Triplet-sensitized deoxygenation reaction of 6-cyanophenanthridine 5-oxide in ethanol

Tokumura, Kunihiro; Matsushita, Yumi

doi:10.1016/s1010-6030(01)00387-2

Cited by 5 publications

(6 citation statements)

References 19 publications

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“…Kinetic studies 15b of atomic oxygen in solution with laser flash photolysis of pyridine N -oxide point to a mechanism in which the solvent reacts with an invisible species (atomic oxygen) to yield the observed transients. Rapid release of 3 O from the N -oxide functional group in the lowest excited singlet state (S 1 ) has also been considered for pyridine N -oxide. ,15b These studies support the formation of oxygen atom (accompanied by other intramolecular processes, however); also, a number of questions concerning these reactions still remain open.…”

Section: Discussionmentioning

confidence: 99%

“…8 There is now general agreement that the former involves the first excited singlet state and the latter probably the triplet state. 7,9 Oxygen transfer to various substrates may be an efficient intermolecular process for diazines 10 and polyazapolycyclic N-oxides. 11 Intramolecular oxygen transfer from pyridine N-oxides to bridged aromatic nuclei also has been reported.…”

Section: Introductionmentioning

confidence: 99%

“…Reported photochemical reactions fall into two groups, i.e., rearrangement and N -deoxygenation , Oxygen transfer to various substrates may be an efficient intermolecular process for diazines and polyazapolycyclic N -oxides . Intramolecular oxygen transfer from pyridine N -oxides to bridged aromatic nuclei also has been reported .…”

Section: Introductionmentioning

confidence: 99%

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Covalently Linked Acceptor−Donor Systems Based on Isoquinoline N-oxide Acceptor: Photoinduced Electron Transfer Produces Dual-Channel Luminescent Systems that Evolve Chemically to Photohydroxylation of the Aromatic Donor

2003

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Acceptor-donor compounds containing the isoquinoline N-oxide acceptor and (methoxy)(n)benzene (n = 0, 1, 2, 3) electron donors were studied. The two chromophores are connected by a CH(2) bridging unit. All acceptor-donor compounds exhibit photoinduced electron transfer in acid medium that results in the formation of a charge-transfer (CT) state. Measurements of the corresponding electronic emission spectra revealed that these bichromophoric systems exhibit a dual fluorescence that is strongly dependent on the protonation of the N-oxide function and the donor ability. The CT state responsible for the red-shifted luminescence in the studied compounds is directly connected with the initial excited state S(1). On the basis of the spectroscopic and photochemical evidence, N[bond]O scission is the dominant primary photochemical process involving the CT state, the subsequent radical coupling resulting in efficient aromatic hydroxylation. The outcome of both quenching and sensitization experiments confirms this assertion. The results strongly suggest that the ensuing photohydroxylation reaction is not a concerted process, but rather a two-step N[bond]O scission followed by C[bond]O formation, which is regioselectively guided by the electronic distribution of the resulting donor cation-radical.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Covalently Linked Acceptor−Donor Systems Based on Isoquinoline N-oxide Acceptor: Photoinduced Electron Transfer Produces Dual-Channel Luminescent Systems that Evolve Chemically to Photohydroxylation of the Aromatic Donor

2003

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“…The triplet excited state of heterocyclic N-oxides has been suggested to be responsible for photodeoxygenation, while oxygen migration and ring cleavage are attributed to the excited singlet. 15,20,21 This hypothesis is supported by an apparent correlation between the degree to which the triplet is formed in substituted pyridine N-oxides and the extent of deoxygenation. 15,20,22 Also, introduction of O 2 , a known triplet quencher, inhibits deoxygenation.…”

Section: Introductionmentioning

confidence: 92%

Generation of free oxygen atoms O(³P) in solution by photolysis of 4-benzoylpyridine N-oxide

Carraher

Bakač

2014

Phys. Chem. Chem. Phys.

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Laser flash photolysis of 4-benzoylpyridine N-oxide (BPyO) at 308 nm in aqueous solutions generates a triplet excited state (3)BPyO* that absorbs strongly in the visible, λmax 490 and 380 nm. (3)BPyO* decays with the rate law kdecay/s(-1) = (3.3 ± 0.9) × 10(4) + (1.5 ± 0.2) × 10(9) [BPyO] to generate a mixture of isomeric hydroxylated benzoylpyridines, BPy(OH), in addition to small amounts of oxygen atoms, O((3)P). Molecular oxygen quenches (3)BPyO*, kQ = 1.4 × 10(9) M(-1) s(-1), but the yields of O((3)P) increase in O2-saturated solutions to 36%. Other triplet quenchers have a similar effect, which rules out the observed (3)BPyO* as a source of O((3)P). It is concluded that O((3)P) is produced from either (1)BPyO* or a short-lived, unobserved, higher energy triplet generated directly from (1)BPyO*. (3)BPyO* is reduced by Fe(2+) and by ABTS(2-) to the radical anion BPyO˙(-) which exhibits a maximum at 510 nm, ε = 2200 M(-1) cm(-1). The anion engages in back electron transfer with ABTS˙(-) with k = 1.7 × 10(9) M(-1) s(-1). The same species can be generated by reducing ground state BPyO with ˙C(CH3)2OH. The photochemistry of BPyO in acetonitrile is similar to that in aqueous solutions.

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“…For example, proflavine exhibits excited-state proton-transfer properties when it is encapsulated in a silane-modified MCM-41 silicate host, as well as in amine-functionalized MCM-41 [ 17 , 18 ]. Proflavine can also access triplet excited-states [ 19 ] and be used as a photosensitizer in sensitization experiments [ 20 ], or generate free radicals to participate in the photoreaction [ 6 ] after excitation. Moreover, it has been used as a photocatalyst to promote the reduction of aldehyde hydrides induced by visible light [ 19 ].…”

Section: Introductionmentioning

confidence: 99%

Excited-State Dynamics of Proflavine after Intercalation into DNA Duplex

et al. 2022

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Proflavine is an acridine derivative which was discovered as one of the earliest antibacterial agents, and it has been proven to have potential application to fields such as chemotherapy, photobiology and solar-energy conversion. In particular, it is well known that proflavine can bind to DNA with different modes, and this may open addition photochemical-reaction channels in DNA. Herein, the excited-state dynamics of proflavine after intercalation into DNA duplex is studied using femtosecond time-resolved spectroscopy, and compared with that in solution. It is demonstrated that both fluorescence and the triplet excited-state generation of proflavine were quenched after intercalation into DNA, due to ultrafast non-radiative channels. A static-quenching mechanism was identified for the proflavine-DNA complex, in line with the spectroscopy data, and the excited-state deactivation mechanism was proposed.

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Triplet-sensitized deoxygenation reaction of 6-cyanophenanthridine 5-oxide in ethanol

Cited by 5 publications

References 19 publications

Covalently Linked Acceptor−Donor Systems Based on Isoquinoline N-oxide Acceptor: Photoinduced Electron Transfer Produces Dual-Channel Luminescent Systems that Evolve Chemically to Photohydroxylation of the Aromatic Donor

Covalently Linked Acceptor−Donor Systems Based on Isoquinoline N-oxide Acceptor: Photoinduced Electron Transfer Produces Dual-Channel Luminescent Systems that Evolve Chemically to Photohydroxylation of the Aromatic Donor

Generation of free oxygen atoms O(³P) in solution by photolysis of 4-benzoylpyridine N-oxide

Excited-State Dynamics of Proflavine after Intercalation into DNA Duplex

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Triplet-sensitized deoxygenation reaction of 6-cyanophenanthridine 5-oxide in ethanol

Cited by 5 publications

References 19 publications

Covalently Linked Acceptor−Donor Systems Based on Isoquinoline N-oxide Acceptor: Photoinduced Electron Transfer Produces Dual-Channel Luminescent Systems that Evolve Chemically to Photohydroxylation of the Aromatic Donor

Covalently Linked Acceptor−Donor Systems Based on Isoquinoline N-oxide Acceptor: Photoinduced Electron Transfer Produces Dual-Channel Luminescent Systems that Evolve Chemically to Photohydroxylation of the Aromatic Donor

Generation of free oxygen atoms O(3P) in solution by photolysis of 4-benzoylpyridine N-oxide

Excited-State Dynamics of Proflavine after Intercalation into DNA Duplex

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Generation of free oxygen atoms O(³P) in solution by photolysis of 4-benzoylpyridine N-oxide