Ultrahigh-sensitive fluorescence dosimeters that use turn-on mode fluorescent diarylethenes

Article abstract of DOI:10.1016/j.tetlet.2020.152232

Turn-on mode fluorescent diarylethenes such as 1,2-bis(2-alkyl-6-phenyl-1-benzothiophene-1,1-dioxide-3-yl)perfluorocyclopentene were applied to ultrahigh-sensitive fluorescence dosimeters. The dosimeters can detect absorbed dose as low as 50 mGy. The sens

Full text of DOI:10.1016/j.tetlet.2020.152232

Journal Pre-proofs
Ultrahigh-sensitive fluorescence dosimeters that use turn-on mode fluorescent
diarylethenes
Tadatsugu Yamaguchi, Masahiro Irie
PII:
S0040-4039(20)30699-7
DOI:
Reference:
https://doi.org/10.1016/j.tetlet.2020.152232
TETL 152232
To appear in:
Tetrahedron Letters
Received Date:
Revised Date:
Accepted Date:
27 May 2020
5 July 2020
9 July 2020
Please cite this article as: Yamaguchi, T., Irie, M., Ultrahigh-sensitive fluorescence dosimeters that use turn-on
mode fluorescent diarylethenes, Tetrahedron Letters (2020), doi: https://doi.org/10.1016/j.tetlet.2020.152232
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Graphical Abstract
Ultrahigh-sensitive fluorescence dosimeters
that use turn-on mode fluorescent
diarylethenes
Tadatsugu Yamaguchi and Masahiro Irie
F2
F2
F2
S
F2
S
F2
F2
-rays
n-Bu
n-Bu
n-Bu
Ph
Ph
Ph
Ph
n-Bu
S
O O
S
O O
O
O O
O
nonfluorescent
fluorescent

1
Tetrahedron Letters
journal homepage: www.elsevier.com
Ultrahigh-sensitive fluorescence dosimeters that use turn-on mode fluorescent
diarylethenes
Tadatsugu Yamaguchia,  and Masahiro Irieb
aHyogo University of Teacher Education, Shimokume 942-1, Kato, Hyogo 673-1494, Japan
bRikkyo University, Research Center for Smart Molecules, 3-34-1 Toshima-ku, Tokyo 171-850, Japan
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
Turn-on mode fluorescent diarylethenes such as 1,2-bis(2-alkyl-6-phenyl-1-benzothiophene-1,1-
dioxide-3-yl)perfluorocyclopentene were applied to ultrahigh-sensitive fluorescence dosimeters.
The dosimeters can detect absorbed dose as low as 50 mGy. The sensitivity is 102–103 times
higher than that of conventional colour dosimeters.
Available online
2020 Elsevier Ltd. All rights reserved
Keywords:
Diarylethene
Fluorescence
Gamma-rays
Dosimeter
Introduction
and 1,2-bis(2-methyl-5-phenyl-4-thiazoyl)perfluorocyclopentene
(2), have been used as colour dosimeters, which change the
Film colour dosimeters are widely used for monitoring
absorbed dose in radiation processing, such as radiation curing
and radiation sterilization of medical products. It is strongly
desired to increase their sensitivity to enable applications in
medical radiation therapy and nuclear security monitoring [1–5].
colour from colourless to blue or red upon gamma-rays
irradiation [12–15]. Even when the absorbed dose is as low as
10 Gy, a clear colour change was observed [15].
Similar films and fibers containing photochromic spiropyran
dyes have also been used to detect X-rays absorbed dose in the
range of 10–100 Gy by the colour change [16,17]. Recently
polymer films containing 3a were reported to be effective for X-
rays detection in the dose range of 102–104 Gy [18].
Recently, various types of thermo luminescent as well as
optical stimulated luminescent dosimeters based on aluminum
oxide have been developed and used for monitoring
environmental radiation [6–8]. Although these inorganic
dosimeters can detect very low absorbed dose (~ mGy), they can
not be used for large-area detection. For large-area detection,
especially to get information concerning the images of absorbed
dose, it is required to develop highly sensitive polymer film
dosimeters.
F2
F2
F2
F2
F2
h
-rays
F2
R
Ph
Ph
R
R
Ph
h'
Ph
S
O O
S
O O
R
S
O O
S
Photochromic diarylethenes with heterocyclic aryl groups are
promising for use in optoelectronic devices because of their
thermally irreversible and fatigue-resistant properties [9–11].
Polystyrene films containing photochromic diarylethenes, such as
1,2-bis(2-methyl-5-phenyl-3-thienyl)perfluorocyclopentene (1)
O
O
3a: R=Me 4a: R=Et 5a: R=n-Bu
3a: R=Me 4a: R=Et 5a: R=n-Bu
Here, we report on ultrahigh-sensitive fluorescence
dosimeters that use turn-on mode fluorescent diarylethenes (4
and 5) and BaFCl:Eu fluorescent metal complexes [12,18–20].
F2
F2
F2
F2
F2
S
F2
S
The closed-ring isomers 4b and 5b in 1,4-dioxane emit
brilliant green fluorescence at around 540 nm (f=0.85–0.87)
upon excitation with 488 nm light [19–21]. The fluorescence
quantum yields of these diarylethenes are 1.4 times higher than
N
N
Ph
Ph
Ph
Ph
S
S
2a
1a
———
 Corresponding author. Tel.: +81-795-42-3722; e-mail: tyamagu@hyogo-u.ac.jp

2
Tetrahedron Letters
Fig.1. Absorption spectra of open-ring isomer 5a (solid line) and
closed-ring isomer 5b (dotted line), and fluorescence spectrum of the
closed-ring isomer upon excitation with 488 nm light (dot-dash line)
in toluene (1.6 × 10-5 mol/L).
Fig. 2. Absorbed dose versus relative fluorescence intensity at 530
nm for 5 in toluene (6.9 × 10-3 mol/L). The excitation wavelength
was 488 nm.
ing polystyrene and 4a or 5a onto a Teflon plastic plate (75 mm
× 25 mm). The film was dried under vacuum for 12 h and then
pressed between two glass plates at 140 °C for 90 min to obtain a
flat colourless film. The film obtained was sandwiched between
two BaFCl:Eu films (Toshiba Materials, TB-80). BaFCl:Eu
emits fluorescence in the 300–400 nm region upon gamma-rays
irradiation [15]. This emission sensitizes the isomerization of
diarylethene and results in an increase in the gamma-rays
sensitivity. Fig. 3 shows the fluorescence intensity changes of the
polystyrene film containing 5 before and after gamma-rays
irradiation. Fluorescence intensity increases with an increase in
the absorbed dose.
that of 3b in toluene. In addition, the colouration reactivity in a
polystyrene film was found to dramatically increase by replacing
methyl substituents at 2 and 2’-positions with butyl substituents
(See Supplementary data).
Results and discussion
The synthetic procedures and photochromism of diarylethene
derivatives 4 and 5 have already been reported [19–21]. Fig. 1
shows the absorption spectra of 5a (max: 296 nm,  2.1 × 104
M-1cm-1) and 5b (max: 450 nm) in toluene. There is no absorption
band for 5a in the visible region ( > 400 nm). The closed-ring
isomer 5b emits brilliant green fluorescence at 530 nm upon
excitation with 488 nm light. Similarly to 5a, diarylethene 4a
Table 1 shows the effect of BaFCl:Eu films on the radiation
induced isomerization of polymer films containing 4 and 5. The
isomerization of the diarylethenes in the polystyrene films was
remarkably enhanced by sandwiching the films with two
BaFCl:Eu films. The films containing 5 was found to exhibit
higher fluorescence intensity in comparison with the films
containing 4. The reactivity of the polystyrene films strongly
depends on the substituents at 2 and 2’-positions. The substit-
uents are known to affect the conformation of aryl-groups and the
reactivity in the solid state [21,22]. Diarylethene 3 cannot under-
(max
: 294 nm, 2.1 ×
104 M-1cm-1) also underwent
photochromism in toluene. The closed-ring isomer 4b (max: 450
nm) emitted brilliant green fluorescence at 530 nm upon
excitation with 488 nm light.
The open-ring isomers 4a and 5a were transformed into the
closed-ring isomers 4b and 5b upon gamma-rays irradiation in
toluene. The closed-ring isomers were stable and practically
never returned to the open-ring isomers even at 80 °C under
room light. Fig. 2 shows the fluorescence intensity change of 5
versus the absorbed dose of gamma-rays in toluene (6.9 ×
10-3 mol/L). The fluorescence was measured upon excitation with
488 nm light. The concentration change of the closed-ring
isomers was negligible during reading out the fluorescence
signals, because the ring opening quantum yield was very low
(1.2 × 10-3) [21]. Fluorescence intensity increases with an
increase in the absorbed dose. The relative fluorescence intensity
is 0.90 at 530 nm when the dose is 0.05 Gy, while it increases to
1.76 when the dose is 0.1 Gy. We carefully examined the
relationship between the relative fluorescence intensity at 530 nm
and the absorbance of the closed-ring isomer at 450 nm and
confirmed a linear relationship between them in the 0–100 range
of relative fluorescence intensity (see Supplementary data). In the
case of 4 in toluene (7.0 × 10-3 mol/L), when the dose was
0.05 Gy, the relative fluorescence intensity was 0.76, which is
slightly lower than that observed in a toluene solution of 5.
Fig. 3. Fluorescence intensity changes of a polystyrene film
On the basis of the above results obtained in toluene solutions,
we doped diarylethene 4 or 5 (50 mg, 5.0wt%) into a polystyrene
film (Polystyrene Japan HF-77, 950 mg, 95.0wt%). The film
dosimeter was prepared by casting the toluene solution contain-
containing
5
upon gamma-rays irradiation. The excitation
wavelength was 488 nm. The polystyrene film was sandwiched
between two BaFCl:Eu films.

3
Table 1.
Fluorescence emission intensities at 530 nm of polystyrene films containing 4 and 5. The excitation wavelength was 488 nm.
Compound
Sandwiched material
Dose
Fluorescence Intensity(relative)
4
4
4
4
5
5
5
5
5
5
None
1.0 Gy
1.0 Gy
0.5 Gy
0.5 Gy
1.0 Gy
1.0 Gy
0.5 Gy
0.5 Gy
0.1 Gy
0.1 Gy
1.91
5.95
0.69
3.07
2.87
8.76
0.92
3.96
0.21
1.10
BaFCl:Eu
None
BaFCl:Eu
None
BaFCl:Eu
None
BaFCl:Eu
None
BaFCl:Eu
go the cyclization reaction in the crystalline phase, while
diarylethenes 4 and 5 undergo the reactions. The stable
conformation of 3a is parallel one, which can not undergo the
cyclization reaction. On the other hand, 4a and 5a take an anti-
parallel conformation, which can efficiently undergo the reaction
[23]. The reactivity differences among 3, 4 and 5 are well
explained by the conformation of the open-ring isomers.
Appendix A. Supplementary data
Supplementary data to this article can be found online at
https://doi.org/10.1016/xxxxx.
References
[1] M. J. Buston, P. K. Yu, T. Chenung, P. Metcalfe, Mater. Sci. Eng. R 41
(2003) 61-120.
The fluorescence intensity change indicates that the energy
absorbed by solvents or polymer matrices migrates and is
transferred to the open-ring isomers of the diarylethenes [12–15].
The absorbed high energy is deactivated by such processes as the
photoelectric effect, the Compton effect and pair production, and
finally excites toluene or phenyl side groups of polystyrene and
metal complexes. The excited phenyl rings and metal complexes
transfer their energies to diarylethene molecules non-radiatively
as well as radiatively. The excited diarylethene molecules
undergo the cyclization reactions to produce the fluorescent
closed-ring isomers. The ultrahigh-sensitivity is achieved by the
fine tuning of chemical structures of the diarylethenes.
[2] M. J. Butson. T. Cheung, P. K. Yu Australas. Phys. Eng. Sci. Med. 37
(2004) 230.
[3] B. Whittaker, Manual on Radiation Dosimetry eds. N. W. Holm, R. J.
Berry, Marcel Dekker, New York, 1970.
[4] National Research Council, Health Risks from Exposure to Low Levels of
Ionizing Radiation, The National Academies Press, Washington, 2006.
[5] J-M. Han, M. Xu, B. Wang, N. Wu, X. Yang, H. Yang, B. J. Salter, J.
Am. Chem. Soc. 136 (2014) 5090–5096.
[6] I. Kobayashi, T. Okazaki, K. Yajima, H. Yasuda, Prog. Nucl. Sci. Technol.
3 (2012) 79–81.
Conclusion
[7] C. F. Conheady, F. M. Gagliardi, T. Ackerly, Australas. Phys. Eng. Sci.
Med. 38 (2015) 447–453.
In summary, diarylethene derivatives 4a and 5a were found
to undergo isomerization reactions to closed-ring isomers 4b and
5b in toluene solutions and in polystyrene films upon irradiation
with gamma-rays. The closed-ring isomers produced by -
irradiation were stable and emitted fluorescence. It is possible to
estimate the absorbed dose from the linear relationship between
the absorbed dose and the fluorescence intensity. Even when the
absorbed dose is as low as 50 mGy, 4 and 5 emitted distinct
fluorescence in both toluene solutions and polystyrene films. The
sensitivity of the dosimeters composed of 4 or 5 and fluorescent
metal complexes was 102–103 times higher than that of
conventional colour dosimeters. The dosimeters have potential to
be used in medical radiation therapy as well as in nuclear security
monitoring, where low doses are required to be measured.
[8] E. Einbergs, A. Zolotarjovs, I. Bite, K. Laganovska, K. Auzins, K. Smits,
L. Trinkler, Ceramics 2 (2019) 525–535.
[9] M. Irie, M. Mohri, J. Org. Chem. 53 (1988) 803-808.
[10] M. Irie, Chem. Rev. 100 (2000) 1685–1715.
[11] M. Irie, T. Fukaminato, K. Matsuda, S. Kobatake, Chem. Rev. 114
(2014) 12174–12277.
[12] S. Irie, T. Yamaguchi, H. Nakazumi, S. Kobatake, M. Irie, Bull. Chem.
Soc. Jpn. 72 (1999) 1139–1142.
[13] S. Irie, M. Irie, Bull. Chem. Soc. Jpn. 73 (2000) 2385–2388.
[14] S. Irie, M. Irie, Bull. Chem. Soc. Jpn. 75 (2002) 2071–2075.
[15] S. Irie, M. Irie, Chem. Lett. 35 (2006) 1434–1435.
Acknowledgements
[16] K. Kinashi, Y. Miyashita, K. Ishida, Y. Ueda, J. Phys. Org. Chem. 25
This work was partly supported by JSPS KAKENHI Grant
Number JP19K03080. We are grateful to Dr. Takao Kojima for
gamma-rays irradiation.
(2012) 427–430.
[17] K. Kinashi, Y. Miyamae, R. Nakamura, W. Sakai, N. Tsutsumi, H.
Yamane, G. Hatsukano, M. Ozaki, K. Jimbo, T. Okabe, Chem. Commun.
51 (2015) 11170–11173.

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Tetrahedron
[18] K. Asai, T. Ubukata, M. Koshimizu, Y. Fujimoto, T. Yanagawa, H.
[21] M. Irie, M. Morimoto, Bull. Chem. Soc. Jpn. 91 (2018) 237–250.
Kawamoto, K. Asai, J. Mater. Sci. 30 (2019) 10211–10216.
[22] T. Yamaguchi, M. Irie, J. Photochem. Photbiol. A: Chemistry 178 (2006)
162-169.
[19] K. Uno, H. Niikura, M. Morimoto, Y. Ishibashi, H. Miyasaka, M. Irie, J.
Am. Chem. Soc. 133 (2011) 13558–13564.
[23] M. Morimoto, private communication.
[20] Y. Takagi, T. Kunishi, T. Katayama, Y. Ishibashi, H. Miyasaka, M.
Morimoto, M. Irie, Photochem. Photobiol. Sci. 11 (2012) 1661–1665.

5
Highlights
Ultrahigh-sensitivity dosimeters using turn-on
mode fluorescent diarylethenes
Detection of absorbed dose as low as 50 mGy for
gamma-rays
Fluorescence in both toluene solution and
polystyrene film by gamma-irradiation
100-1000 times more sensitive than conventional
colour dosimeters