Photochemical rearrangement of diene endoperoxides

1970 ◽  
Vol 48 (20) ◽  
pp. 3265-3268 ◽  
Author(s):  
K. K. Maheshwari ◽  
P. de Mayo ◽  
D. Wiegand
Keyword(s):  
Energy Transfer ◽  
Methyl Ester ◽  
Acid Methyl Ester ◽  
Thermal Rearrangement ◽  
Triplet Energy ◽  
Photochemical Rearrangement ◽  
Acid Methyl ◽  
Levopimaric Acid ◽  
Direct Irradiation ◽  
Triplet Energy Transfer

It has been shown that the direct irradiation of cyclic peroxides such as ascaridole, and those derived from cyclohexadiene, 1,3,5,5-tetramethylcyclohexadiene, and levopimaric acid methyl ester rearrange on irradiation. The bisepoxides are obtained, as in the thermal rearrangement, together with, where the structure permits, the ketoepoxide. The reaction can be induced by triplet–triplet energy transfer.

Triplet state of orotic acid and orotic acid methyl ester in solution

1970 ◽  
Vol 48 (6) ◽  
pp. 987-999 ◽  
Author(s):  
R. W. Yip ◽  
W. D. Riddell ◽  
A. G. Szabo
Keyword(s):  
Methyl Ester ◽  
Excited States ◽  
Orotic Acid ◽  
Flash Photolysis ◽  
Acid Methyl Ester ◽  
Kcal Mole ◽  
Triplet Energy ◽  
Acid Methyl ◽  
Triplet Excited States ◽  
Triplet Energy Transfer

Flash photolysis of orotic acid and orotic acid methyl ester in aqueous solution was studied. The transients were identified as triplet excited states on the basis of their lifetimes, sensitization, quenching, and self-quenching experiments. The rate constants for self-quenching and for decay of the triplet were measured and discussed in terms of dimerization and competing unimolecular and pseudo-unimolecular processes. A triplet energy of 60 kcal mole−1 was deduced for both orotic acid and orotic acid methyl ester from triplet energy transfer measurements.

Thymine Dimerization Induced by Oxidative DNA Lesions and Epigenetic Intermediates via Triplet-Triplet Energy Transfer

2020 ◽  
Author(s):  
Mauricio Lineros-Rosa ◽  
Antonio Francés-Monerris ◽  
Antonio Monari ◽  
Miguel Angél Miranda ◽  
Virginie Lhiaubet-Vallet
Keyword(s):  
Energy Transfer ◽  
Excitation Energy ◽  
Transient Absorption ◽  
Theoretical Calculations ◽  
Dna Lesions ◽  
Transient Absorption Spectroscopy ◽  
Triplet Energy ◽  
Pyrimidine Dimers ◽  
Triplet Energy Transfer ◽  
Dna Nucleobases

Interaction of nucleic acids with light is a scientific question of paramount relevance not only in the understanding of life functioning and evolution, but also in the insurgence of diseases such as malignant skin cancer and in the development of biomarkers and novel light-assisted therapeutic tools. This work shows that the UVA portion of sunlight, not absorbed by canonical DNA nucleobases, can be absorbed by 5-formyluracil (ForU) and 5-formylcytosine (ForC), two ubiquitous oxidative lesions and epigenetic intermediates present in living beings in natural conditions. We measure the strong propensity of these molecules to populate triplet excited states able to transfer the excitation energy to thymine-thymine dyads, inducing the formation of the highly toxic and mutagenic cyclobutane pyrimidine dimers (CPDs). By using steady-state and transient absorption spectroscopy, NMR, HPLC, and theoretical calculations, we quantify the differences in the triplet-triplet energy transfer mediated by ForU and ForC, revealing that the former is much more efficient in delivering the excitation energy and producing the CPD photoproduct. Although significantly slower than ForU, ForC is also able to harm DNA nucleobases and therefore this process has to be taken into account as a viable photosensitization mechanism. The present findings evidence a rich photochemistry crucial to understand DNA photodamage and of potential use in the development of biomarkers and non-conventional photodynamic therapy agents.

Evaluation of the Impact of Fatty Acid Methyl Ester (FAME) Contamination on the Thermal Stability of Jet A

2013 ◽  
Author(s):  
Jr Morris ◽  
Shardo Robert W. ◽  
Higgins James ◽  
Cook Kim ◽  
Tanner Rhonda ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Fatty Acid ◽  
Methyl Ester ◽  
Fatty Acid Methyl Ester ◽  
Acid Methyl Ester ◽  
Acid Methyl ◽  
The Impact ◽  
Thermal Stability Of

Optical Absorption Enhancement in Polymer BHJ thin Film Using Ag Nanostructures: A Simulation Study

2020 ◽  
Vol 16 (4) ◽  
pp. 556-567
Author(s):  
Asma Khalil ◽  
Zubair Ahmad ◽  
Farid Touati ◽  
Mohamed Masmoudi
Keyword(s):  
Absorption Spectrum ◽  
Solar Cell ◽  
Methyl Ester ◽  
Butyric Acid ◽  
Organic Solar Cell ◽  
Short Circuit ◽  
Acid Methyl Ester ◽  
Short Circuit Current ◽  
Acid Methyl ◽  
Butyric Acid Methyl Ester

Background: The photo-absorption and light trapping through the different layers of the organic solar cell structures are a growing concern now-a-days as it affects dramatically the overall efficiency of the cells. In fact, selecting the right material combination is a key factor in increasing the efficiency in the layers. In addition to good absorption properties, insertion of nanostructures has been proved in recent researches to affect significantly the light trapping inside the organic solar cell. All these factors are determined to expand the absorption spectrum and tailor it to a wider spectrum. Objective: The purpose of this investigation is to explore the consequence of the incorporation of the Ag nanostructures, with different sizes and structures, on the photo absorption of the organic BHJ thin films. Methods: Through a three-dimensional Maxwell solver software, Lumerical FDTD, a simulation and comparison of the optical absorption of the three famous organic materials blends poly(3- hexylthiophene): phenyl C71 butyric acid methyl ester (P3HT:PCBM), poly[N-9″-heptadecanyl-2,7- carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)]: phenyl C71 butyric acid methyl ester (PCDTBT:PCBM) and poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b′]dithiophene)-alt- 4,7-(2,1,3-benzothiadiazole)]: phenyl C71 butyric acid methyl ester (PCDPDTBT:PCBM) has been conducted. Furthermore, FDTD simulation study of the incorporation of nanoparticles structures with different sizes, in different locations and concentrations through a bulk heterojunction organic solar cell structure has also been performed. Results: It has been demonstrated that embedding nanostructures in different locations of the cell, specifically in the active layer and the hole transporting layer had a considerable effect of widening the absorption spectrum and increasing the short circuit current. The effect of incorporation the nanostructures in the active layer has been proved to be greater than in the HTL. Furthermore, the comparison results showed that, PCDTBT:PCBM is no more advantageous over P3HT:PCBM and PCPDTBT:PCBM, and P3HT:PCBM took the lead and showed better performance in terms of absorption spectrum and short circuit current value. Conclusion: This work revealed the significant effect of size, location and concentration of the Ag nanostructures while incorporated in the organic solar cell. In fact, embedding nanostructures in the solar cell widen the absorption spectrum and increases the short circuit current, this result has been proven to be significant only when the nanostructures are inserted in the active layer following specific dimensions and structures.

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