Excited states of ketones as electron donors—ketone—iodonium salt systems as photoinitiators for radical polymerization

Timpe, H.‐J.; Kronfeld, K.‐P.; Lammel, U.; Fouassier, Jean Pierre; Lougnot, Daniel Joseph

doi:10.1016/1010-6030(90)87096-t

Cited by 65 publications

(33 citation statements)

References 23 publications

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“…Because k dif and [base] can be taken as constants, the collision frequency varies depending on È isc 3 s 0 t . The values of È isc and s 0 t of XAN analogues were previously reported (54). The values of È 8-oxo-dGuo and È P were divided by È isc 3 s 0 t and plotted against ÁE ( Fig.…”

Section: Discussionmentioning

confidence: 85%

Base Oxidation at 5′ Site of GG Sequence in Double-stranded DNA Induced by UVA in the Presence of Xanthone Analogues: Relationship Between the DNA-damaging Abilities of Photosensitizers and Their HOMO Energies¶

Hirakawa

Yoshida

Oikawa

et al. 2003

Photochem Photobiol

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UVA contributes to skin cancer by solar UV light. Photosensitizers are believed to play an important role in UVA carcinogenesis. We investigated the mechanism of DNA damage induced by photoexcited xanthone (XAN) analogues (XAN, thioxanthone [TXAN] and acridone [ACR]), exogenous photosensitizers, and the relationship between the DNA-damaging abilities and their highest occupied molecular orbital (HOMO) energies. DNA damage by these photosensitizers was examined using 32P-labeled DNA fragments obtained from the p53 tumor suppressor gene. Photoexcited XAN caused DNA cleavage specifically at 5'-G of the GG sequence in the double-stranded DNA only when the DNA fragments were treated with piperidine, suggesting that DNA cleavage is due to base modification with little or no strand breakage. With denatured single-stranded DNA, the extent of XAN-sensitized photodamage was decreased. An oxidative product of G, 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dGuo), was formed by photoexcited XAN, and the 8-oxo-dGuo formation was decreased in single-stranded DNA. TXAN and ACR induced DNA photodamage as did XAN, although the order of DNA-damaging ability was XAN > TXAN > ACR. These findings suggest that photoexcited XAN analogues induce nucleobase oxidation at 5'-G of GG sequence in double-stranded DNA through electron transfer. The HOMO energies of these photosensitizers, estimated from ab initio molecular orbital (MO) calculation, decreased in the following order: XAN > TXAN > ACR. Extents of DNA damage increased exponentially with the HOMO energies of XAN analogues. This study suggests that DNA-damaging abilities of photosensitizers can be estimated from their HOMO energies.

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Section: Discussionmentioning

confidence: 85%

Base Oxidation at 5′ Site of GG Sequence in Double-stranded DNA Induced by UVA in the Presence of Xanthone Analogues: Relationship Between the DNA-damaging Abilities of Photosensitizers and Their HOMO Energies¶

Hirakawa

Yoshida

Oikawa

et al. 2003

Photochem Photobiol

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“…Using the triplet energy reported by Timpe et al . , triplet oxidation of purines is endoergic and using the oxidation potential of MK reported by Jockusch et al . , reduction of the pyrimidine bases by either singlet or triplet MK is likewise endoergic.…”

Section: Resultsmentioning

confidence: 93%

“…Using the singlet energy (3.45 eV in a rigid glass) and ground state reduction potential (À1.87 V vs SCE) reported by Loutfy for MK provides an excited state oxidation potential (1.58 V vs SCE) sufficiently large to oxidize G, but questionable for A (E ox = 1.24 and 1.69 V, respectively) (15,26). Using the triplet energy reported by Timpe et al (14), triplet oxidation of purines is endoergic and using the oxidation potential of MK reported by Jockusch et al (13), reduction of the pyrimidine bases by either singlet or triplet MK is likewise endoergic. Our hopes that the triplet state of the MK hairpins might prove to be an effective reductant of pyrimidines unfortunately were not realized.…”

Section: Spectroscopic Characterization Of Hairpins Mk-1-3mentioning

confidence: 99%

Electronic Interactions of Michler's Ketone with DNA Bases in Synthetic Hairpins

Jalilov

Young

Eaton³

et al. 2014

Photochem & Photobiology

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The mechanism and dynamics of photoinduced electron transfer in two families of DNA hairpins possessing Michler's ketone linkers have been investigated by means of steady state and time-resolved transient absorption and emission spectroscopies. The excited state behavior of the diol linker employed in hairpin synthesis is similar to that of Michler's ketone in methanol solution. Hairpins possessing only a Michler's ketone linker undergo fast singlet state charge separation and charge recombination with an adjacent purine base, attributed to well-stacked ground state conformations, and intersystem crossing to the triplet state, attributed to poorly stacked ground state conformations. The failure of the triplet to undergo electron transfer reactions on the 7 ns time scale of our measurements is attributed to the low triplet energy and reduction potential of the twisted triplet state. Hairpins possessing both a Michler's ketone linker and a perylenediimide base surrogate separated by four base pairs undergo photoinduced hole transport from the diimide to Michler's ketone upon excitation of the diimide. The efficiency of hole transport is dependent upon the sequence of the intervening purine bases.

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“…Whether this assumption is valid can be assessed via a colorimetric acid/base titration during 395 nm LED irradiation using QR as an acid marker. This result may be explained by the synergistic effect of an acceptable light harvesting capability, low deactivation behavior in acetonitrile (f f = 0.005), 33 high quantum yield of triplet formation (f T ) (0.66) 33 and an efficient interaction rate constant between 3 PS-I and the diphenyliodonium salt of 410 9 s À1 . 20 As seen in Fig.…”

Section: View Article Onlinementioning

confidence: 99%

Activation of the sol–gel process by visible light-emitting diodes (LEDs) for the synthesis of inorganic films

et al. 2015

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Photoinduced sol-gel polymerization is an efficient one-step and solvent-free process to synthesize inorganic or hybrid films. Highly condensed films are achieved using photoacid generators (PAGs) producing in situ Brönsted superacids without thermal densification. However, most commercial PAGs exhibit short light absorption below 300 nm and display limited overlapping with the emission spectra of conventional UV sources, or with the newly emerging visible LED light sources. Therefore, the development of PAGs with extended absorption in UVA (l 4 380 nm) is of paramount importance. In this study, a simple one-step visible LED induced sol-gel process of poly(dimethoxysiloxane) (PDMOS) was conducted by virtue of different photosensitized acid generating systems. The sol-gel process was followed using real-time Fourier transform infrared (RT-FTIR) spectroscopy. The hydrolysis rate and condensation of the siloxane network were directly correlated with the concentration of the photogenerated acid. Different types of photosensitizers, onium cations and counter anions were investigated. Isopropylthioxanthone combined with iodonium salts bearing high charge delocalized anions led to the fastest and more efficient release of protonic acid, yielding tack-free and condensed transparent silica films. 29 81535026; Tel: +86 29 81535032 † Electronic supplementary information (ESI) available: The UV-vis spectra of all the PSs and the emission spectrum of 395 nm LED, deconvolution of the Si-O-Si stretching band of cured PDMOS films photocatalyzed by PS/Iod-PF 6 , evolution of n as (Si-O-Si) vibrational frequencies, UV spectra changes of PS-I/Iod-PF 6 upon irradiation of 395 nm LED under air in acetonitrile. See

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Excited states of ketones as electron donors—ketone—iodonium salt systems as photoinitiators for radical polymerization

Cited by 65 publications

References 23 publications

Base Oxidation at 5′ Site of GG Sequence in Double-stranded DNA Induced by UVA in the Presence of Xanthone Analogues: Relationship Between the DNA-damaging Abilities of Photosensitizers and Their HOMO Energies¶

Base Oxidation at 5′ Site of GG Sequence in Double-stranded DNA Induced by UVA in the Presence of Xanthone Analogues: Relationship Between the DNA-damaging Abilities of Photosensitizers and Their HOMO Energies¶

Electronic Interactions of Michler's Ketone with DNA Bases in Synthetic Hairpins

Activation of the sol–gel process by visible light-emitting diodes (LEDs) for the synthesis of inorganic films

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