Visible light-induced photodeoxygenation of polycyclic selenophene Se-oxides

Article abstract of DOI:10.1002/poc.4144

Photodeoxygenation of dibenzothiophene S-oxide (DBTO) is believed to produce ground-state atomic oxygen [O(³P)] in solution. Compared with other reactive oxygen species (ROS), O(³P) is a unique oxidant as it is potent and selective. Derivatives of DBTO have been used as O(³P)-precursors to oxidize variety of molecules, including plasmid DNA, proteins, lipids, thiols, and other small organic molecules. Unfortunately, the photodeoxygenation of DBTO requires ultraviolet irradiation, which is not an ideal wavelength range for biological systems, and has a low quantum yield of approximately 0.003. In this work, benzo[b]naphtho[1,2-d]selenophene Se-oxide, benzo[b]naphtho[2,1-d]selenophene Se-oxide, dinaphtho[2,3-b:2’,3’-d]selenophene Se-oxide, and perylo[1,12-b,c,d]selenophene Se-oxide were synthesized, and their ability to utilize visible light for generating O(³P) was interrogated. Benzo[b]naphtho[1,2-d]selenophene Se-oxide produces O(³P) upon irradiation centered at 420 nm. Additionally, benzo[b]naphtho[1,2-d]selenophene Se-oxide, benzo[b]naphtho[2,1-d]selenophene Se-oxide, and dinaphtho[2,3-b:2’,3’-d]selenophene Se-oxide produce O(³P) when irradiated with UVA light and have quantum yields of photodeoxygenation ranging from 0.009 to 0.33. This work increases the utility of photodeoxygenation by extending the range of wavelengths that can be used to generate O(³P) in solution.

Full text of DOI:10.1002/poc.4144

Received: 2 June 2020
DOI: 10.1002/poc.4144
Revised: 3 September 2020
Accepted: 6 September 2020
R E S E A R C H A R T I C L E
Visible light-induced photodeoxygenation of polycyclic
selenophene Se-oxides
Satyanarayana M. Chintala | John C. Throgmorton
Ryan D. McCulla
| Peter F. Maness |
Department of Chemistry, Saint Louis
Abstract
University, St. Louis, MO, USA
Photodeoxygenation of dibenzothiophene S-oxide (DBTO) is believed to pro-
Correspondence
3
duce ground-state atomic oxygen [O( P)] in solution. Compared with other
Ryan D. McCulla, Department of
Chemistry, Saint Louis University, 3501
Laclede Ave. St. Louis, MO 63103, USA.
Email: ryan.mcculla@slu.edu
3
reactive oxygen species (ROS), O( P) is a unique oxidant as it is potent and
3
selective. Derivatives of DBTO have been used as O( P)-precursors to oxidize
variety of molecules, including plasmid DNA, proteins, lipids, thiols, and other
small organic molecules. Unfortunately, the photodeoxygenation of DBTO
requires ultraviolet irradiation, which is not an ideal wavelength range for bio-
logical systems, and has a low quantum yield of approximately 0.003. In this
work, benzo[b]naphtho[1,2-d]selenophene Se-oxide, benzo[b]naphtho[2,1-d]
selenophene Se-oxide, dinaphtho[2,3-b:2’,3’-d]selenophene Se-oxide, and
perylo[1,12-b,c,d]selenophene Se-oxide were synthesized, and their ability to
Funding information
National Science Foundation, Grant/
Award Number: CHE-1900417
3
utilize visible light for generating O( P) was interrogated. Benzo[b]-
3
naphtho[1,2-d]selenophene Se-oxide produces O( P) upon irradiation centered
at 420 nm. Additionally, benzo[b]naphtho[1,2-d]selenophene Se-oxide, benzo
[
b]naphtho[2,1-d]selenophene
Se-oxide,
and
dinaphtho[2,3-b:2’,3’-d]
3
selenophene Se-oxide produce O( P) when irradiated with UVA light and have
quantum yields of photodeoxygenation ranging from 0.009 to 0.33. This work
increases the utility of photodeoxygenation by extending the range of wave-
3
lengths that can be used to generate O( P) in solution.
K E Y W O R D S
photooxidation, photodeoxygenation, selenoxide
1
| INTRODUCTION
microwave discharge of a helium and molecular oxygen
[
9,11–13]
mixture.
In contrast to the gas phase, the reactivity
3
3
Ground-state atomic oxygen [O( P)] is an important
oxidant because of its selective reactivity and strong
oxidative properties.
of O( P) in the condensed phase is yet to be thoroughly
explored due to the dearth of clean and efficient methods
[1–7]
3
3
The reactivity of O( P) has been
of generating O( P) in the condensed phase.
investigated extensively in the gas phase due to its impor-
Photodeoxygenation of certain aryl sulfoxides is the
[
8–10]
3
tance in industrial and environmental chemistries.
most commonly used method for generating O( P)
3
[4,5,14,15]
3
The widely used methods for producing O( P) in gas
in solution.
Other sources of O( P) in the
phase are decomposition of N O by mercury photosensi-
condensed phase include photodeoxygenation of
2
tization, photolysis of liquid CO2 by γ-rays, and
dibenzoselenophene Se-oxide (DBSeO), pyridine N-oxide,
J Phys Org Chem. 2020;e4144.
wileyonlinelibrary.com/journal/poc
© 2020 John Wiley & Sons, Ltd.
1 of 14
https://doi.org/10.1002/poc.4144

2
of 14
CHINTALA ET AL.
[
1,5,6]
and oxo-anions.
Irradiation of pyridine N-oxide at
DBTO derivatives that are water-soluble, lipophilic,
photodeoxygenate more quickly, or absorb visible wave-
3
3
08-nm light yields 95% oxaziridine and only 5% O( P)
and pyridine. Photodeoxygenation of DBSeO generates
O( P) and dibenzoselenophene (DBSe) but also yields the
undesired selenic ester as shown in Figure 1. Photolysis
of oxo-anions produces O( P) but requires 193 nm,
48.5 nm, or 308 nm light and generates ozone as a
Photodeoxygenation of dibenzothiophene
S-oxide (DBTO) is a clean source of O( P) as it produces
solely O( P) and dibenzothiophene (DBT). However,
this method requires high-energy UVA irradiation and
has a low quantum yield of photodeoxygenation of
.003.
In the condensed phase, O( P) has been shown to
cause deoxyribonucleic acid (DNA) strand scission in
plasmid DNA and selectively oxidize cysteine residues of
adenosine-5 -phosphosulfate kinase (APSK).
oxidation of low-density lipoprotein (LDL) by O( P)
yielded primarily fatty aldehydes.
selectively oxidizes the tertiary carbon of 2-methyl-
butane to the corresponding alcohol and benzene to
[1]
length light have been synthesized to suit the required
3
[3,25,26]
experimental conditions.
Sulfonic acids and
[6]
hydroxymethyl groups have been added to DBTO to
3
3
improve water solubility and to allow generation of O( P)
[
3,18,25]
2
in water.
Alkyl groups have been substituted on
[16]
[26]
byproduct.
the DBTO structure to enhance its lipophilicity.
When
3
a higher quantum yield of photodeoxygenation was
required, sulfur in the structure of DBTO was replaced
3
[5]
[
6,27]
with selenium.
The change of sulfur to selenium in
the DBTO structure improved the quantum yield of
[5]
[6]
0
photodeoxygenation to approximately 0.1. To extend
3
the ultraviolet-visible (UV-Vis) absorption into the visible
wavelength range, benzannulation of the DBTO structure
[
14,28]
has been employed.
However, benzannulated DBTO
0
[17,18]
The
derivatives displayed other photodeoxygenation mecha-
nisms in addition to the unimolecular S O bond scission
3
[19]
3
3
Additionally, O( P)
mechanism that yields O( P), and none appeared to
3
[28,29]
generate O( P) upon visible light irradiation.
The
combination of creating selenium containing analogs
[4]
3
phenol.
These results show that O( P) could be a
potential oxidant in organic synthesis and be used to
probe oxidative stress-induced biological pathways.
Despite the advantages of utilizing O( P), the neces-
sity of UVA light combined with low photodeoxygenation
with π-extended chromophores was postulated to create
3
O( P)-precursors that have a high quantum yield of
photodeoxygenation upon irradiation with visible light.
To examine this hypothesis, polycyclic aryl selenoxides
1 to 4 were synthesized, and their photodeoxygenation
processes were studied (Figure 2).
3
3
quantum yields of currently available O( P)-precursors
have hindered the application of O( P) in organic synthe-
3
sis, biochemistry, and microbiology. Previously, photo-
deoxygenation of 2,8-dihydroxymethyldibenzothiophene
2 | EXPERIMENTAL SECTION
2.1 | Materials
3
S-oxide, which is presumed to generate O( P), has been
3
[19]
used to study the effect of O( P) in RAW 264.7 cells.
However, UVA is not a preferable range of wavelengths
to use with biomolecules and cells as it causes degrada-
tion of biomolecules, and longer exposure of UVA can
All chemicals were purchased from Sigma Aldrich,
Fisher, Arctom Chemicals, Oakwood chemicals, or Ark
Pharm and used without further purification except as
specified. Anhydrous N-Methyl-2-pyrrolidone (NMP)
obtained from Sigma Aldrich was further dried using 3-Å
molecular sieves. HPLC-grade toluene, benzene, and ace-
tonitrile were used for common intermediate experi-
ments. Selenides 1Se to 4Se and DBSe except for 2Se
[20–24]
3
lead to cell death.
In this work, O( P)-precursors
that are expected to deoxygenate upon irradiation with
visible light and have high quantum yields of photo-
deoxygenation are investigated.
3
One strategy to develop an O( P)-precursor that deox-
ygenates upon irradiation with visible light is to modify
the structure of DBTO. Previously, the DBTO structure
has been modified in various ways depending on the
objective of the particular research. For example,
[28,30–37]
were synthesized according to the literature.
Compounds 1 to 4, DBSeO, diphenyl selenoxide, and
DBTO were synthesized by oxidizing 1Se to 4Se, DBSe,
FIGURE 1 Photodeoxygenation of dibenzothiophene S-
oxide (DBTO) and dibenzoselenophene Se-oxide (DBSeO)

CHINTALA ET AL.
3 of 14
FIGURE 2 Aryl
selenoxides and selenides used
in this study
diphenyl selenide, and DBT, respectively. Selenoxide
conversions (<20%). HPLC was used to analyze the solu-
tions before and after photolysis. Photorearrangement of
azoxybenzene to 2-hydroxyazobenzene was used as an
actinometer for wavelengths less than 390 nm, and for
wavelengths above 390 nm, K[Cr (NH ) (NCS) ] was
3
used for all the experiments that had less than 10%
isomer content. All the information about the synthesis
of 1 to 4 are provided below in this section.
3
2
4
[
38,39]
used.
2.2 | General methods
Shimadzu GC-2010 Plus was used for GC-FID analysis.
Absorption spectra were obtained using a Shimadzu
UV-1800 UV spectrophotometer. A Bruker DRX-400
NMR was used to obtain NMR spectra of compounds 1 to
2.4 | Common intermediate experiments
One- to 10-millimolar solutions of DBTO and compounds
1 to 4 were prepared. The solutions were sparged with
argon in quartz cuvettes (1 cm × 1 cm) with long stems.
The degassed solutions were irradiated with either UVA
bulbs (Luzchem LZC-UVA bulbs centered at 350 nm) or
bulbs centered at 420 nm (Luzchem LZC-420 nm). The
common intermediate experiments with 420 nm irradia-
tion were also performed in glass test tubes. The changes
in the concentrations of products were analyzed using
GC-FID, and changes in the concentration of DBT and
corresponding selenides of 1 to 4 were analyzed using
HPLC. Dodecane was used as an internal standard.
4. HPLC analysis was conducted using an Agilent 1200
Series HPLC with a quaternary pump, diode-array
detector, and a Higgins Analytical CLIPEUS C18 column
(5 μm, 150 × 4.6 4.6 mm). A Shimadzu GCMS equipped
with QP2010S was used for gas chromatography-mass
spectrometry (GC-MS) analysis.
2.3 | Photodeoxygenation quantum yield
determination
One- to five-millimolar solutions of compounds 1 to
4
were prepared in HPLC grade acetonitrile or ethanol
3 | RESULTS AND DISCUSSION
3.1 | Synthesis of compounds 1 to 4
Compounds 1Se and 4Se were synthesized according to
for determining the quantum yields of photo-
deoxygenation below 390 nm. Saturated solutions of
1
and 3 in ethanol were used for determining the quan-
tum yields of photodeoxygenation at 400 ± 3 nm. The
optical densities of the prepared solutions were ensured
to be greater than 2 at the desired wavelength for
photolysis. Four milliliters of prepared samples in quartz
cuvettes (1 cm × 1 cm) cells with long stem were
degassed with argon for 10 min. The degassed solutions
in quartz cuvettes were irradiated using a 75W Xenon
lamp focused on a monochromator (Photon Technologies
International). The reactions were carried out to low
[
30–33]
previously reported procedures.
Compounds 1 and
4 were prepared by oxidation of 1Se and 4Se,
respectively, with 3-chloroperoxybenzoic acid (mCPBA)
in dichloromethane (DCM). For selenide 4Se, the
reported procedure yielded product, only if anhydrous
NMP was used as the solvent.
The previously reported method for synthesis of DBSe
[
6]
has multiple steps. In this work, DBSe was prepared

4
of 14
CHINTALA ET AL.
3
using a similar procedure to 3Se, which is a one-pot, two-
this work is to prepare O( P)-precursors that absorb and
photodeoxygenate in the visible wavelength region. The
UV-Vis spectra of compounds 1 to 4 were obtained to
determine if visible light was absorbed by 1 to 4. Com-
pounds 1 to 4 had cutoff wavelengths (ε < 50) that are
significantly higher than DBTO (365 nm) and DBSeO
(354 nm). Compounds 1 and 2 had cutoff wavelengths of
400 nm and 376 nm, respectively, and selenoxides 3 and
4 absorptions extend above 400 nm with cutoff wave-
lengths of 433 nm and 533 nm, respectively (Figure 3).
[40]
steps process, as shown in Scheme 1.
DBSe involved the reaction of 2,2 -dibromo-1,1 -biphenyl
with tert-butyllithium (t-BuLi) at −78 C in anhydrous
The synthesis of
0
0
ꢀ
tetrahydrofuran (THF) followed by addition of prepared
SeCl , which was prepared by addition of selenium to
2
SO Cl . DBSeO was obtained by oxidation of DBSe with
2
2
mCPBA.
Selenoxide 2 was synthesized in four steps as shown
in Scheme 2. The first step involved selenobromination of
phenyl acetylene using HBr, SeO , and cyclohexene in
2
1
,4-dioxane to yield 3-bromo-benzo[b]selenophene
[30]
(
2A).
A Suzuki-Miyaura reaction was utilized in the
3.3 | Quantum yield of
photodeoxygenation
second step for coupling trans-2-phenylvinylboronic
acid with 2A to yield 3-(2-phenylethenyl)-benzo[b]
selenophene (2B). Selenide, 2Se, was prepared by
photocyclization of 2B in the presence of iodine and
propylene oxide under UVA irradiation. This method to
synthesize 2Se has been previously used to prepare
dinaphthothiophenes and benzonaphthothiophenes.
The photodeoxygenation of DBTO is the most com-
monly used clean source of O( P) in the condensed
3
phase. However, it suffers from low quantum yield of
photodeoxygenation. The selenoxides 1 to 4 were syn-
thesized to improve the quantum yield of photo-
deoxygenation and therefore make the generation of
[28,34–36]
The final step was oxidation of 2Se by mCPBA
3
in DCM.
Selenoxide 3 was prepared by slightly modifying the
O( P) more efficient. To verify whether 1 to 4 undergo
photodeoxygenation more efficiently, the quantum
yields of photodeoxygenation of compounds 1 to 4 were
measured upon UV irradiation. These experiments were
performed in ethanol and acetonitrile. For individual
selenoxides, the wavelength with maximum absorbance
above 320 nm in the UV-Vis spectrum was used for
irradiation. The quantum yields of photodeoxygenation
were calculated based on the increase in the selenide
concentration and are listed in Table 1. The values
ranged from 0.009 to 0.33. Among the compounds
tested, selenoxide 2 had the highest quantum yield of
photodeoxygenation, which was 0.33, and selenoxide
[37,40]
reported synthetic procedure.
The modified proce-
dure is shown in Scheme 3. The synthesis of selenide 3Se
yielded approximately 90% selenide 3Se and 10% of an
isomer, which had the same molecular mass as 3Se. After
purification using column chromatography, recrystalliza-
tion of 3Se in 17% DCM in hexanes eliminated the
unidentified isomer. However, the isolated yield after
recrystallization was low (ꢁ10%). Therefore, to prepare
selenoxide 3, selenide 3Se containing 10% isomer, or less,
was used. Selenoxide 3 prepared by oxidation of 3Se
using mCPBA had less than 10% isomer.
4
had the lowest quantum yield of 0.009. The quantum
yield of photodeoxygenation of compound 4 was only
obtained in ethanol, as it had poor solubility in acetoni-
trile. HPLC analysis was used to determine the increase
in the selenide concentration used for calculating the
quantum yield of photodeoxygenation. Since irradiation
3
.2 | UV-Vis spectra of compounds 1 to 4
3
The currently available O( P)-precursors require UV light
irradiation for producing O( P). One of the objectives of
3
SCHEME 1 Synthesis of compound dibenzoselenophene Se-oxide (DBSeO)

CHINTALA ET AL.
5 of 14
SCHEME 2 Synthesis of compound 2
of DBSeO leads to DBSe and ring expansion to a selenic
ester as shown in Figure 1, multiple products were pos-
sible upon irradiation of 1 to 4. However, no other sig-
nificant products were observed in HPLC analysis after
photolysis of 1, 3, and 4 other than their corresponding
selenides. This is surprising as photodeoxygenation of
DBSeO yields DBSe and a ring-expanded selenic ester
product, and thus, it was anticipated that selenic esters
might form for 1 to 4. Photolysis of 2 yielded
corresponding selenide 2Se and a new compound 2X.
The H NMR of purified compound 2X, which is
1
included in the Supporting Information, had peaks with
chemical shifts in the aromatic region and resembled a
polymer. To measure the light flux of the lamp
used, photorearrangement of azoxybenzene to
[38]
2-hydroxyazobenzene was used as the actinometer.

6
of 14
CHINTALA ET AL.
SCHEME 3 Synthesis of compound 3
FIGURE 3 Ultraviolet-visible (UV-Vis)
absorption spectra of dibenzoselenophene
Se-oxide (DBSeO) and 1 to 4
TABLE 1 Quantum yields of photodeoxygenation of DBSeO and 1 to 4
b
Quantum yield Φ+selenide
Entry
Compound
Acetonitrile
Ethanol
Wavelength (nm)
a
1
2
3
4
5
DBSeO
-
0.13 ± 0.01
0.21 ± 0.01
0.33 ± 0.15
0.19 ± 0.02
320 ± 12
356 ± 6
340 ± 6
330 ± 6
320 ± 6
1
2
3
4
0.14 ± 0.03
0.25 ± 0.01
0.23 ± 0.04
-
0.009 ± 0.006
Abbreviation: DBSeO, dibenzoselenophene Se-oxide.
a
[6]
Quantum yield of photodeoxygenation of DBSeO from McCulla and Jenks.
b
Quantum yields reported are within 95% confidence intervals and were calculated by increase in selenide concentration.
[
5,6,14,27,28]
3.4 | Photochemistry upon UVA
specific ratio.
Two different chemical reactions
irradiation
can be shown to share a common intermediate if the
reactions yield the same product distribution. Therefore,
if the oxidation of substrates by the photodeoxygenation
of 1 to 4 produces the same distribution of products as
A number of substrates such as toluene, benzene, sty-
rene, and 1-octene have been oxidized using O( P) pro-
duced by the photodeoxygenation of DBTO.
3
[
2,4,5]
3
These
DBTO, then 1 to 4 are considered to produce O( P) on
substrates yield multiple products upon reaction with O
photodeoxygenation. Three different common intermedi-
ate experiments were conducted to verify if selenoxides
1 to 4 produce O( P) on photodeoxygenation. Toluene,
3
3
(
P). For instance, oxidation of toluene by O( P) yields
3
benzyl alcohol, o-cresol, m-cresol, and p-cresol in a

CHINTALA ET AL.
7 of 14
benzene, and 1-octene were used as substrates in these
common intermediate experiments for 1 to 3. Since com-
pound 4 is not soluble in toluene or benzene, oxidation of
toluene or benzene common intermediate experiments
were not conducted for 4. However, the 1-octene com-
mon intermediate experiment of 4 was performed in eth-
anol as the solubility of 4 in acetonitrile was very low.
obtained was negligible and the ratio of CH :ring
3
obtained was 1:17 (Table 2, entry 2). It should also be
noted that the head space for all of the argon sparged
samples was the same, which has been shown to effect
[
41]
the ratio of oxidized products.
Unlike DBTO, the CH :ring ratio obtained for the
3
oxidation of toluene by photodeoxygenation of DBSeO
was 1:26 (Table 2, entry 3) when degassed by argon
sparging. This was due to the higher quantum yield of
photodeoxygenation of DBSeO compared with DBTO,
which results in a difference in the photolysis time of
DBTO and DBSeO. When 14 Luzchem UVA bulbs
(LZC-UVA) were used for irradiation, the photolysis
time for DBTO was 4 h to yield approximately 0.5 mM
DBT whereas DBSeO was photolyzed for only 10 min
to yield approximately 0.5 mM DBSe. Thus, the longer
3.5 | Common intermediate experiments
The oxidation of toluene has been used as a common
intermediate experiment to verify if the oxidant that
formed during the photodeoxygenation of sulfoxides and
3
[6,27,28,41]
selenoxides is the same and likely O( P).
How-
ever, the results must be carefully analyzed since the
ratio of the oxidized products is sensitive to the amount
irradiation time for DBTO affected the CH :ring ratio
3
[27,28,41]
of dissolved molecular oxygen.
This sensitivity
for argon-sparged samples due to the background
oxidation of toluene by the residual dissolved
molecular oxygen. The product ratio obtained for
DBSeO when degassed using argon sparging was
similar to the product ratio obtained for DBTO when
freeze-pump-thaw technique was used to remove
oxygen. Therefore, as the quantum yields of photo-
deoxygenation of selenoxides 1 to 3 are closer to
DBSeO, argon sparging was used to degas the
photolysis samples. The ratio obtained for DBSeO was
considered as the reference ratio.
arises from the ability of dissolved molecular oxygen to
oxidize toluene upon UVA irradiation. Irradiation of tol-
uene for 4 h, which was degassed using argon sparging,
with UVA light yielded mainly benzaldehyde and benzyl
alcohol and some cresols in a 10:1 CH :ring ratio of oxi-
3
dation products. As shown in Figure 4, when toluene was
degassed by argon sparging, the oxidation of toluene by
the photodeoxygenation of DBTO yielded 1:3 CH :ring
3
[
29]
ratio (Table 2, entry 1) upon 4 h of UVA irradiation.
However, when the freeze-pump-thaw technique, which
is a superior technique for removing dissolved oxygen,
was used to degas toluene, the amount of benzaldehyde
Oxidation of toluene by the photodeoxygenation of
DBTO, DBSeO, and 1 to 3 produced more cresols than
3
FIGURE 4 Oxidation of toluene by O( P)
TABLE 2 Product distribution and yields of toluene oxidation by photolysis of DBTO, DBSeO, and 1 to 3
a
Percentage product yield (%)
Total oxidation
product yield (%)
b
c
Entry
Compound
Benzaldehyde
5 ± 3
Benzyl alcohol
6 ± 3
o-cresol
17.6 ± 0.9
21 ± 1
m/p-cresol
13 ± 1
3
CH :ring
d
1
2
3
4
5
6
DBTO
42 ± 4
1: 3
1: 17
1: 26
1: 27
1: 25
1: 11
e
DBTO
0.5 ± 0.7
1.2 ± 0.2
0.2 ± 0.2
0.5 ± 0.9
0.3 ± 0.4
1.3 ± 0.7
0.0 ± 0.2
0.4 ± 0.1
0.2 ± 0.4
0.5 ± 0.5
10 ± 3
33 ± 5
DBSeO
18 ± 3
13 ± 3
32 ± 7
1
2
3
9 ± 3
7 ± 1
17 ± 4
11.6 ± 0.5
6 ± 3
6.1 ± 0.1
3 ± 2
18.4 ± 0.9
10 ± 2
Abbreviations: DBSeO, dibenzoselenophene Se-oxide; DBTO, dibenzothiophene S-oxide.
a
Percentage yields of toluene oxidation products are calculated with respective to formation of selenide/DBT and are within 95% CI.
Calculated as one peak.
b
c
Ratio of sum of yields of PhCHO and benzyl alcohol to combined yields of cresols.
d
[41]
From Petroff et al.
e
Photolysis samples were degassed using freeze pump thaw technique.

8
of 14
CHINTALA ET AL.
benzaldehyde and benzyl alcohol after photolysis. No
other toluene oxidation products for DBTO, DBSeO, and
Oxidation of benzene as a common intermediate
experiment was conducted for DBTO, DBSeO, and 1 to 3.
The photolysis time for 1, 2, and DBSeO was 3 min and
for DBTO and 3 were 60 min and 5 min, respectively.
The product distribution and total product yields of
DBTO, DBSeO, and 1 to 3 are listed in Table 3. Photolysis
of DBTO, DBSeO, and 1 to 3 primarily yielded phenol
with biphenyl as the minor product. No other benzene
oxidation products were observed in GC-FID analysis
after photolysis. Compounds 1 to 3 had similar product
distribution as obtained for DBSeO and DBTO, but the
total product yields obtained were lower. For compound
1, the total product yield obtained, 18.4 ± 0.1%, is lower
than the total product yield obtained for DBSeO
(32 ± 6%) and DBTO (33 ± 2%). Similar to 1, the total
product yield of 2, 17.9 ± 0.9%, was lower compared with
DBTO and DBSeO. Compound 3 had the lowest total
product yield of 7.7 ± 0.2% compared with all the other
1
to 3 were observed in GC-FID analysis after photolysis.
The product yields of DBSeO and 1 to 3 were calculated
relative to the formation of selenide. For DBTO, the
product yields were calculated relative to the formation
of DBT. HPLC analysis was used to determine the
increase in the selenide and DBT concentration. The
photolysis time for 1 to 3 and DBSeO was approximately
1
0 min, while for DBTO, it was 4 h. The total product
yields obtained for DBTO when toluene was degassed by
argon sparging and freeze pump thaw were 42 ± 4% and
3
3 ± 5%, respectively. The total product yield obtained
for DBSeO was 32 ± 7%, which is within the limits of the
experimental error of the yields obtained for DBTO.
Compound 1 had a similar CH :ring oxidation ratio of
3
1
:27 compared with DBSeO. The total product yield
obtained for 1 was 17 ± 4 %, which is lower than the total
product yield obtained for DBSeO. Similar to 1, com-
entries in Table 3. The similar product ratio implies that
3
pound 2 had 1: 25 CH :ring oxidation, which is similar to
1
to
3
produce O( P) upon photodeoxygenation.
3
DBSeO. However, the total product yield obtained for 2,
However, as the total product yields of 1 to 3 are lower
than the total product yields of DBSeO and DBTO, 1 to
3 might also undergo photodeoxygenation through an
alternate pathway which does not result in the oxidation
of benzene.
1
8.4 ± 0.9%, is also lower than that of DBSeO. For
selenoxide 3, the CH :ring oxidation ratio obtained was
3
1
:11, which is slightly lower than DBSeO in terms of
amount of ring oxidation. However, the CH :ring
3
oxidation ratio can be considered as nearly 0:1 because
the errors obtained for the yields of benzaldehyde and
benzyl alcohol are high. Although these results suggest
that compounds 1 to 3 produce the same oxidant as
DBTO and DBSeO, namely O( P), the oxygen sensitivity
makes the oxidation of toluene a less robust approach to
make this conclusion.
The oxidation of 1-octene common intermediate
experiment was also performed to provide further
support that photodeoxygenation of 1 to 3 produced O
3
3
( P). The reaction of 1-octene and O( P) gives
1,2-epoxyoctane and 1-octanal as products, as shown in
Figure 6. Similar to the oxidation of benzene common
intermediate experiment, the product distribution of this
common intermediate experiment was not oxygen
sensitive as no 1-octene oxidation products were obtained
by the irradiationof 1-octene (500 mM) with UVA light in
acetonitrile when the solution was not degassed.
3
As the oxidation of toluene common intermediate
experiment is oxygen-sensitive, other common intermedi-
ate experiments were explored. Oxidation of benzene is
another common intermediate experiment that has been
3
used to support if O( P) is the intermediate of photo-
Compounds 1 to 3 along with DBTO and DBSeO were
used to oxidize 1-octene in acetonitrile. The photolysis
time for DBTO was approximately 4 h and for DBSeO
and 1 to 3 was approximately 5 min. The results of the
1-octene oxidation test are listed in Table 4. The product
distributions obtained for DBTO, DBSeO, and 1 to 3 were
alike. The ratios of 1-octanal to 1,2-epoxyoctane obtained
for DBTO, DBSeO, and 1 to 3 were around 1:1.3. The
total product yield obtained for DBTO was 59 ± 6%
which is significantly higher than the total product yield
of DBSeO which was 25.4 ± 0.7%. Compound 1 had a
total product yield of 13.0 ± 0.3%, which is lower than
both DBTO (59 ± 6%) and DBSeO (25.4 ± 0.7%). The total
product yields of 2 and 3 are 8 ± 1% and 11 ± 3%,
respectively. Again, the similar product ratio suggests
[
5,6,14]
deoxygenation of sulfoxides and selenoxides.
3
Oxidation of benzene by O( P) predominantly produces
phenol along with some biphenyl, as shown in Figure 5.
The product distribution of this test is not oxygen-
sensitive since irradiation of benzene with UVA did not
yield any benzene oxidation products even when the
solution was not degassed. Hence, the product
distribution of the oxidation of benzene should not be
affected due to a difference in irradiation times.
3
that compounds 1 to 3 generate O( P) upon irradiation
3
FIGURE 5 Oxidation of benzene by O( P)
like DBTO. However, the lower yields for 1 to 3, which

CHINTALA ET AL.
9 of 14
TABLE 3 Product distribution and yields of benzene oxidation by photolysis of DBTO, DBSeO, and 1 to 3
a
Percentage product yields(%)
Entry
Compound
Phenol
32 ± 2
Biphenyl
1.0 ± 0.1
Total oxidation product yield (%)
1
2
3
4
5
DBTO
33 ± 2
32 ± 6
DBSeO
31 ± 6
0.8 ± 0.5
1
2
3
17.40 ± 0.03
17.5 ± 0.7
7.4 ± 0.2
1.0 ± 0.1
18.4 ± 0.1
17.9 ± 0.9
7.7 ± 0.2
0.40 ± 0.01
0.30 ± 0.01
Abbreviations: DBSeO, dibenzoselenophene Se-oxide; DBTO, dibenzothiophene S-oxide.
a
Percentage yields of benzene oxidation products are calculated with respective to formation of selenide/DBT and are within 95% CI.
3
FIGURE 6 Oxidation of 1-octene by O( P)
TABLE 4 Product distribution and yields of 1-octene oxidation by photolysis of DBTO, DBSeO, and 1 to 3
a
Percentage product yield (%)
b
Entry
Compound
1-octanal
24 ± 2
1,2-epoxyoctane
35 ± 3
Total oxidation product yield (%)
1-octanal: 1,2-epoxy octane
1
2
3
4
5
DBTO
59 ± 6
25.4 ± 0.7
13.0 ± 0.3
8 ± 1
1: 1.4
1: 1.3
1: 1.2
1: 1.4
1: 1.3
DBSeO
11.0 ± 0.2
5.9 ± 0.4
3.4 ± 0.6
5 ± 1
14.4 ± 0.9
7.00 ± 0.04
4.9 ± 0.5
1
2
3
7 ± 2
11 ± 3
Abbreviations: DBSeO, dibenzoselenophene Se-oxide; DBTO, dibenzothiophene S-oxide.
a
Percentage yields of 1-octene oxidation products are calculated with respective to formation of selenide/DBT and are within 95% CI.
Ratio of yield of 1-octanal to yield of 1,2-epoxyoctane.
b
were also observed in the tests with toluene and benzene,
suggest other deoxygenation mechanisms that do not
produce O( P) could be operative.
The total product yields obtained for DBTO and
DBSeO in the oxidation of toluene and oxidation of ben-
zene common intermediate experiments were similar.
However, the total product yield obtained for DBSeO for
the 1-octene oxidation common intermediate experiment
was much lower than the total product yield obtained for
DBTO. To examine if solvent effects influenced these oxi-
dations, DBTO and DBSeO were photolyzed individually
with 1-octene in dichloromethane. No significant change
in the total product yields was observed when the solvent
was changed to dichloromethane from acetonitrile for
both DBTO and DBSeO. The total product yields of oxi-
dation of 1-octene by photodeoxygenation of DBTO and
DBSeO in dichloromethane were 70 ± 8% and 29 ± 3%.
Therefore, the lower total product yield for DBSeO was
not due to different solvent effects for DBSeO and DBTO.
A similar observation was reported previously when a
mixture of benzene and cyclohexane, in the ratio of 3:1
3
As previously mentioned, common intermediate
experiments for 4 were not possible due to low
solubility in acetonitrile, which is required to obtain
significant oxidation of toluene or benzene. However,
the oxidation of 1-octene as a common intermediate
experiment could be performed in ethanol. Since
3
ethanol is more reactive with O( P) than acetonitrile, a
lower yield of 1-octanol and 1,2-epoxyoctane was
[1,42]
expected.
with 500 mM 1-octene, the total product yield of
-octanal and 1,2-epoxyoctane dropped to 4%.
When DBSeO was irradiated in ethanol
1
Irradiation of 4 in ethanol with 500 mM 1-octene with
UVA light resulted in 4Se; however, GC-FID analysis
showed neither a 1-octanal nor a 1,2-epoxyoctane peak.
Given that the detection limit of 1-octanal and
1
,2-epoxyoctane was 3.0 μM, 4 produces less than half
(v/v), was oxidized in dichloromethane individually by
3
[27]
the O( P) of that of DBSeO or possibly none at all. The
photolysis of DBTO and DBSeO.
Both DBTO and
concentrations of DBSeO and 4 in ethanol used for
DBSeO yielded product ratios which were approximately
1:3 phenol:cyclohexanol. However, the total product yield
1
-octene oxidation were both 1.1 mM.

10 of 14
CHINTALA ET AL.
obtained for DBSeO, 6.2 ± 0.8 %, was significantly lower
compared with the total product yield, 42 ± 5.1%,
Since the product ratios for all the three common
intermediate experiments of selenoxides 1 to 3 were
similar to DBTO, the photodeoxygenation of selenoxides
1 to 3, DBSeO, and DBTO likely have O( P) as a common
intermediate. However, the total product yields of 1 to
[27]
obtained for DBTO.
The reason for the lower product
3
yields of 1-octene oxidation by DBSeO compared with
DBTO was not investigated.
3
were lower than to that of DBTO and DBSeO. One
explanation for the lower yields observed for 1 to 3 is that
3.6 | Mechanistic studies
they deoxygenate through other additional pathways that
do not produce O( P). To test this hypothesis, mechanis-
3
Various mechanisms have been proposed to explain the
photodeoxygenation of aryl sulfoxides.
The first proposed mechanism postulated that the photo-
tic studies for 1 to 3 were conducted. Selenoxides 1 to
3 were individually dissolved in EPA glass (ether:pen-
tane:ethyl alcohol = 5:5:2) at low concentration at 77 K
and photolyzed by UVA irradiation. HPLC analysis after
the photolysis showed increase in the corresponding sele-
[5,7,14,15,27,43–45]
deoxygenation of aryl sulfoxides proceeds by
a
[15]
bimolecular process.
However, common intermediate
experiments, results of photolysis at low temperature
nide concentration. This indicatesthat a plausible
18
(
77 K), and O-labeling studies refuted the bimolecular
unimolecular mechanism for photodeoxygenation of 1 to
[5,14]
3
mechanism.
Currently, the accepted mechanism of
3 is operable, which is the posited mechanism for O( P)
photodeoxygenation by direct irradiation of aryl
release. However, this result does not rule out an addi-
tional bimolecular photoreduction mechanism account-
ing for some of the photodeoxygenation in solution.
Photodeoxygenation by a bimolecular mechanism
could potentially occur by electron transfer, energy
transfer, or the formation of a bimolecular exciplex
3
sulfoxides to yield O( P) is unimolecular scission of the
[5,27]
3
S O bond.
In addition to O( P) formation, photo-
deoxygenation of aryl sulfoxides also occurs through
other pathways such as photoinduced electron transfer
[27,43,44]
and triplet sensitization.
Specifically for DBTO,
deoxygenation through the T triplet state reached by
between two selenoxides that undergoes deoxygenation
1
3
[27]
[43,46]
photosensitization did not yield O( P).
Similarly, pho-
to release a “dioxygen” oxidant.
The potential for
toinduced deoxygenation of DBTO derivatives at high pH
was the result of electron transfer from hydroxide ion to
the sulfoxide, which results in deoxygenation to yield the
a bimolecular exciplex was tested for selenoxide 1.
Direct irradiation of selenoxide 1 dissolved in acetoni-
trile with 390 ± 3 nm light in the presence of DBSeO
yielded 1Se and DBSe. The UV-Vis cut-off wavelength
of DBSeO is 352 nm. Thus, the observed deoxygenation
of both DBSeO and 1 in these conditions implied
either a bimolecular exciplex or energy transfer from
excited 1 to DBSeO, which both would be expected to
result in 1Se and DBSe. To differentiate them,
selenoxide 1 was irradiated with 390 ± 3 nm light at
variable concentrations of DBSeO and 500 mM of
1-octene. Acetonitrile was used as the solvent for these
experiments, and the results of these experiments are
shown in the Table 5.
3
[44]
corresponding sulfides and no O( P).
Fewer mechanis-
tic studies have been done to explain the process of
photodeoxygenation of aryl selenoxides. The limited stud-
ies that have been done show photodeoxygenation of aryl
selenoxides occurs by unimolecular and bimolecular
pathways. Photodeoxygenation of diphenyl and dibenzyl
selenoxides by irradiation with
a
high-pressure
mercury lamp yielded their corresponding selenides
[46]
through a bimolecular mechanism.
However, photo-
deoxygenation of DBSeO to DBSe occurs by
unimolecular mechanism producing O( P).
a
3
[6,27]
TABLE 5 Product distribution and yields of 1-octene oxidation by direct irradiation of 1 in the presence of DBSeO
Initial concentration (mM)
a
b
Entry
Selenoxide 1
DBSeO
0.0
Total oxidation product yield (%)
1-octanal:1,2-epoxy octane
1
2
3
4
5
1.7
1.7
1.7
1.7
1.7
15 ± 2
13 ± 2
1:1.5
1:1.4
1:1.4
1:1.4
1:1.4
0.4
0.8
14 ± 2
1.6
11.1 ± 0.1
12 ± 2
3.2
Abbreviations: DBSeO, dibenzoselenophene Se-oxide.
a
Percentage yields of 1-octene oxidation products are calculated with respective to formation of 1Se and DBSe and are within 95% CI.
Ratio of yields of 1-octanal to yield of 1,2-epoxyoctane.
b

CHINTALA ET AL.
11 of 14
The product ratio 1-octanal:1,2-epoxyoctane was
the common intermediate experiments of 1 to 3 would be
lower if the selenoxides 1 to 3 deoxygenated through both
approximately 1:1.4 for all the experiments. The total
product yields for all the experiments were within the
limits of the experimental error. If a bimolecular complex
was the reason for the lower yields of oxidized product,
the total product yields should decrease with increase in
the concentration of DBSeO. Therefore, these results
indicated photodeoxygenation of DBSeO occurred by
energy transfer from the excited state of 1 to DBSeO
3
T and T but only produced O( P) from the T state as
1
2
2
with DBTO. Photosensitization of selenoxides 1 to 3 to
the T state could be used to test this hypothesis. The
1
energies of T1 triplet states of 1 to 3 were obtained
computationally using a HSEH1PBE/6-311G(d,p) level of
[
48–50]
theory.
The T triplet states energies of 1 to 3 are
1
shown in Table 6.
rather than through
dissociates to deoxygenated products.
Direct irradiation of 1 in methanol with 390 ± 3 nm
in the presence of diphenyl selenoxide was performed to
provide more evidence that 1 does not undergo deoxygen-
ation through a bimolecular exciplex. As selenoxide
a
bimolecular exciplex that
Acridine orange was chosen as the sensitizer because
its triplet energy of 50.2 kcal/mol was close to the
[
51]
calculated triplet energies of 1 to 3.
Hence, the T1
triplet state of acridine orange has enough energy to
promote 1 to 3 to their corresponding T triplet states.
1
However, acridine orange could also act as an electron
donor in its excited state as its halfwave oxidation
potential is closer to aniline, which is a good electron
1
and diphenyl selenoxide had higher solubility in metha-
nol compared with acetonitrile, methanol was used for
this reaction. This reaction did not yield any diphenyl sel-
enide after the reaction. Similarly, direct irradiation of
[
52,53]
donor.
Therefore, both mechanisms have to be
considered while using acridine orange to sensitize 1 to 3.
Selenoxides 1 to 3 dissolved in acetonitrile were
excited by sensitization using acridine orange in the pres-
ence of 1-octene, as shown in Figure 7. HPLC analysis
after the experiment showed that triplet sensitization
resulted in photodeoxygenation of 1 to 1Se. However,
GC-FID analysis showed no formation of 1-octene
oxidation products. Similarly, sensitization of selenoxide
3 yielded 3Se, but no 1-octene oxidation products were
obtained. Interestingly, sensitization of 2 produced only
2Se and no 2X, which was the other product obtained
when 2 was directly irradiated with UVA light. GC-FID
analysis of this reaction showed that 1-octene was
oxidized to 1-octanal and 1-octanol in low yields of 6%
and 5%, respectively. However, as 1,2-epoxyoctane was
2
and 3 individually in methanol in the presence of
diphenyl selenoxide did not yield any diphenyl selenide
for either reaction. The wavelengths used for irradiation
of 2 and 3 were 350 ± 3 nm and 390 ± 3 nm, respectively.
As a bimolecular exciplex was ruled out, another pos-
sible mechanism that was investigated was electron
transfer. As the selenides 1Se to 3Se are produced during
the photodeoxygenation of 1 to 3, photoinduced electron
transfer from the selenide to the selenoxide could result
3
[43]
in deoxygenation without the release of O( P).
hypothesis was tested by obtaining the total product
yields of 1-octene oxidation by photodeoxygenation of
This
2
at different reaction time points. The total product
yields of 1-octene oxidation at all the reaction time points
were in the range of 8 ± 4%, which is similar to the total
product yield reported in Table 4. In another experiment,
3
not obtained, it can be concluded that O( P) was not pro-
duced during photosensitization of 2. In another experi-
ment, sensitization by acridine orange was carried out in
benzene; however, no oxidation products were observed.
The photosensitization of 1 to 3 by acridine orange
2
Se was added to the solution containing 2, 1-octene, and
acetonitrile. The concentrations of 2 and 2Se were both
mM. This solution was irradiated, and the total yield of
2
the 1-octene oxidation products was obtained. The
obtained total oxidation product yield was in the same
range as reported in Table 4. These results indicate no
electron transfer from 2Se to 2 during the photolysis
process. Similar results were expected for 1 and 3.
could have occurred by energy transfer from the T triplet
1
state of acridine orange to T triplet state of 1 to 3 or by
1
electron transfer from excited state of acridine orange to
the ground state of 1 to 3 or by both mechanisms. If the
deoxygenation of 1 to 3 occurred through energy transfer,
The possibility of a unimolecular mechanism that
does not produce O( P), which would result in lower total
it suggests that T triplet state of 1 to 3 did not produce
O( P). However, if the deoxygenation occurred by
1
3
3
product yields, was investigated. Photodeoxygenation of
3
DBTO to DBT and O( P) occurs from the T triplet state
of DBTO.
2
TABLE 6 Triplet energies of selenoxides 1 to 3
[27,47]
However, the T state of DBTO accessed
1
by triplet sensitization was shown to cause photo-
deoxygenation to produce DBT, but this process does not
Entry
Selenoxide
1
T energy (kcal./mol.)
1
2
3
1
2
3
46.8
39.8
49.2
3
[27]
yield O( P).
In contrast, photodeoxygenation of
DBSeO occurs through both T and T triplet states to
1
2
3
[27,47]
produce DBSe and O( P).
The total product yields of

12 of 14
CHINTALA ET AL.
FIGURE 7 Oxidation of 1-octene by
sensitized photolysis of 1 to 3
electron transfer, it would lead to the reduction of 1 to
to their corresponding selenide and nothing can be con-
All the above mechanistic studies suggest that photo-
deoxygenation of 1 to 3 is a unimolecular process and not
bimolecular. However, the efforts to identify a photoin-
duced deoxygenation mechanism that would account for
the lower total oxidation product yields observed in the
common intermediate experiments were not successful.
3
cluded about the deoxygenation of 1 to 3 in their T
1
[43,44]
triplet state.
To determine if the halfwave oxidation
potential of acridine orange made electron transfer
feasible, perylene, which has much lower triplet state
energy but similar halfwave oxidation potential, was used
as the photosensitizer to induce electron transfer. The
triplet-state energy and halfwave oxidation potential of
perylene are 36.1 kcal/mol. and 0.85 V versus saturated
calomel electrode (SCE) (Table 7), respectively.
Selenoxide 1 was chosen for this experiment, as the
3.7 | Photochemistry of 1 and 3 with
visible light irradiation
The primary goal of this work was to prepare photo-
3
3
calculated T triplet state energy of 1 was higher than
activatable O( P)-precursors that generate O( P) using
visible light irradiation. Therefore, compounds which
absorb in visible light, 1 and 3, were tested with a com-
mon intermediate experiment. 1-octene was used as the
substrate, and acetonitrile was used as the solvent. Bulbs
centered at 420 nm (Luzchem LZC-420 nm, 14 bulbs)
were used for irradiation. The use of glass or quartz test
tube had no effect on the observed products or yields.
Selenoxides 1 and 3 were photolyzed for 1 and 4 h,
respectively. The product yields of 1-octene oxidation by
the irradiation of 1 at 420-nm light are shown in
Figure 8. Upon irradiation, 1 yielded 1,2-epoxyoctane and
1-octanal upon irradiation in a ratio 1:1.2. The total
product yield obtained was 13 ± 2%, which was similar to
the total product yield of 1-octene oxidation obtained by
UVA irradiation of 1. The product ratio is similar to the
product ratio of DBSeO listed in Table 5. The product dis-
tribution and total product yield of 1 are similar to that of
the 1-octene oxidation common intermediate experiment
performed by using bulbs centered at 350 nm. The impli-
cation of these results is that the photodeoxygenation of
1
that of perylene and 1 had a UV-Vis cutoff wavelength
lower than that of perylene. Therefore, only the electron
transfer mechanism is possible in this case. Perylene
(1.3 mM) was excited using 435 ± 3 nm in the presence
of selenoxide 1 (3.8 mM), 1-octene (500 mM), and
dodecane (0.125 mM) in acetonitrile. GC-FID and HPLC
analyses showed formation of 1Se (0.23 mM) but no
1
0
-octene oxidation products. These results imply that
.85 V versus SCE halfwave oxidation potential is
sufficient for an electron transfer mechanism. However,
as the calculated T triplet-state energy of acridine orange
1
is higher than that of 1 to 3, an energy transfer
mechanism cannot be ruled out. Additional studies to
selectively perform energy transfer using a photosensi-
tizer to selenoxides 1 to 3 were not conducted due to
limitations in readily available photosensitizers with
properties that would facilitate only energy transfer and
not electron transfer.
Therefore, deoxygenation of 1 to 3 by photosensitiza-
tion using acridine orange could have occurred by an
energy transfer mechanism or electron transfer
mechanism or by both these mechanisms. Hence, it is
3
1 produces O( P) upon irradiation with visible light.
Irradiation of 3 with visible light resulted in the
photodeoxygenation of 3. However, unlike 1, the
oxidation of 1-octene common intermediate test of 3 did
not yield any detectable amounts of 1-octanal or
inconclusive whether the T energy state of 1–3 produces
1
3
O( P). Other photosensitizers with high halfwave oxida-
tion potential could not be used for these experiments, as
they had lower UV-Vis cutoff wavelengths than 1 to 3.
TABLE 7 Halfwave oxidation potentials and triplet state
energies of acridine orange and perylene
ox
E
1/2 /V vs. SCE in
1
T energy
Photosensitizer acetonitrile
(kcal./mol.)
[
53]
[51]
Acridine orange
Perylene
0.82
0.85
50.2
[54]
[55]
36.1
FIGURE 8 Oxidation of 1-octene by 1 using bulbs centered at
Abbreviation: SCE, standard calomel electrode.
420 nm

CHINTALA ET AL.
13 of 14
TABLE 8 Quantum yields of photodeoxygenation of 1 and 3 at
ORCID
4
00 nm
John C. Throgmorton https://orcid.org/0000-0002-4403-
4363
Ryan D. McCulla https://orcid.org/0000-0003-3381-
a
Entry
Compound
Quantum yield Φ+selenide
0.13 ± 0.03
1
2
1
3
8880
0.37 ± 0.03
a
Quantum yields reported are within 95% confidence intervals and
calculated based on the increase in selenide concentration. 400
3 nm wavelength light was used for photolysis and ethanol was
REFERENCES
[
[
1] G. Bucher, J. C. Scaiano, J. Phys. Chem. 1994, 98, 12411.
2] S. M. Omlid, M. Zhang, A. Isor, R. D. McCulla, J. Org. Chem.
±
used as the solvent.
2017, 82, 13333.
[3] M. Zhang, G. E. Ravilious, L. M. Hicks, J. M. Jez,
1
,2-epoxyoctane. This indicates that the photo-
R. D. McCulla, J. Am. Chem. Soc. 2012, 134, 16979.
deoxygenation of 3 induced by visible light irradiation
produces considerably less or no O( P) compared
with irradiation with UVA light. The reason for this
wavelength dependence was not investigated.
[4] K. B. Thomas, A. Greer, J. Org. Chem. 2003, 68, 1886.
3
[
[
[
5] D. D. Gregory, Z. Wan, W. S. Jenks, J. Am. Chem. Soc. 1997,
19, 94.
6] R. D. McCulla, W. S. Jenks, J. Am. Chem. Soc. 2004, 126,
6058.
1
1
7] S. M. Omlid, S. A. Dergunov, A. Isor, K. L. Sulkowski,
J. T. Petroff, E. Pinkhassik, R. D. McCulla, Chem. Commun.
3
.8 | Determination of quantum yield of
2
019, 55, 1706.
[8] S. Chapman, Philos. Mag. J. Sci. 1930, 10, 369.
9] J. T. Herron, R. E. Huie, J. Phys. Chem. Ref. Data Monogr.
973, 2, 467.
10] R. J. Cvetanovic, D. L. Singleton, R. S. Irwin, J. Am. Chem. Soc.
981, 103, 3530.
11] R. J. Cvetanovi ꢀc , D. F. Ring, L. C. Doyle, J. Chem. Phys. 1971,
5, 3056.
photodeoxygenation at 400 nm
[
1
The UV-Vis cutoff wavelengths (ε < 50) for 1 and 3 are
[
[
[
4
00 nm and 433 nm. The quantum yields of photo-
1
deoxygenation of 1 and 3 are obtained in ethanol at
wavelength range 400 ± 3 nm and are listed in Table 8.
Saturated solutions of 1 and 3 in ethanol had optical
densities greater than 2. K[Cr (NH ) (NCS) ] was used as
7
12] R. E. Huie, J. T. Herron, D. D. Davis, Int. J. Chem. Kinet. 1972,
4, 521.
3
2
4
[39]
the actinometer.
deoxygenation of 1 and 3 were 0.13 ± 0.03 and
.37 ± 0.03, respectively.
The quantum yields of photo-
[13] H. Sakurai, K. Akimoto, T. Susumu, S. Takamuku, Chem. Lett.
975, 4, 469.
1
[
[
[
14] E. Lucien, A. Greer, J. Org. Chem. 2001, 66, 4576.
15] G. M. Gurria, G. H. Posner, J. Org. Chem. 1973, 38, 2419.
16] U. K. Kläning, K. Sehested, T. Wolff, J. Chem. Soc. Faraday
Trans. 1 Phys. Chem. Condens. Phases 1984, 80, 2969.
17] O. R. Wauchope, S. Shakya, N. Sawwan, J. F. Liebman,
A. Greer, J. Sulfur Chem. 2007, 28, 11.
[18] J. Korang, I. Emahi, W. R. Grither, S. M. Baumann,
D. A. Baum, R. D. McCulla, RSC Adv. 2013, 3, 12390.
19] M. T. Bourdillon, B. A. Ford, A. T. Knulty, C. N. Gray,
0
4
| CONCLUSION
[
3
Selenoxides 1 to 3 have shown to generate O( P) in
condensed phase when irradiated by UV light.
Selenoxides 1to 4 have higher UV-Vis absorption
wavelength cutoffs than DBTO and DBSeO, with 1, 3,
and 4 having the cutoff wavelength equal to or above
[
M. Zhang, D. A. Ford, R. D. McCulla, Photochem. Photobiol.
2014, 90, 386.
[
[
20] R. Brem, P. Karran, Photochem. Photobiol. 2012, 88, 5.
21] M. C. Cardoso, R. Greinert, S. Henning, A. Rapp, B. Volkmer,
K. O. Greulich, E. W. Breitbart, Nucleic Acids Res. 2012, 40,
4
00 nm. Photodeoxygenation of compound 4 to
corresponding selenide 4Se had a lower quantum yield
compared with 1 to 3. Although photodeoxygenation of
10263.
3
occurs upon visible light irradiation, it did not produce
[22] P. Karran, R. Brem, DNA Repair (Amst). 2016, 44, 178.
[23] P. Agostinis, K. Berg, K. A. Cengel, T. H. Foster, A. W. Girotti,
S. O. Gollnick, S. M. Hahn, M. R. Hamblin, A. Juzeniene,
D. Kessel, M. Korbelik, CA Cancer J. Clin. 2011, 61, 250.
3
O( P). Most importantly, the photodeoxygenation of
selenoxide 1 induced by 420-nm light generated O( P).
The quantum yields of photodeoxygenation of 1 to 3 are
higher than all the O( P)-precursors reported till date.
3
3
[24] J. Zhao, W. Wu, J. Sun, S. Guo, Chem. Soc. Rev. 2013, 42, 5323.
[25] S. M. Omlid, A. Isor, K. L. Sulkowski, S. M. Chintala,
J. T. Petroff, R. D. McCulla, Synthesis 2018, 50, 2359.
ACKNOWLEDGMENTS
[26] J. T. Petroff, R. D. McCulla, Tetrahedron Lett. 2016, 57, 4723.
This work was supported by the National Science
Foundation under CHE-1900417.
[27] E. M. Rockafellow, R. D. McCulla, W. S. Jenks, J. Photochem.
Photobiol. A Chem. 2008, 198, 45.

14 of 14
CHINTALA ET AL.
[
28] X. Zheng, S. M. Baumann, S. M. Chintala, K. D. Galloway,
J. B. Slaughter, R. D. Mcculla, Photochem. Photobiol. Sci. An
Int. J. 2016, 15, 791.
[49] D. Avcı, S. Bahçeli, Ö. Tamer, Y. Atalay, Can. J. Chem. 2015,
93, 1147.
[50] M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone,
B. Mennucci, G. A. Petersson, H. Nakatsuji, M. Caricato, X. Li,
H. P. Hratchian, A. F. Izmaylov, J. Bloino, G. Zheng,
J. L. Sonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda,
J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao,
H. Nakai, T. Vreven, J. A. Montgomery Jr., J. E. Peralta,
F. Ogliaro, M. Bearpark, J. J. Heyd, E. Brothers, K. N. Kudin,
V. N. Staroverov, R. Kobayashi, J. Normand, K. Raghavachari,
A. Rendell, J. C. Burant, S. S. Iyengar, J. Tomasi, M. Cossi,
N. Rega, J. M. Millam, M. Klene, J. E. Knox, J. B. Cross,
V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts,
R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi,
C. Pomelli, J. W. Ochterski, R. L. Martin, K. Morokuma,
V. G. Zakrzewski, G. A. Voth, P. Salvador, J. J. Dannenberg,
S. Dapprich, A. D. Daniels, Ö. Farkas, J. B. Foresman,
J. V. Ortiz, J. Cioslowski, D. J. Fox, Gaussian 09, Revis. E.01,
Gaussian, Inc, Wallingford CT 2009.
[
[
[
[
29] S. M. Chintala, J. T. Petroff II, A. Barnes, R. D. McCulla,
J. Sulfur Chem. 2019, 40, 503.
30] E. Paegle, S. Belyakov, P. Arsenyan, European J. Org. Chem.
2
014, 2014, 3831.
31] G. Kirsch, S. Deprets, Zeitschrift für Naturforsch. B 2006,
1, 427.
32] W. Jiang, H. Qian, Y. Li, Z. Wang, J. Org. Chem. 2008, 73,
369.
6
7
[
[
33] V. Gupta, K. S. Carroll, Chem. Sci. 2016, 7, 400.
34] J. C. Throgmorton, S. M. Chintala, R. D. McCulla,
J. Heterocyclic Chem. 2017, 54, 3682.
[
[
[
35] Y. Tominaga, M. L. Lee, R. N. Castle, J. Heterocyclic Chem.
1
981, 18, 967.
36] M. L. Tedjamulia, Y. Tominaga, R. N. Castle, M. L. Lee,
J. Heterocyclic Chem. 1983, 20, 1143.
37] M. Iyoda, S. M. Humayun Kabir, Y. Kuwatani, H. Matsuyama,
M. Hasegawa, M. Yoshida, J. Chem. Soc. Perkin Trans. 2002,
1
, 159.
38] N. J. Bunce, J. Lamarre, S. P. Vaish, Photochem. Photobiol.
984, 39, 531.
[51] R. W. Chambers, D. R. Kearns, Photochem. Photobiol. 1969,
10, 215.
[52] S. L. Murov, I. Carmichael, G. L. Hug, Handbook of Photo-
chemistry, 1993.
[53] F. Li, M. Pfeiffer, A. Werner, K. Harada, K. Leo, N. Hayashi,
K. Seki, X. Liu, X.-D. Dang, J. Appl. Phys. 2006, 100, 023716.
[54] E. S. Pysh, N. C. Yang, J. Am. Chem. Soc. 1963, 85, 2124.
[55] C. A. Parker, Photoluminescence of solutions: With applications
to photochemistry and analytical chemistry, Elsevier,
Amsterdam, London, N.Y 1968.
[
1
[
[
39] E. E. Wegner, A. W. Adamson, Quantum 2011, 22, 394.
40] J. Takeya, T. Okamoto, T. Nakanishi, Chalcogen-
Containing Organic Compound and use Thereof, US
9
537110 B2, 2017.
[
[
[
[
[
[
[
[
41] J. T. Petroff, S. M. Omlid, S. M. Chintala, R. D. R. D. McCulla,
J. Photochem. Photobiol. A Chem. 2018, 358, 130.
42] C. W. Wu, Y. P. Lee, S. Xu, M. C. Lin, J. Phys. Chem. A 2007,
1
11, 6693.
43] J. W. Cubbage, T. A. Tetzlaff, H. Groundwater, R. D. McCulla,
M. Nag, W. S. Jenks, J. Org. Chem. 2001, 66, 8621.
44] J. Korang, W. R. Grither, R. D. McCulla, J. Am. Chem. Soc.
SUPPORTING INFORMATION
Additional supporting information may be found online
in the Supporting Information section at the end of this
article.
2
010, 132, 4466.
45] K. Kumazoe, K. Arima, S. Mataka, D. J. Walton, T. Thiemann,
J. Chem. Res. - Part S 2003, 2003, 60.
46] Y. Yamazaki, T. Tsuchiya, T. Hasegawa, Bull. Chem. Soc. Jpn.
2
003, 76, 201.
How to cite this article: Chintala SM,
47] S. A. Stoffregen, S. Y. Lee, P. Dickerson, W. S. Jenks,
Photochem. Photobiol. Sci. 2014, 13, 431.
48] D. Avcı, S. Altürk, F. Sönmez, Ö. Tamer, A. Ba s¸ o ꢁg lu,
Y. Atalay, B. Z. Kurt, N. Dege, Tetrahedron 2018, 74, 7198.
Throgmorton JC, Maness PF, McCulla RD. Visible
light-induced photodeoxygenation of polycyclic
selenophene Se-oxides. J Phys Org Chem. 2020;
e4144. https://doi.org/10.1002/poc.4144