2896-70-0Relevant articles and documents
Effect of Sterical Shielding on the Redox Properties of Imidazoline and Imidazolidine Nitroxides
Kirilyuk, Igor A.,Bobko, Andrey A.,Semenov, Sergey V.,Komarov, Denis A.,Irtegova, Irina G.,Grigorev, Igor A.,Bagryanskaya, Elena
, p. 9118 - 9125 (2015)
The oxidant properties of the series of 2,2,5,5-tetraalkyl imidazoline and imidazolidine nitroxides were investigated. An increase in the number of bulky alkyl substituents leads to a decrease in the rate of reduction with ascorbate, which makes the electrochemical reduction potential more negative and shifts the equilibrium in the mixture of nitroxide and reference hydroxylamine (3-carboxy-1-hydroxy-2,2,5,5-tetramethylpyrrolidine-1-oxyl-1-15N) toward the starting compounds. The effect of structural factors on these reactions was analyzed by means of multiple regression using the Fujita steric constant Es and the inductive Hammett constant σI. Satisfactory statistical outputs were obtained in all of the biparameter correlations, denoting that the oxidant properties of the nitroxides are determined by steric and electronic effects of the substituents. The data imply that bulky substituents can stabilize nitroxide and/or destabilize hydroxylamine.
Cella et al.
, p. 943 (1974)
Kinetic analysis of nitroxide radical formation under oxygenated photolysis: Toward quantitative singlet oxygen topology
Zigler, David F.,Ding, Eva Chuheng,Jarocha, Lauren E.,Khatmullin, Renat R.,Dipasquale, Vanessa M.,Sykes, R. Brendan,Tarasov, Valery F.,Forbes, Malcolm D. E.
, p. 1804 - 1811 (2014)
Reaction kinetics for two sterically hindered secondary amines with singlet oxygen have been studied in detail. A water soluble porphyrin sensitizer, 5,10,15,20-tetrakis-(4-sulfunatophenyl)-21,23H-porphyrin (TPPS), was irradiated in oxygenated aqueous solutions containing either 2,2,6,6-tetramethylpiperidin-4-one (TMPD) or 4-[N,N,N-trimethyl-ammonium]-2,2,6,6-tetramethylpiperidinyl chloride (N-TMPCl). The resulting sensitization reaction produced singlet oxygen in high yield, ultimately leading to the formation of the corresponding nitroxide free radicals (R2NO) which were detected using steady-state electron paramagnetic resonance (EPR) spectroscopy. Careful actinometry and EPR calibration curves, coupled with a detailed kinetic analysis, led to a simple and compact expression relating the nitroxide quantum yield ΦR2NO (from the doubly-integrated EPR signal intensity) to the initial amine concentration [R2NH]i. With all other parameters held constant, a plot of ΦR2NOvs. [R2NH]i gave a straight line with a slope proportional to the rate constant for nitroxide formation, kR2NO. This establishment of a rigorous quantitative relationship between the EPR signal and the rate constant provides a mechanism for quantifying singlet oxygen production as a function of its topology in heterogeneous media. Implications for in vivo assessment of singlet oxygen topology are briefly discussed. This journal is
Oxidation of 4-substituted TEMPO derivatives reveals modifications at the 1- and 4-positions
Marshall, David L.,Christian, Meganne L.,Gryn'ova, Ganna,Coote, Michelle L.,Barker, Philip J.,Blanksby, Stephen J.
, p. 4936 - 4947 (2011)
Potenital pathways for the deactivation of hindered amine light stabilisers (HALS) have been investigated by observing reactions of model compounds - based on 4-substituted derivatives of 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) - with hydroxyl radicals. In these reactions, dilute aqueous suspensions of photocatalytic nanoparticulate titanium dioxide were irradiated with UV light in the presence of water-soluble TEMPO derivatives. Electron spin resonance (ESR) and electrospray ionisation mass-spectrometry (ESI-MS) data were acquired to provide complementary structural elucidation of the odd- and even-electron products of these reactions and both techniques show evidence for the formation of 4-oxo-TEMPO (TEMPONE). TEMPONE formation from the 4-substituted TEMPO compounds is proposed to be initiated by hydrogen abstraction at the 4-position by hydroxyl radical. High-level ab initio calculations reveal a thermodynamic preference for abstraction of this hydrogen but computed activation barriers indicate that, although viable, it is less favoured than hydrogen abstraction from elsewhere on the TEMPO scaffold. If a radical is formed at the 4-position however, calculations elucidate two reaction pathways leading to TEMPONE following combination with either a second hydroxyl radical or dioxygen. An alternate mechanism for conversion of TEMPOL to TEMPONE via an alkoxyl radical intermediate is also considered and found to be competitive with the other pathways. ESI-MS analysis also shows an increased abundance of analogous 4-substituted piperidines during the course of irradiation, suggesting competitive modification at the 1-position to produce a secondary amine. This modification is confirmed by characteristic fragmentation patterns of the ionised piperidines obtained by tandem mass spectrometry. The conclusions describe how reaction at the 4-position could be responsible for the gradual depletion of HALS in pigmented surface coatings and secondly, that modification at nitrogen to form the corresponding secondary amine species may play a greater role in the stabilisation mechanisms of HALS than previously considered. The Royal Society of Chemistry 2011.
Waste-derived bioorganic substances for light-induced generation of reactive oxygenated species
Bianco Prevot, Alessandra,Avetta, Paola,Fabbri, Debora,Laurenti, Enzo,Marchis, Tatiana,Perrone, Daniele G.,Montoneri, Enzo,Boffa, Vittorio
, p. 85 - 90 (2011)
Urban waste-derived bioorganic substances (UW-BOS) have shown promise as chemical auxiliaries for a number of technological applications in the chemical industry and in environmental remediation. In this study, the application of these substances in the photodegradation of organic pollutants is addressed. The experimental work is specifically focused on the photolysis mechanism promoted by AC8, a UW-BOS isolated from a 2:1 w/w mixture of food and green residues, composted for 110 days, using 4-chlorophenol (4-CP) as probe molecule. The production of OH and the 1O2 is monitored by EPR spectroscopy. The correlation between radical species evolution and photodegradation of 4-CP is investigated. The effect of 1O 2 and OH scavengers on the 4-CP degradation process is also checked. The results suggest that the role of these species in the photodegradation of 4-CP depends on AC8 concentration. AC8 is thereby proven to be a photosensitizer for applications in environmental remediation. The results on AC8 further support the use of urban bio-waste as a versatile source of chemical auxiliaries of biological origin for use in diversified applications. An offer you can't refuse: A bioorganic substance isolated from a composted urban refuse (AC8) is applied as sensitizer in the photodegradation of 4-chlorophenol. Production of OH and 1O2 species is monitored by EPR spectroscopy and the data suggest that the role played by these species in the photodegradation process is strictly related to AC8 concentration. AC8 is thereby proven to be a photosensitizer for applications in environmental remediation.
Bordeaux,Lajzerowicz
, p. 790,791,792 (1974)
Singlet oxygen generation properties of an inclusion complex of cyclic free-base porphyrin dimer and fullerene C60
Ooyama, Yousuke,Enoki, Toshiaki,Ohshita, Joji,Kamimura, Takuya,Ozako, Shuwa,Koide, Taro,Tani, Fumito
, p. 18690 - 18695 (2017)
To gain insight into the singlet oxygen (1O2) generation properties of supramolecular complexes of cyclic free-base porphyrin dimer with fullerene C60, we evaluated the 1O2 quantum yield (ΦΔ) and rate constant (Kobs) of 1O2 generation for a cyclic free-base porphyrin dimer (CPD) linked by butadiyne bearing four 4-pyridyl groups and its inclusion complex (C60?CPD) with C60. We demonstrate that CPD and C60?CPD possess the ability to generate 1O2 under visible light irradiation. Moreover, it was found that the ΦΔ value of C60?CPD is lower than that of CPD. Based on the kinetic and thermodynamic consideration concerning the electron transfer processes between the porphyrin dimer and C60, this work revealed that the lower ΦΔ value of the C60 inclusion complex would be attributed to the formation of the charge-separated state c60·?-CPD·+, leading to a low intersystem crossing (ISC) efficiency for the formation of the triplet excited state 3(CPD)*.
Spin-labeled naphthalimide oxygen-containing compound and application thereof
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Paragraph 0030-0031, (2021/06/09)
The invention belongs to the technical field of medical drugs, and relates to a spin-labeled naphthalimide compound containing an oxygen substituent and an application thereof, in particular to a stable nitroxide free radical labeled naphthalimide compound containing an oxygen substituent and an application thereof in preparation of anti-tumor drugs. According to the spin-labeled naphthalimide oxygen-containing compound and the application thereof, a stable nitroxide free radical is introduced into an oxygen-containing substituent naphthalimide parent to obtain the naphthalimide compound shown in the general formula I and pharmaceutically acceptable salt thereof, and the compound has good anti-tumor activity, shows lower toxicity to normal cells than a naphthalimide analogue containing a nitrogen substituent, and has very good development and application prospects.
A class of stable nitroxide free radical modified naphthalimide compounds, and application thereof
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Paragraph 0066-0067, (2020/07/02)
The invention belongs to the technical field of medicines, and relates to a class of naphthalimide compounds modified by stable nitroxide free radicals, and application thereof, particularly to a class of naphthalimide compounds with stable nitroxide free radicals, and application of the naphthalimide compounds in preparation of antitumor medicines. According to the invention, stable nitroxide free radicals are introduced into a naphthalimide parent structure to obtain a naphthalimide compound represented by a general formula I or II, and a pharmaceutically acceptable salt, a solvate and a hydrate thereof, wherein R1, R2, R3 and R4 are defined in the claims and the specification.
