Compd abs / nm em / nm F dec / 10-2 kr / 108 M sec-1 a  / 10-2 CO yield ISC
1B 456 635 (0.16 ± 0.01) (2.1 ± 0.1) (4.7 ± 0.2) (7.0 ± 0.2) 61 ± 3 ‐
2B 461 635 (0.21 ± 0.01) (1.9 ± 0.1) (6.5 ± 0.2) (5.5 ± 0.8) 80 ± 5 ‐
3B 465 635 (0.23 ± 0.02) (2.3 ± 0.2) (4.9 ± 0.18) (7.0 ± 0.2) 45 ± 2 ‐
4B 460 635 (0.18 ± 0.01) (2.2 ± 0.1) (2.6 ± 0.37) (7.9 ± 0.3) 54 ± 1 ‐
5B 461 635 (0.19 ± 0.01) (1.7 ± 0.1) (3.6 ± 0.27) (4.9 ± 0.2) 90 ± 2 ‐
6B 482 698 (0.039 ± 0.008) (2.1 ± 0.1) (3.9 ± 0.03) (9.5 ± 0.3) 50 ± 3 ‐
7B 472 634 (0.20 ± 0.01) (2.1 ± 0.2) (5.5 ± 0.29) (5.3 ± 0.6) 72 ± 2 ‐
8B 511 705 (0.021 ± 0.003) (1.3 ± 0.1) - (2.5 ± 0.4)* 83 ± 3 * ‐
9B 482 694 (0.0003 ± 0.0001) (1.1 ± 0.1) - (1.1 ± 0.2)* 51 ± 1* ‐
F dec  ISC CO yieldF dec  ISC CO yield
The evaluation of effects of different groups at different positions on the photochemical properties of hydroxyflavones shows that the reactivity is significantly
influenced especially by the groups on the naphthalene ring. The major effects involve the shift of the acid-base equilibria, the efficiency of intersystem crossing, and the
excited-state lifetimes.
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I / Normalized
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The well-established toxicity of carbon monoxide (CO) appears contradictory with its possible therapeutical function.
Indeed, it has recently been discovered that CO is produced endogenously.
Studies of the effects of CO have demonstrated its potential to produce a variety of beneficial health outcomes, including
anti-inflammatory, anti-bacterial effects, and antiproliferative effects on cancer.1 Therefore, CO-releasing molecules
(CORMs), biologically compatible agents allowing for a defined administration of CO into living organisms to circumvent its
acute toxicity, are of special interest.2 A precise spatial and temporal control over the CO release can be achieved via
activation of the CORM (photoCORMs) by light.
A good photoCORM should be stable under ambient conditions and soluble in aerobic aqueous environments. It should
release CO using light at wavelengths that do not have the potential to impart cellular damage and may exhibit fluorescence
to enable tracking in the cell.
Understanding the mechanism is a key step for designing new derivatives with improved properties for biological
applications, such as water solubility, higher quantum yields and the absorption spectra in the visible light region.
The detailed mechanism of the photochemically induced CO release from 3-hydroxy-2-phenyl-benzo[g]chromen-4-one
has been studied in our group.3 A deeper understanding is presented in this structure/reactivity study of CO-photorelease
reactions from this class of compounds with the aim to design better photoCORMs for biological applications.
Acknowledgement:
This work was supported by the Czech Science Foundation (GA18-12477S). The research was also supported by the RECETOX Research Infrastructure (LM2015051 and CZ.02.1.01/0.0/0.0/16_013/0001761).
1 L. Vítek, H. Gbelcová, L. Muchová, R. Koníčková, J. Šuk, M. Zadinova, Z. Knejzlík, S. Ahmad, T. Fujisawa, A. Ahmed, T. Ruml, Digestive and Liver Disease 2014, 46
369-375.
2 C. C. Romao, W. A. Blatter, J. D. Seixas, G. J. L. Bernades, Chem. Soc. Rev. 2012, 41, 3571-3583
3 Russo M., Štacko P., Nachtigallová D., Klán P J. Org. Chem. 2020, 85, 3527-3537.
photochem.sci.muni.cz
Uncovering of the Structure and Reactivity Correlation of COPhotorelease
from 3-Hydroxyflavone-Based Acid-Base Forms
Marina Russo,1 Peter Štacko, 1 Lenka Karpíšková,1 Petr Klán, 1 *
1Department of Chemistry and RECETOX, Masaryk University, Kamenice 5, 625 00, Brno Czech Republic
e-mail:russomarina.mr@gmail.com, *klan@sci.muni.cz, photochem.sci.muni.cz
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Emission
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O
O
OH
h
O
COOH
O
O
Ph
3
1Z*
1
1A* 1
1Z*
ESIPT ISC
O
OH
O
3 *
anaerobic
r = 1.2 10 4
+ CO
(55%) (52%)
3
O2
+ CO
(91%) (80%)
= 0.14
aerobic
r = 0.031
PhO
1A
1
O2
3
O2
O
OH
O
O
O
O
Ph
O
HO
Compd abs / nm em / nm F dec / 10-2 kr / 105 M sec-1 a  / 10-2 CO yield ISC
1A 403 598 (0.72 ± 0.06) (3.0 ± 0.2) (4.3 ± 0.1) (14.0 ± 0.2) 80 ± 5 0.23 ± 0.03
2A 406 605 (0.52 ± 0.02) (3.6 ± 0.4) (1.3 ± 0.23) (11.0 ± 0.8) 80 ± 5 ‐
3A 409 612 (0.32 ± 0.02) (2.4 ± 0.3) (0.56 ± 0.01) (28.4 ± 0.4) 50 ± 4 ‐
4A 410 603 (0.63 ± 0.05) (3.6 ± 0.2) (2.1 ± 0.1) (11.0 ± 0.6) 82 ± 5 0.24 ± 0.02
5A 406 599 (0.60 ± 0.03) (1.7 ± 0.3) (13.0 ± 0.6) (7.6 ± 0.1) 65 ± 6 0.22 ± 0.03
6A 411 622 (0.13 ± 0.01) (13.0 ± 0.9) (2.9 ± 0.14) (31.0 ± 2.1) 95 ± 5 0.79 ± 0.04
7A 438 571 (0.25 ± 0.034) (0.82 ± 0.06) (28.0 ± 5.2) (2.82 ± 0.05) 60 ± 1 ‐
8A 455 613 (0.085 ± 0.006) (1.3 ± 0.4) - (8.6 ± 0.6) * 85 ± 3 * ‐
9A 414 620 (0.09 ± 0.01) (16.0 ± 1.1) - (24.30 ± 0.02) * 95 ± 5 * ‐
2 3 4 5
6 7 8 9
1
Acid form Basic form
IV. Conclusion
V. References
I. Photophysical and Photochemical Properties
III. Jablonski Diagram
Heavy atom effect on naphthalene ring
F dec  ISC CO yieldF dec  ISC CO yield
EDG effect
F dec  CO yieldF dec  CO yield
Heavy atom effect on naphthalene ring
F dec  ISC CO yieldF dec  ISC CO yield
EDG effect
~~ ~~
~~ ~~
II. Substituent Effects
Acid form
Basic form
Heavy atom effect on phenyl ring
Heavy atom effect phenyl ring
F dec  ISC CO yieldF dec  ISC CO yield
F dec  CO yieldF dec  CO yield
~~ ~~ ~~ ~~ ~~
~~ ~~ ~~ ~~