Communication
ChemComm
oxide intermediates, were observed in any experiment. Additionally, photooxygenations. The scheme also offers a viable method
a collision event between the sulfoxide of the excited 1a and the for studying other short-lived reactive intermediates.
sulfide of 2a would be required for direct oxygen atom transfer
We greatly acknowledge financial support by the National
resulting in 2b. Thus, the probability of a productive collision event Science Foundation under CHE-1255270 and CHE-1709921.
within a pore of the nanocapsule shell is very small and cannot This work was additionally supported by the University of
explain the 8–11 mM increase in 2b.
Connecticut Research Excellence Program.
The results from the experiments described above demon-
strate that photodeoxygenation of 1a inside of the nanocapsules
generates a freely diffusing intermediate that oxidizes 2a to 2b. Conflicts of interest
3
Since the diffusion distance of O( P) in this system is predicted
to be 65 nm, a freely diffusing O( P) would be capable of
traversing the nanocapsule intact.
1
6
3
There are no conflicts to declare.
Notes and references
Because 2a is oxidized to 2b upon irradiation in the presence
of O (Fig. 4A, photocontrol), the possibility of O as the oxidant
2 2
1
2
3
D. D. Gregory, Z. Wan and W. S. Jenks, J. Am. Chem. Soc., 1997, 119,
94–102.
J. Korang, W. R. Grither and R. D. McCulla, J. Am. Chem. Soc., 2010,
should be examined. While the current experiments cannot rule
this out, the preponderance of evidence from previous studies
have led to the conclusion that the direct irradiation of DBTO and
its derivatives result in photodeoxygenation by a unimolecular
132, 4466.
H. Kautsky and H. de Bruijn, Naturwissenschaften, 1931, 19, 1043.
4 A. Greer, Acc. Chem. Res., 2006, 39, 797.
1
,2
5 M. D. Kim, S. A. Dergunov and E. Pinkhassik, Langmuir, 2015, 31, 2561.
mechanism. A biomolecular mechanism of deoxygenation
leading to O2 was inconsistent with several different experi-
ments. Photodeoxygenation was observed when DBTO was
6
M. D. Kim, S. A. Dergunov, E. Lindner and E. Pinkhassik, Anal. Chem.,
2012, 84, 2695.
7 S. A. Dergunov, B. Miksa, B. Ganus, E. Lindner and E. Pinkhassik,
1
,2
Chem. Commun., 2010, 46, 1485.
isolated in a solid matrix to prevent bimolecular collisions.
8
A. G. Richter, S. A. Dergunov, M. D. Kim, S. N. Shmakov, S. V. Pingali,
V. S. Urban, Y. Liu and E. Pinkhassik, J. Phys. Chem. Lett., 2017,
8, 3630.
Additionally, the selective irradiation of DBTO in the presence
of diphenyl sulfoxide produced no diphenyl sulfide, which
would be expected if a bimolecular exciplex was involved in
9
S. A. Dergunov, K. Kesterson, W. Li, Z. Wang and E. Pinkhassik,
Macromolecules, 2010, 43, 7785.
1
the photodeoxygenation mechanism. The possibility of two
1
0 A. Q. Maclin, M. D. Kim, S. A. Dergunov and E. Pinkhassik, Electro-
analysis, 2015, 27, 733.
3
O( P) combining to form O is unlikely due to the low steady-
2
3
11 L. T. Banner, D. C. Danila, K. Sharpe, M. Durkin, B. Clayton, B. Anderson,
state concentration of O( P) in these conditions.
A. Richter and E. Pinkhassik, Langmuir, 2008, 24, 11464.
2 C. A. McKelvey, E. Kaler, J. A. Zasadzinski, B. Coldren and H. T. Jung,
Langmuir, 2000, 16, 8285.
3 S. M. Omlid, A. Isor, K. L. Sulkowski, S. M. Chintala, J. T. Petroff and
R. D. McCulla, Synthesis, 2018, 2359.
4 P. K. Dornan, P. L. Leung and V. M. Dong, Tetrahedron, 2011,
67, 4378.
As described in the ESI,† (Table S1 and Fig. S1), common
intermediate and isolation experiments were performed and
indicated that 1a and DBTO generate an oxidant with the same
chemoselectivity and that 1a undergoes photodeoxygenation by
a unimolecular mechanism.
Applying Occam’s razor, the simplest explanation for the
oxidation of 2a by 1a through an impermeable barrier upon
irradiation of 1a is that the photodeoxygenation of 1a generates
a small freely diffusing oxidant. Since 1a undergoes deoxygenation
by a unimolecular mechanism and has the same chemoselectivity
1
1
1
1
1
1
5 D. L. Singleton and R. J. Cvetanovic, J. Phys. Chem. Ref. Data, 1988,
17, 1377.
6 S. M. Omlid, M. Zhang, A. Isor and R. D. McCulla, J. Org. Chem.,
2017, 82, 13333.
7 M. D. Kim, S. A. Dergunov, A. G. Richter, J. Durbin, S. N. Shmakov,
Y. Jia, S. Kenbeilova, Y. Orazbekuly, A. Kengpeiil and E. Lindner,
Langmuir, 2014, 30, 7061.
as DBTO, these results are consistent with the notion that the freely 18 M. D. Kim, S. A. Dergunov and E. Pinkhassik, Langmuir, 2017,
3
33, 7732.
diffusing oxidant is O( P).
1
2
9 S. N. Shmakov and E. Pinkhassik, Chem. Commun., 2013, 49, 11026.
0 S. A. Dergunov, N. Ehterami and E. Pinkhassik, Chem. – Eur. J., 2016,
22, 14137.
The employed experimental scheme answers a key mechanistic
question about the nature of the oxidant in aryl sulfoxide
Chem. Commun.
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