) immediately after of phosgene to the probe, the intensity at 483 nm gradually
the addition of different amounts of triphosgene (0−50 μM). increases. From this spectral behavior, it is clear that chemosensing
Initially, DCCO shows two major absorption bands at 330 nm and reaction between the probe and phosgene is very effective. The
4
25 nm. But when we have gradually added triphosgene to the fluorescence intensity gradually increases with the increase in the
probe solution the absorbance at 330 nm increases and the peak at concentration of phosgene. Quantum yield has been increased to
25 nm has slightly shifted to 420 nm with gradually decreasing 0.52. Thus, a 13 fold increment of fluorescence quantum yield has
absorbance. A clear isosbestic point has been noticed at 358 nm been observed in this case. A change in color of probe has been
Fig. 1). Thus, a blue shift phenomenon has been observed in this occurred from blue to green in the presence of COCl (Fig. 2, inset).
4
(
2
case due to the formation of CN group in the product (DCC). These
spectral changes are in accordance with the naked eye observation.
The yellow color solution of DCCO becomes colorless as soon as
triphosgene and triethylamine are added to the solution which
Sensitivity of the probe has been determined following 3σ
method. The determination of detection limit has been carried
out based on the formula K × Sb1/S, where Sb1 is the standard
29
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Pl eNa es we dJ oo u nr no at l ao df jCu hs et mm i as tr rgy ins
Page 4 of 8
ARTICLE
Journal Name
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
deviation of blank measurements and S is the slope of the and nitric oxide as some previously reported chemosensors for
calibration curve (See Supplementary Information). A plot of the phosgene experienced interference fromDtOheI:s1e0.1s0p3e9c/iDes0N(FJ0ig0.6S465)A.
fluorescence intensity of DCCO vs. concentration of triphosgene in We can see that formaldehyde and nitric oxide do not have any
the presence of triethylamine ranging from 0 to 2.0 µM shows significant effect on fluorescence intensity of DCCO.
View Article Online
2
1
2
linear fit (R = 0.997) (Fig. S3). From this linear fit data we have
Excited state behaviors of DCCO and DCC are examined by
calculated the detection limit of the probe for phosgene to be 0.12
nano-second time resolved fluorescence technique (Fig. S7). The
µM.
fluorescence decay curves of the compounds are obtained by using
the mono exponential functions. Life times (τ) of DCCO and DOCC
are found to be 0.667 ns and 3.22 ns, respectively. Using the
= kr + knr and kr = Φf /τ (Supplementary
Information) we have calculated the radiative rate constant (kr)
and total non radiative rate constant (k ) (Table S1). It has been
observed that radiative rate constant increases by 27 times
whereas non-radiative rate constant value decreases by 10 fold on
the conversion of DCCO to DCC. This event leads to the significant
enhancement of fluorescence.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
−
1
equations
τ
30
nr
Fig. 2 Fluorescence spectra of DCCO (10 μM) in MeCN containing
triethylamine (100 μM) after the addition of different amounts of
triphosgene (0−50 μM) at 25 °C; (λ : 425 nm). Inset: fluorescence
color change of DCCO in the presence of phosgene.
ex
The time dependent of fluorescence intensity of DCCO has been
measured in the presence of phosgene (Fig. S4A). From the spectra
it is evident that the fluorescence intensity of tested solution
increases rapidly and reaches the saturated level within 1 min, with
a pseudo first order rate constant of 16 × 10
result strongly supports high reactivity of the probe towards
phosgene. Moreover, the probe and probe-phosgene product (DCC)
in acetonitrile show very good photostability under irradiation at a
wavelength 485 nm for 1 h (Fig. S4B).
-2 -1
s (Fig. S5). This
Selectivity and specificity test is a very important parameter for
a smart probe for the detection of an analyte. Next, we have
studied selectivity of DCCO towards phosgene. The probe has been
treated with various competing acid chloride such as phosgene,
diethyl cyanophosphate (DCNP), diethyl chlorophosphate (DCP),
trifluoroacetic acid (TFA), HCl, p-toluenesulfonyl chloride (p-TsCl),
thionyl chloride (SOCl ), phosphorus oxychloride (POCl ), oxalyl
2
3
chloride (COCl) , acetyl chloride (CH COCl) and fluorescence
2
3
intensity has been measured (Fig. 3). From the figure, it is clear that
only phosgene shows remarkable fluorescence enhancement. From
Fig. 3A it is evident that only triphosgene cannot induce any
increment in fluorescence intensity of the probe while from Figure Fig. 3 (A) Fluorescence increment of DCCO in the presence of (1)
B it can be observed that fluorescence intensity of DCCO and phosgene (triphosgene/triethylamine), (2) DCNP (3) DCP (4)
phosgene does not change in the presence of triphosgene. It triphosgene (5) TFA (6) p-TsCl (7) SOCl (8) POCl (9) (COCl) and (10)
indicates clearly that DCCO is a highly selective chemodosimeter for CH COCl. (b) Fluorescence intensity of DCCO (2.0 × 10 M) toward
phosgene and triphosgene cannot interfere the detection phosgene (1.0 equiv) containing 10 equiv of (1) DCNP (2) DCP (3)
procedure of phosgene. These results are in accordance with that triphosgene (4) TFA (5) p-TsCl (6) SOCl (7) POCl (8) (COCl) and (9)
COCl. Here, R is DCCO and P denotes phosgene.
3
2
3
2
−
5
3
2
3
2
obtained in absorption spectral studies. It is important to CH
investigate the sensing ability of the probe towards formaldehyde
3
4
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 5 of 8
Pl eNa es we dJ oo u nr no at l ao df jCu hs et mm i as tr rgy ins
1
2
3
4
5
6
7
View Article Online
DOI: 10.1039/D0NJ00645A
ARTICLE
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Scheme 2. Fluorescence enhancement on conversion of DCCO to DCC.
Sensing mechanism:
could have been corresponding nitrile compound and we get the
result as expected. Very rare examples are known for phosgene
sensors where end product is not formed because of cyclisation.
Our present study is one of the chemosensors for phosgene in this
category.
Strong fluorescence has been observed when DCCO reacts with
phosgene to yield DCC (Scheme 2). We propose that the sensing of
phosgene of DCCO starts with nucleophilic substitution by oxime
‒
hydroxyl group with the removal of Cl from phosgene and
formation of oxime-N-O-oxychloride intermediate (Scheme 2). Final
product has been obtained after the elimination of C (=O)(Cl)(OH)
group and cyanide group has been generated in place of oxime
DFT-D3 analysis of DCCO and its phosgene interacted product
(DCC):
1
hydroxyl group. In order to support the sensing mechanism, H
13
Geometry optimized structures of DCCO and its phosgene
interacted product (DCC) have been obtained from density
functional theory (DFT) calculations (See Supplementary
Information). Considering the dispersion correction, DFT-D3 has
been employed during the calculation. Vibrational stretching
frequency of both DCCO and DCC has also been measured which
shows no negative vibration (See Supplementary Information).
Distribution of HOMO-LUMO oribitals for both of the compounds
are shown in Fig. 4.
NMR (Fig. S8-S11), C NMR (Fig. S12, S13) and mass spectra (Fig.
S14, S15) have been recorded. NMR and mass spectra of DCCO are
1
in accordance with its formation. H NMR spectrum of DCCO shows
the hydroxyl proton signal at 10.69 ppm and the formyl proton
signal at 9.07 ppm. These peaks disappear when triphosgene-
triethylamine have been added to it indicating the conversion of the
probe (DCCO) to probe-phosgene product (DCC).
ESI-mass spectra have also been recorded to verify the
formation of DCCO and DCC. Mass spectrum of DCCO exhibits an
ΔHOMO-LUMO for the DCCO and DCC is 3.438 eV and 3.448 eV,
respectively, which is almost similar. However, the NBO popluation
analysis of DCCO and DCC reveals that imine carbon and nitrogen
(C13-N3 in DCCO) has 0.03972 and -0.17827 charge which has
increased drastically to 0.34387 and -0.40999 (C31-N32 in DCC)
after interaction with phosgene due to changing the hybridisation
m/z peak at 261.1300 which may be attributed to the presence of
+
(
Probe + H ) species. Mass spectrum of phosegene mediated
product through the reaction of an equimolar mixture of probe and
triphosgene has been recorded. The mixture shows a major peak at
+
m/z 243.1126 [(DCC + H )] which corroborates the formation of
DCC.
(
See Supplementary Information). Significant increment of charge
Depending on functional moieties such as amino, hydroxyl,
sulfhydryl groups, etc. on the probe, phosgene produces different
end products after the reaction with the probes. When
distribution has resulted in enhanced charge transfer within the
molecule, in turn helps in fluorescence enhancement.
ethylenediamine derivatives are allowed to react with COCl , cyclic
2
Detection of Phosgene Gas with the Test Paper:
products such as imidazole, benzimidazole, oxazole derivatives, etc.
have been obtained with usually an extended delocalization feature To test practical applicability of the probe towards phosgene, dip
1
0h,10j,12b,14a,32
leading to high fluorescence increase.
Carboxylate and stick method has been followed. For this purpose TLC plates are
hydroxyl groups at suitable disposition can react with phosgene to dipped in the solution of DCCO. The test paper stripes have been
form coumarin derivative with the generation of strong placed into centrifuge tube with 20 ppm concentration of
18
fluorescence. With oxime functionality, the probe reacts with phosgene. Upon exposure of phosgene for 1 min, the color of test
13a
phosgene to give an amide derivative as the end product. There paper stripes changes from yellow to colorless under normal light
is another report with that hydroxylamine functionality, in where and from blue to green under UV light (Fig. 5). Thus, the presence of
28
phosgene converts it into nitrile group. As DCCO has similar oxime phosgene can be detected by test paper strips implying that the
functional group, it is reasonable to expect that the end product probe detects the phosgene at very low concentration.
Please do not adjust margins

Pl eNa es we dJ oo u nr no at l ao df jCu hs et mm i as tr rgy ins
Page 6 of 8
ARTICLE
Journal Name
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
View Article Online
DOI: 10.1039/D0NJ00645A
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Fig. 4. HOMO-1, HOMO, LUMO and LUMO+1 charge distribution for (a) DCCO and (b) DCC.
Detection of phosgene in the gas phase:
triphosgene and acid chlorides. The sensing reaction between DCCO
and phosgene is very fast and sensitive, and reaction almost is
completed within 1 min. This is the first sensor which can detect
phosgene in gas phase. The detection limit of the probe for
determination of phosgene is quite low as compared to the safety
level of phosgene recommended for humans. DCCO also shows very
good performance in dip stick method. Thus, it is an effective
practically portable probe not only for gas phase but also solid
phase detection of phosgene.
We have been interested to study this sensing in gas phase. For this
purpose probe (DCCO) coated TLC plate has been exposed in the
vapor of phosgene. From the Figure 9 we can see that probe coated
TLC plate turns to colorless from yellow after exposure with
phosgene vapor within 10 s. From this experiment it is clear that
DCCO is a very good probe towards phosgene and it also detects
phosgene in solution as well as in gas phase. From Matheson gas
data book, it is evident that 20 ppm phosgene can cause lung
diseases within 2 min, 90 ppm is rapidly fatal for exposures of 30
min or less. TLC plates coated with the probe can detect phosgene
only within 1 min. From this result it is clear that DCCO is very much
effective and fast to detect phosgene below concentration levels
related to a health risk.
31
Comparison of recognition mechanisms for detecting phosgene:
We compare some important parameters of previously reported
phosgene probe with our probe in supporting information. Our
probe shows some advantages over other reported probe while few
parameters of other probes are better in comparison to our work.
Excitation and emission wavelength in visible region is always better
for a probe. Our probe shows excitation and emission wavelength
in visible region whereas most of the reported probes are not. This
is of course a advantage property of our probe. Most of the probes
including our probe detect phosgene in few seconds, while few
probes detect phosgene slowly (within few mins). Some probes
have LOD values in the range of nM and ppb. Our probe has LOD
value of µM range. Our probe shows very good selectivity towards
various acid chlorides and important analytes.
Fig. 5 Color changes on the TLC plates under (i) ambient and (ii) UV
light in the presence of (a) DCCO (b) DCCO with phosgene.
Conflicts of interest
There are no conflicts to declare.
Conclusions
We have synthesized a new coumarin based chemodosimeter, 7- Acknowledgements
(diethylamino)-2-oxo-2H-chromene-3-carbaldehyde oxime (DCCO),
which can selectively detect phosgene over various nerve gas,
6
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 7 of 8
Pl eNa es we dJ oo u nr no at l ao df jCu hs et mm i as tr rgy ins
Journal Name
ARTICLE
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
2
016, 8, 22246−22252. (b) S. L. Wang, L. Zhong and Q. H.
View Article Online
SP acknowledges financial support through UGC DS Kothari
Postdoctoral Fellowship. PR wishes to thank for financial
support from RUSA 2.0, Jadavpur University.
Song, Chem. Commun., 2017, 53, 1530−1533. (c) Y. L.
DOI: 10.1039/D0NJ00645A
Huanga, W. Yea , Y. T. Sua , Z. Yi Wub and H. Zhenga, Dyes
and Pigments, 2020, 173, 107854.
14 (a) H. C. Xia, X. H. Xu and Q. H. Song, Anal. Chem., 2017, 89
,
4
192−4197. (b) Y. Zhang, A. Peng, X. Jie, Y. Lv, X. Wang and
References
Z. Tian, ACS Appl. Mater. Interfaces, 2017,
5 X. Wu, Z. Wu, Y. Yang and S. Han, Chem. Commun., 2012, 48
895−1897.
9, 13920−13927.
1
1
1
,
1
F. R. Sidell and J. Borak, Ann. Emerg. Med., 1992, 21
65−871.
(a) T. C. Marrs, Pharmacol. Ther., 1993, 58, 51−56. (b) L.
Szinicz, F. Worek, H. Thiermann, K. Kehe, S. Eckert and P.
Eyer, Toxicolog.,2007, 233, 23−30.
,
1
8
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
6 X. Zhou, Y. Zeng, C. Liyan, X. Wu and J. Yoon, Angew. Chem.,
Int. Ed., 2016, 55, 4729−4733.
2
7 W. Q. Zhang, K. Cheng, X. Yang, Q. Y. Li, H. Zhang, Z. Ma, H.
Lu, H. Wu and X. J. Wang, Org. Chem. Front., 2017,
4,
3
4
(a) D. Evison, D. Hinsley and P. Rice, Clin. Rev., 2002, 324
332−335. (b) K. Brown, Science, 2004, 305, 1228−1229.
,
1
719−1725.
1
1
8 P. Kundu, K. C. Hwang, Anal. Chem., 2012, 84, 4594−4597.
9 H. Xie, Y. Wu, F. Zeng, J. Chen and S. Wu, Chem. Commun.,
2017, 53, 9813.
(a) S. A. Cucinell and E. Arsenal, Arch. Environ. Health, 1974,
28, 272−275. (b) D. E. Rowe, R. J. Carroll and C. L. Day, J. Am.
Acad. Dermatol., 1992, 26, 976−990.
2
2
0 C. Wua , H. Xua, Y. Lia , R. Xiea , P. Lia, X. Panga , Z. Zhoua , B.
Gub , H. Lia and Y. Zhang, Talanta, 2019, 200, 78-83.
1 (a) Z. Li, Z. Xue, Z. Wu, J. Han and S. Han, Org. Biomol. Chem.,
5
6
J. L. Plahovinsak, M. R. Perry, K. A. Knostman, R. Segal and M.
C. Babin, Inhalation Toxicol., 2015, 27, 832–840.
(a) R. Price, Int. Org., 1995, 49, 73−103. (b) T. A. Ryan, C. E.
Ryan, A. Seddon and K. R. Seddon, Phosgene and Related
Carbonyl Halides; Topics in Inorganic and General Chemistry;
Elsevier Science: Amsterdam, 1996, 24, 3−932.
2
011, 9, 7652–7654; (b) Y. Q. Sun, J. Liu, H. Zhang, Y. Huo, X.
Lv, Y. Shi and W. Guo, J. Am. Chem. Soc., 2014, 136, 12520–
12523; (c) L. He, X. Yang, M. Ren, X. Kong, Y. Liu and W. Lin,
Chem. Commun., 2016, 52, 9582–9585.
7
(a) J. P. Hendershott, Am. Ind. Hyg. Assoc. J., 1986, 47
742−746. (b) A. Keil, H. Hernandez-Soto, R. J. Noll, M. Fico, L.
Gao, Z. Ouyang and R. G. Cooks, Anal. Chem., 2008, 80
34−741. (c) Y. Juillet, C. Dubois, F. Bintein, J. Dissard and A .
,
2
2
2 L. Pasquato, G. Modena, L. Cotarca, P. Delogu and S.
Mantovani, J. Org. Chem., 2000, 65, 8224–8228.
3 (a) K. A. Kumar, N. Renuka, G. Pavithra and G. V. Kumar, J.
Chem. Pharm. Res. 2015, 7, 67-81. (b) A. M. Yasameen, A. A.
,
7
Bossꢀe, Anal. Bioanal. Chem., 2014, 406, 5137−5145. (d) W.
S. Wu and V. S. Gaind, Analyst 1993, 118, 1285−1287. (e) R. J.
Rando, H. G. Poovey and S. N. Chang, J. Liq. Chromatogr.,
1993, 16, 3291−3309.
Ahmed, A. A. Kadhum and A. B. Mohamad, Sys Rev. Pharm.
017, , 24-30.
4 TURBOMOLE V7.3, a development of University of Karlsruhe
and Forschungszentrum Karlsruhe GmbH, 1989-2007,
TURBOMOLE GmbH, since 2007; available from
http://www.turbomole.com.
25 S. V. Shishkina, I. S. Konovalova, S. M. Kovalenko, P. V.
Trostianko, A. O. Geleverya and N. D. Bunyatyan, Cryst. Eng.
Comm., 2019, 21, 6945-6957.
6 (a) S. Halder, A. Barma, C. Rizzoli, P. Ghosh and P. Roy, ACS
Appl. Nano Mater., 2019, , 5469-5474; (b) S. Halder, P.
2
8
2
8
9
(a) H. B. Singh, D. Lillian and A. Appleby, Anal. Chem., 1975,
47, 860−864. (b) S. Virji, R. Kojima, J. D. Fowler, J. G.
Villanueva, R. B. Kaner and B. H. Weiller, Nano Res., 2009,
2,
1
35−142. (c) M. Davydova, A. Kromka, P. Exnar, M. Stuchlik,
K. Hruska, M. Vanecek and M. Kalbac, Phys. Status Solidi A,
2009, 206, 2070−2073.
2
(a) W. B. Crummett and J. D. McLean, Anal. Chem., 1965, 37
24− 425. (b) N. Nakano, A. Yamamoto, Y. Kobayashi and K.
Nagashima, Talanta, 1995, 42, 641−645. (c) D. Feng, Y.
Zhang, W. Shi, X. Li and H. Ma, Chem. Commun., 2010, 46
203−9205.
,
2
4
Ghosh, A.Hazra, P. Banerjee and P. Roy, New J. Chem., 2018,
42, 8408-8414.
7 Brouwer, A. M. Pure Appl. Chem., 2011, 83, 2213−2228.
8 T. Kim, B. Hwang, J. Bouffard and Y. Kim, Anal. Chem., 2017,
,
2
2
9
10 (a) H. Zhang and D. M. Rudkevich, Chem. Commun., 2007,
1238−1239. (b) P. Kundu and K. C. Hwang, Anal. Chem.,
89, 12837–12842.
2
9 M. Zhu, M. Yuan, X. Liu, J. Xu, J. Lv, C. Huang, H. Liu, Y. Li, S.
2
012, 84, 4594−4597. (c) X. Wu, Z. Wu, Y. Yang and S. Han,
Chem. Commun., 2012, 48, 1895−1897. (d) X. Zhou, Y. Zeng,
C. Liyan, X. Wu and J. Yoon, Angew. Chem., Int. Ed., 2016, 55
729−4733. (e) Y. Hu, L. Chen, H. Jung, Y. Zeng, S. Lee, K. M.
K. Swamy, X. Zhou, M. H. Kim and J. Yoon, ACS Appl. Mater.
Interfaces, 2016, , 22246−22252. (f) X. Zhou, Y. Zeng, C.
Liyan, X. Wu and J. Yoon, Angew. Chem. Int. Ed., 2016, 55
Wang and D. Zhu, Org. Lett., 2008, 10, 1481.
30 B. Valeur, Molecular Fluorescence. Principles and
Applications; Wiley-VCH:Weinheim, Germany; 2002.
1 W. Braker, A. L. Mossman, Matheson gas data book, 6th ed.;
Matheson: South Yarra, VIC, Australia, 1980; pp 596.
2 (a) Q. Hu, C. Duan, J. Wu, D. Su, L. Zeng and R. Sheng, Anal.
Chem., 2018, 90, 8686−8691; (b) W. Feng, S. Gong, E. Zhou,
X. Yin and G. Feng, Anal. Chim. Acta, 2018, 1029, 97-103; (c)
X.-Z. Wei, Y.-L. Fu, M.-J. Xue and Q.-H. Song, Org. Lett., 2019,
,
4
3
8
3
,
4
2
729 – 4733.(g) H. C. Xia, X. H. Xu and Q. H. Song, ACS Sens.,
017, , 178−182. (h) S. L. Wang, L. Zhong and Q. H. Song,
2
Chem. Commun., 2017, 53, 1530−1533. (i) H. C. Xia, X. H. Xu
and Q. H. Song, Anal. Chem., 2017, 89, 4192−4197. (j) Y.
Zhang, A. Peng, X. Jie, Y. Lv, X. Wang and Z, Tian, ACS Appl.
Mater. Interfaces, 2017,
Cheng, X. Yang, Q. Y. Li, H. Zhang, Z. Ma, H. Lu, H. Wu and X.
J. Wang, Org. Chem. Front., 2017, , 1719−1725. (l) H. Xie, Y.
Wu, F. Zeng, J. Chen and S. Wu, Chem. Commun., 2017, 53
9813—9816. (m) L. Chen, D. Wu, and J. Yoon, ACS Sens.,
21, 9497−9501.
9, 13920−13927. (k) W. Q. Zhang, K.
4
,
2018, 3, 27−43.
1
1
1 H. Babad and A. G. Zeiler, Chem. Rev., 1973, 73, 75−91.
2 (a) H. Zhang and D. M. Rudkevich, Chem. Commun., 2007,
1
238−1239. (b) H. C. Xia, X. H. Xu and Q. H. Song, ACS Sens.,
2
017, 2, 178−182.
13 (a) Y. Hu, L. Chen, H. Jung, Y. Zeng, S. Lee, K. M. K. Swamy, X.
Zhou, M. H. Kim and J. Yoon, ACS Appl. Mater. Interfaces,
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 7
Please do not adjust margins

New Journal of Chemistry
Page 8 of 8
View Article Online
DOI: 10.1039/D0NJ00645A
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
TOC only
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
A coumarin based compound, 7-(diethylamino)-2-oxo-2H-chromene-3-carbaldehyde oxime, acts
as a selective fluorescent chemodosimeter for phosgene gas in solution and as well as in gas
phase.